Pros and cons of steel sailboats - Page 158 - SailNet Community
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post #1571 of 5317 Old 10-09-2013
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Re: Pros and cons of steel sailboats

Denda:
Thanks. Right now I'm like a guy running around showing his hot new girlfriend off.

As of half an hour ago we now have six boats spoken for.
POPEYE
BLUTO
OLIVE OIL
SWEET PEA
are names already taken.
WIMPY is still available.

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Last edited by bobperry; 10-09-2013 at 04:57 PM.
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post #1572 of 5317 Old 10-09-2013
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Re: Pros and cons of steel sailboats

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Originally Posted by bobperry View Post
BLIMPY is still available.

....wasn't that "Wimpy"????

Ron

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".. there is much you could do at sea with common sense.. and very little you could do without it.."
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Re: Pros and cons of steel sailboats

Blimpy should be reserved for the extreme girth wrapped around the pramish bow.A gentleman should be able to stand while pulling a prawn trap.be glad to pay you on Tuesday.
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post #1574 of 5317 Old 10-09-2013
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Re: Pros and cons of steel sailboats

Yeah, fixed that. It was WIMPY and it's also OLIVE OYL.

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post #1575 of 5317 Old 10-09-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Classic30 View Post
Thankfully.. All you need is a Fein, boat nails and another piece of wood.

I can't think of anything in boat-repair much more difficult than patching a hole with plate steel. It looks simple enough to an onlooker, but I've seen even professional welders (cheap ones, I might add) stuff it up totally by not allowing for weld stress and heating.


EDIT: Thinking about this, in theory you might be able to cut wood with a plasma cutter. Dunno.. I'm not silly enough to try it. It's always easier to use the right tools for the job at hand.
Use rounded corners on any patches. Weld the rounded corners last . The rest, weld an inch, let it cool, then weld another inch , etc. This lets the welds cool, and shrink as far as they are going to, before closing the circle.

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post #1576 of 5317 Old 10-09-2013
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Re: Pros and cons of steel sailboats

When comparing metal with other materials, one should bear in mind that only metal has the same tensile strength in all directions. Douglas fir has a tensile strength along the grain only. Across the grain it is very weak. With planked boats ,that means the planking has strength longitudinally only. The frames give the transverse strength, usually much weaker. That is what transverse frames were invented for, a material which has strength in one direction only. It has very little diagonal strength, which is why Herreschoff used diagonal bronze strapping, to prevent diagonal movement, called hogging and sagging.

Cold molded?
At best, a tripe laminated cold molded hull only has about a third of its planking in any one direction. Whichever direction you load it, only a third of the wood in it has any tensile strength in that direction, the rest of the load is across the grain of the other laminations. So for a tensile strength of 1500 PSI for fir, a cold molded fir hull will have a third of that strength in any one direction.
Fibreglass?
Roving has half its fibres in one direction and half in the other. So the best you can hope for is roughly half the maximum tensile strength of a fibreglass hull, in any one direction.
Diagonal strength? Matt?
In a random jumble of logs, there is very little wood and mostly air space. Similarly, in the random jumble of fibres which is fibreglass matt the thickness of the matt is only a tiny percentage glass fibres ( strength )and a huge percentage resin, which has very little strength. As roving is very rarely run diagonally, there is very little diagonal strength in most fibreglass hulls, which is why it is so easy to sag them with a hydraulic backstay adjuster. You will never get the ultimate tensile strength of fibreglass in any hull layup, for these reasons.
You can see this in old fibreglass SSB antenas. Unidirectional layup makes them strong, longitudinally, but weak transversely ,where you can twist them apart by hand, if you cut the metal end off one.

Steel however, has 60,000 psi tensile strength in all directions, period.

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"

Last edited by Brent Swain; 10-09-2013 at 07:05 PM.
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post #1577 of 5317 Old 10-09-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Brent Swain View Post
Use rounded corners on any patches. Weld the rounded corners last . The rest, weld an inch, let it cool, then weld another inch , etc. This lets the welds cool, and shrink as far as they are going to, before closing the circle.
Quite true, Brent. .. and bevel the edges of the patch first also.

I guess my point is that it's hardly a trivial exercise.

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Re: Pros and cons of steel sailboats

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I think that you and I are trying to say roughly the same thing. I was saying it in the negative by pointing out that in and of itself, increasing the displacement of a boat does it automatically add to carrying capacity.

You are pointing out in the positive, a heavier boat does not have greater carrying capacity if that added weight is in the form of a heavy hull and deck structure.

Jeff
In a heavier boat, the percentage of increase in her displacement, by adding a given weight of personal effects and stores, will be less than it would be in a lighter boat, and the heavier designed boat will be floating much closer to her original weight. The percentage of change will be far less in a heavier design.

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"

Last edited by Brent Swain; 10-11-2013 at 07:22 PM.
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post #1579 of 5317 Old 10-09-2013
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Re: Pros and cons of steel sailboats

GRP boats in all their iterations are here to stay until something better comes along. It won't be steel.

Just a reminder, again, this Nordic 40 just completed a solo circumnavigation. Remarkably it is still in one piece. The owner is very happy with the boat. It's a great looking boat.

Brent's constant whining that our GRP boats are not up to the job can be proven wrong over and over just with my own designs. Lighten up Brent. You like steel boats and some people don't. What's wrong with that?
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bfloyd4445 View Post
whew, Bob speaks well for steel but he is forgetting that one could make a car with four inch Armour plate then drive letting others just bounce off but the price paid in energy expended to move all that extra weight is more than most of us wish to bear no matter what our income. Not a matter of what one can afford as what's best for the world and future generations. When I don't fly, boat, I drive a vw Golf TDI, the prius eater, only because I have little desire to squander non renewable resources. The fact is for small craft steel requires just too much energy to move from point a to b. Basic engineering.
I'm sure you engineering types can grasp the concept
That said I love steel boats, they are realistically just not cost effective under 50 feet
When the wind is free and environmentally sustainable, what is the problem?
With my tiny income, a months wages a year on average, for the last 37 years in my 29 ft and 31 ft steel sailboats , including building the latter, what is not cost effective about that?

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