How can I simplify my house boat design for easier construction?

Discussion in 'Boat Design' started by LandFish, Jun 22, 2021.

  1. LandFish
    Joined: Jun 2021
    Posts: 21
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    Location: Norway

    LandFish Junior Member

    I am designing a house boat that I want to live aboard (in norway).
    It will most likely stay at a marina most of the time, but I would also like to cruise it along the coast line in kinda rough weather occasionally as I sometimes work in different cities that are near the coast and would prefer living in my house boat instead of staying in a hotel for three weeks.

    Width: 4 meter

    Height (including pontoons): 4.8 meter
    Height (not including pontoons): 3.5 meter

    Length (including entry platform): 12.5 meter

    Catamaran pontoon size:
    1 meter width
    12 meter length
    1.3 meter height

    [​IMG] [​IMG]

    I am probably going for twin outboard motors for easier steering.

    Fibreglass is a lot of work as far as I know. So only the red and black areas on the lower part of the boat will be fibreglassed (not inside obviously even though its red on the drawings). The rest will be constructed as a normal house. So that I also hopefully do not run into condensation issues.

    I plan on housing all technical stuff like water, electronics, etc inside the pontoons so that I can use the full area over the pontoons to live in.

    The black area on top are 6 x 400 W solar panels which as of now I think will be enough to also be off grid in the summer times.

    The house on top of the pontoons is pretty tall (3.5 meter). That is because I need to have good insulation on the floor and ceiling because of the cold winter climate in Norway, I was thinking 35 cm thick insulation. So the actual living height inside will be around 2.8 meter. The walls will have only 20 cm thick insulation.

    I have a question about flat roofs on boats btw. In housing as far as I know it is unwise to have a completely flat roof because water doesn't have a place to drain. However is my theory true that on a boat it is okay to have a flat roof because the boat is never completely standing still, thus always being able to drain off excess water?

    Just to make it clear, I have almost zero experience boating. All design decisions I made are based on things I've read or heard from boat owners. I just want to fulfill my dream of escaping land based living and the housing market.
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    35cm thick insulation ? Seriously ? If it is that cold, surely snow on the flat roof could become a problem, as it builds up, not as an insulation problem but as unwanted weight.
    Last edited: Jun 22, 2021
  3. SolGato
    Joined: May 2019
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    Location: Kauai

    SolGato Senior Member

    It’s not clear if you are looking to simplify to save money on construction, speed up the process, or make it easier to construct for a novice, or all the above.

    Since you are dealing with mostly flat panel construction above the water and are interested in fiberglass construction, you might want to explore products like ThermoLite which is a pre-engineered fiberglass sheet material that is used in boat construction in place of plywood. It can be cut with basic power tools, bonded or glassed together, painted or gel coated, etc.. and it weights less and is stronger than its equivalent in marine ply, and it doesn’t absorb moisture so you don’t have to worry about rot.

    A lot of boat builders here in Hawaii are using this material to build out everything above the waterline, pulling the hull shape from a mold, then using it for everything above from the decks, to cabin, to bimini because it allows them to build very quickly, and they end up with a consistent strong structure.

    It’s not cheap, but then again if you’re not skilled at fiberglassing or don’t have a good environment or space to work in and are looking to build fast, it might be worth the added cost.

    Just something to think about.

    Here’s a link to some products to give you an idea of their properties:

    Thermo-lite Board Product Line
    kapnD and bajansailor like this.
  4. clmanges
    Joined: Jul 2008
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    Location: Ohio

    clmanges Senior Member

    Two words: Arctic Circle.

    Really, though, I don't think I'd worry as much about the snow on the roof as I would about ice crushing the hull.

    Also, that's not a shape of craft I'd want to be on in anything approaching "kinda rough weather".
  5. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    The entire boat looks like it could be built with a carpenter's square. Maybe a barge ramp pontoon bow would be faster, but you'll get a little hull slap.
  6. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    35cm does sound ridiculous to me, if the weather is that bad, why would you want to be in it ?
  7. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    That boat is not capable of rough seas.

    Before worrying about construction complexities; I'd work on defining the hulls, addressing windage, etc.

    Most houseboats here in the US/Canada are not operated in 2 foot seas. They are notoriously difficult to deal with to windage.
  8. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Even in summer the seas along the coast of Norway can get very rough indeed. And that little shoe box which you have sketched will not be happy at all when it encounters conditions like this.

    If coastal travel is a definite requirement, you would be much better off simply buying a reasonably seaworthy motor boat - this will still have plenty of room for living on board, and buying an existing boat second hand will probably cost much less than building a new houseboat now.
    Here is a typical example of a nice Scandinavian semi-displacement motor yacht for sale - this is just for illustration. You will find literally hundreds of other types of motor yachts in this size range (I arbitrarily chose 9 - 12 metres).
    2007 Nimbus 340 Commander Power New and Used Boats for Sale -

    But if your heart is still set on developing further the design shown, how much further have you got?
    Have you sketched a rough general arrangement for the interior?
    Have you calculated what her displacement might be at the waterline shown?
    Have you carried out a preliminary weight estimate re the weights of all the construction materials and outfit items (including propulsion gear) that will make up the boat?

