Pictures, Videos, and Scores

[Balsa Man]

Any compression member is only as strong as its weakest axis... If your ladders are 1/8" x 1/16", they will be no stronger in compression that a 1/16 x 1/16 member... These should be square... either 1/16 x 1/16, 1/8 x 1/8 or split the diff and go for 3/32 x 3/32...

Imagine making your columns 1/8" x 1/4" and you'll see what I mean.

Tension members, on the other hand are just the opposite... Making them a little wider increases the gluing surface to the columns, making them thinner (as thin as 1/64") will reduce the weight while maintaining the strength. These do not need to be square.

And FWIW, lets get the terminology correct... "beams" are members that run horizontally... The Ladders, could actually be considered beams.
What I think you have referred to as Beams are actually the columns... vertical or semi-vertical members that transfer the specified load down to the table.

Overall, beautiful tower!... but to be competitive, we need to shed about 50% of the weight. It would help us analyze it, if we knew the column weights and / or bending strengths Then we could identify if the number of tiers of bracing could be reduced.

Well covered, Dan. I agree on all points.
To do an initial design, and even more importantly, to refine a design- get the weight down (your challenge), or strength up (if someone has a really light tower that's not carrying much load ), you have to be tracking/aware of densities and strengths- at a minimum stick weights (at 36"), and buckling strength at 36" for legs (the term I use; Dan's 'columns', your 'beams') and ladders (legs and ladders being the components that come under compression loading, and will fail by buckling). With this data you can calculate, and know exactly how to get the weight down.

[Towerofterror]

Thx for the suggestions. I will use square pieces for compression from now on. Will try to find 1/32 for X's. Legs were buckling at about 2-3 kg. Hard to get an exact reading when I was pressing down on the scale. Legs were about 2.3 grams a piece when I put them on (1/8 x 1/8 x 51-ish cm)

[Balsa Man]

Thx for the suggestions. I will use square pieces for compression from now on. Will try to find 1/32 for X's. Legs were buckling at about 2-3 kg. Hard to get an exact reading when I was pressing down on the scale. Legs were about 2.3 grams a piece when I put them on (1/8 x 1/8 x 51-ish cm)

As you'll see if you review past posts, those leg weights are way heavy- you can go to a lot lighter. Legs from 36" sticks weighing around 1.6/1.7gr each, with bracing at 1/4 interval (vs your pictured 1/9 interval) should get you close to carrying full load. That'll save you a lot of weight.

[Nathan4444]

I don't think this is necessarily meant to be clickbait, as it does show a tower being tested (albeit not to the claims stated). It may have good intentions, but there is something definitely wrong with it.
First of all this is 6 years ago, but I guess it doesn't disqualify it as a tower, as long as it fits the current rules. Second, there is no way that this is getting a score of 2800 under the current rules (or even past rules). There must have been a testing error or calculation error. A score of 2800 would allow a maximum mass of 6.07 grams (assuming it gets the bonus) and just from the size of the tower alone it doesn't even look under 10 grams. It also doesn't look particularly strong, no way that's holding 15 kg.
tl;dr
This video won't help anybody at all. Best to ignore.

[H_zhang]

I don't think this is necessarily meant to be clickbait, as it does show a tower being tested (albeit not to the claims stated). It may have good intentions, but there is something definitely wrong with it.
First of all this is 6 years ago, but I guess it doesn't disqualify it as a tower, as long as it fits the current rules. Second, there is no way that this is getting a score of 2800 under the current rules (or even past rules). There must have been a testing error or calculation error. A score of 2800 would allow a maximum mass of 6.07 grams (assuming it gets the bonus) and just from the size of the tower alone it doesn't even look under 10 grams. It also doesn't look particularly strong, no way that's holding 15 kg.
tl;dr
This video won't help anybody at all. Best to ignore.

It was 5.38 grams holding full load breaking at 14.9 g, it was previously but it will work under this year rules, that is our design, I'm trying to get a video out of the 2800 one we just tested. It looks pretty same, just more sticks on the bottom.

[H_zhang]

Currently uploading the video for the 2800 tower.

[Towerofterror]

Thx for the suggestions. I will use square pieces for compression from now on. Will try to find 1/32 for X's. Legs were buckling at about 2-3 kg. Hard to get an exact reading when I was pressing down on the scale. Legs were about 2.3 grams a piece when I put them on (1/8 x 1/8 x 51-ish cm)

As you'll see if you review past posts, those leg weights are way heavy- you can go to a lot lighter. Legs from 36" sticks weighing around 1.6/1.7gr each, with bracing at 1/4 interval (vs your pictured 1/9 interval) should get you close to carrying full load. That'll save you a lot of weight.

