Bending laminated sides

[markishandsome]

After failing miserably to get decent sides cut out of solid stock, I made a set of laminated sides out of two strips of veneer. They came out a little stiffer than I expected and am now unsure if I'll be able to bend them. I normally soak sides in water and bend around a hot pipe, but the veneers are glued together with titebond and this sounds like a recipe for delamination. Am I hosed? Should I try bending them cold/dry/normal? Grrr

Thanks
Mark

[Paul Hostetter]

Several historical notes:

Selmer laminated sides in a shaped mold - no bending afterwards required.

Gibson made zillions of guitars in Kalamazoo that had laminated backs but solid sides - they were easier to bend.

Laminated sides can be bent, you just hope you don't trash the glue in the process.

Eventually one can get the temperature and timing right so that almost any wood can be bent safely and reliably, whether it's over an iron or in a Fox thing. Practice makes perfect. If I were you, I'd go back and try solid sides again. Get several sets and keep at it until you succeed.

[Dale Ludewig]

I believe also that laminating the pieces together and then trying to bend them will present many challenges- as you mentioned: delamination. If you want to take that route, then you probably should prebend the real thin things and then put them in a mold. And the mold has to be virtually perfect. Otherwise you'll have gaps between the laminations and that's just no good.

I would think, and Paul could probably verify this, that the laminated tops and backs were done in presses with lots! of heat and pressure. If you're only doing this on a small scale, the amount of effort involved in making the molds to bend your laminated sides (pre-lamination) and then glue them together just isn't going to be time well spent.

Perhaps your side thickness could be taken down a bit? How thick are your sides. I think a lot of builders are hovering in the .080 thickness. In some areas, they may even thin in a bit more.

Also, from my experience, don't soak your wood if you're going to use a bending iron. Highly figured wood that's been soaked is just going to want to come apart on you. Spritz the wood with water and hit the iron. Gently. Just my $.02.

[Rick Turner]

I've bent sides from three ply mahogany (probably sapele) and rosewood...stuff that came via Gidwani at Exotic Woods. Bent as easy as could be in Fox-style benders.
But really I think you should learn how to bend solid sides; it really is pretty easy. The real trick is to use a bending strap rather than just wood on the hot pipe. You'll need a short length of 22 or so gage stainless sheet metal with some sort of handles on each end and you hold that on top of the wood as you rock the wood back and forth on the hot pipe. There are some top of the line small shop guitar makers like Linda Manzer and Bill Cumpiano who still do most of their building in the very free, no molds Spanish style free bending the sides over a hot pipe.

[markishandsome]

I guess my wording was ambiguous. I have no problem bending solid sides (well, no more than anyone else), my problem was actually cutting the strips off of solid stock. They kept coming out warped or burnt or otherwise irregular. I wanted to go down to .05 in thickness, like a fiddle.

I made the laminates by slicing up a scrap of veneer I found in the trash at the art school, so it's no big loss if they don't work out. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif

My plan was to try to keep the temperature of the pipe below the melting point of titebond, not that I know what that is, and take my time. The other angle would be to get it real hot and try to bend it real fast before the strips could delaminate. I guess I'll just try both with what i've got and see what happens. Any thoughts?

[tree]

So this is more of a stock thicknessing question, then?

I recently thicknessed my own band stock for Shaker-style oval boxes, and it is roughly the thickness you are shooting for. #I simply cut them slightly oversize and then thicknessed them using a plane. #You have to clamp the strips at one end (I clamped them onto a flat board and then onto my workbench) and use the plane so that you're pulling against the clamp. #This requires that you check your stock thickness frequently and switch ends several time under the clamp. #But it works surprisingly well.

It helped considerably that I own a very well-designed low-angle Jack plane and utilized a replacement iron that gave me a 50 degree cutting angle (higher than normal for hard wood with difficult grain). #It functioned almost as a scraper plane. With light cuts, that thing handles reversing grain without a hiccup. #It probably helped that I skewed the angle for the entire length of the thin stock.

If you don't have a plane like mine I suspect you could accomplish the same goal with a scraper plane, cabinet scraper or thickness sander.

[Rick Turner]

For narrow mando sides, you can thickness sand them with a drum sander mounted on a drill press. There's a jig called the "Luthier's Friend" that will handle this task admirably.

http://www.luthiersfriend.com/

[markishandsome]

Experiment 1

I'f I'm careful I can bend the laminates to the mold cold, but of course when I let go they pop back out straight. If i just clamped them up in the mold, how long would I have to wait for them to stay that way? If a added bent solid violin-style linings while still clamped up? Could I stick it in the oven?

[Antlurz]

ON your expirement 1, spritz them with water, just enough to moisten the entire surface, then bend them cold and let them dry out well. Might be all you need to do. I've had good luck bending freaky quilted maple that way.

Of course, on the maple, I did it in several stages, part way at a time. If you've bent it all the way cold, there shouldn't be any problem, I'd think...

Ron

[kww]

If you can cold bend the laminate temporarily, why not use an exterior form to hold the sides in place and then install the back and blocks? Are you afraid the mighty force of .05 thickness laminate trying to straighten is going to warp and distort the instrument? Or am I missing something?

Again, not a luthier, just an interested kibitzer.

[markishandsome]

Well, for one thing I'm using an inside form. It would also be tricky to put on spool clamps to attatch the back if there were an outside form in the way.

[Rick Turner]

I guess my big question is why reinvent the wheel? Hot bending mando sides and outside molds have worked just great for tens of thousands if not hundreds of thousands of instruments. Why do it some other way? This isn't brain surgery nor rocket science. What's worked for a hundred or more years still works quite well, and with some advances like electric heating blankets, it's easier than ever. This isn't a money issue...

[markishandsome]

I'm not sure who you think is reinventing anything. I thought inside forms were just as common as outside forms and always had been. Am I mistaken?

[Rick Turner]

Inside forms are common for violin building and for bowl back instruments, but outside forms are standard for fretted instruments. For one thing, you can glue on the back and top while the instrument is in the mold with an outside form.

The other thing, though, is bending hot. Yes, it's possible to bend cold if the wood is very thin, but the heat is what really makes bending work. You are actually changing the cellular structure permanently when you head bend wood. The bonds between the fibers weaken with the heat and allow the fibers to shift and then rebond in the new bent position.

The real point of using water when bending is that the water conducts the heat all the way into and through the wood while protecting the wood from burning.

[markishandsome]

Hmm. I guess all the books I've been looking at have been violin-oriented (easier to come by at the public library). Live and learn. Thanks for your help
Mark