epoxy bite to wood
 

What is a proper grit to prepare "A" faced ply (birch if it makes a
difference) for epoxy coating prior to painting.

Ron

epoxy bite to wood
 

Now it is time to lay glass.

Haven't had a wood/glass bond let go yet.

I take it that glass directly on wood doesn't hold well? Why doesn't it
adhere as well without glass as with?

epoxy bite to wood
 

"JS" writes:

I take it that glass directly on wood doesn't hold well? Why doesn't it
adhere as well without glass as with?

I don't have a clue. I described what works for me.

YMMV



--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures

epoxy bite to wood
 

JS wrote:
Now it is time to lay glass.

Haven't had a wood/glass bond let go yet.


I take it that glass directly on wood doesn't hold well? Why doesn't
it adhere as well without glass as with?

It is better to put down a coat of epoxy first to fill pores so they
don't drag resin out of the glass. Epoxy adheres to most plywoods
extremely well but a light 2oz scrim of glass keeps the face veneers of
the plywood from checking and makes a more stable surface for paint.

AS to the original question, it depends on what you plan to do but the
grit for birch is not all that critical. For a clear varnish top coat I
would sand to the birch to #120 grit, apply the epoxy and scrim, fill
the scrim and sand to #180 grit. If using a marine paint I would go to
#80 and #120 respectively then apply the recommended high build primer
and sand to what ever the paint system recommends.

You would need to stay with a coarser grit for tougher to bond woods
like white oak and teak because you have to rely more on the mechanical
surface bond.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

epoxy bite to wood
 

Glenn Ashmore ) writes:

You would need to stay with a coarser grit for tougher to bond woods
like white oak and teak because you have to rely more on the mechanical
surface bond.

I've read that the reason epoxy bonds well to wood is that it bonds at the
molecular level, the mollecules of curing epoxy being the same size or
something as the molecules of wood. So long as the surface of the wood is
clean and dry it doesn't need to be sanded for adhesion, except as noted
above in the case of woods with incompatible resins. Otherwise you only
sand if you want a smoother surface for the finish.

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epoxy bite to wood
 

epoxy bite to wood
 

On 8 Jul 2003 14:37:46 GMT, (William R.
Watt) wrote:

Glenn Ashmore ) writes:

You would need to stay with a coarser grit for tougher to bond woods
like white oak and teak because you have to rely more on the mechanical
surface bond.

I've read that the reason epoxy bonds well to wood is that it bonds at the
molecular level, the mollecules of curing epoxy being the same size or
something as the molecules of wood. So long as the surface of the wood is
clean and dry it doesn't need to be sanded for adhesion, except as noted
above in the case of woods with incompatible resins. Otherwise you only
sand if you want a smoother surface for the finish.


I don't think that is quite right, as in molecules bonding?
The word attraction, or resistance to surface tension, may be the
better term. - So you looking at wetting agents, and surface tension.

As in bonding, - would mean the epoxy is disintegrating, or migrating,
as in solution - which is want you wouldn't want.
What you would want is an ability to penetrating through the cell
walls. - As in its saturation ability.
In other words the chains can slip through the holes, and fill up the
cavities, so you wouldn't want, oils and waxs in the timber, but it
can take in a bit of water, so a small amount of water in the timber
as a wetting agent can help its movement.

If you try to separate two layers, you will see as it tears out the
fibers, as to its penetration ability - and you could test on various
formula -( lack of fillers ) As the timber is seen as just another
fiber type filler.
As for sanding, its not that big a deal, - but that's relative to the
saturation point of your mix - and any fillers then added.- the more
filler the more sanding, the less saturation.

epoxy bite to wood
 

I have found that if you REALLY want something to stick and it's
important, it will not stick. However, all those little drips and gobs
that seem to end up where you don't want them tend to be there
forever...go figure!!

epoxy bite to wood
 

epoxy bite to wood
 

epoxy bite to wood
 

What is a proper grit to prepare "A" faced ply (birch if it makes a
difference) for epoxy coating prior to painting.

