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Wing profile info for backyard hydrofoil builders

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Biggles
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Re: Wing profile info for backyard hydrofoil builders

Postby Biggles » Tue Feb 16, 2021 11:17 am

Thanks again for the help in airofoil selections. With this crazy lockdown and no beach allowed, I have been drawing 3D foils and wings to keep myself sane!
Would it be possible to run 2 more calcs for me to get preferred sections? I see the top of this page request you added a min velocity as 10km/h - please can you do that for these.

1. 90kg , 168500 area , 258 chord , 955 span - low 10km/h speed biased

2. You also wrote : "The optimiser 5000 says that area of around 1450 cm^2 is a good area for this speed range / wingspan" This was for 12.5km/h and wingspan 1050 to 1150. Could you do the same for low speed biased 10km/h and same wingspans.

Modeling directly off an Albatross wing gives for 1150 Span , 150 Chord and 130000 area. This seems incredibly little for my 90kg of pies !!

Thanks again
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PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Wed Feb 17, 2021 4:50 am

Biggles wrote:
Tue Feb 16, 2021 11:17 am
Thanks again for the help in airofoil selections. With this crazy lockdown and no beach allowed, I have been drawing 3D foils and wings to keep myself sane!
Would it be possible to run 2 more calcs for me to get preferred sections? I see the top of this page request you added a min velocity as 10km/h - please can you do that for these.

1. 90kg , 168500 area , 258 chord , 955 span - low 10km/h speed biased

2. You also wrote : "The optimiser 5000 says that area of around 1450 cm^2 is a good area for this speed range / wingspan" This was for 12.5km/h and wingspan 1050 to 1150. Could you do the same for low speed biased 10km/h and same wingspans.

Modeling directly off an Albatross wing gives for 1150 Span , 150 Chord and 130000 area. This seems incredibly little for my 90kg of pies !!

Thanks again
Hello Biggles,

You kiting in Durban or CT? Durban was my hometown for 12 years and CT 3 years. Big fan of both, wish it was possible to fly over and get some epic foiling in over there. I think the swell in both spots is much better and more consistent than Perth... we suffer in the summer months with no swell.

1. 90kg , 168500 area , 955 span - 10-25 km/hr.
You mention a chord of 258 mm? For a elliptical area distribution the chord would be 225 mm in my calcs, that is quite a big difference. Please note you would need to add in inefficiency factors for increased induced drag when going away from elliptical lift distribution.
Capture - Biggles 955 x 1685.PNG
And some results below for 1050 mm span x 1700 cm^2 area:
Capture - Biggles 1050 x 1700.PNG
And some results below for 1150 mm span x 1530 cm^2 area:
Capture - Biggles 1150 x 1530.PNG
This table below (if it's legible) shows how the average drag and initial drag changes over a big range of areas and wingspans. You will see how I chose the areas of 1700 cm^2 for the 1050 option and area of 1530 cm^2 for the 1150 span option. It looked like the best combination of minimum average weighted drag and minimum initial drag. The 10% resolution can be reduced to get a bit closer to a final chosen area, when needed. Makes for interesting info in anycase. In general I think 10 km/hr is just getting to really really low speed for our kind of practical wingspans. Drag is dominated by induced drag. Many more options available when going faster.
Capture - Biggles 10-25kmhr optimisation.PNG
Capture - Biggles 10-25kmhr optimisation.PNG (37.23 KiB) Viewed 1726 times

TeachMe
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Re: Wing profile info for backyard hydrofoil builders

Postby TeachMe » Wed Feb 17, 2021 12:40 pm

PrfctChaos wrote:
Happy to revise any of these if you want to update the inputs, such as speed range etc. Would be keen to see your design / build results as well. There might be a lot, so maybe start a dedicated build thread, would be interesting. Cheers.
Thanks a lot for your help! It seems like your program is pretty powerful and useful for first time builders like me. I will consider your suggestions for my build and keep you updated, I'll let you know, when I start my own build thread.

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Re: Wing profile info for backyard hydrofoil builders

Postby Biggles » Sat Feb 20, 2021 9:38 am

@PrfctChaos. Yes, the 258 was used for model simplicity as a previous lower aspect wing, that is really epic carving on swell, just got stretched and matched to an Albatross wing on the trailing edge profile ... hopefully I can keep the great carve and add more pump. I was using a completely flat profile as the manufacture was pour polyurethane into silicon moulds which are then bent during cure.
Umdloti & Vechies got foiled every day for many years (Sadly I think foiling has taken a back seat there again now, a very active group in Richards Bay however) ..... now in Langebaan (Some real secret gem foiling swell here) .... and Bigbay is also very underfoiled over twinflipped ! Not enough usage of our swell using foils ... too many speed merchants....and brand designers don't understand the average foiler just wants to chill and have easy fun in lovely conditions.
Sent you a PM regarding your great program.
Thanks!

