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Portsmouth or SCHRS ???

Posted By: Mark Schneider

Portsmouth or SCHRS ??? - 01/28/18 08:37 PM

Tiberious wrote

Quote
CRAM will be very interested to know about the Portsmouth or SCHRS debate. We have an ongoing discussion on if we should move away from Portsmouth.

We're flattered to hear you call Cat Fight a cant miss event. We hope it will grow.

Marketing Officer for the Catamaran Racing Association of Michigan
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 01/28/18 08:39 PM


TiberiusGV

A bit of history that your club CRAM and mine CRAC experienced back in the day. Our clubs used the NAMSA catamaran rating system administered by Herb Malm. US Sailing took over the Dixie portsmouth system and with Darline Hobock taking the volunteer lead made a commitment to support the multihull racing scene. Both clubs vigorously debated a move from NAMSA to US Sailing Portsmouth. I have a vague memory of speaking with Roger Cochran at the time. The core principals remain the same and are:
Accuracy
Transparency
Authority
Robustness

Accuracy How close are the ratings to the true rating of the class.
Transparency Do the rank and file racers KNOW what data and methods are used to generate changes in the ratings and do they think this process is fair.
Authority The yacht clubs and catamaran clubs want to know that they have the support and approval of regional and national bodies that can settle all disputes.
Robustness. Can the ratings quickly get to a fair rating for all of the boats that want to go racing. Recalculating last seasons results using the New... better more accurate ratings (not saying I did this....errrr ahem...) is just nuts.

Concurrently, the kind donation of the Hoyt Jolley endowment to support a multihull championship within US Sailing Adult Championship programs was a powerful incentive for most clubs to switch from NAMSA to US Sailing Portsmouth. The idea was that sailors would use one handicap system to go racing. The Authority of US Sailing was a big factor in CRAC's decision to change to USPN.

The Robustness of the Dixie portsmouth system was limited because it is founded on the premise that fleets of one design class boats are being rated. Catsailors of course are constantly trying out modifications to their one design class. This presents a unique challenge to rating systems that presume a fleet of boats. One offs, or changes in rigs, sail areas, boards, etc etc etc are, by definition, not a fleet of boats. The solution of course was to modify the Dixie portsmouth system that was founded on statistical data collection of class data by creating a table of flat percentage modifications. Presto... the statistical system was now robust!

In 2018, the criteria are the same.. Accuracy, Transparency, Authority and Robustness.

Analysis of the SCHRS 2017 measurement rating table was compared to race results from the French racing scene for these classes.


Summary chart for C1 AHPC Viper Double Nacra 20 carbone F18 A Class classic Nacra 17 old Olympic

The SCHRS annual review states. (I can get permission to forward you a copy if you need)

2.4 All these differences are below 2% and most are as expected. There is nothing here to compel us to make any changes to the formula.
Summary SCHRS is accurate

SCHRS is transparent. Its a measurement rule and ALL of the class OD measurements are published as is the formula used to calculate the ratings. The web site has the data and calculators. Measurement is provided by World Sailing certified individuals.

SCHRS has the authority of World Sailing and US Sailing will be including SCHRS information in the handicap systems that US Sailing supports. (All handicap sailing administration has been moved under the off shore committee.)

SCHRS is Robust. A modification to a one design class is measured and the rating for the specific boat is calculated. A one off design can be measured and a final rating for that boat determined. For the owner.... his rating is by definition "accurate" and independently determined and reproducible since approved measure's use the same techniques. For the fleet, The modified boat is rated using the same methods used for their rating.


Final point, the UK RYA portsmouth system is a statistical system as well but fundamentally different in design then the US system. The UK system rates 10 catamaran classes because those are the active UK fleets that can generate yearly returns. They use a hybrid system for anyone with a boat in the dead boat society.

Will Rottering (Houston Area) is the US representative replacing me going forward. I and another volunteer serve on his US committee.

We would be delighted to answer any questions you have and World Sailing has been extremely responsive in getting final answers to any concerns we have raised.
Mark

Last edited by Mark Schneider; 01/26/18 03:49 AM.
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 01/28/18 08:42 PM

Tiberius worte
Quote

WOW I really appreciate all of this information. I will be forwarding this on to Roger Cochran who as you may be able to guess, the CRAM Scoring Officer.

Marketing Officer for the Catamaran Racing Association of Michigan
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 01/28/18 08:47 PM

Mike Fahle Wrote
Quote
Hi Mark,

OCRA used to do a lot of racing using Portsmouth for any boat that showed up (we encouraged that); popular class boats, some "one-offs", any modification that a racer wanted to try, and many "dead" class or rarely raced class boats. Over the years we found it to be very even and predictive - the sailors seemed to finish pretty much in the same positions regardless of the boats they raced; the classes seemed to finish in an expected pattern to each other, etc.

It worked so well that way that one time when we went racing in CRAM we saw results that were posted that we knew could not be correct because that predictability was wrong - one whole class beat all of the next class that started, for example, and (very long story, short) it turned out that there had been a five minute scoring error in favor of the unusually well performing class.

I always thought that a measurement class could be even more accurate since I have always also raced big boats that use measurement handicap systems (both keel and multihulls) and that is the way the moneyed racers have gone (good old PHRF is still alive and well here in MI and OH). I have no experience with that on the beach cat level and wonder if they use race result feedback to check their accuracy as Portsmouth did.

Mike
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 01/29/18 02:47 AM

HI Mike

Two points SCHRS World committee does an end of the year analysis comparing the gaps in time between the Formula prediction and actual race results. They publish this analysis. For 2017 they report that the gaps or deltas are 2 percent or less for 5 major classes using large events in France for the race data.

Of course a strong one design fleet will see 20 to 40 percent deltas between first and last place finishers sailing identical boats in class... even at the Olympic level! The SCHRS formula is remarkably accurate and no changes to the formula were called for in 2018.

To put this into perspective... consider a theoretical race. with 10 30 footers all sailed equally well. At the weather mark 9 boats will becoming in on starboard and will have to randomly line up bow to stern on the lay line.... The boat on port tack will get to the weather mark exactly the same time as the first boat on Starboard... However, the RRS of sailing will force port to duck the entire parade of boats and round the weather mark in 10th PLACE... On time... they will be 270 feet behind... or around 6 percent behind on time pending their speed over the ground... Even tho they sailed a perfect race. So... what this means is that the RRS will introduce as much as 6 percent error when you try to measure its performance around the race track. SCHRS has developed an accurate measurement formula for beach cats.

Second point, you write
"the sailors seemed to finish pretty much in the same positions regardless of the boats they raced;"

I agree, the pecking order in a fleet is really a good measure of sailing skill and as you noted.... a very good quick check on the validity of any set of calculated race results. We know the top sailors and we salute anyone who sails really well that day and breaks up the ol pecking order...

IMO, what we want is a handicap game that has Accuracy, Transparency, Authority and Robustness. We can go CRAZY about the last significant number in your rating... Forgetting that the RRS introduce noise... We really should value the other three attributes equally.... Having a rating system that is transparent eliminates a lot of the backbiting that undermines a sailors good performance.. Having an Authority outside of the local region also goes a long way in building support for a system. Darline Hobock, was a singular personality who generated national support for her volunteer efforts in administering US Portsmouth for us. SCHRS builds this authority in by its multinational contributors and international support. Of course Robustness ... ie can it handle Mike Fahles custom and home built sail for his mystere 4.3 (I think that was the last sail I remember you working on) is unique to us in the multihull world..... those dinghy sailors tend not to fiddle with their boats in the same way we do....

Take Care
Mark

Now... what happens when Steve Clark's UFO wants to come racing is a new problem... so... hmmm....
Posted By: Damon Linkous

Re: What the heck is this? - 01/30/18 06:00 PM

Good discussion! My first exposure to SCHRS came with involvement in the Florida 300. I'm impressed with the math and analysis they use to arrive at the ratings.

The biggest roadblock I see to using it widely for local regattas in the USA (besides inertia - "we've always done it this way") is the nature of the bulk of racers at popular regattas (casual and have customized their boat in some way).

The way we do it for the Florida 300 is to use the ratings from the SHCRS ratings table http://www.schrs.com/ratings.php for a boat IF

The skipper can certify that their boat is a factory stock version of the rated boat, otherwise they need to get an individual SCHRS certificate.

If someone shows up to race with a slightly modified boat and no SCHRS certificate then the PRO will assign a rating.
Posted By: Mark Schneider

Re: What the heck is this? - 02/01/18 05:08 AM

Originally Posted by Damon Linkous


If someone shows up to race with a slightly modified boat and no SCHRS certificate then the PRO will assign a rating.


A ha.. the rest of the world calls this process PHRF! (just putting the conventional name to what you do)

Chances are your Race Committee PRO can do a pretty good job of guessing a fair rating.... The sailor can enter the race or not with that rating. The bar could host a lively discussion on ratings or the slimy reputation of XXX or whatever)

How good of a job the PRO does as a ratings expert/ sooth sayer is really not the point....PHRFng the rating is not a good or bad thing...Much of the sailing world in the USA uses PHRF quite happily. its simply just not a transparent or unbiased process.

