One foil

[Quoddy]

We are going windward without a traveler or easily movable jib block.

If you look at the main and the jib (110) as “one foil” then I expect they should have the same twist. Let’s say they do and it is right for the conditions. If you change course away from the wind you must ease the jib which increases twist. If you ease the main the same amount and are vang sheeting then the twists of the two sails will no longer be compatible.

The question is which is better. Maintain the right twist in the main with the vang or let the boom rise so the main matches the jib?

 

[FourPoints]

Interresting question... I would think maintaining the shape of the main (espicailly if it's a fractional rig with a relativly small headsail / large main) for optimal power would be better than deforming the main to match the deformed genoa. The question of impact of the slot effect comes in then, and does the gain from maintaining the best possible slot outweigh the loss of power from the main not being optimally shaped. I think the answer would be no.

I say maintain the correct shape of the main and do your best with the genoa (maybe get creative with a barberhauler placed fore or aft instead of windward to compensate for the lack of track?), but Don may tell us otherwise.

 

[Don Guillette]

Quoddy: I know how I want to answer your question but I'm not sure I can put it into written words - RichH, Alan, StuJ and Joe from San Diego are better at some of these technical questions than I am. There are a number of questions hidden in what appears to be only one question.

Picture that your boat has a wooden dowel coming up through the keel that the boat can pivot on. Say your closehauled and your main and jib are set for 100% efficiency. Now you change course to between closehauled and beam reach. The wind hasn't change direction - your boat has (it pivoted) - and the sails don't know the difference in the point of sail. My BOARD OF EXPERTS will fill in the blanks that I probably left open.

On the 110 jib, which is a very small jib, I assume you have a fractional rig. The engine of your boat is the main and the small jib has little effect on your performance so your ability to adjust it is not that important. You really have to concentrate on your main from a sail trim standpoint. It appears you have a boom vang - crank on that to take out the twist and then see if you can match (mirror) the jib to the main. The sail trim control for TWIST on the jib is the fairleads. The fairleads are also used to adjust ANGLE OF ATTACK abd DRAFT POSITION. The fairleads and JIB SHEET are used to adjust DRAFT DEPTH. As you can see the fairleads are used to adjust ALL of the FOUR ELEMENTS OF SAIL TRIM and therefore are a very important sail trim control for the jib. Probably 60% of sailors don't even use them. So, when you ease your jib sheet, you're not increasing twist - your increasing your draft depth.

 

[Don Guillette]

Mates: Please notice I said "mirror the jib to the main". Here's what I mean by that. They both have to mirror each other but it more of who's looking at who in the mirror. For fractional rigs you're adjusting the main FIRSTand next the jib. For a masthead rig, you want to do the opposite - adjust the jib FIRST and then have the main mirror the jib. I almost confused myself!!!

Next time you're on the water, take a look at the boats around you and check out how many sails mirror each other. If your boat isn't in the water yet, pick up any sailing mag and check out the adv pictures and see how may sails mirror each other - you'll find not many do as crappy sail shape makes for better pictures in 85% of the adv. I don't know why that is.

 

[Bill Roosa]

that is why you want to have a travler BTW.
So how are you controling the boom angle and height?

 

[Joe]

We are going windward without a traveler or easily movable jib block.

If you look at the main and the jib (110) as “one foil” then I expect they should have the same twist. Let’s say they do and it is right for the conditions. If you change course away from the wind you must ease the jib which increases twist. If you ease the main the same amount and are vang sheeting then the twists of the two sails will no longer be compatible.

The question is which is better. Maintain the right twist in the main with the vang or let the boom rise so the main matches the jib?

I think your error is in the assumption that easing the jib sheet tension changest the twist of the head sail.... that is not the case... the jib lead position controls the twist by distributing the jib sheet tension between foot and leech. Move the lead forward, more leech tension, less twist. Move it backward, less leech tension, more twist.

To answer your question: Watch your tell tales.... let them tell you what to do.

 

[Ted]

There are too many unknowns here to make accurate trim suggestions. Wind speed, sea state, helm balance and wind shear will also influence your sail setup. Always go back to your knot meter and see if the sail trim change that you made positively influenced boat speed. Sometimes what looks like poor sail trim can actually be fast. Make small adjustments and wait a minute to see the true results before making another adjustment.

 

[RichH]

If you change course away from the wind you must ease the jib which increases twist.
The question is which is better. Maintain the right twist in the main with the vang or let the boom rise so the main matches the jib?

Neither !!!!!
If you have tell tales .... you move the fairlead car forward so that the jib tales are restored to 'perfection' ... and then readjust / fine tune the 'set' & shape of each sail so that ALL the tell tales are again 'perfectly flowing'.

 

[FourPoints]

Neither !!!!!j
If you have tell tales .... you move the fairlead car forward so that the jib tales are restored to 'perfection' ... and then readjust / fine tune the 'set' & shape of each sail so that ALL the tell tales are again 'perfectly flowing'.

You're not wrong, but the OP said he cannot or isn't willing to move the fairlead cars, So he is asking what is the lessor of two evils here...

 

[Don Guillette]

I could have answered his question simply by saying that he should maintain the right twist in the mainsail and forget the jib but this forum is for beginners to intermediates and many times they don't know what they are really asking and since I've heard about every sail trim question anyone could ask (some questions over a million times) I go into a bit more detail. Quoddy is not a beginner and I didn't want my answer to be something beginners would pick up on and run with because the lesser of two evils in this case is not the way to go.

 

[Todd Smith]

... I didn't want my answer to be something beginners would pick up on and run with because the lesser of two evils in this case is not the way to go.

They should go with the greater of two evils ?