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I am wondering if it would it be feasible (at an affordable price) to 3D print a boat hull (small dimensions, maybe something like 60x40x20 cm).

I am mostly concerned about:

  • durability (against salty water, UV rays, extreme temperatures (under the sun or in a cold ocean)
  • strength (the material should be able to resist some chocs and maybe a little bit of pressure if a wave was to smash on it).
  • waterproofness

Those characteristics should last during extended periods of time in water (at least several months, maybe more, about a year or two).

Is there any easily accessible 3D printing material that would match those characteristics?

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  • $\begingroup$ Quick point to clarify, 60x40x20 isn't small. That's actually quite large for the printing world. $\endgroup$ – Hari Ganti Mar 17 '17 at 21:00
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You will really need to specify your constraints better because the short answer is yes, what you describe is entirely possible, but without knowing whether you are limited to a particular budget, process, or aesthetic, it's not a particularly useful answer.

Some machines (ex. Stratasys Connex 1000) will print models up to 1m in length, so sure, you could print an entire hull with the dimensions you specify.

Pros:

  • Monohull construction
  • Excellent surface finish
  • Many resin options are UV and salt water resistant with decent enough durability

Cons:

  • Ridiculously expensive machine with decently expensive resins
  • It will waste plenty of support material in printing (which means added cost too)
  • Not really easily accessible, but some design studios will have them and will print things for you, for a cost

Other machines (ex. Ultimaker 2 Extended) will print models up to 30cm along the vertical axis. It would require some assembly in the end, but you could segment your build and get a boat hull in the end.

Pros:

  • Easily accessible
  • Fairly low cost (Maybe under \$1000 for the machine vs nearly \$1M and many filaments cost 1/10th that of polyjet resins or sintering powders)
  • The materials themselves can be UV resistant and salt water resistant

Cons:

  • Joinery and seams create passageways for water ingress, so you'd need secondary sealant
  • The FDM process itself isn't always watertight, so you'd need sealant anyway
  • Low interlayer adhesion limits the tensile strength along one axis and the shear strength in one plane, so you'd either need composite hull panels with varying print orientations (in which case, just do a composite layup instead) or a fairly careful analysis of principle hydrodynamic stresses

There's significantly more to the discussion as well, but without really understanding your design constraints, it's difficult to give any concrete advice.

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  • $\begingroup$ Thank you for this detailed answer ! Well, honestly about the cost I was mostly interested in actually getting an idea of how much it could be and compare that to other methods (the goal is to make it as much inexpensive as possible but to ensure that it will bear ocean conditions) , i'd be curious to know the price design studios would make you pay just to print with a 3D printer like Stratasys Connex 1000. $\endgroup$ – Trevör Mar 18 '17 at 9:42
  • $\begingroup$ @TrevörAnneDenise The studio I am most familiar with is Fathom in Oakland, CA. I know of some online services as well (like Shapeways and i.Materialise), but you're likely looking at the low-thousands (USD) as a starting point. Realistically, you would be far better off with a composite hull. Use an FDM assembly and layer matrix reinforced fibers on the inside and outside. Strong, light, and relatively inexpensive. $\endgroup$ – Hari Ganti Mar 19 '17 at 23:11
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Something similar has been done in ABS already, although I don't expect it gets left in the water for years. See the video, showing a kayak being printed in many ABS sections of about one cubic foot, then bolted together and sealed.

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It is totally fine, it is what I did a lot at my previous job. I 3D printed cases for underwater stationary equipment, mini-submarines and simple buoys, and almost all of them work fine. In fact, most of the failures I had were the breach of sealant. Or someone forgot to close the lid. For example this thing I've made.

To make watertight objects, follow the rules:

  • You may use PLA. Over the course of a few years in water it degrades only in color, unless exposed to direct sun heat for prolonged times.
  • Obviously, use several outer shells.
  • If you are making floating thingy, and there is a free space in your hull, do NOT leave it empty! Instead, make it solid in the model, and set slicer to use sparce hexacomb infill with a solid layer every 20-30 layers. This way, your model will be made of hundreds of isolated pockets of air, so a breach of a hull in some place will not sink it. You can also drop lead pellets into those pockets as they are made to weight the ship properly.
  • Set nozzle diameter to layer height ratio to more than 3. It will produce nice thick layers welded shut. For example, use 0.7 nozzle for 0.2 layer or 0.4 nozzle for 0.1 layer. The last one can be a bad choice if your extruder can't provide that little flow and tears layers. In general, obtain those bigger nozzles for technical parts. 0.4 nozzle is for toys, really.
  • Remember that wires conduct water just as well as electricity - water runs between the isolation and the copper core. No wires should go through the containment.
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  • $\begingroup$ Thank you for this detailed answer and all of those advices, that's really interesting especially the part about not leaving the free spaces empty ! $\endgroup$ – Trevör Mar 18 '17 at 9:47
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I would give it a try, but dont expect it to be watertight. Print the hull and paint it with some epoxy and you will be fine. (outdoor paint job, epoxy is bad for you)

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Probably feasible, Affordable or simple probably not. To start from an affordability perspective, kayaks normally weigh around 20 kg, they kayak in the video mentioned in the other answer weighs in at 30kgs. Assuming you print all your parts perfectly, your using \$15 a kg filament, and you use 25 kg of abs you are looking at a minimum of \$375 in material just to print the kayak. After this the cost would only go up because now you need the parts to fasten it all together, the seat ect... In other words, it will probably be no cheaper and a whole lot more time intensive then buying one.

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  • $\begingroup$ Thankak you for your answer ! I am not planning to build something as big as a kayak, so the cost wouldn't be as high ! $\endgroup$ – Trevör Mar 18 '17 at 9:48

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