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From: Matt Broze <mkayaks_at_oz.net>
subject: RE:[Paddlewise] : Boat Strength and Weight
Date: Wed, 11 Oct 2000 03:35:04 -0700
Peter Treby <ptreby_at_ozemail.com.au> wrote:
>>>Matt writes:
"Here in the Northwest the public demands and gets a kayak that is a little
too lightweight
to take hard pounding on rocks or enders in surf."
That immediately prompts me to think that if that is the case, the
knowledgeable manufacturer ought to supply a heavier seaworthy boat as
standard, and supply a lighter boat on demand after explaining its lack of
strength and attendant risks.<<<<
Most paddling in the Seattle, WA/Vancouver, BC area is on inland waters and
few paddlers venture off the coast. Since 19 out of 20 paddlers will choose
the lighter kayak if given a choice (and they get all the information you
suggest) why would a dealer want to stock the kayak for 5% of the customers
and have to order custom kayaks for the other 95%. Since almost all the
orders for our kayaks are custom orders I'm only faced with this problem for
the other companies kayaks I handle as a retailer.
I don't like seeing any kayak I sell come back damaged much less broken. You
can be sure that we make our standard lay-up strong enough to stand up to
surf big enough that few paddlers will go beyond the kayaks limits. Those
who might usually know it and can get heavier lay-ups. You can also be sure
that any paddler wanting a custom lightweight kayak is informed of the
limitations of that kayak (bigger surf, rocks in breaking surf, and boat
over boat rescues). The line of price point fiberglass kayaks we carry have
their least expensive lay-up choice also being their strongest and heaviest
lay-up. What most who buy it want is a good kayak at a low price. They
suffer a little extra weight but get a stronger stiffer kayak as well. They
don't break them and I'm happy not doing repairs.

>>>On referring to the bible, Derek Hutchinson's "The Complete Book of Sea
Kayaking" 4th Ed, Chapter One, it opens with general comments about design,
and there is plenty of discussion of the design considerations useful to a
buyer. I can't find any mention of weight. There is a little about North
American designs, pages 19, 20 and 21, with recommendations for reinforcing
weak decks.
Where's the problem with the bible?

Same problem I have with any "bible", I don't believe it!
Actually the book you mentioned used to be called "Sea Canoeing" in some
earlier editions and that is not the manuscript I was commenting on. Derek
was writing a guide for North America to be published by Pacific Search
Press in Seattle. Pacific Search was trying to get me to sign a contract to
write a "Deep Trouble" style book based on the Sea Kayaker articles I had
been writing as kayak safety editor. They showed me Derek's original
manuscript to what became "Derek Hutchinson's Guide to Sea Kayaking". This
was an inferior book to "Sea Canoeing" (which I don't recommend either as I
think there are several better texts on the market). The "Guide to...."
included a lot of survival stuff that was a poor rehash of other works that
had little to do with kayaking. I still want to see Derek make a fire
without matches using the methods described in the book. I'm in agreement
with John Winters about Derek's hull design writing and I didn't think much
of his safety and rescue information either (my two areas of self-proclaimed
expertise). David Zimmerly told me Derek's history was all wrong and David
Burch ("Fundamentals of Kayak Navigation" and at least five other major
navigation textbooks) showed me a copy of Derek's Guide to... he had marked
(with an orange felt pen) each sentence that had an error in it (in Derek's
navigation section). Half of it was orange. Not being an expert in those
areas I wouldn't have been nearly as critical. Derek is good on paddling
skills but tends to try to write the rest of the book off the top of his
head as well and gets a lot of things wrong. I read the first edition of
"Sea Canoeing" that my brother got at the library before I was ever a sea
kayaker and I can recall realizing that some things Derek had written just
couldn't be true (at least if other things he had written earlier were
true).
Note: I realized that it must have been in 1986 or 1987 that I saw the
manuscript rather than 1983 or 1984 as I had guessed earlier. I'm at home
and my copy is at work or I'd check the copyright date and quit guessing.

