CLT houseboat

I think it would be best if you started prioritizing requirements. For example if the houseboat it to move often it's simpler for it to be selfpowered. And please stay realistic. For the price of a tow over the Atlantic you can just as well buy another boat at the destination. Regular boat transport service exists for a reason.
Make a sketch of the thing in different materials and start asking people prices.

 

It does not need to move often. The cost of maintaining a large vessel that can move under its own power legally, is very much prohibitive over here; and there is no way my oddball vessel will qualify for those anyway. Houseboats are comparatively completely unregulated however. Movement within dutch or maybe european coasts and its river systems is the most likely scenario. Ive got a reasonable idea of the cost of that. I know its not cheap but neither are realtors and sales taxes. Not sure of the cost of towing to another continent; not a regular request I suppose.

That would be an excellent idea if I had an intention to get myself a boat right now, rather than a desire to discuss the practicalities of this specific boat design.

 

Ok, then back to the CLT. I propose wood, a little fiberglass (under 1mm or so) in epoxy and steel plates for protection screwed on (screws in epoxy bungs). Mild galvanized and painted steel is perfect for this, no need for the expensive stuff.
But i have to say that for not a lot of more money there are better materials to be had when considering the overall costs from cradle to grave.

And for moving a small tender that functions as a pusher, 5m boat with 400hp of diesel.

 

Dunno; if I can pay a few k extra, and for that money I literally never have to worry about painting even after dragging it over a bunch of rocks, that seems like an investment worth considering. But sure galvanized steel would also go a long way. Why do you think mechanical fastners are preferable? Undoubtly cheaper; many buckets of marine grade adhesive are not cheap. But when SHTF and you actually need those plates, I worry that mechanical fastners will concentrate the load and quite readily tear out of the wood.

I was thinking of the possibility of owning a small pusher myself. Perhaps that would be affordable and feasible from a regulatory perspective; though I imagine the professional licensing requirements would kick in once id start using it to push my boat anywhere near commercial shipping lanes... but if I do want to do something crazy like actually take it across the atlantic, it might be an interesting option.

 

Wrt adhesives; m3 5200 was one of the first things that came to mind and ive heard of it being used to permanently stick other things to hulls. But it sells for something like 40e/L, you cant put it on very thin, and youd spend 20k on that stuff alone if not careful.

PVB resin granules sell for 4e/L, and might be an equal or better solution. You can use this as a hot-melt adhesive, so I think itd be easier to work with, since you can correct mistakes, and have a way of taking it off again should the need arise. Its stronger than the underlying wood anyway so a stronger adhesive wouldnt really add value. Should be easy to cobble together an electric oven that goes up to 200c, put a sheet in there with a layer of granules on it, and then press it to the undersize of the vessel with a jack. To rip a 1m2 plate like that off again, you need to rip a 1m2 layer of wood along with it. Thats hard to beat with mechanical fastners.

 

I have never used PVB so can not comment on it. I like mechanical fasteners the same reason I like galvanized steel. Cheap and proven. I don't actually know of any adhesive approved for underwater use to hold metal to wood or fiberglass structurally. Above water yes, there are some, but not cheap. As for not needing painting, you will have to antifoul the bottom regularly anyway.

I am curious what is the difference between owning a barge with a motor that is used as a houseboat and a houseboat without a motor if they are both under 24m? A barge under 24m is a pleasure vessel just like any other.

 

Not going to bother antifouling regularly in case the thing is sitting still for years. I guess id only bother as prep for longer trips. m3 5200 and similar have decades of track record glueing all kinds of boat hardware together above and below water and the only complaints ive heard about are the trouble you are in if you ever change your mind about these things needing to be stuck together. PVB is everywhere nowadays, from wood varnish to the glue holding bulletproof glass together. On paper it should be great for this application, it adheres great to metals and is mould and water resistant. But cant find any precedent of it being used in a similar manner as m3 5200, so the safe bet is to just find a good deal on the proven marine adhesives I suppose.

I imagine it depends a lot on locality. Getting a licence to operate a boat this size isnt that hard over here. Getting it classified as a boat is the hard/expensive part I think. There are many people living on old converted river barges in my neighbourhood, but maintaining a status where they are allowed to move the thing around themselves is generally not considered viable.

That being said, should the proverbial zombie apocalypse break out, a little pusher is going to be worth a lot more than any license would.

 

As a reference-sanity check for the cost of metal-plating the hull; a 1mm 300-series stainless steel roof of a 100m2 or so costs about $10k as installed, in the US, of which only about 1/3 is material costs, and the rest labor/overhead. Duplex is only marginally more expensive by weight than 300-series stainless; and getting this done in a low-cost country, I think around 10k for a few mm of installed duplex steel is in a realistic ballpark. If it is really necessary is another question; but the way im thinking about it is to leave it as an upgrade option; just stick with glass and/or urethane initially as long as im parked in a boring zoned houseboat location, and should I wish to get more adventurous and relocate to some rocky tidepool in the middle of nowhere, it is good to know that such upgrade options exist.

The main obstacles to using stainless more in boat construction seems to be that 300 series has poor strength per dollar, and isnt so stainless that you can just throw it in seawater unprotected anyway. Duplex is much more competitive in strength per dollar; but still a lot more expensive than carbon steel, and nowhere near as formable or weldable. There is a big chance of nullifying your strength or corrosion advantages with your welds, which takes out a lot of the appeal as a boat building material.

As it happens, I could hardly care less about formability or weldability when glueing some plates to an already polygonal hull.

 

I think whatever strength and toughness you aim to get with steel plates, you can equally get with fiberglass and aramid/kevlar and epoxy. And lighter and easier/cheaper to do in one go - since you'll need to encapsulate the wood anyways.
From what I've read stainless steel will continue to rust in saltwater. So there seems to be really nothing you gain over normal painted steel.

