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Where can I find the Portsmouth modifiers? #250724
07/12/12 07:30 AM
07/12/12 07:30 AM
Joined: Aug 2011
Posts: 774
Greenville SC
bacho Offline OP
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bacho  Offline OP
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Greenville SC
I am making a few modifications to my boat and considering a few more. I would like to work up the rating hits, but I cannot find an official list of them. Google just brings up a bunch of dead links. Maybe my search skills suck though.

Ps, in an open class do I need to take a hit for non factory sails as well as a hit for a different area?

Last edited by bacho; 07/12/12 07:35 AM.
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Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250725
07/12/12 07:52 AM
07/12/12 07:52 AM
Joined: Jun 2001
Posts: 3,906
Clermont, FL, USA
David Ingram Offline
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David Ingram  Offline
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It's not the most intuitive navigation: www.ussailing.org -> offshore -> Portsmouth_Yardstick -> Portsmouth Yardstick Index -> Current Tables -> MH Modification Factors

MH Modifiers

To answer your question you take the MN hit "For non-class legal mainsail, of same sail area or less than class legal mainsail (formerly square top adjustment)".


David Ingram
F18 USA 242
http://www.solarwind.solar

"Do or do not. There is no try." - Yoda
"Excuses are the tools of the weak and incompetent" - Two sista's I overheard in the hall
"You don't have to be a brain surgeon to be a complete idiot, but it helps"
Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250732
07/12/12 11:41 AM
07/12/12 11:41 AM
Joined: Jul 2004
Posts: 125
Clinton, Mississippi
rattlenhum Offline
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rattlenhum  Offline
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Clinton, Mississippi
Originally Posted by bacho
Ps, in an open class do I need to take a hit for non factory sails as well as a hit for a different area?


Depends on what boat you're on. The underlying principal is that you follow class rules or take the appropriate modification. Some classes don't require "factory" sails to be class legal like Hobie does. If your sails are class legal with same sail area, there's no hit. If your sails are not class legal, use MN for same sail area or ML for greater sail area.


Jerome Vaughan
Hobie 16
Clinton, Mississippi
Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250738
07/12/12 01:51 PM
07/12/12 01:51 PM
Joined: Aug 2011
Posts: 774
Greenville SC
bacho Offline OP
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bacho  Offline OP
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Greenville SC
So, my boats (nacra 20) current rating is only valid as a one design?

If I wanted to change the area of all 3 sails and add beam, would it make for sense to have it measured and rated texel or SCHS(spelling) for the long run instead of basing off of a design that is very different from what it is today?

Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250740
07/12/12 02:10 PM
07/12/12 02:10 PM
Joined: Jun 2001
Posts: 3,906
Clermont, FL, USA
David Ingram Offline
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David Ingram  Offline
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Clermont, FL, USA
Originally Posted by bacho
So, my boats (nacra 20) current rating is only valid as a one design?

If I wanted to change the area of all 3 sails and add beam, would it make for sense to have it measured and rated texel or SCHS(spelling) for the long run instead of basing off of a design that is very different from what it is today?


The short answer is no. I've only seen one race in the US use SCHRS and that was the Tybee 500. Mark S may use Texel in the NE but for the most part nobody uses either system in the US so your measurement cert wouldn't do anything for you.

Personally I think you'd have a ratings beater if you just took all the modifiers applicable in DPN. If there is a weekness/loophole in DPN it's in the modifiers which is the appeal of a frankenboat.


David Ingram
F18 USA 242
http://www.solarwind.solar

"Do or do not. There is no try." - Yoda
"Excuses are the tools of the weak and incompetent" - Two sista's I overheard in the hall
"You don't have to be a brain surgeon to be a complete idiot, but it helps"
Re: Where can I find the Portsmouth modifiers? [Re: David Ingram] #250741
07/12/12 03:00 PM
07/12/12 03:00 PM
Joined: Dec 2001
Posts: 5,590
Naples, FL
waterbug_wpb Offline
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cool! a Franken 20!

How wide are you going on the beam?

How much more sail area you going for?


Jay

Re: Where can I find the Portsmouth modifiers? [Re: David Ingram] #250743
07/12/12 03:14 PM
07/12/12 03:14 PM
Joined: Jun 2001
Posts: 3,116
Annapolis, MD
Mark Schneider Offline
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Mark Schneider  Offline
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Annapolis, MD
We have switched in the mid atlantic to SCHRS.... the ISAF measurement system.

I believe the Great Texas also uses SCHRS. The advantage is that it gets rid of the politics in PHRF/Portsmouth.

The OA decides what handicap rating fleet they will offer. If your area jumps to SCHRS... your franken boat would be run through the same rating formula as the stock Nacra 20. Very straightforward... no politics.



crac.sailregattas.com
Re: Where can I find the Portsmouth modifiers? [Re: waterbug_wpb] #250745
07/12/12 03:48 PM
07/12/12 03:48 PM
Joined: Aug 2011
Posts: 774
Greenville SC
bacho Offline OP
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bacho  Offline OP
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Originally Posted by waterbug_wpb
cool! a Franken 20!

