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T foil rudders on Cherubs?

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Post Options Post Options   Quote Granite Quote  Post ReplyReply Direct Link To This Post Topic: T foil rudders on Cherubs?
    Posted: 02 Jan 06 at 6:10pm

the T-foils are definatly interesting, as well as the riding the fin aspect up wind( which is great}, they improve pitch and lateral stability making the boat smoother to sail.

Plus down wind you let them off and they can help to save you from a pitchpole

If you built an articulating blade foil then it would be easy to swap the blades to experiment with sizes, howver I think it would be easier just to build two fixed foil blades.
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Post Options Post Options   Quote Iain C Quote  Post ReplyReply Direct Link To This Post Posted: 31 Dec 05 at 11:48am
I've sailed Andy's Aquamarina and it does feel really weird!  When you wind the foil on the nose just makes a beeline for the seabed, but as soon as you move back you really feel the boat start to fly upwind, it just feels really odd being at the back!

I think that a bistro will probably benefit even more so from a T foil than a skinny boat...be really nice to be able to lift as much of that fat hull out of the water as possible.  I'm certainly planning on building one sometime next year.

The one thing I have no idea about is the size of the T foil...there was a huge difference in size between various foils at the Nationals.  What would be cool would be to have the main spar (as in aviation) as a secure part of the rudder and then be able to put interchangeable foils on depending on wind strength!!! 
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Post Options Post Options   Quote m_liddell Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 05 at 5:42pm

T foils don't seem to be very well understood at this time. At fed week most of the 14's took them off. They are especially difficult to analyse since the rudder blade and the hull all have a large effect on the flow so I guess the only way to find out what is going on is through trial and error.

From the descriptions from cherub sailors, upwind it seems like the boat equivalent of 'riding off the fin' windsurfing.



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Post Options Post Options   Quote Isis Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 05 at 1:42pm
Originally posted by I luv Wight

It seems to help if the crew stays back if the nose dips, instead of running forward up the gunwales, and then flying round the front.


That brightened up my otherwise quite crappy day

Thats for the replies Andy and Andy and Jim, It something id quite like to look at after ive sorted my daggerboard, snout, pole, stump, fittings, rig, trolley and a whole pile of other bits
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 05 at 10:19am
I'd be suprised if the wider boats didn't benefit from a lifting foil upwind. Fixed foils I'm not quite so sure about. I have a feeling I Luv Wight might have tried one without total success -- too much stuffing of bow into waves IIRC.
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Post Options Post Options   Quote Chris Noble Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 05 at 10:05am
yeh i was going to say that next, my old foil on the moth was fixed and as are most low rider t foils and they have there own benifits when it comes to inducing planing aswell quite technical but just cause they are fixed does not mean to say they are at a disadvantage
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Post Options Post Options   Quote andy_cherub Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 05 at 9:49am
& oh, Aquas & Primals foils are very easy to make - fixed "T" on the rudder blade and just knock the rudder stock back and forth! No little fiddly bits to go wrong, sorry Andy, not aimed at you, but if I tried making yours Id prob Fek it up!!!
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Post Options Post Options   Quote andy_cherub Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 05 at 9:46am

I have a T-foil on Aqua, shes a P7. Makes SO much difference - twining upwind, both myself and crew in rear fruit loops - you feel the acceleration as you put it on! It enabled us to pace a windsurfer upwind, one of these big roached sail jobbies with the bak of his sail flipping off.

http://www.sailingsource.com/cherub/dokuwiki/doku.php/aquama rina 

My foil has a very long span & quite a thick chord, so its ideal for lighter winds where I can get upto 8knots boat speed and have full foil on, twining as far back as poss & max lift!! So im now designing another foil to use in around 20knots of wind which will be alot smaller, due to the current foil needing to be eased off, and causing more drag. Where as a smaller foil will be on full angle and less drag!

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Post Options Post Options   Quote I luv Wight Quote  Post ReplyReply Direct Link To This Post Posted: 29 Dec 05 at 2:08pm
The narrow P7 has less of a pitchpole issue than the blunt-bowed bistro type. The narrow entry angle, carried right up to gunwale level means that it pierces the waves, without much slowing down. You can dip the bow, and still sail fast, and wait for the bow to pop up again.
I havn't done a real pitchpole in my P7 ( but i do know a man who can pitchpole his in a f3! ) It seems to help if the crew stays back if the nose dips, instead of running forward up the gunwales, and then flying round the front.

The upwind lift should benefit the wider hulls too.

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Post Options Post Options   Quote Isis Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 05 at 10:16pm
Not that im planning on building one anytime soon but whilst we're on the topic, do you think a bistro style hull would benefit from a Tee?
They dont have quite the same pitchpole issues as the narrow P7 style hulls which seems to be the main reaosn the 14s use them but if you think its the lift upwind thats the main advantage then surely a fat hull would bennefit as much?
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