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Flying Wing Commentary

Posted: Sat Oct 06, 2018 1:59 pm
by lightandfrost
Removing a hydrofoils stabilizer and riding the stock wing ie riding stabless increases the control requirements of the rider as the wing is unstable since nothing counters the wings center of pressure as it moves around the center of gravity. Furthermore there will be limits to the wings ability to function.

The design of flying wings is well researched. For home builders who wish to pursue the development of flying wing specific hydrofoils - here are some simple design suggestions.

1. The stabilizer and tail are replaced by a reflex which is a rectangular area on the trailing edge of the wing angled upward acting as the stabilizer

2. The wing should have some dyhedral which will help counter yaw-pitch-roll inherent in flying wings.

3. The wing should have two fences on each wing, and on both sides of the wing. These fences forward point should start behind the center of gravity

4. Small winglits on the wing tip should be installed to increase the Center of pressure area of the wing.

5. The wing shape could be designed symmetrical ie cambered both top and bottom. This would reduce center of pressure movement, increase the stability, but reduce lift.

There are plenty of pictures of flying wings. A primer for home builders can be found here.

The aerodynamics of flying wings part one and two

https://www.youtube.com/watch?v=gkb11eKXM14
https://www.youtube.com/watch?v=x2Cn3vIb6gw

Light and frost has begun a flying wing project and will post for community use as the wings are developed and tested.

Re: Flying Wing Commentary

Posted: Sat Oct 06, 2018 2:14 pm
by BWD
When L & F wrote “symmetrical” did “they” mean in the aerodynamic sense or the geometric sense?
Are “winglits” sharp or , erm, “blunted”
Why fences? They’ve been unnecessary on conventional, stables, and canard configurations so far...

Re: Flying Wing Commentary

Posted: Sat Oct 06, 2018 3:18 pm
by TomW
The reading I've done on wing design, I learned the literature uses the term " symmetrical wing" to mean the top and bottom surface has camber, but not necessarily the same or mirrored camber. So it's not really symmetrical, but it could be..
Asymmetric means one side is flat.

Re: Flying Wing Commentary

Posted: Sat Oct 06, 2018 3:39 pm
by jakemoore
939F637D-829D-40F4-B4FA-A45D0BCFC1EE.jpeg
939F637D-829D-40F4-B4FA-A45D0BCFC1EE.jpeg (21.22 KiB) Viewed 1727 times
I wonder why we don’t have more winglets, fences and dihedral on the flying wings so familiar to us already?

Closed cell foil kites definitely benefit from reflex. Open cell fixed bridle, less so. What about LEI?

Parallel for hydrofoil is user impulse can address pitch roll yaw, preventing front and back stall.

Re: Flying Wing Commentary

Posted: Fri Nov 02, 2018 9:39 pm
by Horst Sergio
Hi lightandfrost,

I was hopeing one day somebody will design a "flying wing only" monofoil wing. But after 2 years of testing more than 10 different wings and riding the most used three wings each about 20-100 times (AR 7 - 3,5 and 580 - 990 mm²):











My search for an ideal wing hasn't come to an end, but

most wings feel very well for monofoil. For sure the long cord and big wings are the most beginner friendly, but I also like the grey AR 7 a lot and I would expect even a AR 10 like this could ride very well:
Levitaz_front_wing_aspect_freeride_big-air_parts_HW.jpg
I think traditional kites and flying wings have nothing to do with monofoils, as the load point is not 5 times under the wingspan or within the wingspan, but for the monofoil it is 5 times above the wing! This can make every self stabilizing tricks ineffectiv.

While a kite with lost line tension acts like a flying wing and can form its reflex profile and therefore pitch easily up, a free flying monofoil even with the most extrem reflex profile will never pitch up as long the nose of the board above is 10 gramms to heavy, not talking about the situation with a rider on it.

Development for monofoils would be great and interesting, but IMHO it is much less about fences and winglets, but more about stiffness, harmonic lift curves with pitch, surfacing behaviour and safe round tips.

Re: Flying Wing Commentary

Posted: Fri Jan 18, 2019 3:01 am
by lightandfrost
L&f have completed step one in a flying wing project. A basic flying wing shape has been constructed without the reflex or elevons. This wing with standard stabilizer will be tuned and tested for functionality for a number of hours. If the wing is suitable the reflex(elevons) will be added having 1/8th the square area of the wing and a 5 degree positive angle of attack. The stabilizer and beaver tail will then be removed and test flown again.

A second wing with a semi-isochronus curved leading edge is also being constructed. This shape has already been tested and found functional so reflex(elevons) will be added during initial construction dependent on how tests on the first wing proceed.

Again we are open source non-profit and any info of note will be released for community use.

Re: Flying Wing Commentary

Posted: Sat Jan 19, 2019 2:49 am
by lightandfrost
To Horst Sergio

Your work is held in high regard here.

Reference stiffness. The smoothest wings L&f ever made had some flex much like standard aviation wings. Unfortunately a stress crack began to form along the major flex point. These wings were intentionally constructed to have this flex and were brought back in and the flex removed.

Since that time methods of allowing flex that did not result in a stress crack have been considered but currently no good ideas have formed. The wings can be made but their use-able lifespan is limited.