Designs

[thsom]

Thankyou. That brings me to my next question. What density balsa wood are you guys using or do you recommend. I am using 1/18th by 1/8th balsa for the legs and 1/16th by 1/16th for cross pieces. Also, where do you order them

[Balsa Man]

Thankyou. That brings me to my next question. What density balsa wood are you guys using or do you recommend. I am using 1/18th by 1/8th balsa for the legs and 1/16th by 1/16th for cross pieces. Also, where do you order them

In reverse order- we get out wood from Specialized Balsa (in Loveland, Colorado); they have a website, do mail order, and sell weight-graded balsa sticks (and 1/64th sheet). They have bass, too, but not weight graded. Living close by, we're fortunate to be able to pick our sticks.

As I've posted before, we use 3/32nds bass for legs, 3/32nds balsa for ladders, and 1/16th x 1/64th for Xs. With 2 years of bridges, and now into second year on towers, we have a lot of real test data on this combination- for legs & ladders, what density at what exposed column length carries what load; for Xs, what density at what width works, for all, what the range of strength at a given density looks like, i.e., what level of safety factor is likely to work. I am not saying this is the best/ultimate combo. Sticking with it, and developing data means design becomes a pretty straightforward engineering excercise, as opposed to guesswork/experimentation. For instance, on bridges, both years, we built one regional bridge, and one state bridge; they all won.

Specific densities? I'm going to have to say no comment till late in the season...

[thsom]

Thankyou. That brings me to my next question. What density balsa wood are you guys using or do you recommend. I am using 1/18th by 1/8th balsa for the legs and 1/16th by 1/16th for cross pieces. Also, where do you order them

In reverse order- we get out wood from Specialized Balsa (in Loveland, Colorado); they have a website, do mail order, and sell weight-graded balsa sticks (and 1/64th sheet). They have bass, too, but not weight graded. Living close by, we're fortunate to be able to pick our sticks.

As I've posted before, we use 3/32nds bass for legs, 3/32nds balsa for ladders, and 1/16th x 1/64th for Xs. With 2 years of bridges, and now into second year on towers, we have a lot of real test data on this combination- for legs & ladders, what density at what exposed column length carries what load; for Xs, what density at what width works, for all, what the range of strength at a given density looks like, i.e., what level of safety factor is likely to work. I am not saying this is the best/ultimate combo. Sticking with it, and developing data means design becomes a pretty straightforward engineering excercise, as opposed to guesswork/experimentation. For instance, on bridges, both years, we built one regional bridge, and one state bridge; they all won.

Specific densities? I'm going to have to say no comment till late in the season...

I respect that, thanks!

[mrsteven]

As I've posted before, we use 3/32nds bass for legs, 3/32nds balsa for ladders, and 1/16th x 1/64th for Xs.
Specific densities? I'm going to have to say no comment till late in the season...

for the 1/16th X 1/64th for x's which way do you orient the 1/16 X 1/64th on the tower?

[Balsa Man]

As I've posted before, we use 3/32nds bass for legs, 3/32nds balsa for ladders, and 1/16th x 1/64th for Xs.
Specific densities? I'm going to have to say no comment till late in the season...

for the 1/16th X 1/64th for x's which way do you orient the 1/16 X 1/64th on the tower?

They run diagonally between ladders-; one from lower left to upper right, one from lower right to upper left, forming an "X". If you take a look in the Image Gallery- bridges 2009- along the top of the bridge- between the two upper "rails"/compression members. Imagine those two members are tower legs; glued to the legs - flat - the 1/16th dimension parallel to the legs

[Faustina]

The tensile strength of "high density" balsa is pretty amazing. A little real test data - 1/16th width, from a 3"x36" 1/64th sheet at 8.6grams, almost 2.1kg. The range of (3"x36") sheet weight that "should work" at 1/16th is from the low 7s up.

When you say that the range of sheet weight that should work at 1/16th is from the low 7s up, are you referring to a 1/64th sheet cut into 1/16th pieces, or to a 1/16th sheet? I initially interpreted it to be the latter, but now that I think about it, that wouldn't make much sense because there wouldn't seem to be an advantage using 1/64th.

[mrsteven]

As I've posted before, we use 3/32nds bass for legs, 3/32nds balsa for ladders, and 1/16th x 1/64th for Xs.
Specific densities? I'm going to have to say no comment till late in the season...

for the 1/16th X 1/64th for x's which way do you orient the 1/16 X 1/64th on the tower?

They run diagonally between ladders-; one from lower left to upper right, one from lower right to upper left, forming an "X". If you take a look in the Image Gallery- bridges 2009- along the top of the bridge- between the two upper "rails"/compression members. Imagine those two members are tower legs; glued to the legs - flat - the 1/16th dimension parallel to the legs

Oh im sorry! I meant how are the placed in terms of the rectangular nature of the stick? Is the 1/64th side facing you or the 1/16th facing you when looking directly at one side?

[lucwilder42]

Are you asking if he's glueing on the 1/64th side?

[mrsteven]

well im asking when looking directly at one side of the tower so you clearly see an X, if you see the 1/64th or 1/16 facing you.
so which side is being shown, the thicker or thinner

[lucwilder42]

well im asking when looking directly at one side of the tower so you clearly see an X, if you see the 1/64th or 1/16 facing you.
so which side is being shown, the thicker or thinner

Ive used 1/64th and you pretty much always have the 1/16th side up so you have a better gluing surface.