The pro's and cons of steel boat building

[JumbleDuck]

The models used at Glasgow University testing tank (and I assume others) used to have sand grains applied over an area of the bow to try and introduce a scaled roughness that one could not get on the model alone, or something like that.

Absolutely ... but it's not a "law". In fact the only results I get from googling "law of mechanical similitude" are from boating publications, so it looks as if it may be a myth which has established itself in that world.

 

[SlowlyButSurely]

I too googled it but was a little intimidated by the results so could you please explain in simple terms how mechanical similitude might or might not have a bearing on the example of the Titanic sinking vs a yacht on a coral reef?
TIA.

 

[PeteCooper]

I am puzzled - some would say that's my perpetual state.
There are a lot more people cruising the world in GRP boats than steel.
Steel boats regularly bounce off reefs/rocks/hiabs.
If the same percentage of GRP boats were bouncing off the same stuff then surely we would be hearing of deaths, families, clans and small countries being wiped out on a regular basis?

 

[JumbleDuck]

I too googled it but was a little intimidated by the results so could you please explain in simple terms how mechanical similitude might or might not have a bearing on the example of the Titanic sinking vs a yacht on a coral reef?
TIA.

I'd be interested in the answer too.

 

[newtothis]

I am puzzled - some would say that's my perpetual state.
There are a lot more people cruising the world in GRP boats than steel.
Steel boats regularly bounce off reefs/rocks/hiabs.
If the same percentage of GRP boats were bouncing off the same stuff then surely we would be hearing of deaths, families, clans and small countries being wiped out on a regular basis?

Well that's exactly the response I'd expect from a marina dwelling, plastic toy sailing, pampered salary slave. You don't understand that when the thousands of plastic tubs that sink in the middle of vast oceans each year disappear no one ever knows because the boat has sunk. Their friends and family never know. When they don't show up after a few years, they just assume they're still sailing or were abducted by aliens so there will never be any reports. Those that do get suspicious are paid off by the dark forces of 'big sailing', whose sole aim is to kill its customers.
There are small villages over the world that have been left abandoned after their residents were swallowed by whales or their bath toys were shredded by coral and containers. But do you ever hear about it? No, and that's all the proof you need.
(Trying to use logic with BS usually leads to BS.)

 

[Daydream believer]

There is a lot of talk about GRP boats being left in marinas. But there are an awful lot of marinas with an abandoned rusting steel yacht in one corner or another. many of them look highly undesirable even if one tries to imagine them in their new state, let alone their current state. Perhaps that is why they are there- destroyed dreams, chasing ridiculous stories of sailing the seas & navigating coral reefs
Considering the ratio of GRP to steel I would expect that the failure or abandonment ratio is probably just as high as that of GRP

 

[DownWest]

The rate of abandonment is different. people abandon GRP because of the systems and rig problems, while steel owners do it because of the hull.
And both do it because of money (lack of) apart from the broken dreams and soured relationships.
I could be wrong here, it has happened ;o)

 

[newtothis]

I could be wrong here, it has happened ;o)

Well that rules you out as an evangelist for steel boats then.

 

[DownWest]

Well that rules you out as an evangelist for steel boats then.

Damn, I was hoping for a new career and a plentiful supply of nubile young ladies to keep me happy.
Back to building a boat in the shed...

 

[JumbleDuck]

I like origami boats.

 

[Brent Swain]

That makes you non normal. Can you imagine what the world would be like if everybody behaved in the same way as you?

There is nothing virtuous or commendable about what you have done - in fact the words selfish and egotistical come to mind.

Your suggestion being, we should all unselfishly live life styles which would require several more planets to sustain, and that we are morally obliged to live lifestyles which will destroy the one we have for future generations. It seems the staunchest priests of the puritan work ethic are those who do very
little hands on work themselves, but have others working for them .It is really nothing more than the "worship of blind ,obsessive greed" ethic.
Can you imagine what the world would be like if everyone behaved the same way you do, all 7 billion tried living in your home ,parked their car in your driveway ,wanted only to work at your job, sail in your boat? Wouldn't work, so you should feel guilty about your lifestyle? Shows what stupid argument that one is.

