To: baidarka@lists.intelenet.net
Subject: Re: [baidarka] to peg or not to peg
From: jeff.woodall@juno.com (Jeffrey G Woodall)
Date: Wed, 20 May 1998 11:50:30 EDT
Hi there~
Having survived engineering school with my humanity intact, I thought I'd
give my two cents on the peg vs screw vs lashing inquiry.
>From a basic "Strength of Materials" point of view, ANY material removed
from the gunwales acts to weaken their resistance to the bending moment
existing along their length. At the deck beam cross sections the mortise
cut has already removed 1/4 to1/3 of the material, so it seems to me that
in the interest of maintaining flexibility and strength , lashing is the
way to go.
If holes are going to be drilled through the gunwale (ie for pegging),
they should be through the mid-point with the axis of the hole(s)
perpendicular to the bend of the gunwale. This places them along the
"neutral axis" where, in theory, no bending stress exists ( stress
increases linearly with distance from the mid-point: inboard =max
compression; outboard=max tension).
Screws seem like a bad choice because their threads are going to "work"
the wood as the frame flexes, possibly initiating a crack in the gunwale
or the deck beam tenon.
Well, that's one opinion. I wonder if anyone has done a 3D frame analysis
on the baidarka. The joints get worked in so many ways that it would be
difficult to account for all the loadings.
Regards,
Jeff
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