Treasure chests in the pirate style with the rounded lid look a little tricky to make. They're not - here's how to make one out of old wood you may have lying around, and you only need one measurement. Here it is: 10 degrees. Right, you're ready to go!
I made the chest from some left over wood from our neighbor's fence. I'd used a fair bit of it to build a treehouse, and my kids were busting to have a piratey treasure chest to store their loot in. I thought I'd try my hand, and it turned out to be easy enough to share how to make it.
Step 1: Tools
This project is technically woodworking but requires no real finesse, just as well, or I couldn't have built it! However, you will need access to a power tool that only a woodworker would own: a table saw. This is really the only way you can accurately rip lumber. However, you don't need a fancy one with a cast iron table; though if you have one of those, I envy you, as mine is a crappy little store-brand bench saw that cost $75 new. A jigsaw is handy (though a fine-toothed handsaw would work perfectly well). You'll need a hand plane, and a hammer or a nailgun. Some ratcheting tie-downs are useful, but there are lots of other ways to apply the pressure to glue this project together. Oh yes, some PVA wood glue. You'll need a pencil, but you DON'T need any measuring tools. Really. No tape measures or rulers were exploited in the execution of this project.
Step 2: Pick a Length and Rip Your Boards
But... but... you said no measurements! Well, yes, but you have to decide how long your treasure chest should be. I just picked the length that would allow me to waste as little wood as possible - I had old six-foot long cedar boards, so I cut the rot off each end and got two lengths out of each piece. The wood I used was nominally 10 x 1, but it varied wildly in width and thickness. If yours are more consistent, your job will be easier.
Rip your boards at a 10 degree angle using a table saw, as shown in the photo to give them a trapezoidal cross section. Alternate the angle, and keep the fence setting for all cuts. If you organise things well, you won't waste much wood at all.
How wide do you make each board? Well, some simple circle geometry: you will need 10 boards to bring them around in a semicircle (9 joins between 10 boards, each join 2 x 10 degrees, so 9 x 2 x 10 = 180 degrees) and leave the outside boards vertical; you can use 9 boards if you're not fussed with this final requirement. The longest edge of your trapezoid is one eighteenth of a circumference, and the circumference of a circle is related to its diameter by pi (~3.14). So the width of your treasure chest will be 18/pi (about 6) x the length of the longest edge. So, for example, if your long edge is 2", your treasure chest will be a little less than 1' wide.
To make your life easier, your treasure chest should be no more than twice as wide as your widest board. You'll see why in the next step.
Step 3: Make the Ends
You generate the pattern for the ends just by tracing the trapezoidal outline of one of your boards 10 times on another board, as shown in the picture. The more careful you are, the better it will look. Cut to the inside line using a jigsaw or handsaw (my floor looked as in the picture after this step). Use the cut end piece as template for the other end.
Step 4: Nail and Glue
Glue and nail the boards to the end pieces and each other. I used a nail gun, but hammering in finishing nails would work fine too. You'll need to punch the nails below the surface.
Step 5: Clamp
How do you clamp something as weirdly shaped as this? Easy - use some tie-downs. I used the ratcheting type, which had, if anything, too much oomph. Strap them around and tighten until the glue starts to squeeze out. You could just use rope, and tension with a trucker's hitch. Wood glue is strong and pretty forgiving.
Step 6: Plane Smooth
After leaving the tie-downs on for 20 minutes, remove and clean the glue off (or if you're smarter than me, you would have put some newspaper down first to stop the straps getting gluey in the first place). Scrape the glue off. At this stage, it might not look too promising, but a few passes with the plane makes it come up really nice. I have a little Stanley block plane; it worked beautifully for this job. I didn't take too much off because I wanted to preserve some texture, but you could make the whole lid really smooth if you liked. Sanding optional. You'll also need to plane off the edges, because they'll have a bevel on them that you don't need.
Step 7: Make the Box to Match
The box must be the same size as the lid, whatever that happens to be. The depth is also optional - I just used the width of the old cedar boards I used to make the lid. Same for the base. Again, glue and nail; I didn't use clamps, but by all means do so if you have them. Now add hinges. I had a leftover piece of piano hinge, so used that. Real piratey ones on the outside of the chest would be way cooler.
Step 8: Paint and Add Hardware
We used leftover acrylic exterior paint, which hides a multitude of sins in one coat. A stenciled skull and crossbones would seem just the ticket!