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Re: Charleston RW [Re: brucat] #271741
04/23/14 04:10 PM
04/23/14 04:10 PM
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On the Water
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Originally Posted by brucat
OK, so far we have Mark Schneider, Dave Ingram, and Sam in favor of changing to a new system.

Add me to that list. It's long overdue and way past time to put Portsmouth to pasture.


Philip
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Re: Charleston RW [Re: Mark Schneider] #271743
04/23/14 05:50 PM
04/23/14 05:50 PM
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OK, we should probably take this to a separate thread, but are we adding you to the list of people who will take action on this?

Mike

Re: Charleston RW [Re: brucat] #271751
04/23/14 08:28 PM
04/23/14 08:28 PM
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Annapolis, MD
Mark Schneider Offline OP
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Mike...
This is not an MHC call.... FACT... Each Club makes that call of what handicap system to use based on what their members want to use.

BUT the MHC and US Sailing can take a leadership position here.

How did it work BACK IN THE DAY!.... it was contentious to switch from NAMSA to USA Portsmouth.... Those in the know had an opinion.... The sailors ultimately decided that the US SAILINGS stamp of approval had some meaning... there was no value in running a NAMSA table which was proprietary to a guy named Herb Malm...and was used exclusively for Catamarans. The USA switched in about two seasons following Darline Hobocks AND US SAILINGS leadership.

The world is different. Quality and qualified data simply do not exist for portsmouth calculations. Now the only real choice is SCHRS or TEXEL.... 9tapping into the stronger EU cat scene) So, since SCHRS is sanctioned by ISAF and thus US Sailing... SCHRS is the obvious alternative. The MHC and US Sailing could move the community by putting their good housekeeping seal on US SCHRS.

The MHC could make life easy for US clubs and get certified measurements for the one design classes that did not make it to the EU.... (Isotope, Shark, CFR 20 and some others)... This would create a SCHRS table with full integrity. The good house keeping seal of approval by US Sailing will matter to clubs running handicap beach cat races... US Portmsouth is still valid for clubs racing mono's and cats in the same start. Nothing would change for the US Sailing Portsmouth system. Race data is race data... independent of what rating system is used to compute the score-sheet. ...



crac.sailregattas.com
Re: Charleston RW [Re: Mark Schneider] #271752
04/23/14 08:43 PM
04/23/14 08:43 PM
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brucat Offline
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Sounds reasonable. Make it happen...

Mike

Re: Charleston RW [Re: Mark Schneider] #271763
04/24/14 05:35 AM
04/24/14 05:35 AM
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Greenville SC
bacho Offline
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Do we have any examples of the differences we might see between the 2 systems? Does SCHRS rate an F18 faster than Portsmouth? What differences would we see?

Re: Charleston RW [Re: Mark Schneider] #271768
04/24/14 07:15 AM
04/24/14 07:15 AM
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rehmbo Offline
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http://www.schrs.com/ratings.php

There's some weirdness in there...

Edit: However, after reading the 2014 change summary, I can understand the ratings a bit better. Sounds like a valient attempt at an impossible task.

Edit #2: Check the chart at the bottom of the PDF here for relative rankings of various boats as a function of time.

Last edited by rehmbo; 04/24/14 07:52 AM.

Jeff R

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Re: Charleston RW [Re: rehmbo] #271774
04/24/14 08:43 AM
04/24/14 08:43 AM
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South Carolina
Jake Offline
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no handicap system is ever going to be perfect. Ever. With that in mind, here are how the two systems compare:

In SCHRS, F18 is the scratch boat. It's correction factor is 1 and everything else is based off it. Acat and F16 (2up) are rated the same). It's a little tough to compare them because the resulting correcting factors are a bit different.

To really compare the ratings, I've flipped around the formulas so that we are comparing them based off an elapsed time of 30 minutes for the F18...basically making it the scratch boat in both systems. I then took that corrected finished time and backed out the other boats elapsed times as if they all perfectly tied on the handicap corrected times.

