Carbon is an artform and a means of self expression nowhere more apparent than in the moth class and in particular (in relation to this entry) Mike Cooke’s famous 08 curly tipped rudder as featured on the Axiom 4s.
Lately I’ve been striving to get the mistress to ride as high as possible based on the logic that has been used to great effect with the Mach2s ie. the higher you ride, the more room you have for foiling transitions apart from the fact that it is more efficient (less whetted foil surface area) but the problem I’ve been having is that the back end keeps cavitating due to the tips piercing the surface. The other problem (having discussed this with Mike Cooke a while ago) is that the Axiom rudder and Ninja main foil are imbalanced and creating too much overall lift.
Yesterday we had a great session to figure this out. Winds were moderate (12-18mph) and sea state was choppy with a ground swell running. We are used to the conditions now but suddenly with all the extra ride height it’s a new ball game in terms of control. It was obvious after a while that the rudder is just generating too much lift in relation to the main foil. Lots of deep runs offwind ended in some impressive crashes as I just couldn’t keep the tail down despite winding off lift through the tiller.
So the plan was hatched to chop off the tips off, which would effectively give another couple of inches of height tolerance at the back and also reduce the lifting surface area. Today was a day of carbon butchery as I attacked Mike’s artwork but I wanted to keep in line with his original concept of being different hence the final appearance of a hammerhead courtesy of the tip fences.
This should help the top end performance now in the rougher stuff and due to the fact that there was too much rudder in the first place, low end shouldn’t be affected.
Another good thing is Jonnie installed the fluorescent lights in the garage in preparation for the Ninja build so working in there is much better now.
Heh, cool. I’ve been busy copying you today, nearly have a nice new wordpress site…
Excellent, I look forward to seeing it! Thanks for tip on chopping the rudder down. It was painful demolishing your foil!
Nice work. Looking forward to seeing how you get on with the new setup.
A small rudder lifting foil sounds like a good idea, but you will probably find the same problem at speed. To fix that you need to run the mainfoil deeper or add some height to your rudder vertical. This is I think why rudder verticals have been getting longer lately – people are flying the main foil really shallow and the rudder vertical simply runs out of length. Nearly happening to me here:
http://2.bp.blogspot.com/_g6gy7cgKvuc/SuW15v5MgwI/AAAAAAAAATM/CQhBj3F5kbQ/s1600-h/DSC02383.JPG
PS. I’ve just looked again through morning breakfast boredom and I would like to point out it is VENTILATING not cavitating. everyone gets this wrong and it is annoying!
Cavitation is when the water pressure gets so low that it vaporizes and can/does serious damage to stuff when this happens…
phil we got to find out how to do some of this cavitation stuff !! i like the sound of vaporization sounds a laugh. Make it so number 1!!!
Ooops sorry Mike I meant VENTILATING! I agree I’ve never cavitated.. only ventilated!
Karl, My rudder verticals were always longer anyway so Phil shouldn’t have as much a problem as others in this respect.
Jonnie, You need to go a lot faster!
cookie i`m waiting for your foils then i`m going cavitating,
Actively seeking cavitation may void your warranty!