Saturday, 16 January 2016

Warbow Ups and Downs

This post really illustrates the trickiness of Warbow tillering.
I've slimmed the tips, straightened up the sides of the bow and rounded the corners some more.
Time has been spent checking for thick or thin spots by nipping up the calipers on the limb and checking that they will slide towards the tip but not back towards the grip. This ensures a continuous gradual taper.
I find I can now just string it using my foot on the long string, taking care to use my legs to pull and not my back. It's hard work as one is bent over at an awkward angle.
I've taken the winch off the tiller so I can flex the bow dynamically to look at the bend and its 90# @ 24" which interpolates to 120# at 32" so it's virtually finished and time to put on the horn nocks.

90/24= 3.75 pounds/inch
32 x 3.75 = 120 pounds
It can be calculated using only the power stroke rather than the whole draw length, but it's arguable which works best.
Now this raises the whole thorny subject of draw weight.
You can't actually measure it to any great degree of accuracy as it depends on so many thing, like:-
For how long has the bow been strung.
Temperature and humidity.
For how long it's held at full draw.
Has it been shot in.
An error of plus or minus 5 pounds is actually pretty good. I try for spot on or a couple of pounds over knowing that a bow will settle, but there are no guarantees.

Just to illustrate the problems I've been back and pulled it again after it's sat braced for half an hour and the draw weight has dropped significantly to about 90 at 26" !
I've exercised it and pulled it further and it's showing 100 at 29" This really shows that I should follow my own mantra of pulling to full target weight from as early as possible.
So what's going to happen? Is it going to be underweight?
Probably... BUT but I have a few tricks, I'll take an inch off each end, but I don't want to take off too much, and I don't want to heat treat it.
I'm taking out the little ugly deflex at the right tip and the deflex bend by the knot on the left limb (about a foot out from the centre). Just straightening out a couple of kinks can push the tips back an inch or so which will gain some weight. Mind whatever I gain in weight will probably be lost in tiller improvements to the outer limbs.
I'm rather beating myself up for being light, but that's probably rather unfair it's just that I'm my own harshest critic.
Probably do another post tomorrow.

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