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Old 17-04-2006, 09:23   #46
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steel

There are the books that tell what strength materials have and then there is bending and breaking after that.If i ever collide with anything i would choose to be on the steel boat.When it comes to durability and that is what keeps you afloat nothing compares.Now for ease of maintanance fiberglass is the deal.I have flattened cars with a 60,000 pound excavator in a scrap yard and you would be hardpressed to poke a hole through them unless you came down on it with the teeth of the bucket.I have a fiberglassed boat ,however ,working around metal all my life it is laughable to compare fiberglass and steel on the same page when it comes to durability.The fiberglass crowd will use these numbers to compete with steel and when you add up the thickness required,they would then argue that you should never build a boat that thick because it would be so heavy,so it should be cored.Then with the cored boat ,take a hammer to it.Go take a hammer to a corvette and then beat on the engine hood of an old caddillac,like i said it is laughable.There are alot of negatives with steel but durability is not one of them.They make the handles of hammers out of fiberglass.
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Old 17-04-2006, 09:57   #47
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As noted, Jeff compared the strengths of equally heavy steel & fibreglass panels, obtaining thicker FRG laminates.
He could have just as easily compared the weights of comparable strength panels, obtaining lighter FRG laminates.
As previously noted, we can choose from a grab-bag of desirable qualities, understanding the reciprocals attending each, including:
~ strength (of several “flavours”)
~ weight
~ maintenance
~ durability
~ engineering (simplicity vs complexity)
~ cost (initial capital & life cycle)

Without doubt, if initial cost were not an issue, I would opt for an exotic hi-tech laminate (or perhaps titanium) that satisfied all of the other requirements, over steel (or Aluminum).
Steel only becomes attractive, when you select strength & initial cost, over all other attributes.

FWIW,
Gord
Who’s owned & operated Wood, Aluminum, and FRG (solid & sandwich) - how can he “dis” steel, w/out personal experience?
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Old 17-04-2006, 20:17   #48
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Steel and stuff

I am surprised that the steel fanciers do not tell us that planes would be stronger if built from steel. Obviously weight would be an issue, but for some it is not an issue with boats. I have a 31 year old 22 foot fiberglass boat outside, it weighs about 2950 pounds. So far I have failed to fathom how it would be any better if it was made from steel and weighed a whole lot more.
Jeff gives us a well reasoned and fair discussion on the subject, and some members want to misquote him and bring in arguments that just do not fit.
Maybe it would be better if at the beginning of the post you qualified yourself by saying " I like steel " and explain why. That would be better than shooting the messenger. It might work fine for your application, it will not work fine for mine. If I change my requirements then steel might work.
Other materials work fine for some folks, while others can ruin anything.
There is a steel boat of about 36 feet in Bamfield and it looks very sad. It is not a good advertisement. It is a poster boat for rust.
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Old 17-04-2006, 21:05   #49
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k

