Some ancient time ago I saw a sketch of an old 19th century (?) joint that was used for making outdoor weatherproof chests in 3/4" pine or similar. It was a dovetail, AFAIR, but there was also some way of seating oakum into the joint to improve weather sealing.
Anyone got any bright ideas on how to do such a thing ?
Leaving room for caulk was a "design feature" of many of my early attempts at dovetailing, and I occasionally do one like that just for practice.
Saw where Frank Klaus (sp) the King of Dovetails was making a pine, waterproof box on Roy Underhill's show once that may give you an idea or two. The box was for holding water that held the stones he used to sharpen his chisels and plane blades.
As I recall, he didn't do anything special to the dovetail joints since they would swell and seal shut after the box was filled with water. The box was not treated or finished. Along the bottom of the side pieces, he took a bent, hard wire that he lightly hammered into the sides making a groove about 1/8" deep and wide the length of the side. After compressing (indenting) the wood by making the grooves, he then planed the bottom edges until the compressed wood could barely be seen.
He then assembled the pine box using plain old nails to hold the bottom to the sides, with dovetails holding the sides together. Filled the box with water and no leaks. As the water soaked into the wood sides, it would cause the compressed wood to swell - creating a water tight seal. The dovetails also sealed after the joints were exposed to water for a few moments.
Bob S.
It was really cool the way he got the bottom of the box to seal:
1.) Once the box (minus the top and bottom) was assembled (no glue), he used a finishing nail (laying on it's side) to create an indentation all around the bottom edge of the piece. (Basically created a valley in the middle of the wood along the bottom). 2.) Next, he planed (by hand, of course), the bottom of the piece until it was almost flush with the indentation. 3.) Used a sponge to then wet the wood and raise the indentation back up, essentially creating a wooden gasket of sorts 4.) The last step was to use the finishing nails to nail the bottom on the piece, with nails every 1.5 - 2 inches.I always thought it was really cool the way it all worked out...
Regards,
I have Japanese drinking cup just done with finger joints. No nails, no wires, no caulking, no nothing else, just the finger joints and its water tight. How they do that?
They fit tightly, they're smal enough that they don't get racking stresses and they don't stay sealed forever. If you have some paulownia or lime (basswood) it's a good exercise to make a couple.
The "gasket" trick is a good one, but it only works for long grain. I already use it for sealing the boards in the bottom. What I'm after here probably needs to be a groove to take some glued or tarred hemp string. I think I'll saw the inside corner at 45° and caulk into that. It's for a reasonably big chest to be used for camping.
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