Making a wooden rudder

[Alastairdent]

I have an old steel boat whose rudder is damaged and worn. Currently it's 4mm steel with wooden 'cheeks'. The steel is very corroded, and the wood is not in good shape.

Rather than repair it, I was thinking of making a replacement out of ply, sandwiching two slabs of wbp ply, profiling them then soaking in epoxy. This has the advantages that I'd only need a jigsaw and hand tools.

I was thinking of adding some grp matt on the edges, both to keep water penetration down and add some abrasion resistance.

Has anyone done this? Hints and tips welcome please.

 

[Tranona]

You don't say what style of rudder you have so difficult to comment. If it is transom hung and you have the fittings, then a Ply blade would work, but if it is any size it would have to be quite thick to get any blade shape and avoid warping. Would not use WBP unless you intend sheathing completely in epoxy and glass cloth. GRP matt is not appropriate as it does not adhere well to wood.

If it is a rudder with a stock going into a tube, then a SS stock with tangs and a sheathed ply blade would work, but again if you want to have any shape to its section you may want to build up a composite (wood/ply/epoxy) blade.

Piccy would help

 

[mickshep]

Agree with Tranona re' rudder type but would use Marine grade 1088 plywood sheathed in epoxy/glass. I recently bought 12mm WBP ply for the berth bases on Wraith. There were a lot of voids within the laminates which had a major impact on strength, (It was cr*p) A rudder can take a hell of a lot of strain and I for one would pay the extra on strength grounds alone, regards, Mike.

 

[Alastairdent]

Sorry, should have said.

Transom hung rudder.

Fitting are bu&&3red, a bad storm had the boat pounding on the bottom and broke some of the fittings. So I have those to make/replace as well.

Was thinking of using agricultural gate hinges - my landlords have them, very heavily galvanized 6-7mm steel.

The boat is only 28ft.

What sort of ply would you recommend? part of my problem is that the boat is a long way from home, I don't want to drive there, would rather use the train and make use of what I can carry or purchase locally. So a welder is out of the question!

 

[Tranona]

Rudder on even a 28 ft boat takes a lot of forces! Assume it is supported at least 3 points, 2 on the transom and one in some form of heel fitting, or at least toward the bottom of the rudder blade. For construction use BS1088 marine ply, at least 15mm for the main blade and and sandwiched between two 15mm cheeks the full length of the leading edge. Won't look pretty, but will be strong. Can't really comment on using hinges for fittings as don't know what you have on the boat to mate up to. Galvinised is OK, but wears off the bearing surfaces. Stainless or bushing pivot points with a bearing material such as Delrin is better.

Trying to imagine carrying a rudder that size on a train!

Hope this helps.

 

[Alastairdent]

Yeah, it all helps.

I was thinking of using 15mm ply doubled - prob need two sheets. so a thickness of 30mm over the whole rudder, plus extra under the fittings.

the original rudder had mild steel for the fittings, and this has worn away. Replacing them is going to be a right pain as welding isn't a very likely option. It's the fittings on the boat that are gone.

There were 3 fitting points originally. I think I can repair the top one, and add another just above waterline. Drilling through the hull to bolt that on is a bit scary, but I guess lots of boats have this sort of fitting. SS bolts plus bedding onto sikaflex?

Bolting can be done easily, as it is possible to beach the boat at low tide.

 

[Peterduck]

Take the thickness of the sternpost as a guide to the required thickness of the rudder. A friend's 25ft Lyle Hess cutter has a rudder that took two of us to lift,and I wouldn't want to carry more than a few feet. Look to your hull fastenings for a guide to what the rudder fittings should be made of. If copper-fastened, then gunmetal fitttings will be compatible, fastend with copper bolts. Don't consider using Stainless steel bolts below the waterline; they'll erode quickly.
Peter.