Homemade Houseboat

Discussion in 'Boat Design' started by JCal, May 24, 2018.

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  1. JCal
    Joined: May 2018
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    Location: Louisiana

    JCal Junior Member

    Hey guys

    I want to build a houseboat. I’m not very well versed in boat building or calculating buoyancy, but I’m hoping y’all can help.

    I have two 20’ long, 36” around, 1/2” thick iron pipes. They have been sitting in my pasture for awhile now, until I got the idea.

    My plan is to weld caps on either ends of the pipes, weld a frame tying the two pipes together, and build a small 12x20 cabin on that frame.

    My judgment is that regardless of how heavy the pipes are, they will still float because they’re a sealed container. And they should be able to hold a little weight since they would be displacing a good bit of water. But I’m not sure, I don’t know how to calculate buoyancy or how much weight they would be able to hold, and I don’t want to weld them up and stick it in the water until I’m 100% sure of those things. So I’m here.

    Any help would be much appreciated

    Thanks :)
     
  2. Rurudyne
    Joined: Mar 2014
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    Rurudyne Senior Member

    How about using them structurally instead?

    Cut in half lengthwise they could form a set of four lengthwise continuous arches as part of a platform foundation supported in turn by blocks of flotation foam. Really, for the size only one of the two would be needed for that use, giving you two 20' long structural members. Or use both for a longer platform. You may want to look up how old riverboats used truss like structures for rigidity for if you went longer.

    Another option would be to use them covered with a layer(s) of flotation foam blocks cut accordingly (a bit like making a bowl turning blank from 1x4 stock, only really long, maybe done in overlapping "tiles" of foam so you aren't trying to wrangle and precisely glue long floppy blocks) and then all sealed under a layer of fiberglass, that wouldn't increase weight much but could increase displacement considerably. Some modest internal bracing might be in order.
     
  3. Tiny Turnip
    Joined: Mar 2008
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    Tiny Turnip Senior Member

    If my back of an envelope calculations are right, each of those pipes weighs around 1.7 metric tonnes not including end caps, and will displace around 4 metric tonnes. So on their own, they'd be floating around half out of the water. In theory you could add up to 4 tonnes on both (build, gear, supplies, people) to point of swamping, but you'd want some free board, how much depending on how sheltered it is where you are mooring up. (I'm guessing you're not planning to travel in this.) So for 6 inches freeboard, which is probably not enough, you might be limiting your payload to 2.5 tonnes. That's everything. I stress these are very rough unchecked guesstimates.
    Here's a thought; might be worth checking out the local scrap value of those pipes - 3.5 tonnes of steel? and putting it into a second hand pontoon/hull ?
     
  4. Dave T
    Joined: Sep 2011
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    Location: Anamosa Iowa and North Buena Vista on the Mississi

    Dave T Senior Member

    36" around? Do you mean 36" diameter or is this the circumference which would be about 11 and 1/2" diameter?
     
  5. Tiny Turnip
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    Tiny Turnip Senior Member

    If it is circumference, which, in fairness is how it reads, then scratch my post!
     
  6. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    The pipe you describe appears to be schedule 80. It weighs 65.4 pounds per foot , for a total weight of 1308 pounds per piece. It has a section area of 113 square inches. It is 240 inches long therefor ...27,143 cubic inches . That will be good for a displacement of 980 pound.s. If you cap the ends and throw it into the water it will sink promptly. Simply stated it weighs more than it can displace. Sorry for that unfavorable bit of arithmetic.

    Pipe weight taken from American Institute of Steel Construction manual. Half inch thick steel weighs 20.4 pounds per square foot Standard pipe is available in 10 inch diameter and 12 inch diameter. The actual diameters of the pipes are 10.75" and 12.76" respectively. In either case the circumference that you have quoted; 36 inches, does not quite compute. If this is standard pipe, the circumference is either 33.77 or 40.0 inches. In either case the pipe will sink because of its own weight.
     
  7. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    If you mean 36" diameter, then it's about 18 000 pounds of buoyancy there.
    So, you're good with about half that for total weight on a small, protected pond.
    Or, 1/3 if needing any seaworthiness.
    So, not a great plan unless you're okay with very little on top, like a party barge.
     
  8. JCal
    Joined: May 2018
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    Location: Louisiana

    JCal Junior Member

    Hey man thanks for your reply!

    That's a really out of the box idea. I like it, but were at a point where were trying to make do with what we have, and if we need to invest in Styrofoam blocks we might scrap the pipe idea completely and opt for something different. My main goal posting on this forum was to see if anyone with more experience than me in boat building thought that my idea with the pipes would work.

    Nevertheless, thanks for your reply man, ill definitely take it into consideration
     
  9. JCal
    Joined: May 2018
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    Location: Louisiana

    JCal Junior Member


    I'm sorry i wasn't clear. the pipe is 12" in diameter and 36" circumference
     
  10. JCal
    Joined: May 2018
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    Location: Louisiana

    JCal Junior Member


    I should have been more clear when i wrote my post i guess:rolleyes:

    The pipes are 12" in diameter and 36" circumference
     
  11. messabout
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    messabout Senior Member

    If 36 inch diameter, each capped 20 foot pipe would displace 8820 pounds. Each pipe would weigh about 3900 pounds when capped. Net buoyancy about 4900 pounds.

    That would be a pipe suitable for the Alaska pipe line or other oil transmission pipe. The OP is apparently in Louisiana. where he could possibly have such a ginormous pair of pipes.
     
  12. JCal
    Joined: May 2018
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    Location: Louisiana

    JCal Junior Member

    You just answered my question :( it was just an idea I had. I didn't know the first thing about the buoyancy of pipes, much less a pipe that big in size.

    So i guess my next question is, what would the best option be? If i cant use the pipes i have i guess i need to invest in something else. But i don't know the first thing about boat building, or houseboat building to be more specific.

    I'm very keen on it being homemade. I like the DIY aspect of it, and it will hold great sentimental value to both me and my dad. So I'm not really interested in buying a pre-made pontoon and slapping a pre-fab shed on top:confused:
     
  13. JCal
    Joined: May 2018
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    Location: Louisiana

    JCal Junior Member


    Funny you should say that, being as theres a company laying a pipeline down near my house:p my dad has also worked on natural gas lines for 40 years.

    The pipes are only 12" in diameter though, sadly they wont displace as much lol. Check out my reply to your other post
     
  14. Tiny Turnip
    Joined: Mar 2008
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    Tiny Turnip Senior Member

    Could you give some more information? Where is this to be floated? How are your woodworking/metalworking/composite working skills? Machinery you can access? Budget? What have you got lying about to build from if you want to DIY as much as possible? (Any tanks, containers, silos, stashes of a thousand or more gallon containers etc???)
     

  15. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    I'd strongly recommend you elect to build your houseboat, from plans and not attempt to self design, just because you have some large diameter pipe laying around. There's a whole lot more to doing a safe design, than the displacement of the pipes and generally you're trying to save weight wherever you can, which 1/2"wall pipe seems to be self defeating. Additionally, pipe isn't a structural material, tubing is and yes there's a big difference, engineers are all too familiar with. Plans are available at a number of sources, have a look.
     
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