Epoxy Drips

[rturbett]

I am looking for info on how to get a smooth epoxy finish, and the only answer I see is use a female mold or sand, sand ,sand.

I'm working off a male mold, and have a layer of 10oz. cloth on the outside of a core. Of course, each layer of epoxy I put on has some sag by the time it cures. I have added some different fillers to try to minimize this, but much of the surface is vertical.

The best luck I have had is with prewarming the hull with a heat gun, using "fast" hardener (west) with a little 410 filler added. There was still some ridges by the time it was cured, but much less than previous attempts.

I have also used a trick my brother taught me when he was glasssing RC airplane wings. Hold a heavy duty razor blade perpendicular to the surface, and scrape along. This takes down the high points, making sanding much less of a project.

I would like to put another layer of epoxy on before going through the painting process. I will wait untill it comes off the mold, will lay it on its side, and do one side at a time.

I still have another hull to do. I would appreciate any tips or techniques that have worked for you to make this process more efficient.
Thanks,
Rob Turbett

[Roly]

I had this delemma when I wanted to put sealer coats over the west 410 filler. Best result was by doing a flow coat over the hull by using at least 0.5 litres per sq metre of epoxy per hull area. This enables the epoxy to self level. It is a tricky operation requiring fast hardner,dust free item, and a hot air gun to burst any air bubbles in the film. Pour the epoxy on and spread rapidly with a
wall paper brush (cross strokes) then even out using longiitudinal strokes and then leave. Do not over brush.
I did half the hull at a time so as to be able to reach the keel.



I now have at least a 1mm film build of neat epoxy over my fairing compound. (to top boot stripe only)
G'luck with it.

[rturbett]

Thats impressive!
Just to be clear, you heated the epoxy after it was on to the point where it started to cure, holding itself in place?

[Roly]

The paint stripper gun is only to expand the air & burst any bubbles that remain in the film after the longitudinal brush strokes.Stirring the hardener in often entraps air and brushing out only removes a portion of it. Also it allows air in pinholes to burst and suck the resin in. We have used this procedure on solid table tops with a butane torch and a naked flame, much to any onlookers alarm . Neat, 100% solids epoxy has no solvents, and does not burn readily. Do keep the flame moving though or you will "cook" the resin.

On the boat above were working mid-summer at 27deg C (80F) which is ideal for a fast set up. We still used fast hardner which meant we had to work fast. Obviously a fast setup is a must or the flow is excessive and "tears" appear.

In your temps I guess you would be best to heat the hull to at least 68F for
a good flow and not too longer setup. This is not as hard as it sounds with an inverted hull as the shape keeps the warm air in.
You do waste probably about 20% as the film "stretches" uniformly under gravity (especially on topsides) and runs off, so allowing for a 20% loss I should have obtained a 0.4mm per coat. Maybe a little less on the turn of the bilge.
It was a vastly better result than rolling it on and the resultant stipple and runs.
.

[rturbett]

I am working indoors, so temp is not too much a problem. I used a biscuit scraper (soft plastic) to spread on a thin coat. Warming the hull made it spread "verrrry" nice. Next coat I will try the additional heat gun trick.

Isn't there flamable solvents in the hardener? I'll stick to the heat gun vs. open flame!

[Roly]

Isn't there flamable solvents in the hardener?

Not in West 205,206,207. Can't vouch for others.(100% solids includes the hardener) Heat gun is more user friendly anyway.
If you cant brush out the epoxy it needs heating in bulk (electric blanket or incandescent light box) before you put in the hardener. Also the hull must be heated as well or it will become unworkable as soon as it is spread and you will not get the self leveling flow out effect.
In your "neck of the woods", getting epoxy to flow may be a summer procedure.
Laminating here in winter we heat the resin to 70deg F.
Heating the hull needs to be started at least a day before or you may experience out gassing. Flow coat or laminate just after peak temp of the day
to get the slight vacuum of slight cooling to your advantage.

[thill]

I'm not particularly experienced, but when I had a similar experience, I got the solution from another board.

1. First, you wet-sand the existing epoxy very smooth. Take your time with this part!
2. Then spread a VERY thin layer of epoxy with a rubber squeegee.(sp?) This coat is literally paper-thin, just enough to "wet" the surface, but not enough to run. This is a lot easier than it sounds with a squeege.

If you do it right, you are done! If you mess up a spot or two, don't worry, sand the affected area as soon as it is hard, and apply a very thin layer to the area, pulling the edges very tight.

I applied two sheen coats like this, the second one as soon as the first one hardened, and it really came out glass smooth! Very much like the picture above. SO much easier than trying to do it in one heavy coat!

The rubber squeegee trick works!

Hope this is helpful.

TH