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Old 27-03-2012, 19:05   #16
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Join Date: Aug 2006
Location: Brisbane Australia [until the boats launched]
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Re: building with kevlar

Originally Posted by minaret View Post
Note that the laminate schedule for the teeny canoe linked to above is three times thicker than you claim they are skinning 3/4" inch thick foam hulls with! More actually as it calls for 3 plies of 6 oz. instead of one ply of 5 oz.
Claim? No claim champ, it is a fact.
I didn't look at the link but so what?
I'd never go to sea to cruise in a boat with fiberglass less than 1/16" thick, that's madness!
Thats your call probably bought on by ignorance of structure strength.
My last cat had a massive box beam holding it together.
The designer told me that a beam about 1/4 of the size was more than sufficient but it would put people off it as it "Appeared" to be not strong enough.
The reality of it is that it was.
Fine for racing but what happens when you beach the boat or run aground or hit something, which as we all know is fairly inevitable for most serious cruisers?

All of these vessels regularly beach and on occasion have run aground and hit things.
Hit the bricks at 14 knots and you have damage regardless.
What I can tell you is its possible for the lighter boat to sustain less damage as it doesn't have the weight to carry it on.
I say this with experience having clipped a reef doing 14 knots driving that hull (dagger board down) up onto a bombie and sustaining minimal damage to the board and next to nothing to the hull.
If I had a heavier boat with all that weight and momentum carrying me forward I doubt I would have been as lucky.

As for serious cruiser, the second picture has been cruising through Asia as a full time live a board for the last 10 years managing just fine, discounting your "theory"
Laminate schedules that light in a structure that undergoes the stresses a catamaran does just cannot possibly have the same longevity as a serious cruising design.
And yet they have been out there being flogged harder than an average cruiser ever would and doing it for over 25 years.
I don't think you can compare these designs to a normal production cruising cat in any way, as I've told you before.
Of course you cant, what production builder uses kevlar epoxy?
And where was the comparison made between production boats anyway?

You can find all sorts of extremes to make your point but it doesnt really help the discussion any.
Extreme to some but relatively normal to others.
The OP is after a kevlar build so your "production" comparisons lend little weight to the discussion

Show me a production cruising cat with ONLY kevlar in the laminate, I challenge you!
Why are you harping on production again, it's obvious the OP will not be wanting a production build, he's using Kevlar FFS

Even the examples you already mentioned have as much glass in that single biax than in the kevlar skins, making it a 50/50 mix as I already suggested,
again, so what.

and I'm sure they were the most extreme examples you could find!
You are kidding right?
These are old boats, I'm sure I could find something more exotic and possibly lighter if I tried.

Minaret, the fact that someone may have more knowledge about a subject than you do really seems to get you upset.

I suggest you get over it.

"Money can't buy you happiness but it can buy you a yacht large enough to pull up right alongside it"...............David Lee Roth
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Old 28-08-2012, 07:37   #17
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20 years ago I was getting my masters degree in materials science. Back then Kevlar was the highest strength to weight ratio of any material, including carbon. But not good in compression. That is so cool you got enough to build a boat. I think it is just a question of finding the right design / designer to work with. I would check with Shuttleworth, Hughes, schionning, maybe Grainger.

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