Mike Waddell
10-04-2005, 1:09 PM
Good afternoon everyone –
Warning: VERY long post, and is the first of two posts that detail a process.
I recently posted pics of a table that I built for the LOML, and said that I would post the procedure that I followed (with mistakes!) to create the bentwood lamination sides of the table. It was a learning experience for me, as this was the first time I have tried to do this. Last year, I went to a Bentwood Laminations class by David Marks (great guy and a great class by the way!) where he instructed us on the steps in this type of procedure. Needless to say, I think you should take the class from him rather than try this first on your own. I am not a professional, and I don’t even play one on TV! This is the process that I used; it worked well for me but I highly recommend that if you haven’t done this before you take your time and perhaps learn from someone like David Marks.
That being said, please refer to the pictures below as a semi-guide:
(First Picture) The first step was to create a template for the bentwood lamination. I copied the shape for my template from LOML’s kidney shaped desk and scaled it down to create a template out of ½” MDF. I copied the shape onto the MDF, cut it out with a bandsaw, and then used rasps to shape the edges, and ended up sanding the edges with a home-made sanding tool. If you’ve ever watched Woodworks and seen David Marks create a curved shape, you’ll know the type of home-made sanding tool I am referring to.
(Second Picture) From the template, I created a form by copying the template onto ¾” MDF, and repeated the process in step one to clean up the edges. By doing this process 5 or 6 times, stacking up the ¾” pieces and gluing/screwing them together, the form was completed as in the second picture. I also taped two layers of 1/8” cork to the outside edges of the form to make the form fit to the wood more easily during glue-up. The tape prevents the glue from permanently fastening your glued-up laminations to your form! I also cut out the center of the form to make assembly and glue-up easier.
(Third Picture) Also from the template, I created cawls (sp?) that are used to bend the laminations tightly around the form. These are created in the same manner as the form, and also use taped cork. You’ll notice that I created only a front and back cawl… a mistake that I paid for in the next step.
I do not have a picture for this, but to create the laminations I first tried using thin veneers purchased from an online retailer. While this was convenient, and I could order just about any kind of wood I desired, I killed my stock of purchased veneers in the step below (ugh). For the second glue-up attempt (it still hurts to say that), I used my bandsaw to create the veneers myself, cutting veneers from a board of quilted Mahogany a hair less than 1/16” thick, about 6” wide and a little more than six feet long. I then ran the bandsawn veneers through a drum sander to ensure that they were the same thickness and fairly smooth on the sides (sanded down to about 120 grit on the drum sander).
(Fourth Picture) During the class, David recommended Urac or Unibond 800 to create bentwood laminations. I further read in a couple of places on the internet that you can use a PVA glue (Polyvinyl Acetate, or plain old white or yellow glue) to create laminations. Though it may have worked for others, the glue-up with PVA did not work for me. After two days in the form, it still came out VERY wet and the wood was deformed. This is where the “only two cawls” monster reared its ugly head.
As you can see in the picture, because I had only the front and rear cawl, the area on the sides where the cawls came together ended up pinching the laminations no matter how hard I tried. I decided to glue it up anyway and try to deal with it later. Big mistake.
So, the first glue-up was a disaster. I may have used too much PVA glue, the veneers may have been too thin to use with the PVA, I didn’t account for the gap between the cawls that would be created by the thickness of the laminations… in short, I screwed it up pretty badly and decided to try again.
(Fifth Picture) For the next glue-up attempt, I used bandsawn veneers that were a little thicker as I feel they should have been; I broke into my wallet to purchase the Unibond 800 glue that I should have used to begin with; and I created two more cawls to help in forming the sides of the laminations as I should have done the first time. (Wow, I really screwed up that first glue-up didn’t I?).
As you might be able to tell by the fifth picture, this attempt was much easier and better. To create as close to a “seamless” appearance on the laminations, I used a scarf joint on the final two layers of veneers (there are nine total layers). To begin, I glued up the first three layers in the form and let them dry, then glued up the next four layers on top of the first three in the form, and finally scarf jointed the final two laminations and glued them up carefully over the rest of the already-dry laminations in the form. I found that I had to increase the amount of cork on the first two glued-up sections to account for less thickness than I had planned for in the final piece.
Due to attachment number limitations, the remaining portions of this procedure are in the next post with the same title.
