Comments

• Bones Moderator

  April 2017 Posts: 3,319

  Hey Craig, did you join the top first and then bend it or bend each half and then join? thanks!
• Craig Bumgarner Drayden, MarylandVirtuoso Bumgarner S/N 001

  April 2017 Posts: 795

  Bones wrote: »

  Hey Craig, did you join the top first and then bend it or bend each half and then join? thanks!

  
  I bent each half and then joined. I've bent a jointed top with the heat and clamp method, but there can be some shrinkage around the joint at the bend point and the joint can open up a little, so I have not done that for quite a while.
  
  The shrinkage happens when bending just the halves too, so even if the edge is planed straight before bending, it has to be touched up. I use a long aluminum sanding beam for this, perfect joint every time.
  
  

  Bumgarner Guitar Blog
• Bones Moderator

  April 2017 edited April 2017 Posts: 3,319

  Ok yeah that makes sense. Since the boards are not flat anymore how do you keep them lined up to glue... in a fixture?
  
  You've got me inspired to get back out in the shop after many years. I've only made one Selmac copy (all the others are carved archtops) and that has a domed top but I've always wanted to try a pliage. Your success is getting me motivated (that plus since my left hand is permanently messed up so I can't play a lot anymore).
  
  thanks
  
  PS- for hand bending sides I use a section of a small, aluminum sailboat mast and an electrical heating element inside. I use a common rheostat to adjust the temp and at full tilt it gets really hot. I should check the temp but it will scorch wood if you want to.
• Craig Bumgarner Drayden, MarylandVirtuoso Bumgarner S/N 001

  April 2017 Posts: 795

  My jig for gluing bent tops is very simple, just a long block of wood about 75mm wide and the angle (7 degrees I think) cut in the top of the block in the right place. At the thickest, it is about 40-50mm and little longer than the top itself. I can post a picture if you like. I use this in lieu of a flat table. I set the block up on two other block set cross wise so I can get clamps in where I need them. I set the top on the block gluing with the outside surface up. Other that that, it is pretty much the same as a flat top.
  
  To clamp, i run a bead of glue and tape the halves together. Set the top on the jig and set some weights on the seam to get the edges aligned up and down. I clamped down lightly on the center line where I can for the same reason. Then I set up three light bar clamps across the top and lightly squeeze the halves together. I clamp the top to the bar clamps at the outboard edges to keep the top from folding up under compression, then tighten some more. If the top is well jointed, it does not take much clamping pressure to get a nice bead of glue squeezing out. Tighten up all the clamps, done, easy.

  Bumgarner Guitar Blog
• AndrewUlle Cleveland, OH✭✭✭ Cigano GJ-15

  April 2017 Posts: 541

  These videos from Mateos are great. Here's one about joining the top halves:
  https://www.facebook.com/geronimo.mateos/posts/10208949320875574
• Bones Moderator

  April 2017 Posts: 3,319

  Yeah Craig, a picture would be awesome if it's not a big deal.
  
  Thanks for the info guys!
• Craig Bumgarner Drayden, MarylandVirtuoso Bumgarner S/N 001

  April 2017 Posts: 795

  Sorry to be slow coming back, busy with family and little kids over Easter.
  
  The block I was talking about looks like this:
  
  
  
  I set it up on two other blocks so I can get clamps under the pliage block.
  
  
  
  Here's a picture of an already glued up top sitting on the block
  
  
  
  Here is a picture of a rough top with no bend, just for illustration of clamping method. The actual bent top is aligned with the "bend" in the block and clamped on the ends. I use long bar clamps (3) to clamp the joint side ways. Note the spring clamps holding the bar to the top on the ends, this is very helpful top prevent the thin top from bending under clamp pressure. I also use weights and deep throat clamps to keep the joint aligned top to bottom.
  
  
  
  Finally, a pic of the bent top.
  
  
  
  
  

  

  Bumgarner Guitar Blog
• Bones Moderator

  April 2017 edited April 2017 Posts: 3,319

  Very cool, thanks! NP on the delayed response it's going to be a while before I can get back out in the shop anyway. How did you accurately cut the very shallow 7 degree angle in the block? What happens to the bend at the edges when you clamp to the sides, just pull it flat with the clamps?
• Craig Bumgarner Drayden, MarylandVirtuoso Bumgarner S/N 001

  April 2017 Posts: 795

  The accuracy of the 7 degree angle is not critical. The top halves will not be perfect, but it is helpful if they are about the same. I just drew the angle with a bevel gauge, sawed it out on the bandsaw and planed it true.
  
  If the top joint is dead straight, it does not take much pressure to clamp the joint. the bar clamps are almost an after thought. More important is getting as many clamps and weights down on the joint so the two halves align. Because you can't run the top through the thickness sander after joining like you do with a flat top, the top halves are thicknessed close to the target thickness and care is taken in gluing to be sure one side is not higher than the other. If that happen, you have to sand more off and that might take you below target.
  
  Clamping the bar to the top at the edge is a recent discovery and in the past, I just clamped them and was careful not to distort the top too much. If you over do it, you can break the top though I've not done that. Clamping the bar to the top is a big improvement and easy.
  
  BTW, the Mateos top joining video Andrew provided the link to illustrates the traditional method of clamping the top join. In the video, he is joining flat halves, not bent. The method could be adapted to joining bent top easily enough, but my method is essentially the same in concept, just substituting clamps for the rope and wedges.

  Bumgarner Guitar Blog
• Bones Moderator

  April 2017 Posts: 3,319

  Ok thanks. Yeah that makes sense since you can't really do much about the overall thickness once it's bent with a thickness sander.
  
  Do you just pull the bend down flat at the edge when you clamp the top to the sides?