G'day Paul
I flew my RV7 Rensis for the first time today. All went well, except for
the heat radiating from the Tangential Muffler, more shielding coming up.
A question for the Propeller people.
Static full power run gives 5900 rpm with no cowls on and the 68"X86"
Prince P tip prop. However the max I can on take off is 5200 rpm.
Does this mean the prop. is stalled when static? Does a stalled prop.
spin faster than an unstalled one?
 The other possibility is that the [carb] air intake  under the cowl  is
drawing in very hot air.

Ian Beadle Western Australia.

Great news Ian. Congratulations. You built that thing in
record time. My guess is.. it being your second rotary powered
RV really helped. I'll see if Robin and I can get over there
in the next year or two and go for another ride. Are you still
at the same airport and hangar?

Don ought to hire you to help finish his Mustang II.
You now qualify as an expert rotary engine installer.


Well it depends on your definition of stalled.
I have heard of that condition before. Typically people refer
to that condition as the prop starting to "bite" when the airplane
starts moving. Do you have the 2.85:1 or the 2.17:1 gear ratio?

Please send me some more pictures of your cowl opening and rad
configuration and I will try to figure out what is going one.

In the mean time here are some old pictures of Ian's first airplane
and hanger for the realatively new guys.

The last picture is Ian's new TB and intake air filter.
My guess is the intake runners are too short for 5900 RPM.
They need to be 22 to 24 inches long or there abouts for a
2.17 gear box. Shorter for a 2.85:1 gear box. 18 inches or so.

A 180 degree cold air  ram air scoop coming up and out
of the top of the cowling will help. See the 3D. The last
thing you should change is the prop pitch.

Paul Lamar ...No rotor no motor.

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Paul,

I'm also building a similar type of intake manifold for my Renesis, as
previously posted.  Target rpms are currently 6500 with the 2.17 drive
(and a short, 65" prop).  This is prop rpm of 3,000, and a tip speed of
.74 mach (580 mph).  This is fast, but is still a lot slower than  Warp
Drive's recommended rpm for this size prop.

You had mentioned before that a short intake manifold wouldn't make any
real difference in this rpm range on a Renesis.  Should I not be
pursing this type of intake manifold?

Scott Gettings

I don't recall saying a real difference at 6500 RPM. I was assuming
7500 RPM because you had an RX8 engine. I was also assuming bell
mouths inside the short runners. Maybe I missed the fact you had
a 2.17:1 GB.


If I were all you guys I would forget the silly side ports.
That goes double for Mistral that are casting their own side
and rotor housings. It is much MUCH  easier to cast end
and center housings with out side ports. They would have a
lot easier time selling their engines if they had 240 HP
or more on the 2 rotor and 360 HP on the 3 rotor normally
aspirated. Current ratings are 190 HP and 285 or so.
Their intake manifolds would be cheaper to make
in the bargain.

Everette Hatch built P-port engines 20 years ago and Allan
Tolle went 238 MPH in the Sun 100 race. We built a p-port engine
and got 240 HP on the dyno at 6500 RPM with a carb no less. How
much more evidence do you need?

In your case Scott the 65 inch prop will help but I don't
think you are going to see 3000 prop RPM.

-- 
Paul Lamar ...No rotor no motor.

Thanks, Paul.   I can go up to 7500 rpm if necessary, but this would
give 3456 prop rpm -- very fast, but still lower than the recommended
3700 rpm for this short of a prop --- according to Warp Drive.  In
worst case, I can always switch out the redrive to a low-ratio version.

I have bellmouths inside the plenum, ported into the 1/4" base plate.
They have a minimum of 1/4" radius, as per your previous
recommendations.

Scott Gettings

Somebody is pulling your leg. A 65 inch dia. prop is not going to go 3700 RPM.
I think you can still add longer runners. Here is a better 3D of what
I am talking about. You need a longer prop anyway to get the low speed
thrust you will need to get on the step and out of the water.
I would change the drive to 2.85:1 and add longer runners.