The advantage that SCHRS provides is that for the NEXT EVENT.... the Owner can go get his gear measured, present the certificate with his transparent rating and play the game with a fully measured boat. Discussion about fair/not fair and bias is simply over. (It doesn't mean everyone is happy with the measured rating... but you know where you stand)
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/01/18 05:12 AM

samc99us; wrote
Quote

I'm a member of both forums. In terms of ease of use, I won't favor one over the other, and I really appreciate Damons efforts to keep this site alive simply for the technical content. However, if it was merged with thebeachcats.com, we would make it work. The one thing I've always appreciated about this site is a lot of the top guys would come here and post advice and ask questions of fellow racers, without reading through some of the more mundane topics. I suspect that is what kept those guys coming back here. The downside is we have a bit of a split in knowledge, with beginners overwhelmed or unaware of this forum, and experienced racers ignoring the other. So it could be good for our community as a whole to merge the two, but we also must respect the White's family wishes in this regard.

Now onto SCHRS...

Mark lays out all he details. I will speak from practice. I have run results in both rating systems with no net difference between them. However, SCHRS offers an equitable rating system when modifications come into play. For example, this let one of our former F16 sailors race his boat in 1 up mode with main and jib and compete fairly. His rating ended up being a touch higher than a Nacra I20; he ended up finishing a touch behind the well sailed I20's on a good night and would often correct in front but equally often not. I won't say he was ecstatic about his number (behind used to the Portsmouth handicap system that just assigns a very simple modifier to your rating, no matter how much sail area you add), but I think it made for fair racing without any additional racing statistics required-statistics that would never come. The bottom line is it allows someone to build a line honors boat and race it fairly in a handicap fleet, or make modifications to their existing class boat and race it fairly under handicap without relying on a one size fits all modifier.

There are several other things SCHRS brings to the table. One is a high amount of global race data,primarily French, but they do take input from European events, Texel, and our U.S SCHRS committee. This mitigates the issue that was happening in Portsmouth whereby the top guns would all be racing I20's, that boats rating would get driven low and once the top guys were out of the class the rating would state low as there wouldn't be enough statistical data to correct it out for what a more average team could do against the other average teams.

Second, this rating system is managed by a French committee, they do it well and alleviate the burden on the U.S catamaran fleets to maintain their own rating system (Portsmouth for cats is almost a decade old).

Third, it is free, completely open source and easy to use.

Fourth, and most importantly, it seriously cut back on rating conversations at the bar.


Last edited by samc99us; 01/29/18 12:06 PM.
F18 Infusion
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/01/18 05:23 AM

Quote
For example, this let one of our former F16 sailors race his boat in 1 up mode with main and jib and compete fairly. His rating ended up being a touch higher than a Nacra I20; he ended up finishing a touch behind the well sailed I20's on a good night and would often correct in front but equally often not.


Sam, Good report on West Rivers SCHRS outcomes.....

IMO, This is always a tough ratings problem/choice. A single handed sailor running a rig with two or three sails will have to be really well trained to sail the boat to that rating.... I don't believe SCHRS (or any other system) cuts you a break for your choice of running two or three sails with just two hands.

IMO, You don't want to run three sails single handed on a very crowded and short windward leeward course! On the other hand.... if you know you are doing a Once around a long windward leeward course plus a reach leg out the river.... .... you have a weapon!
Posted By: ksurfer2

Re: Portsmouth or SCHRS ??? - 02/01/18 01:13 PM

Originally Posted by Damon Linkous
Good discussion! My first exposure to SCHRS came with involvement in the Florida 300. I'm impressed with the math and analysis they use to arrive at the ratings.

The biggest roadblock I see to using it widely for local regattas in the USA (besides inertia - "we've always done it this way") is the nature of the bulk of racers at popular regattas (casual and have customized their boat in some way).

The way we do it for the Florida 300 is to use the ratings from the SHCRS ratings table http://www.schrs.com/ratings.php for a boat IF

The skipper can certify that their boat is a factory stock version of the rated boat, otherwise they need to get an individual SCHRS certificate.

If someone shows up to race with a slightly modified boat and no SCHRS certificate then the PRO will assign a rating.


Like if a highly modified Tornado would show up at the FL300, they would not be allowed to race with a stock Tornado rating, they would need a different rating. Right?
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/01/18 04:08 PM

It depends on the meaning of the word "STOCK" (you are going to hate this answer)

Chances are you define the word "Stock" much like Hobie 16 world.... Basically, if you did not buy it from the factory... its not stock... Oh... and the factory can change things any time they want..... so by definition.... its STOCK.

Maybe, you are a bit more open minded.... you can add a different bugee set up for your trap lines, arguably violating the rule but not the spirit of the rule..... and so it starts.

SCHRS ratings are not going to fuss with how you run your trap lines or what type of running rigging (high tech line) you use. So.... STOCK is a meaningless term for a Hobie 16 rating.

The A class has no concept of stock... They just have a measurement rule box that you must fit in. What is STOCK for an F18? .... do decksweeper rigs count as STOCK? (rhetorical question only)

The T class has had a number of rule sets over the years... The current rule set tried to make it as much like a SMOD one design for ISAF Olympic selection trials after cats were booted. The fleet entered a one design Tornado class in the selection trials..

Would you use the word "STOCK" Tornado to describe the Lovell and Ogletree's Tornado in the China Olympics sporting the only code zero geneker in the fleet going up wind at the start of race 1? By rules at the time.... it was a STOCK Tornado.... QED!.... Of course, what people really meant was.... Was it FAIR.? Bottom line.... ISAF demanded changes in the Rules defining "STOCK" after the Olympics. (The USA Tornado finished dead last... so they shot themselves in their own foot.... so... answer to the ? fair? ... would be Yes it was!@)

My advice would be.... get a judge involved and clearly define the rule set for the race. Make it crystal clear what the standard for measurement compliance will be and put the responsibility on the owners to meet it. NOBODY wins when you half butt this and the OA's lack of rigor opens a door for debate after the fact... That's when you get the BS started that xxx is a cheater boat and everyone just walks away.

so..... maybe you don't want to use the word "Stock" in the rule set!

Fair... is an opinion and likely grounded on where you stand. Not a good word to use in the rule set either.

The other pitfall is using the term "Class legal" without careful thought. Are the numerous Class rules comparable? Is it FAIR for that particular race to run using a Class Rule standard... Hell.... You can't even find a collection of class rules for some classes that might show up..... Why would a fleet of 1 boat in a class need a lot of rules??

Bottom line....think carefully about what you want.
Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/01/18 04:49 PM

And they were given a new rating, at least for 2017, so I'm not really sure where that issue comes from. It is also up to the race organizers to handle this situation in a fair and equitable manner i.e don't allow entries without valid SCHRS numbers. Assigning on the spot ratings without measuring the boats is questionable at best, but then again this race has always had a cowboy feel...
Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/01/18 05:31 PM

Originally Posted by Mark Schneider
It depends on the meaning of the word "STOCK" (you are going to hate this answer)

Chances are you define the word "Stock" much like Hobie 16 world.... Basically, if you did not buy it from the factory... its not stock... Oh... and the factory can change things any time they want..... so by definition.... its STOCK.

Maybe, you are a bit more open minded.... you can add a different bugee set up for your trap lines, arguably violating the rule but not the spirit of the rule..... and so it starts.

SCHRS ratings are not going to fuss with how you run your trap lines or what type of running rigging (high tech line) you use. So.... STOCK is a meaningless term for a Hobie 16 rating.

The A class has no concept of stock... They just have a measurement rule box that you must fit in. What is STOCK for an F18? .... do decksweeper rigs count as STOCK? (rhetorical question only)

The T class has had a number of rule sets over the years... The current rule set tried to make it as much like a SMOD one design for ISAF Olympic selection trials after cats were booted. The fleet entered a one design Tornado class in the selection trials..

Would you use the word "STOCK" Tornado to describe the Lovell and Ogletree's Tornado in the China Olympics sporting the only code zero geneker in the fleet going up wind at the start of race 1? By rules at the time.... it was a STOCK Tornado.... QED!.... Of course, what people really meant was.... Was it FAIR.? Bottom line.... ISAF demanded changes in the Rules defining "STOCK" after the Olympics. (The USA Tornado finished dead last... so they shot themselves in their own foot.... so... answer to the ? fair? ... would be Yes it was!@)

My advice would be.... get a judge involved and clearly define the rule set for the race. Make it crystal clear what the standard for measurement compliance will be and put the responsibility on the owners to meet it. NOBODY wins when you half butt this and the OA's lack of rigor opens a door for debate after the fact... That's when you get the BS started that xxx is a cheater boat and everyone just walks away.

so..... maybe you don't want to use the word "Stock" in the rule set!

Fair... is an opinion and likely grounded on where you stand. Not a good word to use in the rule set either.

The other pitfall is using the term "Class legal" without careful thought. Are the numerous Class rules comparable? Is it FAIR for that particular race to run using a Class Rule standard... Hell.... You can't even find a collection of class rules for some classes that might show up..... Why would a fleet of 1 boat in a class need a lot of rules??

Bottom line....think carefully about what you want.


This is all good advice, but I'm not sure the organizers will take this to heart. If they want the race to continue being successful, and down the road, want the Worrell 1000 to be successful, they need to beef up the rules and actually have an international jury available to take protests. Otherwise you get into all sorts of issues (cough couch Cape Canaveral exclusion zone). The lack of proper management in these areas is a prime reason why I haven't shown up to do the race, among others including wear and tear on a boat that spends a good deal of time buoy racing, plus the usual excuses of time.

Mark I realize your question is rhetorical, but for the rest of the world, the F18 is also a measurement box rule boat...its a much tighter box than the A but things like decksweepers are legal per the rules and at this point are here to stay. Are they faster, well, upwind yes, downwind maybe not. Will the F18 SCHRS rating change as a result? No. Will every one else's SCHRS rating potentially change as a result? Yes, as the benchmark boat is the F18 and if it gets faster then the boats around it have to change, that is simply a result of how the formula works, and it may confuse many sailors.

