What Epoxy for Cockpit Floor Voids ?

[FraidNot]

I have a small void to fill.
Glass with foam-fill floor in cockpit.
Drill small hole at each end of void and squeeze in epoxy with syringe until it comes out the other end.

What brand and model of epoxy?

[ShipShape]

Doesn't really matter what brand - what matters is the volume of "small". Assuming your cockpit floor is cored like the rest of most boats are, "small" is actually quite a bit of volume as far as epoxy is concerned. This is important because even a "small" volume of epoxy gets so hot as it cures that it boils and can damage the fiberglass, and/or your foam core, or even start a fire. If it does neither, you will probably end up with air bubbles in the epoxy from the epoxy boiling - which in the case of a cockpit floor doesn't matter. The way to slow the epoxy cure rate, which reduces the heat from a fast cure, is to use fillers. You can also physically reduce the temperature of the area using ice, or do it in the winter if you live up north - when I lived in Baltimore I had to use a heat gun to force epoxy to cure in the winter...

West System's "Fiberglass Boat Repair and Maintenance" publication #002-550 will answer all your questions. You can get a hard copyfrom www.westsystem.com, and GordMay has posted a link for an electronic version somewhere.

[delmarrey]

Originally Posted by ShipShape

Doesn't really matter what brand - what matters is the volume of "small". Assuming your cockpit floor is cored like the rest of most boats are, "small" is actually quite a bit of volume as far as epoxy is concerned.

This is important because even a "small" volume of epoxy gets so hot as it cures that it boils and can damage the fiberglass, and/or your foam core, or even start a fire. If it does neither, you will probably end up with air bubbles in the epoxy from the epoxy boiling - which in the case of a cockpit floor doesn't matter.

The way to slow the epoxy cure rate, which reduces the heat from a fast cure, is to use fillers. You can also physically reduce the temperature of the area using ice, or do it in the winter if you live up north - when I lived in Baltimore I had to use a heat gun to force epoxy to cure in the winter...

West System's "Fiberglass Boat Repair and Maintenance" publication #002-550 will answer all your questions. You can get a hard copyfrom www.westsystem.com, and GordMay has posted a link for an electronic version somewhere.

Not sure about the boiling part hot maybe, but if you use a filler like West's 403 or 405 to make a wet paste the epoxy will cure slower and not get that hot. Anything more then 1/8 cup in a volume mass will begin to get hot.

Also resins shrink when they cure so making a sprue at the ends will keep the ends full.

The big question is if it's foam cored and you start pumping the stuff in, it might go all different directions. Some cores (foam and balsa) are little squares and the voids are all around each square.
How small of a void are you talking about?

[ShipShape]

Originally Posted by delmarrey

Not sure about the boiling part

Oh my gosh, YES!! You haven't experienced "YIKES!" until a batch of epoxy goes off on you. This is the epitome of the definition that chemists and environmental scientists call a "positive-feedback exothermic reaction": the hotter the epoxy gets the faster the reaction happens, and the faster the reaction happens the hotter the epoxy gets. Within a few very short seconds you are Fully understanding the meaning of "YIKES!"

If you haven't already experienced this by accident, I highly recommend finding out about this in a controlled manner on purpose. Mix up a small amount of epoxy in a cup and let it kick off. Have a flame-resistant place readily available to set down the cup, and be very careful to avoid breathing the smoke.

It doesn't need to smoke to boil, and you wouldn't necessarily know it boiled unless unless you physically get into the cured epoxy. Here is a picture of less than an ounce-worth of epoxy that I knew got to hot, but not hot enough to smoke:

Attachment 20612

The bubbles from boiling were not evident until I sanded off the proud top of the area - fully exposing the bubbles. I knew it got too hot and I might have to drill it out and do it again, but these are temporary epoxy plugs that will be cut out when I remove the teak decks and replace the rotten core, and I think they are structurally sound enough to withstand the light sailing I will do until everything is removed and properly replaced.

[cburger]

Polyester resin, possibly thickened with silica as required.

[Geminidawn]

Why epoxy? Epoxy needs an environment with less than a 13% moisture content to cure effectively and foam or balsa core decks usually fail because of the presence of moisture, dampness and rot. In such a situation I would of injected a single or two part high density polyurethane foam which seeks out moisture in order to cure, furthermore you'll get no exotherm.

[delmarrey]

Originally Posted by ShipShape

Oh my gosh, YES!!

Looks like air bubbles to me. I've used more then 5 gallons of West's and a couple gallons of Pro-brand(?) over the past 7 years and have only had two batches go off on me due to the hot weather. They just smoked but never boiled.

Mixing methods create a lot of bubbles, especially if one is using fillers. I've learned ways of not getting a lot of air in the mix which helps with finish work.
Spinning the mix rather then whipping it keeps down the bubble content.

I've done a lot of injection work filling balsa core damage and the bubbles use to drive me nuts. I'd fill a hole and come back latter and it was still there. So I watched a couple of them and I could see the bubbles working their way up. And they weren't hot. I tried popping them. In small holes it was fine but in large holes it was time consuming.

So, I learned how to mix with the least amount of agitation.


.

[ShipShape]

Delmarry ... I'm not sure how to explain this, but in Florida we have this thing called the Sun, and this weather condition called Hot. It is not a mixing issue - it is the heat. Most days I have to submerge the mixing pot in ice water, and the exact same batch of epoxy injected in a hole in the sun will kick off within seconds and have those bubbles, and under the shade tarp it could take 15 minutes for it to firm-up, and it won't have any bubbles at all. It is quite predictable, and when the epoxy plug needs to be structurally sound I hang a towel to shade the area before the sun can heat up the hull. West System makes slow hardeners for the tropics, and in a few days I'll finish up the last of my 205 and start using 206 - that should help a bit.

But even in your climate curing epoxy can get smoking hot and FraidNot needs to be aware of this. Geminidawn's idea of the polyurethane foam might be a better way for him to go.

[ollie820]

I went through this process a couple of years ago. I had a 8x8 inch void that I filled with west system and microballoons. drilled two holes and injected the mixture in until it came out the other hole.