CLT houseboat

Discussion in 'Boat Design' started by Eelco, Apr 11, 2020.

  1. Dejay
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    Dejay Senior Newbie

    Nope, I just watch this guy building a steel roof for his container castle for inspiration :) But a barge is also much easier to build than either of those. I'm sure you could find a good price for having someone welding together only the bottom hull of a barge. Same would go for building with glassed plywood, without much curvature it should be rather easy to build.

    You probably should also build the house on top of the barge using lightweight materials. Maybe a custom run of SIPS made out of thin 6mm outdoor grade plywood and XPS. I wish there was a good way to vacuum infuse fiberglass on plywood. Or even vacuum infuse a complete SIP wall. I've considered various crazy ideas for this. Like build a large 10m x 3m table mold and put fiberglass, 6mm thick and 30mm wide strips planks, XPS with flow channels cut in and more wood strips and more fiberglass on top. And 20x80mm wood beams on the border and in intervals. That could be very lightweight, plenty stiff and tough and you could vacuum infuse a huge panel with a final finish. Maybe even transparent varnish.

    So you're not alone thinking about creative new ways to build boats, but for the hull I wouldn't mess about.
     
  2. Eelco
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    Eelco Junior Member

    Yeah ran into his videos before. Pretty cool project; but with a bunch of guys working for years and at least as much heavy machinery, im not sure id call it 'easy'.

    Dunno; I want something you could take onto the open ocean; and that precludes most steel living barges, if youd ask the people who are attached to them at all. A typical river barge without much freeboard or the bending strength of a stiff superstructure, could easily buckle if hit by a big wave.

    If im going CLT, I think I might as well go CLT all the way for simplicity, including the second floor. No its not the lightest form of construction; but this boat is only 5-6m from keel to roof, and open ocean waves can get bigger than that. I kinda like the idea that it could get capsized, float just as well when upside down, and be self-righting. Again more a theoretical-aesthetic concern than a practical one. But in general my philosophy is that I dont want to prematurely optimize for weight. This thing doesnt need to be competitive in hauling freight; it needs to be a solid and comfortable house first. As long as towing it someplace else doesnt become prohibitively costly, I am ok with that.

    Just defending the idea here for arguments sake; not sure id make a downpayment myself yet either.
     
  3. Rumars
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    Rumars Senior Member

    5-6 meter waves, capsizes, etc.? You need to scale down a little. A normal houseboat will have normal sized windows and doors so your weak point is whatever you fit over them while towing and how waterproof that cover is. You want such capabilities you are better off designing a seagoing hull instead of a box.
    Material choice is simple, you prioritize your desires and see what fits and what can be improved by combining materials. From what you have described so far only Al fits all your requirements. Paying for it is another thing.
    I would say you need to do some research on the different materials and their prices.
     
  4. Rumars
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    Rumars Senior Member

    Why do you think infusing glass on ply is hard? If you are doing one sided infusion you seal the bag on the ply itself (on the other side) if infusing both sides at once the bag looks like an envelope and you have resin feeds to both sides. You only need a table for thin ply, thicker ply is self selfsupporting. SIP's are made with vacuum all the time, plywood, glue, foam glue, plywood, apply vacuum. Presses are used in high volume production, custom SIP's are vaccumed.
     
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  5. Eelco
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    Eelco Junior Member

    If you want the ability to cross oceans, and you dont want this to be an excercise in russian roulette, even if you pick your seasons, you better be prepared for multi-meter worst case waves, yes. If by some freak accident those suckers break on you (can happen even in deep water), you are going to find yourself with a nice test of the exact range of stability of your vessel. Do I need to scale down a little? I am open to reasoned arguments to that effect; but what I am telling you is that you can afford a vessel that will be capable of shrugging off an open ocean wave breaking on top of it, by building your superstructure out of a fat slab of CLT as well.

    I was thinking of thick PC sheets that can be installed before all glass during towing. Also, probably no windows or other openings on the bottom floor. The bottom floor would be in large part below the waterline and having a window just at the waterline would just look weird and get gunked up with duckweed in notime, I imagine. Was thinking more of a split-floor design (or perhaps mezzanine is the word im looking for?) to bring some daylight into the parts of the bottom floor that might want it.

    I dont see Al being used that much other than in rowboats and I am not very familiar with its properties. Do you have any link with information pertaining to the cost of newbuilt Al hulls?
     
