Thursday, 25 September 2014

100# Warbow Collected

The guy came over today to collect the 100# Warbow and the 60# Hickory backed Yew, he was very pleased with them but unfortunately was in a hurry, so we didn't get out to shoot them. I'd been hoping to get some pics of him at full draw and to see his face when he loosed a flight arrow.
I took a few pics of the bow before he arrived and also took some measurements to see how it compared with the Mary Rose bow I'd taken the initial measurements from.
Measurements are distance from centre line then width and thickness in mm.
                       Mary Rose         my bow
centre Line  34.5  32.7           38.5  33.4
200mm        32.8  29.7           36.3  28.5
400mm        30.1  26.9           32.3  25.4
800mm        20.0  18.9           20.8  18.4

You can see I've gone a little wider, and generally thinner. I'm a tad thicker at the centre line but there is a bit of an odd dip/twist there. From the figures, I'd think the MR bow was higher draw weight, but of course we don't know what the draw length was (it is one of the shorter bows).
Out of interest I'll play with some figures.
Stiffness is proportional to cube of thickness, so if we take the thickness of the MR bow cubed (at say 400 mm) and divide that by the the thickness of my bow cubed (at 400mm) we should a figure to multiply the draw weight by.

We get 1.19 (to 2 decimal places).
If I multiply the 100# draw weight by this we get 119#
Ah but The MR bow is slightly narrower by a factor of  0.93 which would take the draw weight back down to about 111#
Of course this is just a bit of fun and proves nothing, other than showing the bow is somewhere in the right area as an approximation.

The lower pics show a small filled knot which has a nice blush around it and has almost been rasped off the edge of the bow, on the right edge of that pic you can see the last remnants of that nasty knot revealed when I first sawed the log. The right pic shows the little area where the central pith is still exposed, You can also see the centre of the log as a dot just right of centre...
How come? The log was much bigger than that?
Ah! The centre isn't always in the middle! I can only assume that the knotty side of the log grew faster and had wider rings, leaving the central pith closer to the clean side of the log.

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