Is it possible to build in steel if not originally designed for steel?

Discussion in 'Boat Design' started by eggman918, Jan 15, 2011.

  1. eggman918
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    eggman918 Junior Member

    I am having trouble finding plans that I like in steel.
    Is it possible to take design not in steel and build in steel
    without comprising the design? I know this is a broad question
    But I need to know before I go any farther.I have a structural engineer
    who works withe me on many odd problems so together we should be able
    to crunch the numbers.
    Is this a bad idea?
    Steve.
     
  2. Tad
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    Tad Boat Designer

    Broad answer for a broad question.....

    It depends.......
     
  3. eggman918
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    eggman918 Junior Member

    Fair enough, if I am going from wood to steel and develop a steel hull of same
    strength and it sits within the designed waterline would it have similar stability?
    I am not trying to be a pain and if it is best to give up this idea so be it.
    Steve.
     
  4. Tad
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    Tad Boat Designer

    Sorry.....I did not mean to aggravate......

    You did not specify the original construction material....it could be that a design originally fero-cement might convert to steel construction without too many problems....weight wise at least.....

    But steel is far heavier than most wood (again it depends), so structural weight might go up considerably.....building in very light steel is possible (as you know) but can be tricky and expensive paint wise........

    Also some designs can benefit from increased structural weight while others will be compromised to the dangerous point.......

    So it gets pretty specific and will probably cost you consulting time with an expert NA to find out for sure........
     
  5. gonzo
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    gonzo Senior Member

    It depends. Can you post the boat lines? To get the same stiffness on a steel boat, the weight will be much higher unless you are talking of 80' or more.
     
  6. Tad
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    Tad Boat Designer

    And if your steel version floats on exactly the same waterline as the wooden boat.....it will probably still have a lower angle of vanishing stability due to higher VCG because of the heavy steel deck and house.......equal stability could probably be obtained by changing the hull lines and adding ballast........
     
  7. eggman918
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    eggman918 Junior Member

    I was thinking that in steel it might roll very differently.
    I need to look for more options already in steel,thank you all for the input it is helpful.
    One more question off the topic but my local blasting/coating co. can powder coat
    things up to 25'x12'x12' so is powder coating a hull as a completed unit practicable?
    We have had good luck on pumps in Municipal water systems where the expected life between overhauls 20 years.
    Steve.
     
  8. eggman918
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    eggman918 Junior Member

    My first choice before talking to anyone was Atkin's "Martha Green" out of steel.
    It seems a heavy built wooden frame as well as easy to plate I like the looks but do not have enough experience with hydrodynamics or boat driving to judge hull performance.
    But at least I know that I dont Know.
    Thanks for helping sort this out.
    Steve.
     
  9. viking north
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    viking north VINLAND

    As a general rule the weight factor of steel limits the building of boats in the lower displacement range, however aluminium does not. When all is said and done construction in aluminium is possibly less than steel when you factor in labour hours,sandblasting the hull inside and out. Prime and paint the hull inside and out. Constant maintenance on steel hulls in a salt enviorment and don't forget tedious compass adjusting. Welding material costs are more but not an extreme factor in the construction of the hull and you can always go with a wood core epoxy GRP deck and superstructure. Welding labour is the same wheather steel or aluminium. Many designers will only charge a nominal fee to modify construction in aluminium as it is similar in weight to ply. where flat panel construction is concerned. Anyhow if metal is your choice i highly recommend you consider aluminium. Converted an alum. lifeboat built in the 1950's to a motorsailer, installed 6 hull zincs as recommended,sailed it for 8 yrs. never had as much as a corrosion blemish on the hull. Sold it in 2000 and as far as i know it's still sailing. Food for thought. Geo.

    A yacht is not defined by the vessel but by the care and love of her owner.
     
  10. Landlubber
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    Landlubber Senior Member

    ..forget powdercoating, you will be using epoxy and follow one of the better manufacturers directions. Powder coating is NOT for underwater us or anywhere near the sea. Try Altex Devoe web site.
     
  11. eggman918
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    eggman918 Junior Member

    Aluminum is my second choice only due to my lack of experience in welding it.
    But if that ends up being my best choice it will not be difficult to master and need a new bed on my truck and it is perfect project to learn on. It does cut much easier,the more answers I get the more questions I have funny how that works.
    thanks again
    Steve.
     
