Sail Trim - What did I do wrong?

[rpwillia]

All, In a race about a month ago I did really well. But on one upwind leg I squandered a big lead. We had about 10-20 knots of wind all day with a 1-2 foot of chop. I recall we tweaked the traveler and the rigid boom vang a little; this resulted in the helm being very hard to steer until it over corrected and then I had to fight it back into trim and hard to steer again. On the final leg after a downwind run we simply just set the traveler to amidships and let out the mainsheet just a little and the boat just absolutely rocked (to the point I gained and passed a boat that had caught up to me on the previous upwind run. Attached is a picture of us on the upwind run - my boat is the C310 on the right.

 

[Peggie Hall HeadMistress]

A better place to ask--IF you can find it! (Phil, please read?)

If you look under forums...and then under "shared forums"...and THEN under "expert forums"... you'll FINALLY find the Sail Trim forum!

(Phil, it's wonderful to have the expert forums linked to the shared forums again, but there's GOTTA be an easier way! 'Cuz ain't nobody who doesn't already know where they are gonna dig that deep find 'em...that thought won't even occur to anybody!)

 

[ITMaster]

I'm not the person to give you advice on sail trim.

I am the person to give you advice to spend the money on Don Guillette's book on sail trim available here at this site. It will be one of the most economical investments you can make toward providing you with an abundant wealth on knowledge about sail trim.

It is easy reading and something for you to have with you to read, look at the conditions, evaluate, then follow the advice in the book for the conditions. I have had the book for going on 3 years, and I continue to read it, evaluate the conditions, and then apply the concepts.

I can't recommend that book enough to anyone having any questions about sail trim. You will be very pleased with the small token of money you will spend on it and you get to use it over and over and ...

 

[LANCE ON CLOUD NINE]

read all old trim posts by RichH

I have learned a ton from him. And I'll bet twenty he gets back to you SOON!

 

[Ross]

Re: read all old trim posts by RichH

RichH has been conspicuously absent lately. It is too early for skiing and rather later for sailing from Warton Creek. I have wondered where he is.

 

[RichH]

" I recall we tweaked the traveler and the rigid boom vang a little; this resulted in the helm being very hard to steer until it over corrected and then I had to fight it back into trim and hard to steer again. "

I took your thumbnail and pasted it into a graphics program. This is what I seem to be seeing: I took a straight (red) line and overlayed it onto the leading edge of your forestay/genoa luff .... and your forestay seems to be sagged well to leeward (probably by 18" from the below posted pic). Its somewhat hard to tell from a picture but it 'appears' this is whats going on and gave you the problems in 'pointing'. This 'sag' will cause the helm symptoms you describe (plus the boat will heel excessively and without much speed) ... and if this is the case, then no amount of 'sail trim' will correct this.

Two things cause such sag:
1. not enough backstay tension. The genoa Luff on a 310 is ~42 ft. and the 'sag' for a fully loaded head sail would be about 6" for a properly tensioned backstay ... from the your thumbnail, I can approximate nearly 18" of sag.

2. overzealous tension on the genoa winch. Over-tensioning the sheet of a big genoa can increase the forestay sag and yield the same adverse effect of too much sag. A big luff genoa is easy to overtension with a big winch ... so if you overtension, then you 'must' also increase backstay tension to compensate.

Since you 'romped' going downwind where a slack forestay (released tension on the backstay) will be an advantage .... my 'best guess' is that you didnt have enough forestay tension upwind and proper tension going down. If you race often a backstay tensioner is a 'must'. Unless the rig tension is 'near perfect', sail trim wont gain you very much when it comes to headsail shape.
If we were 'match racing' and I so observed your slack forestay, I'd be sure to get you into a tacking duel to take advantage of the slack forestay ;-)

If you want an opinion of 'exactly' how much backstay tension to apply for bombproof-PERFECT jib/genoa leading edge shape ... drop me an email at RhmpL33ATattDOTnet.

 

[RichH]

Re: read all old trim posts by RichH

Hi Ross
Been hiding from all the gales marching up along the SE coast ... . Hatteras has been generating LOT of 'junk weather' lately.

 

[Peggie Hall HeadMistress]

That's better!

Thanks Phil!:dance:

 

[Ross]

Hi Ross
Been hiding from all the gales marching up along the SE coast ... . Hatteras has been generating LOT of 'junk weather' lately.

RichcH, Glad to know that you are still alive and kicking. I was beginning to wonder if you had sailed too close to the edge. Several of my friends have come close this fall and I am starting to get edgey.

 

[Ross]

Phil, Are we getting too compartmentilized here? I think that some form of cross referencing is going to be needed before we become several forums. Ask all sailors should be comprehensive. I don't spend my time wandering from specialist to specialist here but I value the words of wisdom from all of our experts. Was the change their choice or yours?

 

[sailingdog]

Ross-

I think they moved this from Ask All Sailors to the Ask Don Sail Trim forum, since it is clearly a sail trim related question. I think it makes sense to put all the "expert" topic posts under the proper forums... since most are probably going to go to the expert forums when looking for answers in those topics. I know if I had a Head-related question, I'd want Peggie's input on it.... and if I had a sail trim question, I'd want Don's feedback and advice on it.

 

[Don Guillette]

RPwillia: Nice picture. Actually, your sails and heel look pretty good. Lets talk about what you said you did. First, 10 to 20 knots is a big range of wind. That range could involve 3 different settings. Lets assume it was 15 knots.

Tweeked the traveler: I assume you pulled it closer to the center line. The traveler ONLY controls angle of attack. By moving the traveler toward the centerline you powered up the boat. If you eased it down you lost power.

Tweeked the boom vang: If you cranked on the boom vang you adjusted 2 things. The first thing you did was reduce twist which added power. The second thing you did was move the draft position forward. As the wind increased in speed it pushes the DP aft, which slows the boat. If you move the DP forward (around 50%) it speeds up the boat. You don't want the DP to be more than 55%, especially if you want to win races.

Let out the mainsheet: By doing that you reduced the angle of attack, you increased twist and you moved the DP aft - all speed killers.

You left out one very important sail and that is the jib. On a masthead rig the engine in the jib. If you have a perfectly shaped mainsail and a crappy shapped jib your losing speed.

L

 

[Don Guillette]

I forgot to mention one other item and that is crew position. In 15 knots of wind they should be windward/forward.

Obviously, your serious about your sailing. Here's my guarantee on my SAIL TRIM CHART - if you use my setting and you don't move up 3 positions I'll refund your money and you can keep the chart!!