How do I fix a cracked rudder?

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MacD68

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Hi,

I bought a Mk3 Silhouette a few weeks back and have been giving it a good looking over before launching. Unfortunately I've just discovered a very large crack on the upper leading edge of the rudder, to the the extent that I can see part of the main shaft that passes through the rudder. There is also a smaller crack on the lower rear edge of the rudder.
It certainly doesn't look safe to launch, but I'm unsure as to how best to repair it. I have some marine epoxy filler, but to my inexperienced eye it would need a repair that is a bit more structural and permanent that filler.

I would appreciate any advice and opinions on this, as I will mostly be single-handing and want to be sure I have a boat i can trust under me.

I have some pictures, but not too sure how to post them here - if anybody can let me know how to include pictures I'm sure it will give a much better understanding of the problem I have.

Thanks,
MacD.
 
Hi,

this as you probably know by now is serious. it will need to be laminated .

Sand it all right down to the glass GRP. Then start laying iit up with some woven rovin and resin, layer by layer. Once it is set. Sand it all till smooth. Wash thoroughly. When dry you will have to apply gelcoat/flowcoat.

Good luck- If you can seek a professional for on site advice and possible help.
 
MacD68 said:
worth a thousand words
Click to expand...

Filler is not going to be any good, at least not on its own

You will have to use resin and glass cloth to cover the cracks and rejoin the halves together soundly

BUT

It looks as thought there may be a steel structure inside the rudder which is rusting and forcing the two halves apart.

If that is so you may well have to split the rudder apart, deal with/ re-fabricate the inside structure then refit the two halves of the shell bonding them together with epoxy and glass cloth
 
VicS said:
Filler is not going to be any good, at least not on its own

You will have to use resin and glass cloth to cover the cracks and rejoin the halves together soundly

BUT

It looks as thought there may be a steel structure inside the rudder which is rusting and forcing the two halves apart.

If that is so you may well have to split the rudder apart, deal with/ re-fabricate the inside structure then refit the two halves of the shell bonding them together with epoxy and glass cloth
Click to expand...

Yes this is quite likely the cause, or impact with something solid, or both. Best investigated, repair properly, and have confidence in your rudder.

Use a grinder to cut a channel all the way around the rudder and open it up. It will need to be 100% bone dry and cleaned with acetone prior to re-assembly.

If you do this you can inspect and replace/repair the metal internals and epoxy it all back together with woven glass cloth as above

There are lots of resources on the epoxy suppliers websites.
 
There are lots of resources on the epoxy suppliers websites.
Click to expand...
in particular on the Wessex resins website.

My choice would be epoxy resin and biaxial cloth. ( no need to flo coat it. just prep and antifoul) Expensive though!

Cheapest would be polyester resin and chopped strand mat. Just like you'd patch up an old car.
 
Hi,

Thanks for the replies. I guess it confirms my initial fears.
There does seem to be corrosion on the inner structure, so that will need looked at. I'll have to see if I can drop the rudder and have it looked at. I haven't done any work with cloth/resin previously, and though I'd be willing to try I don't think that something as critical as the rudder would be the place for trial and error.
MacD
 
MacD68 said:
Hi,

Thanks for the replies. I guess it confirms my initial fears.
There does seem to be corrosion on the inner structure, so that will need looked at. I'll have to see if I can drop the rudder and have it looked at. I haven't done any work with cloth/resin previously, and though I'd be willing to try I don't think that something as critical as the rudder would be the place for trial and error.
MacD
Click to expand...

