10-08-2008, 02:48 PM
I use a metal oil drum. You'll find that the plywood will bend and stay bent easier if you soak the wood for a few days first. I made a simple box from wood scraps, and put a piece of thick black plastic sheet inside, then fill it with water, and sink the board with a couple of bricks or rocks. Put in the sun, it will warm the water (assuming you have sun where you are) and become soaked quicker. It takes about three days for the wood to dry. Put it in a dry place, or put a lamp inside the barrel to add some heat.
Along the outer edges, be sure to put a board lengthwise, so the ratchet straps don't dig dents into the wood. When it's dry, they will remain there and be difficult to correct. Put the straps at the ridges of the barrel, and you will minimize that dent, though.
An oil drum is about 24" diameter (~60cm). Make the curved strips the same way, soaking them in the same tank. Cut more of them than you'll need, as some will break when you curve them. Curve them over the barrel in the spaces between the ridges, and you will get a slightly tighter bend. That's important, because it will all want to straighten out when it comes off the barrel. I suppose you could rig up a steamer for the wood, but use hardwood like ash, for example, as straight a grain as you can find. Pine works, but you'll lose about 40% of your strips to breakage.
Once it's all together, it will hold its curve, because the strips on the back will have a slightly different radius than the shield face. Geometry dictates that the two must both move for either to move, and it holds itself under tension. Some peened over or clenched small nails will hold the curved strips in place while the glue dries.
That's how I do them, though there are those who say that's not an accurate system. I agree, but it's what I do, nevertheless.
If you decide to go with the wood strips layed up like the originals, the whole technique is much different, and I can't really advise you on that.
Along the outer edges, be sure to put a board lengthwise, so the ratchet straps don't dig dents into the wood. When it's dry, they will remain there and be difficult to correct. Put the straps at the ridges of the barrel, and you will minimize that dent, though.
An oil drum is about 24" diameter (~60cm). Make the curved strips the same way, soaking them in the same tank. Cut more of them than you'll need, as some will break when you curve them. Curve them over the barrel in the spaces between the ridges, and you will get a slightly tighter bend. That's important, because it will all want to straighten out when it comes off the barrel. I suppose you could rig up a steamer for the wood, but use hardwood like ash, for example, as straight a grain as you can find. Pine works, but you'll lose about 40% of your strips to breakage.
Once it's all together, it will hold its curve, because the strips on the back will have a slightly different radius than the shield face. Geometry dictates that the two must both move for either to move, and it holds itself under tension. Some peened over or clenched small nails will hold the curved strips in place while the glue dries.
That's how I do them, though there are those who say that's not an accurate system. I agree, but it's what I do, nevertheless.
If you decide to go with the wood strips layed up like the originals, the whole technique is much different, and I can't really advise you on that.
M. Demetrius Abicio
(David Wills)
Saepe veritas est dura.
(David Wills)
Saepe veritas est dura.