  6. Eelco
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    Eelco Junior Member

    Did some more looking into foam cores; XPS would be about 8k to cover the whole thing in 12cm (first, non-bulk price I could find). Not a big deal; and youd pay the same to get a house of that size isolated to that standard.

    The cheapest structural PET foam I could find would be about 20x that for the same volume of foam. Id only put that on the bottom half, so lets say 10x. But thats still about 80k in foam. Could compromise on the r-value a little; max temp diffs with the water are more modest anyway than vs air... but yeah not a trivial expense.

    Now building a foam core boat in XPS is generally not recommend for its lower strength; but its only about 6x lower than structural foams it seems. Frankly I think I can get away with it here. The only reason shear strength is sought after in these foams is because you need it to get bending strength/stiffness in your sandwich panel. But you dont need any bending strength in your sandwich panel if its backed by 30cm of wood. Sure in an impact scenario that 6x would be quite welcome. But for 80k I can get my boat towed to a yard and get a section of XPS replaced quite a few times.

    EDIT: finding some conflicting figures; but now id say highest density XPS has about half the strength of a medium grade PVC foam which is still 7x the cost. With half the stiffness but a monstrous 12cm thickness by foam core construction standards, it should still be able to absorb more energy on impact than is typical for foam core.
     
    Last edited: Apr 15, 2020
  7. Rumars
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    Rumars Senior Member

    XPS is great if you want to pour a slab of cement over it. In a sandwich it will delaminate instantly, that's why nobody uses it for anything important. You can make light furniture with it. It is also a rigid foam, so any impact will crush it permanently. The good news is it's waterproof so water will not get to the CLT unless it is ripped away. Still a waste of money on the outside in my opinion.

    I have no recent info about how much an Al hull of that size will cost you. Probably ~200k depending on scantlings and who welds it. As for what it is used for well, one of the better known yards using it is the Royal Huisman, and they don't build rowboats. Just ask google to show you Al dutch and french boats. The Netherlands is actually a hotspot for Al building (workboats also, not only superyachts). You have probaly seen plenty of Al boats without realising it, painted they look just like any other boat.
    You need a sketch with scantlings, then you can request quotes and see how much is asked for your specific design.
     
  8. bajansailor
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    bajansailor Marine Surveyor

    Eelco, please do take note of Rumar's sound advice re building in aluminium. In the long run it will most probably prove to be the most economical, require the least maintenance, and be the least stressful, especially so when compared to these various sandwiches that you describe above.

    Similarly for ocean passages - if you want to get your houseboat to the other side of the Atlantic, what are you planning on towing it with?
    I think you will find that (in the long run again) the cheapest, easiest and least stressful way of doing this will be to carry it as deck cargo on a ship.
    And yes, I have been caught out at sea on a yacht in 9 metre seas with the wind blowing Force 10 gusting 11, so I have a good appreciation for the power that is contained in these waves - especially when they decide to dump on you. No matter how strong your houseboat is, it is not going to like it if you (try to) tow it in these sort of conditions.
     
  9. Rumars
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    Rumars Senior Member

  10. Dejay
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    Dejay Senior Newbie

    But for stability, wouldn't you want the weight in the hull, not in the second floor? As low as possible. You could build a barge hull with sealed compartments, maybe 50cm high. Very stiff. Then build lightweight with something like SIPs. Sips would be very buoyant so the boat would be self righting if it flips over. As long as the hull compartments are sealed.

    And really welding a 15m x 5m x 0.5m big steel box with a grid inside for sealed compartments is pretty easy. You're not working high in the air and you're not welding things at odd angles and all the pieces are very uniform. Of course you would need equipment to lift the plates and something to flip the hull over. I can't imagine any other construction method getting any easier and faster than this in terms of working time. Unpainted aluminium is the ideal in terms of maintainance and I also love the look.

    You could have as much freeboard as you'd want - I image. Like a solid railing a meter above the barge top. Well I don't know what you're imagining, I'm thinking the first floor would be a bit like some of these mississippi riverboats where the first floor has a walkway around the sides and the second floor would be the full width.

    As far as ocean crossing? Is that even remotely feasible with a barge or a raft? I assume you mean something like crossing the canal to England or towing along the coast?
    I think a barge is theoretically very stable like a flat raft on the water - as long as the top is very light. Just very uncomfortable for motion and seakeeping. And with two floors it would have insane windage and could easily tip over in a storm.

