Dragon wings max revs

[Sapientino]

does anybody know max safe rpm for a dragon wings rotor? since my rotor is pretty little for the weight I have, it turns normally around 375 rpm, and it goes to 415 rpm in fast turns (I think I can go also to more rpm but I never tried)
Thank
Sapientino

ps dragon wings are really superb rotors, no shake at all (using taller teether hole) and a great efficiency.

[GyroRon]

I would say your okay on the speed. My first Dominator turned that fast with the 23 foot blades I had on it. You would get a slower takeoff and more float time in ground effect with a longer set of blades. but I see nothing wrong with your setup as long as your happy with the performance.

[C. Beaty]

Ernie ran a set of 23’ DWs at 600 rpm on a test stand without ill effect.

As a general rule, most rotor airfoils will begin to encounter compressibility at tip speeds of ~700 feet/second and start to tuck nosedown. That’s because local flow over the airfoil is accelerated and can exceed mach 1.

[Sapientino]

Ernie ran a set of 23’ DWs at 600 rpm on a test stand without ill effect.

As a general rule, most rotor airfoils will begin to encounter compressibility at tip speeds of ~700 feet/second and start to tuck nosedown. That’s because local flow over the airfoil is accelerated and can exceed mach 1.

That's what I need to know!!!!! now I can try more hard turns!!!!!! :D :D
Thanks
Sapientino :) :) :) :)

[Sapientino]

I would say your okay on the speed. My first Dominator turned that fast with the 23 foot blades I had on it. You would get a slower takeoff and more float time in ground effect with a longer set of blades. but I see nothing wrong with your setup as long as your happy with the performance.

ok thanks I'm really happy with the perfomances
Sapientino

[automan1223]

Hey chuck, I enjoy your articles in the pra rotorcraft mag. They are very informative. How about a rotor blade 101 for everything us nuts and bolts guys need to know kind of article like rotor rpms, pitch, etc.

say you had a 30' rotor what would be the max rpm you would recommend for safe op ? how slow ?

Jonathan

[Al_Hammer]

A related factoid: I remember reading on the old forum about Bill Clem's record setting flight to 24,000 ft or whatever it was. Seems he watched his rotor rpm get pretty high in the thin air, to the point that Ernie B. was urging him to come down.

[C. Beaty]

I remember rotor rpm being discussed while Bill Clem was on his way up, Al.

Ernie had several sets of blades of various diameters for Bill to try but I don’t recall specifics of diameter, rpm, etc.

My spreadsheet shows that for AUW of 700 lb. and 28’ diameter rotor, tip speed and rpm respectively are 631 fps and 430 rpm at 24,000’ and 429 fps and 293 rpm at sea level.

A tip speed of 631 fps is pretty high but probably not dangerous.

[C. Beaty]

Thanks, Jonathan.

Most of the stuff you ask about has been written and is in the pipeline.

[Al_Hammer]

My spreadsheet shows that for AUW of 700 lb. and 28’ diameter rotor, tip speed and rpm respectively are 631 fps and 430 rpm at 24,000’ and 429 fps and 293 rpm at sea level.

A tip speed of 631 fps is pretty high but probably not dangerous.

Thanks, Chuck.
So ,centrifugal load was about twice normal. (430/293) squared.

[automan1223]

Always ears open for more things to learn or review !

Now I can just picture this, ernie on the radio, getting nervous about his rotorblades on bills record setting flight. That had to be a hoot. ! Ernie to Bill: You gotta come down now. Bill was frozen if I recall reading correctly. Thats a great story.

Jonathan