>>>There are a few weak, but popular boats here as well. Some you can
depress
the deck in places with one finger. That worries me, but the sales staff
tell you that it's strong enough. Have a look at the boat cracked in half 5
kms off shore at:
http://www.nswseakayaker.asn.au/forsale.htm
Regards,
Peter Treby<<<<

Thanks for the picture Peter, but what happened to the kayak? Let me guess,
boat over boat rescue as advocated in some bibles?

Matt Broze
http://www.marinerkayaks.com


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From: Nick Schade <schade_at_guillemot-kayaks.com>
subject: RE:[Paddlewise] : Boat Strength and Weight
Date: Wed, 11 Oct 2000 19:32:51 -0400
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



><snip>
>I don't like seeing any kayak I sell come back damaged much less broken. You
>can be sure that we make our standard lay-up strong enough to stand up to
>surf big enough that few paddlers will go beyond the kayaks limits. Those
>who might usually know it and can get heavier lay-ups. You can also be sure
>that any paddler wanting a custom lightweight kayak is informed of the
>limitations of that kayak (bigger surf, rocks in breaking surf, and boat
>over boat rescues). The line of price point fiberglass kayaks we carry have
>their least expensive lay-up choice also being their strongest and heaviest
>lay-up. What most who buy it want is a good kayak at a low price. They
>suffer a little extra weight but get a stronger stiffer kayak as well. They
>don't break them and I'm happy not doing repairs.
<snip>
-- 


Nick Schade
Guillemot Kayaks
824 Thompson St, Suite I
Glastonbury, CT 06033
(860) 659-8847

Schade_at_guillemot-kayaks.com
http://www.guillemot-kayaks.com/

>>>>"It's not just Art, It's a Craft!"<<<<

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From: Rex Roberton <rexrob_at_mac.com>
subject: Re: [Paddlewise] : Boat Strength and Weight/ compare skin boats to fiberglass
Date: Wed, 11 Oct 2000 23:47:13 +0000
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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From: ralph diaz <rdiaz_at_ix.netcom.com>
subject: Re: [Paddlewise] : Boat Strength and Weight/ compare skin boats to fiberglass
Date: Thu, 12 Oct 2000 08:51:25 -0700
Rex Roberton wrote:
SNIPPED
> 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

I have anecdotal information on folding kayaks being banged through surf
in the same waters as hardshells and the folding boats doing fine
whereas the hardshells developin hard to repair (in the field) cracks. 
But nothing scientific.

You mentioned totally flooded hardshell kayaks sustaining damage when
moved around.  I know of a similar situation with a totally flooded
folding kayak, which was recovered by a fishing boat.  In their handling
of the folding kayak (a double Klepper) and bringing it aboard fully
loaded with water and camping gear, they broke a few wooden frame pieces
with a small puncture of the kayak's deck by one jaggered frame piece.

I also have a validated account of several folding kayaks being picked
up by a tornado and smashed against concrete structures with no damage. 
But I really don't know what the forces were (except severe winds) and
only have the person's thought that a fiberglass boat might have
sustained damage.

I don't want to spark a holy war on hardshells vs. skinboats (or folding
ones) but there is something to be said about an internal structure that
has lots of give to it and a flexible skin.

ralph diaz 
-- 
-----------------------------------------------------------------------
Ralph Diaz . . . Folding Kayaker newsletter
PO Box 0754, New York, NY 10024
Tel: 212-724-5069; E-mail: rdiaz_at_ix.netcom.com
"Where's your sea kayak?"----"It's in the bag."
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From: Nick Schade <schade_at_guillemot-kayaks.com>
subject: Re: [Paddlewise] : Boat Strength and Weight/ compare skin boats to fiberglass
Date: Thu, 12 Oct 2000 09:44:46 -0400
Sam McFadden is doing testing primarily on strip-built 
wood/fiberglass/epoxy composites, but the same conditions apply no 
matter what the construction method.

I am sure that the 5,000 years of evolution of the Aleut and Inuit 
boats was not wrong, but since we don't know exactly what their 
design criteria were, we can't say what was right or wrong for them. 
It is quite possible to design the perfect kayak for a given task 
that can not survive being pushed into the sand while surfing 8 foot 
waves.

