Boomilever B/C

[iwonder]

Yeah, sorry I wasn't clear, you can test wood of similar density and it'll give you a better idea of what will happen. Not that you should be testing the wood that goes on your competition booms.

[iorbiteuropa4776]

Hey guys!

This is the first time I've ever done Boomilever. I've built a few simple ones, all weighing 7-15 grams. I built a compression tube after reading about it here, but it ended up weighing about 17 grams. I went to the local hobby store and selected the lightest wood I could find, but it still ended up being way too heavy to beat any of my previous scores (usually around 800-1000 with a 9 gram boomilever).

I was wondering how good scores compression tubes actually get, and what some of the top scores would be. I've heard about some teams getting the mass of the compression tube down to under 7.5 grams, but I'm struggling to understand how this is even possible. Mine weighs a lot more, and using it wouldn't increase my best score, even if it held all 15 kg.

[nxtscholar]

Hey guys!

This is the first time I've ever done Boomilever. I've built a few simple ones, all weighing 7-15 grams. I built a compression tube after reading about it here, but it ended up weighing about 17 grams. I went to the local hobby store and selected the lightest wood I could find, but it still ended up being way too heavy to beat any of my previous scores (usually around 800-1000 with a 9 gram boomilever).

I was wondering how good scores compression tubes actually get, and what some of the top scores would be. I've heard about some teams getting the mass of the compression tube down to under 7.5 grams, but I'm struggling to understand how this is even possible. Mine weighs a lot more, and using it wouldn't increase my best score, even if it held all 15 kg.

Have you tried using thinner sheets when making your tube? It's quite possible you're using sheets thicker than necessary. Also, I actually dehydrated my booms with a simple method: hairdryer. I found that, especially with tubes (since there's a lot of surface area), you can knock off quite a bit of weight.

[retired1]

This may help some.
for the yoke use 3/32 basswood tension members. for the dowel, use a good 1/4" one that is 7/16" long. very carefully cut slots that are 3/32 wide and deep. If it is sloppy, make another one.
For glue, use Devthane 5. It is a 2 part urethane that is SLOWto set. It is stronger than gorilla glue, wood glue, 2 coat model cement and epoxy. It is less viscous that epoxy, so can get into the grove better. You may have to go online to get this. Devthane 2 is all that is available in the local area. You do not need the applicator tool to use the 50 ml size. The 10 and 25 ml size probably will cost more even if you can find it.
On 6 models at the state tournament on sat, none of the yokes failed. Best score was over 1100 with a 10g model.

[thsom]

Should the tube be more than 1 layer thick?

EDIT: assuming I'm using 1/16 sheet and 7/16" diameter

[iwonder]

7/16" Diameter is rather small from the little I know about tube booms, but, I'd try and avoid going anything thicker than 1/16", since the thicker you go the more you're stretching the outside of the tube and compression the inside surface, which can add internal stress to the wood and weaken it.

[iorbiteuropa4776]

Hey guys. I was wondering what luck anyone has had with the " normal " boom design (with a two dimensional compression and two tension chords) . I have a friend in C division who has gotten pretty good scores with this design (1600-1700), and I was wondering how this compares to the compression tube design. From what I have read on the internet, and this forum, I've got the impression that the tube design was superior, but my friend strongly believes in the simple "normal" design. He says that he has seen many compression tube designs and they have never gotten above 1400. I was wondering what designs people have found to be the best, and what scores people have been getting with the compression tube design. Thanks!

[UQOnyx]

Personally I think that the tube method is overly complicated and though it may have its merits, I would opt for the simple design. If your friend in division C is getting scores of 1600, I would strongly suggest copying the elements of his design. If I am not mistaken, a score of 1700 in division C is a VERY big deal.
(If you're really good friends with him, copy his exact design. No shame in that if you build it by yourself )

[thsom]

7/16" Diameter is rather small from the little I know about tube booms, but, I'd try and avoid going anything thicker than 1/16", since the thicker you go the more you're stretching the outside of the tube and compression the inside surface, which can add internal stress to the wood and weaken it.

So 1 layer is most likely sufficient?

[GeorgeInNePa]

Hey guys. I was wondering what luck anyone has had with the " normal " boom design (with a two dimensional compression and two tension chords) . I have a friend in C division who has gotten pretty good scores with this design (1600-1700), and I was wondering how this compares to the compression tube design. From what I have read on the internet, and this forum, I've got the impression that the tube design was superior, but my friend strongly believes in the simple "normal" design. He says that he has seen many compression tube designs and they have never gotten above 1400. I was wondering what designs people have found to be the best, and what scores people have been getting with the compression tube design. Thanks!

Personally I think that the tube method is overly complicated and though it may have its merits, I would opt for the simple design. If your friend in division C is getting scores of 1600, I would strongly suggest copying the elements of his design. If I am not mistaken, a score of 1700 in division C is a VERY big deal.
(If you're really good friends with him, copy his exact design. No shame in that if you build it by yourself )

The beauty of the tube is that, after "bending the tube", it goes together quickly. Also, there are not many glue joints. We have yet to have a tube fail along the seam.

Our tube failure at Regionals was due to using a very low density sheet.

Our main trouble is with weight. Using a 1/16" thick sheet, it is very hard to get total weight under 10g. 11g to 12g is more the norm. I have seen "traditional" designs under 7g.

We are sticking with the tube, if for no other reason that we have a decent, working design. It may not take 1st or 2nd at States, but it will probably medal.