Towers B/C

[MadCow2357]

It's definitely a risk to travel with the tower in any way, though traveling by car is definitely safer for the tower. CA glue joints will take a few weeks to deteriorate, if that's what you're wondering. At least, that's what the general consensus came to be after some discussion in the forum.

[cheese]

It's definitely a risk to travel with the tower in any way, though traveling by car is definitely safer for the tower. CA glue joints will take a few weeks to deteriorate, if that's what you're wondering. At least, that's what the general consensus came to be after some discussion in the forum.

Yeah CA will take a few weeks to go bad, but you still want 24-48 hours to let it fully dry based on my trials.

[MadCow2357]

I know this is very very very late in the season, but I am going to design a final tower that will hopefully help me break the 2000 score mark. After rereading through Balsa Man's (may he rest in peace) lengthy Euler's critical load formula, I finally understood at least some of the stuff he was talking about. But I do still have some things I have questions about:

For our “design strength” for this analysis, we’ll use 4499gr, which is applying a 10% safety factor to the 4090gr force a base segment leg in B tower meeting the 29cm circle bonus will see at a 15kg tower load.

Does this 4499g only apply to square base towers? I can only build rectangular base towers, since I do not have access to a good jig.

E = the modulus of elasticity (aka Young’s modulus) of column material. This is the inherent stiffness of a piece of wood; it doesn’t depend on, it doesn’t have a relationship to size/cross section. It does have a linear relationship to the density. As discussed in previous posts, as wood density increases, E increases. On average, if you double the density (increase it by a factor 2), E goes up by a factor of about 2.25, but there is significant “variation around the mean”- two sticks, same size and same weight can have significantly different E values, which means significantly different BSs. This is what I was talking about when I noted wood is not a homogeneous material.

Does this mean that if I have a 0.4g 12" 1/8"*1/8" stick, I should get a elasticity of about 0.45g? I am a little confused on whether I need to use certain units (eg pounds per cubic foot, but I don't know how to calculate that) for the equation to work properly.

I = minimum area moment of inertia (sometimes referred to as the 2nd moment of inertia) of the cross section of the column. For a square cross section leg, where the length of the sides are x, I = (x^4)/12. (that’s x to the fourth power, divided by 12

What is the minimum moment of inertia? I am still in middle school, so I apologize for not getting basic physics concepts.
And what are inverse square calculations?

Again, sorry for asking pretty basic questions. I will admit that the tower design I have been using for the last month or two was not formulated from any math.

I also apologize for double posting, but I am on a real time crunch before nationals and I want to get as much done as possible.

[windu34]

I know this is very very very late in the season, but I am going to design a final tower that will hopefully help me break the 2000 score mark.
I also apologize for double posting, but I am on a real time crunch before nationals and I want to get as much done as possible.

Okay I have never competed in Balsa events, but I have read through Balsa Man's methods for designing and it is NOT something you can just read, understand, and implement properly. PLEASE do yourself a favor and focus on building the best tower you can using methods you have been using throughout the year and delve into experimenting with new methods AFTER nationals. You have many years of Scioly ahead of you to experiment with these methods and improve, but 1 week before nationals is NOT the time for this

[Girlpower05]

The inverse square relation is that if you divide the lenght of a stick by 2, then the buckling strength will increase 4 times, likewise if you divide the lenght by 4 then the buckling strength will be 16 times more.

So lets say you have a 91.5 cm stick with a BS of 30. For your 27 cm chimney with 5 X bracings, each interval is 5.4 cm.
To calculate the BS of each interval:
5.4/91.5 = 0.059
.059^2 = 0.003481
1/0.003481 = 287.27
287.27 * 30 = 8,618
If you use X bracings only then you multiply this number by 0.55
8,618 * 0.55 = 4,740
Each leg can hold 4,740 grams, so multiplying this by 4, your chimney could hold 18,960 grams.
You can do your own calculation like this by substituting your own values.
I am also in div B and don’t understand physics stuff, but just know how to use the calculations.

[Cow481]

Does pretesting a tower weaken it significantly? If so how much?

[TheSquaad]

Does pretesting a tower weaken it significantly? If so how much?

What do you mean by pretesting? If you mean putting a tiny bit of weight (<600g) to check stability, it shouldn't matter. But if you're going much higher than that, the wood starts to get stressed, and subsequently weakens.

[stevepilot]

Ok, so I know this is really random, and if this isn't the right place to post it, I apologize, but do you think they will care if I write a "in memory of Balsa Man" on the tower? The rules say only markings leftover from the construction process are allowed...

[Cow481]

I think that the event supervisor will allow that because it is in memory of balsaman and he is from fort collis with also helps allow it.

[TheChiScientist]

Who is Len Joeris? He was before I joined so I am a little clueless.
Also if you can I would ask. If it's written in pen it should be fine...