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Hi tech redneck flight bow.
Selfbowman:
Willie I can print 1” full scale drawings at my architects office. Bend profile and force draw. It would be nice to have it all on the same page unstrung , strung, and bend profile every 4” of draw. Every other bend profile starts about ten inches from fade as to not blurry up the first ten inches. coming out or the fades.
willie:
--- Quote from: mmattockx on November 23, 2024, 01:22:51 pm ---
--- Quote from: willie on November 22, 2024, 03:16:37 pm ---Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness.
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Depending on the thickness you want, a table saw may not be accurate enough. I use a thickness sander to get consistent thickness on my bend test samples and a decent surface finish to prevent lifting splinters during the test.
Mark
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After measuring some rippings, I see some deviations that would warrant a thickness sander, especially if trying to get a good sample from a stave.
I suppose if you had some sizable stock that didnt make a stave from the same tree, and you had enough to work with squaring, resquaring and re-ripping with decent featherboards it might possible.
what bend test do you use and how big a sample?
mmattockx:
--- Quote from: willie on November 25, 2024, 07:29:29 pm ---what bend test do you use and how big a sample?
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I used a simple cantilever bend test where I measured the deflection of the sample slat due to a known weight at a known bending length. The two bows I did this way were made from boards, so I cut one test piece off the board before I did anything else with it. My primary concern was measuring the elastic modulus (Young's modulus) so I could calculate the dimensions to achieve a desired draw weight. I was less concerned with finding the strain where set started, but I did do some of that for the second bow I made from red oak laminations just to get an idea of the strain limit. Because of the imprecise way wood takes set this is pretty approximate and mostly gives you a kind of fuzzy edged range of where set starts to be noticeable.
Mark
willie:
--- Quote from: mmattockx on November 25, 2024, 11:53:16 pm --- I did do some of that for the second bow I made from red oak laminations just to get an idea of the strain limit. Because of the imprecise way wood takes set this is pretty approximate and mostly gives you a kind of fuzzy edged range of where set sttarts to be noticeable.
Mark
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I wonder if the imprecision is "in the wood" or a better test method could help?
Maybe something that bends a sample to a true arc of a circle can be less fuzzy.
I might do some experimenting with test methods here that Arvin could duplicate at his place. I think he would like to design a bow that just begins to take set at full draw if I understand his needs correctly.
mmattockx:
--- Quote from: willie on November 27, 2024, 04:03:04 pm ---I wonder if the imprecision is "in the wood" or a better test method could help?
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I expect it is some of both. The biggest problem I had was determining when set had started. I'd put a load on the sample, measure how far it bent and then take the load off to see if it returned to zero or not. Because wood has some hysteresis there is always a little bit of what could be set, depending on how long you allow for it to return to the unloaded position. I would repeat this with increasing load until I clearly had set, then try to determine where set really started by going back through the test results.
Mark
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