Then you have classes with ambiguous class rules as mentioned above. SCHRS I think handles that in a good way with a measurement based rule, but it would help if sail areas and mast areas are prescribed by the builders for granting of an initial rating.
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/02/18 12:16 AM

Sam, You highlight the rabbit hole in using the term "Class Legal" in a handicap race under ANY rating rule. It is a proven swamp!

Indeed, Deck sweepers are CLASS legal. They are not really an issue in a F18 race... However, once you start down that road... What's class... What's legal.... you wind up explaining F18s as yardsticks, why other ratings may or may not change, and on and on....

Show up for a handicap race against a deck sweeper F18, a "standard" rig and perhaps a Hobie tiger all called F18s. .... Questions will asked about the ratings used. .... God forbid you try to remember ALL of the flavors of the Nacra 6.0 as an OA for an event.... The class names are a trap.... They are a by product of US Dixie Portsmouth.... which is a rating system premised on FLEETS of sailors racing a Class of boat against ANOTHER fleet of sailors in a different class.

Best practice.... don't get into the class ID swamp..... or worse... the class legal briar patch... I think you simply deliver the message... Know your rating.


Most of the events, you don't need to present official paperwork. If you know that you are sailing a OD class legal Hobie 16.... you can honorably look up the H16 rating and report it. .... Its a number.... NOT a report of a class legal Hobie 16.... Likewise the owner of a Hobie 16 with a solid mast... Or a comp tip hobie 16 with non class legal customization.... just report your number... its the owners responsibility to figure it out or get some help. IF you are single handing your class legal Hobie 16...... KNOW your rating... and report it. Its a number! its the owners responsibility!

The "heavily modified Tornado" owner just needs to measure all the modifications etc and report the rating.... ITS a SINGLE NUMBER.... If asked... he can show his certificate that documents that simple Single number.

BTW.... Know your number! Its how all of the PHRF boats go racing... Hell PHRF scratch sheets may not even LIST the boat class.... they want yacht name, Sail number, captain name and your NUMBER....
QED.... Its the owners responsibility to KNow their Number!
Posted By: Jake

Re: Portsmouth or SCHRS ??? - 02/02/18 02:01 AM

Originally Posted by samc99us

This is all good advice, but I'm not sure the organizers will take this to heart. If they want the race to continue being successful, and down the road, want the Worrell 1000 to be successful, they need to beef up the rules and actually have an international jury available to take protests. Otherwise you get into all sorts of issues (cough couch Cape Canaveral exclusion zone). The lack of proper management in these areas is a prime reason why I haven't shown up to do the race, among others including wear and tear on a boat that spends a good deal of time buoy racing, plus the usual excuses of time.

Mark I realize your question is rhetorical, but for the rest of the world, the F18 is also a measurement box rule boat...its a much tighter box than the A but things like decksweepers are legal per the rules and at this point are here to stay. Are they faster, well, upwind yes, downwind maybe not. Will the F18 SCHRS rating change as a result? No. Will every one else's SCHRS rating potentially change as a result? Yes, as the benchmark boat is the F18 and if it gets faster then the boats around it have to change, that is simply a result of how the formula works, and it may confuse many sailors.

Then you have classes with ambiguous class rules as mentioned above. SCHRS I think handles that in a good way with a measurement based rule, but it would help if sail areas and mast areas are prescribed by the builders for granting of an initial rating.


ding ding ding. I agree. That's not really why I don't do the Florida distance race anymore but it was definitely a sore spot for me, personally. I don't know that it needs to be an international jury, but at least one trained judge and two knowledgeable/fair stand-ins would probably be sufficient. Adhere to the rules with protests, filings, time limits, impartial adjudicating, etc. Sticking to a very strict regiment of what information should be in an NOR, what should be in Sailing Instructions, and what you can/can't change in the skipper meetings each morning will help everyone have an even and consistent expectation of what they signed up for. That said, it's been several years since I've participated so I'm speaking from an aged, and possibly not current, perspective.

And as far as splitting hairs with a handicap rating, I have two points:
A) these little things like deck sweeper mains and small changes here and there have such a small actual effect on boat performance compared to the mental impact. If you are in the 99th percentile of racing, yes, they may give you an edge - but those guys are hardly worried about their handicap rating.
B) it's handicap racing. By it's very nature it's inaccurate. It's a close swing at leveling the playing field and that's all. If you don't accept it as that, you won't ever enjoy it.
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/04/18 04:12 PM


First point... these are two different games we play. Very similar games but you play them slightly differently.

Quote
By it's very nature it's inaccurate.


Nope.... to make that argument... you would have to show that Sailor A who routinely just edges out Sailor B in a regatta on one design. Suddenly starts loosing to Sailor B. Your argument would be... the XXX rating system for these two class boats is not accurate. (I have NO examples of this occurring... fact is... the pecking order is about the same in either game)

I think what you want to argue is that handicap racing (and xxx rating system) is NOT AS PRECISE at sorting the pecking order by sailor skill. The analogy would be... two archers shoot bulls eye..... and are tied on points... One archer clustered his shots in a quarter ... while the other one filled the entire bulls eye. You would say... the test of skill could not resolve which of the archers was better that day. Next time... make the bulls eye smaller! (increase the precision needed)

IF you could get valid data... the statistics of signal averaging could get an extremely accurate rating.. of course that is a big if..... AND ignores the fact that you are comparing two slightly different games. My point that sailboat racing rules...(starboard has right away) CAUSE a good bit of the loss of precision in both one design and handicap racing..... So, Focusing on the accuracy of the ratings while ignoring the noise in the game is usually misguided. We actually KNOW how to manage this problem. We play the regatta game.... We spec out a fixed number of races to count . AND a fixed duration... with a fixed number of throwouts. (of course... all of these paramaters are heavily debated in coming up with the best game to sort out sailing skill)

Setting aside the details... here... I would support these statements.
One design racing is a more precise game to sort out sailing skill at an event.
It is VERY Difficult to get enough data to use the statistical power of signal averaging....the ratings are not perfect...
It is also very difficult to write a perfect formula. the ratings are not perfect.

Your conclusion.
Quote
It's a close swing at leveling the playing field and that's all. If you don't accept it as that, you won't ever enjoy it.


Is a very nice bottom line conclusion and I agree with it completely.
Posted By: David Ingram

Re: Portsmouth or SCHRS ??? - 02/05/18 05:31 PM

Originally Posted by ksurfer2
Originally Posted by Damon Linkous
Good discussion! My first exposure to SCHRS came with involvement in the Florida 300. I'm impressed with the math and analysis they use to arrive at the ratings.

The biggest roadblock I see to using it widely for local regattas in the USA (besides inertia - "we've always done it this way") is the nature of the bulk of racers at popular regattas (casual and have customized their boat in some way).

The way we do it for the Florida 300 is to use the ratings from the SHCRS ratings table http://www.schrs.com/ratings.php for a boat IF

The skipper can certify that their boat is a factory stock version of the rated boat, otherwise they need to get an individual SCHRS certificate.

If someone shows up to race with a slightly modified boat and no SCHRS certificate then the PRO will assign a rating.


Like if a highly modified Tornado would show up at the FL300, they would not be allowed to race with a stock Tornado rating, they would need a different rating. Right?


That would be correct, if your boat has been modified from stock you need to get a measurement cert. Buoy 44 got their boat measured the first year they did the event on site, the FL300 organizers made the arrangements. Your post reads like Buoy 44 ran a stock Tornado number and that is simply not the case. The stock T number is 0.949, Buoy 44 ran with .924.

Posted By: TexasTuma

Re: Portsmouth or SCHRS ??? - 02/07/18 02:19 PM

Originally Posted by Mark Schneider
Originally Posted by Damon Linkous


If someone shows up to race with a slightly modified boat and no SCHRS certificate then the PRO will assign a rating.


A ha.. the rest of the world calls this process PHRF! (just putting the conventional name to what you do)

Chances are your Race Committee PRO can do a pretty good job of guessing a fair rating.... The sailor can enter the race or not with that rating. The bar could host a lively discussion on ratings or the slimy reputation of XXX or whatever)

How good of a job the PRO does as a ratings expert/ sooth sayer is really not the point....PHRFng the rating is not a good or bad thing...Much of the sailing world in the USA uses PHRF quite happily. its simply just not a transparent or unbiased process.

The advantage that SCHRS provides is that for the NEXT EVENT.... the Owner can go get his gear measured, present the certificate with his transparent rating and play the game with a fully measured boat. Discussion about fair/not fair and bias is simply over. (It doesn't mean everyone is happy with the measured rating... but you know where you stand)


Mark, you're right. I currently serve on a local PHRF committee and we have been pushing ORC Club for the serious racers. The "debate" between Portsmouth and SCHRS seems to parallel PHRF vs ORC. Even though Portsmouth is supposed to be derived from observed performance, getting US Sailing to accept the results is quite a challenge. I run a Wednesday Night racing series (20 races during Daylight savings) and we have submitted the results every year for the last 15+ years. There is always a challenge to get acknowledgement. But, it appears that Portsmouth and PHRF (Performance Handicap Racing Formula) are a projected handicap based on a boat's performance; where SCHRS and ORC are more of a scientific measured rating system. I grew up with IOMR, which measures boat specifications and applies a rating based on that. Always seemed straight forward and fair. Now, our larger multihulls use a modified form of PHRF, and they have gotten pretty close to performance; but I am not a fan of a single point rating system. I have raced Nacras, Tornados, and Prindles. In the 90s, we used D-PN and I could tell you who would win based on the wind speed. From my experience, many people who first supported the ORC, quickly changed their tune when their favorable PHRF handicap wasn't a "gift" anymore.
Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/07/18 04:21 PM

Quote
I am not a fan of a single point rating system. I have raced Nacras, Tornados, and Prindles. In the 90s, we used D-PN and I could tell you who would win based on the wind speed.


