At last, that curved baseboard!

Posted by Steve on Thu, 05/03/2007 - 12:02pm

I've been pushing off this little project for a couple of months. The bedroom renovation began with construction of the closet and the curved plaster corner I absolutely had to have (if for no other reason than I'd never done one before). I knew that was going to create problems with the trim later but, hey, later is later. Six months later, later became today.

There are basically four ways to build a curve using solid lumber. One is to steam it and bend it in a jig. Bending 1" nominal hardwood stock to as shallow a radius as I need is probably impossible, at least with my skills, and since I don't have a wood steamer anyway, it's moot. So let's move on.

The second method also involves a jig but instead of bending solid lumber you build up thin veneer layers like plywood. You can construct a very small radius this way and lots of glue ensures a stable curve. The third way is to saw lots of narrow vertical kerfs in the back of the stock, leaving a thin facing layer to make it bendable. It's tricky but this method wouldn't work for me anyway because the board has a half-lap detail.

I chose Option #4: build up the curve using several narrow pieces of lumber edge-laminated together. It's not really a smooth curve however but a polygon... kinda like the difference between a raster and a vector curve. However, since that's how all the convex curved woodwork was originally built in this house, it's Authentic. That's my story and I'm sticking to it.

So how do you calculate the miter and width of each piece? Fortunately, dumb luck made this almost a textbook exercise. The corner's circumference is eleven inches. If I were to use one-inch wide pieces how many pieces would I need? You, the kid in the back corner. That's right, eleven pieces. But how do you calculate the miter angle for each piece? If you glue together eleven pieces of lumber you have ten joints. A 90 degree angle divided by 10 equal joints would mean that each joint would have to be 9 degree corner. Since a corner is two equal miters, then the miter is 4.5 degrees.

Am I smarter than a fifth grader or what?

Alright, there's a bit more to it, like the fact that the face of the baseboard will have a larger circumference than the back, but a little guesstimating set the width of each piece to 1-1/8" at the face. Close enough.

Construction was pretty routine except that clamping was a bit of chore once the curve extended past 30 degrees. So I constructed the baseboard as three sets. Then I assembled them around the jig I'd used to make the knife to construct that plaster corner: a plastic bucket. A strap clamp held the pieces snug while the glue dried.

It still needs cap and shoe mouldings and, of course, it would look better actually attached to the wall. More to come.


I've read about this being done, but this is the first time I've almost seen it done by someone I almost know. Is there also a crown set? That's going to be a beautiful corner!

Posted by Steve on

Thanks. Whether or not it's beautiful or a mortifying hack depends on the remaining trim, which turned out be a little more involved than I thought. The old "there ain't no screwup a sander can't fixup" thing doesn't apply well to profiled trim. I hope to get it done over the weekend.

Posted by Kathy (not verified) on

It's really beautiful. You are incredibly talented (and patient).

Another subject - some time back you mentioned that you were able to purchase efficient light bulbs that would work on a dimmer. I have four 120-watt floodlights in the kitchen on a dimmer switch. Today I bought two fluorescent floodlights to try out (I forgot about the dimmer thing) - will I blow something up if I install them? If you don't recommend, I'll return them.

Posted by Steve on

I found some dimmable CFLs (compact fluorescent lights) on Google. However, while not recommended and this comes with no warranty implied, you can dim a standard fluorescent down to about 50% brightness. You just have to turn it full on first and then dim it down. Beyond half brightness, you risk damaging the dimmer because they're not designed to work with an inductive load like a ballast transformer. There are special dimmers called variacs that work with fluorescents.

Posted by Anonymous (not verified) on

Hi, did exactly the samewith oak but with 2 curves and a straight section in between. All looked nice untill the decorator varnished it, now you can see dark lines where the joints are. I am trying to solve this, but would be interested in wether you had the same problem, if so I really need the help to sort it. By the way, satisfying isn't it!

Posted by Steve on

I got lines too:

They're not too objectionable but they smack me in the face whenever I look at that corner. It's just the nature of stain, I think. I tried sealing the wood with a clear oil conditioner first, believing that would eliminate stain being absorbed by the seams. It did, to a certain extent.

Posted by Anonymous (not verified) on

I talked to an instructor at colege and his explanation was that unless the joins are extremely tight, capilary action draws the varnes or stain into the end grain of the joints, and end grain stains darker than the face. Sanding won't do much as the stain is drawn into the join. His suggests kerfing the board but just stoping short of the top, as the moulding does not have as much wood as the rest of the board it shoud bend, or you could kerf the board with a mitre saw and the moulding part with a thin bladed hand saw, maybe also soaking it.

But I first want to try using oak veneer on the flat part of the board first before I try the above, any comments?

Posted by Steve on

Back-cutting kerfs is one of several ways to do something like this. It wouldn't have worked with this moulding though because of the rabbeted profile on top of the board. The best solution, I think, would have been steaming the board in two or three passes with three jigs of decreasing radius. That was a lot more involved than I wanted to get though so I used a barrel stave approach.

Building up layers of veneers will also work so long as the board doesn't have a face profile and you don't see the edge.