General Discussion

[Aia]

I would very excited if individuals could post their scores and placement from Nationals, thanks!

[fishman100]

Was anyone else surprised when they announced the tie?

[nejanimb]

Yes, until I heard that they used balances that only measured to 0.1g...

Which is patently absurd for nationals.

Congrats nonetheless to the teams!

[mrsteven]

.1 scale? You got to be kidding me... that's totally silly for even a regional let alone nationals!!

A 3 way tie, is that what I saw? Thats impressive that it could even happen, even with the weak scale a tie is still a bit funny that it happened xD

[LKN]

Yes I thought that was ridiculous, when I put my tower on the scale and saw it only measured to the nearest tenth I shot the look of "come on now, really!?"

And to clarify it was a tie just between Grand Haven and Auburn. I thought it was interesting and definitely took me off guard, but when you think about the design of a competitive division b tower all of them are made so dang similar that two towers could max and easily be within a tenth of a gram of one another.

[mrsteven]

Thats questionable the call to use that scale...

Anyway, watching tonights awards online (we shant be good enough for nationals lol) gave me some fire to start workinh on boom for next year. I was toying with the idea of using a single rolled balsa sheet for the compression section without bracing and using 2 tension cords going to the tube. Issue that keeps coming up is the mounting of the loading block on the tube. Im sure cutting a circle to allow the bolt through would be a way to do it, but afraid that will take out too much structure from the circle and not be able to support the load (im working off of the assumption that the load is 15 kg again). Or to make it work use a larger diameter roll but that becomes ineffective in weight and possible issuable with getting the eye hook through enough to actually hook the chain.

Anyone in the past done boom that has toyed with tubed balsa? Is it a deadend bc too heavy?

[thsom]

Quite honestly, the trick with making a tube for compression is not exactly density or any typical factor, rather the grain of the wood. That can really make or break (no pun intended) the boom.
As for Boom, i have made 5-6 booms in the range of holding all and in the range of being light and holding little. The best efficiency received I don't want to disclose. However I tell you this, it is not hard to make a boom under 15-16 grams and holding all 15 kg, not hard at all. The worst efficiency received was a ~630, the others were in a range of 1000 up.

[mrsteven]

Well how I'm looking at it is its like towers: I want to be in the 10 gram range for boom by the end of the season.
I know the grain is super important, I'm always careful about that but have you tried using a tube for the compression member (s)? Can you use light enough wood where it becomes useful to use that over conventional bracing of members?

[LKN]

Any rough ideas on the boom dimensions/specs? I wasn't around when boom was last used in the competition cycle and I'm interested to know what we should expect for a ball park so maybe I can try a few things this summer too.

From what I recall, SLM's tube tower had a chimney 35 cm Long and about 3cm in diameter. Don't quote that, it is a guess from the picture Posted in last years forum. I believed it weighed in at 9ish grams and was somewhere around 1/32 of an inch thick. Density wise, SLM has total control over what the entire balsa sheet weighs, how uniform the density it is, and probably grain too. I don't have this luxury nearby so I might throw a few bucks to specialized balsa and see if I can custom order a few sheets and see what, if anything, might be feasible. I would think that as long as the wood didn't crack or split by rolling then thinner or lower density wood could be possible options. The other thing to remember are properties of wood and a circle... The smaller the diameter and thickness then greater the weight savings. Add on any skill to tightly and consistently roll a tube small enough to hit that perfect size you want, that an be a nightmare or impossible in itself. Balsa has a point where it can only roll so tight. Depending on how consistent tubes can be in this event, this could be the matter of tenths of grams to whole grams. Any thoughts on this?

I... Have ideas on making the circle connection work. Try some 1/16 x 1/8 at about .75g a 36" stick. Be sure to diagonally cut to nearly match the circle's curvature. Cut out 2 one cm lengths. Find out the place on the tube and mark where the 1/8 height gain from the balsa would barely exceed the total height or the tube where the block is to be loaded. Maybe trying a rubber band or affixing sandpaper to the tube itself (or whatever you jigged the tube on) and sand the piece for supporting the load block. Glue them down, make sure they are a level surface for the block. Have a hole at least 5/16 inch for the rod that goes through the tube and centered between the newly created platform for the testing block. Thoughts?

[mrsteven]

I... Have ideas on making the circle connection work. Try some 1/16 x 1/8 at about .75g a 36" stick. Be sure to diagonally cut to nearly match the circle's curvature. Cut out 2 one cm lengths. Find out the place on the tube and mark where the 1/8 height gain from the balsa would barely exceed the total height or the tube where the block is to be loaded. Maybe trying a rubber band or affixing sandpaper to the tube itself (or whatever you jigged the tube on) and sand the piece for supporting the load block. Glue them down, make sure they are a level surface for the block. Have a hole at least 5/16 inch for the rod that goes through the tube and centered between the newly created platform for the testing block. Thoughts?

I can't say I understand about half of what you had just written. I cannot visualize the:
"Be sure to diagonally cut to nearly match the circle's curvature. Cut out 2 one cm lengths. Find out the place on the tube and mark where the 1/8 height gain from the balsa would barely exceed the total height or the tube where the block is to be loaded. Maybe trying a rubber band or affixing sandpaper to the tube itself (or whatever you jigged the tube on) and sand the piece for supporting the load block"
portion... are you talking about a singular tube or 2 parallel ones?

EDIT: I remember seeing that picture too, but I think he said something about how it wouldn't work... but I dont recall the location of the picture to look