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Ilenart 08-03-2009 12:58 AM

Question on Polar Diagrams
 
Currently sitting in hospital with plenty of spare time so have been reviewing a fair bit of yachting info. One thing I have is a polar diagram that I am trying to compare to my current boat and one thing I was wondering is how do they account for sea state? It is showing an optimum apparent wind angle of 32 degrees in 26 knots of wind. However 26 knots would normally throw up a fair bit of chop, which most boats would need to ease off a bit to make decent progress.

Any one have any ideas? I was thinking they probably assume flat water, which means in real life / choppy conditions you would need to add around 5 degrees to compare to a real life scenario.

Ilenart

JohnRPollard 08-03-2009 08:57 AM

You've hit on it. The polar diagrams do not account for sea-state. They are theoretical, not real world.

But I still find they are helpful for comparing the relative speed potential of different designs.

P.S. I hope it's not too serious and that you're back on the water soon. Cheers.:)

blt2ski 08-03-2009 09:00 AM

As I understand polars, they are saying that the speed on the curve, is the best you will do in those winds. They are not saying that you can always go at the high of a point sailing. So if I understand what you are asking, yes, sometimes you can not point as high, nor want to because of sea state.

I have seen polars with different sea state comparisons too. Then there will even be different rig configs depending upon sea state also. IE, a full main and 110 vs a single reef and 155 for the same wind condition, one being better in 3' chop, the other in 1' waves. Or as I saw once for the V70 follks 40-45knots of wind vs how high the waves were, they had 3 or 4 sail opions, from single to triple reefs with varying jib sizes.

Marty

JohnRPollard 08-03-2009 09:12 AM

Quote:

Originally Posted by blt2ski (Post 510637)
As I understand polars, they are saying that the speed on the curve, is the best you will do in those winds. They are not saying that you can always go at the high of a point sailing. So if I understand what you are asking, yes, sometimes you can not point as high, nor want to because of sea state.

I have seen polars with different sea state comparisons too. Then there will even be different rig configs depending upon sea state also. IE, a full main and 110 vs a single reef and 155 for the same wind condition, one being better in 3' chop, the other in 1' waves. Or as I saw once for the V70 follks 40-45knots of wind vs how high the waves were, they had 3 or 4 sail opions, from single to triple reefs with varying jib sizes.

Marty


Marty,

Thanks for that follow-up. I've never seen those polars with the different sea-states factored. It makes sense and would make them much more useful.

As it is, it's difficult enough to find ANY polar diagrams for older designs. But they seem to be more readily available for many of the newer designs. Where did you find the V70 polars? They would be interesting to peruse.

Ilenart 08-05-2009 01:47 AM

Thanks for the advice guys.

Ilenart

blt2ski 08-05-2009 02:01 AM

John,

The V70 stuff was actually an article in Sailing World a couple of years back during that race. IIRC it was the Disney boat that they were interviewing etc with the what sails were up for different sea types. Finding polars for different sea types is difficult at best, even for new boats. A lot of times you need to take the polars given, and then "YOU" work with them to figure out how to acheive the results. In that manner, you figure out which sail combo's to use for different conditions. And for that manner, if you really want to point as high as you can go, vs going 3-5 degrees off, and gaining a half knot of speed, so even tho you go further to your destination, you get there faster because of the increase in speed, IE now we are into Velocity made good or some such thing.

I know enough to get me in trouble on this, but not quite enough to get out of it. As they say, I am still learning and trying to figure it all out myself. BUT< I noticed last spring, a couple of times my boat does better with the same SA up with a double reef and my carbon 155 than a full main and 110! As they say, play with sail combo's, what you might think is best, may not be!

Marty

georgesoilis 04-15-2012 01:04 PM

Re: Question on Polar Diagrams
 
Quote:

Originally Posted by JohnRPollard (Post 510642)
Marty,

.........

As it is, it's difficult enough to find ANY polar diagrams for older designs..

This is for CREALOCK 34 if its of any use for you....:):)


TWA 6 8 10 12 14 16 20
52 4.4 5.3 5.8 6.0 6.2 6.3 6.4
60 4.7 5.6 6.1 6.3 6.4 6.5 6.6
75 5.0 5.9 6.3 6.6 6.8 6.9 7.0
90 5.3 6.1 6.5 6.7 6.9 7.0 7.3
110 5.2 6.1 6.5 6.9 7.1 7.3 7.6
120 4.9 5.9 6.4 6.8 7.1 7.4 7.8
135 4.4 5.4 6.1 6.5 6.9 7.2 7.8
150 3.7 4.6 5.5 6.1 6.5 6.9 7.5


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