Official Luthiers Forum!

Hi guys, long time no speak! I've been lurking around, but stupidly busy working on my PhD thesis, so almost no time at all for building. Finally coming up for a little air and getting some work done on a few projects, but I've got a question for those of you with a little vacuum bagging experience.

I'm currently trying to figure out what kind of sandwich is ideal/practical for the type of laminations I want to do. Right now it's a non-guitar project (wood on wood, for a table), soon it will be some guitar sides. I'm guessing the molds should be waxed with release wax and covered with a release film/foil (to prevent wax getting on the glue), but I'm unclear on the usefulness or even necessity of peel ply for wood layups.

Right now, I'm planning on laminating indian rosewood to WRC using West Systems epoxy (105/206). I have some peel ply tape for the edges, which worked OK, but I didn't use any release film/perforated foil between that and the bleeder cloth. My first panel had too much bleed through past the (narrom) peel ply tape edges, so I have chunks of wonderfully laminated breather stuck to the workpiece, which I'll have to send through the thickness sander to get off (yay.). I want to avoid this on subsequent laminates, and DEFINITELY want to avoid this when laminating sides (plan is a 2 or 3-ply layup with cocobolo outer, EIR inner for my Trevor Gore-inspired new build..). So, lamination/epoxy mavens, any tips?

Can't help you with the table but for the sides you can use wax or wax paper between it and the mold. If you like epoxy you can use it but there's really no need for the fumes and the PITA factor. I prefer titebond or fish glue with a mold and a truck tire tube. It's quick, easy and very effective- three things I am very find of.

Hmm...not saying it doesn't work-I haven't tried it-but I'd be concerned about not getting even clamping pressure across the width of the side with that setup, esp with fish glue.
Some cauls between the tube and the side might be good insurance.

Not a bad idea at all but I don't see the need at the moment. I now use the same method for binding and only trouble spots with trouble wood (the waist with ebony binding) require cauls to get right. Once pulled tight I have a hard time pulling the tube away anywhere across the grain of the side be it middle or the end. It's pretty even pressure and a lot tighter than it looks. If the sides were wider than the mold I'd be concerned.

Peel ply is unnecessary when laminating wood. It's only there to provide a nice surface finish for composites and to protect the surface from contamination until you want to laminate something else onto it. With wood, you just need the release film and breather. If you don't want the breather sticking itself to it, you just have to leave a gap around the edge of the release film, and get the right quantity of resin in there, which can be tricky...

_________________
"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

I've done a bunch of two ply laminations using similar woods with IRW and Mahogany. Unibond 800 for glue. Bleed through has not been a problem although Unibond does make a blocker if it is a problem. I've tried the outside and inside mold and have found the inside a little easier for me. I put a thin layer of cork on the inside mold and covered it with clear packing tape. Same for the cauls.

I've become a huge fan of double sides. The rubber band clamping system looks cool, I would also worry about loss of flatness and uneven pressure but hey if it works it's pretty darn slick. I'll experiment with it.

Here's a picture of the clamping setup I most commonly use.





Here's an outside clamping mold, it works too, lots of clamps. The inside caul is kerfed plywood that conforms to the curves. You can make it easily on the table saw with a sled and indexing pins.



Profiling and bending the sides together makes for a great fit when laminating.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Mattia, I don't have anything to add to the thread, but I'd love to know what your dissertation is on

I use epoxy as the release surface - the platen I laminate flat work on, and the shaped side molds and plaster archtop plate molds in my shop are all sealed with multiple coats of epoxy sanded to fair and smooth. I coat these with Butcher's, and buff off the excess with clean rags, and have never had a sign of wax transfer to the veneer. In fact, this is a treatment I do ONCE, with a new form, and haven't ever repeated.

That said, I use Unibond, and any glue squeeze pops right off, even after 18 hours under vacuum. I don't know if this would work with an epoxy glue-up, given epoxy's aggressiveness. I would only bother with the mess and expense of epoxy if I went back to yacht repair - I probably applied 200 gallons of West and Sys 3 in an earlier career.

Consider Unibond.

Dan

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

Good to see you here Dan. The back I got from you a couple of years ago worked out great.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Thanks for the tips, I've ordered some uni bond type urea resin glue to experiment with as well, and some release film.

James: my dissertation is on cardiorenal interaction and diuretic therapy in heart failure - sort of an intersect between heart and kidney disease form a cardiological perspective. Mostly involves a bunch of statistical analysis. Which I actually really enjoy. Who knew?

Uni-bond. No need for release stuff. None at all. Use a thin cardboard called news board. Works as a caul pad and helps to even out pressure and absorbs excess glue. Just pull off the cardboard and sand or scrap any that sticks to the wood. Many years experience bagging and form clamping wood.
L

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

You can use a varity of plastics for the release layer. In building composite airplanes, Mylar sheets are frequently used both to provide the release layer and to give a smooth surface finish. Mylar is available in a wide range of thicknesses, use thicker to get smooth surfaces on simple curves and thinner as the shapes become more complex. In a pinch, polycarbonate packing tape can also be used as the release layer with amine cure epoxies such as the 105/206 you mentioned. 105/205 is the normal combo for vacuum bagging.

Peel ply isn't really necessary with most woods, but can be helpful as a breather on non-porous woods like maple.

When working with epoxy be sure to have good ventilation and wear gloves, the long-term health effects can be quite severe.

If any of the epoxy reaches an outside surface, Wash with a scotch brite and warm water before sanding to remove the amine blush and prevent later finish problems.

-jd