Luff lengths

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Mudman
Posts: 28
Joined: Mon Aug 20, 2007 1:10 pm

Luff lengths

Post by Mudman » Mon Sep 22, 2008 8:09 am

Hi all,

I'm playing with spinnakers on my old boat at the moment - does anyone know what the luff/foot/leech length on a medium size kite is, please?

Cheers,

David
"No easy way to be free..."
IC 206 sailing out of Brightlingsea

Mudman
Posts: 28
Joined: Mon Aug 20, 2007 1:10 pm

Re: Luff lengths

Post by Mudman » Wed Sep 24, 2008 7:42 am

Nobody with a tape measure? :( There's a sewing machine burning out its clutch on the start line here.....

A free pair of sailing gloves (my own brand) to the first person with who comes up with some (sensible) dimensions!!! See http://www.sailbag.co.uk

Cheers,

David
"No easy way to be free..."
IC 206 sailing out of Brightlingsea

SteveC
Posts: 550
Joined: Fri Dec 22, 2006 10:32 pm
Location: United Kingdom

Re: Luff lengths

Post by SteveC » Fri Sep 26, 2008 2:34 pm

Depends on what you mean by medium size. Typically kites have settled at 23m2 as being the biggest which are manageable, 18m2 may be better on courses which are not assymetric but are a lot slower in medium and light conditions in a true windward leeward course. 20m2 which is probably medium seems to have no real advantage.

Lengths depend on the boat but on my latest Hyde, the foot is probably around 4m (it will come right back to the fairleads if pulled tight) and the luff length you can work out based on mast length with a 1.8m pole length plus roughly 2m from the foot of the mast. Assume mast is more or less vertical and pole is horizontal from base of mast and get your trig tables out and you will be close enough. Otherwise just measure of your boat to see what will fit.

Basically it's a big b*****d. :D
Steve Clarke (UK)
GBR338 "Money4Nuffin

Mudman
Posts: 28
Joined: Mon Aug 20, 2007 1:10 pm

Re: Luff lengths

Post by Mudman » Tue Sep 30, 2008 7:58 am

Thanks Steve,

I'm trying a donated kites at the moment from a Cherub until I see whether I or the boat can stand the strain (think a new/stronger one will be required over the winter)! The kite looks a bit long in the luff which is why I wanted to see if there is a "definite" measurement. Thanks for your help - need any gloves?!!\

Cheers,

David

PS - Does anyone/the class have a set of plans for a Nethercot?
"No easy way to be free..."
IC 206 sailing out of Brightlingsea

petermclaren
Posts: 110
Joined: Sun Sep 05, 2004 8:49 pm
Location: Scotland, United Kingdom

Re: Luff lengths

Post by petermclaren » Tue Sep 30, 2008 11:01 am

Hi David,

The plans for the Nethercot hull are included (at small scale) in the Canoe Measurement Rules. If you haven't got a copy contact Secretary Andy Biden. Full scale plans are available from Class Chief Measurer Colin Brown at cost of re-production.

Re spinnakers, the rules do not specify any size for the spinnaker, just that it must fit within the extremities of the black band at the top of the mast, pole length max. 1800 mm. and sheeted no further aft than 2680 mm. from the stern measured along the centreline. Luff length should be the same for all spinnakers, i.e. from end of pole to masthead, with the variation in size due to lengths of foot and leach.


Peter McL

Barry Watkin
Posts: 89
Joined: Sat Oct 07, 2006 8:37 pm
Location: United Kingdom

Re: Luff lengths

Post by Barry Watkin » Tue Sep 30, 2008 12:22 pm

Peter, I've got this on file back in my 'sail loft' as soon as I can get out of 'real' work I'll pop along the road and take a look.
Regards Barry, XGBR176AC :mrgreen:
BMW

Barry Watkin
Posts: 89
Joined: Sat Oct 07, 2006 8:37 pm
Location: United Kingdom

Re: Luff lengths

Post by Barry Watkin » Tue Sep 30, 2008 6:08 pm

David (sorry Peter!)
I played with this last winter I settled on a luff length of 7.5mtrs
A Leach of 5.55, A Foot of 3.8 and a 1/2luff to 1/2 leach (mid girth) of 3.7. I had intended to look for a foot of 3.9 & mid girth of 3.8 but on the floor I went for fair shaping.
I had looked at a few Hydes which had luffs of 7.5 to 7.8, leaches around 5.5, feet3.5 to 3.7 and mid girths 3.5 to 3.6.
In conclusion areas have grown from 19 to 23 on average & the guys seem to agree the bigger kites are more forgiving & therefore faster. I also measured a '19mtr' Lonton & gray spi luff 7.2, leach 5.3,foot 3.7 & mid girth 3.45.
Silicon coated Contender Dynalite is favorite & I used Kayospruce 8mm doublesided tape to stick a panel at a time, pre-sewing.
All the best Barry :mrgreen: XGBR176AC
BMW

Mudman
Posts: 28
Joined: Mon Aug 20, 2007 1:10 pm

Re: Luff lengths

Post by Mudman » Tue Sep 30, 2008 6:43 pm

Thanks guys, very helpful - it's out with the tape measure once it's stopped howling and raining!
And I found the measurements for the Nethercot in the rules - just forgot they were there. So is this still the default AC (give or take a little bit) or has the situation changed with the DC rules? There isn't likely to be a rash of 50kg ACs?

Cheers,

David
"No easy way to be free..."
IC 206 sailing out of Brightlingsea

jimc
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Re: Luff lengths

Post by jimc » Wed Oct 01, 2008 7:31 am

Mudman wrote:There isn't likely to be a rash of 50kg ACs?
No, nothing has changed about the AC rules at all, and whilst one should never predict the future I don't think its likely to. There's no particular need or pressure to change the AC rules that I can see.

Barry Watkin
Posts: 89
Joined: Sat Oct 07, 2006 8:37 pm
Location: United Kingdom

Re: Luff lengths

Post by Barry Watkin » Wed Oct 01, 2008 5:13 pm

Hi, like other development classes it's not until an overwhelming majority of newer boats are carrying lead that the logical ones get together & remove it!
Barry :mrgreen:
BMW

jimc
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Re: Luff lengths

Post by jimc » Wed Oct 01, 2008 7:09 pm

Barry Watkin wrote:not until an overwhelming majority of newer boats are carrying lead that the logical ones get together & remove it!
Rarely even then... I don't think the Merlins have ever reduced weight, The Cherubs certainly haven't, the 14s only did because they wanted to merge with the far lighter Australian class and split the difference... I'm not sure about the Nationals.. And of course the Nethercott hull was designed around a certain weight... I know I've taken a fair bit out of mine, but then I'm a fat slob - I reckon my Nethercott is still carrying more all up weight than Colin's is... It really wouldn't make much sense to build a 55kg AC and put 12kg lead/overbuilt structure in.

The thing that has *really* made a big difference to how my boat feels is the lightweight alloy trolley Phil R made me aware of. That's a weight reduction I can recommend to all Canoe Sailors. You can go even lighter if you make one from broken carbon masts!!

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