Bending Boards for a Barrel-Top Trunk
A furniture-maker gets advice on bending barrel-stave-like pieces to form a domed trunk lid. June 10, 2006
Question
I am having trouble with the compound curves of a dome top steamer trunk. The top will end up with 5 boards 29 inches long by 3/4 inch thick by 4 to 5 inches wide. It resembles a segment of a barrel. This is the first time I tried to steam bend wood. I used 1 X 6 cedar planks for the top. I built the steam form allowing for approximately 40% springback. I steamed the boards for 80 to 100 mins, but had problems getting the compound bends. At times the planks would kink instead of bend, but did not ever want to bend in both directions. The top measures 29 inches by 18 inches. The finished top humps a max of 2 inches over the 29 inch length, and 5 inches max over the 18 inch width. The 18 inch width is made up from the 5 boards, so each board is not too heavily cupped. Has anybody any experience in making dome top trunks or barrels?
Forum Responses
(Furniture Making Forum)
From contributor D:
Barrel staves are bent in one direction only, with the edges shaved at an angle and tapered towards the ends to give the assembly a curve in two directions. To get a smooth outside surface, the faceted surface is planed or shaved smooth.
From contributor K:
Softwoods are not good for steam-bending - the cell walls are too long and thin, so the cells just deform under pressure but retain their memory. There is a good little free download at Lee Valley Tools. They also have some tools, but you should read the little book first - any missed detail will lead to a failed attempt.
From the original questioner:
Thanks. I think it is more of an art than a science to make this kind of thing. If I only bend the wood in one direction, I would have to start out with a fairly thick plank to end up with the curve needed, but I am sure that is how barrels are made. I also agree that oak may have been a better choice for bending. I have not read anything about bending cedar other than in boat building. I have a copy of that excellent little Lee Valley book, but I did not know that it was online. I have been thinking about resawing the planks in half (thickness) and trying to bend and laminate it.
If anyone has ever tried to make a dome top steamer trunk, I would love to hear how you made out and your procedure.
From contributor K:
I made a sculptural piece that sounds similar to what you are doing. Most of the sides and top bulging curves were made from 8/4 stock with the curve sawn in, rather than bent. It is surprising how much curve you can get once the bevels are cut and they are glued together. It sounds like you may be overdoing it on the curved part. Not having seen your design, I have no right or basis to say for sure, but sometimes just a little bit makes a lot of difference.
From the original questioner:
I steamed up a couple of boards and left them on the bending jig for a week to dry. When I unclamped them, they sprung back around 2 inches total, but that still left them 1 1/2 to 2 inches over bent. I am making up a new, lower bending jig that looks like it will give me a lot better chance of success. With any luck, I will be able to get some of the compound curve from bending and the rest from joining/sanding/shaping. If not, I will go to thinner pieces and laminate. Anyway, I will bend another piece and dry it for a week to see how that comes out.
From contributor R:
Cedar is a bad choice for bending... fractures badly. Check out The Woodbenders Handbook by Lou Scheirling(?). Great book - use it all the time. Oak is about the best choice or ash is just as good... but I have bent cherry and walnut with ease.