The one thing i said about steel is that it is the most durable by far.People get to excited about strength.A glass is strong,i can stand on it,it has great strength.I can also stand on a soup can that isn`t as strong but do not drop the glass on the concrete floor.I got involved in this discussion when i pictured a fiberglass hammer beating on steel.LOL You can take a sledge hammer to 1 inch plate till you die or take some time and you will beat threw 12 inches of fiberglass.Yes it won`t be easy and you better wear your safty glasses,however,in time you will go through it.That is durability.You can take all the exotic plastic materials that hulls are made from and when they are compressed past their breaking point they do just that,they break.Steel compresses and bends,it gives you warnings of being overstressed,glass does not,you hear the crack and it`s game over.Fiberglass IMO for the average person is the way to go but don`t even consider it near as durable as steel.A half ton truck is a very dangerous vehicle for the driver in accidents but don`t run into one because it will kill you.Durability not strength is steel`s biggest plus.I`m not a fan of anything that is just a fact.
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Old 17-04-2006, 21:49   #50
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Quote:
Originally Posted by BC Mike C
I am surprised that the steel fanciers do not tell us that planes would be stronger if built from steel. Obviously weight would be an issue, but for some it is not an issue with boats.
Well Mike, if it was all about weight alone, then we would still be making planes out of balsa and paper (and we would make boats out of styrofoam). In fact the MIG25 Foxbat was made out of steel. Having 90000 lbs of thrust sort of negates the weight issue and Mach 3 melts aluminium. All building materials have their pros and cons. This thread was started by someone who is interested in building in steel - I don't think I need to state my appreciation of steel before giving an opinion. As much as I respect Jeff's opinions, his argument about strength to weight is misleading - tensile strength is only one factor and as one may make a yacht with 5/8 in steel, one does not make a yacht with 5 inches of red cedar and epoxy. Rather than comparing the materials at equal weight, why not compare at equal strength and tell us how thick that fibreglass or wood would be. Or compare the typical thickness of the various materials if used to build a vessel of a given size then providing the comprarison of actual strength. Not shooting the messenger, but I don't think Jeff's view is entirely fair. Notwithstanding steel's durability (as Dman described it) it also benefits from being a monolithic material with consistent properties and its strength is consistent in all planes. The same can not be said of fibreglass. Certainly smaller boats should not be made in steel, but for a good-sized cruising yacht steel is an excellent material with many advantages, so it's a logical choice for many.

Kevin
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Old 17-04-2006, 22:19   #51
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Books

David Gerr has written The Nature of Boats and a more recent book about the strength of building materials.
I have just gone back and re read the posts. Noticed that I mentioned a site for steel builders early on.
At 53 feet there can be a good argument for steel. But as a do it yourself project it could be challenging, especially for a first time.
I have a basic problem with making a boat too heavy. My fiberglass 28 foot boat is 7400 pounds and that is plenty heavy enough for me. A good boat that size could be 4000 pounds and still be strong. To make it 12000 pounds just does not make any sense to me.
But as has been stated often, as the boats get bigger the weight problem is not such a big deal. I find it distracting to point to other applications like trucks and icebreakers and heavy equipment. I am familiar with those arguments. The owner of Shorelandr trailers wrote an excellent article many years ago explaining why he used steel rather than aluminum. My stock trailer is steel not aluminum because I wanted the strength. But we are talking about boats and they can have some specific requirements.
I have a fiberglass hammer, and a plastic hammer, and a rubber hammer as well as a few steel hammers and they all serve a specific purpose. Do you all want me to install the hubcaps with a steel hammer?
Michael
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Old 17-04-2006, 22:39   #52
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Micheal, with all due respect.

I know in the past posts. You love sailboat racing. And in order to have a good racing sailboat. They have to be light. And since you mentioned in your last post. That you favor a lighter boat. I believe you're not being fair here?

We're not talking about racing sailboats here. But true ocean going sailboats. Not the kind you sail around on a small pond or lake. Like you do?

We're talking true "hardcore" blue water sailboats. And I have read lots into steel boats. And steel being a good medium to build a sailboat with. Since this was my original thread here now!!!

I'm going to use Bruce Roberts, for his steel hull thickness's as an example here.

I have consulted with him personnel in the past. And I asked him what's the normal thickness for his steel boats. He said 5mm or 1/4 in. And that is strong right there. If welded together. Not taking shortcuts. And following the building plans. You should a fairly semi light-heavy sailboat. If you go thicker on the steel plates. You over killing the weight issue.

That's my two cents there!!
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Old 18-04-2006, 10:45   #53
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building in steel