It is hard to compare one construction method vs another unless you 
know the design criteria. I can promise you that Matt or any other 
fiberglass kayak manufacturer can build a stronger fiberglass kayak 
than what was typical of the skin-on-frame. And, any woodworker can 
build a stronger skin-on-frame than the typical fiberglass kayak. 
Generally you can make the structure stronger by adding more 
material. The question is can you build a stronger boat with one 
method which does not weight more than one built with another method. 
Then you need to look at the kind of strength needed and what 
constitutes a failure. Dropping on a rock, jamming and end into the 
sand while surfing and pushing through steep chop all require 
different forms of strength and will have different failure modes.
Nick


At 11:47 PM +0000 10/11/00, Rex Roberton wrote:
>
>Nick,
>
>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
>
>
>

-- 


Nick Schade
Guillemot Kayaks
824 Thompson St, Suite I
Glastonbury, CT 06033
(860) 659-8847

Schade_at_guillemot-kayaks.com
http://www.guillemot-kayaks.com/

>>>>"It's not just Art, It's a Craft!"<<<<
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From: Peter Treby <ptreby_at_ozemail.com.au>
subject: RE: [Paddlewise] : Boat Strength and Weight
Date: Thu, 12 Oct 2000 20:43:32 +1000
"... what happened to the kayak? Let me guess,
boat over boat rescue as advocated in some bibles?
Matt Broze"

Matt, and Nick, and other builders, makers and designers: Now that the cause
of this boat fracture is revealed to be a triple cartwheel (with or without
pike), doesn't a sea kayak have to be capable of handling this punishment?
I don't think you'd see a boat over boat rescue here in these circumstances.
But the capsize T rescue seems useful, particularly if you come across a
boat without a pump. Maybe the boat you have to rescue had a hand pump
tucked under the front bungies, and it was washed away in the cartwheeling.
Why not have a deck strong enough to carry out a boat over boat rescue
without the boat breaking up? Why not keep all options open?
Has anyone ever had experience of a boat breaking across the centre of the
hull because of a boat over boat rescue, as Matt suggests is possible? Or
other breakage due to these rescues?
I like the idea of a boat with a reserve margin of strength, a little
overdesigned. Now, if that's possible without needing Olympic standard
weightlifting talent...
Regards,
Peter Treby
37°42'S 145°08'E


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From: Bob Denton <BDenton_at_aquagulf.com>
subject: RE: [Paddlewise] : Boat Strength and Weight
Date: Thu, 12 Oct 2000 08:49:59 -0400
I own an Eddyline Falcon 16 built in a special light lay-up. It weight in at
34lbs and requires a lot more care than my Nordkapps. I once called Eddyline
about the boat and they mentioned that they no longer offer that lay-up
because too many came back broken. They stated that the boat was never
designed for surfing, but as a light weight touring boat.

The boat is light enough to lift over my head to drain the water but you can
depress the deck with one finger. I think it's a case of "Horses for
Courses". Used in the appropriate conditions it is the perfect boat. 

You wouldn't use an 17 lb road bike with 20cm tires to ride rocky trails and
you wouldn't win any road races on a mt. bike.

Weight is an important consideration for me, since I usually paddle solo and
have to heft my boats on top of a minivan, carry them solo to the put in.
Even my current Carbon Nordkapp is a bit heavy at 48 lbs. It has a
reinforced deck, rock solid, but I'd prefer the older carbon/kevlar deck
which saved 3 or 4 lbs. 

cya






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From: Kirk Olsen <kolsen_at_imagelan.com>
subject: RE: [Paddlewise] : Boat Strength and Weight
Date: Thu, 12 Oct 2000 14:46:36 -0400 (EDT)
On Thu, 12 Oct 2000, Bob Denton wrote:

> The boat is light enough to lift over my head to drain the water but you can
> depress the deck with one finger. I think it's a case of "Horses for
> Courses". Used in the appropriate conditions it is the perfect boat. 

I regularly paddle a lightweight boat.  It's 19'6" and under 28 pounds.
At some point it's going to break.  I accept that.  

To keep it going as long as possible I try to avoid any conditions 
(collision or large breaking waves) that will do it in.  At some point I 
won't be successful and it's going to break and probably sink.  

Until then it's a pleasure to paddle and carry it.

kirk


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