Bonus weight in Towers B

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Re: Bonus weight in Towers B

Post by Balsa Man » December 14th, 2016, 4:52 am

Llamastwaimzjf wrote:Yes. And that is the fastest breaking point of my tower, I plan on using balsa . Would you recommend that?
Without more information, no way to guess why they're breaking, other than saying they're not strong enough. What size wood are you using (as in cross section dimension)> What density (as in weight of 36" sticks)? What interval are you bracing at? What's your tower weight, and what sort of load is it breaking at?
As already explained, there are three ways to make them stronger: 1) use higher density wood (of the same cross-section as you're using now, 2) brace them more (as in shorter braced interval- if you're bracing at 1/4 interval, go to bracing at 1/5, or 1/6 interval, 3) increase cross section.

I'm confused when you say you "plan on" using balsa. In another post you said you were using bass. As discussed in great length in various posts, 1/8" balsa looks like the way to get to the lightest tower (that will carry close to full load).

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Re: Bonus weight in Towers B

Post by Random Human » February 12th, 2017, 8:11 pm

Balsa Man wrote:
Llamastwaimzjf wrote:Yes. And that is the fastest breaking point of my tower, I plan on using balsa . Would you recommend that?
Without more information, no way to guess why they're breaking, other than saying they're not strong enough. What size wood are you using (as in cross section dimension)> What density (as in weight of 36" sticks)? What interval are you bracing at? What's your tower weight, and what sort of load is it breaking at?
As already explained, there are three ways to make them stronger: 1) use higher density wood (of the same cross-section as you're using now, 2) brace them more (as in shorter braced interval- if you're bracing at 1/4 interval, go to bracing at 1/5, or 1/6 interval, 3) increase cross section.

I'm confused when you say you "plan on" using balsa. In another post you said you were using bass. As discussed in great length in various posts, 1/8" balsa looks like the way to get to the lightest tower (that will carry close to full load).
Balsa Man, let's do some reanalysis on the bonus.
You claim the bonus can in fact lead to a higher score, I disagree.
Here are a few things to consider:
1. With the bonus, you are changing a square base from 16 cm, to 22, cm an 8 cm increase. -> more use in leg wood
2. Next, with the legs farther apart, more bracing wood is required, as well as stronger bracing wood
3. The more angled tower, leads to less strength among the legs itself.
4. all of these disadvantages are in exchange for 2000 grams extra to your score
5. If you are just going for a 2000 scoring tower, you would have to be at 8.5 with the bonus, 7.5 without, to make all these changes (steps 1, 2, 3) you would need according to my calculations more than a gram to make it work (hold all)
These are my insights and my ideas, no means to argue
What are your thoughts?
Thanks for insights
Random Human - Proud (former) Science Olympian. 2015-2017
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Re: Bonus weight in Towers B

Post by BuildingFriend » February 12th, 2017, 8:19 pm

Random Human wrote:
Balsa Man wrote:
Llamastwaimzjf wrote:Yes. And that is the fastest breaking point of my tower, I plan on using balsa . Would you recommend that?
Without more information, no way to guess why they're breaking, other than saying they're not strong enough. What size wood are you using (as in cross section dimension)> What density (as in weight of 36" sticks)? What interval are you bracing at? What's your tower weight, and what sort of load is it breaking at?
As already explained, there are three ways to make them stronger: 1) use higher density wood (of the same cross-section as you're using now, 2) brace them more (as in shorter braced interval- if you're bracing at 1/4 interval, go to bracing at 1/5, or 1/6 interval, 3) increase cross section.

I'm confused when you say you "plan on" using balsa. In another post you said you were using bass. As discussed in great length in various posts, 1/8" balsa looks like the way to get to the lightest tower (that will carry close to full load).
Balsa Man, let's do some reanalysis on the bonus.
You claim the bonus can in fact lead to a higher score, I disagree.
Here are a few things to consider:
1. With the bonus, you are changing a square base from 16 cm, to 22, cm an 8 cm increase. -> more use in leg wood
2. Next, with the legs farther apart, more bracing wood is required, as well as stronger bracing wood
3. The more angled tower, leads to less strength among the legs itself.
4. all of these disadvantages are in exchange for 2000 grams extra to your score
5. If you are just going for a 2000 scoring tower, you would have to be at 8.5 with the bonus, 7.5 without, to make all these changes (steps 1, 2, 3) you would need according to my calculations more than a gram to make it work (hold all)
These are my insights and my ideas, no means to argue
What are your thoughts?
Thanks for insights
I still think it's worth it- disregarding all the numbers and making a qualitative claim- adding two WHOLE kilograms at a low weight changes the efficiency dramatically. At the higher levels of building (coming from where I am) we use such thin wood that adding even five pieces of bracing does not register on our 0.1 precision scale (adding on glue probably then 0.1g). And 2000 is too low an estimate- to win probably 2700 would suffice which makes 2kg margin even larger. Strength of bracing wood is not really a matter- glue area is. The more angled tower (longer hypotenuse and base) would require a slightly more dense compression member to make up for the BS- still I feel less significant than the added 2kg. Balsaman probably has the math better than me and a better idea of the bonus than me so just my two cents
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Re: Bonus weight in Towers B