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Re: Wing profile info for backyard hydrofoil builders

Postby fluidity » Sun Feb 21, 2021 3:34 am

Biggles wrote:
Tue Feb 16, 2021 11:17 am
Modeling directly off an Albatross wing gives for 1150 Span , 150 Chord and 130000 area. This seems incredibly little for my 90kg of pies !!
I have 105kg of pies and originally designed a 1800 sq cm foil which needed the wind to be nuking to get me up with no prior foil experience. I built a 2650 sq cm foil which was easy to learn on in lighter winds and now I'm back to my 1800 foil. Less drag, faster and easy to bump up on foil in all but the lightest winds. Doesn't pump quite as well but travels between lulls faster and accellerates faster. Minimum speed is still quite slow though I haven't measured it. Feels like a fast walking speed. Big foil- med walking speed. But I'm looking at a slightly thinner foil down to 1400 sq cm for my next. And will probably in time go even lower. Pie dependent.

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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Mon Feb 22, 2021 1:21 am

Biggles wrote:
Sat Feb 20, 2021 9:38 am
@PrfctChaos. Yes, the 258 was used for model simplicity as a previous lower aspect wing, that is really epic carving on swell, just got stretched and matched to an Albatross wing on the trailing edge profile ... hopefully I can keep the great carve and add more pump. I was using a completely flat profile as the manufacture was pour polyurethane into silicon moulds which are then bent during cure.
Umdloti & Vechies got foiled every day for many years (Sadly I think foiling has taken a back seat there again now, a very active group in Richards Bay however) ..... now in Langebaan (Some real secret gem foiling swell here) .... and Bigbay is also very underfoiled over twinflipped ! Not enough usage of our swell using foils ... too many speed merchants....and brand designers don't understand the average foiler just wants to chill and have easy fun in lovely conditions.
Sent you a PM regarding your great program.
Thanks!
About the 1300 cm^2 area.... it doesn't seem to be small these days. If we have a bit of a look through the popular Axis wings used for prone and Sup foiling around here. (I use Axis often as a example, because there are plenty of guys on them in Perth and they have a great range of different wing types, plus they are one of the few manufacturers that give good info on their wing sizes.). So below are links to a few wings that get used around here depending on whether the user in into speed, pumping, carving etc...

https://axisfoils.com/products/980mm-carbon-front-wing - High performance speed range, 1323 cm^2 area, 980 mm wingspan
https://axisfoils.com/products/s-series ... front-wing - Surf performance range - 1293 cm^2 area - 860 cm wingspan
https://axisfoils.com/products/s-series ... front-wing - Original carve wings - 1184 cm^2 area - 900 mm wingspan
https://axisfoils.com/products/s-series ... front-wing - Pump and glide wings - 1430 cm^2 area - 1010 mm wingspan

Might be worth checking out a few videos of guys using these different types of wings. Seems like you might be looking for something like the Surf Performance range, but improved pumping. Or maybe something like the Pump and glide range, but more curved like the Surf performance range to make turning and carving easier...

Just adding a few more wings to look at for inspiration/ideas.

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Re: Wing profile info for backyard hydrofoil builders

Postby spiru » Fri Feb 26, 2021 4:37 pm

Hi,
I am glad I found this thread. I have been making my foils for a couple of years. I have made abut 8 wings and a bunch of stabs. All 3D printed and vacuum laminated in carbon. In fact I am the one who designed and made the https://www.thingiverse.com/thing:4657218 foil that some of you are making. I am happy to see others are using my design. I wonder if it is working well for you. I have learnt a lot on that foil and rode it for thousands of km. Now I am riding mainly a 680 sqcm similar to a Moses 590 in shape but using my own profile with a thin leading edge.
Choosing the right profile has always been my main question and I have been a bit lost in that area. I copied some profiles from commercial wings (Mosses 633) and sometimes I used what I read online that could work, but nothing accurate nor scientific about it. So it seems like you have the perfect tool to improve my wings.
I am thinking about making a fast carving freeride wing of about 800 sqcm and 70 cm wing span. I am 80cm naked.
Do you consider RG 14A-1.4/7.0 to be the best option?
With my 680 sqcm wing I am hitting a max speed limit of about 40km/h, and I would like to know if it would be possible to reach 45 or 50 km/h with a larger area