I get it... but users seem to demand a single number system across the board. There does not seem to be much user demand for more elaborate tables.

With a performance based system (PHRF or Portsmouth) the argument for wind speed ratings is stronger. This argument is mitigated by the realization that sailing in breeze on conditions requires more skill and perhaps the performance differences are overstated. Tis a valid debate in the bar!!!

For measurement based systems (ORC or SCHRS) they build in the non linearity correction into the formula. Again, the precision of the game and the skill level bump up in breeze make it difficult to evaluate how well it handles non linearity. Tis a valid debate in the bar!!!

All of the handicap tables are fair minded attempts to make a game of sailing diverse boats possible. YMMV.... again.... a valid debate in the bar!!
Posted By: Ventucky Red

Re: Portsmouth or SCHRS ??? - 02/07/18 07:10 PM

Originally Posted by TexasTuma

I have raced Nacras, Tornados, and Prindles. In the 90s, we used D-PN and I could tell you who would win based on the wind speed.


Likewise, however, then we wern't experimenting with different sail plans, spinnakers, and other modifications as we are today... at least not until later in the decade. We went to SCHRS this year; however, I don't think the race committee realized that a boats with a modified sail plans needed a measurement...

So my question would be for those that don't have a measurement certificate, how do we level the playing field in an ad-hoc situation.... For instance someone showes up the day of the race with a Prindle 18 with a square top sail, or a NACRA 6.0 with the bridle tangs moved forward to accommodate a larger jib.... do we say OK, that will be a 5%, 10%, etc... hit? Or????

I don't want to be turning people away form a race, but on the other hand I want to see the system work..




Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/07/18 10:09 PM

The sailor is responsible for his rating.... If the RC made a mistake... you don't get to keep the trophy.... you are supposed to report it.... and correct the scoresheet.
Doesn't matter if its portsmouth, PHRF SCHRS etc. etc.

So, you make changes to your boat... you are responsible for correcting the rating if its warranted. You have to know your proper rating for the modifications you made.

Same principle in SCHRS.... the sailor is responsible to know his proper rating.

For your example... There are lots of options... He could get the measurement guidelines.... measure his own sail and calculate his rating. That is his measurement rating!

If the OA... says... Harry, you are blind... you can't read the rule... get somebody else to do it... Presto he has a third party rating.

The OA could say... Harry.... just get the numbers from the sailmaker.... the sails may have shrunk over time... but hey... its measured by a pro... if it matters to you get them remeasured. . So, he calls his sailmaker.... gets the numbers for his his non stock sails.... opens the calculator and crunches a new rating...

If he can't find the sailmaker... he can get any sailmaker to actually measure the sail using the SCHRS rules ... get a sail measurement certificate, crunch the numbers in the calculator and he has a measurement rating based on an even more authoritative measurement.

If the OA requires it.... (big deal race.....) He can go to a US SAiling /World Sailing sanctioned measurer and get an Official SCHRS measurement certificate.

The sail foot is 150 cm...... It doesn't change based on who is measuring it... What is changing is the level of authority which reports the rating to the OA.

This is no different then Portsmouth... you were supposed to report all modifications made to the one design boat that Portsmouth wanted. Calculate your rating and register your boat using it's proper rating. It doesn't get you off the hook if the scorekeeper did it properly or if he made an error... it was always your responsibility to enter with the proper rating and check it.

Remember, in Portsmouth the adjustments table was not allowed for important races like Area Qualifier regattas because the adjustments were just best guesses.

The OA sets the rules and level of compliance... the sailor meets the standard or not.
Can you be lazy and half butt it... sure...
The good news is that your decision only effects your fleet and racers... The decision on ratings does not effect anyone outside your fleet. the data are not collected so ... YMMV.
Posted By: Ventucky Red

Re: Portsmouth or SCHRS ??? - 02/08/18 12:18 AM

Originally Posted by Mark Schneider
The sailor is responsible for his rating.... If the RC made a mistake... you don't get to keep the trophy.... you are supposed to report it.... and correct the scoresheet.
Doesn't matter if its portsmouth, PHRF SCHRS etc. etc.

So, you make changes to your boat... you are responsible for correcting the rating if its warranted. You have to know your proper rating for the modifications you made.



In the case noted above we have many once a year racers show up... I am not about to tell them no you can't race after they drove 100 plus miles, paid for a hotel, and an entry fee..

With DP-N we can fix that right then and there with the published modifiers... I am not saying they are fair or accurate, but....... With SCHRS, not such an easy remedy... Joe Blow sailor may not have an interest getting all the "T's" crossed and "I's" dotted with being SCHRS compliant. I have directed a few people to the web site and told them to get the measurements form their sail makers so we can come up with a number..

Put yourself in my position.. how would you handle this situation.... a.) Tell them tough luck rules or rules you can't race b.) tell them those are non stock sails and there is a 5% penalty until you can provide a measurement. c.) Stick with DP-N.

Posted By: Mark Schneider

Re: Portsmouth or SCHRS ??? - 02/08/18 05:21 AM

Just spell out the rules in your NOR.
Handicap racing is conducted using SCHRS. Each skipper is responsible for registering with their proper rating. (reference table on web site)

If the owner cannot use the stock table or calculate their custom rating using the web site and available resources. The OA will generate a rating for the weekend using best available information and their judgement.

The OA is NOT measuring any equipment.

Designate somebody who understands the ratings process to serve on a protest committee in the event that you get a ratings protest from a competitor This is NOT the person who generates the weekend rating. . Let your judge / PC chair know the standards. They may want to spell out restrictions on equipment protests.... (that is a judge call there)

The stakes for the event are low and so you don't need high standards with certified rating certificates.... Its just overkill...

So for your situation.. by all means... Plan B
I think you have the conversation with them...
Non stock sails... OK... same size?.... or did you go bigger?

Same size different shape? ... use the stock rating.. Bigger... go with plan B. Nobody wants to cheat... they want to race once a year and enjoy the event. They certainly don't want to feel like they are putting one over on their friends in the fleet. So tell them... we try to be fair AND we lean to the fleet side of fair for your spitball rating . We are not measuring YOUR STUFF... They choose to register with that rating, get their stuff measured or go home. .... Tell them how it works... if they care enough... next time... they will bring a number and perhaps some math on a piece of paper. If you really want to accommodate them... allow them to submit a measurement rating before Sunday racing starts.... (ask the judge about this one)

If they are into the competition and boat design optimization thing... they will do the work themselves and present a number. They will have had plenty of time to get their rating sorted out when they follow your NOR rules.

I go into these things believing that people want a fair game with minimal stress. In the SCHRS world... the responsibility has shifted to the owner here. Your OA is just backstopping them so they can go racing.

I will try to get together with Will and create some NOR boilerplate that you can use.

Mark



Posted By: Jake

Re: Portsmouth or SCHRS ??? - 02/08/18 05:26 PM

Originally Posted by Ventucky Red
Originally Posted by Mark Schneider
The sailor is responsible for his rating.... If the RC made a mistake... you don't get to keep the trophy.... you are supposed to report it.... and correct the scoresheet.
Doesn't matter if its portsmouth, PHRF SCHRS etc. etc.

So, you make changes to your boat... you are responsible for correcting the rating if its warranted. You have to know your proper rating for the modifications you made.



In the case noted above we have many once a year racers show up... I am not about to tell them no you can't race after they drove 100 plus miles, paid for a hotel, and an entry fee..

With DP-N we can fix that right then and there with the published modifiers... I am not saying they are fair or accurate, but....... With SCHRS, not such an easy remedy... Joe Blow sailor may not have an interest getting all the "T's" crossed and "I's" dotted with being SCHRS compliant. I have directed a few people to the web site and told them to get the measurements form their sail makers so we can come up with a number..

Put yourself in my position.. how would you handle this situation.... a.) Tell them tough luck rules or rules you can't race b.) tell them those are non stock sails and there is a 5% penalty until you can provide a measurement. c.) Stick with DP-N.



Frankly, I would be realistic and come up with a reasonable number on the fly for a local event that doesn't have any regional or national consequence. Being a hard butt exclusionist does nothing but hasten the decline of our sport. I would consider applying the relative DPN percentage hit for whatever modification counted to the SCHRS number. It might take a little math but probably gets them in the ballpark. I would also probably err a little on the conservative side with a harsher rating (but do it with some specific math so I have some consistency and people can blame the formula instead of me). If they want a better rating under SCHRS, I would explain that they would be welcome to jump through the SCHRS hoop to prove out their number but above all, communicate how you derived that number and be open about it - let 'em race.
Posted By: Will_R

Re: Portsmouth or SCHRS ??? - 02/08/18 11:26 PM

So, I feel bad that Mark has been in here doing all the heavy lifting! I'm the technical rep for SCHRS in the US and I work with the World Counsel and Technical Committee on a variety of things; data review, areas of concern, changes to class rules, etc.

Mark has done a great job explaining how SCHRS works! I think one word that has been missed however (it was alluded to) is "Corinthian". The point is this, any class, any boat, someone can go out there and cheat. Unless you measure and inspect every boat on the water at every single race, someone could be breaking the rules, but do we do that? No, because it wouldn't make sense! There are a number of ways to say it, but, "is the juice worth the squeeze" is probably the one that most people will understand.

