Boat Builder Central - Builder Forums

Can epoxy be thinned by adding a solvent?

No

Agreed - no. Instead try warming it up to make it runnier. Do it before mixing (of course!) but remember you also have a shorter potlife

Richard Woods

I have a hardener to mix with normal 25 min hardener and to prolong this time. This hardener is like water but needs whole day for epoxy to become hard. The epoxy mix is thin like varnish. German stuff but I believe you can get something similar in US.

Thinned epoxies exist but they are not adequate for boat building. They are fine for a protection coat like on furniture but don't have the mechanical properties we need.
Here in the US, there are some cheap epoxy brands that are thinned.
I don't know the German resin you use, it may be excellent.

Many years ago, I was guilty of specifying a thinned epoxy for a priming coat.
At that time, it was common use, it was mentioned in the Gougeon book but also, the resins were much thicker. I stated that you could add 5% of lacquer thinner. With today's thinner epoxies, I would not do it.
And that was only for a coat to prime the plywood, never for any fiberglass or glue work.

Thanks!

In order to get a decent coat of resin/graphite applied I'll have to warm it up. I'll also run the heat in the shop the night before in order to get the hull warmed up a bit too. Heating the shop is expensive but warranted in this case in order to do a good job.

As I mentioned in another thread I've done the graphite thing before a couple years ago. That came out fine so maybe it was a bit warmer then than now.

If thin epoxy is desired, then a thinner epoxy product should be purchased, already tested and formulated as such by the manufacturer, and approved for these designs. There are too many potential chemistry quirks to try to homebrew a good and safe result. Leave it to the pro formulaters. The designers at Bateau review the physical characteristics of the cured epoxy products they spec and sell for the designs here. Its best to stay within that building envelope.

Pictures Jerry? Progress?

[edit -- oopps. Too slow. I'm still only typing with one finger at a time, but slower than usual today. One wing in a sling. This doesn't let you off posting pictures soon. ]

No pictures. The hull is currently in the corner of a dark basement so you wouldn't see much anyway. Anyone is welcomed to drive up and take a look though. Be advised you'll need a good 4WD vehicle to get up my drive.

Once it's flipped I'll try to move it toward the outside doors. Might be able to get a decent pic there.

...and bring beer.

So, right now it looks something like this?

Got the first coat of epoxy/resin sanded. Figured it would make more of a mess than it did....

The plan for the next coat is to:

Warm the shop up to about 60F or so.
Throw a drop cloth over the hull with an oil filled space heater underneath to warm the surface overnight.
Set the epoxy/hardener jugs by the wood stove overnight to warm them prior to mixing.

Any other tips that might be helpful?

Any other tips that might be helpful?

Yes Dont do this ........

Throw a drop cloth over the hull with an oil filled space heater underneath to warm the surface overnight.

Over the years there have been more than one instance of people have coating failures due to residue from oil heaters. The epoxy would probably be OK, but any paint you put on in the future might have serious issues

This isn't a kerosene heater. It's uses warmed oil in sealed tubes to conduct the heat. Looks like an old-school radiator style heater but plugs into an outlet.

AH Ha..... then your golden

Yea...golden
Well just have to see how the next couple coats come out.
There's no hurry....I ned to buy three more sheets of plywood to finish the boast. Trouble is 8' snow drifts block access to the shop door and even if I had access my trailer is buried in snow.


Its been a tough winter..