Double sides

[Barry Daniels]

I have reported here before that I gave that technique a valiant effort once when constructing a large headboard for a bed frame that was to be veneered with various species. I could not get it to work well. I got places that blistered and the heat caused the veneer to shrink and crack. I upgraded to a vacuum bag which worked perfectly. But vacuum bags don't work as well for curved surfaces as they do for flat.

[Mark Swanson]

Ken McKay was a participant here at one time, he is a friend too. Interestingly, I see Ken at Bryan Galloup's place once or twice a year when we go there to talk or have the Northwoods Seminars.
Barry, I will ask Bryan for more details the next time I see him. He uses a sheet of adhesive that he places between the two layers and it melts when heated.

[Barry Daniels]

Thanks Mark.

[David King]

"Prepreg" glass or CF would be another way of conveying glue into the joint. It comes pre-catalyzed and needs to be refrigerated for a shelf life of about 6 months. Some of them cure at about 180º for an hour or so but some others will need a higher temp and are rated to endure higher temps as well.

[Chuck Morrison]

I'm going back to a previous discussion rather than starting a new one, not sure which is proper protocol. I've done double sides in the past layering up veneers, but I never felt like that was doing what it was supposed to, which is giving a more solid foundation for holding the soundboard and reducing energy loss. Envisioning a piano frame and case. So I decided to go a bit further using a full width reverse kerfing.

extended kerfed sides

I re-sawed a clear pine board in half I and kerfed it on the table saw. I thinned the solid side with the drum sander to get it flexible enough, layered up some plywood and cut out the cauls. Finally I glued the kerfing to some sides in sections as it was too ungainly to try to do it as full lengths. I used a lot of titebond and the result is as shown. Last night I epoxied in some rosewood veneer and will finish that up today. The final thickness of the sides is 10mm or a bit over 3/8". These sides hold shape like nothing I've seen before. It sounds like lumber when tapped on.

Rosewood veneer as inner surface

I like not having an end block and I'm thinking of ways to smooth out a heel block.

Cheers !

[Bob Ionta]

I've vacuum veneered 1 set of laminated sides. Cherry, .045", maple .045", cherry .045". The layers were stacked and pre-bent on a Fox-style bender with a blanket. Gorilla polyurethane glue. In my first attempt I spread the glue and stacked the layers in a 6" wide bag clamped at both ends, laid over the bending form. While the vacuum was being pulled I clamped down the waist and the upper and lower bouts. The side turned out great but I used too much glue which expanded like crazy filling the vacuum mesh and that, combined with the too-stiff vinyl bag, made it impossible to get the side out of the bag. I had to cut it out. At least I had 1 good side after laboriously scraping the excess glue.

In my second attempt I used a large bag and a very, very thin layer of Gorilla glue. Used the bending form, removed from the bender this time. Spread the glue, stacked the layers on the form (waxed paper above and below), laid the mesh over the top, added a custom caul in the waist so the bag wouldn't have to stretch into the depth of the curve, and slid the whole shebang into the bag. Pulled the vacuum down and added 1 clamp over the waist caul and 1 each at the upper and lower bouts. This side also turned out great and wasn't such a mess of glue and at least I didn't have to sacrifice the bag.

My laminations worked out well but the process sure wasn't pretty. I want to try some different methods for the next guitar so I'm watching this thread carefully. Thanks to all for the sharing.

[Barry Daniels]

Yep, procedure is critical to make this work properly. Working clean and minimizing glue is important. Also make sure the glue will not stick to your bag. If it does, you may need an intermediate layer of non-stick material.

[Brent Tobin]

Has anyone tried Lee Valley's 2002 GF for laminating ? I've used it for years on dark colored woods and even on light woods where the tan glue line isn't a problem. Much like HHG, it dries glass hard and cleans up easily with water. I've used System Three for pore filling and I'm not crazy about the mess, so if I do try double-sides, I think this may be an option.

