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Date: Sat, 5 Feb 2000 11:09:20 +0900 (KST)
From: David Kosofsky
Subject: [Paddlewise] Hypalon Skin/Hull Repair Questions

An unplanned and unfortunate encounter with a sharp submerged rock while
paddling my Feathercraft K-Light down the Ocissa River near Tallahassee this
afternoon has me suddenly interested in the details of the technique for
repairing a small hole in a hypalon skin.  I have the Feathercraft-supplied
kit: glue, hypalon patches and somewhat laconic instructions.   I'm left
with the following questions:

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)?

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?

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?

4) Any other bits of advice (other than, "ALWAYS BRING DUCT-TAPE," which
will be my mantra from now on)?

Thanks,

David Kosofsky

ps-- Lest this be construed as criticism of Feathercraft, of hypalon, or of
folding kayaks, let me hasten to mention that of MANY unplanned encounters with
rocks, coral-reefs, etc., this is the first to cause a puncture in the skin,
and that far greater damage would have been sustained had the boat been
fiberglass, wood, kevlar, plastic, or any other `rigid kayak' material.

pps--And lest this be construed as criticism of the Ocissa River, let me hasten
to mention that you'd be hard put to find a more lovely paddling destination,
and that in addition to the odd hidden rock, the river offers countless blue
heron, all sorts of ducks, racoons on the banks, enormous turtles sunning on
the rocks, several artesian springs, Spanish Moss dangling from the trees and
dipping languidly into the water...




Date: Fri, 04 Feb 2000 21:04:10 -0800
From: Dave Kruger
Subject: 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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