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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction > Rudder construction
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Thread: Rudder construction Reply to Thread
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Topic Review (Newest First)
03-03-2010 09:44 PM
Flatfendershop Thanks for the info Gorchew. I wish I would have seen these about 6 weeks ago, at that price I could have used them and built to them. For now I'm beyond that point and would have to backtrack a fair amount to utilize them.

I will wind up with much the same set-up - composite core, reinforced with aluminum, wrapped in fiberglass.

My lower blade is 36" long, 12" at the widest at the top, tapers to 8". This is a little wider than my OEM rudder, but not being a nautical engineer I decided to build oversize and cut it down later if needed. I tried to cut up a different project, that didn't work so well (that was a joke, cut down, cut up...never mind )

Nice to hear another V 21 is under restoration. Mine too was basically free, now she's gorgeous and near new. Last year we had her on the water several times and were not disappointed at all. I've gone bow to stern, she's all new paint, seals, hardware, sails, interior, and rigging. I built a new trailer with all sorts of custom gadgets.

Good luck on yours.
Flat.
03-03-2010 07:50 PM
Gorlog
Different woods, different uses

One of the positive things about teak is that it is practically unaffected by water. Most woods (particularly soft woods, such as pine) have cells that tend to retain their ability to swell with water (cellular osmosis), and to actually transport the water through the wood, as if the tree were still alive. Furthermore, since the tree has been cut, and is no longer in one piece, it tends to twist and warp, since it no longer has the torque of the rest of the tree to keep it in place. One thing that is done to counter-act twisting and warping is to use a quarter sawn plank of wood (it's length emanates directly from the core of the tree), this tends to give a piece of wood that is more stable and will grow and shrink, rather than twist and warp. Plywood is also more stable as it has different grains in different directions all laminated together, but the laminate should be as water resistant as possible.
Teak however is so naturally saturated with it's own oils, that water basically beads up on the surface, kind of like how a duck never gets wet. As far as this property goes, teak is unquestionably the best. Other types of wood have similar properties in varying degrees. Once again however, aluminum would be even better.
It just so happens to be that I found this thread because I'm working on exactly the same project as you. I have a Venture 21 that I'm totally redoing, I got it on the side of the road with a big free sign on it. Needless to say she's needed a ot of work. I happen to be a metal worker as well, and was actually going to do something similar, make my own kick back rudder. I was just going to buy the blade on e-bay and manufacture the rest. And it just so happens that I found a set of two blades on ebay item #260561129457, they are 31'' long, 9.5'' wide, and .750'' thick. They are fiberglass with alots of stainless reinforcement rods in them. Thus my own question? - Is it big enough? the auction ends in 1 hour, so I hope you see this and reply in time. If your interested I will sell you one at half price of the auction.
Thanks and good luck with your rudder - Gorchew
02-18-2010 10:27 AM
Flatfendershop Thanks Mechsmith, I suspected something similar to what you described. Should be no problem.

On the attached pictures you can see what I have so far. The lower section of the rudder is just out of the gluing stage, so I haven't done any shaping on it yet. You can see the layers glued together with 3M 5200, I'll radius the leading edge and taper the trailing edge so it is shaped like a foil.

Again, the layers are two 3/4" slabs of HDPE (I think) (I don't know the exact composition of it - so we'll call it "plastic"). The outter layers are 1/8" aluminum. I used the plastic for bulk and light weight and it won't swell when it gets wet. The aluminum is there for strength.

The upper section is all aluminum, 1/4" plate with 3/4" aluminum barstock for spacers.

The tiller is 1/2"x1 1/2" aluminum bar stock. I wrapped the end with 1/4" rope to make a grip. There is a pin that will pull out and allow the tiller to fold down for storage when I pull the rudder off. It will also fold up and lock so its out of the way during anchorage, etc.

Over and out! Flat.
02-17-2010 10:25 PM
Mechsmith Mine is all wood (3/4" marine plywood) but similar to yours . The rudder simply pivots in the frame. I have a Nyloc nut and bolt through the "sandwich" and a couple of coned washers to spread the load. You will need some rubberized washers between the metals. Use some industrial belting or the sides of an old tire for your friction washers. You will need four rubber washers and two metal ones. Then just tighten the nut as necessary to hold the rudder down. I simply reach over the transom and push it down. You may need a handle or something. No biggie!
02-17-2010 11:20 AM
Flatfendershop David, I had to google vacuum impregnate but now I understand the process. Sounds like a good solution if you were set up for it.

Mechsmith - I'd be interested in your suggestion of a friction clutch. Could you take a picture?

What I have so far is the upper portion that ties to the transom is all aluminum, built from 1/4 in plate. The lower rudder is a laminate with a polyethelene core and aluminum shell. Its pretty high tech if I do say so myself.

The plan was to use a spring system to hold the rudder down and up. The only danger is that when the rudder is pulled up, I don't want it to come up so fast that it hits the helmsman in the nose.

I'll take a couple of pictures tonight and put them up.
Flat.
02-16-2010 01:01 AM
Mechsmith In my 15' daysailer the rudder is held down by a friction clutch on the thru bolt. Force it down by hand and if you hit bottom it just hinges back up.
02-15-2010 11:53 AM
DavidBonesmith What you could do is vacuum inpregnate the wood to increase its resistance to the water.
11-29-2009 06:42 PM
Flatfendershop This is all very good info. Thanks for the input. I can appreciate some of the comments, such as getting a consistent foil shape out of the aluminum and the warpage issue on wide wood planks.

I did think about using a layer of 1/2 inch plywood in between the solid pine in order to help the overall strength.

I didn't think about the floating issue and have wondered about keeping such a system in the down position. I thought I would rig a rope to tie it down, and another to hoist the rudder up when needed. One concern is allowing the rudder to pivot up in the event I got into the shallows. It needs some sort of shear pin type setup-maybe a wooden shear pin that keeps the rudder down but would break if stressed by a sand bar. A weight sounds much better, no fussing with a pin.

I wish I lived near a marina so I could go look at some samples. I'll keep kicking this around until I settle on a good plan. No money to waste on experiments (unless they're free!) Flat.
11-28-2009 11:23 PM
paulk Teak is renowned specifically because it does NOT tend to rot, warp or swell a lot in moisture-laden situations. Pine.... is not teak. In wide boards, it is especially prone to cupping, warping, and rotting. Wrapping it in fiberglass forestalls this, but is a lot of work. For your application and abilities, sticking with aluminum would seem to make the most sense. You can trim it to be moderately hydrodynamic, you won't have to ballast it to make it sink (half inch is pretty hefty) it's compatible with the rest of the steering system you've already (re)built, and you know how to work it. K.I.S.S.
** please note that original poster is experienced metalworker who has already redone tiller in aluminum.
11-28-2009 05:20 PM
TQA Google westsystem for some good info on how to produce a wood epoxy laminate.
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