I've cut out my rudder box out of 1/2" okume plywood, with doug fir spacers and gudgeon strip. It will all be glassed and painted. I was planning on mahogany for the rudder, but the only piece I can find is 14" wide and 72" long. My wood guy quoted me $96 US! While I don't mind spending the money, the rudder is mostly in the water. Can I swap out white oak, stained, for the mahogany? Any other recommendations?
Dave
(12-11-2009, 08:20 AM)Dave Blake link Wrote: [ -> ]I've cut out my rudder box out of 1/2" okume plywood, with doug fir spacers and gudgeon strip. It will all be glassed and painted. I was planning on mahogany for the rudder, but the only piece I can find is 14" wide and 72" long. My wood guy quoted me $96 US! While I don't mind spending the money, the rudder is mostly in the water. Can I swap out white oak, stained, for the mahogany? Any other recommendations?
Dave
I started out with a nice rudder made from a nice piece of oak and it got a big crack through it which started where the pivot pin is. The rudder broke off when it hit something on the bottom. It wasnt' glassed though.
Then I used 1" plywood. Still not glassed. I didn't even paint it. My rudder gets damaged from oysters so I just use a plain old piece of exterior plywood. I still shaped it but I didn't paint it or coat it at all. I'm on my third rudder. Second rudder was not exterior plywood and delaminated.. third rudder is going grey but is otherwise working well.
After the first rudder broke, i ditched the uphaul/downhaul line scheme and instead drilled a single hole int he rudder box aft of the pivot bolt. Then I lifted the rudder up all the way and drilled a hole there, put it half way and drilled a hole there, and put it all the way down and drilled a hole there. I use fiberglass tentpoles cut to about 3 inches as a kind of sheer pin. It doesn't sheer when I run aground... It kind of crushes but it works perfectly for my area where depth is very variable. A rudder stuck in the muck is a huge hassle which I Have not had to deal with since switching to the crush pin scheme.
 The next rudder I make, I will try making it weighted and I'll eliminate the crush pin and just let it dangle free under it's own weight..
my boat sits on a trailer most of the time.
Dave white oak has a tendancy to turn black after wettings. If you cut that piece into strips of ~1-2", alternate the ends of every other piece then glue them back togather you will vastly increase the strength of the structure. It eliminates any flaws in the plank and reinforces the whole with the epoxy. The as designed downhaul leaves a lot to be desired. The weighted rudders work very well.
I used 3/4 inch merenti plywood for the rudder blade. Epoxy over the whole thing and it will be painted. Â Its a kick up rudder. Â The upper part of the rudder has two cheeks made of 5/8 merenti ply. Â No biax. Â The pivot is stainless and has a adjustable knob on one side so that the cheeks will tighten down on the blade. Â If it hits something it will kick up. Â but it will stay down as well.
Great article on fabrication of rudders and centerboards.
http://mothboat.tripod.com/CMBA/Building/foils.htm
I've fabricated several for different boats using these techniques. All have performed well and lasted for a long time.
The rudder for my weekender is made from very old growth Douglas Fir, very tight vertical grain material. 1 3/4" thick at the chord using the foil shapes as recommended. My goal is to compare both the standard 3/4" thick stock rudder with this and see if it makes a notible difference in handling that can be documented.
Ok question, I wonder if you couldent take (in my case merenti) but okkume as well, and epoxy it together in layers to the correct thickness, and then shaped and sanded and sealed it. would it not make a good rudder ? Possably a couple screws too.
Another Idea I had was since I made a sole for my keel out of aluminum, If I couldent take some aluminum plate and Make my rudder box with it? An aluminum rudder box May be the answer to box failure.
Brian.
The Stevensons (forget whether it was Peter or Mike) wrote an interesting piece where they talked about structural strength. One of the points made was that if things were built "too" strong that a catasrophic failure in one part would leave you floating with a spreading pile of wood chips. On the other hand, if some parts were weaker, they would fail in a safe manner that could be more easily repaired.
My rudder is pine and I'm planning on making a spare for "when" I do something stupid like back down a ramp with it not pulled up.
Oh yeah. A spare or 10 may be good to keep around for sure.
Ginny Rae's rudder is made from 1x maple, it's very durable. I'm working with the 4th rudder box and same original maple rudder. It has a few scars from dragging on rocks, and my outboard prop biting at it, still tough as nails through all that abuse.
Greg
I have an Escape Rumba that I have been sailing for 15 years, often it sits in the water the entire summer. I have varnished the rudder only once. It's made from 1X12 Ash. That is what I'll be putting on the weekender.