Flatsawn sides prone to cupping...

[Brian Evans]

I have a nice set of quilted maple sides that I bought for an archtop, and being quilted they are necessarily flatsawn. The last set of flatsawn maple sides I used cupped along the lower bout, enough for me to notice, but probably not a casual glance. Maybe 1/32" after sanding. Is there a technique that I can use to minimize cupping? I do favor stiff and "dense" sides, so I was contemplating using more side braces than normal, quarter sawn for maximum stiffness, and thicker than normal, like 1/4 to 3/16". My sides are 2 5/8" tall, for 3" overall side depth.

Thanks, Brian

[Barry Daniels]

What kind of a bender are you using? Also, how well supported is the side when it is in your form? In other words how much of the side extends above the form, and what type of spreader clamps do you use? See where I am going with this?

One thing I am doing now which makes for much more stable sides is I thin down the good stuff to about .050" and then laminate a regular thickness veneer (.023") on the inside.

[Brian Evans]

I am using a 3" tube bender. The sides were flat when they came off the bender, and sat around in the form for several months before I started to process them past gluing in head and tail blocks. I use spreaders at the waist, and a couple of other points, but not around the full circumference of the lower bout. As I write this, I think the cupping started when I was gluing the linings. My form is three thicknesses of .75" plywood. so 2.25" deep and my sides are 2 5/8" deep. I was experimenting with one piece un-kerfed linings and my side braces were installed quite late in the game, and only between the linings. I think next time I will try full height side braces installed quickly after I bend the sides, and put the linings between the braces. Barry, what technique and glue do you use for your lamination?

[Barry Daniels]

I use West Systems epoxy and a gigantic form with bolts and steel bars to clamp the thing up. It makes an incredibly stiff and stable rim. By the way, my memory is getting bad, I actually use two layers of veneer to back up the show layer. If you want to read more, there are several big threads on side lamination in the library.