Simplest Proa Rudders
Whilst i love the simplicity of this concept, my concern is that will it fail on 2 accounts:
- at speed it will shale & vibrate like crazy?
- there will be too much friction?
Mark
Not sure why you say this? The boards won’t have any more likelihood of flutter than any other. Is your concern about the loose-fitting trunk? Lots of daggerboard and centerboard boats have loose fitting trunks (heck, leeboards often have no guides at all, just a bit of lead to sink the board and a big old rope hanging it from the rail!), and the “improvements” offered here all make that trunk tighter fitting, with the vaguely “hourglass” shaped cutouts. So long as the board is loaded, it’s not going to flop around, regardless of the trunk shape and size
Where are you concerned about friction, the oversize trunk again? (you may be envisioning water geysering up into the air!) This is why it was proposed as a leeboard, running in “staples” as it were—call them hoops, or wickets, or just pieces of bar stock square-bent. In this case the staples can either be all above the water (my preference) or made up of stuff that is in line with the waterflow—either way introduces almost no friction at all, though it leaves the board as a surface-piercing foil, like all leeboards are.
If you opt for daggerboard trunks, then my advice is to make it much more like my earliest sketches, not like some of the later ones which feature far more angle, but require very large cutouts. These are fine—a great improvement—for leeboards outside the boat and/or above the wateline, but not as daggerboard trunks. Nobody has yet countered my claim that +/- 10 degrees on each board is sufficient to steer the boat. Sometimes it may not be.
Dave
I agree that there will be friction, mainly due to where the leading and trailing edges rub on the ends of the ‘staples’. Whether this will be enough to stop the system from working remains to be seen.
I’m wondering how you propose to shunt the boards (change the rake angle)? From experience I know that they will not shunt themselves if you are just relying on rudder drag, (even with a low friction bearing). They will have to be shunted manually, so you will need a method to access them, or some secondary linkage to actuate them.
Mal.
I agree that there will be friction, mainly due to where the leading and trailing edges rub on the ends of the ‘staples’. Whether this will be enough to stop the system from working remains to be seen.
I’m wondering how you propose to shunt the boards (change the rake angle)? From experience I know that they will not shunt themselves if you are just relying on rudder drag, (even with a low friction bearing). They will have to be shunted manually, so you will need a method to access them, or some secondary linkage to actuate them.
Mal.
Throughout this little exercise I’ve been concentrating on simplicity, not actual, practical application. Any parts, even the whole thing may not work at all, but the purpose of the exercise is to demonstrate that it doesn’t cost but a few bucks to try, and then we’ll all know.
Yes, there will be friction with the trunk/staples. As the huge majority of force is ‘thwartships, that’s where I focus—and we’ve maintained simple rolling friction between board and trunk in all iterations so far. This can be as small as, and perhaps even smaller than, typical and acceptable friction of rudder gudgeons and pintles, tiller linkages, whipstaff tillers, steering wheels, pullies and cables, etc, etc. Will the ends of the boards bearing on the front and back of the trunk be a deal-killer? Perhaps, but I don’t think so. Lining both these surfaces with PTFE or Delrin is always an alternative. Easy to retrofit if needed—or not, if not.
Shunting the boards couldn’t be simpler, in the little universe I like to call my mind. During or after the shunt, a simple tug (heave?) on the flexi-tiller in the direction of the new bow, and the boards are shunted. If done during the shunt there’s little friction to overcome and both boards are all set up and balanced for the new tack. If after, then you have the wetted surface drag on the boards in the right direction to assist.