new idea for boat galvanized oriental junk

Discussion in 'Boat Design' started by gp1953, Oct 16, 2007.

  1. gp1953
    Joined: Oct 2007
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    gp1953 Junior Member

    Thanks for some of you responding to the barresl and raft ides. I've been thing this over and have come up with this idea. John boats are very stable and was thinking if one could build one out of galvanized steel around 8 foot wide and twenty foot long with the center part around five foot. One could use the quansen hut idea and put hoops in the center portion for the living quarter and sealing off both ends to store provisions. It would be kinda like a modern day oriental junk. I could have it all welded up here locally even have a building i could use for the project. Any suggestions or ideas?
    thanks
     
  2. rwatson
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    rwatson Senior Member

    Yes, that would work. It may not even need to be galvanised, as there are a number of other rustproof surface types available.
    Steel boats however, generally arn't made of galvised steel due to the implications for bad welds. Better to weld plain steel, and then coat it.
    Steel has many advantages in boatbuilding like instant structual properties.
    The other consideration you may want to think about is if you would like to do more than explore sheltered waters. Probably for not much more than it would cost to build a 'seat of the pants' craft, I am sure you could build an existing design that would be a proven seaworthy solution, especially with those dimensions you gave in mind. eg www.bruceroberts.com
    You would be surprised how easy it is to learn to weld yourself, and for a few hundred dollars, a night course at a tech school, you could do a lot of the work yourself.
     
  3. Gilbert
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    Gilbert Senior Member

    It should be mentioned that welding or heating galvaized metal gives off dangerous gasses that are very harmful if you inhale them.
     
  4. alan white
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    alan white Senior Member

    It can make sense to use galvanised pipe and weld it, but the dangers of zinc fumes are very real (whitish smoke, sweet taste/smell). The way around this is to use muriatic acid and/or a sanding disc first, removing enough zinc coating to keep the remainder cool. Trailers are built this way, and afterwards coated with a cold galvanizing compound.
    Regarding doing the welding yourself, this technology has become much easier in recent years. The process is either MIG (metal/inert gas) or flux-coated wire feed. I recommend the MIG process and the Lincoln 135T welder.
    This will cost about $400.00 US, plus inert gas cylinder rental or purchase. You can own the whole setup for about $550.00 US. You can learn to weld MIG in a week (not achieving beauty, but certainly function).
    flux-coated wire feed uses no compressed gas, but instead uses flux-coated wire fed through a tube directed at the work. $300.00 US. Cheapest weld you can easily make short of arc welding, but far easier than arc welding.
    The advantage of MIG over simple flux/wire feed is the MIG doesn't spatter or have to be chipped of the burnt flux after. The simpler flux-coated wire type has the advantage of being easier to use in breezy locations (outside) and generally will weld hotter.
    You ought to investigate welding it yourself. Otherwise, you will be paying someone a lot of money.
     
  5. gp1953
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    gp1953 Junior Member

    What gauge of steel would you recomend to build a over sized johboat with? I like the simplicity of the design it would be good for shallower waters. This would be for fresh water not for the 7 seas. thanks
     
  6. rwatson
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    rwatson Senior Member

    I had never heard of a John Boat before - having looked one up, an oversized John Boat would be a barge - almost straight sides, perhaps a sloped bow.

    The gauge of steel will mostly depend on how much frame work you want to build. You could almost just use 5 mil plate and not have to do much framing, but you would find it really heavy, and easy to get permanently stuck in the mud. If you used say, thin gauge like galvanised metal, you would need a lot of framing, but then if you ran it into a sharp rock you would spring a leak.
    I stand to be corrected here, but for the cheapest, easiest (least work and design) stiffest hull of this size, 3/8 exterior ply with a fibreglass seams, and a good coat of paint, and still be light enough to tow on a trailer would be the go IMHO.
    There is a good chance you could pick up used exterior ply that didnt require much repair for hardly anything.
    Welding isnt hard to learn, but I think fibreglassing might be even easier and not require purchase of a welder.
    Aint planning the best bit of boat building :)
     
  7. gp1953
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    gp1953 Junior Member

    Where would on fine used exterior ply wood? and yes a jonboat is basicly a small barge used for bass fishing in shallow waters
    thanks
     
  8. alan white
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    alan white Senior Member

    16 guage would probably be about the lightest I'd go. With the right paint, it would last a while. Heavy, of course. 300 lbs maybe. 16 ga is 1/16" of an inch (though this is a coincidence, and not applicable in other guages).
    Oops, just read "oversized". meaning... 20 ft? I was thinking 12 ft. Maybe 14 guage would be better. I wonder, though, at what point painting costs for steel are greater than the higher initial cost of bare aluminum?


    Alan
     
  9. rwatson
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    rwatson Senior Member

    Used Exterior ply can often be picked up from large construction sites or building companies where it is used for hoardings, temporary concrete formwork, safety barriers and the like.
    Also, talk to large hardware shops - often valuable items like bathroom equipment, expensive machinery come in big plywood boxes, and they will often sell it cheap.
    I would also visit secondhand building suppliers and tip sites if you are allowed in.
    While you are there, keep a lookout for any decent timber over a couple of metres in length. You can always saw it to a narrower size, or just use it for part of the working bench you will probably create.
     
  10. newinertia

    newinertia Previous Member

    GP- I have fabricated steel outdoor structures of 35' x 6' and weighed 6000lb. and had the entire structure hot dipped in zinc galv. for about $1200 US.
    I know that sounds like a buttload of money, but the hull will last 100 plus years. dont forget to take into account the weight of the zinc- it usually adds up to 8% of the original wt. for sheet based products. Beam structures, less. if there will be any tubes in the design, air escape holes will have to be drilled many places to allow for coating on the insides, as well as the expanding air to escape or tubes can explode or rupture- causing molten zinc to be sprayed on the workers dipping your object.
    below are pics of the project, if I can have this hot dipped, you surely can do a hull! - I say build it!
     

    Attached Files:

  11. newinertia

    newinertia Previous Member

    By the way, MULLINS boats like this were Galvanized Steel at the turn of the century.
     

    Attached Files:

  12. gonzo
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    gonzo Senior Member

    Jon boats have stamped bottoms and sides for rigidity. If you build one with flat panels, either it needs a lot of framing or really heavy gauge metal. Either way it would be heavy
     
  13. Frosty

    Frosty Previous Member

    Zinc is what sacrificial anodes are made of. You gonna put that on your boat?

    Hot dipped galvanized anchors dont last 100 years! --about 10 years and 99% of that time they are not in the water.
     

  14. thudpucker
    Joined: Jul 2007
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    thudpucker Senior Member

    AlWeld.jpg

    Here's my Al-Weld Jon boat. Great product. It has the slightly sloping bow. Gets up on the plane quickly, stable enough for me to Dance and big enough for me to laydown and nap while fishing.:D

    You could make this out of old Roofing materiel if you re-inforced it and didnt get real rough with it.:D
    The trick is floatation. It does not have enough. It will sink!:(
     
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