 

[Brent Swain]

Bob Perry mentioned that the cost of a mold for a 37 footer in plastic costs around $300,000 US. A much cheaper male mold means having to spend weeks grinding and fairing the hull, not a fun job. The last quote we got for the steel or a 36 ft hull and decks, recently was around $9K. No mold or fairing required. About a weeks work to pull together a 36 hull and decks.
A friend made a male mold for a plastic 26 ft Bristol channel cutter. Took him a year to build just the mold. Then he priced the fibreglass to build the hull, and was quoted $9K . That was in 83. Then he saw me put together a 31 in three weeks for $3500, walked away from his mold, and built himself 31 in steel. Steel is a far better choice for the home builder, a fraction the cost in time and money, of plastic. Several home builders I know, after building their own steel boats, went on , from being unskilled labourers, to metal working tradesmen, working for journeyman's union wages .
When the metal work is done ,you have all your cleats, handrails, engine mounts, Rudder fittings, hatches ,mooring bits, tanks, anchor winch and bow roller, hatches, wind vane ,etc etc, all stuff you have to go out and buy for most plastic boats. A friend said, for a plastic boat ,to put down cleats, you have to buy bolts ,cleats bedding compound, backup plates ,then you need two people to bolt it down. Then you have to rebed it from time to time. On a steel boat you take minutes to built a cleat from ss rod ,at $2 a pound, and a minute to weld it down.It never leaks, and never needs rebedding. Ditto most of the deck hardware on a steel boat. That makes the metal work on a metal boat much bigger percentage of the finished boat, than a plastic hull and decks.

 

[Brent Swain]

Absolutely ... but it's not a "law". In fact the only results I get from googling "law of mechanical similitude" are from boating publications, so it looks as if it may be a myth which has established itself in that world.

Compare the legs of an elephant with those of spider. So much thicker on the elephant. How would they do if they had, porportionately, the same legs as a spider?
Not so well. A clear demonstration of the law of mechanical similitude. That is why a freighter will break in half if it is not very accurately supported in a dry dock, but on small craft, it doesn't matter.

 

[Brent Swain]

I am puzzled - some would say that's my perpetual state.
There are a lot more people cruising the world in GRP boats than steel.
Steel boats regularly bounce off reefs/rocks/hiabs.
If the same percentage of GRP boats were bouncing off the same stuff then surely we would be hearing of deaths, families, clans and small countries being wiped out on a regular basis?

Plastic boats invariably break up on reefs, steel boats rarely do. Plastic boats which hit things, often sink quickly without a trace , taking witnesses along with them. Posts about missing and lost at sea cruisers are common on many chatlines.

 

[Brent Swain]

The rate of abandonment is different. people abandon GRP because of the systems and rig problems, while steel owners do it because of the hull.
And both do it because of money (lack of) apart from the broken dreams and soured relationships.
I could be wrong here, it has happened ;o)

Lack of money is largely caused by getting suckered into "Yottie" priorities rather than the more practical workboat priorities.
Friends who bought older plastic boats around here are almost invariably plagued by rotten balsa cores. Is that a problem on your side of the ,or did they have the wisdom to use foam cores more? Boats on your side have long tended to be far better built.

 

[prv]

Damn, I was hoping for a new career and a plentiful supply of nubile young ladies to keep me happy.

I think that’s Wharrams

Pete

 

[PeteCooper]

Lack of money is largely caused by getting suckered into "Yottie" priorities rather than the more practical workboat priorities.

Complete and utter bollox.

 

[Brent Swain]

Complete and utter bollox.

Teak decks and teak trim contribute nothing to the function of a boat. Ditto lot of other expenses done for no other reason than pretentious yottieness. Expensive complexity often detracts from it. Both can drastically increase the price tag, pushing the dream permanently out of reach, for far too many.
I met a boat from Darwin which a German had built and sailed that far ,before health problems cut his dream of a circumnavigation short. I could see all kinds of ways he could have done things cheaper and quicker, and got out far sooner , realizing his dream ,rather than losing it to pretentious yottieness. I have seen that story repeat itself ,time and time again.

 

[john_morris_uk]

Plastic boats invariably break up on reefs, steel boats rarely do. Plastic boats which hit things, often sink quickly without a trace , taking witnesses along with them. Posts about missing and lost at sea cruisers are common on many chatlines.

Some references please.

My quick search of various web sites hasn’t found any evidence of what you claim. I don’t know what you mean by ‘chat lines’. If dozens of people were disappearing then it would make the news.

 

[solent clown]

Being as metal was my day job for decades, and having recently had a change of lifestyle that afforded us time and space, I did consider building a 32ft steel boat. Maybe things are different in the west ex colonies, but here in the UK it added up to a horrendous cost fro the steel and epoxy even without fitting the boat out. Most steel here has gone up 25-40% in the last year, which does not help, and epoxy seems more expensive than liquid gold.
So we took the approach of looking at old grp boats - thats isnt quite true, we looked at anything cheap, it could have been cement or glass we didnt care.
In the end we found a 31ft grp fixer upper. That became available precisely because it was damaged by rocks. Despite that it did not go to the bottom, and the damage was limited. the boat cost £400. There is work to do, a few days worth over few weeks. in materials it will be under £500. That is sailing on a shoestring. I buy some of your arguments about steel boats, but not the economic one in the real world. There are plenty of fixer uppers out there for the handy.