Flettner rotors were
at one time believed to be the next big thing in air-driven propulsion. They would
replace cloth sails on boats and fixed wings on aeroplanes. I remember seeing such
fantastic contraptions in magazines like Mechanix Illustrated and Popular
Mechanics back in the 1960's and 1970's. The
nouveau sails and
wings were actually built on experimental vehicles which can be found in a Google
rotor. They operate on the
Magnus effect, which is
where a lifting force is generated by a spinning sphere or cylinder moving through
the air (or water, or any fluid), thereby causing an unequal pressure to build on
opposite sides. I had a Magnus rotor kite as a kid in the late 1960's that was made
of thin, molded plastic. It flew pretty darn well if I remember correctly. This
curiosity-inducing control line model designed by Roy Clough exploits the Magnus
rotor effect. It is more of a novelty proof-of-concept platform rather than a stunt
or scale model.
Flettner-Type Rotor Wing-Control Line Model
You'll Find It Fun to Fly This Flettner-Type
Rotor Wing Control Line Model
Nothing hard about this project! Best of all it's a great flyer.
By Roy L. Clough, Jr.
This novel control line model gets its lift from a pair of whirling Flettner-type
rotors which spin automatically in flight.
Easy to build and fly, the model is practically crashproof because the rotors
will keep turning whether the motor is running or not.
Although the model moves along at a fairly good clip in normal flight it can
be made to practically hover on the upwind side of the circle if the nose is raised
a bit. Center of gravity location in relationship to the rotor axis is not very
critical so a wide variety of small engines may be used without altering the model.
It is important, however, to have the control line guide set to allow the model
to nose slightly out of the circle, the same as for any ukie.
Construction Is of the Profile Type.
Fuselage is cut from medium hard 1/4" sheet
balsa. Motor mount is a plywood disk held rigidly in place by blocks cemented on
either side. Landing gear may be held either between the plies of the nose disk
or simply be set in a groove in the face of the disk and held in place by the rear
of the engine tank. Control horn and bellcrank are of the 'Tee' or Firebaby type
which are the best for profile fuselages.
A short wing stub fills the center section. A cabane strut on each side acts
as a brace. This provides support for the 3/32" wire rotor axle and allows a clear
wash-way to the tail surfaces. If you run the rotors right up to the fuselage sides
their interference will make elevator control uncertain at low speed.
Construction of the rotors is simple, but should be followed closely for best
results. The open center design was chosen after experiment with several types indicated
this design allowed the best forward speed maximums and minimums. It is essential
that the rotors be mounted as shown, so that the rotation is to the rear at the
top. If the rotors are installed backwards the model will not lift since the rotor
thrust will be downward instead of up.
The line guide is soldered to the tip of the inboard axle and is bent slightly
to the rear to insure the correct amount of nose-out without the necessity of a
separate rudder adjustment.
When you have your rotor-wing craft in operation, get a friend to snap a photo
for the magazine. American Modeler pays $10 apiece for the individual "shots" used
with its column reports!
Full size plans for Flettner-Type Rotor Wing on Plan No. 357 from Hobby Helpers.
770 Hunts Point Ave., New York 59, N. Y. (50c).
Flettner-Type Rotor Wing Control Line Model Plans
Posted October 20, 2018