All this is becoming too much of a project for what will likely be a
one-time event for my plane.  If I plan to do any serious competition at
Reno in future years.  I need: a new airframe with less drag and a
higher
Vne (most likely dedicated to racing), a 3 or 4 rotor, more time, and
more
money  :-)

--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net <http://n4vy.rotaryroster.net/
http://RotaryRoster.net <http://rotaryroster.net/


I am thinking of putting retractable gear on the RV4. I am sure I will
get a
lot of static from Van if he hears about it.  It is real easy to move
the
stock fuel tank outboard and add a root strake to house the wheel.  Much
like a P51.  I will need to find a thiner wheel of some sort that will
fit.

With Mike's skinny cowl it will look just like a P40. Van warns about
putting fuel in the outer wing panels as he is worried about increased
the
polar moment of inertia about a vertical axis in a spin.

What he is not telling you is he failed to put a strake on the RV
vertical
stabilizer like almost every other airplane in the world has includuing
most all Cessna's and the P51.  When the aircraft is in a spin a strake
generates a powerful vortex and low pressure area on the down wind
sideof
the strake tending to retard the spin.  That is easy to add to an RV as
there is already a fiberglass fairing back there.

I suspect a lot of RV'er would like to retrofit their RV's with
retractable
mains.

Paul Lamar


Paul,  It looks like you could use a ball screw to operate the gear and
have an access hole for a manual crank on the sidewall of the cockpit as
a
backup if the motor is unoperative.

george grimes

What would work great is an RX8 electric rack and pinion.
The motor is hollow with the ball screw passing through it.

Paul Lamar

Hello Paul,

We run into this when looking to Harmon Rocket modifications, á la Bruce
Bohannon B-1

RV-4 Retracts:
http://www.vansairforce.com/community/showthread.php?t=48338

RV-8 version, page 8:
http://www.vansaircraft.com/RVator/2008/3-2008-RVator.pdf

Fuel tank schemes:
http://napwars.com/RV-8HTML/Fuel.htm

Bruce Bohannon's modifed RV-4:
http://www.avweb.com/news/profiles/181769-1.html

The idea was to make a "Cosmo Rocket" on basis of Harmon Rocket 2 and
twin-turbo 20B, and use it as "Vertical Drag Racer".
With 500-700 Hp, climb rate would be just insane :)

To use that as a Reno racer is possible too, but Vne is rather
limiting - even with HR2/HR3 wing.

Cheers,
Petri


Thanks for the links Petri. Can you get the attached pictures from
the Bohannon link? My browser is having problems with those.

It all depends on how far you want to push VNE. Most of these
airplanes, where it is not paying off, are 180 HP or below and
flying near VNE.

Dave Anders went 256 MPH in his 250 HP Lyc RV4 with a constant speed
prop. My ex hangar neighbor Tracy Saylor went 237 MPH in his Lyc RV6 in
the Sun n Fun 100.  Also with about 220 HP and a metal constant speed prop.

Allen Tole Went 238 MPH in the Sun n Fun 100 with the early Power Sport
rotary p-port powered RV3 or RV4 I forget which. Steve B?

The dynamic pressure at
250 MPH is 162 pounds per square foot compared to 104 at RV VNE
of 200 MPH. Obviously there is more safety margin in there than Van
claims.

One guys weight estimate of 250 pounds additional is too high.
Don't forget one loses the weight of the standard gear.

However when testing I recommend a jettisonable canopy and a parachute :)
Just in case Van is right :)

I also considered a whole new carbon fiber thinner, tapered wing along with
the retract :)

Paul Lamar


Paul,

I had considered retractable gear for my RV-4, but I was looking at having
it retract outboard and stow behind the spar, like a Spitfire.  There is
lots of room in the wing and the fuel tanks could stay where they are.
There is also a lot of structure inboard where the trunnions would be.

Steve Brazil

There is room back there for a nose gear airplane retract but
it complicates the gear for a tail dragger. The wheels have
to be ahead of the CG of course. The gear has to get around the spar.
A lot depends on the spar or spar(s) locations. Perhaps a two spar
wing would be easier. The RV's have the spar near the 1/4 cord
point which is generally the center of lift on a wing. It is in
the category more or less of a one spar wing.

The Brits tended to use the 2 spar design with the front spar
further forward. That meant the gear could be behind the spar.
I tend to agree with that.

BTW I just finished a book on the the
development of the P51 called "Mustang Designer Edgar Schmued and
the P-51" By Ray Wagner. The Brits criticized the P-51 as being too
heavy. North American initially used higher design G limits load factors
than the Brits. When the Mustang P51-G was redesigned for the lighter weight
using the Brit G limits it came out about 600 pounds lighter. The redesign
used thiner (.042 instead of 065) 25-T6 skins in some areas. 7075T6 was
invented
about that time but it was in short supply so North American decided
to make their own 25-T6. Page 140.

One of the controversial parts was the motor mount. According to
the Brits the motor mount saw no side loads. The Americans said
yes it does. When I was designing the motor mounts for the rotary
installations I sided with the Americans and installed lateral
support bracing :)

Paul Lamar



The spar is at about the same % chord on the RV as the Spitfire, look at
your drawing.  The trick is that the angle of the turnnion axis makes the
wheels swing forward.  On the Spitfire, they didn't move as far forward as
they might otherwise resulting in the Spitfire being light on the tailwheel
and the pilots having to be careful about nosing over, however the light
tailwheel helped compensate for the narrow track with respect to
ground looping potential.  I think the Sea Fury used the two-spar
configuration with the gear in between.

Steve Brazil

It is an elliptical wing so the 1/4 cord point is further back.

Paul Lamar