Paul and Jeff,

 Would there be any utility in not boring the cup mounting holes in
the motor
 plate, leaving that up to the builder of the plane?  All be it a small
 amount, one could have a little adjustment there.  Noting of course
that the
 space between the top of the motor plate nubbins and the cups would
need to
 be shimmed to allow for the benefit of that structural component.

 In addition, would there be an utility in making the cups out of
7075-T or
 2024-T as opposed to 6061-T?  Or, would that just be overkill?

 I am going to rat out Jeff here.   Dropped by to pay him a visit.  He
has a
 Cirrus-VK30 sitting to the side of his shop.  Jeff has hinted that it
is a
 prime candidate for a 4 rotor engine. . .

 Gordon

 A four rotor P-port would be up to 700 HP :)

 Paul Lamar


The common engine for the VK-30 is the IO-550G which has a dry weight
of 430lbs.  It seems that it might be possible to build a 4 rotor with
a similar installed weight.  That airplane has a problem with not
recovering from spins - a heavier engine would make that problem
worse, so it would be important to not increase the weight of the
engine.

It seems the VK-30 could benefit from larger carbon tail surfaces
(minimum weight, maximum area) and winglets (increasing the
aerodynamic area aft of the CG).

On a side topic, the Nemesis NXT flew the Reno course faster than
400mph this year.  The airplane is still using a direct drive
Lycoming.  It appears to me that the prop they are using is getting
shorter to allow the engine to turn faster without the prop tips going
super/trans sonic, and that they are making up the blade area by
increasing the chord.  Maybe it's just an optical illusion caused by
the large spinner they are using.  The airplane has a noticeably
higher pitched tone when going around the course than Eldridge's NXT
which also has a direct drive Lycoming..  With that in mind, maybe the
way to go with a pusher like the VK-30 is to use a relatively short
diameter prop with wide blades.  Not as efficient at low speeds, but
then again, probably not bad either.  Especially with constant speed.


Matt-


Matt

I need to reply here...there is only 1 guy that I know of flying with
the IO550. He flies out of Van Nyes . He sees 195 MPH at 800ft cruise...
Other  than the few that installed turbines the engine of choice was the
tsio550.

This engine is significantly heavier, well over 650 lbs. With baffling
and all the fans( 7 in one case and still ended up with an engine fire
that killed him) to keep it cool for ground ops even more. Factory
proto VK33 had this engine and the plane flew all the time many time 200
to 300 lbs more than published max gross..

Nobody ever built the plane to specs regarding weight, it was difficult
to do with all the AD's and modification made after the original design
was conceived.

The plane could handle the weight but was sensitive to CG and they all
tended to be aft..For every 1 lb on the tail saved,  2 lbs at the nose.
Factory had sand bags moved around depending on the number passengers on
board. It could hold 5.  I built a carbon fiber horizontal by Grove
Aircraft(now makes landing gear and brake systems here in San Diego. He
was the main structural engineer/consultant for the Global Hawk in
composites) that saved 25 lbs in the tail for that reason..

The wing is laminar and has a heavy wing load. Large fowler flaps can
cause trouble in very deep stalls with aft CG that the factory was
exploring when they lost one in test flying..Some would say the flaps
can effect the horizontal in a slow landing configuration..you land like
a twin and eliminate the typical flair.  When that wing quits flying, it
lets you know suddenly..

I had A Zehrback tio650 inverted water cooled  EFI V8 installed.
Documented dyno test shows 650HP and 900ft-lbs  .38lbs/hp...the prop is
Whirlwind 80" diam turning 2200 RPM.

I want to get a 4 rotor in there with a good reliable 450 HP.  I believe
the rotary, built like a real aircraft engine, would save an enormous
amount of weight and the long profile would allow for an easier
installation particularly for a mid engine configuration.

Like Forrest Gump says:  "That' all I have to say bout that"

jeff