I copied this from the thread in the outdoor gear forum to post here also.
Nice job on that saw, I would enjoy seeing how you built it, and what materials were needed.
Thanks John, here's a list of materials.
I just winged it after looking at a few vids & pics of others on the net.
Side supports: 48" 1x2 oak cut to 14" ea.They were out of shorter pieces so I had to go with the 48".

The 1/4" slots for the center support are drilled at 7 1/2" on center from the bottom x 1/2" deep.
I drilled 2) 1/4"holes at 5/8 width & dug the center wood out with a pocket knife.
The slots for the blade are 5/8 deep & the holes are drilled at 1/2".
The holes for the tensioner are drilled at 7/8" down.
Center support:36" x 5/8" oak dowel cut to 19 1/4" with 1/4" thick end tabs notched to 1/2".
Top tensioner:24" 1/4-20 all thread cut to 22", then I cut it in half to make it more packable.
1)1/4-20 x 1" rod connector.
2) 1 1/2"x 1/4-20 bolts.
4) 1/4-20 wing nuts.
1) 21" bow saw blade.
I shaped the handle with a half round file & sand paper then gave the wood a coat of satin acrylic.
Here it is packed up.
Too bulky for a pack, but not for a truck/car.

I added pieces of rubber hose to the rod ends to keep the wing nuts from rattling off.