Making a new rudder...how hard can it be?

Greenheart

Greenheart

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I always knew when I bought the boat, that I might suddenly have to face this question. My rudder blade is okay, but definitely a bit flaky in places, and I expect that when the boat is in frequent use next year, the elderly GRP will one day crumble catastrophically and unexpectedly...parts have already done so. Right now, when sailing isn't very tempting, I could try making a replacement. Even if it's no slicker than the old one, at least I won't have a hole in next summer's season while I source an expensive replacement.

My centreboard is ply. It's in better condition and much less brittle than the GRP rudder, which isn't exactly lightweight...so is there any reason not to make a ply rudder?

Not having tried it, I'm visualising taking a piece of top-quality ply - perhaps 30mm thick, 10" wide and about 40" long, and planing it/sanding it down to size...

...but I'm not wise about what difficulties I'll encounter, or possible problems with the finished blade which mightn't have afflicted a GRP rudder. Any advice?

Prices for a new rudder from Hartley or Milanes is more than I paid for the boat...so if I can't bodge-up an adequate 'spare' blade, my sailing may stop very suddenly.

Thanks...
 
I made one for my Cherub. It had a western red cedar core and was sheathed in carbon and never broke. Easiest way of getting the right profile is actually to make an MDF box with a profiled router guide halfway along it. The blank slides through and you rout across (not along) the blade to the right profile, until the rudder has "battlelements" if that makes sense. Flip it over and do the other side, and then plane the high bits down to the low bits and you have a perfectly profiled symmetrical rudder. Profiles can be downloaded from the web...an NACA0010 profile is not a bad start. Have a look on the cherub website for a bit more info...I think I did a bit of a write up on it...search for boat no 2644.
 
I've had a ply rudder snap before. It's not strong enough unless sheathed as Iain C says. The other option is to make a laminated blade in alternate strips of softwood and hardwood - the "bacon fry" effect looks great.
 
Thanks for the advice, gents.

Nimbus, that sounds pretty perfect. Is it really straight/unwarped? I couldn't find ply thicker than 25mm from Robbins. I guess I could make up any shortfall with additional laminates.

Overall dimensions of my existing rudder are 1090mm x 260mm x 32mm...how does the ply you have, measure up? (Is there any dinghy anywhere with a bigger rudder?! :confused:)

I've seen very slender ply rudders suffer damage (in fact I caused some, crunching a Mirror with the bow of my Topper, 30 years ago) and I wasn't surprised it broke - but as the Osprey's rudder is a full 32mm thick at the top, tapering to more than 25mm near the bottom, is snapping likely? I'm assuming epoxy-sheathing is like polyester-resin coating over glassfibre repairs...easy enough to apply and a good idea anyway to resist scratches and scuffing.

I read about a Flying Dutchman rudder made in laminated lighter sections of ply, but I couldn't see how it would be stronger than a solid single section of good stuff to start with?

I'm very short of tools. Always wanted a router so this would be a good excuse to invest, and a powered plane. I suppose a B&D 'Workmate' or B&Q equivalent would be wise, too?
 
Good quality ply will be fine, although may be heavy. To get your thickness perhaps laminate 2 pieces of 15 mm together and plane your profile using the veneers as aguide to ensure both sides are the same. Sheathed with glass cloth and epoxy which will both strengthen and protect. Alternative is laminated vertical strips as Ian suggested but a lot more work and skill required.
 
When my First 18 rudder broke I had one made by the local dinghy repair man.

He laminated 3 sheets of 10mm ply with epoxy and roughed out the shape.

I wanted it before he could finish it so I ended up doing the final shaping/sanding/varnishing and it was OK.

The original was made from ply but I think it was made from one thick piece.
 
Here are a couple of articles relating to Wayfarer foils, but relevant to Ospreys as well. If you want the rudder to remain in class rules for racing, the you should obtain a full sized drawing from the class association or RYA to make sure that your shape and profiles are correct. Ply should be avoided as half the grain in it is going in the wrong direction and it is consequently weaker.

http://www.wayfarer-international.org/WIT/maint.repair.ref/CB.rudder/making_CB.rudder.html
http://www.wayfarer-international.org/WIT/maint.repair.ref/CB.rudder/finishingCB.pdf

Good luck!
 
I've made quite a few rudders over the years. I presume here we're talking about a pivoting rudder within a stock.

A wooden structure sheathed in glass/epoxy will do the job but be very heavy and you need to ensure the wood is completely encased to prevent moisture being trapped under the skin. A much lighter alternative is to use foam-cored GRP. The most essential thing is to choose the correct foam: PVC e.g. 'Herex' is ideal. PU foam is worse than useless. Polyester resin is fine for this application which is cheaper and easier to work than epoxy. Bond the requisite number of layers together using layers of grp, shape with coarse sandpaper in a small angle grinder, laminate a few layers of grp over the top then smooth with car body filler.

The resulting structure will be as strong as wood at around 1/3 of the weight.

Whatever method you use I recommend adding a piece of kevlar tape along the leading edge to protect it when grounding.

Carbon fibre can in fact weaken a structure if not designed properly, strange though it may seem!
 
There's an article about rudder construction in current (recent) YM, but of course it's about yacht rudders.

No-one has mentioned how to fix to the stock, or what the material is. Is that not equally crucial?

Mike.
 
Thanks Mike, I've got the November YM but haven't read it much yet.

My aluminium tiller/rudder stock is fairly roughly made, but seems solid, so I was thinking of making the blade fit the stock. I'd be much more daunted by having to rebuild/weld that!
 
You've got all winter. :) Make one like this:

Ent%20Milanes%20R-blade.jpg
 
dancrane said:
My aluminium tiller/rudder stock is fairly roughly made, but seems solid, so I was thinking of making the blade fit the stock. I'd be much more daunted by having to rebuild/weld that!
Click to expand...

Oh, sure. But I wondered how to ensure that, especially if the stock is cylindrical, you transmit the torque to the blade. Perhaps two sheets of aluminium screwed using self-tappers or whatever along one edge to the stock. And then to each other along the opposite edge, thus forming a sort of armature around which the fair blade is built? (If I can think of an easy way to draw a diagram, and it sounds useful, I might try!)

Mike.
 
mjcoon said:
Oh, sure. But I wondered how to ensure that, especially if the stock is cylindrical, you transmit the torque to the blade. Perhaps two sheets of aluminium screwed using self-tappers or whatever along one edge to the stock. And then to each other along the opposite edge, thus forming a sort of armature around which the fair blade is built? (If I can think of an easy way to draw a diagram, and it sounds useful, I might try!)
Click to expand...

I bought my steering gear, less rudder blade, from Whitlock. The rudder stock was solid 2" rod with two pieces of 1" rod drilled through it at approx right angles. The fabric of the blade was then bonded to those rods.
 
I was forgetting exactly which part the stock refers to. In common with many dinghies, my rudder doesn't have a stock as such - the blade stands within a frame of aluminum plate, and hence stays rigid when the tiller is applied, but can swing up when convenient.
 
I'd have said you could fill all the dings etc on your 'old' rudder with some cheap wood filler. Get it looking perfect. Paint it. You aren't going to use it, just make it look perfect.

Then use it as a plug to create a 2 half mould in GRP and then use the mould to build a new rudder...?
 
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