You could sand the surface with something im the 180 - 220 range, maybe even
coarser, but if the surface of the wood is natural, clean and smooth, I believe
you will get a good bond between the wood and the epoxy even if you don't sand.

Almost all my experience is with the Gougeon brothers WEST System epoxy
(http://www.westsystem.com/). However, I believe several of the other epoxy
systems are similar. WEST was developed initially for coating wood surfaces..
the WEST stands for something like Wood Epoxy Saturation Technique.

On plywood or wood, I have put two or three coats of WEST epoxy on. You can
either put on the second and third coats once the previous coat is hard enough
not to run, or you can wait until it cures and sand it. This sanding is both
to get a good bond between the epoxy coats and to smooth the surface for the
next coat. I believe the WEST system literature says that if you recoat within
24 hours you do not need to sand the previous coating.

I believe that if you are coating the surface while it is horizontal, you may
be able to get a thicker coat on without it running, and get away with only one
or two coats.

The instructions that come with the paint you are using should tell you how to
prepare the epoxy surface for painting. Normally I would let the epoxy cure,
and perhaps leave it a few days to be certain I have a complete cure, then sand
with something in the 220-400 range to get a nice smooth surface but with some
texture for the paint to stick to.

Some epoxies, under some circumstances, get a coating called amine blush as
they harden. You are supposed to wash and or sand this off before putting any
more epoxy or any paint on the surface.

Good luck,

Alexander Meller

epoxy bite to wood
 

So many ways to do the same thing reinforces my experience that epoxy is
hard to screw up.

Thanks for all he replies.

Regards, Ron

PS to Scotty, I'm only going to epoxy coat the outside and just paint
the inside. I think that will overcome our mutual concern about
encapsulation.

epoxy bite to wood
 

epoxy bite to wood
 

How's the boat coming, Al?
Darn, I like that design.

Jim

Al Gunther wrote:
snip

epoxy bite to wood
 

"Alexander A. Meller" wrote:

What is a proper grit to prepare "A" faced ply (birch if it makes a
difference) for epoxy coating prior to painting.


-----

I have often wondered if plywood surfaces aren't contaminated with the glues etc
used to manufacture the plywood. If so, I would assume a solvent wash and or
sanding would remove? Anyone have an idea on this?

Also, how about adding say 10% solvent the the first coat of epoxy (either with or
without the cloth) to aid in penetration of the epoxy into the wood.

Paul Oman
www.epoxyproducts.com/marine.html

epoxy bite to wood
 

"Paul Oman" wrote in message
...
I have often wondered if plywood surfaces aren't contaminated with the
glues etc
used to manufacture the plywood. If so, I would assume a solvent wash and
or
sanding would remove? Anyone have an idea on this?

When building a 10ft lapstrake dinghy, I mostly wiped the surfaces with a
solvent. But many times I didn't, but never experienced any problems.

Also, how about adding say 10% solvent the the first coat of epoxy (either
with or
without the cloth) to aid in penetration of the epoxy into the wood.

Don't. You thin the epoxy, thinner evaporates and leaved thinned porous
epoxy behind. Normally, epoxy penetrates the wood sufficiently, especially
at higher environmental temperatures. If you really want good penetration,
heat the wood first and then, while cooling down, apply the epoxy. It gets
warm and thin and get sucked because the trapped air in the wood contracts.
Do not heat the wood when the epoxy is applied. You'll get a lot of air
bubbles.

Meindert

epoxy bite to wood
 

Ron Thornton wrote:
: What is a proper grit to prepare "A" faced ply (birch if it makes a
: difference) for epoxy coating prior to painting.

: Ron


Be careful regarding your choice of paints; I did the above
with epoxy then interlux bright-side (brite-side ??) IT DID NOT DRY.

Call to interlux tech support said that the epoxy posioned the
interlux drying catalyst. The guy's rec was to scrape it all off;
I didn't and it is now 4 months later dry enough to be useable.
(after all, you don't
need a catalyst for a chme reaction if you are willing to wait!)

Note: I did clean off the amine using h2o, detergent and de-waxer.


--

almus kenter
`` Pluralitas est ponenda sine neccesitate''