repairing hole in rudder - what's best

[fjweaver]

repairing hole in rudder - what\'s best

The boat came out yesterday & and the rudder's half full of water. It happened last year & it seems the repair I made hadn't worked.
About 5" below the waterline there's a hole about 2" across - I'm guessing it's from manufacture & used for filling out the rudder with expanding foam.
I repaired it last year with a marine filler designed for underwater but there were cracks all around the hole - and I guess this is where the water's getting in.
What I'd like to know is what's best for repairing it. I haven't used it before but I've heard of epoxy mixed with micro-balloons.

grateful for any suggestions or recommendations
thanks
Frank

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[boatless]

Re: repairing hole in rudder - what\'s best

Frank, Hi

Don't want to depress you, but the manufacture of yacht rudders is a truly agricultural process.

Generally, the two halves of the blade are laid on the floor, part-filled with a mush of resin and chopped strand mat. The stock is laid in one half and the other half squeezed down on top.

Sometimes an attempt is made to fill the remaining voids with foam, sometimes not.

As you can imagine, the join around the edges is, at best, suspect. Even if it were perfect, the join betwixt stock, blade halves and mush at the point where the stock exits the blade is going to flex and open slightly.

So, trying to keep water out of the blade is really a non-starter. (IMHO). The only alternative is to completely fill it with something else.

But, back to your question. As with any grp repair, you have to cut back until there are no more cracks and a feathered edge. An epoxy/balloon mix will be fine, but it's essential that the bonding surfaces are competely dry.

It would be worth exploring down into the foam though. If one of the tangs (pieces of flat bar welded to the stock) is flexing, it could be pushing the foam about and causing your previous repair to come under stress. If so, the part solution is to replace that local area of foam with more resin and glass. Please pm if that's the case.

John

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[chippie]

Re: repairing hole in rudder - what\'s best

Micro balloons are more of a fairing compound than a waterproofer. If you can dry things out, grind back and use epoxy and glass cloth for patching and then the microballoons for fairing the final shape.

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[snowleopard]

Re: repairing hole in rudder - what\'s best

agreed. also if using resin to fill a volume it must be reinforced. the best way is to mix in chopped strands (short lengths of glass 1-5mm in length. evil to work with but effective.

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[oldsaltoz]

Re: repairing hole in rudder - what\'s best

G'day Frank,

First you need to open the hole [grinder job] and remove all traces of cracks as stated above, look for thin dark lines to indicate the depth and direction as you grind, when you think you have them all, take another half inch off and feather the edge to a shallow angle to expose a good clean area for bonding.

Now do nothing till you are 100% sure it is dry, epoxy will not bond in high humidity, so any sign of water will result in waste of your time and moolar.

When dry, clean up with a light sanding and wash with plenty of acetone and clean white cotton rag.

You will need closed cell balloons if you plan to use them, but I would use epoxy fibre mix available at fibreglass distributors, mix to a toothpaste consistency and take care not to trap air behind it; note, this stuff is tough, so make sure it stays below the feathered edge, or you will have to grind and wash again.

When this has cured [next day], have another clean up and start applying some cloth, Not Chopped Strand Mat, CSM, as it will hold too much resin and weaken the repair. Use only mat that is designed for epoxy resin, a 250 gram crows foot weave would be good. Cut you mat to size prior to mixing your resin, aim to build up using small patches in the lowest areas first; try to finish just inside the feathered edge, but don't worry if you go over it a bit. When cured, clean up and remove any and all material that is above the last quarter of the feathered edge, now paint this area with at least 3 coats of resin, wet on tacky is ok to save time and sanding. When cured, apply closed cell balloons or 'Q' cells to fair the hull. sand it to the required level, then remove just enough to apply another 3 coats of resin. The repair is complete.

If you suspect the leak is at the interface between rudder stock and top of rudder, you can grind off the top bit around the shaft and prior to re building this section, slide two '0' rings over the shaft with a little Vaseline between them, this will keep the resin out so they will hug the shaft, but be held in place by resin on the outside. I have been doing this on rudders for some years now and have yet to see one leak.

I hope this helps.

Andavagoodweekend.......



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