Elevated Bridge B/C

[Keyreaper]

Absolutely!!! I used 1/16th balsa for lateral bracing... No problem what so ever... It always broke because a very FACTORED member broke because the glue joint did not hold.... I am also starting to use smaller and smaller pieces of balsa as I get more experience with the materials... And I have considered using toothpicks for the truss, or/and lateral bracing.

[andrewwski]

Toothpicks are heavy, when compared to balsa of the same size.

[smartkid222]

light:6-10
med 10-14
hev: 14-19
in lbs per cubic ft.

[dennism_11]

so what are your thoughts on what density to use for the bridge?......heavier and smaller or lighter and bigger?
any info would be appreciated, lighter balsa would give you more glueing area.....

[Pleiades]

light:6-10
med 10-14
hev: 14-19
in lbs per cubic ft.

yeah but like which of those would be used in bridge? like is the heavy balsa meant for something other than structures and therefore should not be used in bridge? or is the light balsa for something like pennyplanes and therefore would be way to light for bridge? so if i told my coach to get 25% 6pcf, 50% 10pcf and 25% 12pcf or do i want some of that heavy balsa? i just dont know what the heavy and light balsa actually is.

[smartkid222]

it depends on your desgin and what the target weight is. Last year i was using light/med. This year i've been using med/hev.
It really depnds on the design and wood size though.

[Pleiades]

oh ok so it's not like the heavy balsa is EXTREMELY heavy. I thought that it was too heavy and meant for something else and using it on just 2 places on your bridge would make your bridge way to heavy. Good to know. Thanks.

[smartkid222]

Extra heavy balsa is 19+
*edit and i belive that extra heavy balsa is a bit too heavy for bridge (but of course it depends on the design) and is probably rare to find.
Heavy balsa can be used if your design permits

[frontlineballer1]

a concept idea i was thinking of would be a parabolic figure where the tension and compression pieces would each be a single piece of 1/16" bass wood. i was thinking of making the compression member 2 pieces lamenated together, but what do you guys think of this?do you think there could be some potential in this type of design? the problem i see is where to put the loading block so it distributes the load nicely.

[andrewwski]

I find trying to make any sort of arch in the wood isn't worth it.