Post by dholdgreve » February 13th, 2017, 6:44 am

Random Human wrote:
Balsa Man wrote:
Llamastwaimzjf wrote:Yes. And that is the fastest breaking point of my tower, I plan on using balsa . Would you recommend that?
Without more information, no way to guess why they're breaking, other than saying they're not strong enough. What size wood are you using (as in cross section dimension)> What density (as in weight of 36" sticks)? What interval are you bracing at? What's your tower weight, and what sort of load is it breaking at?
As already explained, there are three ways to make them stronger: 1) use higher density wood (of the same cross-section as you're using now, 2) brace them more (as in shorter braced interval- if you're bracing at 1/4 interval, go to bracing at 1/5, or 1/6 interval, 3) increase cross section.

I'm confused when you say you "plan on" using balsa. In another post you said you were using bass. As discussed in great length in various posts, 1/8" balsa looks like the way to get to the lightest tower (that will carry close to full load).
Balsa Man, let's do some reanalysis on the bonus.
You claim the bonus can in fact lead to a higher score, I disagree.
Here are a few things to consider:
1. With the bonus, you are changing a square base from 16 cm, to 22, cm an 8 cm increase. -> more use in leg wood
2. Next, with the legs farther apart, more bracing wood is required, as well as stronger bracing wood
3. The more angled tower, leads to less strength among the legs itself.
4. all of these disadvantages are in exchange for 2000 grams extra to your score
5. If you are just going for a 2000 scoring tower, you would have to be at 8.5 with the bonus, 7.5 without, to make all these changes (steps 1, 2, 3) you would need according to my calculations more than a gram to make it work (hold all)
These are my insights and my ideas, no means to argue
What are your thoughts?
Thanks for insights
Hmmm. Let's think about this... The difference in column lengths stated is 50.30 vs 50.71 cm... .41 cm per column... let's assume a 4 column tower... that is an additional 1.64 cm in columns... A typical tower column might weigh .7 grams... divided by 50 cm times 1.64 = an addition of .02296 grams of columns. Granted, the braces get longer... let's assume a typical 7 tier tower... that's 14 braces per side x 4 sides = 56 braces... bottom braces get ~ 3 cm longer... top braces remain the same... so assume an average of 1.5 CM longer x 56 = 84 cm additional braces... Ahh he says... but they are at an angle... you are correct. let's round that up to 100 cm... the braces we use weigh an average of.2 grams for a 100 cm strip... no added glue.

So... if we add the .2 grams of bracing to the .02296 of column length extra, we get .22296 added material weight... By your own assessment, the break even point is a full gram of mass difference (7.5 grams to 8.5 grams)
Based on these numbers, that allows over 3/4 of a gram to extend your ladders, or stiffen your columns to carry the slight increase in load.

So yes Human, the Bonus is most certainly worth it... :lol:
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Re: Bonus weight in Towers B

Post by Balsa Man » February 16th, 2017, 10:03 am

BuildingFriend wrote:Balsa Man, let's do some reanalysis on the bonus.
You claim the bonus can in fact lead to a higher score, I disagree.
Here are a few things to consider:
1. With the bonus, you are changing a square base from 16 cm, to 22, cm an 8 cm increase. -> more use in leg wood
2. Next, with the legs farther apart, more bracing wood is required, as well as stronger bracing wood
3. The more angled tower, leads to less strength among the legs itself.
4. all of these disadvantages are in exchange for 2000 grams extra to your score
5. If you are just going for a 2000 scoring tower, you would have to be at 8.5 with the bonus, 7.5 without, to make all these changes (steps 1, 2, 3) you would need according to my calculations more than a gram to make it work (hold all)
These are my insights and my ideas, no means to argue
What are your thoughts?
Thanks for insights
Balsa Man, let's do some reanalysis on the bonus.
Cool, let's
You claim the bonus can in fact lead to a higher score, I disagree.
Here are a few things to consider:
1. With the bonus, you are changing a square base from 16 cm, to 22, cm an 8 cm increase. -> more use in leg wood.
Yes, but very little; about 1cm/leg = just under 4cm more, and density the same

