Need Advice with Houseboat Construction

Discussion in 'Boat Design' started by SNGPSo, Feb 4, 2021.

  1. fallguy
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    fallguy Senior Member

    Well, you might want to rake the forward ends for transport. This will reduce your buoyancy some; so you may need to accomodate by going wider, but I think maybe you don't want to design too close, either.

    Forget nominals. They almost never work. They are okay within reason. Like, no reason to go wider by an inch, but nominals on the length are a bit foolish, for example.

    Another thing to consider is reserve buoyancy. This might be like making the thing wider as it goes up which helps with passengers. Most of this is really only general knowledge for me. I am not an NA and cannot delve into specifics.

    I can't tell how thorough you were here, but a good start for sure.
     
  2. fallguy
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    fallguy Senior Member

    Also, not sure about the use of gypsum on a boat. Ain't saying it can't be done, but it wouldn't be anything I'd use.

    I'd use a 'cheap' marine foam, rebated for tape seams. I think gypsum will not finish well, but honestly not too sure. @bajansailor might have better ideas about wall sheathing.

    I would be concerned shifting of the boat during transport would mess up sheetrock wall finishes. And the rock is super heavy.
     
  3. bajansailor
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    bajansailor Marine Surveyor

    Is the gypsum mentioned in the spreadsheet calculation? The print was too small for me to read unless I saved a copy and then blew it up after opening it.
    Re wall sheathings, I know very little about them, sorry.
     
  4. TANSL
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    TANSL Senior Member

    Okay, this is getting better and better. You would now need to perform some stability check, for which you need to know the position of the CoG, and then calculate the scantlings of the whole strucure. One recommendation, the transverse elements that join the two hulls should be closed pipes and probably some longitudinal reinforcement will be necessary, inside the hulls and on the deck.
     
  5. fallguy
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    fallguy Senior Member

    @TANSL

    Do you ever see gypsum used as wall coverings? I am ever so curious.
     
  6. TANSL
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    TANSL Senior Member

    No, I have not seen it, but it would be necessary to know how and where SNGPSo wants to use it to give an opinion. The first feeling I have, without knowing anything else, is that I don't like it.
     
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  7. fallguy
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    fallguy Senior Member

    thank you for the opinion..the issue I have with it is it does not flex much before it cracks and is super heavy

    I would think houseboats would have a better wall material. But paneling or something else.
     
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  8. SNGPSo
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    SNGPSo Junior Member

    Thank you guys for all the input.

    Is raking the pontoons a necessity though, fallguy? I can try to do that but I want the pontoons (and the rest of the structure) to be as easy to build as possible, hence as orthogonal as possible.

    I am sorry but I do not seem to get what you mean by nominals. Regardless, the measurements I used for the whole plan are to eventually allow the use of 2.44m plywoods straight away with no unnecessary measuring and cutting.

    Also, thanks for bringing up gypsum boards, fallguy. As expected by someone who had not known what caused tides (har har), I did not know that gypsum would be problematic in a houseboat setting. I looked around for the marine foam you mentioned and got a lot of result about polystyrene foam, but never used with wooden framing systems. Can you be more specific about the marine foam?
    Thanks, TANSL. Yes, those calculations will take a bit of time too, especially since I keep tweaking the entire plan. About the transverse elements that join the two hulls though, by saying that they ''should be closed pipes'', do you mean aligned as in this diagram? I arranged them as such to facilitate weight distribution and transmission to the pontoons, so no joists bear any unnecessary stress (which I thought would be the case if there were no alignment between studs and scantlings).
    Weight Distribution.png
    By the way, the yellow arrows point to a pontoon section that is open inside. I wanted to reserve that space for potential tanks for any water waste that might be placed in pontoons. What do you guys think about this?

    Here is a work-in-progress 3D diagram I am doing where I intend to show the weight of every element in the houseboat, as well as to serve as a construction assembly process.
    Overall Asembly.png
    Any other suggestions about suitable materials for sheathing would also be welcome. This is how I would like the end result to be: Final Bed Day.jpg
     
  9. bajansailor
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    bajansailor Marine Surveyor

    I think you just want to keep it all as simple as possible.
    You are effectively building a wooden house on a raft.
    I would use timber for the framework (do you have to worry about termites in Morocco?), and clad it with exterior grade plywood.
    If you really want to protect it well, apply a couple of coats of epoxy resin to the plywood - and especially on the edges.
    If you want thermal insulation, you could have a sheet of plywood on each side of the timber structure, sandwiching foam in between the pillars and the two skins.
    The foam does not have to be marine construction grade - it is only for insulation, and polystyrene will work for that.
    Re the inside surfaces of the plywood, once they have been primed with epoxy, then just fill and fair (if you are looking for a perfect finish) and paint them.

    Will your houseboat have to pass inspection by any Authority re it's resistance to fire?
     
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  10. SNGPSo
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    SNGPSo Junior Member

    It will be inspected for fire resistance.

    I was only planning on using marine plywood for the pontoons, since they are submerged all the time. I was also planning on running coats in the pontoons parts in the following layers: epoxy coat, fiberglass, then another epoxy coat.

    I have never heard of any termite problems, but I would have to check.

    Alright then, plywood it is.
     
  11. TANSL
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    TANSL Senior Member

    Excuse me for my poor English. I was referring to the fact that the transverse reinforcements should not be open but closed as the latter better withstand the torsional forces that occur between both hulls. And on the other hand, making them solid means using a lot of material that does not add resistance to the reinforcements. But, if these reinforcements are to be made of wood, my comment does not make sense.
    If you have to make it fire resistant, I would recommend that at least the pontoons be metallic. FRP is not combustible, resin is, but it does not maintain structural consistency.
    I agree with you that the pontoons should be as simple as possible, a continuous cylinder throughout its length. There is no need, in my opinion, to think about buoyancy reserves. You have already foreseen, it seems to me to recall, half a meter of freeboard, which is a large reserve. What you should do is create watertight compartments so that a hole in one of the hulls, or a hole in both hulls, does not cause the house boat to sink. It is my opinion, as rebuttable as any other.
    By the way, the alignment of the structural elements seen in the large picture seems very adequate.
     

    Attached Files:

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  12. fallguy
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    fallguy Senior Member

    If you do not at least rake the forward edges of the hulls; when the boat is being towed, water will splash over the tube fronts and perhaps run into the cabin. Towing may also be more difficult, but it is not my business. I know that it would be more difficult to tow for a skiff.
     
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  13. fallguy
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    fallguy Senior Member

    he had gone from cylinder to rectangular
     
  14. TANSL
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    TANSL Senior Member

    I agree with you but only by knowing the SOR of the boat can the correct choice of shapes be made. The rest is talking for the sake of talking.
    Cylindrical or rectangular? : whatever is most convenient for him to manufacture.
     

  15. fallguy
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    fallguy Senior Member

    It is a floating home. To be towed from point A to a permanent slip.

    Metal hulls more likely and weldable for crossmembers, etc.

    1/4" ply wall sheathing
     
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