Re: [Paddlewise] Hypalon Skin/Hull Repair Questions

David Kosofsky wrote:

> 1) Is it better to repair the skin when it is stretched (i.e., when the
> kayak is assemble) or when it is loose (i.e. off the frame entirely)?

Stretched, so the patch has maximum strength when under use (tension).  If you
patch it when the hull is relaxed, stretching will tend to separate the layers
through shear.

> 2) Would it make sense to patch the hole from the INSIDE (in the interest of
> avoiding a hydrodynamics-impairing external patch) or would that leave the
> external wound liable to be enlarged?

Outside is better.  The hydrodynamic drag is minimal.

> 3) Assuming the patch is done from the outside, what can be done to minimize
> the deformation of the hull's smoothness. That is, how can the patch be made
> to blend with the contour of the hull?

This is tough.  Of course, any shaping of the patch will have to be done BEFORE
adhering it to the hull.

With a fresh, single-edged razor blade, you may be able to cut away a wedge of
the Hypalon (on the outside of the patch) to feather the edges.  If you have
access to liquid nitrogen, you can freeze the Hypalon and then (quickly!)
abrade the edge with sandpaper.  It will warm up quickly, so you will have to
refreeze it and repeat.  (We used to drill holes in rubber stoppers using
conventional twist drills when the stoppers were frozen.   Makes nice clean
holes.)

BTW, clean the Hypalon with lacquer thinner after shaping and before you apply
the glue.  Roughen the surfaces to be glued to give fresh Hypalon.  Poor
surface prep is the main cause of glue failure.

-- 
Dave Kruger
Astoria, OR
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