Monday, 5 September 2011

Ready for the Tiller

The bow is now straight (that's to say the tips and grip are in line).
The first limb I worked was forced to be certain dimensions because of a knot in one area of the limb and the basic dimensions of the stave. I've evened up the thickness taper on that limb by staking the thickness near the grip and then the thinnest point and working out roughly even steps along every 6" of length (it worked out at 1.5mm change every 6").
I don't work slavishly to dimensions, what I'm trying to do is get a fairly even taper with no thin spots which could turn into weak points where the bow suddenly bend excessively (known as a hinge).
So with the stave having dictated the dimensions of one limb, I then make the other limb roughly match it, which is where I am now.
I felt the flex of the bow by putting one end against my foot, holding the other end in one hand and pushing against the grip (a bit like when you string a bow). It feels a bit soft for this stage in the proceedings, but there's no way I could have made it much different.
On the plus side, I flexed my 50 pound longbow and it felt similar, so I'm not too far out. The other good thing is the stave is still long and could always take an inch or so off each limb to get the draw weight up. The final trick up my sleeve would be to heat temper the belly.
Ah, but I'm getting ahead of myself, lets get it on the tiller and see how it flexes.
The second pic shows how I make a virtue of necessity.
One big knot couldn't really be in a limb, therefore it must be in the handle, which then takes on a slightly pistol grip shape:- Note the arrow pass is marked, and you may just be able to see the centre line marked on the belly.
My suspicions have been confirmed, it's a tad soft and the undulations make the shape look weird. I shall do some heat treating and straightening/adding reflex.
I don't want to loose any length yet as you can't put it back on again!
If I do the heat treating now, it can have a couple of days to rehydrate the wood. Getting the limbs a bit more symetrical will help to see the true shape as it's drawn back on the tiller.
At one point I pulled it back to 30 pounds at about 27" on a low brace height...that's just too weak. The top limb looked to have a horrible bend just above the grip, but as I let off the tension I could see it 's just the shape of the stave.
The doesn't seem to be any set at all (hardly surprising on a long bow at 30 pounds...)
Off to the garage to break out the heatgun.

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