Elevated Bridge B/C

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Re: Elevated Bridge B/C

Post by robotman »

thats where i got it and the weight that it had been stated was almost if not exactly the same when i got it so it didn't change over shipping
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Re: Elevated Bridge B/C

Post by nejanimb »

Balsa Man wrote:
nejanimb wrote:Balsa man, do you just mean the scores from the top 6 this year? Or have you actually found images of what they did?
Scores- with weights and weight held - # provide a "picture" of how it went...
nejanimb wrote:Also, where do you find balsa down to 1/64th thickness? I can't really even find 1/32 thickness wood anywhere... which supplier do you use? The thinnest wood we used this year was 1/16th, but I definitely think there were instances where thinner wood would have helped.
Specialized Balsa in Loveland, CO - check out their website; they do lots of mail order business; Jake, the owner is great to work with - and its really great having him just a few miles down the road. In addition to weight-graded sticks, they have sheets, down to 1/64th, which you can also get in weighed/weight-graded.

I suppose part of the problem is that I would be very intimidated by sheets - I've never cut my own sticks before. I feel like I would have inconsistent cuts. How can you be sure? Is there a tool to do it well?
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Re: Elevated Bridge B/C

Post by jander14indoor »

Yep, there is a tool. Somewhere way back in this string should be a discussion of something known as a balsa stripper and how to use it well. If not this string, look in the Wright Stuff string. I posted it in one of those. Also much discussion about why its smart to start with sheets to ensure quality balsa.

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Re: Elevated Bridge B/C

Post by blue cobra »

I tried making my own balsa stripper, mainly just for kicks, and it was a complete failure :lol:
Do you know of a place where I can get a decent balsa stripper? Also, suppose you are cutting a strip and it doesn't cut straight. You now have a wavy edge to your sheet. How would you smooth this straight again so you can cut another good strip?
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Re: Elevated Bridge B/C

Post by andrewwski »

Cut it again, discard the piece with the wavy edge.
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Re: Elevated Bridge B/C

Post by smartkid222 »

is there a picture of the angle-iron lamination anywhere?
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Re: Elevated Bridge B/C

Post by blue cobra »

andrewwski wrote:Cut it again, discard the piece with the wavy edge.
Yes, but many strippers rely on a straight edge to put the stripper against. If there is a wavy edge you don't have this. I suppose you could draw a straight line with a square and use a ruler and a razor to cut it straight again.
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Re: Elevated Bridge B/C

Post by jander14indoor »

One of the tricks of stripping balsa is to cut the sheet to about the length you need for our final pieces. Longer is harder to do. Don't strip a 36 inch sheet if your longest pieces are 18 inches, cut it in half length wise and strip 18 inch long sheets.

I mention this because its much easier to straighten a short sheet's edge than a long one's.

To straighten a wavy edge, you need a good, straight metal rule. Or any good thinnish straight reference, but metal is better so you don't cut it with the knife. And while a machinist rule is handy I'm not talking one of those expensive precision accurate to .001 inches per foot things. Use that with a good knife to get that good first edge straight. Strip until you start getting wavy, then straighten again.

Good knife skills are one of the things you need to learn/develop for all the SO building event and much under appreciated.

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Re: Elevated Bridge B/C

Post by Aia »

Throughout this season, I purchased balsa sticks to build my bridges. However, I found the sticks well worth my time because it was easy to compare densities from one piece to another. In several locations of my bridge, I wanted the lowest possible wood density for a given size, so I simply weighed 36" sticks until I found the .4g/stick pieces I wanted (same goes for the 7 other densities of wood I needed).

Now, when stripping balsa, how do you know you'll get a desired density? Some wood densities are very difficult find. If you strip an entire sheet of balsa, wouldn't all the resulting wood be the same density? If some resulting pieces of wood were a variety of densities, wouldn't you then have to be extremely cautious, seeing as the balsa sheet wasn't uniform density?

It seems to me that while stripping might be cheaper per stick, you'd create a lot of wood that you'd never use. Is this true in any sense? Do you find that resulting wood sticks are close in density? What kind of success have people had with structures that used stripped balsa?
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Re: Elevated Bridge B/C

Post by smartkid222 »

Aia wrote:Throughout this season, I purchased balsa sticks to build my bridges. However, I found the sticks well worth my time because it was easy to compare densities from one piece to another. In several locations of my bridge, I wanted the lowest possible wood density for a given size, so I simply weighed 36" sticks until I found the .4g/stick pieces I wanted (same goes for the 7 other densities of wood I needed).

Now, when stripping balsa, how do you know you'll get a desired density? Some wood densities are very difficult find. If you strip an entire sheet of balsa, wouldn't all the resulting wood be the same density? If some resulting pieces of wood were a variety of densities, wouldn't you then have to be extremely cautious, seeing as the balsa sheet wasn't uniform density?

It seems to me that while stripping might be cheaper per stick, you'd create a lot of wood that you'd never use. Is this true in any sense? Do you find that resulting wood sticks are close in density? What kind of success have people had with structures that used stripped balsa?
I also purchase sticks. I guess i'm just too lazy to cut my own from sheets. I have purchased sheets before though, but for uses mainly with Wright Stuff. People have menchioned how balsa has a very wide range of densities and how variations can exist even in a single strip of balsa. To put it simply, if you take a 1g strip of balsa 36" and cut it in half, you may get .4 and .6 grams. Someone menchioned that they weighed each piece of balsa before using it due to these variations. Now if such vairations occur in strips, they are definetly going to occur in sheets as well. Like i said i dont' use sheets, but i guess i would find a sheet that has an average density of what i want, and then cut it down to strips. some stips would be too dense, and some would be too light, but there would be some that you could use. I also assume that people look at each sheet and use common sense and look for really big variations and not buy that particular sheet.



Also i think balsa strippers are pretty expensive ($150+?). when i cut strips i use a metal ruler and my blade.
When i cut i pick one side to be the side i never cut. In this case it would be side A. If i mess up cutting side B and it comes out wavy

A ---------------B
A----------------B
A----------------B

| (I mess up a cut)
V

A-------------B
A------------B
A-----------B


I measure from A to the closest B. In this Case it would be 11 dashes. Then i measure off this distance at the top and bottom and cut it to even it out

A-------------B
A------------B
A-----------B

| ( I mark off equal distances from A)
V

A-----------|--B
A-----------|-B
A-----------|B

| ( I cut it where i marked it)
V

A-----------B
A-----------B
A-----------B

:D
Now i would continue cutting and try to not mess up again

I hope this answers any questions about cutting sheets and it becomes 'wavy'. If it doesn't, then disregard it :D .
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