Originally Posted by Ann T. Cate
Hi, Matt, et al,
You should PM Jim, and he can tell you all about it. Briefly, the push/pull concept
was based on the Autohelm
one; the vane part was of his own design; original pintles were s/s, and after emergency
welding on Raoul Is., when we returned to NZ, he had bronze ones cast; the auxiliary rudder
shape was based on airfoil design from a text--and the rudder
was balanced. I think he still has some drawings on the boat, his drafting was done on quad paper. The rudder was constructed of 3/4" marine
grade ply, IIRC, which he used epoxy
to laminate up. He made a template to get the foil shape right. Like everybody says, YMMV, but it was doable, and it was a success. The hardest bit for him to come by then was teflon tubing to run the steering cables
through; IIRC, once we used polyethylene instead.
Ann, you chose a practical and handy man there. ;^)
I will contact Jim, and hopefully he does not mind you sharing his IP with the Internet
at large... :^)
Teflon guide cables
....? I just happen to have a long roll of some made by an Italian bicycle parts
manufaturer that are incredibly strong AND weather
proof. They are what are used for brakes on Campagnolo equipped road bikes. Should do the job, the breaking strain is incredible and the friction is practically non existent. Can't see the salt environment
presenting a particular challenge, particularly if I fit the rubber bellows to the ends.
I was trouble by the pintles, felt they would need some kind of bearing. And I also felt no more than an 80/20 balance on the blade would be about right, but if Jim sorted this bit, and is happy to share, I will shortcut the trial and error. Also the foil shape is complicated by trying to prevent cavitation and stalling while trying to keep the blade shallow to minimise leverage. Maybe Jim found a good compromise...
What am I saying...!!!? This is starting to sound like I am going to build my own.... But tempting, oh so tempting. I will gently sound out the admiral. I know what she will say... if I finish her mini and the house roof first....