Potting around large openings in deck?

[jrd22]

I have all the deck hardware removed and the teak off the decks (phew, that was no fun) so now it is time to pot all the holes in the balsa cored deck (no rot!). The normal round holes should be no problem, apart from the enormous number of them. My question is what to do with the deck prism holes that are approx. 4" X 8" rectangles. I won't be able to just tape over the bottom of the hole to support the epoxy because of the size, and because of the location it would be hard to put boards under them (3). I don't really want to fill the entire area with epoxy which I will have to cut out anyway so has someone figured out a good way to do this? Would something like GitRot penetrating epoxy work? Thanks for any advice.

John

[sailingdog]

JRD22-

What you should do is ream out the balsa core around the bigger openings and then fill the gap between the two layers of fiberglass with a good solid coating of thickened epoxy, after "painting" it with plain epoxy. This will do two things. First, it will seal the balsa core from water penetration. Second, it will make the deck edge around the hole stronger and more resistant to compressive forces that the fasteners will exert on the deck there.

The thickened epoxy adds strength, the "painted" regular epoxy will soak in and help prevent the balsa core from wicking the epoxy out of the thickened mixture and weakening it.

[Freesail99]

I understand the issue your having around the 4 inch deck prism holes. If the area is dry and shows no rot, I think you can "paint" the cored edge and seal it from moisture, with epoxy. 5 or 10 years ago, no one was even doing that much with epoxy when re-bedding deck fittings. If you see any issues with the hole by all means do what sailingdog suggested.

[PorFin]

JRD,

4x8 is a fairly big opening -- do you intend to replace the prisms, or cover/fill in the openings completely?

PF

[sailingdog]

PorFin-

I believe he's just pulling up all the deck hardware to re-bed it all again.

[NOLAsailing]

The proper way to do this is to ream the opening around the prism cutout back just a little bit. I do not recommend simply brushing with epoxy.

Use heavily thickened epoxy (I would recommend colloidal silica, #406 if you use West System) to fill the gap you've vacated the core from. You need the epoxy to be thick - mayonnaise consistency - to keep from sagging out of the gap. Try and smooth it as best you can as it is a little bit hard to sand.

This will provide adequate protection for your core and is essentially the same as potting a smaller hole.

[whroeder]

Originally Posted by jrd22

My question is what to do with the deck prism holes that are approx. 4" X 8" rectangles. I won't be able to just tape over the bottom of the hole to support the epoxy because of the size, and because of the location it would be hard to put boards under them (3).

When patching a large area in dry wall, the trick is to place one or more small boards behind the wall with a temporary line to a board on the front. Then the patch can be placed in and the outside spackled.

How about the same: Epoxy the edges and a backing. Remove the front support. Fill and finish.

[Freesail99]

Originally Posted by whroeder

When patching a large area in dry wall, the trick is to place one or more small boards behind the wall with a temporary line to a board on the front. Then the patch can be placed in and the outside spackled.

How about the same: Epoxy the edges and a backing. Remove the front support. Fill and finish.

Great dry wall tip, but you misread the OP's question. He is re bedding deck fittings, not patching holes.

[jrd22]

Let me explain further. I know how to pot regular holes with epoxy, the issue here is that I have three 4"X8" by 1 1/4" rectangles and I just want to fill around the edges about a 1/4" with epoxy, I would rather not have to figure out how to support it on the bottom and fill the whole thing with epoxy and then cut out 95% of it and throw it away. I thought about removing about 1/4" of core all around and then using duct tape to seal the edges all the way. I could inject epoxy through 1/4" holes drilled around the top edges, but I wouldn't be able to thicken it much at all if I had to use a syringe to inject it with. I also wouldn't end up with straight edges because the duct tape would bulge out somewhat, although that probably isn't a big problem. The other option, like Freesail suggested, is to just paint the edges with epoxy and bed the prisms well. Thanks for your suggestions.

John

[sailingdog]

JRD22-

If you're using thickened epoxy, it should stay in place pretty well by itself.