T foil rudders on Cherubs?
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=1329
Printed Date: 15 Aug 25 at 9:14am
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Topic: T foil rudders on Cherubs?
Posted By: Guest
Subject: T foil rudders on Cherubs?
Date Posted: 27 Dec 05 at 11:10pm
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Seems they have transformed the 14, do the Cherubs use them? Rick |
Replies:
Posted By: Isis
Date Posted: 27 Dec 05 at 11:42pm
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yes. is the short answer  there are probibly only about 4-5 boats with them fitted but they are worth having (on the newer designs at least) from what ive heard ------------- |
Posted By: Wave Rider
Date Posted: 28 Dec 05 at 9:31am
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Yep, i've heard they make a massive diffrence on boats which have them and are down to weight. I think in non planing conditions they are a big help too?! ------------- -[Franko]- Chew Valley Lake Sailing Club RS600 933 |
Posted By: Chris Noble
Date Posted: 28 Dec 05 at 7:28pm
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there are many benifits to them but only more so when planing, from all the info ive had on them they are not benificial in non planing conditions but make the biggest difference in marginal on off planing conditions apparently. I shant go into a schpeel about all the other stuff though unless someone wants my tupence ------------- http://www.noblemarine.co.uk/home.php3?affid=561 - Competitive Boat Insurance From Noble Marine FOR SALE: I14 2 Masts 2 poles 3 Booms, Foils Kites/Mains/Jibs too many to list. |
Posted By: I luv Wight
Date Posted: 28 Dec 05 at 9:24pm
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The benefits appear to be less pitching upwind ( especially in light winds and a bit of slop ), and more stability fore and aft - which is not always a good thing.
The major advantage is trapezing upwind in f3+ with both crew well aft, supported by the T-foil lift. There is less drag from the hull due to lower displacement, and this reduction exceeds the extra drag from the T-foil. The boat is now not very sensitive to crew position trim, the T-foil controls the trim angle. The lift varies hugely with boat speed ( proportional to square of the speed ), and so continuous angle adjustment is required. Some boats use foils fixed to the blade, adjustment by raking pivot pin, with string/cleat adjustment. Alternatives are adjustable angle foils, controlled by twisting tiller extensions. 
twin extensions rotate shaft attached to drum attached to cable attached to crank attached to long push rod inside blade attached to lever arm attached to shaft attached to foil blades . - simple really ! This setup enables the blade to be fully retracted for launching etc. |
Posted By: Isis
Date Posted: 28 Dec 05 at 10:16pm
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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? ------------- |
Posted By: I luv Wight
Date Posted: 29 Dec 05 at 2:08pm
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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. |
Posted By: andy_cherub
Date Posted: 30 Dec 05 at 9:46am
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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/aquamarina - 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! ------------- -12ft skiff, Team 'CST Composites' -Many thanks goes out to all of my sponsors. Ignore my user name, my views are of a 12ft skiff |
Posted By: andy_cherub
Date 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!!!  ------------- -12ft skiff, Team 'CST Composites' -Many thanks goes out to all of my sponsors. Ignore my user name, my views are of a 12ft skiff |
Posted By: Chris Noble
Date Posted: 30 Dec 05 at 10:05am
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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 ------------- http://www.noblemarine.co.uk/home.php3?affid=561 - Competitive Boat Insurance From Noble Marine FOR SALE: I14 2 Masts 2 poles 3 Booms, Foils Kites/Mains/Jibs too many to list. |
Posted By: JimC
Date 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. |
Posted By: Isis
Date Posted: 30 Dec 05 at 1:42pm
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 ------------- |
Posted By: m_liddell
Date Posted: 30 Dec 05 at 5:42pm
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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. |
Posted By: Iain C
Date Posted: 31 Dec 05 at 11:48am
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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!!! ------------- RS700 GBR922 "Wirespeed" Fireball GBR14474 "Eleven Parsecs" Enterprise GBR21970 Bavaria 32 GBR4755L "Adastra" |
Posted By: Granite
Date Posted: 02 Jan 06 at 6:10pm
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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. ------------- If it doesn't break it's too heavy; if it does it wasn't built right |