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The base is whatever works. Some people didn't use that particular method and some people did. I would think, though, that an upside-down U would be sort of difficult to be efficient because you would need to bend the balsa 180 degrees and also it might be too weak (just my opinion). The other option sounds feasible, but of course we won't know until testing. There is no hex nut/washer that goes over the base, and you are not allowed to modify the J-hook on the wall. Sorry, don't know about tubes (planning to try it out later perhaps.

On a side note, how are all of your guys' scores/boomilevers doing?

I used a 5/8" dowel. It works really well, and may be a bit heavy, but is very very reliable. I like it because since it is completely symmetrical as a circle, no sanding is needed until the very end.

I expect my scores iA to be around 900 hopefully. My past score was around 700, but probably could have gone more...

You might check and see if specialzed balsa has any more 5/8" balsa dowels. They had some last year (it's not stocked but made on request) and they had a spare they sold to me, not sure if there were any more. I use it for a bad and it's like well under half a gram.

Did you do any extra preparations to the dowel like laminating or anything? I simply cut the hardwood dowel and use it as it is..

Yup, I just cut it and use that.

Hello
This is my 1st year at science olympiad (div B)
One question: Is anyone using more than one of the J hooks for holding the boom? Any ideas on how it can be used?
Thanks

I've never used more than one attachment. It's not really needed, and using them adds weight to the boom that isn't necessary.

Oh, and welcome to Science Olympiad

Is anyone having any success with mounting blocks less than 1 gram? Trying to determine if the envelope can be pushed below that or if that is about as low as it goes. I'm not asking for your secrets mind you, just if it's possible.

Yeah, I mentioed it a few posts up. Last year my lightest base was .4g, I think this year you can even go lighter than that.

iwonder wrote:Yeah, I mentioed it a few posts up. Last year my lightest base was .4g, I think this year you can even go lighter than that.

WOW! no clue how to get it down that light... assuming it carried a respectable load (I'm sure it can be done, if you don't need it to carry the bucket LOL) We put a science seminar on last Saturday for the 3rd through 6th graders to attend, to try to develop their interest in science... We probably had 50+ experiments for them to be part of... One of which was testing 8 pre-built booms by our SO boom builders... All booms were built from a consistent design... Only variances were compression beam densities, and styles of mounting blocks... Really wide range of results, mostly due to various stages of expertise and skill in the construction, as opposed to designs... We have a few that are going into their 3rd year of building, and a few that have just started... In any case, the 8 booms ranged in scores from a low of 350 or so, to over 1200... All were loaded with a sand dispenser, as opposed to a scoop, controlled by selected members of the audience... I think I spotted several Future Boom builders for the next several years!