Anybody step in here if I screwed this up - I didn't double check these numbers. (the code window maintains spacing in the table that would otherwise be ignored by the forum software)

Code
           Elapsed      SCHRS   Corrected
Acat       00:30:03.6   1.002   00:30:00.0
F16 (2)    00:30:03.6   1.002   00:30:00.0
F18        00:30:00.0   1       00:30:00.0
H16        00:34:21.0   1.145   00:30:00.0



Under portsmouth, again, normalized so the F18 has an actual 30 minute elapsed time and backing out the other boat's elapsed times assuming a handicapped tie, we have the following for Portsmouth/DPN. You can really ignore the value of the "corrected" times. All that matters is that the end result is a tie between the boats where the F18 ran the same length race in both scoring systems.

Code
           Elapsed      DPN     Corrected
Acat       00:31:00.8   64.5    00:48:05
F16 (2)    00:30:17.6   63      00:48:05
F18        00:30:00.2   62.4    00:48:05
H16        00:36:32.6   76      00:48:05


So, in this case, Portsmouth is considerably different on the ratings and makes it harder on the F18 (I'm biased anyway). Also notable is that the Acat and F16 (2up) are rated differently under Portsmouth but considered equal under SCHRS.

Under Portsmouth, the F18 would need to beat the F16 by 18 seconds to correct over them. SCHRS says it only needs to be 4 seconds.

Under Portsmouth, the F18 would need to beat the A-cat by right at 1 minute in a 30 minute race to correct ahead of them. Under SCHRS, it's only 4 seconds.

Under Portsmouth, the F18 would need to be 6:33 seconds ahead of the Hobie 16 to take the win. Under SCHRS, the F18 would need to be ahead by 4:21 to take the win.


In summary, SCHRS seems to rate the boats significantly closer together than Portsmouth does. Frankly, I think the existing Portsmouth numbers are closer to reality than SCHRS.


Jake Kohl
Re: Charleston RW [Re: Mark Schneider] #271777
04/24/14 09:19 AM
04/24/14 09:19 AM
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Greenville SC
bacho Offline
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Thank you Jake, that's what I was looking for. It seems we may only think the grass is greener on the other side.

I would also think the baseline boat would be better as an OD boat that has been the same for many years. What happens when the F18 gets faster? Does everyone change or does a scratch boat cease to exist?

Re: Charleston RW [Re: bacho] #271779
04/24/14 09:34 AM
04/24/14 09:34 AM
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South Carolina
Jake Offline
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Originally Posted by bacho
Thank you Jake, that's what I was looking for. It seems we may only think the grass is greener on the other side.

I would also think the baseline boat would be better as an OD boat that has been the same for many years. What happens when the F18 gets faster? Does everyone change or does a scratch boat cease to exist?


SCHRS is a measurement based system with tweaks. It is a complicated formula that predicts boat performance by physical dimensions and configurations. Technically speaking, as long as the F18 keeps the same foil type, mast type, hull dimensions, and sail area, it's SCHRS number should not change even if the sail shapes and batten technology make minor evolution changes and make the boat quicker.

The SCHRS folks have realized that there is more to it than this and they evolve their formula as things change. It's a lot of complex hard work and physically measuring boats has to happen.

The two systems are very different - Portsmouth attempts to calculate a handicap number based on actual race results. The weaknesses are that A) you have to get people to submit race results B) the software that was used to run the statistics was written in Fortran (which was brilliantly assembled but hard to run today...someone may have modernized it by now though) C) boat age and sailor skill level will affect the ratings. For instance on "C", suppose the Hobie 14 is mostly sailed by inexperienced sailors and it's rating creeps as a result. Then a skilled sailor makes a campaign on it and wins everything in sight. Is that fair?

SCHRS suffers from the rigidity of it's system and that it is somewhat uncoupled from many of the other hard to measure dynamics that make a boat fast or slow. This results in the need for complex formula tweaks to refine it.

Which one is more accurate? They're pretty different. I can't honestly say that I've ever felt like a handicap race result under DPN was unfair (although Nigel might say different from Wateree ;-). But, then again, I have a different expectation for handicap racing and don't take the result quite as seriously as I would an OD event. Overall, however, I think Portsmouth has a better opportunity to be more accurate but suffers from human nature.



