Buying Wood

User avatar
WhatScience?
Member
Member
Posts: 394
Joined: July 16th, 2017, 4:03 pm
Division: C
State: NJ
Contact:

Buying Wood

Postby WhatScience? » September 17th, 2017, 1:50 pm

Where do you guys buy your wood? Most places I see the wood is to thick/wide.
"When you clean your room, you are increasing the total chaos of the universe" - Hank Green Crash Course (Entropy)

Events 2018

Thermodynamics, Potions and Poisons, Disease Detectives, Optics, and Towers

User avatar
JasperKota
Exalted Member
Exalted Member
Posts: 160
Joined: October 22nd, 2015, 8:01 pm
Division: C
State: NY
Location: WEHS
Contact:

Re: Wood

Postby JasperKota » September 17th, 2017, 3:15 pm

I've found Michaels to have a selection of balsa sticks and sheets, local hobby shops probably have a wide range as well.

From what I hear, online is the way to go. Specialized balsa (http://www.specializedbalsa.com/products/index.php) offers balsa sticks and sheets with custom densities, widths, etc. for a price, but it's a lot more convenient and easier than having to go through and choose from different grains and densities offered in stores.
2018 Events: Helicopters, Mousetrap Vehicle, Parasitology, WIDI
2017 Events: Invasives, Wright Stuff, Ecology
2016 Events: Invasives, Dynamic Planet, Crave the Wave

retired1
Member
Member
Posts: 657
Joined: July 25th, 2012, 5:04 pm
Division: Grad
State: FL
Contact:

Re: Wood

Postby retired1 » September 17th, 2017, 4:06 pm

Look at Sig contest balsa. You need to email or call about this. It is good most of the time and a lot cheaper.

cool hand luke
Member
Member
Posts: 95
Joined: October 4th, 2016, 10:04 am
Division: B
State: TX
Contact:

Re: Wood

Postby cool hand luke » September 17th, 2017, 5:22 pm

I just looked at sig balsa, and it seems like they only use the lowest density. Which is great if that's what your design needs, but useless if you need something outside this range.

retired1
Member
Member
Posts: 657
Joined: July 25th, 2012, 5:04 pm
Division: Grad
State: FL
Contact:

Re: Wood

Postby retired1 » September 17th, 2017, 7:05 pm

for regular balsa and not contest balsa, they have 6-9, 9-12, 13-16 #/cf page 82 of the catalogue

$.25 upcharge for grain selection and $.35 upcharge for weight selection.
I did not see any prices. In the past, they were typically a bit more than National (highly variable quality) and a fair amount less than Speciality balsa.

User avatar
cheese
Member
Member
Posts: 204
Joined: April 8th, 2017, 7:59 pm
Division: C
State: -
Location: Wherever the cheese is
Contact:

Re: Wood

Postby cheese » September 17th, 2017, 7:28 pm

I do the math for how much the density for my ideal leg would be, then multiply by how many of the legs I can get out of a 4-36'' sheet. Then I go to either Michael's or hobby lobby and bring my scale. It seems there are always a couple good sheets.
2018 Nationals: 2nd Place Mystery Architecture || 6th Place Battery Buggy
Cheese's Userpage

Balsa Man
Coach
Coach
Posts: 1318
Joined: November 13th, 2008, 3:01 am
Division: C
State: CO
Location: Fort Collins, CO
Contact:

Re: Wood

Postby Balsa Man » September 19th, 2017, 6:33 am

WhatScience? wrote:Where do you guys buy your wood? Most places I see the wood is to thick/wide.


It really comes down to how competitive are you trying/willing/able to be, and are we talking engineering or art?

I’m really curious how you came to the conclusion that the wood you saw was too thick/wide? It suggests you have a sense of what is… just right, and I’m wondering what that sense is grounded in. Folk who succeed in being seriously competitive (let’s say medaling at State) ground it in engineering. Others, who do not yet have an understanding of the basic engineering involved create (sometimes) a really cool looking structure that scores a fraction of what the ‘good’ structures do.

