Dinghy development: Are loose footed sails more powerful?

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Are loose footed sails more powerful?

Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=1770
Printed Date: 15 Aug 25 at 2:23pm
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Topic: Are loose footed sails more powerful?

Posted By: Matt Jackson
Subject: Are loose footed sails more powerful?
Date Posted: 16 May 06 at 1:57pm

In the Y&Y piece about National 12s in the last edition there was a statement about the change to loose footed sails and it making the rig more powerful offwind.

Is this really true? and if so does it affect more than just a 30cm band along the boom on a tracked sail?

I'm thinking of buying a loose footed sail but keeping my tracked boom so I don't have to re-cut my 'practice' sails. At 14 stone sailing on a lake I lack power on a reach and it may sway my decision to go for loose footed if it gave me some more power.

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Laser 203001, Harrier (H+) 36

Replies:

Posted By: tack'ho
Date Posted: 16 May 06 at 2:28pm

I would have thought it would make the rig a little more powerful as the extra depth gained by the loose foot will continue up the sail for about a 1/3rd of its height.

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I might be sailing it, but it's still sh**e!

Posted By: Jon Emmett
Date Posted: 16 May 06 at 2:57pm

Remember more power does not always equate to more speed due to drag...

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http://www.amazon.co.uk/Be-Your-Own-Tactics-Coach/dp/0470973218/ref=sr_1_1?ie=UTF8&qid=1312565831&sr=8-1 -

Posted By: Guests
Date Posted: 16 May 06 at 2:58pm

I would have thought the power potential of having a loose foot would be dependant on wind strength and boat speed. In the lighter winds it is much easier for the wind to flow around a flatter sail, and so a full foot would be more of a hinderance. Though certainly in the upper wind conditions, the wind has the strength to keep flow attached to a fuller sail and thus with the wind being able to travel a greater distance round the the back of the sail, more power developed.

I would then guess that a loose foot sail would certainly help through the range of mid to upper wind conditions but not be as quick in the lower wind ranges.
With that in mind it could then be said that the loose foot sail will improve speed in a vaster range of conditions than what it would lose, so possibly a good investmant indeed.

Doug

Posted By: Bruce Starbuck
Date Posted: 16 May 06 at 3:17pm

Matt, I think what they are referring to might be the extra area you get from the foot round on a loose-footed sail, not anything to do with the depth of the sail at the foot or not being able to ease the outhaul enough.

I've never sailed a boat with a tracked footed main and gone down a reach thinking, "Damn, if only I could ease this outhaul a bit more, then life would be great!" You can ease off the outhaul as much as you like on either type of main.

Wheras a main with its foot in the track will not be able to extend below the boom, with a loose-footed sail you will get say 30cm of foot round which will sort of fold itself up against the boom when the outhaul is on, but will drop down and set when you ease the outhaul.

So you get a little bit of extra area, but I'd be very sceptical of exactly how useful it is down there below the boom. Still, it's probably worth having, and a loose-footed main is easier to build than one with a soft shelf foot and boltrope, so you might save a couple of quid too.

Posted By: Stefan Lloyd
Date Posted: 16 May 06 at 4:39pm

In classes that allow the choice, quite a few people find loose-footed mains more convenient to rig, but I've never heard it suggested before that they are either more or less powerful.

Posted By: Chew my RS
Date Posted: 17 May 06 at 8:10am

If loose footed sails are easier to rig, cheaper to make, and no slower, why did they use to be tracked?

Posted By: Stefan Lloyd
Date Posted: 17 May 06 at 8:24am

There was a theory that loose-footed are less powerful, because breeze leaks between the sail and boom, whereas on tracked the boom effectively forms part of the sail area. I don't think well-informed opinion believes this anymore.

Also I presume roller-reefing would require tracked. No longer common but it used to be on smallish yachts.

Posted By: JimC
Date Posted: 17 May 06 at 8:42am

Originally posted by Chew my RS

If loose footed sails are easier to rig, cheaper to make, and no slower, why did they use to be tracked?

'Cause it dates back to when all sails were laced to the boom. If you go back far enough part of the load from the sail came through the lacing whih meant the boom didn't need to be as strong. Once people started to understand about sail shape the lacing stopped doing anyting structurally. It certainly wasn't doing much by the 1930s.

Posted By: Chew my RS
Date Posted: 17 May 06 at 9:44am

Thank you

Posted By: I luv Wight
Date Posted: 17 May 06 at 10:29pm

It's a rule thing for N12s.
N12 rules don't actually measure the foot of the sail - only the black band measurement, so you get a really full sail ( for the offwind stuff ) but it can only go out on the boom so far ( with a stop ), so then you pull fwd on the tack to flatten it. Loose foot sails can cope with this big change in fullness and length better.
The plan is to get as much power as possible downwind, whilst still getting just flat enough for upwind.