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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Tue Mar 02, 2021 12:18 am

spiru wrote:
Fri Feb 26, 2021 4:37 pm
Hi,
I am glad I found this thread. I have been making my foils for a couple of years. I have made abut 8 wings and a bunch of stabs. All 3D printed and vacuum laminated in carbon. In fact I am the one who designed and made the https://www.thingiverse.com/thing:4657218 foil that some of you are making. I am happy to see others are using my design. I wonder if it is working well for you. I have learnt a lot on that foil and rode it for thousands of km. Now I am riding mainly a 680 sqcm similar to a Moses 590 in shape but using my own profile with a thin leading edge.
Choosing the right profile has always been my main question and I have been a bit lost in that area. I copied some profiles from commercial wings (Mosses 633) and sometimes I used what I read online that could work, but nothing accurate nor scientific about it. So it seems like you have the perfect tool to improve my wings.
I am thinking about making a fast carving freeride wing of about 800 sqcm and 70 cm wing span. I am 80cm naked.
Do you consider RG 14A-1.4/7.0 to be the best option?
With my 680 sqcm wing I am hitting a max speed limit of about 40km/h, and I would like to know if it would be possible to reach 45 or 50 km/h with a larger area
Hello Spiru. 8 wings, that's a impressive collection! I'm sure you would have heaps of good manufacturing advice for anyone here starting out making wings. Wouldn't mind seeing a pic or two if you have any photos.

According to the calcs 50 km/h, looks to be achievable at this size without a great deal of drag (More drag means more kite power needed to reach that high speed). Please note I am not checking for cavitation, but as far as I have heard that is not much of a worry with our T-foils until getting up around the 65 km/hr (40 knot) speed range, so probably wouldn't be too worried about it yet. But just mentioning that I haven't checked it, so that if you are worried you can do further calcs to check cavitation specifically.

RG 14A-1.4/7.0 is a good and completely feasible option for this wing. With about 2.4Kg of drag around the middle of the speed range (34 km/h) and 3.5 Kg of drag at high speed (50 km/h). However, the NACA1306 would be my choice if this wing was going to be used in its mid to high speed range, with 2.3 Kg drag around the middle of the speed range (34 km/h) and 3.0 Kg of drag at high speed (50 km/h). Comparison below also showing another one or two options, NACA1507 and MH23 also deserve honourable mentions. NACA1507 with 2.3 KG at mid speed and 3.45 KG at top speed. MH23 with 2.6 Kg at mid speed and 3.1 Kg at top speed.
Capture - Spiru 700 mm x 800.PNG
Hope it helps

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Re: Wing profile info for backyard hydrofoil builders

Postby spiru » Wed Mar 03, 2021 3:36 am

Thank you PrfctChaos for the info about the fast profiles, I see that the NACA 1306 is very thin: https://bit.ly/3qcJTiJ . This profiles are more challenging to make at home, but I think I can reinforce the central area with more carbon to make it strong enough.

These are some photos and info of my early foils in case they can help other DIY foilers. I have to take photos of the present wings I am using lately. I am making a free race wing and a super carving Axis 660 replica (if someone knows its profile I'd appreciate it). And definitely want to try the symmetric stabs you are using. I am very curious about positive lift stabs and how they perform against negative lift.
For first time foilers I wouldn't recommend a DIY foil unless someone experienced tries it first and approves it as an easy beginner foil. Otherwise you would never known if the learning problems are due to your foil or your skills. I think it's better to start with an easy commercial model and then move to DIY tuning. At least this what worked for me.

This is the 1240 sq cm wing I posted in Thingiverse and the one that helped me to progress the most. I tried to copy the profile of the mosses 633, the outline is more rounded, less pointy. It has 1.5º wingtip washout. I know the washout effectivity in hydrofoils is questionable, but I had good sensations from two wings where I used it, specially very close to the surface, near ventilation. I also think it may help stopping wingtip ventilation from propagating through the leading edge but I would have to make the same wing with and without washout to test this (not anytime soon). Also, being the wingtips so far back from the central leading edge may also help a a lot to stop ventilation form propagating. I often see air bubbles trapped in the wingtip vortex after a quick ventilation. Now I am not using whashout anymore because I want to optimize speed and I have more control over near breaching foils. Compared to the real Mosses 633+483 stab my wing is a bit more draggy, about the same top speed, more agile due to shorter stab and front foot pressure doesn't increase with speed.
3D Printed and showing carbon tubes to join pieces:
Image

All joints smoothed with epoxy + microspheres:
Image

Once vac laminated:
Image

This is a 1000 sqcm low aspect carving wing:
Image

Image

This was my first wing, big, thick and draggy, and lots of lift. Very easy to learn air foot changes (so much lift I couldn't lower it for on-water foot changes, so I had to learn to make them directly on flight). The downward tips make carving rail to rail smooth and continuous.
Image

Image

I made some 800 and 1000 sqcm gullwing wings inspired by the MFC wings. They didn't work too well for me probably due to the wrong profile, but I will give them another try with different stabs now that I have improved my skills and have got better at tuning stab angles:

Image

Image

Image

This is a relatively large stab 282 sqcm 37 cm that I am using with a 686 sqcm front wing with my present foil for fast carving, big choppy and strong winds. It calms down the front wing making it quite easy for its smallish size by today's standards. Stable for foot work, even foot pressure with speed (I am very picky about this):
Image

I make the fuselages grinding square alu bars. I use stainless steel helicoils in all threads and make holes to adjust stab in two different positions. I have been using an embedded sacrificial zinc anode to minimize galvanic corrosion. I drill holes for 2 x 8m Liquid Force mast and 3 x M6 Gong/Naish/Airush mast. Front wing goes on the bottom and stab on top. I use the 90cm Gong mast the most because it is lighter than my other Liquid Force mast. But I think second gen Liquid Force with its wider cord ventilates less (or nothing) at extreme upwind angles or with random choppy at less extreme angles.