Capt K
I have a good friend who has a Roberts 53 that he built in partnership with several friends. A story in itself. I don't know if this is the same design you are interested in. This one has a midcockpit and the headroom under the cockpit and aft cabins is a headbanger for anyone over 5'10". Something you would not expect in a boat this size. There is another Roberts 53 in the yard that has been in the building stage for the last 15 years with no end in sight.
I will comment on something that has been lightly discussed so far and that is outfitting. The cost of winches, windlass, engine, and spars and rigging for a boat this size is going to require a huge capital outlay. Not to mention sails and all the other hardware, cordage, etc. If you are trying to pinch pennies by sourcing cheap steel for just the hull you have to ask yourself do you have the monetary resources to pull this off? I don't question your dedication for such an undertaking but this is a HUGE project from a monetary outlook.
About an early post about coating plastic with glass and resin. I am not sure why you wanted to do this but with the exeption of PVC, epoxy does not bond well with plastic. I use small plastic containers and bowls to mix epoxy and after several batches it builds up in the container. After it dries all I have to do is flex the container and it pops loose sometimes even in one piece so I have a nice little epoxy bowl.
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Old 18-04-2006, 11:21   #54
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It always amazes me that this topic seems to result in a very intensive discussion almost anytime it appears. Let me see if I can touch on the points raised since my last post.


To start with, Dman is right, there are books that provide the data and procedures for calculating the relative strength of the materials in question, steel, wood, and composites. I used those books to generate the numbers that I quoted. I have previously posted on the Origami site a detailed analysis that provided the sources of the numbers and formulas that I used to produce the relative impact and bending strength of the materials in question that I quoted above.


These are not just theoretical numbers. They derive from actual testing and have been supported in experimental data as well as mathematical projections. In prior discussions, I have referred to a US Naval Academy study of impact strength relative to weight. In this study actual hull panels were constructed and a heavy battering ram with a sharp point (shaped like the bow of a Naval Academy 44) was released into panel, and the damage noted. On a pound for pound basis the winner was a vinylester/glass panel which was the only panel that withstood the impact without being breeched.


As has been noted, not all fiberglass is created equally. This panel was specifically designed for impact and bending strength. The resin used is the same vinylester popularized in crash and military helmets. The core was specifically chosen for its energy absorbing ability. The laminate used absolutely no non-directional materials. It was also the least expensive of the panels tested.


Then there is the durability issue. In the late 1970's and early 1980's I was a big fan of steel construction. In the early 1980's when I worked for Charlie Whitholz, I worked on the design of a number of steel hulled boats. A few years back, I had a chance to look at one of these boats that was then about 20 years old. Much of the bottom plating had already been replaced several years earlier. I had the chance to examine the plates that were not replaced. Even with the heavy coating of zinc rich coal tar epoxy that was applied when the boat was new, the sheer amount of rust was astonishing. In continuous but localized areas near the longitudinal frames, the 5/16" plating was reduced to less than an 1/8". This is way too light for an over 50 foot offshore power yacht, especially when located at one of the highest stress areas of the hull. After seeing the extent of corrosion on this boat I sought out several steel boats of that same era and found similar levels of corrosion damage.


One often ignored advantage of steel is that it nearly eternally re-buildable. In other words steel does have the advantage that it is pretty easy to replace bad panels or even framing. But that comes at the price that it is a very high maintenance material when viewed over a long life cycle.


To answer the question regarding the relative thickness of fiberglass vs wood vs. steel of equal strength. For the sake of comparison, if we use impact resistance as the controlling factor and assume a steel hull plate 5/16" thick, a comparable impact resistant composite hull would be roughly 1" thick and roughly a third of the weight of the steel hull, and a cold molded hull, would be roughly 1 3/8" to 1 1/2" thick and roughly half the weight of a steel hull. For what it is worth these are fairly normal scantlings for a 50 or so foot offshore sailboat. (Captain K: 1/4” plate is actually a little on the light side for a 52 footer unless you use very closely spaced frames, which comes at the price of greatly increasing build time and paradoxically can increase the likelihood of being holed, but would conversely tend to limit the extent of the damage in such a situation.)