Jake Kohl
Re: Charleston RW [Re: Mark Schneider] #271783
04/24/14 09:52 AM
04/24/14 09:52 AM
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brucat Offline
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Great stuff, guys. This helps a lot.

You make a great point about boats/sailors getting slower. My opinion would be to not increase a handicap based on boats getting less seaworthy and sailors getting Alzheimer's. Unless changes are made to a design/materials, or someone can prove a gross error in calculation of a number (assuming it was based on a large enough data set), I would expect the numbers to be adjusted only to deal with the boats and sailors getting faster.

Mike

Re: Charleston RW [Re: Jake] #271784
04/24/14 09:55 AM
04/24/14 09:55 AM
Joined: Jun 2001
Posts: 3,116
Annapolis, MD
Mark Schneider Offline OP
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Jake, that is a nice summary.

The only thing I would add is that the variance due to boat design is much smaller then the variance between sailing ability. See the F16 discussion.

Second point... the nature of the rules contribute to the lack of precision.
Consider... that for a 30 foot One design boat...and 10 boats in the race... a port tack boat coming into the lay line TIED for first with other perfectly sailed boats will loose three percent in time when the rules force them to bail out and fall into line in 10th place to round the mark. So... the variance will be 3% racing on time even in one design boats because of the rules.

Taking Times will not do better then 3% for 10 30 foot boats and so on.

The major advantage is transparency. Numbers don't lie... the formula is evaluated against the real world. considered by a committe for accuracy and fairness, and applied to all boat classes equally and it is published and sanctioned world wide.... you plug and chug to get your rating...

Everyone has an opinion on the accuracy of the table. If we want to average opinions... that is called PHRF and it can work... it is just not very transparent.

There is no argument that Sarah and JC turned in the rating on the Nacra 17 against joe noname who has the only A cat in the race.... So.. they have created a very hard rating to sail the N17to... The weekend sailor cant sail the boat to it's rating and compete against joe blow on the A cat...
The bar talk about the formula lasts 10 seconds.... the bar talk about Sarah and JC versus joe blow on the A cat lasts indefinitely and is meaningless.

Choose.

Last edited by Mark Schneider; 04/24/14 10:16 AM.

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Re: Charleston RW [Re: Mark Schneider] #271792
04/24/14 11:06 AM
04/24/14 11:06 AM
Joined: Nov 2011
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SE MI / NE IN
rehmbo Offline
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Another area that appears to be different are wind speed related corrections. SCHRS doesn't seem to factor this in. Realize it would be a real monster to try to simulate via mathematical calcs, but there are clearly differences in how boats behave as the wind comes up.

I guess that's a potential benefit of the empirically derived DPN system.


Jeff R

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Re: Charleston RW [Re: brucat] #271794
04/24/14 11:41 AM
04/24/14 11:41 AM
Joined: Jun 2001
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South Carolina
Jake Offline
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Originally Posted by brucat
Great stuff, guys. This helps a lot.

You make a great point about boats/sailors getting slower. My opinion would be to not increase a handicap based on boats getting less seaworthy and sailors getting Alzheimer's. Unless changes are made to a design/materials, or someone can prove a gross error in calculation of a number (assuming it was based on a large enough data set), I would expect the numbers to be adjusted only to deal with the boats and sailors getting faster.

Mike


Mike,

I was studying that very thing when I was involved. The problem is that you need the rating to have some ability to creep up so that it can settle in. If it had no ability to creep upward, random noise or one human mistake in a submitted result could really unfavorably tilt the rating and it would have no ability to correct.

Darline shared with me the original files and a theory document that explained the calculation of the DPN handicap. While I used to be fluent in Fortran at one time, the statistical part of it was pretty advanced and a bit over my head without an investment in some statistics book-learnin' on my part.

While we were examining this issue, I had considered a way that a rating can lower at a full rate but for it to correct in the higher (slower) direction would be at some reduced rate...say 25% of the rate that it could decrease. That would give it some ability to settle in and account for the outliers in the data while at least slowing down the aging fleet ratings. There were several cases of good sailors taking advantage of this rating creep at the time - but I haven't seen any of that in a long while.

all of this depends on getting submitted results and, even if we could make that happen, it's a monstrous task to get those results entered into a homogenized format that can be used for crunching.


