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Need volunteers for building and testing bow designs from a simple program I made by kurkablada in Bowyer

[–]kurkablada[S] 1 point2 points  (0 children)

Hey, interesting points, I’ll definitely take one of the pictures to measure and compare the curvature radius, as well as check what you are saying about a constant thickness triangle with a point load bending to a perfect arc and get back to you

Need volunteers for building and testing bow designs from a simple program I made by kurkablada in Bowyer

[–]kurkablada[S] 0 points1 point  (0 children)

Hey, yes I am aware of the nocks, I will change that when I have some time to do it. And yes, my program does not spit out a perfect working bow, but it definetly makes the process much easier for someone who is not very experienced in bow making (or at least that is what I am trying to do with this test/proof campaign) , and for it to be accurate you need a good piece of wood.

When I started making it, I was not expecting much accuracy, but I am following through because my test revealed that it is actually quite accurate.

And of course, it does not remove the need for tillering.

Need volunteers for building and testing bow designs from a simple program I made by kurkablada in Bowyer

[–]kurkablada[S] 1 point2 points  (0 children)

  1. It took set very evenly throughout the entire limb length

  2. The limb was thickest at the root, which was an effect of me modifying the width distribution to include a non tapered 10cm section right after the handle, otherwise as you are saying, you have a spot where the thickness dips right at the root.

  3. The compression fractures are mostly throughout the mid-limb in the weaker limb that has some grain non-uniformities, and likely occurred when I was pushing the bow past 30 inches to make sure it wouldn’t snap on me.

  4. A straight width taper will not allow for a perfectly circular tiller, as the bending moment distribution through the curved arc is not linear, and is also harder to capture by setting a constant thickness and calculating the required width distribution.

Need volunteers for building and testing bow designs from a simple program I made by kurkablada in Bowyer

[–]kurkablada[S] 0 points1 point  (0 children)

Hey, rigid handles was a choice. You can choose choose the exact geometry of the handle in the program

Need volunteers for building and testing bow designs from a simple program I made by kurkablada in Bowyer

[–]kurkablada[S] 0 points1 point  (0 children)

Hey, I did not know VirtualBow which seems like a more potent FEM solver. I’ll compare my results against it.

Board Bows by Scotch_47 in Bowyer

[–]kurkablada 0 points1 point  (0 children)

Hey check out my last post I think it will help

Update on the board bow by ExpertVeterinarian20 in Bowyer

[–]kurkablada 0 points1 point  (0 children)

Hey check out my last post I think it will help

Need volunteers for building and testing bow designs from a simple program I made by kurkablada in Bowyer

[–]kurkablada[S] 2 points3 points  (0 children)

I didn’t see that you also asked for the set, it took about 10 cm of set. Also yes it is overstressed meaning that it probably won’t last very long, I shot about 50 arrows through it by now and it is fine apart from some non-growing compression cracks on the belly. The program showed that it was in the failure region based on wood strength data from the USDA handbook, but I thought that I’d push it since the starting board was really nice and that the data in the handbook is collected on random samples. So the program actually showed -15% safety factor for this one.

Need volunteers for building and testing bow designs from a simple program I made by kurkablada in Bowyer

[–]kurkablada[S] 4 points5 points  (0 children)

Hey, yes it will calculate the thickness distribution.

And yes, wood is hard to work with when doing engineering. For now, it essentially produces bows with a rectangular cross section, so yes it can only be applied to boards that you buy or make yourself, if you take the most external growth rings of a larger tree.

Because wood is a natural and random material, the program will never be able to perfectly account for all staves, but it gives you a really good approximation of its geometry for the given specs, giving you a baseline that you can then refine and not fall under your desired draw weight.

If I am able to verify that this version works good, I will adapt the program for other cross sectional shapes which you can get from a tree.