Pros and cons of steel sailboats - Page 39 - SailNet Community
Old 08-05-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bobperry View Post
The Fred Flintstone school of yacht design.

I know it's done but even as a 15 year old kid I figured that balancing shapes on a, I used my triangular scale, was BS. It was just not precise. I use a calculus method with Simpson's multipliers. It takes a bit of time but the results are reliable
Far more precise than your assumptions that you can predict what very different owners will put aboard, over decades of living aboard. That assumption is incredibly naïve. The variations in those numbers are far larger than any variations in balancing a curve of areas, model , etc. in fact huge. Herreshoff had a lot to say, none of it complementary, about the foolishness of mathematicians over the logic of practical people . He also had a good laugh about the irrelevance, and goofiness of Simpsons multipliers, over Hereshoffs own much simpler methods.
He well describes the motives of such advocates as "Exhibitionists."
Most experienced offshore cruisers come back saying "Keep it simple" not saying "Make it more complicated."
A good example is the naïve mathematical calculations that one should put a plywood deck on a steel boat. The numbers look great , and the numbers wont tell you anything about the kind of maintenance nightmare it will result in. They wont tell you that plywood is impossible to properly insulate without introducing a high risk of dry rot, or that in cold weather the plywood will be covered in ice, inside. They wont tell you that deck hardware bolted down, instead of welded down, will leak, and pull loose a lot more, as the plywood swells and shrinks against metal, which wont, inevitably pulling any bedding compound apart.
As the hull deck joint takes most of the twisting load of the boat ,huge loads, responsible for so many hull- deck joint problems in fibreglass boats, bolts will inevitably work loose in the wettest part of the deck structure, drastically weakening it. It is the worst place on the boat for changing materials, something your calculations wont tell you. Only experience will do that.
Changing the transition to the inside edge of the deck, makes it far less structurally important, but still a bit wet, and prone to dry rot and leaks. Had leaks there in my cement boat , no fun.
As cabin sides are not all that heavy, especially when you cut ports in them, the top of the cabin side would be a far better place for any transition, something your math calculations wont tell you.
I replaced the plywood cabin top on a Colvin gazelle with aluminium, which was far lighter, and a material you could spray foam over and insulate properly, without fear of dry rot. Worked out well.
Don't expect those who believe their calculations can tell them everything they need to know about boats, with no real hands on practical experience, without living aboard in different climates, and cruising in their products over many decades, to comprehend such practical matters . Now that would be naïve!

Bob, a friend just bought one of your boats . Nice looking boat. Could you explain the logic in stanchions so short, that all they can hope to accomplish is to make sure you hit the water head first instead if feet first? If "yachtiness" prevails , they will have on high visibility yellow boots, to maker sure you can see their feet, when they are up to their necks in murky water.
How very yotty!

Last edited by Brent Swain; 08-05-2013 at 06:52 PM.
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Old 08-05-2013
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Re: Pros and cons of steel sailboats

Sabots, Lido 14's, El Toros, Optimists. Oh yeah, all the racing boats.

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Old 08-05-2013
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Re: Pros and cons of steel sailboats

BS:
I agree with you on that. I can't see anything but problems bolting a PW deck to steel.

But the difference is that L. Francis COULD do the math when he needed to. He just believed that the math had to be balanced with experience. I would certainly agree with that. Can't imagine I know any succesful designer who doesn't think that.

I have another question for you. I was never comfortable spraying fowm inside the shell. IIt scares me that I can never se that part of the shell again. I'd worry what was happening under the foam. Hoiw do you deal with that?

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Old 08-05-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bobperry View Post
BS:
I agree with you on that. I can't see anything but problems bolting a PW deck to steel.

But the difference is that L. Francis COULD do the math when he needed to. He just believed that the math had to be balanced with experience. I would certainly agree with that. Can't imagine I know any succesful designer who doesn't think that.

I have another question for you. I was never comfortable spraying fowm inside the shell. IIt scares me that I can never se that part of the shell again. I'd worry what was happening under the foam. Hoiw do you deal with that?
Many coats of epoxy tar or wasser tar. I once salvaged some galv pipe out of an old building. the side facing SE against the prevailing rainy weather was severely rusted; the side facing the NW and dry winds looked almost new. Inside a steel hull it doesn't take a lot to tip the balance, but given paint is cheap and you don't get a second chance, why not give it an overkill on thickness. Most of the boats built by Foulkes and Fehr have zero paint on the inside, and predictable results, with severe inside rusting. Any time you see rust on a flat surface on the outside of a steel boat, the paint was never thick enough. Moitessier makes this point in pointing out how many coats the French navy insists on before launching. Many! No such thing as too thick, the thicker the better. If you can still see the weld pattern ,it is not thick enough. Too thin a paint job is the main reason for steel boat owners having maintenance problems ( along with wood over steel on the outside).
On older boats, you can tell how well the foam has stuck to the steel, and any other problems under the foam, by dragging your fingernails over it. Where it has separated from the steel, you can hear a distinct hollow sound. That is where you should dig it out and have a look. If you see smooth ,clean epoxy, the rest is probably the same.

