George,
     > > > I think you missed one point, my single rotor is based on 12A
   parts. I
     > > > extrapolated to 13B you are looking at around 150hp at 7500RPM.
     > > >
     > > > Richard Sohn
     > > > N2071U
     > > >
     > >
     > > I guess I've also missed some of the info provided by Richard
   and Paul,
     > > I'll go back and check. While Richard's work on the single
   rotor was
     > > interesting, I'd figured I would need a two rotor to provide
   enough
     > > power for the Vision acft. But, that plane is limited to 300
   lbs FWF,
     > > so it is right on the borderline for using a 13B (if we
   include the
     > > PSRU, engine, mounts, cooling plumbing, etc). Now, if we could get
     > > 150HP reliably from a single rotor, that might be just the ticket.
     > >
     > > Last time I looked at it, the incremental weight savings from
     > > eliminating one rotor didn't seem to be worth it for this
   application
     > > (given the development work required and the potential for
   decreased
     > > smoothness and reduced redundancy). Maybe I need to keep an
   open mind
     > > about the potential for using a single rotor 13B as Richard
   continues to
     > > open these doors.
     > >
     > > Mark Waldron
     >
     > Mark,
     > My single development is designed for the Vision aircraft, Steve
   suggests
     > best power is between 115 and 125 HP. Weight will be under the
   300 lb FF
     > limit for the single.
     > You could use a 2 rotor in a Vision and move the wings forward,
   Steve
     > suggested some time ago a 400 FF limit would require 4" forward
   travel of
     > the spar ( approx). All design changes should be approved by the
   designer.
     > You could also use some weight in the tail of the plane, because
   of the
     > fulcrum effect the weight would be much less than the extra FF
   weight.
     > Some are planning 2 rotor installations.
     > George ( down under)

   George,
     I'm glad you are still going with the Vision, and with the single
   rotor
   development.  I was thinking we could get the weight/balance in line by
   going with radiators (oil and water) mounted aft of the CG.   I had
   thought the 300 lb FWF limit was a function of the limit of the
   spar/fuselage shear web (?) design strength, not CG.  I'm probably
   misremembering it.

     I want to be able to safely fly at the heavy side of the envelope
   (approx 1800 lbs GW, with slotted flaps and the long wing).

   Regarding moving the wing forward:  Any variation from plans introduces
   complexity/delay, but it might be worth it if the alternative is
   insufficient nose-up trim ability.   I'd do it if I couldn't get a
   satisfactory result with battery/radiator placement.   Plus, it will
   give an excuse (since I'm already "off the reservation") to explore
   removable wings.  Thus the spiral of complexity widens . . .

   What do you believe your single rotor engine will weigh?

   Mark Waldron


I suspect that the engine mount and cowl design would be one of the last
pieces of the puzzle. Being able to move the engine fore and aft a
couple of inches, can put the CG dead nuts on target.

Adding weight to the tail post, or a car battery behind the rear seat in
order to get the CG right, is adding polar moment.  The outcome may be a
plane that needs constant rudder attention, and may spin gleefully, but
not recover well, or at all.

Lynn E. Hanover

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