2. Next, with the legs farther apart, more bracing wood is required, as well as stronger bracing wood
Yes, more wood (longer ladders and Xs), but no, not really, on “stronger” (as in higher density) bracing required; very low density works in both cases- for ladders above the bottom one, 0.7gr/36 (1/8”), lowest density you’re going to find is more than strong enough.
3. The more angled tower, leads to less strength among the legs itself.
I think you’re trying to say, more angle = higher forces at a given load; however, that increase is very small (<0.05kg, at a 15kg tower load)
4. all of these disadvantages are in exchange for 2000 grams extra to your score
The noted ‘disadvantages’ are small, and the +2kg is large
5. If you are just going for a 2000 scoring tower, you would have to be at 8.5 with the bonus, 7.5 without, to make all these changes (steps 1, 2, 3) you would need according to my calculations more than a gram to make it work (hold all)
That’s not what my calcs say.
These are my insights and my ideas, no means to argue
No problem- this kind of argument/dialog, and thinking about all the issues in play to analyze this, is a good thing; science and engineering at work.
What are your thoughts?
Thanks for insights

The analysis I ran looks at a C-tower, legs at 1/8”,1.4gr/36” legs, braced at 1/5 interval, ladders (at 1/8”, 0.75gr/36”) and Xs (1/64 x 1/16 at 0.00224 gr/cm) bracing.
For tower meeting the bonus
Legs- 245.2cm, weight 3.75gr
Ladders- 225.5cm, weight 1.85gr
Xs- 802cm, weight 1.8gr
Glue, 1gr
Total = 8.39gr; score if 15kg held =2026.1; score if 14kg held =1906.9

For tower not meeting the bonus
Legs- 242.64cm, weight 3.71gr
Ladders- 165.10cm, weight 1.35gr
Xs- 641.6cm, weight 1.44gr
Glue, 1gr
Total = 7.50gr; score if 15kg held = 2000.7; score if 14kg held =1867.3

Close, yeah, but the bonus tower wins, and as you come down from full load held, the winning margin increases. This doesn’t surprise me, because over the years, in wood structures, and other building events, every time the rule makers have included a bonus it has been very carefully designed to pay off. There’s a lot of careful thought that goes into coming up with and defining bonuses to work this way. The analysis above is….conservative a) because using 0.75gr/36” to calculate for ladders, but 0.7gr/36” is strong enough for both versions, and b) the lighter the tower, the bigger the difference/payoff. For folk shooting for >2000, the bonus is even more important.
Len Joeris
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Re: Bonus weight in Towers B

Post by BuildingFriend » February 16th, 2017, 10:23 am

I didn't post what you replied to above...? (it was RandomHuman's post) But thank you for the analysis!
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Re: Bonus weight in Towers B

Post by Balsa Man » February 16th, 2017, 11:07 am

Hey, sorry 'bout that. Fell a bit silly, but... it got the analysis out there.
I'd been ....tied up in other things for the last few says, and rushing to catch up here. :roll:
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Re: Bonus weight in Towers B

Post by EastStroudsburg13 » February 19th, 2017, 9:45 am

Question that came up during Penn about the bonus:

If the Tower initially spans the bonus weight after check in, but then during loading the Tower deforms to the extent that a piece of it is now touching within the circle, is the bonus now lost? This is a hypothetical, as I don't recall this happening with any team's tower, but I wanted to ask out of curiosity.
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Re: Bonus weight in Towers B

Post by bernard » February 19th, 2017, 11:10 am

EastStroudsburg13 wrote:Question that came up during Penn about the bonus:

If the Tower initially spans the bonus weight after check in, but then during loading the Tower deforms to the extent that a piece of it is now touching within the circle, is the bonus now lost? This is a hypothetical, as I don't recall this happening with any team's tower, but I wanted to ask out of curiosity.
Yes, 3.a. specifies "no part of the tower may touch or be supported within the 29 cm circle" to qualify for the bonus. A Tower touching within the 29 cm circle does not "span a 29 cm diameter circle."
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Re: Bonus weight in Towers B

Post by Unome » February 19th, 2017, 6:03 pm

bernard wrote:
EastStroudsburg13 wrote:Question that came up during Penn about the bonus:

If the Tower initially spans the bonus weight after check in, but then during loading the Tower deforms to the extent that a piece of it is now touching within the circle, is the bonus now lost? This is a hypothetical, as I don't recall this happening with any team's tower, but I wanted to ask out of curiosity.
Yes, 3.a. specifies "no part of the tower may touch or be supported within the 29 cm circle" to qualify for the bonus. A Tower touching within the 29 cm circle does not "span a 29 cm diameter circle."
There's also a FAQ on this if I remember correctly (stating that it has to be outside until failure).
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