Wing profile info for backyard hydrofoil builders

[PrfctChaos]

Thank you. If I can't ride (water and weather too cold and no wind anyway), I'm at least building to ride

For wing surfing my first wing of 1800 sq cm was on the small side. Building a 2650 sqcm wing is letting me learn on days when the wind is around 15 knots where as before I needed 20 knots +

Dont follow that advice for kiting. 1250 is enough and a good size for light wind and learning

[fluidity]

I'll take your advice on that for myself PrfctChaos. I missed it was for kiting he wanted it
Happy with the kiteboard but I'm sure I'll try my kites with a wing at some stage

[kobajagrande]

Don't mean to spam, but with pics more is better.

Wow, this is amazing.
Can you share the name and the brand of the cnc you have ?
Thanks

[robke]

It was an interesting read on Moth @PrfctChaos. The stab has almost as much section drag as the main wing. I'm using inverted stab profile ( I think H105), but on Moth looks like it's non-inverted. And I think you said you use symmetrical profiles.
The way I understand is : noniverted good on high AoA, inverted good on low AoA, symmetrical kinda in between. What do you think?
I was a bit confused since I thought about a controlled stab. In that case it always generates downward force. But on our boards, we change angle of attack with weight transfer, so yes, it can produce lift at low travel speeds.
I agree with you on "free" drag reduction, I would probably go for another profile if I knew better. I need to check how can I optimize wingtips as that can reduce drag by a fair amount.

I have one more idea, kinda silly. I've got a 8hp boat, tried foiling with a SUP foil behind it with my big wing. It's doable, but it's just a hair over stall speed, so barely doable. So I'm thinking, since I have more than one wing, make an adapter and use two wings in a biplane configuration don't see why it wouldn't work

kobajagrande, I made the cnc machine myself. It's basically components from ebay/aliexpress, the frame I made at work/home. It lets me do many many unnecessary things

[PrfctChaos]

It was an interesting read on Moth @PrfctChaos. The stab has almost as much section drag as the main wing. I'm using inverted stab profile ( I think H105), but on Moth looks like it's non-inverted. And I think you said you use symmetrical profiles.
The way I understand is : noniverted good on high AoA, inverted good on low AoA, symmetrical kinda in between. What do you think?

Stabs really do deserve more airtime, they play a bigger role than they are given credit for. Below are some numbers you might find interesting. It is a comparison of a NACA0008 (a typical symmetrical profile) and Inverted S2205 stab (Chose the NACA0008 since it has the same thickness as the S2205, so a close comparison). Stab size is chosen as 460 mm wingspan and 220 cm^2 area. I used your freeride wing (calculated above as the front wing).

NACA0008, angled down at 2.5 degrees compared to the front wing. This is compared to a inverted S2205 stab of the same size, the S2205 stab was checked at two setup angles, -2.5 degrees as well as -1 degrees compared to the front wing.

It can be seen that the NACA0008 at -2.5 degrees and the Inverted S2205 at -1 degree have almost identical Lift and drags throughout the speed range, so very little difference between the two setups. However, the S2205 couldn't handle the angles at the slowest speed and was stalled, while the NACA0008 was still within its operating range. So wide operating range is a good advantage to the NACA00 series. And you can use the same stab and just shim it a bit to match faster or slower front wings. I have not seen a good argument (with numbers of course....) for using non-symmetrical wings yet.

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[PrfctChaos]

A wing to go fast, one to go slow, one in the middle for freeride. Does it ever end.... I dont know .

I'm making a new replacement freeride wing at the moment, will put up some specs tomorrow. Going for 750mm wingspan and 900cm^2 area. Need a replacement to slot in between the tiny race wing and big wave wing (the current freeride wing gave admirable service, but it is out of date alas).

I'm a novice to moulding, but recently gave it the first shot on a small fast little Stab. Was super happy with how the stab came out (my new favourite, loose and very little drag). And the process of moulding was surprisingly easy, I was expecting to hit some pitfalls, but nope things just went smoothly. I'm so used to the multiple steps and waiting involved with laminating, that I was totally surprised by how quick and easy it was to just lay up the mould. Then once it was cured the resultant wing just needed a quick trim and sand and it was literally ready to use, felt like I was missing a few steps!!

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Anycase, decided to make the new freeride front wing by moulding it as well. Going for a 750 mm wide wing, 900 sq.cm. And optimised for a pretty highish speed range of 17.5 - 50 Km/h (~10-30 Knots). Hopefully it goes well, the drag values are nice and low in the middle of the range.

