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Bending double sides simultaneously?
https://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=42372		 Page 1 of 1
Author:  Blair Russell [ Fri Jan 03, 2014 7:13 am ]
Post subject:  Bending double sides simultaneously?
I've been bending with a bending iron for a few years and finally want to switch over to using side bendng machine. I've been reading about laminating sides and would like to try it out after I've built my side bender, but I'm not sure of the process of bending laminate sides (although I've seen lots of stuff on how to glue them).

Do I need to make a form for each of the side laminations, since one side would be 0.055" thinner than the other, or is it possible to bend both sides simultaneously in the side bender? If I do bend with this method, would I need to use two heating blankets?

It seems like every builder has a preference on lamination thickness, number of laminations, and some even laminate without bending, so I'm a bit lost as to where to start. I was thinking of using two sides each 0.055 thick.

Cheers
Author:  Jim Kirby [ Fri Jan 03, 2014 8:13 am ]
Post subject:  Re: Bending double sides simultaneously?
I'd be worried if I tried to bend both pieces together that the piece further from the blanket may not have gotten heated as well as if it were a single piece of wood. Using blankets on both sides would certainly help. I'd probably bend the pieces individually with my single blanket setup, and not worry about the inside/outside difference in shape.

I have to give this a try at some point. I haven't been laminating sides, but I have a cocobola set with sides that are way too thin at one end, and which can't possibly be passed up.
Author:  Ken McKay [ Fri Jan 03, 2014 8:54 am ]
Post subject:  Re: Bending double sides simultaneously?
A relatively simple two part form works best for me. I can laminate one after the other in my rig and get 4 or 5 sets done and then put away the jig. The two part mold is a negative which is the exact size of the perimeter of my guitar body and then the gap consists of aluminum flashing, the blanket, one more aluminum, the side layup (0.09 three ply) and another aluminum slat. I press the sides to shape without heat but with glue (UF) then press the cutaway in and turn on the blanket. The heat cures the glue hard in 4 minutes. Remove the side and do another.
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Author:  Jim Kirby [ Fri Jan 03, 2014 11:11 am ]
Post subject:  Re: Bending double sides simultaneously?
Well that's pretty cool, Ken. How much heat do you use to set the UF glue? I guess 3 plies at a total of 0.09" are pretty bendy individually.
Author:  mkellyvrod [ Fri Jan 03, 2014 1:23 pm ]
Post subject:  Re: Bending double sides simultaneously?
Ken, your method really is impressive! No pun intended.
Author:  ernie [ Fri Jan 03, 2014 1:51 pm ]
Post subject:  Re: Bending double sides simultaneously?
I use an aluminum overholtzer mold to bend 1 thick piece .070 and I add 2 veneers .022 with u f veneer brwn glue It/s all done on the alum jig, that can only bend 1 side at a time for CL gtr. Sorry no pics. I get the veneers either locally or from certainly veneer in buffalo
Author:  Burton LeGeyt [ Fri Jan 03, 2014 2:10 pm ]
Post subject:  Re: Bending double sides simultaneously?
Each of my sides are in the .035 +/- range, so the time it takes to pre bend them on the pipe is about equal to the time it would take to get out and setup the bender (I imagine, I don't have a bending form).

I'm curious why people use such thick veneers for their double sided guitars? A doubled side finished at .065 or so seems absolutely thick/stiff enough to me.

The final side shape is set in the glue up jig so getting it only close beforehand seems more than enough. I use an outside form so the guitar shape never varies (in case the side thickness does). That makes it a bit harder to clamp when laminating but not so bad.
Author:  Ken McKay [ Fri Jan 03, 2014 4:35 pm ]
Post subject:  Bending double sides simultaneously?
I am a seat of the pants kind of luthier and just plug the blanket straight in and observe for signs of the glue setting. I got it down now and four min does it. The plys are not too bendy. The waist and bouts are pretty mild radius but the cutaway will crack if I don't use the special sauce aka veneer softener.
The reason I make my sides 0.09 inches thick is because that's the way it was done in 1958. I in my case it's essential to have a layer in the center with crosswise grain.


