Tuesday, 9 August 2016

Not Much Room Inside

Blimey the seasons are moving on apace. My neighbour's apple tree is one of the first to start dropping fruit, they leave the windfalls on our front porch and I give 'em a litre of last years cider. I've got the apples stored on the garage floor on an old bamboo roll up blind, add in the Yew I have on the floor and I'm running out of room. I don't think it will be a big apple harvest this year due to the late frosts.

I've pressed on with the Osage flight bow and it's beginning to flex. The string line is good, I'm a bit scared of it, It's not braced yet and I've only pulled it to 55#... now from my own advice I know that if you want a 70# bow, you have to pull it to 70#... I don't want to end up with a 55# bow, but I also don't want to over-stress it until the tiller is looking good.
You can see from the pic the tips are back just about far enough to brace it, so I should give it a careful try at a low brace.
Maybe I'll heat in a little deflex at the fades and recurve the tips a bit more.

The problem is, I don't want to use all the bend up just bracing the bow, but conversely, that's the way to get a flatter force draw curve. Bottom line is... it's all guesswork. If I end up with the nocks about in line with the back of the bow and a reflex/deflex shape that will do fine.

To put it simply and to exagerate slightly:-
Do you have very thick stiff limbs deflexed back to almost brace height so the early draw weight is low, but it ramps up very sharply and the limbs don't actually have to bend back very far to reach full draw. Or do you have thinner softer limbs with a lot of reflex which takes a good poundage to get braced and the early draw weight is high and it comes up smoother and slower... BUT the limbs actually bend a much greater distance from unbraced to full draw?
Obviously with modern materials you can go for the latter, with natural materials it's less straightforward and to be blunt the maths/physics is verging on the impossible. Even those who have analysed this stuff rely on vast simplifications, and those who try to explain it in layman's terms are often somewhat confused. Just try to explain or understand exactly how reflex achieves an improvement, and why. Is it an improved force draw curve? A better acceleration profile? Is it due to change of string angle or an effective shortening of the limbs as the string makes contact?I know enough to recognise I have no idea and I just go by gut feel and watching the wood.

Update:- I've evened up the right limb a tad, had it on a low brace and back to 60#. Then I clamped it up to heat treat in a little deflex. I'm following my old adage of doing about half as much as I think I should.

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