Old but useful esp if opting for polyester http://www.bluemoment.com/downloads/grp_repair_manual.pdf
 
Our silhouette had a 1 inch rod passing through a tube to make the stock
There were 2 straps made from waterbar bent to a "U" shape & welded to the rod
A piece of 1 inch ply formed the rudder blade & was bolted through the straps which went either side of it
Point being is that you could easily make a completely new rudder to save the hassle laminating parts
I damaged the rudder when it slipped off the trailer when launching one year( i was 12 & was doing it with a couple of friends) & my father jacked the boat up on bits of rock on the beach tipped the boat forward & removed the rudder stock.
Took it home , made a new one that night & had it back in the boat the next day
Mind you he was pretty resourceful -in 1959 he built the whole boat from scratch (in wood )to launch in under a month
I think the No was 1494 if anyone out there has it
 
I would build a new one out of 316 stainless for the shaft and the tangs, face with marine ply, and coat with epoxy resin. Screw the ply faces together using epoxy glue (epoxy resin + colloidal silica (406 filler in West System) to stick two sides together and take up any gaps around the tangs. Use a hand plane to shape the faces. Easy.

The chances are that the stainless steel in the old rudder is unreliable. Apart from the obvious visible corrosion, the shaft itself may have corroded with itself. I have cut rudder shafts up that have been cored out like electrical cable.

The damage from the photos is typical of spade rudders that have had a sideways force on them, either from say grounding or catching a mooring line, or net.
 
I had the same on my Leisure 20. The rudder was removed and then split into 2 parts. This showed that the tangs welded onto the shaft had failed. These were re-welded and the foam was removed from each panel of the rudder. A retired boat builder then glassed it all back together so it looked like new, recycling the shaft and the panels of the rudder. Unfortunately l was not present to witness how this was accomplished.
My point is whichever way you tackle it do it as it will give you great piece of mind especially when experiencing some weather helm.
 
As said it really needs major surgery. Don't despair however as you will find that GRP work is quite simple and almost a pleasure.
I would suggest you start by splitting the skins off the rudder and I think the way forward will then become obvious. The shaft and tangs may need repair or replacement. If it just rust cuasing the assembly to expand then a clean up and rust treatment may be all that is needed.
Then if necessary replace the foam either with foam sheets or mix up foam. You then sahpe the foam and lay up the GRP or try to glue ariginal sides back on. You should end up with 6mm plus of GRP over the foam. Lay strips of cloth around the elading edge particularly and if possible the training edge. This will make a rounded trailing edge so additional filler or f/g might be needed to get the fine trailing edge.
Come back with more questions when you need. Do give yourself some days to repair as you allow layers of GRP to harden before you fair it and fill it. good luck olewill
 
Definitely split the rudder.If the stock is not stainless or if it is corroded make a new one.Don't use foam for the inside but make it solid fiberglass.It won't be as hard as it may seem. and you'll have a rudder you can depend on.
 
As others have said you need to split the rudder.

I would not use polyester resin as it does not bond well with fully cured polyester resin which is almost certainly what your rudder is. Use epoxy.

Working with glass cloth and resins is not rocket science and it is always possible to grind off anything you don't like and redo it.

West System offer some good guides including one on rebuilding a rudder. See http://www.westsystem.com/ss/boat-repair/
 
TQA said:
As others have said you need to split the rudder.

I would not use polyester resin as it does not bond well with fully cured polyester resin which is almost certainly what your rudder is. Use epoxy.

Working with glass cloth and resins is not rocket science and it is always possible to grind off anything you don't like and redo it.

West System offer some good guides including one on rebuilding a rudder. See http://www.westsystem.com/ss/boat-repair/
Click to expand...
I've read the article and they advocate the use of foam which IMO is not a good idea.There's an article on PBO by Andrew Simpson about the building of his boats rudder in plywood and epoxy.
 
Simplest (and best) way is ply and epoxy for that size rudder. The stock and tangs will almost certainly be mild steel and when you split it you will find a mess of rotting foam and rusty rubbish. Take measurements and the details of the top and bottom of the stock and get a shaft made of 316 stainless with two tangs welded at right angles. Have them drilled with 6mm holes to take screws to hold into the ply blade. Cut a groove top and bottom where the shaft goes into the blade and fill with epoxy. Make the blade out of ply which will be easy to shape and then sheath in glass cloth and epoxy. Look at replacing the top and bottom bearings with Delrin bushes. Rudder made like this will see you out!
 
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