Image

For boards, I make my pocket boards by shaping 2 €, 30mm thick isolating foam from the DIY shop (Leroy Merlin in Europe, kind of like Home Depo in US), Then vacc laminate them over a rocker shape to make rocker. I use my first paulownia board as a rocker shape. I laminate the bottom first to avoid wrinkles, and it already keeps the rocker shape, so the top doesn't need to be vacc against the rocker shape. I overlap edges and reinforce the area around the foil a lot. Weight is 2kg without painting and about 2.3-2.4kg with cork grip and paint. There are much more elegant ways to make boards, but this is a very cheap way and it works for me. These boards have thousands of foiling km and haven't shown any weakness. I don't jump though.

Image

Image

Image

I am now using US rails, but I also make my own 3D inserts for straps (foot hook now) and foil with stainless steed embedded threads. I use M6 blinded threads for straps, so no problem destroying threads with frequent straps changes, or reaching foam with too long screws:

Image

Fixed with epoxy before laminating:
Image

What I have learnt from mistakes:
I have been using mostly ABS for 3D printing. ABS is stronger as material than more commonly used PLA, but 3D layer adhesion is weaker with ABS than with PLA, so final strength can be stronger with PLA. I print wings vertically for profile accuracy. This makes the 3D wing fragile, but the strength will come form the carbon. The wing can be foam inside, so the strength of the core is irrelevant. ABS warping at the trailing edge is an issue. It can be fixed filling the gaps between layers with epoxy+microspheres but it's more work. So I have made my latest cores with PLA but I haven't laminated them yet. Temperature resistance of PLA is a concern, but not too worry about it once carbon is hard. I use slow epoxy which doesn't heat up much.
I overlap carbon layers around leading edge for extra strength and avoid delaminating. I hit sandy bottoms all the time, no problem. I hit rocks sometimes and usually is not too bad.
I had delaminating problems along the leading edge a couple of times due to sanding too much the leading edge looking for perfect finish. I sanded so much that I exposed the core a little bit along the leading edge. After some use it produce what I call the crocodile effect: top and bottom carbon layers open like a crocodile jaws when going fast making you fly over board without apparent reason. When I looked at the foil everything looked normal (crocodile mouth closed), but when I tried to water start again croc mouth opens and makes it impossible to ride. Easy to fix and avoid: make sure there is some carbon along the leading edge and do not sand too much.
Fuselage attachment is another area that needs attention:
If the wing design includes a recessed thinner area for the fuselage, it may need some reinforcing. Carbon gets much more resistance with thickness. I snapped a wing at the fist water start just because the wing was too thin in this area. It is frustrating to brake a wing in the first try after so much work. Braking stuff its part of the DIY life. But easy to avoid reinforcing that area a lot, or what I do now: avoiding recessions. I make a flat area in the center of the wing where the fuselage sits flat. I make fuselages as hydrodynamic as possible, so I don't think drag increase against a recessed fuse is too much of an issue at normal non-racing speeds.
I use 3 countersunk M8 bolts to attach the wing to the fuselage. This is a high stress point that requires some special reinforcement. I print this area at 100% infill, but this is not enough. If you laminate the wing and then make countersunk holes, the bolts' head will sit agains the 3D core. It will work well for a while. But after hours of use, you will notice that the front wing needs retightening after each session, and eventually after some minutes. The central 3D core area will deteriorate inside under the high loads and the wing will eventually get too loose. Solution: Before laminating overdrill holes and fill with epoxy+micro or better with epoxy+carbon fiber. For M8 bolts I over drill to 13mm, fill, and re-drill to 8mm. Then countersunk holes, and last laminate. So the countersunk part of the hole is carbon laminated and the bolt's head will sit against carbon, not ABS or PLA.
With the reinforced leading edge and the overdrilled-filled-laminaned holes the wings are bombproof.

These is a video having fun with these wings, line mounted scenes on the 686 sqcm and surface scenes on the 1240 sqcm:


Some slow carving on the 1240 sqcm


Happy DIY foiling
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salvatoreone
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Re: Wing profile info for backyard hydrofoil builders

Postby salvatoreone » Mon Mar 08, 2021 12:43 am

Hey mate, very impressive collection and tons of information!


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