There is one other question in my mind. Are the fan tips

approaching super

sonic velocities and absorbing all the HP or are the fan blades

wide enough to generate as much thrust as possible? In other words, where is
the HP going?

Perhaps Vance can answer this question.
I still think you need to broad band that duct. Make a more

streamlined

lower drag duct such as found on turbo fan jets with a smaller

diameter opening and use the variable geometry opening. I still think it can
be done with an inflatable rubber lip.

Marc de since you are on here now perhaps you can help Perry extend

the speed range of his ducted fan. In other words reduce the high speed drag
from the duct with out losing too much low speed thrust.

Paul Lamar

With the duct you are "sucking down the inlet face of the duct at

static

for a forward thrusting pressure area term, but at high forward

speed

the inlet flow is overpowering that "suction" and you have an added

drag

component
With the duct removed you are aparrently "sucking down " the

significant

"base"
area on your plane, What rpm can you get at static? are you really

making

horsepower? Why does it work with the Subaru which is not that much
bigger than yours (Or do Subaru's just make more power than Wankels

(;<)!!

Vance

Ah So! Vance has a point here Perry. What he is saying the fan is

causing

a low pressure all over the back side of your cowl which translates

into high

drag. In other words the negative pressure vectors are perpendicular

to the

cowl surface so the backward facing components of the vectors are

adding

up to a lot of drag.

I forgot about that Vance. Good point.

Paul Lamar

As I've said before, I am not making that much power. Prop analysis

and

fuel burn indicate maybe 120 HP which agrees with Mazda specs. Stock
porting 1986. The potential is there for 180 HP on two rotors, so I'm
waiting for Jerry to get this PPort thing worked out.
As far as the Subaru guy, do I remember correctly that he is not

flying

that configuration any more? The VEZ is a 600 lb. airplane while the

LEZ

is a 1000 lb. airplane. I think he was turning maybe 3500 RPM and I'm
turning 5500 so his prop was still much larger than mine, around 50
inches I think it was? I'm guessing his plane must have been a runway
hog but it did ok once in the air.
Those goofy antique subarooo piston engines just can't turn up the rpm
like our superior rotary turbines Vance.
Perry

Perry, I also think you can make some drag reductions on your current

duct.

The one on the left is your current duct more or less and the one on
the right is lower drag because it is less cone shaped. In other words
the departure angle on the outside surface of the duct is less acute.
Any negative pressure vectors back there will have a high drag components.
Both ducts are designed to have the same inlet areas and the same
out let areas.

Paul Lamar

With the 38in dia at 5500 the tip speed is a tad above 900 fps, a bit high
for a typical thick wood prop but modest for metal or composite sections.
A search on net suggests that at least at one time the soob was running
about
50 inch dia and 60 in pitch - looking for 4000 where the Soob shoud be just
a tad over 100hp. I was suprised to hear that your exit area is greater than
the
fan area. This means that you are diffusing the flow velocity down before
exit. This cannot be good. Treating your whole plane as a controll volume,
thrust is the total air weght flow times the difference between entrance
velocity and exit velocity, so diffusing that exit flow is thrust loss.
Only sonic throat flow (ie rockets and turbojets) benifits from a
diverging exit. Vance

 
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