I've heat treated the inner 2/3 of the left (lower) limb with it pulled down with rubber strapping to try to take out a little of that ugly deflex kink and to stiffen it mid limb a tad.I didn't over do it or clamp it down hard. Here's an annotated pic of it after the heat treatment and a pic of it at 100# pull, you can see the tiller is looking a bit better and it's stiffened it up by an inch.
E.G It was 100# at 29 before, now it's 100 at 28" despite me narrowing the left outer limb a bit more!Tillering undulating staves is tricky as the undulations visible in the unbraced stave should still be visible at full draw.
Video here:-
https://youtu.be/x2k-oYHxQIo
Since taking the video I've eased off the outer 1/3 of the lower limb taking a little off along one edge which was a tad thicker than the other, using a fine rasp but mostly working with the scraper.
It's remained strung all this time. Then I flexed it dynamically on the tiller increasing the draw each time up to 32", it looked to be about 115#, but couldn't read it accurately as I was watching the tiller and the draw length.
I'm much happier now, and I think this whole build has really shown the problems of tillering a warbow. I'll take some more video once it's been exercised some more.
I think it also shows how you really do need to be pulling full draw weight from the start. Maybe it also shows that I'm wrong and that with a warbow you need to work to dimensions early on to get you close enough to put it on the tiller and brace it.
the real problem has been that its the first warbow I've done for a while and it's tricky to go from a 42# primitive straight onto a warbow... If I do another warbow now, it would doubtless be a simpler job.
Out of interest I've taken the thickness figures from each limb at 6" intervals and averaged them.
I've then looked at how much each reading dropped from the previous.
E.G My rough out figure is 2mm reduction every 6". How does this compare with the finished bow?
One would expect it to taper more severly near the tip and less severely near the grip.
Here are some figures starting at 32.2mm thick at the Centre Line (CL):-
6" reduces by 2.45 mm from CL
12" 2.3mm from the previous figure
18" 1.3mm from previous
24" 2.35mm from previous
30" 2.65mm from previous
36" 3.45mm from previous
tip 5.25mm from previous
This shows that the 2mm every 6" is a reasonable rough out figure, but needs treating with some caution as it will give stiff tips. Mind, that's the way I tend to tiller (from the middle outwards).
Plotting the thickness figures shows a dip down from the grip area and then a nice smoothly increasing degree of taper to the tip.
CL 32.2
6" 29.75
12" 27.46
18" 26.15
24" 23.8
30" 21.15
36" 17.7
Tip 12.45
Hi,
ReplyDeleteNice work on this warbow!
I'd like to know the specifications of the tillering string: the material and the number of strands?
I'm fed up with my big dacron tillering string!
Cheers.
ReplyDeleteI've just had a look at the tillering sting its 14 strands of Angel majesty or maybe AstroFlite (which is what I'm using at the moment. I just use the cheapest of the good quality low stretch materials.. they are all very similar)
It's a continuous loop string (e.g The loops will be just 7 strands, but I normally lay in an extra strand or 2) The loop is formed by serving a 4" length and folding it back to form a 2" loop that's big enough to go over a roughed out stave. The overall length is enough to go on the longest bow you can imagine making. An ald ball race or a ring of aluminium makes a good string adjusting toggle.
You could easily get away with fewer strands as the string won't be subjected to the actual stress of shooting. Extra serving and some figure of 8 binding at the base of the loop is a good idea as putting it on a big rough stave tends to stretch out the loops, but it doesn't matter too much as it doesn't actually get used for shooting.
thank you very much !
DeleteI've just looked for a spool of Astroflight but I fell on prices higher than for a reel of angel majesty (already enough expensive), so I wonder where you buy your string material ?
I usually by for Quicks or Merlin, depends on price or if I happen to be near Quicks and can save postage.
ReplyDeleteI use lower thread counts than some people, make it less expensive, usually 8 strands up to about 60# and then 10 up to about 70#. 12 strands for warbows.