Mike
Warning: VERY long post, and is the first of two posts that detail a process.
I recently posted pics of a table that I built for the LOML, and said that I would post the procedure that I followed (with mistakes!) to create the bentwood lamination sides of the table. It was a learning experience for me, as this was the first time I have tried to do this. Last year, I went to a Bentwood Laminations class by David Marks (great guy and a great class by the way!) where he instructed us on the steps in this type of procedure. Needless to say, I think you should take the class from him rather than try this first on your own. I am not a professional, and I don’t even play one on TV! This is the process that I used; it worked well for me but I highly recommend that if you haven’t done this before you take your time and perhaps learn from someone like David Marks.
That being said, please refer to the pictures below as a semi-guide:
(First Picture) The first step was to create a template for the bentwood lamination. I copied the shape for my template from LOML’s kidney shaped desk and scaled it down to create a template out of ½” MDF. I copied the shape onto the MDF, cut it out with a bandsaw, and then used rasps to shape the edges, and ended up sanding the edges with a home-made sanding tool. If you’ve ever watched Woodworks and seen David Marks create a curved shape, you’ll know the type of home-made sanding tool I am referring to.
(Second Picture) From the template, I created a form by copying the template onto ¾” MDF, and repeated the process in step one to clean up the edges. By doing this process 5 or 6 times, stacking up the ¾” pieces and gluing/screwing them together, the form was completed as in the second picture. I also taped two layers of 1/8” cork to the outside edges of the form to make the form fit to the wood more easily during glue-up. The tape prevents the glue from permanently fastening your glued-up laminations to your form! I also cut out the center of the form to make assembly and glue-up easier.
(Third Picture) Also from the template, I created cawls (sp?) that are used to bend the laminations tightly around the form. These are created in the same manner as the form, and also use taped cork. You’ll notice that I created only a front and back cawl… a mistake that I paid for in the next step.
I do not have a picture for this, but to create the laminations I first tried using thin veneers purchased from an online retailer. While this was convenient, and I could order just about any kind of wood I desired, I killed my stock of purchased veneers in the step below (ugh). For the second glue-up attempt (it still hurts to say that), I used my bandsaw to create the veneers myself, cutting veneers from a board of quilted Mahogany a hair less than 1/16” thick, about 6” wide and a little more than six feet long. I then ran the bandsawn veneers through a drum sander to ensure that they were the same thickness and fairly smooth on the sides (sanded down to about 120 grit on the drum sander).
(Fourth Picture) During the class, David recommended Urac or Unibond 800 to create bentwood laminations. I further read in a couple of places on the internet that you can use a PVA glue (Polyvinyl Acetate, or plain old white or yellow glue) to create laminations. Though it may have worked for others, the glue-up with PVA did not work for me. After two days in the form, it still came out VERY wet and the wood was deformed. This is where the “only two cawls” monster reared its ugly head.
As you can see in the picture, because I had only the front and rear cawl, the area on the sides where the cawls came together ended up pinching the laminations no matter how hard I tried. I decided to glue it up anyway and try to deal with it later. Big mistake.
So, the first glue-up was a disaster. I may have used too much PVA glue, the veneers may have been too thin to use with the PVA, I didn’t account for the gap between the cawls that would be created by the thickness of the laminations… in short, I screwed it up pretty badly and decided to try again.
(Fifth Picture) For the next glue-up attempt, I used bandsawn veneers that were a little thicker as I feel they should have been; I broke into my wallet to purchase the Unibond 800 glue that I should have used to begin with; and I created two more cawls to help in forming the sides of the laminations as I should have done the first time. (Wow, I really screwed up that first glue-up didn’t I?).
As you might be able to tell by the fifth picture, this attempt was much easier and better. To create as close to a “seamless” appearance on the laminations, I used a scarf joint on the final two layers of veneers (there are nine total layers). To begin, I glued up the first three layers in the form and let them dry, then glued up the next four layers on top of the first three in the form, and finally scarf jointed the final two laminations and glued them up carefully over the rest of the already-dry laminations in the form. I found that I had to increase the amount of cork on the first two glued-up sections to account for less thickness than I had planned for in the final piece.
Due to attachment number limitations, the remaining portions of this procedure are in the next post with the same title.
Mike