Primitive Archer
Main Discussion Area => Bows => Topic started by: Eric Garza on November 11, 2019, 02:59:36 pm
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I have a theory I want to explore, but to do it I need data. Specifically, I need data on the force draw curves of wood bows of various sorts. I have data from a few bows that I have made, but that is not enough. I am particularly interested in getting force draw data from longer bows, including straight-stave bows, reflexed bows, and deflex-reflexed bows. Anyone willing to collect data from bows they have lying around and send it my way? Or send along data they already have?
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you might want to try out this: https://www.virtualbow.org/
can simulate force/draw curves on any bow design you can think of building.
takes a lot less time than actually making each bow :-)
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Thanks, but I want data from actual bows, not from a computer simulation. I spent years developing simulation models like the one you linked to, and as a consequence do not trust them much anymore.
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There is some data here
http://www.primitivearcher.com/smf/index.php/topic,5717.0.html
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Thanks! I will search for other force draw curves and hope to find a few more posts like this.
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Like what DETAILS? Pound reading at each inch of draw? Beginning at what draw or pull length? I have 2 self bows I can test/measure.
Hopefully you or the data can confirm, support or modify the oft-quoted dictum that a “well made self-bow should give a minimum bow speed in FPS of (100 + the bow pull weight at the rated draw length)”.
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I am less interested in the speed of the bows than in the shape of the force-draw curve. I am particularly looking at what different side-view profiles do to the inflection point between the initial energy storage and the start of the upwards curve where bows start to 'stack'. I will post results when they are ready.
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I have a bunch of graphs but unfortunately I can't relate them to bow shape any more. Just the graph wouldn't be much use I guess.
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Yeah, if you cannot tell me side-view profile to go along with each graph, that will not be helpful.
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Maybe you could figure out shape based on the data? That would be a good test too.
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I am less interested in the speed of the bows than in the shape of the force-draw curve. I am particularly looking at what different side-view profiles do to the inflection point between the initial energy storage and the start of the upwards curve where bows start to 'stack'. I will post results when they are ready.
That is a defective formula of very little use. It was based on all weight bow shooting at 500 grain Arrow.
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Steve, what formula are you referring to? I am not following you.
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I think he was referring to “a well made self-bow should give a minimum bow speed in FPS of (100 + the bow pull weight at the rated draw length)”.
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The FD curve of every ELB and warbow I've made has been remarkably linear.
https://bowyersdiary.blogspot.com/search?q=FD+curve (https://bowyersdiary.blogspot.com/search?q=FD+curve)
Del
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a fixture I built a while back could just as well be used to plot fd curves. Different limbs could be easily mounted to compare. adjustable for deflex or reflex and riser lengths.
http://www.primitivearcher.com/smf/index.php/topic,62820.0.html
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Eric I did a force draw on some of my reflex bows and strangely enough the force draw imitated the profile of the limb. Don’t know if this is what you are referring too. Out of town but will be home in a few weeks. Arvin