Stu,

I would be very cautious about using DARPA's seal of approval
to mean anything.

OK forget DARPA.

A couple of years ago the US Army requested concepts for a new heavy lift
helicopter. Bell proposed the quad-rotor V-44, Boeing proposed a
side-by-side configuration and Sikorsky proposed a single rotor with a
reverse velocity capability. Sikorsky's concept appears flawed [
http://www.synchrolite.com/1281.html#Potential_Problems ], which leaves
multiple main rotors as the only contenders.

OK forget what the big boys are doing ~ although it does suggest the future
of rotorcraft.

Let's consider simple low cost helicopters, similar to those that were built
in the beginning. Last year Tom Lawrence, a senior engineer at Sikorsky
Aircraft Corporation wrote; "However, the single greatest feature was Igor
Sikorsky's faith in the benefits of the single rotor helicopter. Much
derided at the time, the single-rotor configuration would come to dominate
the worlds helicopters." What an interesting statement. Those who "Much
derided" the single-rotor helicopter had good cause. They were not ignorant
people. In fact, some of the most knowledgeable rotorcraft people at that
time were in Germany. Both Flettner and Focke had built better helicopters
then Igor, before he built his. Perhaps Igor's "faith" was a sort of 'blind
faith'. Or, perhaps his faith was placed in marketing; to DARPA type
government employees.


Logic does not suggest that the twin main will cost less than
the main-tail ship unless you can produce in large quantities.

The main/tail rotor helicopter and the twin-main-rotor helicopter have the
same total number of blades and gears etc. The former has big parts and it
has small parts. The latter has only identical medium size parts, but twice
as many. Savings from volume production starts at 2-off. This is because
the machine setup cost, the purchasing cost, etc. etc. are now 1/2 per part
for what they would be for only 1-off.


I have a problem with Moller AirCar, Ezcopter, Skyscooter
and a few of the others....

Me too, but the Intermeshing helicopter is a proven configuration.


As I understand it the twin rotor machines
can have pedal reversal during autorotation.

The intermeshing helicopter does have pedal reversal during autorotation.
Offsetting this argument; the intermeshing helicopter (Flettner FL-282) was
the first helicopter to enter and exit autorotation. In addition, the US
armed services stopped using Kaman Huskie helicopters for training their
pilots because they were too easy to fly.

If someone starts building recreational twin-rotor helicopters, the people
will come.

Dave J.


"Kathryn & Stuart Fields" wrote in message
...

"Dave Jackson" wrote in message
news:jHK4d.83778$%S.11725@pd7tw2no...
Hi Stu,

Your concerns about price are understood, but for a counter argument;-

My background is in manufacturing, and more specifically, the
manufacturing
of equipment that is used to mechanize and automate the production and
assembly lines of other companies. Without qualification, it can be said
that the single largest contributor to lower prices, by far, is
'economies
of scale'
Boy do I understand that..I manufacture a rotor speed alarm system. It is
basically for the Safari, but easily modifiable to others. With the small
market the individual prices have to be high to cover my costs. I also
built some cyclic simulators that I thought should sell for $50. My cost
was closer to $200. If I could build 1,000... Yeah you were preaching to
the choir here.

Roughly speaking, the main-rotor/tail-rotor helicopter has twice as many
different types of parts as the twin-main-rotor helicopter. The
twin-main-rotor helicopter will have double the production run due to
the
commonality of parts. Logic suggests that the twin-main-rotor helicopter
will cost less than the main-rotor/tail-rotor helicopter.
Logic does not suggest that the twin main will cost less than the
main-tail
ship unless you can produce in large quantities. Logic obviously says
that
the main-tail is less costly for single items. Your argument may hold
water for some yet to be determined production numbers. Just remember the
market for kit helicopters is not large. If you go into the certified
ships, you will learn, as Frank Robinson has learned, there are some
overhead costs that can jack your costs up that aren't covered in a simple
economies of scale model..

In addition, latterly-located-twin-main-rotors have a number of
aerodynamic
advantages.
I agree here just based on what I see the Kamans doing.

I really believe that this configuration is the future of rotorcraft,
and
this future may arrive next month. The only current request for a new
helicopter in the USA is the DARPA competition for an Unmanned Combat
Armed
Rotorcraft. An intermeshing helicopter and a compound helicopter are
the
two finalists that are competing for the authorization to build a
prototype.
I used to have great respect for DARPA (I had an interface with them in
the
70's) until they pulled off that "Great Challenge", which they called a
"Success". I had inside poop from a guy working on the set up for that
FARCE. DARPA spent $12M on the setup for that event and only pre-tested
the
entrants on a flat well defined track. I think that the managers are
running DARPA now and apparently they don't understand tech issues very
well. I would be very cautious about using DARPA's seal of approval to
mean
anything.

I've begun to think that I'm talking about enjoying bigamy to a group
of Catholic priests.

There is no reason why the affeceadoes of recreational helicopters can't
start looking at the 'second coming of rotorcraft'. A little preaching
in
your new magazine might lead the unconverted out of the wilderness.
Dave: I have a problem with Moller AirCar, Ezcopter, Skyscooter and a few
of the others with their "positive forward thinking" when they haven't
built
and tested the item to really know what they are talking about. They
claim
"Easy to build and Easy to fly" and haven't built and tested the
prototype.
The Skyscooter does not have collective controls and I believe therefore
very questionable autorotation ability.. These have to be rectal
extractions since they haven't gone the whole route. I'm surprised at
people, however, a friend told me of an investment banker that tried to
dump
a bunch of bucks on an untried and unflied helicopter kit a few years ago
just based on the artist's conception. As I understand it the twin rotor
machines can have pedal reversal during autorotation. That would not be
something that I wanted to expereince during an engine out emergency.
I'm coming to the conclusion that this newsgroup has a different idea or
definition of recreational helicopters. A lot of the posts that I see are
coming from people interested in big $ commercial ships. Only a very
small
percentage of the posters seem to be involved in recreational rotorcraft
flying. .

Stu Fields