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Subject: Re: [world-cruising] Fiberglass or Steel
lewhodgett@XXX.XXX
Date: Wed May 14 2003 - 23:01:07 EDT
"Russ Swan" writes:
>The following illustrates one point and is a true one. An aged
>English
>gentleman came to Darwin and put his boat alongside the careening
>poles at
>one of the local yacht clubs. He'd been around the world several
>times in
>his backyard built steel boat... and it looked it too. It had bangs
>and
>buckles all over the boat. He'd hit things and been hit by all sorts
>of
>other things.
Maybe he needed to improve his basic navigation skills a bit.<G>
>Alongside him was a chap with a solid looking fibreglass boat. Both
>these
>men were in the bar one night with the latter chap expounding how
>strong his
>fibreglass boat was, to the point of saying it was as strong as steel.
> At
>this the Brit finally got fed up. He said, "Tell you what! I'll get
>out a
>5lb sledgehammer and we'll take turns banging each other's hulls.
>I'll even
>let you go first, and we'll see which boat stands up to it best". The
>offer
>was declined.
An interesting story that repeatedly gets told at the club bar, being
embellished a little more with each retelling; however, there is some,
but no much, merit to the tale.
It should be noted, all fiberglass is not the same.
Polyester resin, woven roving and mat laminates are relatively "brittle"
compared to mild steel which is more ductile. (That and $5.00 will get
you a cup of coffee in a cheap place)
The vast majority of older fiberglass boats are probably constructed of a
solid polyester, mat and roving construction.
Some of the old ones that are still around could probably take a direct
hit from a missle, they were so overdesigned, but I digress.
Then along came the cored hull concept which utilizes things like balsa
wood, isocyanate activated PVC foam (Divinycell) and non isocyanate
linear PVC (Airex) foam, to reduce weight and improve strength.
After that, along comes CoreCell as another core material option.
Again the skins of this cored sandwich construction were usually
polyester resin and glass.
The following are purely personal observations.
Balsa has no place on a yacht, but it makes great model airplanes and
should stay there.
Divinycell is a good foam for things like a deck core; however, it's
rather limited energy absorption does not make it the best choice for a
hull core, IMHO.
Airex is designed as an energy absorbing foam. It's total function in
life is to allow the outer skin to be sacrificed in the event of a
collision while protecting the integrity of the inner skin to insure that
the vessel does not sink.
Polyester resin, roving and mat skins do an adequate job; however, epoxy
along with knitted glass is far superior.
Epoxy is more ductile than polyester, has a higher glass to resin ratio
than polyester, and is less weight for a greater strength than polyester.
The boat I'm building is built using epoxy, knitted glass and Airex core
for the hull and Divinycell core for the deck.
The tag line in my sig file contains the following:
"S/A: Challenge, The Bullet Proof Boat (Under Construction in the
Southland)"
Why, you ask?
Well, because it is bullet proof.
When I finished the stern/deck joint, had some waste pieces of cored
laminate about 5"-6" wide x 12"-15" long x 1-1/2" thick which I took to a
local shooting range where I got a lot of lead for my ballast.
Hung the cored laminate up as a target, stepped back about 20 ft, and
fired several copper jacketed .357 magnum projectiles into it.
Funny thing, the projectiles entered the front of the laminate,
completely piercing the front laminate, but none exited out the back
laminate.
They were all trapped by the Airex.
I keep that piece of sandwich containing the .357 slugs around as a
conversation piece.
Might want to ask yourself, how thick a piece of steel does it take to
stop a copper jacketed .357 magnum from 20 feet?
I can tell you this much, a .357 magnum will stop a running automobile
engine dead cold in it's tracks.
Basically 1020 hot rolled steel is very low cost compared to other
building materials, is much heavier than other boat building materials,
and requires a lot of maintenance.
It is also has a very low strength to weight ratio.
You can build it strong, but that makes it heavy.
Heavy = SLOW for a wind powered vessel.
Ultimately, rust gets you, rust from the inside where you can't see it
and thus can't repair it.
Bottom line................
Fiberglass is an engineered system which can address most problems and
provide a relatively low maintenance product.
Steel is also an engineered product.
It has a place in the world of ships and boats.
There are simply much better materials for construction of a small
sailing vessel than steel.
BTW, about that 5 lb hammer drill exercise.
Anytime you would like to work up a sweat and lose a small, well maybe
not so small wager after all, let me know.
To the potential buyer of a used steel boat, I would caution, unless
professionally built, probably in Holland or maybe you will find a
Manfred Kanter boat which is built in Ontario, Canada, you are probably
buying a "Rust Bucket".
Just my opinion, but then I put my wallet behind it for my own boat.
Lew
S/A: Challenge, The Bullet Proof Boat (Under Construction in the
Southland)
Visit <http://home.earthlink.net/~lewhodgett> for pictures
There are no problems, only varying degrees of challenging opportunity.
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