Can we create the optimum wing first?

Sure but 10 times more expensive.

Could laminated thin plywood be an idea, if you think of the strength of a skateboard, and that’s only around 10mm thick,
carbon does sound nice though,but having the wing as sharp as a blade, is another safety concern

A lot of people have laminated 3mm ply to build the core, shaped it and then glassed it.
In terms of a skateboard, there is this guy that actually just used a skateboard deck: https://www.seabreeze.com.au/forums/Kitesurfing/General/DIY-hydrofoil-with-rubbish-and-an-angle-grinder
If you can get a deck that has no concave I think its almost a no-brainer as a starting point.

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yea, i seen that video over the summer, still deciding on the propeller at the minute, bought the 24" slingshot mast an base, the wing is another few stepping stones away :slight_smile:

I got the 30" mast and base, and then got a Unifoil (South African brand) Wing, Stab and fuselage (All carbon). I just have to mill an adapter for them and then its done.

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I have been getting to know the Heliciel Software, although the dialogs are mixed between French and English and the UI design is unusual, the program has the tools to apply to creating and estimating the optimum foil wing and propulsors. It is definitely increasing my understanding of the dynamics of the shapes.

In order to learn more about the design process, I am happy to enter some suggested foil dimensions and share the resulting lift and drag results here.

Here is how a foil is specified within the software, foil is selected, ocean water, 10 degrees C, the profile dimensions on this diagram page shown below are not to scale, they are schematic. You can also choose a profile from the database or input/import your own foil profile. Below is the image of some of the NACA profiles. Source here. Based on nothing whatsoever, I choose a NACA0010 that has a thickness of 10% of the chord length. Half wing length of 300mm, width at the root of 160mm and width at the tip of 80mm are entered. A design target of 10 meters per second is specified.

Curvature is specified in another dialog and left out for this first post.

Figures shown are half of the total values as the program is only estimating one side. At 36KPH, this wing will have a lift of 2800 Newtons, a drag of 42 Newtons, and a calculated 1800 Watts to overcome the drag of the full wing.

Doing a further analysis, the program cruches away and returns this chart showing the lift and drag at various speeds. This chart would show 110 kilos of lift at under 7 kph, factoring in only the main wing. Drag numbers do not reflect the board, the mast, or the motor/propellor unit.

Obviously the variations are unlimited. The question becomes the desired speed in a hydrofoil to achieve a given amount of lift. 110 kilograms at 12 kph for example. Maybe we can have a discussion on the average speed to center the designs around? Lower aspect winger i.e. wider wings will provide more lift at low speed but more drag at higher speeds. Narrow wings, higher aspect, will achieve the required lift at a higher speed but will have less drag going fast. What speed is ideal to lift out of the water? What is an idea top speed?

If anyone can supply some existing wing measurements, such as overall width, chord width root and tip, chord thickness and a plan view photo, I can try to enter in the shape and see what the results are. As time permits.

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Hello,
I have taken some photos of an AC50 foil, and it shows something like a NACA series 6 (the closest one I found is the NACA 63(2)-615) this profile has an advantage that could be useful for us. For example over a range of low attack angle, speed is transformed into lift without increasing the drag. @x-jets Would it be ok for you to do some simulations with this type of profiles?

Also, the chord of the tip was extremely narrow maybe 50mm

First test specs, NACA 632615 Half wing width 300mm, root chord 100mm tip chord 50mm shows structural warning at root in aluminum



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Second iteration 250mm half wing, 150 root chord, 50mm tip
These are half wing numbers, be sure to double the lfit, drag and watts numbers for a full wing.

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Yes, I am also a proponent of a larger wing and a greater distance between front rear. U Kite Foil helps the dragon itself drag the sliders up

some software simulation explorations with variations of attack angles and the effect on lift. This is the base configuration.

The goal would be to get up on foil at as low a speed as possible, yet when at a high speed have reduced lift and reduced drag. This increased angle would be controlled by the inclination of the board itself, nose up angle more lift, full cruising speed, horizontal, controlled amount of lift. Ten degrees seems like a maximum.

NACA profile 632615 suggested by Clarin.

0 degrees, lift and drag in Newtons for a half wing (double values for full front foil)


1 degree, lift and drag in Newtons for a half wing (double values for full front foil)

2 degrees, lift and drag in Newtons for a half wing (double values for full front foil)

3 degrees, lift and drag in Newtons for a half wing (double values for full front foil)

4 degrees, lift and drag in Newtons for a half wing (double values for full front foil)

5 degrees

6 degrees

7 degrees

8 degrees

9 degrees

10 degrees

The preliminary analysis of the tail showed 39% of the front foil lift. The following table converts the Newtons to kiograms, doubles the values, and adds the tail values for a total lift in kilos at the various angles of attack and meters per second. Values under 150 kilos are colored blue, values above, yellow.

It seems like the range of lift can be controlled by board inclination, now to try more foil shapes and sizes and aim for more lift at lower speed, and less lift at 0 degrees.

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Great info thanks! Do you think we could add some twist on the last 10-15cm of the foil? This would give more lift at lower speed and as speed increases the twist would “flatten” due to the flexion of the foil.

As my understanding of simulating foil characteristics in software expands. The effect of attack angle factors in, more attack angle at lower speeds give more lift. Many foils do not have increased drag at these lower angles, but the advantage of flattening out the angle at speed reduces the excessive overall lift. Some diagrams.

0 degrees sitting in the water.

5 degree as kneeling starter position, could be more, the foil angle has also naturally increased.

5 degrees

10 degrees

Hy, I didn`t get with what reynolds numbers you are calculating in the program?

Yes 11° pitch is possible with the right profile and makes it much more stable during landing and Lifft off;-)

Using the program suggested defaults currently. the program calculates Reynolds numbers from 10,000 to 5,000,000 or allow a specific number to be input. This is an example of the foil selection dialog Reynolds section.

My understanding of Reynolds number is far from complete.

Hi I am Kalle from Finland. We ( my 5 friends) have build running efoil, but we have no simulation back round for the foils and propulsion. I have done rough calculations with basic physics. Can you help us to verify our foil and duct/prop calculations? We are looking after better foil and prop combination.
This is our foil gliding on cold (+6°C) the Baltic Sea last month.

https://www.youtube.com/results?search_query=e+foil+on+cold+baltic+sea

kalle & others

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You should concentrate your calculations on Reynolds Numbers below 500000 :wink:

The last few weeks I have build a new front wing, it’s 900cm2 and 125cm wide the tip chord is only 2cm.
It really looks like a bad ass slicer, sadly it’s almost impossible to ride!
The roll stability is so hard to control, it balances from right to left and I can’t fly centred. The takeoff speed is about 9knots which is one knots better than my Alpinefoil ULW900 both have 900cm2 (the shorter foil on the photo)
The foil center of gravity turned out to be about 20mm more forward, maybe, this is the reason of the roll instability or maybe I will need to change the rear wing?

The molds been covered with epoxy

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Awesome job, how was efficiency? Would not like to fall on that tip tho:p

Beautiful massive wing!

Do you know if it bends under load? Dihedral on a front wing is terrible for our type of hydrofoil control.

If my theory is right, then you might still be able to use it. Try to give it a serious amount of anhedral. You probably need to cut off the wingtips 30% of the way from the center. Then carefully glue them on at an angle so that the middle of the wing is around 13cm higher than the wingtips. (wrap the joints in carbon fiber to get strength).

I expect it to become usable that way.

Dihedral on the rear wing could help, but I doubt you will get enough roll-yaw coupling from a small rear wing when the main wing is so wide.