Is it better to have a sharp prow on a Footy, or is a rounded prow better? I have noticed that very few boats have a really sharp prow.
Because of the very low Reynolds numbers where Footies operate, I am guessing that the sharp prow has less drag as long as the boat is going straight. But if it is bouncing around or turning, the sharp prow might cause early flow separation and high drag. The rounded prow also adds a litle more flotation up forward, to counteract nose-diving. A sharp prow is also more susceptible to damage.
I’m trying for a compromise with a sharp brow, but swelling to a fatter bow further up to counteract nose-diving.Both are still works in process although both have sailed, but not competitively. With hulls this small, you can really only assess the benefits of anything by comparison with another boat. GPI sailed well but is a wet boat, while GPII seems slow. Still trying to learn!!!
I’ve been a bit stalled on Footys due to servo problems with HS-55 Hitecs. I have two which got immersed and one wont operate at all, while the other will only return to center if it is manually turned to one side, but not when turned to the other. That is the only function it will carry out. Both have been taken apart, cleaned and dried and sprayed with contact cleaner–but no joy. All info or suggestions welcome.
Walt,
My Cobra 3 (which you have seen) has a fairly blunt bow, while the new Razor 3 has a very sharp bow. Both go to windward very well. Right now, using identical sails, the Razor has a slight edge going to windward, while the Cobra has a slight edge downwind - all as you might expect.
My next boat will be a Cobra 3 varient where Bill Hagerup has extended the bow to give a sharper prow and a slightly longer waterline. One is currently being built on Long Island and i will get to start mine in a month or so. It will be interesting to see how they compare.
Scott
I was one of the first people to use what I call ‘bullet bows’ in Footys. I do bot say that the logic is correct or that the theory is anything but witchcraft. For better or worse, here it is.
The effect of widening the bow right forward on the moment to bury the bow by x mm is surprisingly great. The volime is small but the lever arm about the centre of action is large. This is pure Archimedeann mechanics. Since it has been uded in genral engineering practice for about 2500 years, it is pretty likely right.
Much nearer to witchcraft. In Smooth(ish) water I think that the globular/bullet stem generates an area of dead water ahead of it that becomes part of the effective wave-making length - i.e. we get a slightly longer boat free.
Quasi-witchcraft. There is published research on mooring supertankers that suggest that they will ‘fly’ upstream in a tidal stream. Most of the research applies to vessels with bulb bows and globular stems, but thre is evidene to suggest that the bulb bow is not fundamental.
A question for the cognoscenti: