Houseboat design...

Discussion in 'Boat Design' started by duns227, Jun 17, 2010.

  1. duns227
    Joined: Jun 2010
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    duns227 Junior Member

    Hi all. I've been lurking for a while enjoying the site and trying to absorb as much info as possible. I've been ticking over some boat design ideas in my head and thought I'd see what you think.

    Warning: Long and boring design below. Feel free to not read :)

    I've been toying with an idea for a houseboat and wanted to run the idea past you guys (& gals) for critique. I'm shooting for over-engineering of a vessel that would require minimal maintenance and longevity. Feel free to tell me why I'm an idiot :D

    First off. the primary purpose of this boat would be a full-time live-aboard with the majority of the time spent on anchor (or 'the hook' as I believe it's called).

    What I was dreaming up is a pontoon boat deck that is 50' long by 10' wide supported by 3 pontoons that are 36" diameter by 50' long.

    On top of that deck, I'd visualized a rectangular cabin (not sure if this is the correct term) that is 40' long by 10' wide by 7' tall. This would leave 5' of deck at both ends. The cabin walls would be made of (fairly thin) aluminum panels with aluminum I-beams or square tube as the wall supports. I actually envisioned use of glass or plexi-glass as the roof to let light in, and large windows on the sides. A door in the front center and back center would provide access to the cabin.

    I envisioned a sundeck on top with aluminum decking (some sort of mesh or grating to allow light to the clear roof). The sundeck would be 45' long by 10' wide and extend out over the bow deck. There would be light aluminum railings.

    Now I know you're laughing at me right now because there's no side decking, but here's my ace in the hole. I envisioned a 4-foot wide deck on both sides supported by 2 more 50' long 36" diameter pontoons (for a total of 5, yes 5 -go ahead and laugh). These side decks would be attached via 3 long aluminum I-beams that would slide into and bolt to the main boat platform with a minimum number of bolts (more on this later). Of course there would be railings.

    For power I was thinking twin 4-stroke outboards behind the outer pontoons of the main deck (not the railing pontoons). I'd like to see the outboards have their own battery, separate fuel tanks and controls inside (along with separate throttle, gauges, etc..). The only thing common between the engines would be the steering system (I'm thinking hydraulic). Probably 30 gallon fuel tanks for each. I was actually thinking the motors would be fairly small. Maybe 20 to 50HP each with hi-thrust props. Because, let's face it, this beast will move sloooooow.

    I would like to see it have a 400 gallon potable water tank and 600 gallon black water tank hung underneath the deck, with a 50 gallon drinking water tank inside the cabin.

    I'd also like to have in the middle of the back (running up the back wall of the cabin) a boom and crane arm. The main column would be part of the back wall and the arm would fold down against the back wall when not in use and be able to lift things behind the boat. Just plain handy to have around.

    I'd actually thought about having a smaller pontoon as a pull-behind (some people call them toads I think???) that would house the power generation equipment. It would house the generator, fuel, and battery banks. It would be attached to the main boat with some stout aluminum pieces under the water. There would be a 4 inch flexible pvc water line with the electrical cables run through it connecting it to the main boat.

    Random thoughts and reasoning:

    5 pontoons of that size by the calculations from >>here<< should give a floatation value of 53,950 pounds, or about 27 tons. I think that ought to be waaaay more than sufficient to give a very reasonable margin of safety even with almost 9,000 pounds of liquid aboard. Not to mention some hefty anchors. I'd think it would be ok even if one pontoon was full of water.

    The boat would be 18' wide by 50' long and about 11' tall (not including sundeck railing). Does this sound like it would be fairly stable? I'd still keep the weight low inside and I think the water tanks underneath the center should help also.

    The reason for the side decking pontoons being held on by only I-beams is that I want to make them removable (fairly easily). That way if I ever need to I could take them off and the boat would only be 10' wide and 11' tall which should be trailer-able. Might be an oversize load, but still movable.

    I like the totally separated twin outboards for redundancies sake and you could just run one at a time if you wanted.

    I like the idea of the power generation/storage equipment on a separate vessel because it would cut down on vibration from the generator and get the generator exhaust that much farther away. Plus I don't like the idea of batteries with corrosive/explosive gas on the boat much (I realize the outboards will have batteries on the boat - just have to live with that).

    I'm trying to stay away from any building materials other than aluminum. The use of zincs will be mandatory of course, but from what I've read, not mixing steel and aluminum reduces galvanic corrosion. Also I intentionally stayed away from wood. Why would anyone use something that rots as part of the main structure of a boat???

    Obviously this boat won't be going on the ocean or any big water. I was thinking more along the lines of inland rivers. The ohio, Mississipee, etc.. It should have a fairly shallow (18 inch) draft so could go a lot of places. With the extra width from the railing pontoons though (almost like outriggers), I'd think it could handle a little weather. Maybe not. Any thoughts?

    I know the cabin will get really hot/cold being made of metal, but I was thinking more of a snowbird lifestyle. Going south in the winter and north in summer.

    Any comments? (as he zips up flame retardant suit, just in case...). :D
     
  2. apex1

    apex1 Guest

    At a first glimpse, I don´t see any major faults in your plan....

    ...except for the metal structure of the "house". Aluminium is a perfect heat conductor, that makes it a sauna in warmer climate, a freezer in cold weather.

    A ply sandwich (ply/foam/ply) would be cheaper, stiffer and insulate well.

    " 20hp outboards should be sufficient to move that even against some wind or current (probably not much when these accumulate).

    Regards
    Richard
     
  3. Stumble
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    Stumble Senior Member

    My first thought would be to buy a retired barge. They come in the size you are looking at, normally steel, and can be had for about or less that the scrap value. Then you just have to do the outfitting instead of hull construction
     
  4. Grant Nelson
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    Grant Nelson Senior Member

    Sounds like a plan to me. Some thoughts
    Aluminum will work, but why not quality wood construction above the deck? Since you are not going to sea, you have little to worry about in regard to needed a lot of extra strength or low weight up high.
    I think you should make one of the end decks longer, you will find you just want to walk out the door and have a biggish place to sit and watch the sun set, and not have to climb up to the sun deck which is also so far above the water you wish to live on.
    Maybe it will work not to use extra pontoons for the removable side decks, but instead make some decks that just fold up against the side, but mainly stay down. I am guessing the boat will be heavy enough that a person walking out there will not tilt the boat too much. If that is the case, maybe one smaller inflatable or small pontoon you can put up on the sun deck when not in use.
    Two engines is good idea...
    Mainly its a floating house, not a boat. Indeed stability is key, but at 20 tons (seems a lot) with the pontoons half submerged, you will be OK. That will need some calculations, relatively simple, once you know where your center of gravity will be and have details on the pontoon shapes...
     
  5. Jeremy Harris
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    Jeremy Harris Senior Member

    If you want the relatively low maintenance of an aluminium exterior, then you could look at using an alloy/foam/ply sandwich. I built a big box trailer like this a few years ago, using panels I made up myself and it ended up pretty light. I just bonded 2" foam sheets to alloy sheets, using polyurethane adhesive, then bonded ply sheets to the other side of the foam. The resulting sheets were light and very stiff, so I didn't need as much framing. I built the framing into the sheets at the edges, so it was pretty easy to construct the whole superstructure.

    Jeremy
     
  6. apex1

    apex1 Guest

    Good idea Jeremy!
     
  7. SamSam
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    SamSam Senior Member

    Are there different kinds of polyurethane, like different kinds of glue? What kind did you use? How did you go about making the panels? Did you have to clamp or apply pressure?
     
  8. Jeremy Harris
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    Jeremy Harris Senior Member

    I built panels that were 8' x 4', with built in framing that was the same thickness as the foam, 2" but only an inch wide, for lightness. The glue I used was ordinary polyurethane construction glue, the light brown treacly stuff that cures by absorbing water from the atmosphere, a bit like Balcotan (but cheaper!).

    I found that to keep the alloy sheets flat I needed to build the panels by laying the alloy sheet on the workshop floor (on top of some ply sheets to avoid scratches). I just roughed the alloy sheet up with coarse abrasive, smeared the glue over it, then laid the foam sheet and wood framing on. I used a few bricks to weigh the sheet down whilst the glue cured. As soon as it had, I glued and pinned (to the framing) the inner plywood skin to the foam. I used a few bricks on it to keep it flat.

    The one important lesson I learned was to mark where the timber internal frame members were on the skins, so that I could find them later. I made the panels with an overlap on the outer alloy skin, and when I bonded the panels together (using Sikaflex polyurethane sealant/adhesive) I made sure that the lapped joint was well-bonded. If I'd thought about it, I'd have used a joggling tool to created the lapped joint in the alloy skin more neatly, but it worked OK without this, as the outer skin was thin, just 18g.

    Despite the thin skin, the finished panels were very stiff and solid. I'm reasonably sure I didn't need as much internal framing as I used, but it was better to be safe than sorry.

    Jeremy
     
  9. duns227
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    duns227 Junior Member

    Thanks for the feedback all. I like Jeremy's foam core sandwich idea. I wonder if you did that but made an alloy-foam-alloy sandwich if that would provide enough insulation to keep it from being a summer sauna / winter freezer?
     
  10. duns227
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    duns227 Junior Member

    Also - could someone explain exactly what maintenance an aluminum exterior would need? Other than changing the anodes on the pontoons?
     
  11. apex1

    apex1 Guest

    None..............

    And for what would you need anodes? You don´t submerge the "house" just the pontoons.;)

    sure, but how would you hang the pictures of your beloved on the wall?
     
  12. SamSam
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    SamSam Senior Member

    Thanks for the reply, Jeremy.
     
  13. duns227
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    duns227 Junior Member

    True that. I'm a little ignorant on the whole electrolysis/galvanic corrosion issue. Need to read up some more on that.


    Hadn't thought of that!
     
  14. duns227
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    duns227 Junior Member

    double post
     

  15. duns227
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    duns227 Junior Member

    I'd considered that, but steel rusts, and usually from the inside out from what I've read. I like the idea of aluminum pontoons because they last (mostly) forever and even if one gets a hole in it, it still won't sink due to being compartmentalized (then again they said the same thing about the Titanic :D ).

    Besides a steel barge would be super heavy wouldn't it? I like the option of being able to pull it out and move it down the road.
     
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