Scioly.org

I (and many other people on here) have been using 3/32 square basswood for the tension members. Though none of my boomilevers have held max load before (my highest was a little more than 8kg), I have never had a failure at the tension members.

I use 1/16 square bass for tension it has held more than full hold but i think that the connection to the base and distal ends are more important than the size of the tension pieces.

The 1/16 square basswood is more than enough. Each just need to hole 20kg. We pulled with luggage sale, it can hold more than 40 kg, single.

Our boomilever holds 12kg in invitation. The distal end twisted inward caused it to break. The tension member held OK.

This is C division.

Jinhu

We had success with 1/16 x 3/32 Bass tension members, holding full load.

How would you slot your tension members through the base? How would you put holes through the base? And what size base are you using for this (as I can imagine my 1/2 by 3/32 basswood is too thin for this method. Also, how do you increase surface area with this method?

Anonymous15 wrote:How would you slot your tension members through the base? How would you put holes through the base? And what size base are you using for this (as I can imagine my 1/2 by 3/32 basswood is too thin for this method. Also, how do you increase surface area with this method?

We use 1/4X1/2 basswood block, so, you can slot. Drill hole or groove on the side then sandwich.

Someone else: 1/2 X 3/32 basswood just glue it between the tension members, then sandwich them with sheet. I forgot the thickness, guess 1/16 basswood sheet.

Jinhu

jinhusong wrote:

Anonymous15 wrote:How would you slot your tension members through the base? How would you put holes through the base? And what size base are you using for this (as I can imagine my 1/2 by 3/32 basswood is too thin for this method. Also, how do you increase surface area with this method?

We use 1/4X1/2 basswood block, so, you can slot. Drill hole or groove on the side then sandwich.

Someone else: 1/2 X 3/32 basswood just glue it between the tension members, then sandwich them with sheet. I forgot the thickness, guess 1/16 basswood sheet.

Jinhu

yea i glue strips cut from a sheet of basswood on top of and underneath the tension members with superglue or gorilla glue.

Anonymous15 wrote:How would you slot your tension members through the base? How would you put holes through the base? And what size base are you using for this (as I can imagine my 1/2 by 3/32 basswood is too thin for this method. Also, how do you increase surface area with this method?

Thanks for the replies! I'll probably just sandwich my tension members with a bass stick/sheet.

Also, I just tested another boomilever. I have pictures attached.

https://www.dropbox.com/s/jck3o0ez1jho5 ... 6.JPG?dl=0
https://www.dropbox.com/s/roy9mi4zgzlb4 ... 5.JPG?dl=0
https://www.dropbox.com/s/77u37dp66ts98 ... 4.JPG?dl=0

There were two main failure points: one at the base (where that crater was) and one at the compression member, where one compression member split right in half. I understand the base failure-I attached some light-density balsa last minute to correct for some slight misalignment (which was a bad idea), but the compression failure still has me confused. I used no tension-compression bracing, and my compression members were 1/8 by 1/2 light density balsa. I used rectangular balsa compression to counteract the forces in the tension-compression plane rather than using bracings. Is this where the problem is (is 1/2 too thin?)

Thank you, as always, for your help!

Also, as we were testing, the crater at the base was slowly growing, which caused the boomilever to tip downwards, which probably increased the compression force. The boom broke at around 8kg. Could the downwards tipping have caused the premature compressive failure?