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post #1 of 10 Old 05-07-2009 Thread Starter
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Genny too big?

I am racing on a 1970s era 27' fin keeled plastic fantastic (not going to say more to protect the guilty).

Skipper insists on flying a 170% upwind. I say it's killing us because it can't be properly trimmed. I don't think we point as high (stats seem to suggest I'm right) and I think the 170 outpoints the main, leaving the main to luff slightly when it should be drawing upwind, so my theory is it's killing boat speed too.

Oh, and by the way, we're taking a 12 point hit on the PHRF rating for even having this behemouth aboard.

Any thoughts, suggestions, would be appreciated.
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post #2 of 10 Old 05-07-2009
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It certainly sounds like you have a valid point. I'm sure on a reach, it pushes the boat nicely. Is the helm relatively neutral or is there a lot of weather helm. If it's nearly neutral, than the sail(s) are probably "blown out" with that much sail forward. I have a late 60's CCA boat that balances beautifully with a 110. We pretty much leave the 150 below unless we're racing.

Moe
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post #3 of 10 Old 05-07-2009
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You definitely will not point as high with a poorly trimmed genoa and the 170 is a ridiculously large foresail for a 27' boat.

You're not going to get the shape out of a 170 that you would out of, say, a 150, or better yet, something smaller.

My guess is its meant as a "drifter" for light winds, and then basically on a reach to a run.

I don't know about it outpointing the main, but if it's trimmed too tightly, it's probably backwinding the main.
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post #4 of 10 Old 05-07-2009
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The main driving force is mainly from the genova. The wind is deflected by the genova and the main cannot generate a good dirive. Its main function is to keep the boat on course. The ise of the genova does not matter to much to deflect the wind. Even you use 100% genova the wind will be blowing nearly from the head of the boat when you consider the main sail. It is a good idea to keep the genova area maximum if you can trim it correctly. Do not worry about the main, it will not generate enough drive.
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post #5 of 10 Old 05-07-2009
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See if you can get him to switch to a 135% or so...and see how you do in the races. If you do the same or better, your point will have been made.




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post #6 of 10 Old 05-07-2009
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A 170 genoa is intended for light winds only, and will be severely stretched out if its wind range is exceeded, hurting performance as you believe.

A 153% genoa will incur no rating penalty... maxing out at 135 will give you a rating credit.. either move will likely result in improved results on the score sheet - and likely on the water as well.

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post #7 of 10 Old 05-07-2009
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Quote:
Originally Posted by sneuman View Post
....
Skipper insists on flying a 170% upwind. I say it's killing us because it can't be properly trimmed. I don't think we point as high (stats seem to suggest I'm right) and I think the 170 outpoints the main, leaving the main to luff slightly when it should be drawing upwind, so my theory is it's killing boat speed too.
.....
The 170% genoa has pretty much disappeared from racing boats, I guess most racers have calculated that the extra 20% area is not worth the typical 6 seconds penalty received for inventorying such a sail. (That said, ANY serious race boat inventory other than one designs with limited foresails, works with one or more 150% genoas as primary sails and carry the 150% long after most cruisers would have reduced the foresail size....).

Assuming the wisdom of the general race population, I'd drop the 170% unless
1. It's in good condition
2. you don't have a 150% in better or similar condition
3. you sail in a generally light air venue.

A 170% will earns its points versus a 150% in less than 6-7 knots, there is no reason it should not point as well as a 150%, if in similar condition and if you have the track length for it to trim inboard. As with any sail with a large overlap, you are likely to backwind the main in the genoa's upper wind strength range...that is OK, it's still fast. Your comment about "outpointing the main..." doesn't make much sense, I gotta suggest you might want to see if you can get a second opinion onboard to work through the relationships of the genoa and main and related trimming.

Certified...in several regards...

Last edited by sailingfool; 05-07-2009 at 10:16 AM.
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post #8 of 10 Old 05-07-2009
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Hellllooooo Neuman (from Seinfeld),

Man, for a second there I thought you were one of my crew harshing me for flying the 170 on my C27. Then I saw you were in Thailand. Whew.

You're right though. That thing's a pig.

And it's good to hear from these other sailors on what the best sail is. Nice.
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post #9 of 10 Old 06-01-2009
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I'd hate to be the guy grinding in a 170 on my boat with a masthead rig and displacing 24,000 lbs (not counting the not-so-light crew). I would think that a 170 would have an extremely limited application and should not be the every day (or every race) jib.
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post #10 of 10 Old 06-23-2009
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With 170s ... one has to ask the questions:
If the 170s is so efficient, then even with the ratings penalty do you not see more flown? ... intuitively obvious answer: inefficient overall

170s are from a bygone day when it was erroneously assumed that DDW was somehow faster and pointing ability was somehow enhanced by more sail area, etc., especially in 'light winds' ----
1. Wind strength at most 170% conditions does not usually have sufficient energy for the airstream boundary layers to remain 'attached' ... for the full cord of the sail ... and with such a sail being soooo sensitive to such boundary layer conditions, easily develops separation stalls aft of mid-cord and towards the leech sections. A full set of telltales and a row of 'gentry tufts' will usually validate this stability/instability.
2. A 170 designed/plotted for typical 'light wind sailing' will have lots of 'shoulder' - fullness in the upper sections of the sail for more 'power' but that comes with less pointing ability. Most 170s cut 'back then' were cut with the mistaken idea that you needed a larger draft (powered up) sail for 'light condition' --- entirely wrong due to the propensity of separation stalls. "powered up" sail are not FAST sails.
3. Its easy to be overpowered using a 170 and that will create more leeway/skid that drastically reduces VMG .... "going like hell but in the wrong direction (for pointing)". Plus, a (especially light weight) 170 can easily have its luff distorted by energetic/aggressive winch pressure / windloading ... and the luff hollow (entry portion of the luff) no longer matches the normal sag in the forestay/headstay .... the result is more heel, skid to leeward, ... drastically falling VMG.
4. Unless your class rules allow a reaching strut (most dont), a BIG LP sail wont have very good shape when reaching due to the undue twist that develops because .... you simply cant move the fairleads out beyond the rail of the boat.

Every boat is different and every trimmers' perceptions are different so I would suggest


Suggest that you perform some comparative 'plots' of VMG vs. 'normal windspeeds when the 170 is flown ... between the smaller genoas and the 170. Careful 'profiling' (based on a quantity of collected data points under varying conditons) of the performance of each (vs. VMG) may validate that the 170 ... just isnt worth it (ratings penalty) vs. VMG. Use FULL set of tell tales with 'gentry tufts' to set/shape each sail to perfection, then do the comparisons.
Look to 'nature' (who seemed to have this figured out millions of years ago) that the best 'gliders' are the birds that have VERY high aspect ratio wings and look to the sails being used on the modern high end boats ... high aspect ratio to the hilt. Increasing the LP% reduces AR.

BTW - The comment about mainsails being 'just steering components' ... sorry that is entirely wrong wrong wrong as the mainsail is definitely part of the 'system' and helps create the 'upwash' etc. in which the jib/'genoa operate. If the mainsail isnt trimmed to perfection you will NEVER be able to perfectly optimize/trim/set a genoa on an aerodynamic basis.

Last edited by RichH; 06-24-2009 at 08:20 PM.
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