Boomilever B/C

[MadCow2357]

Just curious to see what's possible, how much do y'all's tension pieces weigh? (the tension pieces + the base) My design is about 2.7 grams but I'm trying to see if I can decrease that a bit...

Xiangyu

I've been fine with much less (around 1.5 g), and I'm purposely overbuilding that part

Hmmm good to know. I've been using 1/8 by 1/16 for my tensions, do you think I'll be able to go lower? (About how low? I'm ordering new bass tensions soon)

Xiangyu

You should be safe with 1/16 by 3/32 or something with the same X sectional area

[dankdecidueye]

How many trusses are recommended for full load held? I don't want to over/under build on how many I'm making

[dholdgreve]

How many trusses are recommended for full load held? I don't want to over/under build on how many I'm making

You cant design in a vacuum. It depends on the compression beams. The smaller/ lighter they are, the more support is required.

[scioly2345]

Hi Boomilever people,

So I need some advice on attaching verticals. I don’t know whether to use bass or balsa, or how to get them on properly because of the annoying angles of the compression and tension pieces. My breaks this season have mostly been compression explosions because they bend upwards. Any tips on how to do this? I just want to do one vertical on each side of the boomi so I can shrink the size of my compression to save mass. So far I’ve just made the main supports of my compression so tall and thick to the point where verticals aren’t needed, but with that comes the fact that the compression is so. heavy. Which is not cool efficiency wise.
My next steps to make my boomi lighter is 1. Learn how to properly do verticals so I can shrink my compression and 2. Change my bass size from 1/8x1/16 to either 1/8x1/32 or 3/16x1/32 for tension. I have experimented taking off lamination at either the hook area (I use a dowel) or the distal end, but that very experimenting told me that that excessive lamination, although mass consuming, is not optional, so I’m not going to mess around with lamination. I’d rather have a compression break than a lamination/dowel break for sure.

My peak efficiency this year was a 1.7k but the highest I’ve gotten at competition is 1.5k, because I’ve been too scared to go to light because I don’t want to lose the bonus. UPenn efficiencies were scary good. So I need something to save lots of mass for NYS. My guess is around 1.3k for top ten, but I have NO idea of the competitiveness of the top 5.

A few things to consider here. Learning how to properly do verticals that are light is a huge challenge but is an absolute must if you want a light design that can hold the full load. For your bass tension pieces- do they hold full load? If so, make them lighter. Find the lightest you can use that can still hold full weight. I would move away from a dowel at the connection and experiment with some other designs. We use bass in tension and our verticals are all balsa.

I understand going "conservative" at competition but (especially this year) no risk, less reward. Our team"flirts" with disaster in boomi. We know it will break around 15kg and usually it holds, and sometimes it doesn't (looking at you, MIT). UPenn was relatively competitive with just a handful of scores at, or above, 2k but I am sure there will be more above 2k at the NY state championship.

Weigh the pieces of your boomi. Which are the heaviest? Do they need to be that heavy? Only way to know is to keep building, change one thing, and then record results. If those pieces hold up easily, make them lighter.

My tension is QUITE heavy, like everything with lamination can come out to 4 grams.
Compression I don’t wanna really mess with.
But with the verticals, how do you deal with attaching verticals when the angles the tension and compression are at are so annoyingly hard to deal with?

[scandium21]

Hey guys, I built a boomilever that I was hoping would hold 12 to 15 kg, but it failed at 8kg in tension. I was using 3/32 basswood tension sticks, which I used last season to good results. The break was clean in tension close to the hook connection. Why did they break so early? Could it be that there was too much of an inward curve of the sticks?

[Lorant]

Hey guys, I built a boomilever that I was hoping would hold 12 to 15 kg, but it failed at 8kg in tension. I was using 3/32 basswood tension sticks, which I used last season to good results. The break was clean in tension close to the hook connection. Why did they break so early? Could it be that there was too much of an inward curve of the sticks?

Perhaps they were not glued into the chip at the correct angle.

[scioly2345]

Does anyone else’s distal end lower when they get to full load? Mine will go down at least a centimeter but still hold full load. Is this because of the stretch of the tension pieces?

[MadCow2357]

Does anyone else’s distal end lower when they get to full load? Mine will go down at least a centimeter but still hold full load. Is this because of the stretch of the tension pieces?

It could be the base of your boom compressing, which is rather likely if you are using balsa.

[jinhusong]

Does anyone else’s distal end lower when they get to full load? Mine will go down at least a centimeter but still hold full load. Is this because of the stretch of the tension pieces?

It could be the base of your boom compressing, which is rather likely if you are using balsa.

We use basswood base and pre-dented with 40kg pulling. The distal still went lower more than one cm before the boomi broke at 9kg.
Mostly is because the stretch of the tension.

[scioly2345]

Does anyone else’s distal end lower when they get to full load? Mine will go down at least a centimeter but still hold full load. Is this because of the stretch of the tension pieces?

It could be the base of your boom compressing, which is rather likely if you are using balsa.

We use basswood base and pre-dented with 40kg pulling. The distal still went lower more than one cm before the boomi broke at 9kg.
Mostly is because the stretch of the tension.

Wdym by “40kg pulling”?