Re: [Paddlewise] : Boat Strength and Weight/ compare skin boats to fiberglass

on 10/11/00 11:32 PM, Nick Schade at schade_at_guillemot-kayaks.com wrote:

> Matt,
> In your opinion, how strong should a kayak be? Do you have anything
> besides experience with boats which have survived/failed to base your
> opinion on?
> 
> The reason I ask is I am working with a grad student who is looking
> to do some testing on this subject. We are currently discussing the
> conditions to investigate. He wants to find out how strong the
> materials need to be, to be "strong enough".
> 
> Obviously, the ocean can always produce a bigger wave than you
> planned on, but we are trying to come up with reasonable estimates.
> 
> 
> 
> Everyone,
> If you have had a boat fail, how did it fail, what were the paddling
> conditions, and what kind of material was the boat?
> 
> I suspect most failures are do to hitting some object while being
> pushed by a wave. How often does it happen that the force of the surf
> just tears a boat apart?

Nick,

Most of the fiberglass sea kayaks that I have seen break were full of water
(cockpit area) after a wet exit in the surf.  The stress of breaking waves
and the weight of all that water in the boat is enough crack a hull or deck,
even in sandy beaches with no rocks.  (This is one of the reasons Matt Broze
and others recommends a sea sock in the surf)

I've seen enders in the surf that cracked a kevlar deck when the bow hit the
sandy bottom.  I know of one fiberglass sea kayak that got a crack in the
hull in 8 to 10 foot surf.  Just the impact of the wave breaking, no contact
with the bottom.

My own experience breaking a fiberglass kayak, surf kayak not a sea kayak,
was from making the stupid mistake of getting caught in a steep shore break
on the Washington coast.  I went completely vertical (bow up) and smashed
the stern when I came down.  About 20 inches from the end the stern folded.

Is your grad student friend only interested in fiberglass?  How about a
comparison between skin boats and fiberglass.  I have a wood frame skin boat
(yellow cedar, red cedar, and white oak, nylon fabric with polyurethane
coating).  It weighs 32 pounds.  It is an engineering wonder.  Lots of
flexible pieces lashed together.  No glue or metal fasteners.  The boat
flexes on impact.  The forces are distributed among many flexible pieces.

Does anyone know if any engineers have done tests comparing wood frame skin
boats with fiberglass?  I'm putting my money on the skin boats.  5,000 years
of skin-boaters can't be wrong. :)

Rex


  


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