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Author Topic: Sail spacing  (Read 1892 times)

Catalina

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Sail spacing
« on: January 24, 2007, 12:45:48 PM »

Hello all.
Newbie needs assistance on setting the gap between boom and mail sail and between boom and jib on a scratch built RC yacht. Are there any formulae for these dimensions or is it a matter of experience.
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tobyker

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Re: Sail spacing
« Reply #1 on: January 24, 2007, 08:11:15 PM »

Maybe I don't understand the question, but I don't think there should be a gap between the foot of a sail and its boom.  Normally they are laced tight, but sometimes the sails overlap the booms, as the foot is cut in a curve to get you a bit of unmeasured area, but this can sause problems with reefing.

I think. ???

Remember Dixon Kemp- " a craft of which the mainsail boom does not extend beyond the taffrail is not a sightly craft".

Right on Man. Bring on the plank on edge cutters.
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BobF

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Re: Sail spacing
« Reply #2 on: January 24, 2007, 09:14:00 PM »

Hi Catalina,

This could end up with quite a lot of differing answers I believe.

There is a general rule of thumb (or should that be rule of finger) with One Meter yachts which have a loose footed sail. As it's a year plus since I set mine up, I am struggling to remember, but I think it's three fingers between boom and middle of the foot for the main. And two fingers for the jib. I think the biggest stumbling block for a definite rule lies in the cut of the sails. Single or multi panel etc. and the shape of the luff on the main. I would suggest you have a look at Lester Gilberts site for very tech info though.

 The best advice I can offer, is to trim them to give the best sail set and work from there.

Good luck
Bob
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martin-R

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Re: Sail spacing
« Reply #3 on: January 25, 2007, 06:44:03 AM »

In light winds, it's common to increase the gap and reduce it in stronger winds.
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MikeK

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Re: Sail spacing
« Reply #4 on: January 25, 2007, 08:59:25 AM »

When I first read Catalina's question I had the same reaction as BobF ie is the yacht scale or 'racing' configuration ?? I agree Lester Gilberts site should be of help it's at :

http://www.onemetre.net/

Cheers

MikeK
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Catalina

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Re: Sail spacing
« Reply #5 on: January 27, 2007, 10:12:36 AM »

Many thanks to all for your responses.

I looked at Lester Gilbert's material but found nothing specific. There is a photo of his IOM with  sails laced to the booms but I suspect this would be for the particular test he was running in the wind tunnel. Elsewhere his photos show space between sail foot and boom.
My conclusion from this exercise is that the sail foot, apart from the corners, needs to clear the boom with just sufficient clearance for it to move side to side as the heading changes.
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tobyker

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Re: Sail spacing
« Reply #6 on: January 27, 2007, 03:45:04 PM »

Possibly but there is a difference between vertical gap which is determined by the cut of the sail, and the horizontal gap which is determined by the tension of the sail.  If the tension is slack, the unmeasured area of a loose-footed sail can hang down below the boom, giving you a bit more area. The slackness should also let the sail ride up over the boom when the yacht goes about. To some extent this will depend upon the stiffness of the sailcloth, and how scientifically the foot of the sail is cut and bolt-roped.

I suppose your low-wind set of sails will be cut with greater overlap and set looser than the storm set.

But I'm only a scale sailor, not a racer.
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MikeK

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Re: Sail spacing
« Reply #7 on: January 27, 2007, 03:56:18 PM »

You've got it about right, Catalina, made fast to booms at both lower corners and enough belly in them so when you look down from above you can see an aerofoil shape to the sails. Less belly - stronger winds and vice versa. This is achieved by having some form of adjustment at the after boom attachment.

MikeK
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cdsc123

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Re: Sail spacing
« Reply #8 on: January 27, 2007, 05:59:07 PM »

Also, keep the slot constant, i.e. when looking from above the curve of the full foresail should lead nicely into the curve of the full mainsail. The main is the powerhouse, the foresail feeds it air and it needs to be at the correct angle. Having said this, if you find you have weather helm, flatten the main a little but not the foresail, and vice-versa for lee helm.
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Catalina

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Re: Sail spacing
« Reply #9 on: January 29, 2007, 11:14:22 AM »

Thanks again to all for your responses.
 
Now to water for trials. Will report back later just in case there is any interest in the outcomes.
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