    I mean is it in any way realistic that a 5m wide houseboat (even with a single floor) could be remotely seaworthy? Maybe you could have "slide out" amas so your barge turns into a trimaran haha. Hmm well, if you start with 3 pontoons maybe that is something that could actually work?
     
  11. Dejay
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    Dejay Senior Newbie

    Ok just for shits and giggles... a sketch I made a while back for a 12m x 5m catamaran, for maximum internal floor space as a floating apartment. I was playing with ideas that are easy to build, have large flat roof space for 8kW solar panels and the shape is somewhat more aerodynamic than a typical houseboat. It should be much more mobile and have better motions at sea than a barge.

    The idea here is to use vacuum infusion to build very lightweight foam core structure, similar to the intelligent infusion of the harry proa. Something like 800gsm with 3cm foam. The hull and the roof sides are symmetric front/back, left/right and top/bottom. So you'd make a relatively easy to build half mold and vacuum infuse 8 times. You could attach external walkways and remove them when going through a 5m canal lock.

    Sundog v20 2.jpg Sundog v10.jpg

    I probably should mention that I'm just a novice and trying to learn ;)
     
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  12. Eelco
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    Eelco Junior Member

    Thanks, thats a great find. PU coating also was the simplest solution that came to mind for me; and for a purely static houseboat, why not? Then again houseboats can have other boats crashing into them... will keep a bookmark to see if they further develop and test the concept.
     
  13. Eelco
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    Eelco Junior Member

    Perhaps; ill look more into it. ITs not the most popular option for houseboats exactly while it has had plenty of time to prove itself; but then again im not looking for a typical houseboat so that logic may not hold.

    Transport on another ship is an interesting idea. Not counting on anyone liking such a voyage; id settle for making it across with the hull intact. Obviously preparing it for such a voyage would be no small amount of work, fastning all furniture etc.
     
  14. Eelco
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    Eelco Junior Member

    Yeah, something like that. I think almost full width on the second floor, but a little fore and aft deck to keep your ropes and cleats and stuff.

    Yeah, plenty all kinds of hull shapes have crossed the oceans. By 'seaworthy' I mean 'stays in one piece'. Not 'provide the most comfortable ride' or 'get great fuel economy'.

    The V-hull would be filled mostly with tanks, batteries, and other heavy equipment. Some 20% of the total weight would be right there at the bottom. Probably the design of the superstructure can be lightened somewhat compared to the bottom, but with a quite round 5x5 octagonal-ish section, you may not even need it to be self-righting.
     

  15. Eelco
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    Eelco Junior Member

    Looking at the stress/strain curve for high density XPS and PVC they really are not that different. They both get into plastic deformation at a few % strain; PVC just is stiffer overall. So yeah it will take a 2x harder bump to cause permanent crushing, but it hardly strikes me as a fundamental difference.

    Fully crushing a 700mpa foam over a 1m2 section would absorb about 50kJ of energy, if you look at the area under its stress/strain curve. Thats the same amount of energy as a 100t boat moving at 1m/2, or 2knots. Thats kinda cool; anything structural would be completely shielded from this impact, that would likely put a nice dent in any steel or alu plate construction.

    But yeah not super convinced about the exterior foam. Any kind of contact with the ground for a boat this heavy will result in crushed foam and a cracked external skin; and thatd be true regardless of what foam is used, pretty much. Everything except a very soft grounding over a large area would pretty much cause the same inevitable result.

    Starting to come back to my m5200 glued on duplex plates again, at least on the bottom. Dont really need the extra R-value there anyway; max dT with water isnt that big, and the bilge wouldnt be living space anyway but be seperated by another floor. You cant really beat duplex for a material youd happily drag over a bunch of rocks without wincing, I think. Building a full boat out of duplex is kinda expensive but buying 100m2 of 5mm plate to glue onto my keel really doesnt seem to be that crazy an outlay. 5k, excluding shipping and import. I feel I must be missing something because honestly I dont see why everyone isnt doing this... according to duplex boat makers they are a huge lifetime cost saving due to zero maintenance; but thats what theyd say ofcourse and in the meanwhile it hasnt really caught on it seems... but just as a cladding on the keel as im contemplating it likely to be economical sooner than using it as structural material everywhere.

    Thanks. I need to find out more about how it performs in fresh water in practice.
     
    Last edited: Apr 16, 2020
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