ArrowCopter sets new speed record

ckurz7000

Senior Member
Jean Claude,

I thought that the equivalent area is derived from the drag force equation:

D = 1/2 * rho * Cd * A * v^2 by expressing A.

It seems you are saying the the equivalent area is A*Cd. If that's the case, you would need to multiply my results by the drag coefficient of a flat plate.

Main uncertainty is the airspeed.

Yes, if you have a rotor model which calculates disk AoA as a function of (among others) air speed. I can fly a quick ASI calibration at 200 km/h to give you accurate airspeed. However, It will be between 190 and 210 km/h. There seems to be not too much variation in the drag area, so maybe an error of +/- 0.06 m^2. That's pretty good.

In my post # 26, I mentioned that my calculation is for a 8.6 x 0.2 m rotor, without being contradicted.

That is correct. However, I have reached 225 km/h on several occasions. The ASI calibration may, hover, be not very good at speeds that high. Remember, that we set Vne at 195 km/h. It only needs to be accurate up to Vne.

Greetings, -- Chris.

Jean Claude

Junior Member
Yes Chris. I am saying of "drag area": A.Cd
Flat plate of 1 m2 is a drag area of 1.2 m2 because his Cd = 1.2
For C20 I think A.Cd = 0,35 m2 is close of reality. Not a feat.

Big Cierva with his big radial engine, his big body, his forest of masts, his big wheels, and the passengers' heads outside, had only A.Cd = 0.67

ckurz7000

Senior Member
With my simple calculation I get 0.30 m^2 (using the proper air density and definition of "drag area") you get 0.35 m^2. Not too shabby.

I never claimed it couldn't be improved. We also agree how, aerodynamically, it could be improved. What I simply don't care about is the derogatory attidtude. Currently, I don't think there is a faster gyro on the market in its weight class. I might be wrong, but whoever flies it first has to prove it.

-- Chris.

P.S.: The equivalent drag area is probably defined somewhere as S*Cd. However, I would find it more elucidating if it were simply S, with Cd=1.2. That way I can simply say the drag area of X is equivalent to a flat plate of area X. But there's no arguing with definition. That's what you get when you let engineers define things

Paul Salmon MD

Member
Hey Chris,
Congratulations, I haven't seen you since we did your proficiency check at Smart field, I'll be looking for more record attempts from you in the future!! Keep in touch. By the way, my E-mail address is [email protected], drop me a line now and then to let me know what your up to!!

Paul Salmon

twistair

Living in the Skies
Seeing is believing, Alex. With this lightweight Rotax and 500 kg total weight for that flight I was able to cruise at 200 km/h.

Climb rate at the MTOW of 560 kg is still 900 fpm.

-- Chris.

When I spoke about weight, Chris, I mostly thought about maneuverability and flight dynamics - this is why I love gyros. To fly fast and economical one needs not a gyro.

Jean Claude

Junior Member
Currently, I don't think there is a faster gyro on the market in its weight class.

On this point you are right, Chris. But when the high forward speed is the goal, then it seems to me that the work of designers must focused not only on:
- Closed cockpit
- Cosmetics
They should not neglect:
- reducing the frontal area (A)
- the good collage of the flow on the rear walls (Cd)
- lightweight (induced drag)
- the required corrections on the blades (less pich, more chord)
This is just my opinion.

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ckurz7000

Senior Member
It is not just closed cockpit and cosmetics. You are forgetting, e.g., the stub wings. But, as I said, to design any aircraft is foremost an exercise in compromising and weighing benefits in one area which become liabilities in another.

I take note of the fact that if you designed a gyro it would be a different gyro. The same can be said for me as well, although it would be very similar to the ArrowCopter. I would be greatful if we could leave it at that since I like to focus on the joy and art of flying and am getting tired of arguments in the category of "Eurotub" bashing.

-- Chris.

Steve_UK

Active Member
yup it certainly is soporific.

Next year is 2017.

Rambler

Banned
I have some Ambien to help you out with that problem Steve.

Steve_UK

Active Member
That's mighty kind.

Let me say again - congratulations to Chris, Arrowcopter and those of you living in 2016.

Jean Claude

Junior Member
I would be greatful if we could leave it at that since I like to focus on the joy and art of flying and am getting tired of arguments in the category of "Eurotub" bashing.
Chris, nobody forces you to oppose technical arguments when there is none.
I have nothing to say about the joys of flight in AC20. I do not know and that was not my point.

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Kevin_Richey

Yamaha gyro...Oregon, USA
Congratulations, Chris!

Congratulations, Chris!

Since I've only flown to approximately 100 mph in my open frame machine, I cannot imagine going that fast in a gyroplane...I've been doing the kph to mph math and it appears that you can go about 120mph in cruise, and 140 mph top speed...

The Arrow Copter must be amazing to behold in person.

I didn't see any Euro-tub bashing occuring. Were some comments deleted?

ckurz7000

Senior Member
Hi Kevin, thanks for the post and appreciation. It is a nice feeling going that fast although to many fixed wing pilots this will not be anything to write home about.

No Eurobashing in this thread, although it's subtle.

Wish you zhe best and loads of fun flying, -- Chris.

loftus

Super Member
Congratulations Chris; I don't think there's any doubt the Arrowcopter is top of the class.
If I was not spending my cash on an Aircam build coming up; it would be the aircraft I'd aspire to.

ckurz7000

Senior Member
Thanks for the post and good luck with your build. The Aircam is one fun plane to fly!

-- Chris.

kolibri282

Super Member
Congratulations Chris! Great idea to promote the sport by showing what a good pilot can do with modern gear.

Resasi

Gold Supporter
Chris was wondering when ArrowCopter would be using the 915 IS?

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