Need Advice with Houseboat Construction

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

  1. SNGPSo
    Joined: Feb 2021
    Posts: 16
    Likes: 2, Points: 3
    Location: Oujda

    SNGPSo Junior Member

    Hello everyone,

    I am an intern architect and I am building a houseboat on a budget. The houseboat is 14m x 5.5m (46ft x 18ft), including a balcony that goes all around. The interior space is 10m x 3.5m (33ft x 11.5), and the height is 2.85m (9.4 ft). The structure is a wooden deck with wooden walls. I designed it to be pretty small to help with construction difficulties. Please check the attachment for reference.
    Final Exterior Day.jpg

    [​IMG]
    Final Bed Day.jpg
    [​IMG]
    Since I am on a tight budget, I was looking into the possibility of using these HDPE pontoons for bearing capacity. I contacted them and they said the maximum diameter they have for these pontoons is 60cm (23.6 in) with a length of 90cm (35.4 in): Hdpe Pontoon Fishing Buoy Floating Pontoon - Buy Pontoon,Fishing Buoy Floating Pontoon,Hdpe Pontoon Fishing Buoy Floating Pontoon Product on Alibaba.com https://www.alibaba.com/product-detail/HDPE-pontoon-Fishing-buoy-floating-pontoon_1600094070499.html?spm=a2700.galleryofferlist.normal_offer.d_image.648d3febgrixGK&bypass=true
    dimensions for houseboat.jpg
    What would be the weight for such a boat? Can I safely use that HDPE pontoon with a wooden deck? I've seen people use aluminium for the base deck, but since my budget is very tight, I am thinking about using a timber base with sealants for protection.

    I would greatly appreciate any help!
     

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  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum SNG.

    Only you can determine what the weight for this boat will be - you are the person who is designing and building it.
    You need to do a very careful weight estimate of ALL the materials that has gone / will go into the construction of the house boat.
    And then add on the weight of the full fresh water tank(s), and also the full tanks for grey and black water, if these are required in your country.
    Also the weight of all of the equipment, not to mention the weight of the crew and their personal effects - it all adds up very quickly.

    Re the hull for your boat, a catamaran form would probably be best, with two hulls / pontoons.
    Although it might have to be a trimaran configuration, depending on the sizes of the floats available for building the pontoons, and the final estimated loaded weight of the houseboat.
    The drums shown in your link look interesting - but how would you fasten or secure them to your house boat structure?

    If you can easily source discarded plastic barrels (standard size is approx 40 gallons), you could build two (or three) hulls using the concepts employed by the these folk with their Rolling Barge docks -
    Floating Docks | Aluminum Gangways | RollingBarge.com https://rollingbarge.com/

    But depending on the final estimated weight of your houseboat, you might need more than 2 or even 3 hulls - you might even need to build a complete barge, like in this link -
    Floating Home Platforms - RollingBarge.com https://rollingbarge.com/floating-home-platforms/

    You could also consider building a simple rectangular barge using plywood and epoxy.
    Or a steel barge - but this will need more maintenance.

    The bottom line here is that you now need to do a very detailed and accurate weight estimate, so that you know how much buoyancy you need to support your houseboat.

    Have a look also at the houseboats designed by Eric Sponberg - there might be some useful ideas there for you.
    Houseboats https://www.ericwsponberg.com/boat-designs/houseboats/

    Edit - re how your location is Oujda, Google tells me that this is 60 miles inland in Morocco - will you be using the houseboat on the Mediterranean Sea?
     
  3. SNGPSo
    Joined: Feb 2021
    Posts: 16
    Likes: 2, Points: 3
    Location: Oujda

    SNGPSo Junior Member

    Hello bajansailor,

    Thank you so much for the information!

    I work in Autodesk Revit and calculating the exact weight of the houseboat is possible. However, I would have to figure out how to go about that, as I never had to calculate the weight for any traditional architecture work I did.

    I think I will follow your suggestion of building the simple rectangular barge with plywood and epoxy. That would be the most cost-effective option for me, I think. I was contemplating using the HDPE barrels just to be safe with any potential leaking that may occur, but with enough hull subdivision, I think the result can be pretty safe. I assume, in this case, that the only variable I can use to control how much buoyancy I need would be the height of the barge (and how much air is trapped inside it), right?

    I am planning to put the houseboat in a city called Saidia; a beach town that is 1-hour drive away from Oujda.

    I have been working as an architecture intern for a little over 2 years now. You can check my LinkedIn if you like: https://www.linkedin.com/in/amine-el-kaddouri-9471a514a/
    But I am in a point in my life where I want to try out new things, and this houseboat construction might open up new possibilities.