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Ken
Author:  Terence Kennedy [ Fri Jan 03, 2014 5:08 pm ]
Post subject:  Re: Bending double sides simultaneously?
I bend double sides together in a Fox bender all the time, it works well. I laminate them on a separate form.

Cool rig Ken.
Author:  James Ringelspaugh [ Fri Jan 03, 2014 5:25 pm ]
Post subject:  Re: Bending double sides simultaneously?
When I've done laminated sides, I bent two .05" pieces together in a fox bender with no problems. Glue up is in a vacuum bag over a mold. Because they were bent together the sides always fit together perfectly.

Burton LeGeyt wrote:
I'm curious why people use such thick veneers for their double sided guitars? A doubled side finished at .065 or so seems absolutely thick/stiff enough to me.


I can't speak for everybody, but I did it for the extra stiffness. With solid linings it made the rim just unbelievably stiff and stable. I build on a solera with no outside molds and it made putting the box together much easier for me. That said I haven't made a guitar with double sides for a few years...
Author:  Blair Russell [ Sat Jan 04, 2014 7:11 am ]
Post subject:  Re: Bending double sides simultaneously?
Burton LeGeyt wrote:
Each of my sides are in the .035 +/- range, so the time it takes to pre bend them on the pipe is about equal to the time it would take to get out and setup the bender (I imagine, I don't have a bending form).

I'm curious why people use such thick veneers for their double sided guitars? A doubled side finished at .065 or so seems absolutely thick/stiff enough to me.

The final side shape is set in the glue up jig so getting it only close beforehand seems more than enough. I use an outside form so the guitar shape never varies (in case the side thickness does). That makes it a bit harder to clamp when laminating but not so bad.


How exact do you have to bend them before you laminate them in the glue jig? Is a 0.065 double side considerably stronger than a single 0.08 side?
Author:  Blair Russell [ Sat Jan 04, 2014 7:13 am ]
Post subject:  Re: Bending double sides simultaneously?
Terence Kennedy wrote:
I bend double sides together in a Fox bender all the time, it works well. I laminate them on a separate form.

Cool rig Ken.


Is the process as straightforward as I'm guessing it is? Just bend like a normal side, except do both at once?
Author:  Terence Kennedy [ Sat Jan 04, 2014 10:58 am ]
Post subject:  Re: Bending double sides simultaneously?
Blair Russell wrote:
Terence Kennedy wrote:
I bend double sides together in a Fox bender all the time, it works well. I laminate them on a separate form.

Cool rig Ken.


Is the process as straightforward as I'm guessing it is? Just bend like a normal side, except do both at once?


When I got into double sides I e-mailed Tim McKnight and he bent them together so that's what I did. I profile, thickness, and then moisten and stick them together. The water causes them to adhere to each other.
Moist brown paper on either side, slats, and two blankets. As mentioned, they are perfectly matched coming off the bender which makes laminating easier.

I have also bent double Maple archtop sides together with a tight cutaway and to my huge relief it worked great. I think using two blankets may give an added measure of security with a more even heat.

I have gone around .050 for the inner side and .060 for the outer. So far the same wood type, just a lower grade for the inner side.

As mentioned, they are very stiff and the sound has been very well received by players with a much better ear than mine. After reading Trevor's books and the effect of adding mass to sides, the changes he describes seem similar to what I have experienced.
Author:  Toonces [ Sat Jan 04, 2014 12:35 pm ]
Post subject:  Re: Bending double sides simultaneously?
My goal for the sides is to have them as stiff as they can possibly be. I aim for 0.125" because that is the limit for me of having two extremely easy laminates to bend. If you start going thicker than 0.060", you start to have the same problems of bending one-piece sides (cupping, etc.). These problems are especially pronounced with certain woods like Ebonies and some of the other exotics that I use on a regular basis. And so, if I wanted to go thicker than 0.125" for the laminates, I would probably just add an additional laminate; but I think that is overkill.

Bear in mind, there isn't just one right approach to building. Burton uses laminates because they allow him to go thinner and lighter but still maintain a strong structure. I use laminates because they allow me to achieve a stronger and more stable/massive structure without worrying about bending problems when using exotic tonewoods (if you bend woods at 0.060", it is almost impossible to break them).
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