Rudder has damaged back of boat, help needed ASAP

You don't need to put fibres in the epoxy bonding mix. An ideal mix would be a bit of colloidial silica to thicken it so it doesn't run out from the bond and microballoons or glass bubbles to bulk it out. The laminate should be roughened up with  80 grit and be clean and dry. Try to do a good fit on the plywood to minmise the amount of epoxy required. The wood should have a wet mix of epoxy applied and allowed to tack off before fitting. The end grain will soak up more so give this a second application just before it goes in. Try to get some clamping pressure on the plate if possible with a temporary strut in the tank while the resin cures.

Hi Matt, this is a common problem on contenders of that age - it happended on 473, the one I had before 620.  The most widely used fix is what has already been suggested: a plywood pad coated in epoxy and clamped well on, and  big washers.  It should at least be accessible through the transon hatch.

Edited by winging it - 22 Jun 12 at 10:18am

i can access it from inside to speak right need to the pintle i have a port hole so can get my hand inside to feel the area. Not sure if its the gel coat that has cracked or deeper. How would i check this?

I'd want to investigate this quite carefully I think. Doubtless a piece of ply glued on the back would hold it together for months, maybe years, but if the cracks are right into the main structure as opposed to just the gel coat then I think I'd be inclined to do something a bit more sophisticated. I think maybe I'd grind off the gelcoat over the whole affected region anyway just to see what's going on.

If turns out to be just the gel coat cracking off round the holes wih a bit of water ingress then a ply pad on the back to spread the loads and new gel coat will be good. That will stop water getting into the laminate and promoting osmosis and so on. If on the other hand the underlying fibres and resin are cracking up then I guess cut back to good over a larger area and new fibre and resin right over the whole area. I'd use epoxy I think, not sure that polyester really sticks well to old polyester.

It's probably best not to use epoxy on it, as that boat is probably polyester.  Is there room to get into the tank, remove the pintiles & gudgeons, & glass in a plywood pad.  This should stiffen the area around the rudder fittings.