[NSRCA-discussion] An education in balsa usage for pattern

[Don Ramsey]

My daughter, in a high school class, built a bridge using 1/4 sq balsa.  She still holds the record at her school.  The bridge was 12 inches long, 1 inch wide, weighed 14 grams and supported 70.5 lbs hung under the bridge.  Last year the max weight held was 42 lbs.  She did use good techniques in the construction but with a little more testing she could have gone much higher..  I've seen balsa towers 12 inches tall weighing in the 15 gram range hold over 300 lbs in compression.
  ----- Original Message ----- 
  From: Wayne Galligan 
  To: NSRCA Mailing List 
  Sent: Wednesday, March 29, 2006 8:35 AM
  Subject: Re: [NSRCA-discussion] An education in balsa usage for pattern


  Matt,

  My son did his 5th grade science project using balsa construction.  His project was to determine what bridge truss design held the most weight for a given span.  It was truly amazing how much weight the structure would hold.  The spans he built where 7"x7"x24" and weighted 1.5 oz, made of 1/4" square med grade balsa glued together with thin c/a.  The Warren truss held 42 lbs before collapsing and the two other structures were close behind holding 32 to 38 lbs.  It was a learning experience for both of us.  It gave me a better understanding of how certain truss structure builds stiffness, strength and be light weight.   

  Wayne Galligan
    ----- Original Message ----- 
    From: rcmaster199 at aol.com 
    To: nsrca-discussion at lists.nsrca.org 
    Sent: Tuesday, March 28, 2006 6:58 PM
    Subject: Re: [NSRCA-discussion] An education in balsa usage for pattern


    Balsa is pretty amazing stuff overall, particularly for a natural material. The Xylem that makes up much of the superstructure of any wood (that's what we commonly hear as grain), is essentially a huge number of tubes arrayed side by side, but interconnected along the length. The tubes serve a terrific function in the long direction and the interconnects make the structure have reasonable transverse strength as well. 

    The closest thing manmade that will surpass it in terms of mechanical strength vs flex vs weight vs cost will likely be Buckytube if you excluded the cost. That's just in laboratories now, being made in very small quantities supporting very high end applications. This stuff is the true unobtainium that some have complained about. But that's another subject.

    There used to be an annual competition in colleges where a very small, known quantity of balsa and glue were used creatively by students to build some kind of support structure like a small bridge. These things would hold unbelievable amounts of weight. 

    Alas, the weakness is shock loading. 

    Matt
     
    -----Original Message-----
    From: Adam Glatt <adam.g at sasktel.net>
    To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
    Sent: Tue, 28 Mar 2006 16:44:02 -0600
    Subject: Re: [NSRCA-discussion] An education in balsa usage for pattern


Not directly applicable to pattern, but certainly a good start:
Buy and build a Stevens Aeromodel kit. The planes are small (35-50" 
span, 1-2.5lbs) and electric powered. I'm about 1/2 done building the 
Edge 540, and am actually enjoying the build because I am constantly in 
awe of the genius wood design and its results (consider that this Edge 
540 is 40-sized, but will weigh only 2lbs with more performance than all 
but the most dedicated 40-sized 3D glow planes).

-Adam

White, Chris wrote:
>
> Can anyone tell me where a person can get a "Crash" course in learning 
> about balsa weights and strength and its proper use in balsa pattern 
> models.
>
> I notice a few years ago that in the 99 world champs most of the 
> Japanese pilots models were balsa and light weight too. It seems that 
> everything I read of late seems to indicate that light weight and 
> strength only come with composite construction.
>
> Thanks..Chris
>
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