Monday, 18 November 2013

Warbow 130# at 32"

The warbow is near as damn finished. My attempt at getting force draw measurements from the video didn't work. At the speed I was exercising the bow each frame of video shows the  pointer of the scale as a blur.
I could pull it slower or get someone to take readings as I do it. No matter, it was a good idea in theory... don't s'pose I'm going to buy a top of the range video camera just for that.
Here's the video and a still at full draw.
I did a force draw curve by pulling the bow to each 10# of draw and looking at the scale, fortunately it happened to generally correspond to a an exact number of inches and is very linear at about 5# per inch.

For anyone interested, here's the raw data. Decimals of inches were just estimates to the nearest 0.25
10#    9"
20    11"
30    13
40    15
50    17
60    19
70    21
80    23
90    25
100  26.75
110  28.25
120  30
130  31.75
I've reposted the graph with the axes round the conventional way (and labelled)

For future reference I've put the long string back on the bow and measured the weight needed to get it strung. It needed 60# to get the tips back to brace. The 60# immediately disappears and the force draw curve shows zero force at brace height! Ain't physics and geometry wonderful?

video

4 comments:

  1. Well done derek, your videos on correct tiller are a great help to budding bowyers. Tiller looks great considering all the pitfalls you have negotiated on this bow. rgds Adrian

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  2. Cheers, great to know it's helpful :)

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  3. Unless my Mk.! eyeball deceives me, that tiller looks almost perfect! She looks luvverly, cant wait to shoot her in! (Sigh) JayTee :o)))))))))

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  4. You will have to bring her flowers and chocolates and ask her nicely!

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