Paul,

   No self-respecting constant speed prop today would be satisfied with
   under 85 percent efficiency. The big slow-turning ones on turboprops are
   just under 90 percent.

   If we assume 85 percent as a reasonable efficiency for a prop, then .83
   times 85 is 70.55 percent.

   Now you are claiming that internal duct drag will for a 10 percent
   loss? Did you not get my email about the calc on that HVC website. With
   the exact parameters I have been using in this discussion, it shows a
   pressure drop of less than one percent (.6 of one percent to be exact.)

   Regards,

   Gordon.

   That is for straight airflow.
   What you have inside a ducted fan is a vortex.
   Air molecules are like marbles. When you spin them
   around they tend to congregate out near the walls
   of the ducts. Nothing short of CFD is going to come
   close to telling you what losses you will have.
   As Matt says, build it and try it. Perry Mick worked
   on his for 13 years as I recall. He now uses a gear box
   and prop.

   Paul Lamar ...No rotor no motor.

In the interest of accuracy, this is not really correct Paul.
It was 13 years from the start of building my Long-EZ until first flight
- which was with a ducted fan. But I did not work on the ducted fan for
13 years.

I worked on the airframe from 1986 to 1997. I bought the rotary engine
January 1997, had it installed and was doing taxi testing with the first
ducted fan by Summer 1998. First flight was July 1999 on the second
ducted fan.

So actual ground experiments with ducted fans only consumed about 1 year
before first flight. I experimented with a third ducted fan after it was
flying.

I flew it for 500 hours with the ducted fan, until December 2004. Top
cruise speed achieved was 135 knots, engine speed 5400 RPM. With the
same engine (the engine has not been removed from the plane since 2001)
with RD1B and 62/68 3-blade prop top cruise speed is now 160 knots,
engine speed 6400 RPM. I am getting more power out of the engine now
since I can turn it up higher. Flying at 5400 RPM now, I am back around
130 knots again.

Some of the drag of the duct can be offset if the duct has a dual use as
a horizontal/vertical stabilizer. See my LSA proposal at
http://www.bridgingworlds.com/LSA.htm

Perry
http://www.ductedfan.com

Even tho the speed is the same at 5400 RPM the power generated
is less. One needs to know the intake manifold pressure at a
given RPM to determine the HP consumed.

What is the intake manifold pressure now at 5400 RPM Perry?