    Your electronics will not be very happy if you stash them away in the bilges of your boat, and they will probably complain of maltreatment long before their friends that are kept at the helm station.

    You could allow for some camber (say 75 mm / 3" across the 4 metres of beam) on your roof, and then it should be easier to lay down the roof panels, it should be slightly stiffer (compared to a totally flat roof), and it should still be possible to install solar panels as shown.
    DogCavalry likes this.
  9. latestarter
    Joined: Jul 2010
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    Location: N.W. England

    latestarter Senior Member

    Viewed from England it is not surprising.
    15 years ago I upgraded my loft insulation to 25cm of fibreglass quilt which was the minimum at the time.
    The insulation standard has since been increased by a further 25%.
    Regarding build up of snow in your previous post, the design loads for roof structures take account of that.
    Looking at the opposite end of the temperature range, I do not know how you survive your heatwaves.
    DogCavalry likes this.
  10. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    These 10 degree C mornings are cool enough for me ! Heat isn't too bad, but heat combined with high humidity is.
  11. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I designed my Skoota rooftop for 100# point loads and made some anti-buckling wall intersects specifically for snow loads if I kept the boat wintered in Wisconsin. But then we bought land in Texas.

    Sorry to be a dream killer here, but I recall our honeymoon in BC. We were on Pender Harbor with a 16' skiff and the winds were heavy from the south. In the fjords, it was nice, but exiting them was hairy and we only had to go 100 yards. Seas were 4-8 feet in the Strait of Georgia which is not even open to the sea.

    I have been on houseboats about 15-20 times in my life and never would I want to be in 4-8 foot seas. You'd end up staying in the fjord until the seas calmed. In our case, it was 3 days. Never saw a boat go out in it, but we skipped between the harbor and the fjord to the north.

    The Skoota 28 would have been capable of such seas, but not the groom without dramamine.

    There is a reason you don't see houseboats cruising the Bahamas. It is too windy and rough for them.
    bajansailor likes this.
  12. Iridian
    Joined: Jan 2020
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    Location: MD

    Iridian Junior Member

    I would not ever take a boat like this offshore. I'd hesitate ever taking it across anything larger than a bay.
  13. LandFish
    Joined: Jun 2021
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    Location: Norway

    LandFish Junior Member

    Hi all! Thank you so much for the feedback and the reality check.
    It seems pretty obvious that I need to rethink the design completely to get more in line with what I need.

    To all of you that think 35 cm is insanely thick. It is the bare minimum required for roof insulation in Norway when building houses nowadays (although it depends on R-value of the insulation type).
    I've been inside some house boats that only have 10 cm in the walls and 15 in roof/floor. So it is probably livable as well. There are no rules when building boats, I just wanted to be safe about it.

    Sorry that I was a bit unclear on this: I was not planning on building it myself, but having a boat builder build the shell for me and do the interiors myself.

    I have sketched out the interior:
    Bathroom to the left. Then kitchen + sleeping room. The rest is the living room. Hybrid pellet/wood stove in the living room.
    The red part is raised about 40 cm and is a big storage space inside.

    And I have also started calculating overall material use, weight of individual items inside the boat and so on, but there are still lots of unknowns at the moment.

    A while back I tried to draw up a frame for the boat so that I could estimate material use. With this drawing approximately 730 meter of framing material is used in building the frame.

    On a different note:

    There is a ferry boat in Fredrikstad, Norway that I would like to get your input on. I like the way it looks and it is spacious inside and very shoebox like.
    I think something like this would suit my needs also. If I built it a bit smaller. It is currently 13.5 meter length, 5.4 meter width, unknown height.
    Do you think it would handle rougher water? I assume it is designed to only be cruising on the river that runs through the town. But it looks pretty sturdy.
    [​IMG] [​IMG]

    Here is an early drawing of the ferry that I found. I don't know how accurate the hull is compared to the final version of the boat. But I assume the hull is somewhat flat like in the drawing.
    DogCavalry likes this.
  14. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    35cm of glass or rock wool for houses is lower end in the ceiling/the attic (in Finland). 50cm not rare.

    But on a boat Xps or urethane could achieve similar insulation at fraction of the thickness.

    But yeah, even little bit rough seas, Atlantic coast and that boat don't seem like a good combo.

  15. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    OK, well glass "batts" wasn't what I was imagining, I was thinking polystyrene, and as you say, a fraction of the thickness
    kerosene likes this.
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