How wide are you going on the beam?

How much more sail area you going for?


Well I am not sure how much I will do, I am still exploring options. At first I was looking at the Open 20 rules but now I have decided against them. I was talking with Randy Smyth about the open 20 and we (I mean he) came up with a sail plan for it. After deciding against the Open 20 we decided that the sails proposed for that class would still be a good choice and he did not see a good reason to go bigger. So my new sails will be a 214sq ft main and a 53sq ft square top jib. So 24sq upwind.

I decided I wanted to try those out before deciding on how much spin area to go with. I think I would like to have at least 2 separate spin sizes.

Beam, again not sure. It depends what options I can come up with for beams. If performance will sell me bare extrusions at a reasonable price, I think I would shoot for 10.5'. If they wont, it will be up to finding some used beams to splice which does not excite me. Carbon beams are not gonna happen.

I want to explore all (if any) options with ratings, because I want to do this mostly just for fun. I love to tinker with things that are good enough left alone, but I want to keep it fair rating wise on both sides.

Re: Where can I find the Portsmouth modifiers? [Re: Mark Schneider] #250746
07/12/12 03:49 PM
07/12/12 03:49 PM
Joined: Jun 2001
Posts: 3,906
Clermont, FL, USA
David Ingram Offline
Carpal Tunnel
David Ingram  Offline
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Clermont, FL, USA
GT 300 was DPN according to the NOR.



David Ingram
F18 USA 242
http://www.solarwind.solar

"Do or do not. There is no try." - Yoda
"Excuses are the tools of the weak and incompetent" - Two sista's I overheard in the hall
"You don't have to be a brain surgeon to be a complete idiot, but it helps"
Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250747
07/12/12 04:28 PM
07/12/12 04:28 PM
Joined: Sep 2002
Posts: 3,222
Roanoke Island ,N.C.
Team_Cat_Fever Offline
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Team_Cat_Fever  Offline
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I was thinking of doing all of that stuff, plus curved boards, but couldn't justify the expense. The boards would be your biggest improvement with no handicap that I can find. Pricey but probably worth it. The N-20 always suffered from the fat hull and how quickly it got that way, the curved boards would help get that out of the water. I think your handicap would be 57.5 with the stuff you're talking about doing.


"I said, now, I said ,pay attention boy!"

The cure for anything is salt water - sweat, tears, or the sea
Isak Dinesen
If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most.
E. B. White
Re: Where can I find the Portsmouth modifiers? [Re: Team_Cat_Fever] #250748
07/12/12 04:53 PM
07/12/12 04:53 PM
Joined: Jun 2001
Posts: 162
Dunedin Causeway, FL
hobiephil Offline
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hobiephil  Offline
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Dunedin Causeway, FL
Originally Posted by Team_Cat_Fever
The boards would be your biggest improvement with no handicap that I can find.


MH Modification Factors
OTHER: Any other deviations from standard class configurations, including the addition of wings, can be assessed a penalty of AT LEAST 0.995. Multiple deviations may incur multiple penalties. Penalties may be greater than 0.995

Last edited by hobiephil; 07/12/12 04:56 PM.
Re: Where can I find the Portsmouth modifiers? [Re: hobiephil] #250751
07/12/12 06:00 PM
07/12/12 06:00 PM
Joined: Sep 2002
Posts: 3,222
Roanoke Island ,N.C.
Team_Cat_Fever Offline
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Team_Cat_Fever  Offline
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Roanoke Island ,N.C.
Originally Posted by hobiephil
Originally Posted by Team_Cat_Fever
The boards would be your biggest improvement with no handicap that I can find.


MH Modification Factors
OTHER: Any other deviations from standard class configurations, including the addition of wings, can be assessed a penalty of AT LEAST 0.995. Multiple deviations may incur multiple penalties. Penalties may be greater than 0.995


Then the PN would be 56.9 with wide beams, big main, big jib, different spin (non E/P) and curved boards. Slightly slower (.4) than an RC-27.


"I said, now, I said ,pay attention boy!"

The cure for anything is salt water - sweat, tears, or the sea
Isak Dinesen
If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most.
E. B. White
Re: Where can I find the Portsmouth modifiers? [Re: Team_Cat_Fever] #250753
07/12/12 07:44 PM
07/12/12 07:44 PM
Joined: Aug 2011
Posts: 774
Greenville SC
bacho Offline OP
old hand
bacho  Offline OP
old hand

Joined: Aug 2011
Posts: 774
Greenville SC
Originally Posted by Team_Cat_Fever
I was thinking of doing all of that stuff, plus curved boards, but couldn't justify the expense. The boards would be your biggest improvement with no handicap that I can find. Pricey but probably worth it. The N-20 always suffered from the fat hull and how quickly it got that way, the curved boards would help get that out of the water. I think your handicap would be 57.5 with the stuff you're talking about doing.



