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RE: Exotic Wood Question

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Also, consider using West System epoxy.  It is a two part (1:5) system that can be bought in two cans with plungers on top that proportion the epoxy mix correctly.  My youngest son used it on his soap box derby car instead of the Elmer's glue suggested.   Used to buy West System epoxies at boat stores.

In reviewing the criteria of your nephew's, what is the competitive part of the olympiad?   Higher load?  Minimum deflection?

There are a variety of woods available at some hobby shops.  Here's an on-line website that has balsa, mahogany, walnut, basswood (?), cherry and spruce.  Table 4.4 of the Wood Engineering Handbook  shows the mechanical properties of most of these woods.

Good luck.

Neil Moore, S.E.

At 03:07 PM 12/29/2004, Lucas Jolly wrote:
When I was in high school and had a similar project, I got beat by a kid using this technique...
You said the laminations had to be a max of 1/8".  Get some 1/32" balsa wood strips and soak the stuff in the epoxy of your choice.  Clamp it together and when it dries you will have a solid epoxy/wood block.  Can't beat it.
The kid who came up with this that ended up breaking every school record with his bridge.  I'm pretty sure he thought of him without his uncle's help ;)

From: Caldwell, Stan [mailto:scaldwell(--nospam--at)]
Sent: Wednesday, December 29, 2004 8:36 AM
To: SEAINT Listserv
Subject: Exotic Wood Question
Importance: Low

I am writing on behalf of my nephew, Jake, who is in the eighth grade.  He is participating in a science olympiad and needs to fabricate a laminated wood beam and load test it.  According to Jake, the beam must span 350 mm (13.78") and be no higher than 40 mm (1.57") and no wider than 20 mm (0.79").  It must be a straight, solid rectangular section fabricated from strips of wood no thicker than 3.175 mm (0.125"), glue, and nothing else.  Finally, it must support a center load of 15 Kg (33.1#) with a deflection less than 20 mm (0.79").
I am thinking that the winning beam will be fabricated from wood that is dense and very fine-grained, without knots or other irregularities.  In other words, an exotic hardwood from South America or Asia, like Pau Lope or Teak, rather than good old Southern Pine or Douglas Fir.  The wood must be available in Dallas, or available online with delivery within the next two weeks.  Of course, such woods do not appear in NDS, so I have very limited information on them.  Also, I am thinking that the laminations should be vertical, rather than horizontal.  This should make a stronger beam, and make the glue choice less important.
1]    What wood species do you recommend?  What are its mechanical properties?
2]    Do you concur with vertical laminations?
Thanks in advance for your thoughts.
Stan R. Caldwell, P.E.
Vice President

8616 Northwest Plaza Drive
Dallas, Texas 75225
Phone: 214-346-6280
Fax: 214-739-0095
Email: scaldwell(--nospam--at)