Thx for the suggestions. I'm limited by cost...idk if I can swing the online stores so I go shopping at Blick's, HL and Michael's. Blick's had the cheapest sticks. I forgot my scale and hefted and bought what I thought were the 10 lightest. When I weighed them I found the usual wide range of weights and chose 4 that were in the middle but close to each other.

Sorry if this was already answered, but should I choose the 4 lightest or the 4 closest together? If I had a 1.6g, 1.7g, 2.2g, and 2.3g, wouldn't the lighter ones break pre-maturely?

[Balsa Man]

Thx for the suggestions. I'm limited by cost...idk if I can swing the online stores so I go shopping at Blick's, HL and Michael's. Blick's had the cheapest sticks. I forgot my scale and hefted and bought what I thought were the 10 lightest. When I weighed them I found the usual wide range of weights and chose 4 that were in the middle but close to each other.

Sorry if this was already answered, but should I choose the 4 lightest or the 4 closest together? If I had a 1.6g, 1.7g, 2.2g, and 2.3g, wouldn't the lighter ones break pre-maturely?

I certainly understand your cost constraint, and the issue/need to....do the best you can with what you can get.
With the question being how do you get it lighter, and taking that into consideration-

There is (pages and pages of) detailed info just waiting for you to read/digest that explains how to figure out what a leg will carry- depending on it's buckling strength, and the intervals its braced at. There's a general relationship between stick density and buckling strength, so you can....take the quick and dirty approach of just using stick weights for design. While I believe most of the following data has been presented/discussed, a quick set of data for 1/8 " balsa:

Stick weight Buckling strength
1.0gr 55gr
1.2gr 70gr
1.4 gr 84gr
1.6 gr 105gr
1.8 gr 120gr
2.0 gr 135gr
2.2 gr 153gr
2.4 gr 170gr
2.6gr 188gr

These values are approximate median values- individual sticks at these densities will vary as much as +/-20%. The stated buckling strengths are values you can use to do the inverse square calculations needed to determine increased strengths at various bracing intervals.

You are correct that the weakest/lightest leg in a set will fail first.
You should be looking for the lightest.....reasonably matched (say within 0.1 -0.2gr) you can assemble, and figure out the bracing interval needed to brace them to 'design strength'.

[RJohnson]

Just recently got put on towers. Built my first tower after having read this topic. Great source of information- provides a good starting point for anyone. In division C, got a score a bit less than 1500. Definitely know where to start making improvements. Now it's time to build - break - build...

Good luck to all and thanks to those who have contributed!

[Towerofterror]

Thx for the suggestions. I'm limited by cost...idk if I can swing the online stores so I go shopping at Blick's, HL and Michael's. Blick's had the cheapest sticks. I forgot my scale and hefted and bought what I thought were the 10 lightest. When I weighed them I found the usual wide range of weights and chose 4 that were in the middle but close to each other.

Sorry if this was already answered, but should I choose the 4 lightest or the 4 closest together? If I had a 1.6g, 1.7g, 2.2g, and 2.3g, wouldn't the lighter ones break pre-maturely?

I certainly understand your cost constraint, and the issue/need to....do the best you can with what you can get.
With the question being how do you get it lighter, and taking that into consideration-

There is (pages and pages of) detailed info just waiting for you to read/digest that explains how to figure out what a leg will carry- depending on it's buckling strength, and the intervals its braced at. There's a general relationship between stick density and buckling strength, so you can....take the quick and dirty approach of just using stick weights for design. While I believe most of the following data has been presented/discussed, a quick set of data for 1/8 " balsa:

Stick weight Buckling strength
1.0gr 55gr
1.2gr 70gr
1.4 gr 84gr
1.6 gr 105gr
1.8 gr 120gr
2.0 gr 135gr
2.2 gr 153gr
2.4 gr 170gr
2.6gr 188gr

These values are approximate median values- individual sticks at these densities will vary as much as +/-20%. The stated buckling strengths are values you can use to do the inverse square calculations needed to determine increased strengths at various bracing intervals.

You are correct that the weakest/lightest leg in a set will fail first.
You should be looking for the lightest.....reasonably matched (say within 0.1 -0.2gr) you can assemble, and figure out the bracing interval needed to brace them to 'design strength'.

Thank you.