Forming the curved panels, step 1

When forming curved panel spring back is something which must be taken into account. Spring back is the tendency of the panel to change its shape from that of the form once pressure is removed.

Some builders try to predict the amount of spring back and allow for it in the form design. But since I need 3 panel with identical curves, that's not a good plan. Instead I use a multi step process to eliminate spring back. The more layers used, and the thinner the layers, the less spring back you'll have. Also the more rigid the glue used, the less spring back. I'll take advantage of both these facts to achieve the results I desire.

First step is to sandwich a layer of backer veneer between 2 pieces of 3/8" bending plywood. The grain of the veneer must run perpendicular to the grain of the plywood. Backer veneer is any inexpensive veneer. In this case I'm using beech wood veneer flats. This veneer comes in pieces 8' long by 7" wide, so I use 3-hole veneer tape to piece together a sheet large enough for my purposes. The tape will be left in place inside the panel, it won't effect anything.



Next I glue the panels together. I'm using a catalyzed glue due to its rigidity, which will further stiffen the panel. Using a disposable roller, I apply the glue liberally to the bending plywood. The plywood is very rough and soaks up a lot of glue.



After gluing, the sandwich is assembled and placed on the form. A couple pieces of tape hold everything in place...



... and the assembly is placed in the bag.



The bag is sealed and the vacuum is applied.



The panel has to sit under pressure for 4 hours. When it comes out, I have a panel which springs-back from the form, but that's ok, I'm not done. Here you can see the spring back by looking for the shadow line where the panel separates from the form.



Here's the panel from the side. This one gets to site while a second one is pressed in the bag. I'll need to cut one panel in half to make the two sides of the vent chase.