Did you ever get a price from anyone on building some curved trunks? Just curious, not something I want to do.

Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250754
07/12/12 08:12 PM
07/12/12 08:12 PM
Joined: Sep 2002
Posts: 3,222
Roanoke Island ,N.C.
Team_Cat_Fever Offline
Carpal Tunnel
Team_Cat_Fever  Offline
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Joined: Sep 2002
Posts: 3,222
Roanoke Island ,N.C.
Trunks are easy, the boards are alot of work. F-20c or M-20(would probably come with the trunks) boards would be the easiest and most affordable, still pricey though.For the trunk you just pack the board out a bit, release film, then carbon over your pack. Slide it off the board and you've got a trunk.


"I said, now, I said ,pay attention boy!"

The cure for anything is salt water - sweat, tears, or the sea
Isak Dinesen
If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most.
E. B. White
Re: Where can I find the Portsmouth modifiers? [Re: Team_Cat_Fever] #250764
07/13/12 07:45 AM
07/13/12 07:45 AM
Joined: Aug 2011
Posts: 774
Greenville SC
bacho Offline OP
old hand
bacho  Offline OP
old hand

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Greenville SC
I think if I was to do anything like that, I would try canted or L boards. I have a couple extra boards that I have considered experimenting with

Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250767
07/13/12 08:25 AM
07/13/12 08:25 AM
Joined: Dec 2001
Posts: 5,590
Naples, FL
waterbug_wpb Offline
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waterbug_wpb  Offline
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Naples, FL
a 10.5' width on a 20' boat would make it pitchpole before heel over?

For some reason, I seem to think a boat wider than 1/2 of the LWL has some issue? Maybe some of you designers could chime in here?


Jay

Re: Where can I find the Portsmouth modifiers? [Re: waterbug_wpb] #250770
07/13/12 09:30 AM
07/13/12 09:30 AM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
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Jake  Offline
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Posts: 12,310
South Carolina
Originally Posted by waterbug_wpb
a 10.5' width on a 20' boat would make it pitchpole before heel over?

For some reason, I seem to think a boat wider than 1/2 of the LWL has some issue? Maybe some of you designers could chime in here?


There is a point where the additional bow pressure that results from extra righting moment due to the width starts to become a concern....like on the wide supercats (11' x 20'). The additional width gives it better speed potential but it makes them more sensitive to proper downwind handling...and more sensitive to sailing downwind in waves. However, you can control that by being wise with how much leverage you put on the bows...if you're in danger of stuffing it with the kite up, get your crew off the wire and start moving your weight inboard = problem solved. The trick is identifying that you need to do this BEFORE the boat takes you all the way to the scene of the crash. There really is not much concern with this change in the upwind attitude of the boat.

The 20 (at 8.5' wide) is one of the best ocean sailing cats I've ever been on. It will flat out eat waves and wind and you can sail with the confidence that as long as you can keep your weight rearward, the boat will not pitchpole (unless you're out in some REALLY crazy stuff). I think it would live and perform well at 10 or 10.5 feet but it's going to be less wave resistant.

Oh, and BTW, I've got a spare rear beam (standard width) from a 20 that I don't need.


Jake Kohl
Re: Where can I find the Portsmouth modifiers? [Re: Jake] #250771
07/13/12 10:03 AM
07/13/12 10:03 AM
Joined: Aug 2011
Posts: 774
Greenville SC
bacho Offline OP
old hand
bacho  Offline OP
old hand

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Posts: 774
Greenville SC
Thanks Jake, I was mostly considering upwind and did not consider downwind effects as hard.

I can see the difference in waves, that said unfortunately for now most of my sailing is on the lakes locally.

Re: Where can I find the Portsmouth modifiers? [Re: bacho] #250778
07/13/12 11:25 AM
07/13/12 11:25 AM

M
MN3
Unregistered
MN3
Unregistered
M



seems like a too much work to me (impo)

I would rather just sail it till I break it (or it breaks me), then get another smile

Re: Where can I find the Portsmouth modifiers? [Re: Jake] #250782
07/13/12 12:13 PM
07/13/12 12:13 PM
Joined: Jan 2007
Posts: 139
Hernando, Florida
M
Mlcreek Offline
member
Mlcreek  Offline
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M

Joined: Jan 2007
Posts: 139
Hernando, Florida
However, you can control that by being wise with how much leverage you put on the bows...if you're in danger of stuffing it with the kite up, get your crew off the wire and start moving your weight inboard = problem solved. The trick is identifying that you need to do this BEFORE the boat takes you all the way to the scene of the crash.

Jake, coming off of the wire and moving inboard is best to prevent pitch pole? Aren't you taking the cantilever action of your weight off the hull, and loosing the counter balance effect by doing this? Please explain the principle.

Thanks

Forrest
I-20

Last edited by Mlcreek; 07/13/12 12:30 PM.

Forrest
I-20
USA 645

" There ain't enough rum in the drum!"
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