I use Hereshoff's methods of calculation, with models as double checks. The results, decades of successful boats, with some owners on their third, as testimony.

Last edited by Brent Swain; 08-05-2013 at 07:11 PM.
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Re: Pros and cons of steel sailboats

Rueters:August 5th 2013,Dubai UAE
Nigel Irens announces his next record breaking trimaran will be built of steel according to the origami method. A stunned Francis Joyan remarked "I thought we were doing ok with IDEC,I am not sure about this new direction".When asked by reporters if steel was the right choice Irens errupted " Its just better! %\$#%^#& dis informers and there ^&%*\$\$ idiotic campaigns against forward thinking building methods."Ive been wrong all along" he shouted."Carbon, kevlar,E-glass,its all garbage".Irens then started banging his head on the podium screaming steel!,steel, STEEL! before leaping bodily into the crowd of reporters.He was taking to a near by hospital for observation.
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Re: Pros and cons of steel sailboats

Models? Really. I have 60 of them in my office. I have models coming out my ears. If you look closely over the left should of Erica, holding Bram, you can see the walls of the head are also covered in models. I like them.
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Last edited by bobperry; 08-05-2013 at 07:19 PM.
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by mark2gmtrans View Post
You are 100% correct in your assertion that there is no way to visually inspect a steel hull and certify it as to its integrity. When I had the oil field pipe business we had a machine that cost well over a million dollars that was one of the only ways to inspect steel pipe correctly. This machine is called an EMI and is basically an MRI for pipe, it uses several large magnetic coils to generate a field which can "see" through the pipe and detect microscopic defects and flaws in the pipe. This inspection is done on almost all oilfield casing and tubing, in an effort to prevent "blowouts" and reveals the flaws in the pipe. It does a great job, however there is not a good way to run an EMI on a hull, you cannot see the microfractures that come from stress on the material.

There are surveyors who use ultrasound to do hull inspections on steel boats. This is the only way to really get a good idea of the hull integrity, and it is costly. If you are purchasing a used mega-yacht the cost is not prohibitive, if you are purchasing a used sailboat under 40 feet it may be more than most would be willing to spend on a survey, and it takes up to two days to do it. There are not many people here in the states who can do an ultrasound hull survey, so that makes it even more fun.

The stress of an impact on the keel seam of a vessel weighing in at somewhere around 30,000 pounds is going to so far exceed the tensile strength of the material at the point of impact as to be able to cause incredible damage and still not be visible. The damage will be done at the molecular level, and this is something you cannot see or inspect on a survey, but it sure can come back to haunt you.

BS said that the steel he used had some huge million plus pound tensile strength, that is not true. I do not know how anyone can state that and even expect us to believe it, because there is not a single type of steel with a tensile strength that high. This is not an assumption, it is a fact.

If you use A36 steel, 3/16" thickness you have an estimated tensile strength of 36,000 pounds, that is what the 36 represents. Layering it to four layers does not increase the tensile strength at all, it does raise the amount of force needed to penetrate the hull, but not to 1,800,000 psi times four, as asserted by BS. I have no idea how BS came up with that number for tensile strength, but unless he can show me a metallurgical test for the specific hull plating used that gives a tensile strength of 1,800,000 psi I am going to have to say he has had a mathematical error somewhere in his calculations.

To start with 3/16" is too thin for a hull, especially at the keel, I would think that the keel would want to be done in about 3/4 inch steel plate, which is more like what BS is talking about with his four layers of 3/16 inch steel. The thing is that layering is good, but you still only get 36,000 psi you just get four layers of it. I have not done the math yet, but if you have a boat that weighs 36,000 pounds, which would not be at all out of line with a steel boat, I am guessing that when you factor in the speed and angle of the impact you get a good deal more than 36,000 psi, so the best thing to do with a steel hull remains the same as with any other hull....don't hit stuff. Now if Brent has some 1.8 million psi 3/16 inch steel somewhere he needs to start building pressure vessels and tanks with it, and maybe the military might like to have some too.

