Distal End Fails

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ganesh
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Distal End Fails

Post by ganesh » February 16th, 2019, 4:35 pm

So my partner and I made 2 boomilevers that weighed 27 grams and 21 grams. After testing them, they both held only 7 kilograms and had the same base structure design. The thing is, they both broke in exactly the same place, THE DISTAL END. This was a major problem for us but we soon fixed it by using a different type of glue and supports.

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Re: Distal End Fails

Post by samhua1 » February 16th, 2019, 4:51 pm

Also, the base needs fixing

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Re: Distal End Fails

Post by MadCow2357 » February 16th, 2019, 7:02 pm

Sounds like you don't have enough surface area for the glue. Also, you need to make sure that you are using Gorilla Glue.
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Re: Distal End Fails

Post by bobo » February 19th, 2019, 8:56 pm

It will be helpful if you describe more clearly the failure. Did the wood shear off from the glued surface? Did it break a distance from the joint? What kind of wood are you using? What are the dimensions?

There are many many ways to make a good distal joint. You can see examples in the wiki picture gallery. This is just a starting point. In general, you need to have good enough surface area for the glue. You can start with 1/8"x1/16" wide brasswood stick for the tension chords. Glue the 1/8" wide face to the joint. Then, put two pieces of 1/8" wide balsa wood adjacent to that, one on each side. Apply glue to the edges where they contact the brasswood stick. Finally, put a 1/16" think piece of balsa on top to cover the whole joint. This vastly increases the strength because the brasswood stick is glued on both sides. Apply gorilla glue sparingly for this because it expands. Use a clip to gently apply pressure on the joint overnight.

Once you have a good joint, try to reduce the weight of the boomilever. The lower the better, but under 15 g should be easily achievable if you pay attention to the size and weight of the wood you are using.

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Re: Distal End Fails

Post by ganesh » February 23rd, 2019, 5:06 am

Thanks for all of your support. Most of the breaks were shaved clean off and he switched to thick CA glue. It worked perfectly.

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