Hi Paul,
George Lendich said I should introduce myself to you and join your
rotary discussion group.
We have been talking about Rotary engines and construction methods for
the Stratos aircraft I am developing. He said he already wrote to you
about me.
A little background about me..(Will keep it brief)
My father designed an aircraft called the stratos. The original
aircraft
flew well, however when he started to produce the aircraft he made a
second Stratos that had aerodynamic changes that caused a severe
stall.
At low altitude it stalled unexpectedly and claimed his life. I have
the
original Stratos that I have been back engineering for a while. In six
months I aim to start building it (once I get a bigger workshop).
Until
then I am looking at different construction methods, motors and
finishing detailed CAD data etc. in preparation to building it. The
original Stratos was constructed similar to a vari-eze or dragonfly.
Right now I work for Boeing Australia as an Aero Engineer, I have
worked
on many aircraft professionally F35 variants, F18C/D, Eurofighter,
CH300, 777, 787. In disciplines of Concept design, Design for
manufacture, R+D, Testing.
I always liked rotaries but haven't until now seen them used in
private aircraft (besides the one-off). I studied ducted fans in
detail,
I don't know - I may/may not have something worthwhile to offer for
discussion?
Lastly George has gotten me onto a rotron axiro 40+hp turbo rotary.
If those figures are correct i am very impressed - it will extend my
flight envelope considerably.
Best Regards
Ron
Paul,
Ron's Stratos is a ducted fan design, he may be able to help in this area. I
know very little about ducts, but brief discussions with Ron indicated he
knew quite a lot.
George (down under)
Ducted fans are fine for low speed. As speed increases the drag of the duct
itself starts to affect the over all efficiency. Dozens of ducted fan
airplanes
have been designed and built and all have failed as viable aircraft.
There is no
way around it except remove the duct. Any object or surface you put in
the air stream
WILL increase the drag. Even powered parachutes don't use ducts.
If you want good low speed performance use a larger diameter propeller.
A helicopter
is a good example. Taken to it ultimate conclusion you have a VTOL or
tilt rotor.
http://www.rotaryeng.net/VTOL.html
Paul Lamar
Hi Paul,
I agree with you about high speed and the profile drag of the duct over
a certain velocity for a non-gas turbine engine.
I'm curious about those graphs. It says in a gas turbine a ducted
fan is more efficient at speed.
Static thrust on - I assume a short duct, appears to be better then a
plain propeller.
The problem with empirical data from graphs is that it doesn't tell
you what ring chord, profile, camber, thickness, radius is used. It
doesn't tell me what inner duct curvature there is to account for pre
and post fan, pressure velocity-area ratio. L/E radius? Did it have
stator/reaction blades? What tip gap was attained to reduce pressure
leakage on the tips? Was the duct attached to the motor or fuselage to
reduce tip gap because of vibration tolerance? Was it a pusher or
tractor config?
The design constraints on the Stratos caused it to have a duct, it has a
very small fan diameter because of ground clearance. Upon testing
with/without the duct the climb and cruise suffered without the duct.
There is a place for a duct if it is put on the aircraft for a reason
(small dia prop), not just to look cool, it has to be engineered
correctly too. Yep I agree, Tilt Rotor is a different Kettle of fish.
Although the F35 STOVL uses a ducted fan, advantages - more efficient
then a pure turbofan, increased payload, small diameter fan that fits
inside the fuselage, it's distance from CG will tell you how much
thrust it produces compared to the jet exhaust. And it stops the hot jet
exhaust gas from re-entering the inlet. It is a level ahead of the
harrier in many regards, because of a ducted fan.
Powered parachutes are interesting too, finally they are getting higher
horsepower motors. I wonder how big their fan diameters can get without
being cumbersome, give you a big torque kick on acceleration and still
be transportable in the boot of an average car? If they want something
with the same amount of thrust and a significantly smaller fan
diameter it might be worth some investigation?
Best Regards
ron
If you have enough HP to go 500 MPH ducted fans are your best choice.
The F35 uses if for static thrust only.
Good luck. Perry Mick tried for ten years.
http://www.mickaircraft.com/duckt.htm
Hey people please send plain text only. html text screws things up.
Paul Lamar
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