Thursday, June 26, 2008

Research on Waterproofing Wooden Furniture

I'm working on a pair of knock-down benches on a design by my friend Sean. These are being built with the ash I purchased last fall. I've finished gluing up the tops in one big panel that will be ripped down for two bench tops and one or two stretchers (as yet to be determined) Once the cutting gets under way, these should come together in under a day.

Since the benches are intended as camping equipment, and last year's two-week camping trip included 6 consecutive days of rain, I need to waterproof these appropriately. Some quick research turned up a couple sources.

First, from the U.S. Government, I found a short piece on finishing wood for outdoor use. This one sticks with traditional Big Box finishes—paints, stains, and varnishes—rating them on appropriate use. This gave me some thought: did I want to paint the benches, as this article suggested. Not really. And Ash wasn't on the list of recommended outdoor woods. Hmm.

So I started thinking about wooden boats, and my trip to Mystic Seaport last year. What would a boat builder do? Assuming that a boat builder would use ash in the first place. I turned up two more sites of interest: one about spar varnish and the other about a homemade polymer coating. As intriguing as the homemade option is, I think I'm planning to track down some spar varnish. I found three brands that seemed promising: Sutherland Welles, Man O'War, and Z Spar. I think one of these will end up on the benches.

If anyone has suggestions or cautions on finishing these benches correctly, please chime in.

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Wednesday, June 18, 2008

The Promise of Pinch Dogs

This week I conducted a quick experiment: I jointed a couple of warped scrap bits to see how the pinch dogs I received last Christmas would work. The first thing I learned is that pinch dogs want roughly even surfaces: I knew they could go around corners (for mitered joints or more difficult multi-angle glue-up), but it didn't seem likely that they would work on the ends if the surfaces were not relatively coplanar.

Out came the hand saw (it was late and children were sleeping) and I cut down the longer board to roughly the same length as the shorter board. Then I smeared both edges with glue and started pounding in pinch dogs.

Thats when I learned that this tool could benefit from a little help when being applied. I would have liked to have a couple straight pieces of wood clamped together on each end of the work piece to keep the boards in the same plane. It also would have worked better if the boards were lightly held in place on the bench and had not been cupped (and therefore more like a rocker than a pedestal).

Even with these challenges, I managed to clamp the boards using these glorified staples, and set the assembly aside to dry. That was Monday night. When I came back to it this evening, I set it on the bench and it looked like the picture at the top of the page. The joint looked tight in spite of the trouble I had during glue up, but the rough cut surfaces and misaligned edges could be hiding the reality.

To get a closer look at the joint, I planed the surface down until the joint was revealed. Sure enough, the pinch dogs had done their job and held the joint tight. If you look closely at the picture below, you might see the joint, but it is tightly glued. The holes are visible where two pinch dogs held the joint together on the surface, but there will be many projects where that holes like that will be concealed. I expect to use these for the bench project I'm working on now: the holes won't be visible on the underside of the benches, and I've rough cut the stock long enough that I can trim off the ends after glue up.

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Monday, June 16, 2008

First Dovetail for an Eight-year-old

Here's a great post by Konrad Sauer about his son's first through dovetail. This is the kind of experience that blow me away about being a parent.

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Thursday, June 12, 2008

Pile of Boxes and Warping Lid

I went to an event that had a marvelous door prize: 18 boxes made by my friend Sean. These were intended as prizes for a tournament, but there were only 23 entrants total, so almost everyone went home with a box. These boxes were made from some of the ash purchased at the same time as my stock pile.

As a member of one of the tournament teams, I came home with one of these boxes. It sat in my front hallway for the last four days, looking pretty. But now that the heat and humidity have returned to normal levels, the lid and front side are starting to cup away from the box. In part, I think this is a case of grain orientation; in part, a case of excessive moisture. I've taken the box into the basement and lightly misted it with water on the cupped sides. I've also cracked the lid to get the inside drying faster. I don't know if either of these actions will help, but it's worth a try.

Now I'm worrying about the benches I'm making, and hoping that the better treatment of my lumber (painted ends and tarp over top) will mean less moisture content. I did some research to see if you can figure moisture content without a meter, and found a method for calculating moisture content with an oven and a scale.

Perhaps I'll try it before building my benches.

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Tuesday, June 3, 2008

Box Assembly

Yesterday night I returned to the shop. The bottom and insides of the cherry dovetailed box had been finished with two coats of Tung oil finish and a coat of wax. The finished cherry glowed almost golden, practically begging me to glue it together.

Having come this far without incident, I wanted to be sure to get the glue up right. I checked my labels, still visible on the outside of the box, and laid out the parts in relative position with the bottom in the center. I placed the sides with the bottom slots of each piece laid alongside the bottom. I had clamps ready if I should need them; also a 12" rule, a mallet, four pine blocks cut with fingers slightly thinner than the tails, glue spreaders and glue cup cut from a small paper cup, a spray bottle of water, paper towels, and scraps of cherry created when I cut the dovetails.

Surveying the scene, I ran through the process in my head. It seemed that everything I needed lay in front of me. I used some poster putty to temporarily attach the paper glue cup to the bench top (have you ever chased a glue cup under the bench while your open time was ticking away? I have.). Then I poured enough wood glue into the cup and started spreading glue on the long grain of the pin boards. Perhaps I should have also spread glue on the tail boards, but I chose not to do so. I knew the tails had a fairly tight fit, and I wanted to minimize squeeze out.
After adding glue to all the pins, I lightly inserted one set of tails into the corresponding sets of pins, first on one side and then the other. Using one of the pine blocks to protect the cherry side from the mallet, I tapped the end home, working alternately from one edge to the other. When that end was set, I turned the box over and slid the bottom into its slot, then repeated the process of inserting the tails and driving the second end home.

I now had a box. Using the 12' rule, I tested for square. Then I looked at the inside for squeeze out. At this point I realized two sections were not driven all the way home, so I applied the mallet just a little bit harder to drive them into place. The box was still square, and there was only one spot of squeeze out. Since the inside was already finished, cleaning this was no big deal. I sprayed a paper towel lightly with water and wiped away the glue spot.

At the last, I looked at the dovetails critically. Only one spot looked like it needed significant help, so I made a small wedge from one of the cherry scraps. I dipped this in glue and lightly tapped it into the gap (making sure to line up the grain so it would appear to be part of the pin – I think end grain hides better than edge grain and its easier to make the wedge that way). So now the assembly is done. My only worry is that I may have driven this wedge a little too far and deformed the tail enough to be noticeable. We'll see tonight when I trim it flush.

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