What is the best design a balsa wood bridge?

Question

What is the best possible design for a bridge made from balsa wood? Links to images/ideas greatly appreciated, the bridge cannot have any finishing, however steaming to allow curves is allowed.

If you don't have any idea, suggestions for bridge design and presentation would also be greatly appreciated! Thanks!

Answer 1

I made this type of bridge for a competition and it held about 130 lbs.:

Take a thin piece of balsa wood and put it in a large clamp to hold it in a curve. Spread wood glue over the surface. Use small spring clamps to clamp a second piece of balsa wood to the top. Repeat this a few times. When you are done, tie a piece of fishing line in between the ends of the bridge. Make it go back and forth about 10 times and you're done.

Answer 2

1).You can make a Pratt truss design (Google it)

2).You can make an I beam type span, Two long horizontal plates with a vertical plate glued between them like a lazy H. Several of these side by side may be needed.

3). Since curves are allowed You can take a long flat piece and bend it into an arch by steaming. then Place/glue a long flat board on top of the arch. Support both ends by placing wood between the arch and the top plate.

Good Luck!

Answer 3

by usind a truss system,  a lot of triangles or if you like, z structures

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