Hi All,
Here are some pics of a quickie Bhutanese style bow that I've made during the cold wet nights over the past couple of weeks. It survived a field shoot this weekend just past, and so I thought I'd post it now
I was prompted to make this bow after a chat and meeting with a neighbour bowyer friend of mine - Dave Sinfield. He had made a quickie bow in the same style, but he hadnt got to the point of finishing it. I could see some fun and/or experiments in making one. There is a similar but one piece bow in TBB4, which also provided some inspiration, so thanks guys for the book. I bartered an archery club egg'n'bacon sandwich and a cuppa with Dave for a piece of the best bamboo pole he had left - a half split pole of about 4" diameter, and 40" long.
I split the half pole lengthwise into quarters with a knife, and then sanded the inner nodes down on one quarter, until the thickest ends overlapped and fitted reasonably together for about 8". I then fixed the halves to each other by bedding them into some araldite expoxy. The fit was locked in place by using two offset osage pins with expanding wedges, driven into tapered holes in the handle - these are just about visible in the pictures of the handle area.
Once dry, the bow was initially tillered by plain straight tapering to pin nocks from the handle flares. Also of course there is a natural reduction in the thickness of the bamboo culm, which helps. I could not resist gluing on some small pieces of horn to protect the bamboo from the string. I worked the limbs down to near points, each tip being around 9mm, with a 4 mm pin (sorry about mixing my units, but I cant find my old imperial ruler to measure
) to hold the string loop.
Initial tillering on the pulley was rather fraught, as there were plenty of creaking and cracking sounds on every draw of the bow. Closer examination showed that the inner surface of the bamboo, which is serving as the back of the bow, had many shallow cracks in the natural waxy surface. The more the bow was drawn, the more cracks appeared, but none of them seemed to get any worse, so I shrugged to myself and carried on. I had in mind the warnings from TBB4 page 152, about flattening the concave surface as much as possible, but I wanted the bow to make a little weight, so I left it a little wider.
The tillering was quite quick in the end, as it was nearly right when first stretched. I made a string out of 6 strands of BCY450 (not primitive, but really good stuff), served it, and then shot a few heavy arrows into the ground in my back garden. On every draw, the bow creaked loudly and caused me to grit my teeth, but no fatal problems occurred
Then I found that as well as the cracks, the ends of the araldite bed had separated from the bamboo, so it was time to reinforce the joint. I decided to use some 1" fine rawhide strips soaked in warm water, and then steeped in white PVA woodglue. These were tightly wound on, and held in place with thread until dried and shrunken. This worked well, and although the bow still creaks occasionally, it is now very solid in the handle section.
The bow was now working, but only a very poor draw weight for its size (68" nock-to-nock, 2" wide at the flares), probably 25-30lb at 28". This is generally because the bamboo culm is fairly thin, and real Bhutanese bows are made of much thicker and tougher bamboo. Having read TBB4 I thought I'd have a go at heat treating the bamboo. This was done with a 1600W electric heat gun, while the bow was strapped down in reflex on a caul. When restrung, the bow was noticelably zippier, and after a few pulls and a little tiller correction, the bow pinging arrows happily into the back yard again.
Since the bow had survived so far, despite the protests it was making, I decided to give it a quick coat of floor varnish. This would be necessary to protect it from the damp of a winter 3D shoot I intended to attend with the bow at my club.
Last weekend I shot the bow, and was pleasantly suprised. Mainly because there was absolutely no handshock, none at all. Secondly because the performance wasnt bad for a 30-35lb @28" bow - I shot some old 9/32 diameter arrows of 360-380 grains weight and the performance was quite acceptable. Plus of course, the bow held together and recovered its reflex about 15 mintes after shooting with it all day. I am very happy with it, considering the relatively quick build and tillering time.
Ok, now the pictures. Sorry I havent managed to get any full draw shots, but they could maybe come later.
//Bob
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