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Foster Price
07-07-2002, 05:19 AM
Hi Guys

I'm repairing the sheathing on my boat, dynel cloth set in epoxy over strip plank. It has split in a two places below the waterline, these are very small areas about 2-3 inches long.

One of the splits is on the garboard area, and has occured as diesel in the bilge has contaminated the wood and "caused" (?) it to split the sheathing.

Anyhow she is out of the water for other repairs and I figure it would be a good idea to fix these little splits before they become big ones.

My question is - how does epoxy "co-habitate" with diesel?

Currently I'm thinking to sand the area well out beyond the contamination to get a good key, wash it with thinners a couple of times and patch it with glass set in epoxy.

What do you all think?

Thanks - Foster

Ron Williamson
07-07-2002, 06:47 AM
What makes you think diesel did it?
As for repairs you might try the epoxy stickum that is used to fix leaking fuel tanks,then layer over it with regular epoxy and cloth.My local hardware store has about four different flavours for fixing water jackets,mufflers,fuel tanks,cylinder heads,space shuttles(okay,not space shuttles).The stuff I used on my tractor has worked very well,so far.
R

Foster Price
07-07-2002, 04:06 PM
Oh its diesel alright, I could smell it in the antifouling, I'm not saying diesel cased the problem, just that diesel is now THE problem.

Interesting lead though Ron, I'd forgotten that epoxy is used to repair tanks, so I'll get a datasheet on one of those products which should have details on preparation.

Thanks

thechemist
07-07-2002, 07:53 PM
Diesel is volatile, but not very. It will form a film on the surface of any wood it has saturated, and it will interfere with any sort of epoxy product put on the surface, and I suppose the simplest way to explaint how is that not enough diesel dissolves in the epoxy and migrates away into that liquid epoxy, as does more diesel migrate through the wood to the surface being bonded.

If you had an epoxy formulation that dissolved a lot of diesel, then you could apply it and, with mechanical scrubbing of the wood surface, get the epoxy to wet the wood surface.

It will not, however, wet the fibers enough to glue them to themselves well enough to increase the shear strength of the wood any more than its maximum of 200-300 psi. The bottom line is that you might be able to get some particular product [I don't know what without doing tests, but those that are known to glue oily woods have a better chance than those that do not glue, for instance, teak] to stick and perform the low-stress function of a filler, but I would not expect it to glue two pieces of any diesel-wetted wood together with much strength.

Foster Price
07-08-2002, 08:23 PM
Thanks Chemist - advice much appreciated. On the basis of this I will apply a patch that goes well beyond any contaminated area to ensure it is securley bonded, and hope it sticks a bit to the contaminated areas, which are very small - sort of like a bandaid.

Cheers - Foster

PatCox
07-08-2002, 09:04 PM
Chemist,on the same topic, I have a butcher block countertop sold by Ikea, it is beech, with a misture content of 7% to 9% and it has been oiled, treated with a mixture of 50% linseed oil and 50% turpentine. (They call this "wood oil) I would like to glue two pieces together to double the thickness, I plan to glue and screw it; is there a gluethat wil hold this, ordo I have to somehow remove the "wood oil"?

thechemist
07-09-2002, 10:33 AM
I would assume [hope] the wood is not something that has a really extensive open porosity, but I dunno. I would sand it with a really coarse grit [50, for instance] and a palm sander to chew off maybe a thirty-second of an inch, then clean up the surface with 80-120 grit, and expect to see a clean sanded surface. Then, since there may be some grain-angle mismatch with the new wood, use a relatively flexible epoxy adhesive...something with a reputation for gluing oily hardwoods, just to ensure it will be compatible with small traces of oil in the wood.

Use enough glue that some excess flows out everywhere. That flushes out air in the glue line.

Do not clamp the pieces together. Just put one on top of the other, put a weight on top to give maybe a half to one pound per square inch, and a few guides on the sides so the arrangement does not swim sideways. Let it cure like that and clean up the glue drips later.

Some of the Forumites may be able to recommend specific brands of glue that meet the above criteria.

NormMessinger
07-09-2002, 11:13 AM
Gorilla glue claims to bond teak very well. I wonder if a pretreatment with some pretty potent degreaser might remove enough diesel or oil from the surface to enhance the bond. Hmmm. Then there are the powerful solvents in CPES. Why not?

--Norm