One bow, two draw force curves

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One bow, two draw force curves

Tuomo.e
Registered User
Tuomo.e
Registered User
Joined: January 26th, 2006, 3:02 pm

July 10th, 2018, 1:35 pm #1

Here is an example of one bow and two draw force curves. The bow in this example is a lot used bamboo-maple-ipe-laminate, about 40#@28". Before draw force measurements, I took about twenty full draw. My scale has two measurement option - a peak value and stabilized value. Depending on draw length, it took about 1–5 seconds to stabilize. Please, see the result, in the table and graph.

There is one oddity - wood bow energy storage (potential energy) is too good. If compared to straight draw force "curve" (which value can be set to 100 %), then using maximum values, this bow stores 109,6 % of energy compared to straight line. But, if I use stabilized value, it stores 111,5 %!. As you can see from the graph, there is small hump in the beginning of draw force curve but with stabilized value, the maximum value is lower than peak value. So, it seems that wood bow stores a lot of energy but it is not so true because this phenomenon is caused by hysteresis.

I will make the same measurements and test with a lot used white wood selfbow (English oak, Quercus robur) and I think that the difference will be larger.

blue line - max. values
red line - stab. values
draw force curves 2.png
draw force table.png
draw force curves 2.png draw force table.png
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