Main Discussion Area > Bows
Poisson Effect Versus Neutral Plane - A Theory
tom sawyer:
I now horn can take more compression stress than wood, but is it stiffer?
Justin Snyder:
--- Quote from: tom sawyer on June 14, 2007, 05:36:38 pm ---I suppose you could determine that your NP was right in the center, thats doing it the hard way though.
--- End quote ---
Once again I think you are reading to much into this result. The only thing you can determine is that the weak spot was in the middle. Even if you did assume that the neutral plane was at the break, (which would be a huge assumption) it would not be the center of mass like hypothesized earlier. The horn is significantly heavier than the boo. Justin
bobnewboy:
--- Quote from: J. D. Duff on June 13, 2007, 01:30:13 pm ---
--- Quote from: bobnewboy on June 13, 2007, 11:06:24 am ---ACS-type section of <whisper>fibreglass limbs
//Bob
--- End quote ---
I was thinking about an article I read in which fiberglass bows were forced into a hollow 'C' section. Such bows had far superior performance. I had thought for a which about hollowing-out a 'C' section bow to see what it acted like but it's too much work. Is that what you're talking about?
--- End quote ---
Hi JD,
Yes, it is the curved section limbs that I was thinking about. The ones mentioned have a convex back, and a concave belly, although with a fair sized radius. The overall limb section is C-shaped. The claim is that the limbs are far lower in mass for the same draw weight, and hence they shoot more quickly for the same draw weight.
Considering these limbs with the Poisson effect is what made my brain fade :o
//Bob
tom sawyer:
Justin, I wouldn't assume that a composite would still have its NP in the center of mass. It would only be the case if the horn and the boo had similar MOEs for their respective positions, correcting for thickness. The center of mass only equates to NP for single materials.
SimonUK:
Trying to picture this C shaped bow... If you made it out of wood, you might run the risk of frets on the tips of the C as that's where the compression would be concentrated. However, if the poisson effect flattens out the C as you bend the bow, you could avoid that. I guess it would have to be quite a shallow C shape.
I prefer the sawyer effect bow where the sides are thinner and there is no change in the cross sectional shape as you bend the bow. That way all the energy goes into stretching the back rather than making it skinnier.
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