First and foremost, SCHRS will meet the needs of likely 95%+ of the sailors our there; guys like me who sail a Frankenboat are not in the majority. The semantics of "class legal", "stock" and "one design" could be argued for ages here, but... is the juice worth the squeeze? The point is, SCHRS states, "These rules are intended to allow a wide range of catamarans to race together. Boats from established classes with class rules must comply with their class rules and can use the ratings on the SCHRS list."

The other point in the SCHRS rules is this, "In case of doubt about any part of these regulations, the meaning, i.e. the spirit of the regulations governs." As such, lets just agree that, class legal is class legal. If you could take your H16, F18, A-cat, P19, N6.0, etc. etc. etc. to a nationals and race it without fear of being protested, you're good.

With that out of the way, 95% of the work is done! wink

Now, to the last 5% (that's a total SWAG guess, so don't hold me to it!). As Mark stated, the onus for how races are run is on the organizers. I might get myself shot by Jean-Claude for saying this, but... If the OA wants to use SCHRS, but allow sailors to measure their own boat, that is up to them. Again, Corinthian. As Mark said earlier, if someone shows up with a rating sheet that looks off.... like, a 20' boat listed at 4.9m, there's a problem. I would suggest that in cases where the OA wants to use SCHRS, but not require a full measurement certificate, the boat owner should provide not just a number, but a print out of their rating calculator spreadsheet with their entry. That said, boat owners should not expect that self developed rating to hold up for a larger race, or for SCHRS to approve it, because they won't.

I COMPLETELY DISAGREE that the OA's should throw ratings/modifiers out there on the fly... One of my biggest complaints (some people here will know what I'm talking about and this "major" race has yet to fix the problem...) is poorly developed NoR/SIs. Write the rules down clearly and unambiguously and publish them well in advance. If the OA says, "bring your own certificate", make sure the sailors know, fill out the #$@% spreadsheet, print a copy and bring it with you! Most of the people here aren't building their own hulls, they are taking an existing platform and changing the sails. There are >250 boats in the SCHRS table, surely almost everyone here can go to the table, take the published values and then fill in the blanks for sail measurements on the sail measurement form.

Although allowing/accepting self measured certificates induces a level of risk and reduces the integrity of the system, I think this is a more appropriate way to go than as Mark said, "PHRF'ing the number". If a racer doesn't like the measurement, they can go verify it themselves, but the rating formula and the integrity of the data that developed it remains the same. The other option is to use WAY outdated ratings from US PN and apply what are nothing more than WAG (not SWAG) modifiers. I'd prefer to put faith in people to honestly measure their boats than that.....
Posted By: Will_R

Re: Portsmouth or SCHRS ??? - 02/09/18 12:11 AM

Specific to the FL300 and the Buoy 44 boat. That was my boat and the experience of developing and racing it gave me a lot of valuable insight into both sides of this discussion.

First, the boat was officially measured for 2016 at the Islander just prior to the start. The forms were signed by Carla and submitted to SCHRS; I have the signed certificate and can assure you that it was not the same rating as a stock Tornado.

For 2017, I purchased a new spinnaker; besides the addition of rudder T-foils (does not affect rating on a boat with straight boards), the rest of the boat remained the same. The new sail was measured and a new ratings request officially submitted. Again, I have a signed copy of the certificate issued by SCHRS.

Overall, SCHRS did a very good job of rating this configuration relative to the N20c. There were times when each platform was in a more favorable range than the other, but you see that with any boat/race. In the end however, the race times supported the ratings for both platforms. We had several break downs, so we didn't perform as well in 2017, but I am MUCH happier that we raced under SCHRS instead of Portsmouth.

With regards to Portsmouth; the rating, once the modifiers were applied, resulted in the modified Tornado owing the N20c time! So, a boat designed in 1962 that is narrower, shorter and has pizza pans for dagger boards rates faster than a modern wave piercer with more volume, sail area and lifting boards??? Although the T did weigh less, that isn't enough to overcome the advantages that the N20c has in pure speed. This kind of handicap is the reason that we didn't run the boat in that configuration in the GT300; US PN over penalized the modifications and has not updated the F-18 to address development in that class. Note that there is still NOT a published rating for the N20c under US PN and that highlights one of its major problems; lack of support/updates over the past decade.

In that same line of thought, US PN relies on race data to develop ratings, once a new boat is released, it would take a year or more to come up with a somewhat "reliable" rating. SCHRS can rate it before it hits the water with a pretty high degree of certainty AND as race data is analyzed, make adjustments as necessary when anomalies are found. This is a good example of how SCHRS is handling the adoption of deck sweepers on the F-18, or foiling (among other changes) in the A-cats.

In the case of the changes to the F-18, the recent opinion of the SCHRS world council was to be careful to not make a decision that hurt the integrity of the system. In 2018, like every other year, data will be collected, analyzed and anomalies identified; the F-18 (along with a couple of others) will be under the microscope to determine if/how overall fleet performance was affected by the adoption of the new mainsail configuration. The data used for that analysis is from a much MUCH broader pool than is available in just the US. As such, the statistical significance is much higher.

SCHRS leadership is committed to ensuring the integrity of the system. A lot of work goes in to collecting race data, looking for problems and making sure that the system remains viable into the future.

If you have a few minutes and are curious, go read the annual world council reports available here: http://www.schrs.com/inc/SCHRS_Review_20180129.pdf

Previous reports are located on this page: http://www.schrs.com/news.php
Posted By: Jake

Re: Portsmouth or SCHRS ??? - 02/09/18 01:35 AM

Originally Posted by Will_R


I COMPLETELY DISAGREE that the OA's should throw ratings/modifiers out there on the fly...


The guy that does one, maybe two regattas a year, is going to quit coming to the regatta if you put hurdles in front of him that he really doesn't care about. It's just not worth giving somebody a negative opinion. Throw a piece of bubble gum at a wall and give him a number. Let him race, have fun, no fuss, and see you next year. Offer to point him in the right direction if he wants to build a real SCHRS number for his boat. It's worth the risk that that one boat runs away with all the prize money....

A few years ago, we had a serious resurgence starting with Hobie 16s in our area at local regattas. We had two situations with two regattas in one year where one had poor communication at one and another suffered one sour attitude that resulted in handicap and class issues and a bunch of Hobie 16s feeling like outsiders. They evaporated and we lost all momentum from a fleet that was on the cusp of outnumbering all other boats combined on a regular basis. It was dumb and I really regret that we weren't able to fix it. Kill the hurdles and tone down the seriousness at the low level regional regattas.

That said, I'm NOT talking about a major regional (or bigger) event - like the Florida 300 or whatever. Absolutely, everyone that is putting a lot of effort into a campaign for that event should expect a fair and refined playing field - real handicap numbers should definitely be required.

And yes, Portsmouth is pretty much static at this point. I don't think anyone can actually run the statistics to do a real refresh on a single rating and, even if they were able to, I doubt they're getting any event results submitted to them.
Posted By: Isotope235

Re: Portsmouth or SCHRS ??? - 02/09/18 01:41 AM

Originally Posted by Will_R
As such, lets just agree that, class legal is class legal. If you could take your H16, F18, A-cat, P19, N6.0, etc. etc. etc. to a nationals and race it without fear of being protested, you're good.

With that out of the way, 95% of the work is done!

On the other hand, if you sail a one-design catamaran not already listed in the SCHRS tables, you have a lot of work - and a lot of guesswork - to do in order to generate a fair and honest rating. Anybody who claims you can simply plug a few simple measurements into the SCHRS spreadsheet hasn't tried.

Quote
With regards to Portsmouth; the rating, once the modifiers were applied, resulted in the modified Tornado owing the N20c time! So, a boat designed in 1962 that is narrower, shorter and has pizza pans for dagger boards rates faster than a modern wave piercer with more volume, sail area and lifting boards???

With regards to SCHRS, I made an honest and good faith effort to measure my class-legal Isotope, and the official spreadsheet showed it owing the Goodall Viper F16 time! So, a boat designed in 1962 that is narrower, has a shorter mast, and shallow centerboards rates faster than a modern wave piercer with more volume, sail area, and a spinnaker???

I'd be happy to race under SCHRS handicapping if the system were anywhere near as simple to use or as accurate as its proponents claim - but it isn't.

Regretfully,
Eric
Posted By: Will_R

Re: Portsmouth or SCHRS ??? - 02/09/18 05:57 AM

Jake, reread what I said. The goal is to make it easy while maintaining as much of the original integrity as possible. How many 1-2 races per year guys aren't racing a stock boat? If they are putting forth the effort to get to a race and they don't have a stock boat, so long as the OA had set it up this way, run what you bring, but have the decency to take 30 minutes to measure your sails and fill out the spreadsheet. So long as the OAs put the info out in time, is it really that hard? Show me a list of boats that you see annually at races in your area that aren't included in the current SCHRS table. (That is both a challenge and... I could use the data if it exists...)

Eric, I heard about your case through the grapevine. I've gotten two measurement certifications for my own boat, have written an in depth slide presentation on SCHRS, assisted in developing a guide for boat owners to get a rating, deconstructed the equations and the spreadsheet and have even put it into MathCAD and replicated what the calculator produces. If you will get me data, we will figure out what is going on with the rating that you calculated.

In all honesty, the Isotope is one of the classes that was on my list to look into, but if you saw the comparison that I assembled which lists all of the boats in US PN and SCHRS tables, you would understand the size of the task at hand. Honestly, part of the reason that the rules require a recognized/certified measurer (in my opinion) is to make sure that measurements are both accurate and consistent. I'm not saying that you did it incorrectly, but if you're numbers are as you say... Something has to be going on there.
Posted By: Isotope235

Re: Portsmouth or SCHRS ??? - 02/09/18 04:47 PM

Originally Posted by Will_R
If you will get me data, we will figure out what is going on with the rating that you calculated..

