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I hope all is well here on the OLF.. I am in the process of using arched braceless backs (similar to a violin or cello) on my instruments and need some help. I have made a form out of MDF board and will be using a 2.5 CFM vacuum pump with vacuum bag and netting. My first question is what is the best adhesive to use?? I have heard several different replies to this question including Better Bond cold press veneer glue, Nelson's urea-formaldehyde veneer glue, and epoxy. I am wondering which will have the best tonal characteristics while having no creep or delamination issues. My second question is whether my current vacuum pump is sufficient for this process? It is a pump generally used in HVAC applications. I tried contacting the manufacturer but they have not returned my calls and nobody else has been able to help me with this. The last question is how to get a near invisible joint and proper alignment with the bookmatched veneers on the outside (the visible ones). Thanks in advance.

Hiya

Try Unibond 800 - hard and strong.

Put a vacuum guage on your pump and verify that it will pull twenty or twenty-five inches of vacuum.

A tight joint in the centerline? Now you're talkin' fun. Invest in some perforated veneer tape, and check your (flat) veneer joint on a light table. Tape the outside face of the veneer with delicate surface masking tape, and glue the gummed perf down to the inside face.

Suck it down, see what happens. Experiment.

Dan

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Dan
http://www.acme-archtops.com

Oh, and feel free to phone; I'm a slow go on the keyboard.

Dan 410 523 5419

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Dan
http://www.acme-archtops.com

Agree 100% with Dan. Uni-bond !!!
Link

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Cut to size.....Beat to fit.....Paint to match.

Thanks a lot guys... very helpful. I actually went and bought the Nelson urea-formaldehyde formula (I thinks it's very similar to the unibond) and it works very well. My only reservation is that the pump gets pretty hot. Is there supposed to be an automatic shut-off when the correct vacuum is reached or does it run continuously?? Thanks again.

Sorry, forgot to log in

I have no idea about whether or not that style of pump is designed for continued operation under pressure. If you want the pump to cycle on and off automatically, you'll need to build a system like JoeWoodworker.com's EVS Pump.

The cheapest/easiest/quickest short-term solution would be to install a vacuum gauge, turn the pump of when it's above 25hg, and then switch it back on when it gets below 20hg. A bit like watching paint dry though...

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Richard
http://www.guitarmaker.com

Yeah, the pump needs to shut off. Running it like that will burn it out.

How much arch do you have? I made some laminated plates for a thinline archtop that had about 1/2" total arch and I had to cut a thin wedge out of the book match to keep the veneers from wrinkling.

I second the recommendation on the Uni-bond 800 glue and the preforated veneer tape. Dampen and apply the tape then run over the joint with a household iron. I cut my veneer with a sharp utility knife and a straight edge. Getting a good joint is pretty easy.

I also found that I needed a two part form to prevent blisters. I made the top part of the form out of fiberglass (polyester resin and about 5 layers of glass cloth) that was cast against the bottom form in the vacuum bag. This hard shell really gave me a smooth surface on the show face of the lamination.

Woo hoo...I got it. It worked fantastic. Thanks for the tips guys. Here are a few photos.

Pretty cool, Kristopher. How many plies, and what material?

Dan

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Dan
http://www.acme-archtops.com

Thanks!! It was 5 ply. Brazilian RW, Mahogany, Bubinga, Maple, Brazilian Rosewood. I really can't believe how stiff the back is and it rings like a bell!! I am really getting anxious to get the guitar together. Thanks for the help too. Very nice to give out your number.

A new glue to me. If, like unibond, it's waterbased, then in a few days when all the moisture works it's way through five veneers and four gluelines, your plate will REALLY ring. In the meantime, prop the plate up so both sides see air circulation; if one side dries faster, potato chip city. How do I know this? I didn't read it anywhere.

Dan

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Dan
http://www.acme-archtops.com