Saturday, 2 August 2014

Spliced Yew on the Tiller

This post is at start of play today. That's an important point, always check where you are before setting to work on a bow.
I've got it on the tiller on a taut string (but not braced) I've clamped a block in front of the bow to stop it flipping over. I took some video watching it flex and slowly worked it up to how it's shown in the second picture. The right limb was beginning to look a bit hingey on it's inner third so I didn't take it any further, (there is a dark mark on the belly at that point which makes it look like a thin point on the limb) the left looks pretty good.
It has the look of a beginners attempt at tillering, what I call square tillering, but it's early days yet.
The outer half of each limb needs to work a lot harder now. It's just my style of tillering, but I like to get the middle of the bow moving just about enough and then bring the ends round, plenty of people do it the other way. My view is that as long as I don't get the middle flexing any more than it will in the finished bow that's fine, what you don't want is to get full draw with the tiller wrong, or more deflection at any point than it will have in the finished bow. It could be argued that, seeing as how I started with a load of reflex near the grip I've already passed that point... well maybe I have, time will tell.
Without this check I may well have taken more wood off those inner limbs. I shall put on the tea and toast and pencil a big "LLL" (for leave... leave...leave well alone) on that inner limb before doing anything else.

You can see the tips are now back 10" so it could be braced.
There was a good discussion on Primitive Archer about longstring vs short string tillering and a couple of guys had worked out empirically that a slightly long string actually gave good weight/draw figures. E.G If we look at the second picture here it's pulling about 80# at 23" and they have found that when braced it turns out to be a similar figure.
Personally I go by tip deflection, then I brace and work from there. It will be interesting to see what figure I get when I brace it.

Update:- I've braced it and it was trying to bend sideways, with each limb going a different way... so, on average it was fine ;-) . This is why the tips are left wide!
I removed a little from the side of each tip to move the nock across away from the side it was trying to bend to, (it tries to bend towards the weaker side. I also removed a little from the belly on the sronger side to help balance it up. Back to brace and it looked much better, still a slight S shape but within acceptable limits It's mostly just cosmetic and some judicious tidying up as tillering progresses will leave it looking fine.
It's this stage of initial brace is critical, if problems aren't correct they will just get worse and I'd have ended up with a completely twisted bow. Correcting sideways bend and twist needs a careful approach, it's easy to get it wrong and make matters worth.
Just about done for the day, it's at 5" brace and pulling to 70# at 25" which extrapolates to about 95# at 32"
so you see I haven't actually got much poundage to play with to get to target weight & draw. I might ahve to use my ace in the hole and heat treat that right limb which seems weaker than the left, it's thicker but seems 'softer'.
Note the bow is stiff handled to take strain off the splice.

No comments:

Post a Comment