Date: Tue, 21 Jan 1997 08:42:41 -0500
From: Bill Low <billow@capecod.net>
To: baidarka@lists.intelenet.net
Subject: Re: Split keelson
Tom Clarke wrote:
>
> Regarding split keel... or more properly, an articulated keel... the
> gunnels in the baidarkas were designed to provide the anti-hogging
> strength of the vessel... they are very stiff in the vertical plane...
> yet the keel flexes... It seems to me that the flex in the keel
> combined with the stiffness of the gunnels ends up to be like springs
> and shock absorbers in a car... the frame (gunnels in the baidarka)
> does not bend, but the wheels (bottom in the baidarka) can flex over
> bumps (waves)... Is this correct?...Tom in Newark...
Interesting thought..
Some additional comments on the split keelson. Before I put the skin on
I just had to see what the split keelson did to the flexibility of the
frame. On the bench I tried flexing it in hog and sag; bow and stern. In
hog the upward movement of the keelson was restrained by the ribs
forward of the split. The forward section of the keelson was able to
move upward held only by the ribs and the lashing used at each split.
The movement of the keelson upward tried to reduce of the cross section
of the hull.
In sag it was another story completely. The movement of the bow upward
caused the split to try and move downward. It was resisted by the ribs
and the locking of the notch cut into the split and the lashing. The
downward movement of the split also tried to increase cross section of
the hull.
I would expect the skin to have no noticeable effect in hog but would
resist the sag. The design is obviously intended to reduce sag movement
and have smaller resistance to hog. In use sag would be expected every
time the boat sat in a wave trough. Hog would only happen if the bow or
stern were heavily laden and the boat were at the wave crest.
All of this suggests that they wanted the additional flexibility but
they also wanted it controlled. In effect a shock absorber.
Bill Low
billow@capecod.net