Thank you for awesome feedback !
I will try to answer all of your comments:
1. Yep, I was little bit sad that it didn't generate much interest, I thought that people would be more excited about the possibility of printing large items efficiently, but I fully acknowledge that my software is experimental, VERY hard to use for non-programmers, etc. so that's mostly on me, I need to work on interface to provide nice desktop/web GUI (not that hard at all, much less than actual inner workings)
2. I know about rudders made by Don Kiesling, although I thought they are foam core - long time ago I created
river rudder
(small 10cm/4inch height, NACA0012 airfoil) for myself with 3D printed core (CF filled nylon) and fiberglass skins, I use it already for almost 4 years, it took quite a beating many times (dragging across river floor, etc) but it's still holding very well, despite having aluminium shaft (and being much, much lighter than for example stock Nelo 520 river rudder (which has very bad finish with prominent seam on the leading edge).
Of course premium product for sale would be made with carbon fiber shaft (or steel for more durability) and laminated with carbon instead of glass-fabric (spread tow would look amazing), also NACA0012 is a OK choice for hydrofoil (good range of acceptable CD/CL ratio, benign stall characteristic), but there are better airfoils out there designed from inception as hydrofoils with much larger area of laminar flow and better CD/CL ratio over similar AOE (Angle of attack) range.
3. Very good points, for now I stuck with simple hand-laminating of the 3D printed composite cores, but that of course means extensive post-processing to get that awesome mirror finish look -
this is for example SUP paddle
with carbon-petg filament core and 200g twill carbon fabric skin (2 layers + unidirectional strips on shaft for bending stiffness).
It's similar weight to production SUP carbon paddles (470g) and when I tested the shaft stiffness it was similar as well, but getting the finish to acceptable flatness was a major PITA and sanding/polishing that took by far the most work - if that would be production item, most of the price would need to cover that = not economic.
I experimented with Mylar foils but the classic approach is only fine with surface mostly curved in 2D and very little 3D curvature.
I have one idea in mind, which is basically vacuum forming mylar sheet over pattern to match the curvature perfectly, it should be possible with core 3D printed from high TG material (like PA12CF15, resisting 170C at 0.45MPA pressure), the caveat is that there is a thin line between sheet conforming enough and sheet conforming too well (3D printing imperfections and layer lines imprinted on the sheet itself).
I have no time for that now, but I will test it in the future.
It's not a big deal for boat prototypes though, for example that canoe is just laminated fiberglass with no post-processing and it's fine for its purpose as a functional prototype which you can throw on water, test its behaviour and quickly print/laminate a new one if you find out you need to make any changes.
The final iteration which you are satisfied with can be then painted/sanded/polished and you can take negative mould from that for future production.
Another possible direction is to target the tech for home-builders, current cedar-strip kits are very work intensive and basically mean weeks/months in the garage, with this tech you could sell just gcode (3D printing format) files and people could download/print/laminate them, providing they have good enough and large enough printer (which is my primary focus now, providing such printers).
Ff course I fully get the appeal of traditional wooden boats and I find wood-strip boats simply gorgeous, this would just provide a feasible alternative for quicker building of "modern" style/look boats.
4. I'm familiar with resin infusion and I think I have a pretty good setup for that -
this is for example resin infused flat panel
and it turned out very nice. The idea with flow channels printed directly in core is brilliant, I already tested how airtight you can make the print (so resin will stay in channels and won't get sucked into hollow spaces in core), it was very promising, certainly doable.
With higher temperature polymers (PA12CF15 or even more exotic PPS/PEEK with TG above 200C) even pre-preg lamination is fully feasible.
5. Yes, I'm located in Europe (right in the middle), but I would be happy to print that airfoil and send it to you just for the shipping costs. Do you have it already designed/tested in XFOIL or similar program ? If not, my custom designer/slicer incorporates airfoils namespace/library where any airfoil shaped surface can be easily defined, airfoil cross-section, planform (tapered/elliptical) etc.