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Well, the new freeride wing is finished and I'm totally stoked on it, does what was expected (decent speed range and pretty low stall speed) and even turns way better than I was expecting for the 750mm wingspan (will not be scared to go even up to 800mm or 850 mm in the future). Had a chance to take it out in underpowered conditions for my 4m peak and some decent swell and messy ocean. The wing did a awesome job of just cruising along through the lowest luls (yes the surf wing would have kept cruising through even lower luls and a bit slower stall speed, but still respectably low minimum cruising speed for this wing) and when catching some swell it speeds up quickly and easily matches the swell speed even for the faster bumps (where the surf wing sometimes struggles to keep up with fast swell). Very happy with the carvability on the swell faces as well.
Also had 2 chances to take it out near the top end of the 4m peaks range and again the wing has no problem cruising at good speed when well powered (I really need to take a gps along obe of these days and get some good numbers). Slower than the race foil but not by that much, and much better stall speed and keeps on cruising really well through long luls (thus preffered option to the race gear when wind is inconsistent).

Will be my new go to wing for inconsistent wind or big fast swell or super choppy conditions (the long mast makes life easier than the short mast on the surf foil). And low wind with the fast kite.

I stupidly ran out of sandpaper between 60 and 400 grit. So had to go from 60 to 400 to 600, leaving quite a few 60 grit scratches visible. So will restock and give it a proper surface finish one windless afternoon. Doesn't seem to affect performance.

And yes it is solid carbon. I wasn't keen enough to put a foam core in this wing. Since it has 153mm max chord and a 6% thickness airfoil it means that it is less than 10mm thick at its thiclest point. Which can be consodered extremely thin. So was happy to go full carbon and not worry about stiffness or strength.

Pics below:

[salvatoreone]

very nice! Also, very neat fuselage, did you also make it?
So you have machined the wooden a mould? I'm starting to plan a new slightly faster wing than the one that I made previously (shared in this topic). I'll also be experimenting with options other than 3D printing the core as it was a pain in the ass at so many levels. The biggest issue was getting the epoxy stick to PETG plastic. Although I have to admit that the wing has already taken some beating, one tip is completely stripped off the paint due to some hard sand landings but the wing is still perfectly intact so I can't complain at the durability so far.

[PrfctChaos]

very nice! Also, very neat fuselage, did you also make it?
So you have machined the wooden a mould? I'm starting to plan a new slightly faster wing than the one that I made previously (shared in this topic). I'll also be experimenting with options other than 3D printing the core as it was a pain in the ass at so many levels. The biggest issue was getting the epoxy stick to PETG plastic. Although I have to admit that the wing has already taken some beating, one tip is completely stripped off the paint due to some hard sand landings but the wing is still perfectly intact so I can't complain at the durability so far.

Thanks! Yes the 2 halves of the mould are machined out of wood (it is what I have lying around).

The fuselage and mast is not my handiwork, wish it was it is a piece of art, it is a Taroa Sword 2 mast (mast and fuse is one piece). This older generation race gear is often veey cheap, but the old race wings can be a pain, so replacing it with a new freeride wing can give it a new lease on life. The race gear is often very strongly and stiffly built.

Maybe it is easy for you to 3d print the mould, since the pieces will be flat and wide (easy base adhesion and not much warping)? And then don't need to worry about adhesion between the epoxy and PETG? If you don't want a solid carbon wing, then can maybe fill the inside with thin (1-2mm foam strips) or thick (cheap) fibreglass, 2 part expanding foam etc... just a few ideas.

[salvatoreone]

very nice! Also, very neat fuselage, did you also make it?
So you have machined the wooden a mould? I'm starting to plan a new slightly faster wing than the one that I made previously (shared in this topic). I'll also be experimenting with options other than 3D printing the core as it was a pain in the ass at so many levels. The biggest issue was getting the epoxy stick to PETG plastic. Although I have to admit that the wing has already taken some beating, one tip is completely stripped off the paint due to some hard sand landings but the wing is still perfectly intact so I can't complain at the durability so far.

Thanks! Yes the 2 halves of the mould are machined out of wood (it is what I have lying around).

The fuselage and mast is not my handiwork, wish it was it is a piece of art, it is a Taroa Sword 2 mast (mast and fuse is one piece). This older generation race gear is often veey cheap, but the old race wings can be a pain, so replacing it with a new freeride wing can give it a new lease on life. The race gear is often very strongly and stiffly built.

Maybe it is easy for you to 3d print the mould, since the pieces will be flat and wide (easy base adhesion and not much warping)? And then don't need to worry about adhesion between the epoxy and PETG? If you don't want a solid carbon wing, then can maybe fill the inside with thin (1-2mm foam strips) or thick (cheap) fibreglass, 2 part expanding foam etc... just a few ideas.

At this moment I'm still unsure how to do the moulding, do you know any YouTube videos similar to what you've been doing?

3D printing the mould sounds great. Then I could use it either for moulding or creating an expanding foam core which would be laminated in carbon. These are the two options I'm strongly considering, but the moulding sounds a bit scary to me for some reason. I'll need to make some smaller parts for testing.

[salvatoreone]

I watched many videos about moulding and it seems relatively easy and with beautiful surface finish right off the mould but they all just make parts that are either simple panels or more complex parts that have two surfaces parallel to each other. I don't get how you make it for a wing which has asymmetrical top/bottom surface :/