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Recommended Expoxy Thinner
Posted:
Fri Aug 05, 2022 1:40 pmby Onajourney
Anyone have a recommended epoxy to use for sealing the plywood before skinning with aluminum? Also, preferred thinner and ratio to use to roll on? There is a ton of dialog on this here but I can't find these specifics. Thanks
Re: Recommended Expoxy Thinner
Posted:
Fri Aug 05, 2022 5:51 pmby Capebuild
I'll share my experience which may have nothing to do with your "technique" of applying the aluminum.... I used contact cement to apply my aluminum to the ply sides.
Prior to applying the aluminum I coated the ply with 3 coats of urethane. Big mistake. I had to wind up sanding it all off back down to the bare wood. So depending on how you're applying your aluminum (and whether you float it or not) you may want to give some thought about whether or not the wood should be sealed. My 2 cents.
John
Re: Recommended Expoxy Thinner
Posted:
Fri Aug 05, 2022 6:51 pmby Onajourney
John- Thanks. Like so many things here, there are numerous ways to do things. My plan is to epoxy ~12" around all corners (my is a squaredrop) and use a minimal amount of contact cement to assist this one man crew to skin the aluminum. SO you are saying do not epoxy anything? I am ok with that but Tony beat into my head to epoxy everything. If you had to do it again, what would you do?
Re: Recommended Expoxy Thinner
Posted:
Fri Aug 05, 2022 9:43 pmby tony.latham
Onajourney wrote:John- Thanks. Like so many things here, there are numerous ways to do things. My plan is to epoxy ~12" around all corners (my is a squaredrop) and use a minimal amount of contact cement to assist this one man crew to skin the aluminum. SO you are saying do not epoxy anything? I am ok with that but Tony beat into my head to epoxy everything. If you had to do it again, what would you do?
If it were me, I would use Raka thin set epoxy and float the aluminum.
Tony
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Re: Recommended Expoxy Thinner
Posted:
Sat Aug 06, 2022 6:52 amby Capebuild
If you plan on "floating" the aluminum, then I'd follow Tony's lead. If you are planning on using contact cement to adhere the aluminum to the ply (not floating it) I'd not seal the wood. I had spoken with 2 tech reps from Wilsonart after I had sealed the wood with urethane and both had said the urethaned surface would compromise the bond. I suppose the contact cement is adhering to the urethane and not soaking into the ply as it should (if the ply were uncoated) .....so now the contact cement could just pull up the urethane and separate it from the ply. So I guess it all depends on how you plan on applying the aluminum.
Re: Recommended Expoxy Thinner
Posted:
Tue Sep 13, 2022 8:34 pmby Millerrep
Thinning epoxy is not suggested. I understand the epoxy everything to seal it. No need if are using aluminum skin. Maybe just the edges where the aluminum seams together.
Re: Recommended Expoxy Thinner
Posted:
Tue Sep 13, 2022 10:12 pmby halfdome, Danny
If you decide to glue your aluminum on, power sand the back side of the aluminum with 80 grit sandpaper to give it a tooth for the contract to adhere to.
No sealant of any kind should be used on the wood surface.
Contact cement needs to be applied at a 90% rate or better.
I apply 3 sprayed coats to each surface for a permanent bond.
Make 2 prop boxes to hold the sheet in place and use 3/8" dowels every 6" on the plywood surface, the contract will hold them in place.
Clean strips of 3/8 x 3/8" wood will work too.
I place the glued aluminum sheet on the prop boxes then tack the sheet to the center of the plywood slowly hand smoothing one direction as you remove the dowels/wood strips.
When you're satisfied with the results take a "J" Roller to smooth it out permanently.
If part of the sheet sticks in the wrong spot then use a squirt bottle of lacquer thinner to release it then apply more contact to that spot.
If you're careful this can be a one person task but having an extra pair of hands comes in handy.
Danny
Re: Recommended Expoxy Thinner
Posted:
Wed Sep 14, 2022 7:28 amby Pmullen503
Whether you seal everything or not, I really like the idea of sealing the edges of plywood with either the "mix" or epoxy.
I won't thin for adhesive or laminating purposes but you can thin epoxy with methanol. Thinning only 5 or 10% makes a big difference as does just warming. (Think hair dryer temps rather than heat gun.)
Re: Recommended Expoxy Thinner
Posted:
Wed Sep 14, 2022 9:01 amby Onajourney
I got some of Raka' thinnest epoxy. I am going to epoxy all edges and corners then Paint the whole thing with Henry sealant. And on Capebuilds and other suggestions, float the aluminum.
Re: Recommended Expoxy Thinner
Posted:
Wed Sep 14, 2022 10:09 amby Pmullen503
I use Raka too. It responds well to warmth. As you paint it on, use a hair dryer (or heat gun at appropriate distance) to warm the wood ahead of the epoxy and warm the epoxy after it's down. It will get very thin and soak into the wood.
I suspect that air in the wood itself expands (as evidenced by bubbles in the epoxy) and helps draw the epoxy into the wood as that trapped air contracts when it cools.
Re: Recommended Expoxy Thinner
Posted:
Wed Sep 14, 2022 11:43 amby tony.latham
I am going to epoxy all edges and corners then Paint the whole thing with Henry sealant.
Why not seal the entire cabin with epoxy? That's what I have always done on cabins before floating aluminum.
Tony
Re: Recommended Expoxy Thinner
Posted:
Wed Sep 14, 2022 1:15 pmby Onajourney
tony.latham wrote:I am going to epoxy all edges and corners then Paint the whole thing with Henry sealant.
Why not seal the entire cabin with epoxy? That's what I have always done on cabins before floating aluminum.
Tony
Well Tony, I think you use BB on your boxes. I am using plytanium sheathing which is water resistant exterior grade. The BB is not. So I would agree with epoxy for all BB. The other reason is that the epoxy is expensive and I have a 3/4 of a gallon of Henry I bought for the underside. That stuff was $80 gal. I don't mean to sound like I am cutting corners to save buck but I just don't want to spend money and time if I don't need to. Am I miscalculating something?
Re: Recommended Expoxy Thinner
Posted:
Wed Sep 14, 2022 1:42 pmby tony.latham
The BB is not.
You can throw a chunk of Baltic birch in a bucket of water for a week, put it out, and after it's dry, nothing has changed.
Tony
Re: Recommended Expoxy Thinner
Posted:
Wed Sep 14, 2022 2:54 pmby halfdome, Danny
tony.latham wrote:The BB is not.
You can throw a chunk of Baltic birch in a bucket of water for a week, put it out, and after it's dry, nothing has changed.
Tony
I did a test for months in and out of a bucket of water and no delaminating at all.
Baltic Birch is great plywood.
Danny