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Structural epoxy
A very important part of building a Chog Boat, is the epoxy. The
type of epoxy used is as important as the marine plywood, and
the hardwoods that go into building the hull. I personally use
(System Three) not because I think that it is better than the
others, but I seem to have less reactions to (System Three) than
(West System).
Use the Good Stuff!
Use name brand epoxies only. Don't use off brand resins. The prices
may be inviting, but the quality and strength may not be conducive
to boat building. I have heard of some severe reactions to these
industrial resins. These resins are meant to be used under controlled
environment, not available in the home shop.
Glue and Leave
When coating or gluing, especially large areas, glue and leave!
Warm the shop and all to be coated then turn the heat down prior
to coating then leave the building. The curing process does not
need you to be there to happen.
Use Protection!
At very least use gloves. I use cheap vinyl gloves and sleeve
protectors. If you do not have sleeve protectors, wear a long
sleeve shirt then tape the cuffs with 1 ½" masking
tape.
Work Clean!
Many problems related to using epoxy, can be greatly reduced by
working clean. Extra care taken when making fillets or applying
resin can reduce the hazards and if you clean up your drips and
runs before they cure, could save a bunch of time sanding.
Fillers
A lot of confusion occurs when choosing fillers and additives
used with epoxy resin. Structural fillets, i.e. as used when bonding
two pieces of wood, require a simple formula of 1 part col. Silica
and 2 parts wood flour. Blended with epoxy resin until a peanut
butter Consistence is achieved. This is also a good gap filling
glue when mixed to a mayo like paste.
Col Silica
Makes a very hard surface, and a strong glue joint. This additive
helps make the mix texture Smoother. Avoid breathing the very
fluffy particles.
Wood Flour
A very versatile filler, strong and cheap, mixed with silica it
makes a strong glue and a very Good fillet joint.
Milled Fibers
Add when gluing, adds strength to most any joint. Scarfs are a
good place to add fibers.
Graphite Powder
Add to last coat on the bottom. " I question if it's needed
"
Microballoons
Phenolic microballoons and plastic microballoons are a couple
of additives used to make A lightweight and easily sanded filler.
My favorite Is west system # 410 , it works easy and is simple
to use. When its mixed correctly it looks like bondo (body filler).
Taping Joints
Structural joints should be taped with reinforced tape and filled
with e/resin. Non structural corners can be taped with 6 to 8
oz tape, and fill the weave.
Round Over
Maybe this doesn't belong in the epoxy page, but it's important!
All inside and outside corners should be rounded w/fillets and
outside joints rounded over (router works well) This helps prevent
cracking and wearing through of the finishes.
Jerry Mathieu
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