Designs

[Freyssenet]

Illazar and others,

Have you tried bracing the lower part of the tower with a V-chevron brace? A V-chevron brace is like the seventh type of bracing shown in the first figure in this link:

http://responsivebydesign.com/12/brace- ... -2006-ibc/

Chevron braces are quite effective, and require less material than a X-brace.

[bmbw123]

I recently built the lower portion of the tower, and when I try to press down on the top of it, I can see the bottom x-bracing connecting the legs sag down slightly. My pressure is no where near a large amount of pressure, but I can already picture it buckling very early. Do you guys think this would be attributed to poor/sloppy building technique, a flaw in a design, or something else?

[Freyssenet]

bmbw 123

I think this is normal and is caused by deformation compatibility. As the legs shorten slightly the braces become slack. Once the tower will begin to slightly buckle, some of the braces will go in tension, while others will definitely go slack.

J

[bmbw123]

Ok thanks. It just seems that a little more pressure would certainly cause some piece of wood to break or slip.

And I think that chevron bracing would be very effective, but you would have to use 1/8 in sq. wood pieces, right?

[Freyssenet]

bmbw123: I would use 1/16 x 1/16 braces. To increase the contact area between the braces and the horizontal (also a 1/16 x 1/16 stick), I would glue a 1/16 x 1/16 by 1/2 in. long stick to the horizontal right in the middle where the two braces come in contact with the horizontal.

[lllazar]

What would a chevron v brace look like....im confused with the pic on the page you linked us to. Is it a v opening up in the horizontal direction or is it a v opening up at the bottom of the base?

[Freyssenet]

It is the V-bracing type opening in the middle between the legs...

[lllazar]

Ahh alright i see why that would be more efficient, btw is anyone using 1/32 x 1/16 for bracing? I ordered some balsa in that size and because i felt the chimney bracing was adding a bit more than i would like to the mass of the tower without actually providing any strength...

[Freyssenet]

I think a good strategy for reducing the tower's weight is to calculate the percentage of the total weight contributed to by the legs, diagonal braces, glue and any other piece glued to the tower. That way one can decide what to trim to reduce weight. I would expect that in 7 gram towers, or less, the legs account for over 50 percent of the total weight, and that the weight of the glue is less than 15 percent.

[lllazar]

My base is around 3.5 grams, so yes i think those numbers sound about right....