The numbers I used were:
Crew = 1
WS = 113.60
AL = 4.880
WL = 4.496
BEAM = 2.234
CM = 14.567
VLM = 7.390
CJ = 3.730
VLJ = 4.983
CSPI = 0
TRAP = 1
B27 = Yes
LTM = 0.634
SH = No
LF = 0

Which generated a rating of 1.050 with the 2015 SCHRS spreadsheet.

I took most measurements from my boat, but some (like weight) are from the manufacturer. Sail measurements are from my sails according to Formula 40 (I didn't re-measure them from the SCHRS diagram). The Isotope class rules restrict total sail area to 185 sq/ft, but permit any ratio of main to jib area, and allow either square or pin-top mainsails. I figured there would be more variation from sail to sail than between measurement methods. After all, if other legacy boat sail measurements were taken from published sources, that should be ok for Isotopes too. Most of us are running 44 sq/ft in the jib and 141 sq/ft in the main.
Posted By: Will_R

Re: Portsmouth or SCHRS ??? - 02/09/18 08:48 PM

Eric, do you have a copy of the class rules? I looked online and didn't find them.
Posted By: Isotope235

Re: Portsmouth or SCHRS ??? - 02/09/18 10:06 PM

Originally Posted by Will_R
Eric, do you have a copy of the class rules? I looked online and didn't find them.

I sent you a PM
Posted By: Ventucky Red

Re: Portsmouth or SCHRS ??? - 02/09/18 11:46 PM

Originally Posted by Jake
[quote=Will_R]
The guy that does one, maybe two regattas a year, is going to quit coming to the regatta if you put hurdles in front of him that he really doesn't care about. It's just not worth giving somebody a negative opinion. Throw a piece of bubble gum at a wall and give him a number. Let him race, have fun, no fuss, and see you next year. Offer to point him in the right direction if he wants to build a real SCHRS number for his boat. It's worth the risk that that one boat runs away with all the prize money....



Bingo...

I would like to see SCHRS become the norm; however, as I stated earlier, not many folks are going to perform the gymnastics needed to get their boats in compliance should the have altered the sail plan etc... as they are the once or twice a year racers... And in our case many of them are Frankenboats.

I think this needs to be handled by each race committee noting on the NOR that you're using SCHRS for the rating system. And if you're not compliant with measurement to your modifications than a X% penalty will be applied until you can either a.) furnish a measurement certificate, or b.) measurements from your sail maker that can be plugged into the on-line calculator where an agreeable rating number can be assigned.

On another note, I agree, it really shouldn't be that hard to be in compliance. With most of the modifications that come into play are with sails many times going from a pin to a square top, getting the numbers from any sail maker shouldn't be that difficult. My question would be are the "reputable" sail makers of our community in tune with the SCHRS requirement for measurement? And, if so could/would they include a measurement sheet with the purchase of a new set of sails?
Posted By: Mike Fahle

Re: Portsmouth or SCHRS ??? - 02/11/18 01:27 AM

Here is the latest SCHRS to PY chart I could find: https://www.schrs.com/pylookalike.php

Here is a complete reference for Portsmouth Yardstick: http://www.ussailing.org/racing/offshore-big-boats/rating-rules/#1471969539173-9c4d8bd4-7aff

These sources should help a lot to rate different boats.

Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/12/18 01:39 AM

Ventucky Red,

The answer is yes. Glaser for example will include a F18 measurement form with their sails, they are certified class measurers on the F18 side and I would fully trust them to provide accurate sail area data to compute a SCHRS rating. Any of the lofts building A-Cat sails should also be capable of the same.

One issue with the SCHRS rating scheme is the mainsail area includes the mast. So you need to measure the mast area. That is pretty straightforward. It helps to look at the F18 measurement certificate which clearly outlines how to measure sails and the mast. The US F18 class website also has detailed photographs of sail measurement. Its about 1 hr for a 3 sail boat.

Jake,

I hear you, but applying DPN corrections to SCHRS doesn't work. We've played this game locally. Get your sail area if that is the change and run the calculator. It is easy because the numbers for almost every boat are readily available online, type those into the excel calculator and update the sail area. I do this for our fleet, maybe you can designate someone for your local fleet?

Eric,

Unfortunately SCHRS doesn't differentiate between pinhead or square top sails etc. They do have a sinking correction factor which I think you should use for the Isotope, and on the 2018 rating calculator this gives you a SCHRS number of 1.072, quite a bit slower than a 1 up F16 (1.041). Without this I get a number of 1.057, again relatively slower than a 1 up F16. I used a board depth below waterline of 0.56 m, the number for the Taipan 4.9 (which in stock configuration has very short and stubby boards). You didn't post a number from what I can tell, so that may be part of your ratings issue. Personally I feel the 1.057 number is a fair rating considering the following statement on the Isotope website:

"The Isotope Catamaran is a registered Formula 16 boat!
The hulls meet the 16ft LOA requirements of the Formula 16HP class. The strong points of the Isotope are that its balanced helm allows it to out point any other catamaran to windward. An Isotope meeting the One Design class specifications can be raced as a single handed Formula 16 boat. An Isotope with a spinnaker can be raced with crew in the Formula 16 one up class."

If the hull doesn't plane, maybe the 1.072 number is fair, maybe. How does the boat sail compared against a 1 up Blade, Falcon, Viper or Nacra F16?

-Sam
Posted By: Isotope235

Re: Portsmouth or SCHRS ??? - 02/12/18 02:21 PM

I hesitate to resurrect this discussion, since I've already gone into details at https://www.catsailor.com/forums/ub...ds/%2Bschrs/Search/true/schrs#Post282859, but:

Originally Posted by samc99us
Unfortunately SCHRS doesn't differentiate between pinhead or square top sails etc.

Really? Then what is LTM (length of top of mainsail) for?

Quote
They do have a sinking correction factor which I think you should use for the Isotope, and on the 2018 rating calculator this gives you a SCHRS number of 1.072, quite a bit slower than a 1 up F16 (1.041). Without this I get a number of 1.057, again relatively slower than a 1 up F16.

SH (sinking hull) is "only for HC14, HC16, Prindle 14 and 16". While I could get a fair number by claiming the SH adjustment, and omitting mast area from sail area, that would be illegal. SCHRS claims to produce fair handicaps without cheating.


Quote
I used a board depth below waterline of 0.56 m, the number for the Taipan 4.9 (which in stock configuration has very short and stubby boards). You didn't post a number from what I can tell, so that may be part of your ratings issue.

Sorry, I inadvertently omitted VLB when transcribing numbers in my previous post. I measured VLB = 0.560 for the Isotope.

Quote
Personally I feel the 1.057 number is a fair rating considering the following statement on the Isotope website:
"The Isotope Catamaran is a registered Formula 16 boat!
The hulls meet the 16ft LOA requirements of the Formula 16HP class. The strong points of the Isotope are that its balanced helm allows it to out point any other catamaran to windward. An Isotope meeting the One Design class specifications can be raced as a single handed Formula 16 boat. An Isotope with a spinnaker can be raced with crew in the Formula 16 one up class."

When the F16 class was first created, a number of existing 16 foot catamarans were grandfathered in, including the Isotope and the Hobie 16. Technically, both the Isotope and the Hobie 16 MAY race as F16 class boats. That doesn't mean that they actually are the same speed as a modern F16 design. If it did, then why does the Hobie 16 have a SCRHS rating of 1.193 rather than 1.050?

Does anybody really believe that 45 years of marine engineering, including the advent of computer modeling, CNC manufacturing, and the addition of spinnakers has yielded no difference whatsoever in boatspeed? I don't.

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If the hull doesn't plane, maybe the 1.072 number is fair, maybe. How does the boat sail compared against a 1 up Blade, Falcon, Viper or Nacra F16?

I haven't raced directly against against a Blade, Falcon, Viper, or Nacra F16. They've always been in "A-Fleet" whereas I sailed in "B-Fleet". The times I have sailed on the same racecourse, the A-Fleet boats were definitely faster. I have raced several times against Hobie 16s (1- and 2-up), Hobie 17s, and Hobie 18s. The Isotope is definitely faster than a Hobie 16, perhaps a little more than the US Portsmouth handicap indicates. Although US Portsmouth rates the Hobie 18 faster than an Isotope, I was often able to beat some H-18s around the course. I'd be willing to race boat-for-boat against a H-18. To claim that a 1-up Isotope is as fast as a 1-up Goodall Viper (which carries a spinnaker larger than the Isotope's main and jib combined) however, is ridiculous.
Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/12/18 09:59 PM

Eric,

We can move this conversation over to the other thread if you prefer. I will briefly answer some questions here.

1) LTM = is length of the top of the mainsail as you state, so it does factor in and my apologies on misspeaking on that front.

2) I'm not sure the sinking hull correction applies only to H14's and H16's. I would have to dig into that more. Will probably knows the answer off the top of his head.

3) So I used the same VLB. I would have to look at the formulas directly but I don't believe SCHRS distinguishes between short stubby Tornado-like centerboards and narrow, high aspect ratio F18 like daggerboards beyond this number, i.e you could build a boat with very high VLB but super big chord and be slow.

4) I was quoting the Isotope class website, NOT the F16 class website when making that statement. I'm not arguing your point that 45 years of technology hasn't made a significant impact on boat speed, because it has, but the Isotope manufacturer is claiming the boat as a fantastic trainer for the Tornado (same statement made by the F16 class) and they are the ones claiming the boat performs as good or better than an F16!!!!