I've read an article somewhere about building the bow of a catamaran (or trimaran?) as a kind of detacheable foam structure. So if you hit something it acts as a crumple zone to absorb the impact and will come off at a designed breaking point. But I believe that is really only useful for a fast ocean cruising vessel. If you actually manage to get a dent in your fiberglass from a tidepool (unlikely?) it's easy to repair.

 

Typical stainless grades dont do that well in seawater. Duplex steel is used uncoated in sea water pipes, pumps, heat exchangers, and the like, and even in warm, chlorinated and acidic water, it does great. In normal seawater, it is basically inert.

If I put on a ton of composites as an outer skin, like a bunch of mm, I dont think that would crack readily, true. The steels im looking at here are much harder than any composite (10x the yield of glass), and have 25-50% elongation until break (10x of glass), so on a per-mm-basis, its absolutely no match in impact resistance. Probably glass would be cheaper per mm built up, but if you get fancy with kevlar I am not so sure. Sure the steel is heavier; but im ok with that.

Well define easy. It would still involve a drydock I imagine.

With a few mm of hard steel on the bottom, backed with a solid slab of wood, you could basically pull this thing onto land with a winch anywhere. I kinda like that idea. Even with the best composite construction, you wouldnt do that unless you are fine with at least superficial damage.

 

And you're right, ships out of shiny stainless duplex steel are actually being build! A boat with a mirror finish would really be amazing.

But the relevant numbers are per weight, per cost and also per labor to manufacture. And btw aramid isn't that expensive.

Why not just attach some old truck wheels to the side so you can drive onto land? Or maybe wooden wheels - that are plated with stainless steel of course

 

Well no arguing taste I suppose . Only thinking about using it on the bottom right now, but you could do a thin gauge on top as well. Above water I have many ideas but it doesnt really matter since its not central to the concept. There are some cool zinc and corten clad houseboats in amsterdam near where I live; I think their weathered look is really cool. Another thing that came to mind is glueing on thin scales of titanium anodized in different colors so the whole thing would look like a dragon out of an LSD trip.

Yeah you are right. If there is no foam on the bottom of the hull but its sitting directly on the solid wood, that would be a fine option for all intents and purposes. Even a few mm of glass, when it cant flex and be dented easily, would already serve all but the most of my exotic purposes, and if I am not making things difficult enough for myself in getting a CLT structure delivered and assembled in a boatyard, its pushing my luck to also add another experimental process on top. Pretty sure ill delegate the steel plating to the 'possible later upgrades' bin.

Another construction detail I didnt want to get into so far; but id want to have a cooling channel routed in the bottom hull, so I can run a heat-pump inside coupled to the nice and stable temperature under the boat. However, running the numbers on the thermals of that; id pretty much need to put 1 or 2 mm of aluminium sheet on the bottom as a heat spreader anyway, to make this efficient, and not have to cover the entire bottom with tubing. Ideally I could get this arranged with the CLT factory and have them press that alu sheet nice and consistently onto the bottom panels with their presses. But if im going with that extra expense the external duplex is even more overkill. Just glassing over that to provide a continuous barrier and for corrosion protection of the alu would be pretty solid I think. I dont think a tiny crack in the glass getting a wee bit of moisture on the alu would lead to some kind of runaway corrosion delaminating the glass from the alu like you might get with steel. But I could be wrong about that... alu and glass is a pretty common laminate combination in many industries tho so there should be more info I can find about that.

You joke; but steel clad wood is the OG of wheel technology. That said if I wanted to add the complications of a bunch of 100t-rated axles and underwater bearings to my boat, I think id go with the more modern rubber tires there instead.

If, that is.

 

Well speaking of corten steel, using old banged up 40' shipping containers might be an interesting way to build a cheap barge. You'd need to cut them up a little and weld them back together, but in cost/tonne I think they could be cheap. Maybe 1000€ per ton isn't that cheap. And you would need to weld new steel sheets to form the hull surface. Ok I'll stop now, probably not worth contemplating haha.

In regards to your water cooling idea you could just drop a kind of radiator with connected tubing in the water. I'd think for a cheap AC in the tropics that might be a good method.

 

Keeping a compact and thus finned radiator submerged in non-pool-water from clogging up is a rather high tech endeavour. Instead of a compact radiator you might just throw out a big loop of flexible tubing once youve anchored somewhere but thatd be a little janky and it wouldnt work when on the move.

Note that its not just for cooling; if its -10C outside, water at 1m depth is typically still liquid and above freezing. A heat pump can draw heat out of that icy water (still 273C above absolute zero!), and easily give you 3kw of heat for every 1kw of electricity you put in.

 

Made a little sketch to get a sense of proportions. This is 24m LOA, 5m wide, 5.5 from bottom to top, with 20cm thick walls throughout. It has about 160m2 of floor space, and about 50m3 of volume for fuel/water/batteries/whatever under the bottom floor.

Without internal walls, this would come down to about 100m3 of CLT, for about 50t. As currently draw it could be assembled from 20 panels. At 500e/t, thatd be 50k of CLT. It may end up higher since i want all panel edges to have interlocking joints machined into them, and they need to be glued together to a higher standard than regular CLT housing construction, which is typically just screwed together.

It should be possible to glue this all together in the dock in a few days. Next, alu and glass on the bottom, XPS and a little glass on the other surfaces. Id think that including the windows and so on to make it watertight, I could get this out the dock for around 100k. But if I am being unrealistic anywhere, please point it out.

Then there is everything else; kitchen bathroom hvac power flooring, you name it. That probably adds up to a lot more than 100k, depending on the details. But the savings made by not doing that in western europe but in a low cost country, will probably pay for the hull by themselves.