All

As I mentioned in passing a week or so ago, the younger daughter had to
build a bridge as her final projects in physics.  She chose a classic
trestle design (from a bridge in Baltimore I think).  We went to the
hardware store, guesstimated our needs (typical galoot project, huh?), and
bought some basswood and balsa wood.  Once we got home and started laying
out the components, and figuring the cuts, we realized we needed more wood
(again, typical).  So I started her cutting and gluing the pieces we had,
and went back to the store.  Of course, they were out of stock on the sizes
we needed, so had to buy bigger stock (again, typical).  Once we got the
few main pieces cut glued and clamped up, using all my available
lightweight clamps (again, typical), she got sidetracked (again, typical).
She decided some embellishment on the base might be nice, maybe carving or
stamping some words or dates into the standards.  So, I set her up with
some basswood blocks and the carving chisels, and away she went (again,
typical).  I took a nap (again, typical).  When I woke, she was still side
tracked on carving, and not on the 2nd round of glue ups (again, typical).
Got her back on track, and a bridge got built.  There were a few course
corrections and design changes along the way (again, typical), and
execution not being able to meet design standards (again, typical).  We
spent most of Sunday and a little time Monday on it.  Finished it well
ahead of schedule (not typical), but we thought we had a much shorter
timeline to due date.

The weigh off was today, the criteria to win, most weight held / bridge
weight, while spanning 2 benches.  She tied on the most weight held, but
the other girl's bridge was smaller and lighter.

Then, being the daredevil that she is, she asked me "Do you think the
bridge is strong enough to let a small person stand on it."  I assumed she
meant in spanning mode, so said no, only about 20#.  But, once she had her
grade, she was free to experiment.  With the bridge on the floor, it
finally failed at, 243 pounds.  One of the cross pieces let go, not quite
enough glue, the balsa fractured.  I was AMAZED it held that much.

My contribution to the project: Loaning tools and explaining how to best
use them, holding pieces while clamping, little bit of engineering and
geometry review, and financial backing

Tools used: mini miter box and razor saw, all my little clamps and some
clothes pins, small squares, Incra marking tool, dividers, drafting
triangle, sandpaper, Titebond
Diversion tools used but not part of project, carving gouges, mallets,
safety glove.

A few pics here
http://kirkhmb.smugmug.com/Woodworking/Carly-Bridge-Project/23135936_Krh7zW#!i=1863802019&k=kgGBJx7

-- 
Kirk Eppler in Half Moon Bay, CA
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