Made from green Hazel.
I made a couple of pegs to secure the ends of the blade. (I have seen split rings recommended, and also a small nut/bolt combination to achieve the same end.)
First of all I determined which way the selected rod, or bow, wanted to bend under compression and then made the slits in line with the bend. To guesstimate the final length of the rod I fixed the blade in one end. This end I placed on the ground and then, with the rod oriented vertically, pressed down on the end of the rod to get a good bow shape while holding the free end of the blade adjacent to the rod. I then marked the rod where the holes at the end of the blade should be in the final version and added 25mm (1") or so to allow for the blade to be recessed into the rod. I cut it at that point and made the second split and fitted the blade. Having the peg in the end of the blade is a great help when manipulating the blade and bending the rod for the final fit, as would a split ring be.
I made the splits in the Hazel rod with a knife. You could probably also make the splits with the blade itself and a baton. The splits didn't seem to "grow" under the tension of the bow over a couple of days although they might with heavy use. I guess you could always seize the rod with some strong line or snare wire to prevent the split growing if necessary. Or notch the bow to retain the pegs. Or make a new one.
In hindsight I think a slightly thinner Hazel rod would have been better as I could have bent it further to get a larger bow, thereby increasing the thickness of the logs I could cut (and possibly minimising the risk of the splits growing). This rod was around 20mm or 3/4" in diameter.
I thought I'd have go at a "expedient" buck saw.
Rather than carefully making joints I tried using notches to stop the "joints" slipping. The spreader is trimmed at each end to a sort of screwdriver tip shape and the notches made in the uprights. I also made a small groove near the top of each upright in which the tensioning cord sits to minimise the likelihood of it slipping off during use. In hindsight a simple notch on the outside of the frame would probably have sufficed.
Version 1 had a simple horizontal spreader bar and this was hopeless as the whole thing just "parallelogrammed" around the spreader in use. I guess this doesn't happen with the nicely crafted buck saws as there's a nice (mortice and tenon?) joint to provide rigidity.
Version 2 had a diagonal from the spreader bar on one upright to a notch just under the tensioning cord on the other upright. This felt pretty rigid but as soon as I used it it "parallelogrammed" slightly and the diagonal fell out, reverting itself to version 1!
This one is version 3.
It works fine - as long as you hold it at the Y end. Otherwise the upright tends to "parallelogram" around the spreader bar. It cut through a 15cm/6" log without problem.
Again hindsight would suggest thicker uprights so I could get more tension on the blade. These were around 20mm or 3/4".
Once you've found your sticks you could make this expedient bucksaw in a very few minutes.
Mors suggests "saddling" the spreader on the uprights and also carrying and using a few small nails to make the bucksaw more stable. This saddling of the joints may have made versions 1 and 2 a bit more stable. Maybe I'll try sometime.
Of course, one of these is pretty good but costs a lot more than a bent stick!
Finally, the tightest I could really bend the blade without damaging it was around 20cm/8" diameter so your billy would need to be this diameter in order to carry it this way. Some people seem to carry the blade in a piece of split hose pipe. Or a very expensive bow saw blade belt!
I am not young enough to know everything.
Thanks for the nice pictures and hard graff on you.
nothing in the world is more dangerous than sincere ignorance and conscientious stupidity.
Thanks guys. Trying stuff and making mistakes is a good way to learn...and then this forum is all about passing on that info and wisdom "around the campfire".
Now that looks like a good days play, love the different versions. Thanks for sharing