Jake Kohl
Re: Charleston RW [Re: rehmbo] #271796
04/24/14 11:53 AM
04/24/14 11:53 AM
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Annapolis, MD
Mark Schneider Offline OP
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jeff R

Portsmouth uses wind speed ratings or DPN. DPN is 80% of the B4 rating... eg 12 to 18.

SCHRS and Texel use righting moment in the formula so it is considered. Texel did calculate two ratings... hull flying and displacement however most of the Dutch clubs did not use the two ratings because the variance of the sailors was greater then the rating difference at the club level... (basically it wasn't worth it)


crac.sailregattas.com
Re: Charleston RW [Re: Mark Schneider] #271798
04/24/14 12:06 PM
04/24/14 12:06 PM
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Naples, FL
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would accurate VPP information from the mfg. be of any help?

They would be biased to make their polars look as stellar as possible (preventing the sandbagging argument) to sell more boats.

It would provide data on point of sail and tws

Not sure how you'd crunch that into a particular platform's ideal speed/time around a course...


Jay

Re: Charleston RW [Re: Mark Schneider] #271799
04/24/14 12:07 PM
04/24/14 12:07 PM
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What we need is a way to make entering the data easier/automated...

Mike

Re: Charleston RW [Re: waterbug_wpb] #271801
04/24/14 12:12 PM
04/24/14 12:12 PM
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Boston, Ma
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Originally Posted by waterbug_wpb
would accurate VPP information from the mfg. be of any help?

They would be biased to make their polars look as stellar as possible (preventing the sandbagging argument) to sell more boats.

It would provide data on point of sail and tws

Not sure how you'd crunch that into a particular platform's ideal speed/time around a course...


I have a feeling very few small catamarans have accurate VPP data. The system is so dynamic that it would be extremely difficult to develop an accurate model that covers the different sailing modes and the transitions between them.

I have sailed a fair amount under the texel system in Singapore and Thailand and it works very well. There really hasn't been a time where I felt a boat didn't deserve the place the received.


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Re: Charleston RW [Re: Mark Schneider] #271802
04/24/14 12:15 PM
04/24/14 12:15 PM
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Greenville SC
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Do we even have that much good data to enter? What makes the data useable? I'm assuming we're taking about skilled guys racing open class with somewhat consistent results.

Re: Charleston RW [Re: brucat] #271803
04/24/14 12:16 PM
04/24/14 12:16 PM
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surely someone could figure that out along with the calendar.

What is needed to set up the electronic timekeeping thing like the runners use (those little FOBs you wear on your shoe)?

do you need to stretch an antennae across the finish line or something? That would be hard for boats (mast or daggarboards), but if it's some directional antennae (or two), it could probably work to record reasonably accurate finish times for boats which could then automatically load in whatever program (sailworks or whatever)...

If USS hosted the regatta software cloud thingy, maybe your results could be instantly available to USS?

Then the only thing would be to lodge protest hearing results ?

You PROs probably know more about the inner workings of these regatta programs...


Jay

Re: Charleston RW [Re: brucat] #271804
04/24/14 12:21 PM
04/24/14 12:21 PM
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South Carolina
Jake Offline
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Originally Posted by brucat
What we need is a way to make entering the data easier/automated...

Mike


Agreed. I had discussions with Colin Jenkins (the creator of Sailwave) and he was able and willing to include a "submit to US Sailing" option in the software. We just needed US Sailing to setup an FTP site to receive the information. It was at the time that the US Sailing website was being completely overhauled and Darline and I couldn't seem to get any attention about it... though I really wasn't screaming about it I know Darline did have some conversations to that point.

However, I think Sailwave is INCREDIBLY powerful but has gotten a little overly complex to expect everyone to use it. If you are not using it frequently it's hard to remember how to set it up correctly. I use it maybe once a year and I struggle with it until that "oh yeah, crap...that setting" moment. Setting up an Excel spreadsheet is sometimes easier. It could benefit from some streamlining of the setup process and/or having several regatta templates to choose from at the get-go. Actually, I should probably contact Colin about that to see if he hasn't already thought of that.


Jake Kohl
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