finfoil.io Designer software review

[fluidity]

I recently got an opportunity to try this application from the designer Hans Robeers.
Normally I design using openSCAD and although I have an infinite amount of control it's a somewhat laborious process involving setting maths formulae, some trial and error and making new formulae when I want to make a significantly different shape.

In Hans finfoil app you can choose to design for surf, windsurf or foil (Hydrofoil wing in this case)
Surf and windsurf apps differ by surfboard attachment plug/socket foot which is automatically grafted to the root of the fin.
It's possible that Hans would look at fuselase and mast socket options on foils in the future although he has only recently added foils.

I had a design in mind, which was a slightly higher surface area, slightly thicker version of my latest openscad unifoil design, with high centre chord and medium outer chord. This would allow rear mast foot location and a combination of benefits of low chord the outside and high lift + single mast socket without fuselage on the rear. I also wanted it to be just over 2000 square cm and have a wingspan no more than 800mm and a chord of 450mm.
I wanted gently rounded wingtips to avoid nasty accidents with hand held wings and some down sweep on the wing tips as well as some centre dihedral to reduce the cnc block height requirements.

I've attached some snapshots showing what i was able to produce in about 40 minutes. Grey dots are moveable points, click on one and it brings up green dots to change the angles of the segment within it's ajoining curves. Extra points can be added. Wing cross sectional profile has a default which I modified. There is flat option and a curved option for the wing form looking front or rear view, I chose curved and was able to get the minor dihedral and wingtip change I wanted. Because a wing with such a long chord like this is very thick in the middle, the dihedral effectively gets eaten up by the centre of the wing swelling downwards but this is fine and expected, it keeps the total CNC block thickness requirement down.

In the plan view I used just the default stretch and pivot points after setting 80cm wingspan and the chord and thickness. I moved the points and pivots around to get the shape I wanted and the default thickness straight line(adjustable) profile allowed me to alter the automatic thickness to chord ratio if I wanted, I left it at default.

You can experiment completely for free but Hans gave me some testing credits so I could save a high resolution output file.

Web address is simply finfoil.io

[nemoz]

can you please post results of XLFR5? I think this is one of the big plus of finfoil

[mandiw]

hello fluidity
i like this shape more than your first one. based on your first ride on the other monowing, where would you position the mast (distance front edge wing to front edge of mast and how would you mount the mast to wing (0 degree)?
thanks and pls. send information once you have tried on the water.

[nemoz]

looking at it once again, it's close to the one I built last spring.
download/file.php?id=94314&mode=view

[fluidity]

can you please post results of XLFR5? I think this is one of the big plus of finfoil

looking at it once again, it's close to the one I built last spring.
download/file.php?id=94314&mode=view

Hi nemoz,
XFLR5 is completely new to me. There is talk on the internet when I investigate that the XML import is broken so it may be that an earlier version of XLR5 is needed than the one I downloaded. Apparently there are some ways to go from XLR5 to an STL, but (reading last night when I should have been already asleep!), the export may still be an external utility.

I can design my own foil sections using any number of tools but I don't know of one that grabs a 2D picture and converts it to a NACA description file. Had a brief chat with Hans Robeers and I get the impression that people who work a lot in the industry have developed a lot of experience finding workarounds for XFLR5 to be able to run their testing. So short story is, I don't have the experience yet to figure out how to get Hans .xml file into XFLR5 and XFLR5 also doesn't have the code to import an STL. Likely many in the industry have written their own utilities to do the conversions externally? Or are using older versions of XFLR5? I have also considered importing the .stl into openfoam but it has a steep learning curve for setting all the required surrounding conditions, I've already tried that with one of my other wings.

Regarding the link to your wing, sure, general outline similarities but I'm curious, have you matched thickness to chord ratio throughout the span? Or appended the tail? I don't think either approach is a great selection with that planform as the first approach provides an extreme vertical transition between thicknesses of the tail to front section and the side parts of the wing. And the second, it provides drag but without usable lift to offset the cost of the drag.
I may be wrong, it would be interesting to see your solution. I did a much more gentle transition between the short and long chords because I have maintained thickness to chord ratio throughout to make evert part of the span and area productive. In the centre it's FAT as a consequence but it blends out nicely, though I'm sure that at very low speeds there will be a lot of water escaping from under the centre to the inside corners.

