veneering a compound curve

[Frank Zingale]

I have a design for a bar that has a footprint of a circle and from top to 3/4 down is concaved. My question is, has anyone ever veneered a compund curve? and if so any suggestions would be great. The circle for the footprint has a radius of about six feet and the bar height is 42 inches. I have recently posed this question to joe@veneersupplies.com, and he thought that i should pose this question on Sawmill creek, Woodworking forum. My concern with the compound curve is making sure i dont get any creases in the Veneer when laying it up, or putting it in the vaccume bag.Again any help or thoughts will be well appreciated.

Frank Zingale

[Todd Carpenter]

Hi Frank,

I have done some compound curves and the best advice I can give, is run it dry in your vacuum press to see where it's going to wrinkle. And I'm betting it's going to wrinkle - you probably won't escape it - and then you can plan your relief cuts, thin your veneer (whatever your plan is).

Good luck and let us know how it comes out...

HTH
Todd

[Jamie Buxton]

Unless the curves are very very very shallow, you can't form a flat sheet of veneer into a dome (or a bowl) shape. The edges would have to crumple or stretch, and wood doesn't like doing that. The best you can do is to cut the flat sheet into strips that are narrower at the ends and wider in the middle. When you bend them on to the domed substrate, the gaps at the ends close. It is a very tricky business. (There's also the question of how you're going to make the dome-shaped substrate. You can't just make it from plywood. It doesn't like bending into a dome either.)

I've just re-read your description of the bar, and I don't understand it completely. Perhaps it doesn't require a real compound-curved surface, but is made from two simple-curved surfaces. If so, it will be much easier to build. If you could post a drawing of the piece, maybe there's ways to tackle it.

[Bill Arnold]

As I understand, you have a horizontal radius at the top and a vertical radius as well. The way I would approach it is to cut the veneer into wedges and apply them individually. I'd create a pattern by using my laser level to illuminate a line on the bar, trace it, then move the line over a few inches and draw another line. Then I'd lay a piece of heavy paper along one line and cut it to match the other. Assuming the radii are the same at all points, all segments of veneer will be the same.

Edit: I have a vacuum bagging system but this sounds like a candidate for ironing the veneer onto the bar.

Edit2: As I thought about it more, using wedges of veneer will also give you a starburst effect, depending on the type of veneer you choose.

[Jamie Buxton]

Here's two ways I read your description of the bar. The object on the right is does not contain compound curves. It has two simple curves, and is not horribly difficult to make. The object on the left does have a compound curve: that cove at the top. It is much much more difficult to make. You have to cut the flat veneer into shapes that butt together when you glue them to the form. Me, I'd try to avoid doing this job -- at least as veneer. I'd offer to redesign the shape to something that is easier to build, and back it up with prices quotes reflecting the work necessary.

[Bill Wyko]

I've never done this but you might try a dry run with veneer softener on your veneer. Let it dry completely in the bag so it holds its shape. Then go back and glue it. I would also recomend using a foot activated vacuum in order to gradually work the veneer into shape. Any where you end up with a gather or crease inthe wood, repair it like an inlay. On the TV show How They Do It, there is an episode where they show the wood grain being done on a Bently dash. Try DIY and see if you can find the episode. It had some good info on doing this. Also rember, when veneering a substraight, always do both sides or it will curl up.

Bill,