    Thanks again for the reply!
     
  4. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    Not really. What you have to control is the volume of water that has been displaced by the pontoon. The height of the barge inside the water will be an indicator of that volume. The volume of air inside the pontoon will always be much greater than the volume of water displaced.
     
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  5. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Re calculating the weight of the houseboat - there is no 'easy' way as such - it is long and tedious - but the easiest way is probably to set up a spreadsheet.
    If you know the density of the material used to clad the house, and the thickness, and the total area, then you can calculate the weight of this material.
    Similarly with the material used for the structural framework.
    And if you build a plywood & epoxy raft for the hull, you apply the same principles.
    You will probably have to estimate the weights of some items in the outfit, such as the windows and furniture - but the important thing is to make sure that you have made an allowance in the weights for everything that will go into the houseboat.

    You also want to make sure that she will sit fairly level, ie you do not want one end to be significantly deeper than the other end.
    If you set up a spreadsheet, then you can include a column with levers, and a column with moments.
    Once you have calculated the weights of the individual components, then choose a suitable datum (either end of the boat is good) and measure the distance of this item from the end of the boat.
    Multiply this distance by the weight of the item, and this will give you the moment.
    Do a summation of all the moments, and divide this by the sum of the total weights, and this will give you the approximate longitudinal centre of gravity (LCG) of the boat.
    As you are building a rectangular barge, the centre of buoyancy will be approx in the middle of the barge - if the LCG is in the same location, then the barge will sit fairly level.
    If you are building in tanks for fresh water, black water and grey water, try to locate them as close to the centre as possible.

    Edit - re how you intend to keep the houseboat in Saidia, will she be moored in the marina?
    Marina Saidia | marinas in Morocco - iNautia https://www.inautia.com/puerto-deportivo-marina-saidia-1370.html
    Do you intend to rent it out as a 'holiday cottage' afloat, or live onboard it yourself?
     
  6. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I don't like to see houseboat builders using pontoons. The main reason for using a barge is you get a LOT more displacement. Reserve can be done on the ends of the barge versus up the sides of an already undersized tube.

    Consider the simple case of a 60 cm pontoon. The volune of the pontoon is 900*pi*L or 2827*L

    A square box of the same size is 3600*L.

    The square box has 27% more volume. Oh, but not really.

    A pontoon submerged more than 50% is really not functioning. In fact, if I was on a pontoon more than 30% submerged; I'd feel like it were going to plow and I'd become nervous about performance and sinking. So, the volume of the pontoon is much, much less. At 50% submerged, 1414*L. At 30% submerged; you only get to about 20 cm deep. This is say around 1000*L or less than a third of the displacement of the square box. Oh, to be fair, we don't plan to sink the box to the top, but even at the same depth of sinking; the box offers more.

    Then add to that athwart! The pontoons are on the sides, but a barge goes all the way across. Suddenly, the barge offers 4-10 times the displacement.

    The only time pontoons make sense is if the boat is planned to be light and/or there is a demand for mobility in a boat design for moving about a lot. Or say, for a boat intended for beaching where the boat might get stuck easier as a barge.
     
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  7. SNGPSo
    Joined: Feb 2021
    Posts: 16
    Likes: 2, Points: 3
    Location: Oujda

    SNGPSo Junior Member

    Thank you guys for the replies.

    Yes, I was thinking about using a spreadsheet and calculating the amount of each of the materials used. This will be a tedious and long process, as you said, but I will try my best.

    I already thought about the location for the fresh water tank, which is bellow the bed in the bedroom. That might pose an issue though because the bed deviates quite a bit from the center of the plan.

    What about the barge though? Can I use the space inside for grey water and black water tanks? The compartment for those can be placed in the middle of the plan, which may assist with the levelling.

    I must admit that you can see right through me bajansailor . For now, it's just a small project, but if successful I was thinking of scale up the operation to create a holiday retreat. Marina is inside of Saidia. My brother has a boat over there (around where the '-3m' is on the map), and the location where I can put the project is around where the '-4m' is.

    Edit: Yes, fallguy, that's also what I was thinking. A rectangular barge is also much easier/cheaper to construct imo.
     
  8. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Many houseboats or floating homes use the barge spaces for gray and blackwater and fuel tanks. This keeps weights lower and offers some 'free' storage spaces. Care must be given to holing the barge as you don't want water getting in or she'll sink. There are many ways to achieve that. Compartments for the NOT tanks are watertight, buoyancy foam, etc. I profess ZERO expertise on this aspect of design, but you are fast seeing the benefits of barge hulls here.
     