Lastly to the issue of weight and prejudice…I come to these discussions with the hope of being able to provide clear and accurate data on the relative strengths of these materials rather than some intuitive sense of their relative strengths. Anyone who has ever held a piece of 1/4” steel plate in their hand could not help but be impressed with how seemingly indestructible this material would appear to be. Anyone who has ever worked on a poorly built fiberglass boat, will also come away with an intuitive sense of the potential vulnerability of fiberglass. But the reality of situation, is that when compared on a pound for pound basis, using accepted engineering data, steel just does not do all that well against properly designed and properly build composite or cold molded boats. While I gladly admit that I strongly prefer lighter weight boats and better sailing boats for my own use than can typically produced in steel, that still does not change the realities of the materials in question.


And one last point before lunch hour ends, There seems to be an assumption that excess weight is not problem in a cruising boat, but excess hull weight is actually more of a problem in a cruising boat than a racer. In an of itself weight does not give a boat more strength, more seaworthiness, a more comfortable motion or more carrying capacity. When excess weight comes in the form of excess hull weight, it robs a cruising boat of some combination of stability, roll comfort, carrying capacity, fuel economy, seaworthiness, and performance.

If a race boat is over weight it merely robs the crew of a win. If a cruising boat is over weight it can make the cost to build and operate excessive and more importantly make the lives of the crew miserable, and put their lives unnecessarily at risk.


Respectfully,
Jeff
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Old 18-04-2006, 13:52   #55
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steel

It's always entertaining to hear someone make a total fool out of himself by proclaiming that something which hhas worked well for decades "Won't work"
My current boat is 22 years old, yet the paint is mostly as good as the day I put it on. Ditto for boats I've built 25 years ago.
Steel 36 footers I've designed have beaten 35 ft Beneteaus, and C&Cs going to windward in 12 knots of wind , and I was aboard one of my 36 footers when it outsailed a Cooper 42 going to windward in 12 knots of wind. So when someone says that which has already happened time and time again, doesn't happen,they are making complete fools out of themselves.Its like telling an astronaut stepping down from a returning space shuttle "The world is flat , you know."
When numerical theories don't aggree with practical ,real life experiences, then I prefer to stake my safety and thus my life on reality.
While collisions with one of the tens of thousands of cargo containers floating around ,will sink a non metal boat, they are unlikely to be any more than an inconvenience to a well built metal yacht.Ditto whales.
When Jeff talks about steel boats rusting out in 20 years , he is either talking about boats that were not properly painted inside and out, or he is lying.
Another benefit of steel construction is that it lets you use the best bedding compound ever invented to attach fittings, welding.Deck leaks then become unheard of under welded on fittings. leaks under fittings on fibreglass decks are extremely common.
The ability to use scrap for all the fittings ,which would cost an arm and a leg on a fibreglass boat makes the steel a much bigger part of the total cost of the boat. The steel for my 31 footer cost $3500. To get her sailing cost me a total of $6,000. The steel was over 50% of the cost of getting her sailing.Things like anchors , becomming increasingly expensive , can be made from hull scraps for pennies .Ditto a lot of other fittings which would be extremely expensive. Stainless cleats cost me a dollar a pound, cleats which would cost $40 each if bought for a fibreglass boat. My stainless anchor winch cost me $1 a pound , plus discs and welding rod.My stainless heating stove cost me$1 a pound plus rod and discs.Ditto my stainless tanks, stovepipe, handrails, exhuast, mooring bits,hatch hinges,bow roller, thru hulls,lifelines , pulpit, pushpit,boarding ladder, etc etc.. Mast fittings cost me 50 cents a pound. Enough rigging for a 36 footer cost $28.
Despite a huge number of very successful steel boats down to 26 feet in length , roughly 150 of my design , many outsailing similar sized fibreglass boats of the same size on all points of sail ,some doing successful circumnavigations , all with excellent passage times,David Gerr says that such boats, which have worked very well for many decades , won't work. Do they suddenly stop working the moment that Gerr makes his pronouncement? Or does Gerr's crediblity sudenly stop working? I would assume the latter, but its clear that to make such an assumption gives too much credit to human intelligence ,which simply isn't there in so many people.Ditto Jeff.
I saw some incredibly foolish comments made by Gerr in Sail magazine a while ago. I wrote a letter to them refuting the claims, but they didn't publish it.
In Jimmy Cornell's book "Modern Ocean Cruising" he interviews 10 circumnavigators. 9 said they would prefer a metal boat and several had already started new metal boats. Fibreglass is the first choice of the beginner. The more experience a cruiser has the more interest he tends to have in metal boats. Sailing on a dark foggy night , thinking about all the stuff floating out there that one could easily collide with and sink quickly , and thinking about what the chances are of your choice of hull material surviveing such a collision , gives one a clear appreciation of steel. Especially if one has kids aboard. One of my clients , who had cruised extensively in a fibreglass hull before I built him a steel one said that the difference in peace of mind while doing hull speed on a dark night was huge.People doing mathemeatical calculations in the comfort of their living room have trouble grasping the concept. A steel hill is extremely unlikely to even suffer minimal dammage when colliding with a cargo container,
. A stock fibreglass hull is extremely unlikely to survive such a collision.
Brent
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Old 18-04-2006, 13:58   #56
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Jeff, I think your replies are excellent and full of very good factual info. Thank-you for taking the time to reply. Even though you seem to always be against the flow, I do hope you realise that you are being listened to.