The American Engineers' Council for Professional Development (ECPD) has defined "engineering" as “the creative application of scientific principles to design or develop structures, machines, apparatus, or manufacturing processes, or works utilizing them singly or in combination; or to construct or operate the same with full cognizance of their design; or to forecast their behavior under specific operating conditions; all as respects an intended function,

Folk who succeed in being seriously competitive have done enough study to understand the key ‘scientific principles’ that allow you to design a ‘good tower.’ Or perhaps they are fortunate enough to have a coach/teacher who understands those principles, and has taught them. The Scioly board is a resource that provides the largest…library of information on the science and engineering of Science O towers (and bridges and boomilevers). If you go back to the 2017 archives for towers -https://scioly.org/forums/viewforum.php?f=243– you’ll find over a hundred pages of information. The first topic just happens to be two pages on ‘Wood Orders’… I strongly urge you, and anyone who hasn’t yet gotten to an understanding of how to ‘engineer’ a good tower design, to take the time to read through this unique library of information.

You’ll find that the vast majority of folk with competitive towers used 1/8” x 1/8” wood for legs; some used 5/32”, some used 3/32. For bracing pieces, the picture is more diverse, and depends on the bracing configuration (e.g., ‘ladders and Xs’, ‘all Xs’, ‘Z-bracing’)

OK, on to where to get wood. I and many others have come to the conclusion that if you are or want to be seriously competitive, Specialized Balsa in Loveland, Colorado is the best place. http://www.specializedbalsa.com/products/

Why? Because you can get sticks in 1/10gram weight increments (and sheets at specific weights). Why does that matter? Because to build a competitive tower, you’re looking for/you need the very lightest wood that are strong enough to carry the forces produced in the pieces/members that make up the tower.

Summarizing very briefly:

First, you need to know the forces that the legs will see under a 15kg tower load (if you go to the “Towers B/C” thread, you’ll see where I posted a table that provides those forces for the upper and lower leg segments for towers meeting this year’s rules (and meeting the 29cm circle bonus).
Then you need to figure out the bracing interval you want to use. This critical aspect/step of the design process is looking at a basic trade-off; is it better (more efficient) to use lighter, ‘floppier’ legs with more bracing- a tighter bracing interval, or heavier, ‘stiffer’ legs with less bracing- a wider bracing interval. To do this, you need to understand how buckling works, how the buckling strength of a long piece (a leg, or in this year’s case a leg segment (upper, ‘chimney’ section, and lower, ‘base’ section) is increased by bracing (the braced points turn the long piece into a set of shorter “stacked” pieces). The increase in buckling strength has an ‘inverse square’ relationship to length.

What does that mean? If you have a stick of x length that has a buckling strength of y, and you brace it at the midpoint (cutting the ‘braced length’ length to ½x), the buckling strength of the two halves (and therefore the entire stick) will be 4 times y (1 divided by ½ squared). If you brace it at the 1/3 points (cutting the braced length to 1/3x), the buckling strength of the braced segments, hence the entire stick will be 9 times y (1 divided by 1/3 squared). There’s very detailed discussion in past posts of exactly how to test buckling strength of balsa sticks, and apply those measurements to get to the “design” buckling strength for legs/leg segments you want to use.

A piece of very important information that is in the ‘Wood Orders’ thread is a graph of buckling strengths vs 36” stick weights. What you’ll see is that there is a clear relationship between density (stick weight) and buckling strength- if you double the density, the buckling strength is roughly doubled (actually, doubling density bumps buckling strength by about a factor of 2.25). But the other thing you can see is there is ‘variation about the mean’ in the density vs buckling strength relationship- at a given stick weight, buckling strength will vary. What you’re looking for, for a really competitive tower is a set of sticks/legs that are the very lightest that have the ‘design buckling strength’ you need.

