I couldn’t find any pictures to make this easier to demonstrate so I whipped up this:
The object here is to demonstrate how a curved panel might be made without a vacuum press. A picture is supposed to be worth a 1,000 words so I’ll cut it short. The lighter-colored material in the center of the picture is supposed to be the end result. You will have to imagine that it is 2 or more layers of bender board (see #1 & 2 in the series). With this technique you will not want to use the urea formaldehyde glue and since you will most likely eventually have to veneer the curved panel, I recommend you get some of Joe Woodworkers cold press veneer glue and use that to bond your curved panel bender sheets.
The golden-colored objects in the picture represent more bender boards that bridge the ribs (labelled BENDER in the diagram below) and support the panel between the upper and lower ribs. Also, I might add that I don’t think you need to actually bond these bender sheets to the ribs. Further, I can’t prove it but it would seem that the more ribs you have, the better the form would be. I also think that may not be the case with the bender bridge sheets and I would use just one thickness of the thickest material you have. If you don’t want to buy anything thicker than 1/8 bender, then maybe you ought to use 2 plys for both top and bottom bridge sheets.
You will have to make some calculations to determine the radii in the diagram above (NOTE – it is not to scale and not intended to suggest any proportions). Start with the finished panel and work your way out until you get the radii of the upper and lower ribs. Make all your ribs from a single pattern (one for upper and one for lower) and be sure to include some way to align them all.
This may be over kill, but you could also include the thickness of your veneer in the calculation. You should then place one thickness of the venneer above and below the finished curved panel when you lay it up. When you get your curved panel made, you can re-use the press to adhere the veneer to both sides of the panel at once by squeezing the veneer sheets and curved panel in the form again. I did not go to that extent and did not have any problems with the panels or the veneer. I would NOT try to do the panel and the veneer at the same time.
Maybe I’ll come back with a little about the veneering later. It doesn’t get any easier than in this application. Also I will share how my cousin machined the curved rails that hold the top and bottom of the panels in the doors shown below.
I see I forgot to mention that this will work simply by piling some weight on top of the form. The bender does not offer much resistance. You could use clamps and you could also find 13 other ways to accomplish this. Finally, be sure that your upper and lower ribs are aligned before you apply pressure or you may end up with a wavy mess!