Sunday, April 20, 2008

Sliding dovetails rock

It is getting warmer here, and it will soon be time to rig up the air conditioners for the house. Our house has radiant hot water heat, for which I am eternally grateful in the winter (not only does it cost less, but there's no roaring fan stirring up dust), but which means we do not have central air conditioning, and have to rely on spot coolers instead. To serve this need, we have a larger window unit that goes in the kitchen window, a smaller one that goes in the upstairs bedroom window, and a small "office air conditioner" that goes in the family room. This latter unit is a pedestal model with air hoses that go to the outside for heat exchanger air. Last year, we put this on a small table and ran the hoses out the window, stuffing the gaps with towels. (I meant to cut a panel for the hoses, but when I went to do so, my table saw shot me in the belly, a wound which took some time to recover from and which deepsixed that project for the season.) The table we used last year had the shortcoming that it was too low to allow the condensate tank to gravity-drain out the window (we had to drain it manually into a bucket every day or so). And we're currently using that table for something else now, anyway. So making a custom table for the air conditioner to sit on seemed in order.

I rooted around in the garage (which I had spent most of yesterday cleaning; we can now go in and out both doors with relative ease) and found a sheet of 4/4 melamine that was about the right size for the A/C to sit on. Some in-situ experimentation suggested that the best approach was to rest one end of the sheet on the windowsill, and mount legs on the other end. We added to this sides that would help keep the A/C from rolling off the table. These were cut down from some scrap 12 inch wide 4/4 pine stock that we bought from a cutoffs bin at Menard's a while ago, with a dado to receive the melamine cut on the back faces. This all went together reasonably easily, but the assembly lacked stiffness. This is where the sliding dovetails come in.

Using a router table, I cut stopped dovetail dadoes in the sides, near the front and the back. I then cut a dovetail into the ends of another piece of 4/4 pine stock that was laying about in the garage (we really do have a lot of scrap wood laying about), and then ripped that piece in half on the table saw, thereby guaranteeing that the two braces are exactly the same length. These slid beautifully into the sides of the table, creating a very stable and rigid frame. The front piece will be glued on (it friction-fits well enough on the front of the melamine top, but glue will keep it from falling off entirely), and the top slides into the dadoes cut on the sides and front without any fastening technology at all. All that's left are the legs, cut from a piece of 2x2 cedar stock, which will go between the front and the forward brace. I plan to attach them to the forward brace with screws. A stretcher made of a scrap of panga panga will go between the legs at floor level (once again using dovetail joinery), and the rear edge of the top will be screwed to the windowsill.

Did all the machining and a dry-fit assembly today; tomorrow evening we should be able to finish sanding and do the final assembly with glue, and then installation on Tuesday evening. Should be just in time for the cooling season to start. All I have to do after that is get some tubing for the gravity drain, and to make the window panel I was trying to make last year when my table saw shot me.

I even tempted fate by wearing my Wikipedia T-shirt, the same shirt that I was wearing when the saw shot me. There's even a small hole in the shirt where the piece of plywood ripped it on its way to hitting me in the gut. The most serious injury I got out of today's work was a small cut inflicted by one of the chippers in the dado set, while removing it from the saw.

Next weekend's projects include finishing the half-step I mentioned a couple weeks ago, and building an exterior support for the kitchen A/C unit so that it's pitched <i>away</i> from the house instead of toward it like last year. We got a nice puddle in the kitchen from the condensate drain, and I'd rather avoid that this year.