Date: Fri, 30 May 1997 18:58:48 -0700 (PDT)
From: "R. Murray" <rossm@u.washington.edu>
To: baidarka@lists.intelenet.net
Subject: Re: Laminated ribs, etc..
In-Reply-To: <338F592C.825@boi.hp.com>
I just did some quick calculation on the strength and flexibility of wood
beams in bending vs AL tubes. The dimensions were found for square wood
beams that have equivalent or greater strength and stiffness in bending
than a given Aluminum tube.
For an Aluminum tube 0.5"D x 0.049", a sitka spruce square 0.51" on
a side will be roughly equivalent. The AL tube will weigh about
0.086lb/foot, while the spruce will be about 0.047lb/foot.
For an AL tube 0.75" x 0.049" (0.13 lb /ft), a sitka spruce square 0.67"
square (0.082 lb /ft) will suffice.
These calculations do not take into account the variations of the
materials. Wood is highly variable in both dimensions and properties, so
to achieve the same reliability as an AL beam, a wooden beam would have to
be much thicker than calculated here.
-Ross