Message-Id: <1.5.4.32.19980521035218.0069fe78@tscnet.com>
Date: Wed, 20 May 1998 20:52:18 -0700
To: baidarka@lists.intelenet.net
From: stephen <syahn@tscnet.com>
Subject: Re: [baidarka] to peg or not to peg
I believe you are correct. I also observe that flathead screws have a
coneical undersurface to the head. This would certainly wedge apart the
fibers of the wood. However any of the screwheads which have flat underheads
would be a little less distructive. In my view.
Steve Yahn
At 11:50 AM 5/20/98 EDT, you wrote:
>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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