Can we create the optimum wing first?

#21

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.

#22

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

#23

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.

#24

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.

#25

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

#26

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;-)

#27

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.

#28

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.