03-18-2011, 12:40 PM
Here's the project for those who want the fastest transit from one grass patch to the next:
Seems there's no kit available as yet....;-)
PS: The very intersting article below that Dave has dug up lists an awsome array of problems to overcome, yet todays very fast sensors/actuators/controlers might overcome these....unfortunately we might have to wait for a pretty wealthy nut to tackle them.
03-18-2011, 08:54 PM
Here is a stopped rotor that 'might' be of interest.
Stopped Rotor - Boeing is Still a Believer
The following is from a report entitled "CONSIDERATIONS OF THE STOPPED ROTOR V/STOL CONCEPT" It is for larger craft but it does mention the concerns.
This report may have been produced before the above idea.
NASA sponsored studies of V/STOL concepts for
short-haul commercial transport aircraft showthat additional
research is required to determine the relative
merits of various stowed rotor VTOL configurations.
In comparison with many other V/STOL concepts, the
studies ranked the stowed rotor concept from the best
to the worst. These differences in rank show that the
stowed rotor state-of-the-art is not well defined. Additional
research is required to determine the potentialof
the stowed rotor concept. There are many problems
associated with the rotor start-stop process. Of particular
concern are rotor control, rotor and aircraft
response to gusts, and rotor vibratory loads during the
start-stop process. Also, the aerodynamic and aeroelastic
characteristics of the stopped and folded rotor
are important. Experimental investigations in the fullscale
wind tunnel that have been conducted to date show
1. With the rotor folded in the trailed position, considerable
flapwise bending of the blades occurred in the
turbulent wake of the hub. It may be necessary to equip
the blades with bumpers or latches to prevent damage
when folded to an overlapped position. Otherwise, the
overlapped position must be avoided, and a rotor stowage
volume penalty may result. The dragof thefolded
rotor was about I square feet, which was greater than
the minimum drag of the wing-fuselage model without
2. Significant aeroelastic effects of the stopped
rotor blade were encountered. Extrapolation of these
results indicated an aeroelastic divergence speed of
about 200 knots for the blades tested.
3. Negative and positive automatic cyclic blade
feathering must be provided to alleviate gust loads.
Therefore, a rotor shaft angle of attack near zero will
be required during the rotor start-stop process.
4. Large shaft moments were produced during
stops and starts even at zero degrees of rotor shaft
angle of attack.
5. Large amounts of cyclic feathering are required
to eliminate the steady shaft moment even with the rotor
unloaded and at zero degrees angle of attack.
6. Wing design should incorporate high lift technology
to provide the lowest possible flight speed for the
rotor start-stop process, while maintaining high wing
loading for efficient cruise flight. Because of rotor
shaft angle of attack limitations, it will not be possible
to attain high wing lift by utilizing high wing angle of
7. The measured oscillatory shaft moments contained
large third harmonic components. These moments
would result in vibration transmitted to the fuselage during
the start-stop process.
The above results suggest that an automatic scheduling
of blade cyclic feathering as a function of airspeed,
angle of attack, and rotor rotational speed, will be required
to control the large steady shaft moments and the
large oscillatory loads (and therefore fuselage vibrations)
during rotor starts and stops in gusty air. Additional
research is required to define the cyclic blade angles
required for such a schedule. This research would determine
blade loads, shaft moments, control capabilities,
and vibration levels corresponding to the optimumcyclic
feathering schedule. After this basic research has been
accomplished, the feasibility of starting and stopping a
rotor in gusty air could then be assessed.
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