5) When looking at the SCHRS numbers, one big thing sticks out to me in general, and that is platform and sailing weight matter a healthy amount to the final number. I would weigh your actual platform if at all possible, as I suspect it is heavier than the 113 kg you have quoted (even the Blade F16's aren't really there). That could drive you back to a more 'fair' number.

6) SCHRS may not be creating a perfect number for your boat in a long downwind race, but take a look at the Taipan 4.9 numbers. I'm referencing that as I believe it is pretty similar to the Isotope in many ways (including design age). The big thing is they race without the jib in solo mode. Add the jib in and you drive the number from 1.097 to almost half, or 0.980. That may need some looking into on the SCHRS side as I doubt the boat is actually twice as fast with a jib as without.

Hopefully we can resolve your issue, and I'm okay with it being public because it is important for others to see the process and become familiar with it.
Posted By: Isotope235

Re: Portsmouth or SCHRS ??? - 02/12/18 11:40 PM

Originally Posted by samc99us
2) I'm not sure the sinking hull correction applies only to H14's and H16's. I would have to dig into that more. Will probably knows the answer off the top of his head.

Direct quote from the SCHRS calculator: "Sinking Hull (Only for HC14, HC16, Prindle 15 and 16".

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4) I was quoting the Isotope class website, NOT the F16 class website when making that statement. I'm not arguing your point that 45 years of technology hasn't made a significant impact on boat speed, because it has, but the Isotope manufacturer is claiming the boat as a fantastic trainer for the Tornado (same statement made by the F16 class) and they are the ones claiming the boat performs as good or better than an F16!!!!

Please let's distinguish between marketing hyperbole and reality.

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5) When looking at the SCHRS numbers, one big thing sticks out to me in general, and that is platform and sailing weight matter a healthy amount to the final number. I would weigh your actual platform if at all possible, as I suspect it is heavier than the 113 kg you have quoted (even the Blade F16's aren't really there). That could drive you back to a more 'fair' number.

Yes, SCHRS places a large performance factor on platform weight. Yes, the Isotope Class Rules specify a minimum weight that is unrealistic. 275lbs would be a more reasonable number, and I understand that most Isotopes weigh at least 280. Rather than trying to get a rating for MY PARTICULAR ISOTOPE, I was trying to get a rating for the class, and SCHRS uses the Class Rules for that. I can contact the manufacturer to try to fix the class rules. A 1.1% change in minimum boat weight yields a 2% change in rating. In racing against other sailors who weigh 25 pounds less than I do, I don't see that large a speed difference on the water.

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6) SCHRS may not be creating a perfect number for your boat in a long downwind race, but take a look at the Taipan 4.9 numbers. I'm referencing that as I believe it is pretty similar to the Isotope in many ways (including design age).
According to sailboatdata.com, the Tiapan 4.9 was designed in 1982. The Isotope was designed I'm 1962 - hardly the same design age. Please note that the Tiapan 4.9 was also billed as an F16 class boat but it does not carry the F16 rating. The Taipan 4.9 Solo has an SCHRS rating of 1.097. I'd be quite happy with that rating for an Isotope.

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The big thing is they race without the jib in solo mode. Add the jib in and you drive the number from 1.097 to almost half, or 0.980. That may need some looking into on the SCHRS side as I doubt the boat is actually twice as fast with a jib as without.

That's a point I've made before which has fallen on deaf ears. If I were to take a 40sqft jib off the Isotope altogether, and add a 188sqft spinnaker (the standard F16 size), then the Isotope SCRHS rating would go from 1.050 to 1.108. That's right - add 148sqft of sail area (a 58% increase) and the boat gets 5.5% SLOWER!

Looking at things a different way, if you sail an F16 class boat single-handed with main and jib, rather than main and spinnaker, SCHRS says it will be more than 5% faster. According to SCHRS, jib area is 9 times more important than spinnaker area. That makes no sense whatsoever. If it were true, then nobody would use a spinnaker at all!
Posted By: Jake

Re: Portsmouth or SCHRS ??? - 02/13/18 11:21 PM

Originally Posted by samc99us

Jake,

I hear you, but applying DPN corrections to SCHRS doesn't work. We've played this game locally. Get your sail area if that is the change and run the calculator. It is easy because the numbers for almost every boat are readily available online, type those into the excel calculator and update the sail area. I do this for our fleet, maybe you can designate someone for your local fleet?




You guys are either being idealist, argumentative, or you've never met a casual sailor that does one or two regattas a year on a franken boat. There's nothing wrong with taking what the relative % rating hit in Portsmouth for any of the modifiers and applying it to get some sort of roughly approximated SCHRS number so a casual sailor can pay your regatta entry fee and have a good time with everyone else. While we're taking everything so seriously, we're not noticing how utterly unattractive it is to an outsider.
Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/14/18 09:37 PM

Eric,

The issue with how jibs are rated is a serious one and has been taken up with the SCHRS international committee, so your concern is not falling on deaf ears. One note on this subject is jib area is working for you upwind and downwind, so it is possibly twice as effective per area unit of spinnaker. That is unlikely really the case but it is a possible explanation as to where the number is coming from.

The weight penalty is a peculiar one, we will dig into that as well. I will say that at the top of the F18 fleet, 25 lbs easily results in the 2% change noted. There is a very detailed paper regarding this that was recently published including the statistics to support this.

Unfortunately at the moment there are a number of different F16 ratings (every manufacturer has one that isn't just the published F16 rating). I'm not quite sure what the solution to this is. If you have measured weights for the Isotope fleet and can generate an average, that would be more than fair I believe for the SCHRS rating.

Jake,

I was trying to be idealistic, because our local fleet did as you are suggesting for 2 years and it doesn't result in a 'fair' rating per SCHRS (see the jib vs. spinnaker area issue above). If your fleet is okay with this, then go for it. I just kindly suggest setting up a fleet SCHRS focal point that can generate ratings for the frankenboats given basic input data for future events. That is what we do locally-I run the ratings as I volunteered, it is fast for me, and my number doesn't change (F18's have been 1.000 for a while now). I will kindly generate numbers for other boats if they can provide the input data, or if I am at an event and not fixing the bottom of my daggerboards, I will help measure. I will see what I can do to become an approved measurer.

Posted By: Ventucky Red

Re: Portsmouth or SCHRS ??? - 02/14/18 10:30 PM

Originally Posted by samc99us

I was trying to be idealistic, because our local fleet did as you are suggesting for 2 years and it doesn't result in a 'fair' rating per SCHRS (see the jib vs. spinnaker area issue above). If your fleet is okay with this, then go for it. I just kindly suggest setting up a fleet SCHRS focal point that can generate ratings for the frankenboats given basic input data for future events. That is what we do locally-I run the ratings as I volunteered, it is fast for me, and my number doesn't change (F18's have been 1.000 for a while now). I will kindly generate numbers for other boats if they can provide the input data, or if I am at an event and not fixing the bottom of my daggerboards, I will help measure. I will see what I can do to become an approved measurer.



Sam,

Once you do become an "approved measurer" let me know what needs to be done as this is something I may want to do...

With that, the calculator and the other instructions that are online will work as much of the data has already been done... that is some one with a Prindle or Dart 18 shows up with a new square top all I need to do is go to the rating table, plug in the known data, then the new data for the sails (CM & CJ) and get a number.... easy peasy lemon squezzy right?????? Wrong!!!!!!!

The problem I had last year was that some sailors were not able to get the required measurements from the sail makers.. Even with my new sails for the P18 from Whilewind, Chip almost choked when I sent him the chart below noting that he didn't have the time to do this.. In the case of the Dart 18 sailor he noted the Glasser was not able to do this asw well... which was suspect to me, but that is another story..

[Linked Image]

I am going to try and messure my new sails and will send you the messurements to see if they "jive" with mine..

More to come
Posted By: bacho

Re: Portsmouth or SCHRS ??? - 02/15/18 12:29 PM

Originally Posted by Ventucky Red
Originally Posted by samc99us

I was trying to be idealistic, because our local fleet did as you are suggesting for 2 years and it doesn't result in a 'fair' rating per SCHRS (see the jib vs. spinnaker area issue above). If your fleet is okay with this, then go for it. I just kindly suggest setting up a fleet SCHRS focal point that can generate ratings for the frankenboats given basic input data for future events. That is what we do locally-I run the ratings as I volunteered, it is fast for me, and my number doesn't change (F18's have been 1.000 for a while now). I will kindly generate numbers for other boats if they can provide the input data, or if I am at an event and not fixing the bottom of my daggerboards, I will help measure. I will see what I can do to become an approved measurer.



Sam,

Once you do become an "approved measurer" let me know what needs to be done as this is something I may want to do...

With that, the calculator and the other instructions that are online will work as much of the data has already been done... that is some one with a Prindle or Dart 18 shows up with a new square top all I need to do is go to the rating table, plug in the known data, then the new data for the sails (CM & CJ) and get a number.... easy peasy lemon squezzy right?????? Wrong!!!!!!!

The problem I had last year was that some sailors were not able to get the required measurements from the sail makers.. Even with my new sails for the P18 from Whilewind, Chip almost choked when I sent him the chart below noting that he didn't have the time to do this.. In the case of the Dart 18 sailor he noted the Glasser was not able to do this asw well... which was suspect to me, but that is another story..

[Linked Image]

I am going to try and messure my new sails and will send you the messurements to see if they "jive" with mine..

