Boomilever for 2013
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Re: Boomilever for 2013
The longer a tube is that is unsupported, the more prone it is to a buckle. Tubes are extremely strong for their weight. Unfortunately, I think that a tube will be subject to the same criteria as apiece of wood, IE: 1/4 x1/4"
You can not say that it is a built up member, because if you build a tube from material that is 1/4 or less, it will fail or you are extremely good or lucky.
You can not say that it is a built up member, because if you build a tube from material that is 1/4 or less, it will fail or you are extremely good or lucky.
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Re: Boomilever for 2013
Kinda confused about your terminology... What do you mean by a built up member? Also, what is a tube built out of 1/4 or less? And what would make it so failure prone? Finally, what criteria would a tube be subject to that's the same as a rectangular section? Unless you mean a .25" Square piece of balsa and a .25" diameter tube, which would exhibit the same properties(or similar properties).
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Re: Boomilever for 2013
Built up member- a piece that is made up of several parts as a box beam or an I beam or a laminated beam.
Rule 2b of the trial event is very specific in that your starting wood an not be larger than 1/4 x 1/4".
If you made a tube out of say 1/16 x 1/4 , it would be nearly impossible to have it round and you would have numerous glue joints to fail. It would add a lot of weight, negating some of the advantages of a tube.
I recant on the tube diameter-I was not thinking of the 1/4 starting wood when I said that. There is a possibility that they would allow a 1/4 dia tube, but that would have to be built with 1/32 or thinner balsa and I question the strength of it. Remember that a long tube will need to be supported and a thin wall tube is not going to accept most bracing (based on airplane tubes)
I hope that the 2013 rules clarify that. If not, it will be an early question on the rules.
Rule 2b of the trial event is very specific in that your starting wood an not be larger than 1/4 x 1/4".
If you made a tube out of say 1/16 x 1/4 , it would be nearly impossible to have it round and you would have numerous glue joints to fail. It would add a lot of weight, negating some of the advantages of a tube.
I recant on the tube diameter-I was not thinking of the 1/4 starting wood when I said that. There is a possibility that they would allow a 1/4 dia tube, but that would have to be built with 1/32 or thinner balsa and I question the strength of it. Remember that a long tube will need to be supported and a thin wall tube is not going to accept most bracing (based on airplane tubes)
I hope that the 2013 rules clarify that. If not, it will be an early question on the rules.
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Re: Boomilever for 2013
It's been brought up before, and thoroughly discussed, as to why the .25" square cross section will, in all likelihood, not apply. Also, a few pages back jander14indoor had a very good link to a method that produces very nice round tubes of ~.25" diameter without much glue. The bracing issue has also been discussed, but because the cross-section limit will most likely not apply, it hasn't been a large problem.
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Re: Boomilever for 2013
(If there is a 1/4 inch cross section rule)
For boom all members need to meet the 1/4 inch cross section requirement. I understand the base is excluded from the 1/4 inch cross section limit, but what about gussets? Aia's booms have a distal end connection that looks larger than just 1/4 inch, and I don't see how it is feasible for the critical connections if you are limited to a quarter inch.
For boom all members need to meet the 1/4 inch cross section requirement. I understand the base is excluded from the 1/4 inch cross section limit, but what about gussets? Aia's booms have a distal end connection that looks larger than just 1/4 inch, and I don't see how it is feasible for the critical connections if you are limited to a quarter inch.
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Re: Boomilever for 2013
Actually, I never used wood that was wider than 1/4". If you go to my guide under "Distal End", you'll see a pretty good picture of my gusset. I used 1/4" by 1/16" balsa (if I recall correctly, it's been awhile), laminated over the top of the connection, and sanded down the excess wood. At that point, the wood was definitely just a hair below 1/4" wide. The angle between the compression and the tension is small enough that the 1/4" by 1/16" balsa covered the connection perfectly well.LKN wrote:(If there is a 1/4 inch cross section rule)
For boom all members need to meet the 1/4 inch cross section requirement. I understand the base is excluded from the 1/4 inch cross section limit, but what about gussets? Aia's booms have a distal end connection that looks larger than just 1/4 inch, and I don't see how it is feasible for the critical connections if you are limited to a quarter inch.
Admittedly, the diagram in that section of the guide is not the best-- my paint skills made the lamination look larger and more square than it actually was.
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Aia's Boomilever Guide: http://scioly.org/wiki/index.php/Aia%27 ... ever_Guide
Aia's Boomilever Guide: http://scioly.org/wiki/index.php/Aia%27 ... ever_Guide
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Re: Boomilever for 2013
Ala, Did you use any particular height on the bass triangles that you CA glued to the tension member at the base.
Was this your idea or was it borrowed? I have been looking for a method to "pin" the member to the base. This certainly does that.
Was this your idea or was it borrowed? I have been looking for a method to "pin" the member to the base. This certainly does that.
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Re: Boomilever for 2013
I believe those triangles were cut from 3/32" square bass. I determined how long I wanted the triangle, and then used my exactoknife to cut along the would-be hypotenuse. If you do it correctly, you should end up with two near identical triangles. I usually cut out 8 or so triangles, picked the best four, and moved on from there. I did not ever experiment with a different size for those triangles, so there may be a better height choice out there.retired1 wrote:Ala, Did you use any particular height on the bass triangles that you CA glued to the tension member at the base.
Was this your idea or was it borrowed? I have been looking for a method to "pin" the member to the base. This certainly does that.
This idea is mostly my own. I watched my predecessor in the boomilever event try many different types of bases in 2007. When it was my turn in 2008 to build, I knew which ideas were and weren't working for him. I then redesigned the base, improved it as I went along, and eventually arrived at what you see on my guide.
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Aia's Boomilever Guide: http://scioly.org/wiki/index.php/Aia%27 ... ever_Guide
Aia's Boomilever Guide: http://scioly.org/wiki/index.php/Aia%27 ... ever_Guide
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Re: Boomilever for 2013
is there another way to cut wood into sticks from sheets other than using straight edge + razor blade?
My problem is that I often end up cutting in at an angle.
I want to buy sheets instead of sticks this year since it is cheaper, easier to view the grain, and easier examine the wood density across a sheet of wood than examining a bunch of sticks, but I dont think it's worth it if I cant cut properly.
I'm actually okay with cutting thin balsa(1/16" or 1/32"), but any thicker balsa sheets or any bass sheets, I always mess up.
My problem is that I often end up cutting in at an angle.
I want to buy sheets instead of sticks this year since it is cheaper, easier to view the grain, and easier examine the wood density across a sheet of wood than examining a bunch of sticks, but I dont think it's worth it if I cant cut properly.
I'm actually okay with cutting thin balsa(1/16" or 1/32"), but any thicker balsa sheets or any bass sheets, I always mess up.
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