Official Luthiers Forum!

OK, so I am toying with the idea of trying double sides epoxied together, so some questions for you double agents.

Do you bend them together, then lay them up in the same mold with epoxy between? Vacuum-bag, or other arrangement?

Or do you try to epoxy them together and bend them before the epoxy sets?

A photo or two would be tre helpful.

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The member formerly known as erikbojerik....

I bend them separate, Tim McKnight bends them together. I suppose either will work ok.

What I do for a lay up is I have a solid form 8 pieces of MDF lam'd together that is .100" smaller than the mold. The mold has "feet" on it at each end so any extra overhang does has somewhere to go. I coat the mold in wax paper.

I place a thin coat of slow cure epoxy (West 105/206) on each side, with a fill center coat of silica thickened epoxy. I tape the sides together using 3M tape that is resistant to epoxy and superglue (keeps the pieces from sliding around). Put a sheet of wax paper on top

then I place a caul over the 2 sides and use heavy duty spring clamps to clamp it to the mold (I drilled holes in the solid mold). I generally use a piece of PVC at the waist and in the cutaway for a caul.

It works like a champ. You would think it woudl not be enough clamping pressure, but it is. I have never had any significant gaps.

... Also, the silica fill layer has been a marked improvement to reducing the amount of epoxy that sqeezes thorugh the pores. It is a bit of a pain to clean these sides up.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I bend mine together in a fox style bender, then glue up on a mold in a vacuum bag:



This setup works for me. I have used epoxy and titebond with no problems. Note the cam clamps to get everything into relative position. I get these pretty well set before I turn on the vacuum, and I still find myself jiggling things around as the bag gets smaller to make sure everything lines up well. .

How thick is each lamination, and how thick is the overall finished side?

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Mitch

Mine up to this point have started out at .045" each and finish out at about .08" after sanding and clean up.

I am thinking though that I might make the outside a shade thicker and the inside a shade thinner... just in case...

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I've never dived into the few threads I've seen on double-anything, but my curiosity has finally gotten the better of me. It sounds like with double-sides you're talking about two-ply laminated sides. Is that right?

yes. It makes the sides VERY stiff.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Don't use Wenge.

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tim...
http://www.mcknightguitars.com

Why not...poxy seeping through the pores?

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The member formerly known as erikbojerik....

that would be my guess...

The epoxy seepage is a real pain with this method, but lately (based on another discussion thread) I have switched my glue up procedure to.

A very light coat (just enough to wet the sides) on both mating surfaces and then mix the thickener and apply that between the layers (then clamp up as normal). This has stopped about 50% - 60% of the seepage.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I use fish glue instead of epoxy.
On my last one, I used veneer. I make the sides .080.
I didn't bother bending the veneer. It worked well and the sides were very stiff.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

I use a couple layers of standard thickness veneer for the inside and middle layers of my three ply sides, and a .050" thick piece for the outside lamination. This gives me a little more wood for sanding to make sure I don't sand through it.

Lex, do you have any problem with epoxy sticking to your vacuum bag?

No, I was worried about that so I covered the whole setup with parchment paper. It made it a real pain to line everything up.

Now I'm using titebond for my sides which just flakes right off the bag. It's so much easier to work with.

3M makes a style of tape (sorry the product number escapes me at the moment, but I could find it) that looks like heavy duty scotch tape but it is virtually impervious to glue and solvents. I tape the sides together before I put it on the press and it keeps it from sliding around when you clamp it up.

and it just pulls right off when it is dry.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I would like to know what the number of that tape is Brock, and a supplier too. Sounds like a good solution to the alignment problem I've been struggling with.

Packing tape does it. Pretty much any brand. Use it as a mould release, or bonding, anything to do with epoxy. The epoxy does not stick to it, either the adhesive side or the smooth side.

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Expectation is the source of all misery; comparison the thief of joy.
http://redrivercanoe.ca/

No, I did not have any issues with adhesive seep through, which is counter intuitive considering the caveronous sized pores. I tried three different sets of Wenge and all three were cupped after they came out of the mold so I just gave up on Wenge DS's. My guess is the pores are so large and take on an abnormal amount of adhesive that it overpowers or pulls the inner wood when the adhesive dries. I have no proof on that but that is my thought.

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tim...
http://www.mcknightguitars.com

Tim, what did you use for your adhesive on the wenge?

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The member formerly known as erikbojerik....

TAP 4:1 adhesive and West Systems. Both had the same results.

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tim...
http://www.mcknightguitars.com