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What is the best adhesive for tension?? I realize many say gorilla glue but I have a gut feeling that epoxy steel may be better.....

thsom wrote:What is the best adhesive for tension?? I realize many say gorilla glue but I have a gut feeling that epoxy steel may be better.....

I personally haven't experimented with multiple types of glues and where to use them, but I think as long as you have a large surface area for gluing (which you can make if you can put your tensions "under" the loading block), you won't need to use anything other than your typical CA glue. Then again, this is my first year in the "balsa building events," so you might want to take my word with a grain of salt...

jander14indoor wrote:
That said, don't sweat it. As I've said on other construction strings. Don't worry over the exact rules. We can only throw in so many variations and still be boomilever. Use any prior year set of rules to practice building over the summer and learn how to do well and WHY you did. Then whatever variation we throw at you in the fall you are miles ahead of everyone who did nothing over the summer.

If you want to get ahead during the summer, I would suggest learning how to build a functional base. You will certainly need that knowledge in any rendition of the boomilever event. And, as Mr. Anderson said, attempting to build ANY boomilevers will be helpful even if the measurements aren't quite the same as the 2013 rules.

For the record, I am working on a short guide that will detail my boomilever experiences from 2008. I will post a link to it when I am finished.

Since this is only my second year doing balsa events... and I like boomilever more than towers(or so it seems...) I've been looking at designs and trying to figure out what I'm going to do come competition season and I've come up with a couple questions I was hoping you all could answer for me...

First... nevermind, I found it

Second, how do people transport a tension booilever that doesn't have any members running between the chords? It seems to me like the base would cause the tension members to crack very easily.

Third, in the past there has been talk of pre-tensioning some of the members... how does this help? It seems like it just stops any small compressive load from causing the thin beams(1/64th seems to be what's used when this happens) to buckle. Or maybe this one of those 'if you have to ask, don't worry about it' questions.

Thanks! and I will be building a few models over the summer to figure out how to build it and what ideas work best... no matter how crazy people think I am for working on SO before the rules are published...

This is my first year trying out for a new science olympiad team but we have to build a boomilever but I am only familiar with towers. any help on how to construct one?

I have to admit this is only from helicopters/towers experience myself... however I hope it should suffice.

First off, the wiki on boomilevers (http://www.scioly.org/wiki/2013) has a ton of info on how to build one, and from previous years, it's very important to have a jig to build off of, and to only use a very small drop of glue on joints... lap joints, etc. The boomilever doesn't seem that much harder, especially for the tower crane discussed in the wiki(which also tells you how to build a base) the compression truss seems to be the most complex structure, and that's just like a tower, without a base. So what I'm thinking of(maybe someone can tell me if it's a good plan or not..) is building a chimney-like structure, making sure it's flat on the end that will touch the wood, and the gluing the tension members on in the middle of where the loading block sits(watch out for a diving board effect on the loaded end). The base seems be self laminated balsa or plywood from a hardware store(though that can be very heavy), just make sure that you get the largest surface area possible in the joint between the base and tension member because the glue will be in a shear mode there, and only use one bolt(if you're not sure what I mean by one, the rules for a trial version are on the soinc website). Hope it helps!

One thing I thought was interesting when I was doing some quick math and playing with design ideas -- with 08 spec, with a max height of 15cm and a distance of 40cm, makes the angle formed almost exactly the same as the angle formed in the top triangle for anyone who made an elevated bridge that looked like a triangle on vertical (or near-vertical) legs... For me at least (since even the most minor the things I learned about bridges are, I think, permanently seared into my brain), this was a way for me to get some intuitions about the forces involved and the densities required for success.

To answer an earlier question, I would have said an epoxy like that was the best way to attach the base (it's what I did when I made a boom way back). Now though, after seeing what could work with bridges (when similar levels of force were involved, depending on the design ideas you're using), I might be inclined to say it's overkill and that regular CA clue would work fine...

By far the hardest part for me to figure out with this event is the interaction of the attachment base and how to sit the loading block at the distal end. The idealized version with a point load and a point connection is pretty straightforward to figure out, but the realities of bolting to a wall and hanging a loading block are quite tricky. Sitting a bridge or tower on a table and having the loading block (usually) just sit at the top is so much simpler!

By the way, the boom I referenced building (I only ever built one, though I'm thinking about buying myself some wood just to play with on my own...) is still up in the image gallery. iwonder, it mimics your thoughts very closely.

Good to see that my ideas aren't crazy...

After adding to my guide bit by bit, I think the first version is ready to be seen by others...

http://scioly.org/wiki/Aia%27s_Boomilever_Guide

My main goal with this was to help people get started on the event. Let me know if I'm missing any major topic areas.

Aia wrote:After adding to my guide bit by bit, I think the first version is ready to be seen by others...

http://scioly.org/wiki/Aia%27s_Boomilever_Guide

My main goal with this was to help people get started on the event. Let me know if I'm missing any major topic areas.

Wow! Your guide is GREAT! I have read the whole thing and learned a TON. Thank you so much.

I don't think you're missing any major topics. However, one small detail I think you missed is the cutting tool (for the "tools" section). Specifically, I'm wondering if cutting basswood requires special tools.