[fluidity]

hello fluidity
i like this shape more than your first one. based on your first ride on the other monowing, where would you position the mast (distance front edge wing to front edge of mast and how would you mount the mast to wing (0 degree)?
thanks and pls. send information once you have tried on the water.

My other (thinned) monowing has centre of lift back about 5cm from my normal DIY wing that I optimised for fuselage connection and F-one inflatable foil board usage. That wing, my toes are just past the blue indicator lines on the F-one board. On my monowing my toes need to be about 4 cm back. i think that's primarily a consequence of not having a stabiliser wing with a deliberate downward front pointing angle. So with my unifoil there is of course drag (though not as much(it's thinner and has less area) but the corrective bow lift is now from my balancing which is really very easy, It's more stable pitching wise to ride than my big wing was with the pultruded glass rod rear fuselage section before I swapped out to titanium.

So this wing I designed in finfoil.io, there is a further forward centre of lift for the same total chord as my thin unifoi (this is from the planform differences, there is more forward area in the new wing), I would probably move the rear of the mast socket about 50mm forward of the back of the wing to bring it in-line with my 1200mm span higher aspect wing to target that same sweet spot with my toes positioning.

[mandiw]

thanks for your quick reply. am i right that you would position the rear point of the mast socket about 50 mm from the rear end of the wing?
any suggestion about angle of wing to centerline mast (0 deg)?

[nemoz]

can you please post results of XLFR5? I think this is one of the big plus of finfoil

looking at it once again, it's close to the one I built last spring.
download/file.php?id=94314&mode=view

Hi nemoz,
XFLR5 is completely new to me. There is talk on the internet when I investigate that the XML import is broken so it may be that an earlier version of XLR5 is needed than the one I downloaded. Apparently there are some ways to go from XLR5 to an STL, but (reading last night when I should have been already asleep!), the export may still be an external utility.

I can design my own foil sections using any number of tools but I don't know of one that grabs a 2D picture and converts it to a NACA description file. Had a brief chat with Hans Robeers and I get the impression that people who work a lot in the industry have developed a lot of experience finding workarounds for XFLR5 to be able to run their testing. So short story is, I don't have the experience yet to figure out how to get Hans .xml file into XFLR5 and XFLR5 also doesn't have the code to import an STL. Likely many in the industry have written their own utilities to do the conversions externally? Or are using older versions of XFLR5? I have also considered importing the .stl into openfoam but it has a steep learning curve for setting all the required surrounding conditions, I've already tried that with one of my other wings.

Regarding the link to your wing, sure, general outline similarities but I'm curious, have you matched thickness to chord ratio throughout the span? Or appended the tail? I don't think either approach is a great selection with that planform as the first approach provides an extreme vertical transition between thicknesses of the tail to front section and the side parts of the wing. And the second, it provides drag but without usable lift to offset the cost of the drag.
I may be wrong, it would be interesting to see your solution. I did a much more gentle transition between the short and long chords because I have maintained thickness to chord ratio throughout to make evert part of the span and area productive. In the centre it's FAT as a consequence but it blends out nicely, though I'm sure that at very low speeds there will be a lot of water escaping from under the centre to the inside corners.

I thought XLFR5 were included in finfoil without any export import... I'm struggeling finding a freeware cfd program to setup a fixed workspace and just copy and paste different wing directly from a cad program, only in that way we can make multiple tests and probably understand properly what is better between different designs, without it I can only assume or imagine what can be better.

[fluidity]

Hi Nemoz,
Finfoil will export an xml file for XFLR5, I've opened it, it looks like XML and it has x, y,, dihedral and twist data for sections at each part of span of wing. The foil section is referred to but not with any data. It looks legitimate.
I believe it's required to run XFLR5 seperately and manually load a valid foil shape and then load the XML file however I think XML is currently brolen in XFLR5 and it only reads: .dat, .plr, .wpa and .xfl currently.

[nemoz]

http://marc.klein.free.fr/lego/stl2dat/stl2dat.html stl to dat... never used just found the link
https://github.com/HazenBabcock/stl-to-dat