Gyro speed!

[Coen]

Hi could anybody please tell me why, according to the people who fly the tandem gyro's like the MAGNI and the ELA, fly better than even the SPARROW HAWK and why would these gyro's have a better cruise speed they say.

[Harry_S.]

One reason...Frontal Area?!


Cheers

[steveb]

.. and how about weight? Typical MAUW on a tandem 2-seater is 450kg. A Sparrowhawk tips in at over 600kg as I recall - like carrying nearly two extra people.

Steve

[C. Beaty]

The rotor limited top speed of a gyro is ~35% of rotor peripheral speed by which time, the stick will be near or on the forward stop. Some of the 1930s Autogiros were flown as fast as 50% of rotor tip speed but 35% should be regarded as a normal maximum.

A rotor is draggy with tips moving 3 or 4 times as fast as the rest of the machine but that’s not the whole story.

Most gyros being flown today have fuselage drag far in excess of rotor drag.

Side-by-side seating presents an exceptionally difficult problem in streamlining with a pusher propeller.

A cabin with streamlined nose chopped off abruptly behind the seats can never have a drag of less than ~35% of a flat plate of the same cross sectional area. The form drag is proportional to the size of the wake and the chopping off leaves an enormous wake.

Airships such as the Goodyear blimp have drags in the range of 5% of a flat plate of the same area.

Keeping the airflow attached is seldom a problem from the leading edge to maximum thickness but the rear half is a challenge. If the tailcone angle is too broad, the airflow will separate and burble off as though it wasn’t there.

I expect keeping the flow attached on a S-B-S pusher would require a very large diameter prop spinner.

Tractors present less of a problem, even S-B-S because the tailcone inherently has a shallow angle.

[OzyRuss]

Query........

if we ducted some air flow from over the top of the cabin, and in from the sides, to the problem area behind the cabin........would this ease that drag problem there ???????

Am building a RAF.......so I'm interested.....

[C. Beaty]

Maybe if you dimpled your cabin like a golf ball………..

I think the only thing that helps, and then just a little, is a belt of vortex generators like on the underbelly of a Cessna Mixmaster.

Pat McNear, here in Florida, has been playing with them and thinks his cruise speed may have increased slightly.

The main purpose of these things is to eliminate the waggle with the doors on. A vortex is alternately shed from each side.

[OzyRuss]

So...................this drag thing behind the cabin is not that big of a hinderence. Like it's not worth the effort to reduce it........sort of

What about this raising of the engine mass/ cabin etc, then stepping the keel, tall tails etc etc......??????

Sorry to bring this up.............it's probably been covered else where. If so, head me in the rite direction

thanks in advance.........