Nice to see the Darkaero guys load test their wing. They also mentioned that during the test they were verifying that the ailerons still worked under load.

Seems like they are taking a systems engineering approach to design and development.

Go to the 2:30 or so mark on this vid.

https://youtu.be/WamtmKiDIKs

I don't get how they are transmitting torque effectively in that manner. I would expect aero loads to easily displace one end of that tube.

I would have expected to see push/pull tubes.

Thoughts?

Agreed

That aileron linkage looks like a torsional spring waiting to make flutter....

See attached screen shot of the push/pull tubes they are using to activate the ailerons. They can change the force required to move the ailerons by moving the lever arms on the brackets in the flight control system.

The attachment on the wing is pretty beefy, it looks like at least 1/4 inch thick graphite and the aluminum bracket looks just as large.

I'm referring to the long tube that goes off to the left. It appears to rotate along an arc, translating, I assume, that motion to a similar crank at the other end.

The closest thing I can think of to explain my concern is an ice cube tray. Picture how you twist an ice cube tray to release the cubes.

I picture the bell crank on the aileron end as being able to move (or not move) quite a bit relative to the input end.

I'd like to learn how I am mistaken.

The amount of force as well as flutter margins are managed by how the ailerons are balanced. Some ailerons use aerodynamic force for balance others use a mass balance weight.

The ailerons on Darkaero have a mass balance weight ahead of the hinge line which helps determine the force required to move the aileron.

See the attached pics...

Traditional tubes are used in pure compression/tension push/pull roles. Those in the video are used to transmit a rotational load from the hinge point inboard of the flap to the hinge point outboard of the flap, but off axis - pure moment load. For that design to work, there has to be zero angular deflection at the joint on either end of the tube due to the resultant moments. From the video, I don't see how that's possible. Why wouldn't they just have mounted the tube centered on the hinge points so that it's a rotational/torsional load (which a torque tube resists very well) vs a translational movement with moment loads at the tube/plate joint like they did for the aileron torque tubes inside the fuselage?

Did you notice, it is not meant to fly, it is a boat? They talk range in sea miles - 1,700sm, not nautical miles .

I was thinking the same thing as Brett. As long as there’s no play in the the system and that tube is totally rigid it may work fine, but I don’t think that’s realistic.

How much force will the ailerons feel from the slipstream?

What kind of boating do you do that’s in statute miles?

What does the BT Brain Trust think of the 275 mph cruise prediction at 11 gph for the DarkAero?

GIGO

Its very light (1500 pounds max gross) 2 person, so 200HP will probably let it fly pretty high where efficiency isn't bad. Clean airframe and only a little over 1/2 the weight of a mooney M20J.

Wing loading is 23 pounds/square foot, compared to a M20J 14.5. That suggests

Stall speed is 60 knots (an M20J is 53 knots)

M20J claims 170 knots max cruise. This plane claims 240.

The engine claims 105HP at 20,000' That is still higher power to weight than a M20J at 5000'.

Even putting all that together 240 KTAS seems high, but not sure its crazy

It's ~10% than a Lancair 360 and has 10% more power, and looks like significantly less cooling drag. That's not going to equal a 40 mph speed boost, but it will be a boost. If the engine mount and the aileron torque tubes are robust enough (those are the only items that look questionable to me), my money is on about 250 mph.

But I also bet that after they fly it for a year they find a bunch of things that need to be beefed up and add another 100 pounds.