I would like to also stregthen Jeff's comment about what makes a boat good for cruising and racing. It is not weight, but essentially the design for the task.

Jeff, I think the essential point of peoples concerns however, is that perception of wall thickness of a panel, when compared to "weight for weight". When into hull sizes of 50ft and more, we are seeing a more equal playing feild in a laminate thickness, compared toa steel thickness. But what about bringing the argument down to say a 30ft hull range. A range where the playing feild is not so equal anymore. Can you explain if there are important design factors in weight for weight and laminate thicknesses in that size range. What I mean by this, is that I think many are thinking that it is reduculouse to have a laminate of 1" think in a 30ft boat. and I think that is where the arguments are coming in.
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Old 18-04-2006, 14:05   #57
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My hulls are between 1/8th inch and 3/16th inch plate. My current 31 footer is 12,000 lbs empty. Go find yourself a 12,000 lb fibreglass hull and we'll have our demolition derby.
I once worked on a tug that was built in 1947 and has been working ever since. So much for short life. Most short life problems are caused by zero paint , other than a quick coat of cheap stuff and zero maintenance on workboats, not even the hour or two a year I spend.
A friend gave me a good comment on older wooden boats . He said "It's like this axe that I've inherited . It's the same axe that my great grandfather used. Since then it's had 5 new heads and 12 new handles."
Weight? My boats are roughly in the same weight category as other similar cruising boats made out of fibreglass. When they are making good passage times and outsailing fibreglass boats, where's the penalty. Having to go into debt to build a fibreglass boat out of super expensive materials , delays your departure time by far more time than you would ever make up by any theoretical improvement in speed when you eventually do get under way( if you ever do)
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Old 18-04-2006, 14:06   #58
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Polarlized viewpoints this here thread, ain't it!

I wonder if I dangle the view point of us FC owners into here, that I still believe a well built FC boat is better than any material out there. Will I get my hand bitten off???
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Old 18-04-2006, 14:13   #59
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Alan, may get your head bitten completely off here?

And maybe not?
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Old 18-04-2006, 18:57   #60
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y

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A friend gave me a good comment on older wooden boats . He said "It's like this axe that I've inherited . It's the same axe that my great grandfather used. Since then it's had 5 new heads and 12 new handles."
Now that is funny!I think were the fiberglass boat appeals to most is that we are weekend warriors.We seldom venture(if ever) offshore and we are in constant radio contact for help.Most people have never been in the situation where they are truely alone out there.I see boats that sit anchored for months,some people got to work for a living.Where steel is appealing is to serious offshore vessels,unlike most boats that are being used by the majority.We will redo our water soaked decks and buff our gelcoats ,they just look nicer for the most part. I just know that steel rules when it comes to taking impact and when you are out there that means alot.You do not have to read books to know what will take impact better,go whack a maple tree for a few hours with a sledge ,then go crack some fiberglass.
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