  12. viking north
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    viking north VINLAND

    If you do go with aluminium, don't skimp on the mig unit, get a high amperage and a good brand. Another alternative if you presently own a good ac/dc stick welder is to buy an add on, what they call a Box that allows you to mig alum.I addition to a good circular saw with proper alum. cutting blades a plazma cutter is a must. The brand not so important. For mechanical cutting, King has just come out with a metal cutting two blade compact saw that might be worth a look. My similar tool is the Ridgit cement board cutting saw but a little on the expensive side. Either of these tools will replace the circular saw and much easier to operate. The golden rule when working with alum. CLEAN, CLEAN, CLEAN, METAL, With the mig, HEAT SETTING, WIRE FEED RATE, in that order, always set it up on an scrap piece every day before you start welding. Geo.

    A yacht is not defined by the vessel but by the care and love of her owner.
     
  13. BATAAN
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    BATAAN Senior Member

    In Holland, everything floating from 8' prams and larger seems to be steel. The prams have no frames, just rod chines, and are wonderfully fair. Weston Farmer converted the TAHITI ketch to steel in TAHITIANA and was successful, so it can be done but must be properly engineered by someone who really understands the material.
     
  14. viking north
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    viking north VINLAND

    One of the problems as i understand it from what i've read and it sounds logical is there seems to be a point where the designer reaches a catch 22 situation, the hull has to withstand a certain level of forces(stress) and there are several ways to build to withstand these. #1 a thicker sheeting material which increases weight(displacement) which in turn increases the hulls emersion. #2 A thinner sheeting material(and there is a limit) which in turn requires, closer spaced framing which in turn requires, more framing material, which in turn increases weight, and you guessed it increases the hulls emersion. The limit is reached when there is a balance of an acceptiable min. sheeting thickness along with it's required framing places the completed vessel on or very close to it's designed waterlines. Now not being an engineer i can't calculate what that might be but it certainly would have to do with hull form and it's designed emersion water line. I can see prams and smaller boats being built in thin steel sheeting with pipe chines as the longitudional and torque stresses on these would not be a big factor. It's an interesting subject and once caught up into one of these carch22 situations the designer certainly would have to be critical possibly erring on the heavy side accepying the deeper emersion and the little extra wetted surface and drag, however there is a point of no return. Geo.
    P.S. Battan, now i remember you,Spray owner, I have two neighbours that own them, both moved here from Ontario, big boats 45ft. i think one built in cement the other in glass. Viewed your build in wood , excellent craftsmanship from what i could see on the photos.

    A yacht is not defined by the vessel but by the care and love of her owner
     

  15. BATAAN
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    BATAAN Senior Member

    When the radicals of the 1860s started building iron, then steel ships they found that they were much lighter, had more space inside, and were faster. Two framing systems were developed then, and work now, transverse framing and longitudinal.
    Small steel seems to work well with longitudinal framing and can get quite light, like the Dutch prams I saw on the wharf in Amsterdam. Google "origami boat" and see what comes up. A guy designed a cut-and-fold canoe-form hull than really was origami. I was walking down the road and saw a truck unloading sheets of 3/16" "cor-ten" steel at a boatyard and asked the builder what he was doing. He said origami boat and I said whatever. I came by a week later and there was a 40 foot hull, less ballast keel, cut and folded and welded and getting its deck, skin-first construction.
    There's always a way. I did a survey on a Dutch-built 35' conventional marconi sloop and found it lightly framed, expertly plated, and at 40 years old, in pretty good shape. There was oiled paper between the steel deck frame and the wood deck and both were in good shape for their age.
    Steel is a viable material for quite small craft, but again gets weak in corrosion resistance when it gets thin and light.
    I think your above analysis is quite correct in trying to find the "trade-off-point" of where steel is not the best idea. Personally, I like wood/epoxy or conventional wood, as they are cheap and long lived. Aluminum is immensely strong and durable if you can afford it. 10,000 Alaska fishboats are made of it and they beat the bloody snot out of them beach fishing with gillnets.
    Ya pays yer money an' takes yer choice.
     
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