A36 is a standard low carbon steel, without advanced alloying.
As with most steels, A36 has a density of 7,800 kg/m3 (0.28 lb/cu in). Young's modulus for A36 steel is 200 GPa (29,000,000 psi).[2] A36 steel has a Poisson's ratio of 0.260, and a shear modulus of 79.3 GPa (11,500,000 psi).
A36 steel in plates, bars, and shapes with a thickness of less than 8 in (203 mm) has a minimum yield strength of 36,000 psi (250 MPa) and ultimate tensile strength of 58,000–80,000 psi (400–550 MPa). Plates thicker than 8 in have a 32,000 psi (220 MPa) yield strength and the same ultimate tensile strength.[1]
A36 bars and shapes maintain their ultimate strength up to 650°F. Afterward, the minimum strength drops off from 58,000 psi: 54,000 psi at 700°F; 45,000 psi at 750°F; 37,000 psi at 800°F. A36 steel has low carbon, that produce high strength to the alloy

Tensile strength and shear strength are not the same thing, and not only that, an impact exerts both tensile (pulling) and shear (cutting or tearing) forces on the point of impact and combined they will poke a hole in your boat. The hardness of the object impacted, the speed of the impact, the weight of the impacting object, and the angle of the impact along with some other factors are what determine the ultimate force of the impact, but steel, wood, concrete, fiberglass or a combination of all the above will not be enough to stop a sea container that fell off a ship from knocking a great big gaping sink your boat hole in the hull of a sailboat if you hit it at the right angle. Sailing a boat is not something that can ever be made 100% safe, there are risks involved, but the rewards far outweigh the risks, if I die while sailing I will have died doing something I enjoyed. If I die while sailing on a steel boat or a wooden boat I will still be dead.
Mild steel is 60,000 PSI tensile and compression strength . That is 11250 per linear inch for 3/16th plate. Multiply that by the 96 inches in the side of one of my twin keels. That is 1.08 million pounds per side, times four keels sides.
How are you going to break that with a boat under 20,000 lbs?
Just saw two navy 100 footers in Heroit bay. 3/16th hull plate on 100 ft navy ships . And you say the same plate thickness is too light for a 36 foot pleasure boat? You say that a boat which could survive 16 days pounding in 8 to 12 ft surf on the west coast of the Baja, or pounding across 300 yards of Fijian coral reef in big surf, or colliding with a freighter, or hitting the sharp corner of a sunken barge at hull speed, all with minimal damage, is not strong enough? Now that's a stretch!
My hulls are all single thickness, 1/8th for the decks cabin, etc, 3/16th for the hull ,1/4 for the keel sides, and half inch for the keel bottom ( with 4500 lbs of lead ballast poured on top)
Layering steel is a big mistake, guaranteeing corrosion between the layers unless totally sealed.

A good whack with a sledge hammer and a centre punch on lower parts of keels, etc, where corrosion is most likely, is a good starting point on buying a steel boat. If it doesn't give, you have enough thickness there.
Structural failures of steel boats under 40 feet are extremely rare. Your "Invisible " fractures have zero chance of ever causing any problems in steel boats under 40 feet in their lifetimes.
How does such "invisibly fractured" steel compare in strength to a copper fastening in red cedar every six inches, or six inches of plastic?

Last edited by Brent Swain; 08-05-2013 at 07:37 PM.
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Re: Pros and cons of steel sailboats

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Originally Posted by smackdaddy View Post
Brent, that's awesome. It really is very impressive.

But it has absolutely no bearing on what it will take a green boat building dreamer to get it done after they've bought your plans. You've already said you've worked with steel all your life. So, for your boats to make any sense for anyone, that person needs to have years of experience working with steel (and many other systems).

Your boats are not for the 99% - period. They are for the 1%.

Nothing wrong with that at all. It's just the way it is.
The green, first time boatbuilder will get sailing a lot faster using my methods, than he ever will using any other methods, for a fraction the cost. That has been well proven, time and time again.
I have never built a boat for anyone in the top 1% of income earners, but have built most for people in the bottom end of the income scale, people who could never have afforded a good steel boat any other way.

Last edited by Brent Swain; 08-05-2013 at 07:45 PM.
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Re: Pros and cons of steel sailboats

Thanks for the foam coating and paint info BS. I'm still a bit dubious as I can't see running my fingernail over the entire inside of the coated hull. But I get your drift. How much experience have you had with the foam separating from the inside of the shell? Is it common? Uncommon?

You don't have to worry about me using this info to compete with you. I'm just curious and I like to learn. I am convinced we will never compete for the same client. I have zero against steel boats. It' just not a material I chose to work with at this point. But my clients don' ask for steel boats and they most assuredly do not even remotely consider building at home.

Case in point:
See that photo of my office with Erica, holding Bram? If you look behind the lovely Erica you will see a yellow model standing on end. That was one of two tank test models we built to test a 42' powerboat design of mine. Each model cost \$9,000. Cost of two days of tank testing was about \$30,000 not counting my considerable time. We do not fish for the same same fish. Tank testing is a blast; grown men playing with model boats hooked up to computers. You would be uncomfortable Brent. There's lost of numbers involved. You can learn a lot by watching and have long print outs to verify what you see. Secretly I would bet a bottle of Glenmorangie that you would get a kick out of tank testing. Hell, I'd bet three bottles.

You know BS, in that repsonse to Mark I think you had better take another look at your math. You are getting a little creative.

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Last edited by bobperry; 08-05-2013 at 08:26 PM.
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Re: Pros and cons of steel sailboats

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Originally Posted by Brent Swain View Post

Bob, a friend just bought one of your boats .

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