Thursday, 11 December 2014

Reworking a Bow

Always interesting working other bows even though I'm not that keen on it. Hard exotic hardwoods are tougher to work than Yew.
Anyhow this bow has a few oddities the guy I'm doing it for had put a strange rubber boot over the lower nock to protect it... hmmm well, all it's done is retain the dirt and disguise the fact that one ply of the 3ply string had worn right through!

The wear is IMO primarily due to poor nock shaping, this is one of my pet hates. As a bow is drawn the angle of string and bow tip changes from about 15 degrees to near 90 so a simple straight edged groove can't fit the string at both brace and full draw!
The bow tiller seemed to be a bit stiff tipped and somehow looked a bit off, the more I looked the more I thought the grip looked too low down the bow, and to get it to sit on the tiller I had to support it just below the arrow pass ,even then it tilted a huge amount down on the upper limb.
So, I measure the arrow pass...
It was in the middle!
N'owt "wrong" with that as such, but it's more conventional to have it about 1" above centre.
Allowing for a 4" grip and 1" arrow pass you get a compromise. It's always a compromise of some sort as the hand and arrow pass can't be in the same place.

Just to illustrate:- Take a 72" bow (nock to nock measurement) with a 4" grip.
With the arrow pass dead centre:-
The upper limb is 36" long and the lower  32" long (36-4) that's a 4" difference.
Now with the arrow pass 1" above centre:-
The upper limb is 35" (36-1) long and the lower 33" (36-3) that's a 2" difference.
So just moving the arrow pass 1" makes a visible 2" difference... that's why we usually make that compromise. Not essential, it just looks more even, after all there are plenty of asymmetric bows just look at the Japanese Yumi bow.

Here are the before and after pics of the bow at 50# and 44# (lower pic) you can decide for yourself which you think has the nice tiller if indeed you can spot the difference.
Actually it's hard to see much difference as the lighting is different and the bow id supported on the tiller tree in a slightly different position. I took the weight off along the whole limb but mostly the outer 1/3 especially on the upper (right) limb.
By the way, I've tidied up the nocks... you can see from the line I've added to the pic' how at full draw the string would chaffe over that sharp edge.

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