Brent

[Alan Carruth]

The glue+iron technique is the old 'hammer veneering' method that was standard for centuries. Both surfaces are spread with hot hide glue, which is allowed to gel but not to dry. The veneer is put down and the glue forced out from the center using a heated copper squeegee. It's all done in a warm environment: often a brick wall was built a few feet in front of a fire place, and gluing was done between the fire and the wall. this could well work for making sides. Note that is this case the water is still in the glue, so there's probably no chance of shrinkage cracking while you work. Afterwards....?

[Darren King]

Good morning,
I have been vacuum pressing veneered and laminated components for almost 20 years and, last January, decided that I could put off making a guitar no longer. I have now built four (2 completely finished and strung) based on a Georgia Luthier plan, and I have a Maccaferri Petite Bouche part built and another two Maccaferri Concert models nearing completion. All of the backs and sides were laminated in a vacuum bag running at around 90% vacuum which equates to 9000kg per m2. I tried using West system epoxy but found that the degree of bleed through was unacceptable and I so I switched to using a liquid urea formaldehyde resin with a medium speed powdered hardener (full cure 8-10 hours) and and a filler powder which prevents bleed through. I didn't try the micro fibre option with the West System but the fact that the UF resin can be washed up with water, and so I can us my normal hopper fed glue spreader, has convinced me that this is the best glue for my needs. I would advise against the use of PU (Gorilla) adhesives for guitar making as this glue doesn't cure hard enough to ensure that it won't have a deadening effect on the final instrument. The lay up has varied but in all cases I was using standard thickness (0.55-0.6mm) commercially available veneer. I have used 4 or 5 layers but for future guitars I will be going with 5 with the grain direction alternating between layers. In one instance I used macassar ebony for all of the layers but, as one of the key benefits of using knife cut veneers over sawn solid timber is the conservation of increasingly valuable and rare species of timber, I have now settled on using poplar for the inner cores which I think is the same as the original Selmer built instruments. All of the sides were laminated over a CNC cut polystyrene mould faced with a thin layer of birch ply and PTFE impregnated glass cloth to provide a fully non-stick surface, and the backs were laminated into a CNC routed MDF dished mould. The slow cure resin meant that there was no need for any sense of panic or undue urgency in getting the parts into the bag and resulted in parts with perfect glue lines even around the tight section of the Maccaferri cut away. Velcro straps can be incorporated into this type of mould to allow for partial forming of the shape prior to placing it in the bag although adhesive tape (as seen in the photos) can perform a similar, if not quite so elegant, function. I can only post 5 photos at a time but I'll put up some additional pictures of the guitars in various stages of construction if any of you would like to see more.
Regards
Darren

[Chuck Morrison]

Hi Darren,
Thanks for the detailed description and the photos. Definitely worth more than 1000 words in this case. 5 layers of .5mm veneer is 2.5 - 3 mm + whatever glue adds. I got away with 3 layers on a guitar I built to be ultra light (1.5mm).

What did you use to glue the birch veneer onto the polystyrene ? I've had problems with some glues melting styrofoam.

[Darren King]

I have used both a spray contact adhesive specifically meant for polystyrene and a glue film (basically double sided tape without the paper carrier in the middle). I might give a very light weight guitar a go at some stage but a couple of other makers who I have had dealings with seem to be going in the other direction, in one case having sides at 5mm thick! His guitars are very highly regarded but I wouldn't want to carry one too far!
I also used the vacuum bag for laminating the rosette rings and for bonding the braces to the back and soundboard.
Here are a few more pics.

[Bob Francis]

Those ebony sides are incredible!

[Matt Atkinson]

I imagine laminated sides have very little springback?

[Chuck Morrison]

I imagine laminated sides have very little springback?

In the case of the fully kerfed sides I show above, yes. I'd say none actually since it was glued together in the form and it still fits closely into the form even with top and back attached.