Lots of words to get to the why ordering from Specialized makes sense if you’re seriously trying to produce a ‘winning’ tower. It’s a matter of time and economics. With enough time, by going to local stores with a scale, you might eventually get a few sticks that are close to your design buckling strength. By ordering from a place that uses …fairly broad increments of sorting (e.g., between 6 and 8 pounds per cubic foot density), if you order and sort through enough sticks, you will find a few that meet your design buckling strength, and if you’ve ordered enough, of those that meet your design buckling strength, a full set, or sets will be significantly lighter than the others; it’s a statistical game. However, if you know, to a 1/10 of a gram the stick weight likely to have the buckling strength you need, you can order to that narrow range. Example, from the graph on 1/8” stick weight vs buckling strength, you see an average 1.5gr stick has the buckling strength you want, and some 1.4gr ones do…..order a reasonable numbers of 1.4s.
Len Joeris
Fort Collins, CO

tarsavage
Member
Member
Posts: 2
Joined: December 12th, 2017, 5:22 pm
State: -
Contact:

Re: Wood

Postby tarsavage » December 12th, 2017, 5:29 pm

Can anyone recommend a good width for the wood (1/8", 1/10" etc.?) Preferably something that will thin enough to be rather light, but still thick enough that it won't snap easily. I've never done Towers before and I don't know exactly what to expect, so any help will be greatly appreciated!

SPP SciO
Member
Member
Posts: 251
Joined: March 24th, 2015, 8:21 am
Division: B
State: NY
Location: Brooklyn
Contact:

Re: Wood

Postby SPP SciO » December 12th, 2017, 7:04 pm

tarsavage wrote:Can anyone recommend a good width for the wood (1/8", 1/10" etc.?) Preferably something that will thin enough to be rather light, but still thick enough that it won't snap easily. I've never done Towers before and I don't know exactly what to expect, so any help will be greatly appreciated!


1/8” square is common to find and can be totally viable. It’s big enough to work with comfortably since you’re first getting started, but light enough to where you won’t have an embarrassingly heavy tower!

But if you spend some time reading this forum, you’ll realize that it’s a lot more complicated than that. Build a tower with whatever sticks you have available, measure each piece first and note the mass and size on your plan, and then read more and reflect. Good luck!
Coach
MS 821 Sunset Park Prep
http://www.sppscio.com

User avatar
cheese
Member
Member
Posts: 204
Joined: April 8th, 2017, 7:59 pm
Division: C
State: -
Location: Wherever the cheese is
Contact:

Re: Buying Wood

Postby cheese » December 12th, 2017, 7:33 pm

tarsavage wrote:Can anyone recommend a good width for the wood (1/8", 1/10" etc.?) Preferably something that will thin enough to be rather light, but still thick enough that it won't snap easily. I've never done Towers before and I don't know exactly what to expect, so any help will be greatly appreciated!


You can either go in depth and have a competitive tower, or just do what SPP SciO said and use good old trial and error. If you were to go in depth, you can read through the 2017 towers forum and the current 2018 forum. To answer your question, there isn't a necessarily "good" width, there are many factors involved. But with the many tests, it seems that 1/8 to 5/32 are ones to go for.
2018 Nationals: 2nd Place Mystery Architecture || 6th Place Battery Buggy
Cheese's Userpage

emilyshangg
Member
Member
Posts: 12
Joined: February 10th, 2018, 8:28 pm
Division: C
State: TX
Contact:

Re: Buying Wood

Postby emilyshangg » March 1st, 2018, 12:36 pm

Yoooo Anyone know where to buy the ULTRA LIGHT wood?
Before you ask, yes I have tried SIG, National, Specialized, Amazon, and I'm checking out f1d.biz.
But somehow, those that are winning have wayyyy more wood on their tower than I do, and are half the weight.
I'm just about to plant my own balsa tree and harvest my own sticks so... any other ideas? ANYthing would help!! Thanks! <3


Return to “Towers B/C”

Who is online

Users browsing this forum: No registered users and 2 guests