  9. SNGPSo
    Joined: Feb 2021
    Posts: 16
    Likes: 2, Points: 3
    Location: Oujda

    SNGPSo Junior Member

    After scrolling the forum some more for additional info, I am going to start referring to the houseboat plan as she. You guys are already conditioning me... Har!

    I updated the base to a barge and subdivided it into sealed compartments, after looking at how ship hulls are made.

    The barge framing is covered with marine plywood, epoxy resin, fiberglass sheets, and another epoxy layer, respectively. The midsection is larger on purpose; that's where the 3 tanks are going for freshwater, greywater and blackwater. What do you think?

    The native file uploader is not working for some reason... here the link to the updated barge pic. Each color refers to an epoxy-filleted compartment: barge-update https://ibb.co/qWjfvRx

    Edit: I still have not made weight calculations yet because I wanted to have all the structural members' positions/thicknesses refined first, then calculate their weight/placements.

    Edit 2: I figured the previous update was a little over-engineered. So I removed some farming members and replaced them with plywood cross-sections. The compartments labeled 'A' are made to be larger to fit the water tanks as necessary. barge-update-2 https://ibb.co/d4y51bW
     
    Last edited: Feb 6, 2021
  10. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Apologies SNG, but I am a bit baffled by your 3-D drawings - do you have any plain 2-D sketches that you can post?

    In your first post you had mentioned "I am an intern architect and I am building a houseboat on a budget"

    Are you at liberty to disclose approximately what your budget is?

    And are you planning on building everything yourself?
    Be aware that there is a LOT of work involved in the hull construction alone, never mind all the outfitting later on.
     
  11. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    @SNGPSo You should already make an estimate of weights to verify if the volume of the barge is adequate or is too large. You must play with the necessary volume under the water and with the freeboard (distance from the water to the deck) that you want to have. Maybe, I'm just saying maybe, two pontoons is not so crazy because, maybe, a single barge supposes a very reduced draft. It will help you know where to place the various equipment so that the boat has zero trim and list. All these things should be checked before you make the final decision on what shape the float (s) will have.
    The weights and their Cogs are of vital importance, already at this moment.
     
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  12. SNGPSo
    Joined: Feb 2021
    Posts: 16
    Likes: 2, Points: 3
    Location: Oujda

    SNGPSo Junior Member

    Sorry about the quick drawings bajansailor. Here are 2 sections for a clearer picture:
    [​IMG]
    [​IMG]
    I would never be able to build it just by myself hahah. I have contact with someone who does wooden construction for a living, and some plumbing and electricity guys. My current budget is around 50kUSD, which I think should be more than enough to construct a small boat since everything is relatively cheap around here. I also have to take the houseboat for inspection before I am allowed to put it in water.

    Alright, TANSL. I will start calculating the weight asap. I am aiming for a 45cm (17in) freeboard. So, do you think I should open up the middle section to increase the draft distance?
    [​IMG]

    Thanks guys!

    Edit: Also, do you think that 2 pontoons connected in an 'H' would make sense (for tank placements)?
    [​IMG]
     

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  13. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I think there is no need to do the "H" configuration that you propose. Additionally, tanks can produce a destabilizing effect that is proportional to their width. For this reason, it is preferable to make tanks that are longer than they are wide, which will undoubtedly fit inside the two symmetrical hulls.
    Try the typical configuration of a catamaran: two hulls joined by a transverse structure. But beware, I'm not saying that the solution for your boat is the catamaran type.
     
  14. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I think it is too easy to confuse what @TANSL is saying. He is saying calculate weights first, so you know the needed displacement. Otherwise, you are carting before the horse.

    Based on what I see, a barge will be needed, but how much barge is an obvious question.

    You determine the weights and then determine the hull. Not the other way around. Otherwise, you are designing the superstructure to suit the hulls which is very expensive. Consider this error...my hulls are too small and now I need to use exotic ultralight materials and processes to make the house light, etc.

    Your budget is pretty tight. I am assuming you plan no engine and it is a float home? For a budget of 50k, there are some commercially available small houseboat plans for say 27 footers. Sorry, but a new 50 horse engine and the systems to drive it are going to cost nearly 10k. This means batteries, cabling, steering, etc.
     

  15. SNGPSo
    Joined: Feb 2021
    Posts: 16
    Likes: 2, Points: 3
    Location: Oujda

    SNGPSo Junior Member

    Alright, I am currently calculating the weights of every material and we will determine the optimal hull design based on that.

    Oh no, I do not need/want any engine. All I want from her is to carry me around.
     
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