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Re: Towers B/C
Posted: January 9th, 2017, 5:37 am
by dholdgreve
embokim wrote:If I remember correctly many of last year's bridges were comprised of four main uber thick and strong compression members with very thin tension members on the bottom, do you think teams are doing a similar type thing this year? With three very strong members with very thin cross braces running along side of them? Also would you know what kind of wood they used for those compression members?
Also, I was wondering what density of balsa you would use for a compression member, I am confused, as to what density one should buy, I am looking for a really strong compression member as mentioned above. Also how much stronger do you think a dowel would be rather than sticks? Has anyone tries this before?
Thank you for enduring through this long post.
You need to think more "globally" here... Really strong compression members won't get you very far without a good bracing system to support them. They may not need as much bracing, but they will need some. FWIW, I'll take a medium strength compression member with additional bracing over super strong compression members with minimal bracing anytime...
Re: Towers B/C
Posted: January 11th, 2017, 4:00 pm
by Random Human
I use 1/8*1/16 for some braces and 1/16*1/16 for some braces but I've changed to a new tower design with 1/16*1/16 that performed better than my 1/8*1/16. All the 1/8*1/16 will bassically go to waste and as I am low on 1/16*1/16 is it a bad idea to litterally strip off 1/16*1/16 from the 1/8*1/16 sticks? Also, what stripper would be suitable for these kind of strips?
Reusing posts, will stripping 1/16*1/16 from a 1/8*1/16 stick work?
Re: Towers B/C
Posted: January 12th, 2017, 6:10 am
by Balsa Man
Random Human wrote:I use 1/8*1/16 for some braces and 1/16*1/16 for some braces but I've changed to a new tower design with 1/16*1/16 that performed better than my 1/8*1/16. All the 1/8*1/16 will bassically go to waste and as I am low on 1/16*1/16 is it a bad idea to litterally strip off 1/16*1/16 from the 1/8*1/16 sticks? Also, what stripper would be suitable for these kind of strips?
Reusing posts, will stripping 1/16*1/16 from a 1/8*1/16 stick work?
Brace pieces are short enough that with care, you can do it with a razor blade and a metal straightedge/ruler. It'll be a bit tricky; probably want to put 8-10 down tightly together on a piece of wide masking tape (to support the straightedge/ruler)
Re: Towers B/C
Posted: January 12th, 2017, 4:10 pm
by Random Human
Balsa Man wrote:Random Human wrote:I use 1/8*1/16 for some braces and 1/16*1/16 for some braces but I've changed to a new tower design with 1/16*1/16 that performed better than my 1/8*1/16. All the 1/8*1/16 will bassically go to waste and as I am low on 1/16*1/16 is it a bad idea to litterally strip off 1/16*1/16 from the 1/8*1/16 sticks? Also, what stripper would be suitable for these kind of strips?
Reusing posts, will stripping 1/16*1/16 from a 1/8*1/16 stick work?
Brace pieces are short enough that with care, you can do it with a razor blade and a metal straightedge/ruler. It'll be a bit tricky; probably want to put 8-10 down tightly together on a piece of wide masking tape (to support the straightedge/ruler)
im using master airscrew balsa stripper, and gonna use that to strip 1/16*1/16 stick FROM 1/8*1/16 stick, it works right?
Re: Towers B/C
Posted: January 12th, 2017, 4:53 pm
by baker
Random Human wrote:Balsa Man wrote:Random Human wrote:I use 1/8*1/16 for some braces and 1/16*1/16 for some braces but I've changed to a new tower design with 1/16*1/16 that performed better than my 1/8*1/16. All the 1/8*1/16 will bassically go to waste and as I am low on 1/16*1/16 is it a bad idea to litterally strip off 1/16*1/16 from the 1/8*1/16 sticks? Also, what stripper would be suitable for these kind of strips?
Reusing posts, will stripping 1/16*1/16 from a 1/8*1/16 stick work?
Brace pieces are short enough that with care, you can do it with a razor blade and a metal straightedge/ruler. It'll be a bit tricky; probably want to put 8-10 down tightly together on a piece of wide masking tape (to support the straightedge/ruler)
im using master airscrew balsa stripper, and gonna use that to strip 1/16*1/16 stick FROM 1/8*1/16 stick, it works right?
It will be a challenge. As you push or pull the sticks thru the stripper they may bend and break. That stripper works best with sheet material, where you can hold the sheet for stability. But it may work if careful. I find decent sheet balsa at AC Moores or Michaels craft stores. Bring a scale with you.
http://www.nclra.org/Programs/BalsaDensity.php
Re: Towers B/C
Posted: January 12th, 2017, 5:54 pm
by HandsFreeCookieDunk
In discussions about bracing, almost all of the methods I’ve seen involve placing a piece of balsa between the two legs, connected by butt joints. Does anyone has any tips on how to cut the stick so that so that it fits perfectly? I’ve had some difficulty creating a brace that is not only the perfect length, but also has the perfect angles on the end to be flush with the legs. I apologize if this has come up before; I’ve been following this thread since the beginning of the year and I just don’t remember it ever being discussed.
Re: Towers B/C
Posted: January 12th, 2017, 6:42 pm
by Unome
HandsFreeCookieDunk wrote:In discussions about bracing, almost all of the methods I’ve seen involve placing a piece of balsa between the two legs, connected by butt joints.
Really? I've never seen a tower made with anything other than lap joints attached on the outside.
Re: Towers B/C
Posted: January 12th, 2017, 7:41 pm
by bernard
Unome wrote:HandsFreeCookieDunk wrote:In discussions about bracing, almost all of the methods I’ve seen involve placing a piece of balsa between the two legs, connected by butt joints.
Really? I've never seen a tower made with anything other than lap joints attached on the outside.
HandsFreeCookieDunk, such bracing, if I'm understanding you correctly, would be under tension for which butt joints are very weak. Butt joints are generally the weakest, and here they do no better.
Angled connections are best done with sharp blades and fine sandpaper. Cut only wood with your blades; any contact with glue may dull or chip your blades.
Re: Towers B/C
Posted: January 13th, 2017, 4:44 am
by HandsFreeCookieDunk
bernard wrote:Unome wrote:HandsFreeCookieDunk wrote:In discussions about bracing, almost all of the methods I’ve seen involve placing a piece of balsa between the two legs, connected by butt joints.
Really? I've never seen a tower made with anything other than lap joints attached on the outside.
HandsFreeCookieDunk, such bracing, if I'm understanding you correctly, would be under tension for which butt joints are very weak. Butt joints are generally the weakest, and here they do no better.
Angled connections are best done with sharp blades and fine sandpaper. Cut only wood with your blades; any contact with glue may dull or chip your blades.
Hmm... I was just rereading BalsaMan's document about bracing and the "Ladders and Xs" design, where the diagonal members are under tension and the horizontal members undergo compression in order to brace against buckling on all four sides of each leg. I was also thinking of just going the lap joint route since it requires so much less precision, but I figured the butt joint would be better for preventing buckling toward another leg.
Re: Towers B/C
Posted: January 13th, 2017, 5:48 pm
by TeamPlayer25
Hey everyone,
I am competing for Towers this SO season. My last structure had an efficiency of 1583. However, I am looking for a design that can break 2200. Can anyone suggest a good design?