More to come





The computer does not spit out those numbers. Gotta be measured by hand. I am sure they can measure them for the customer. Its just another $75 charge.
Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/15/18 01:35 PM

That depends on the software Bacho. I don't really see how you can design class legal sails in a software package that doesn't give you sail area. I would bet good money that North, Quantum's and Doyle's in-house software gives you sail area, as does Smart Azure but I could be wrong. All my wing design tools generate area...now, the final product? That could still be different than what you drew for a myriad of reasons that you know waay more about than me.

Why Glaser can't provide this, I don't fully understand. They can measure F18 sails so they definitely can measure other class sails...but they should be providing the area. Its frustrating to me because we are working on a Nacra Inter 20 rules re-write locally that doesn't change the sail area but opens up the builder options, yet Glaser won't tell us the area of the sails they have built for the class (that we would like to make sure fit within the rules).

Ventucky Red, this is a helpful link: http://usf18.com/measurement-tips-and-pics/

I would also download the F18 measurement template. It has all the math built in for the diagram you have.
Posted By: Ventucky Red

Re: Portsmouth or SCHRS ??? - 02/15/18 02:40 PM

Originally Posted by samc99us



I would also download the F18 measurement template. It has all the math built in for the diagram you have.


Mr. Google is not helping me here.... do you have a link or can you send me the spreadsheet?
Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/15/18 06:08 PM

http://www.f18-international.org/documents/measurement-forms/
Posted By: bacho

Re: Portsmouth or SCHRS ??? - 02/15/18 10:00 PM

Originally Posted by samc99us
That depends on the software Bacho. I don't really see how you can design class legal sails in a software package that doesn't give you sail area. I would bet good money that North, Quantum's and Doyle's in-house software gives you sail area, as does Smart Azure but I could be wrong. All my wing design tools generate area...now, the final product? That could still be different than what you drew for a myriad of reasons that you know waay more about than me.

Why Glaser can't provide this, I don't fully understand. They can measure F18 sails so they definitely can measure other class sails...but they should be providing the area. Its frustrating to me because we are working on a Nacra Inter 20 rules re-write locally that doesn't change the sail area but opens up the builder options, yet Glaser won't tell us the area of the sails they have built for the class (that we would like to make sure fit within the rules).



The software certainly spits out a SA number, buts its not the same number that you will arrive at measuring by hand as shown above. They can be different for a number of reasons, some of which I do not fully understand yet myself. If they gave you a number from their computer, its not a number likely to be recreated when someone attempts to measure that sail by hand.

Anyways, if you want Glaser or anyone else to fill out that chart, they will need 2 people and half an hour with the sail in their possession to get these numbers. Thats why they charge $75 extra for a "certified" F18 sail. IMO, the certification only says that on X date the sail measured X when measured by approved methods.
Posted By: Jake

Re: Portsmouth or SCHRS ??? - 02/16/18 01:02 AM

Originally Posted by samc99us
That depends on the software Bacho. I don't really see how you can design class legal sails in a software package that doesn't give you sail area. I would bet good money that North, Quantum's and Doyle's in-house software gives you sail area, as does Smart Azure but I could be wrong. All my wing design tools generate area...now, the final product? That could still be different than what you drew for a myriad of reasons that you know waay more about than me.

Why Glaser can't provide this, I don't fully understand. They can measure F18 sails so they definitely can measure other class sails...but they should be providing the area. Its frustrating to me because we are working on a Nacra Inter 20 rules re-write locally that doesn't change the sail area but opens up the builder options, yet Glaser won't tell us the area of the sails they have built for the class (that we would like to make sure fit within the rules).

Ventucky Red, this is a helpful link: http://usf18.com/measurement-tips-and-pics/

I would also download the F18 measurement template. It has all the math built in for the diagram you have.



There are several different prescribed sail area measurement systems and some classes had their own that varied. Sails can be designed to work within a particular system to have a little more real world sail area and still measure in. The measurements are all just an approximation of area taken at a few reasonably practical points. The sail area generated from the software used to design a sail will be different from a sail that's measured manually...and to measure in to any rule, the sail needs to be measured per the prescribed method. I seem to remember that F18 originally had a slightly simpler, self prescribed, sail measurement procedure and that they adopted the ISAF method when they become a fully fledged ISAF class. Both systems would come up with a different number for any given sail and neither would match the software number. A sail measurer is usually listed/recognized with the class they're measuring for and some classes require some level of sailing organization certification to be a measurer. You may also be recognized by one class and not another. In order for Glaser to measure a class sail, he has to learn the measurement method (assuming SCHRS is different) and actually perform the measurement...if it's not a system that he (or Pease) will use often enough, I can see why he would have chosen to not offer the service.

That said, the Nacra 20 sails? I can probably guess why nobody would want to get involved with those numbers! Political football that probably has a pattern of variation in a distinct path...but I can only guess.

(BTW, Bacho has been designing sails in various software packages from low budget to high end and I've helped produce a few - I was also an F18 sail measurer for a while).
Posted By: Ventucky Red

Re: Portsmouth or SCHRS ??? - 02/16/18 06:54 PM

Originally Posted by bacho


The software certainly spits out a SA number, buts its not the same number that you will arrive at measuring by hand as shown above. They can be different for a number of reasons, some of which I do not fully understand yet myself. If they gave you a number from their computer, its not a number likely to be recreated when someone attempts to measure that sail by hand.



When my in laws redid their kitchen, the counter guys did the measurements by laser.. I wasn't there, but my FIL (who was an Apollo project rocket surgeon for both Rockwell and Grumman) told me it was pretty slick... they had some pretty odd angles along with an island that had an arched side (leech) and the finished product fit like a glove right down to the mm when they installed it...

I am wondering if this technology could work for us?







Posted By: brucat

Re: Portsmouth or SCHRS ??? - 02/17/18 01:46 PM

This is a very interesting thread, and brings out a lot of really great points.

As Jake said, there are different levels of regattas, and managing handicaps should be taken as seriously (or not) as the level of regatta. But, you run the risk of alienating anyone who does take it seriously when you start to bend rules. Finding the right balance, and setting the expectation/tone (communication!!!) is the key.

If we move to a new system, or even just start seeing more handicap racing, it will put more emphasis on getting the ratings right before racing. Unless you have a dedicated volunteer (or team), don't expect much to happen on Saturday morning of a weekend regatta, in terms of settling numbers.

But, we've all been to regattas where someone has clearly been allowed to break a class rule, just to get the regatta numbers up. Whether racing OD or handicap, this is not a problem if handled well (communicate well with the legal boat owners, and don't start letting the whole thing turn into frankenboats over time), and as long as the illegal boats don't win.

Mike
Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/20/18 05:44 PM

Originally Posted by bacho
Originally Posted by samc99us
That depends on the software Bacho. I don't really see how you can design class legal sails in a software package that doesn't give you sail area. I would bet good money that North, Quantum's and Doyle's in-house software gives you sail area, as does Smart Azure but I could be wrong. All my wing design tools generate area...now, the final product? That could still be different than what you drew for a myriad of reasons that you know waay more about than me.

Why Glaser can't provide this, I don't fully understand. They can measure F18 sails so they definitely can measure other class sails...but they should be providing the area. Its frustrating to me because we are working on a Nacra Inter 20 rules re-write locally that doesn't change the sail area but opens up the builder options, yet Glaser won't tell us the area of the sails they have built for the class (that we would like to make sure fit within the rules).



The software certainly spits out a SA number, buts its not the same number that you will arrive at measuring by hand as shown above. They can be different for a number of reasons, some of which I do not fully understand yet myself. If they gave you a number from their computer, its not a number likely to be recreated when someone attempts to measure that sail by hand.

Anyways, if you want Glaser or anyone else to fill out that chart, they will need 2 people and half an hour with the sail in their possession to get these numbers. Thats why they charge $75 extra for a "certified" F18 sail. IMO, the certification only says that on X date the sail measured X when measured by approved methods.


That makes a lot more sense Bacho. Not an easy nut to crack given those limitations.
Posted By: Jake

Re: Portsmouth or SCHRS ??? - 02/21/18 12:24 PM

The reason that sail measurement methods and computer design softwares differ in sail measurement reading is because the software is using advanced math (derivation, etc) and getting a very accurate sail area figure. It is also taking into account the entire surface area that is formed by the 3D shape that you don't get when you lay a sail flat on the ground. Physical sail measurement methods generally use a series of defined triangles to approximate the sail area as well. Also, because sails aren't straight line triangles, but the prescribed measurements are, the result of a physical measurement is only an approximation of sail area - but not the actual sail area. The accuracy of a sail measurement system is correlated to the number of measurement points and since it's impractical to have (for instance) 3,000 measurement points, most systems make a compromise in the number of measured points vs. the accuracy of the result. However, if there isn't enough accuracy with the measurement system, the door opens to sail designs that work around the system and stuff sail area into the sail in ways that the measurement system cannot measure. It's all a balance in practicality, accuracy, and keeping things in check.

Posted By: samc99us

Re: Portsmouth or SCHRS ??? - 02/21/18 04:03 PM

Jake,

I got all that. The biggest issue is with classes that don't have or use a prescribed sail area measurement system. I recommended the F18 one because it has a reasonable degree of accuracy, there are step by step instructions and a form that does all the math for you once you've done the measuring. Is it the best system? Probably not. Will it get the job done for SCHRS? Most likely.
Posted By: Jake

Re: Portsmouth or SCHRS ??? - 02/22/18 04:30 PM

I thought F18 had adopted the standard ISAF measurement method when they became a recognized class. I'm pretty sure the A-cat uses that system...would probably need to research a bit. Either way, I agree that the F18 system is pretty thorough with a well thought out form.
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