BTW I forget to mention something when we were talking about
your idea for more static air. Those slots will indeed provide
more static thrust by getting more air through the fan but with
the inflatable lips you get thrust from the air flowing over
the lips as well. I would say it would work twice as well at
a minimum. This is because the airflow causes a low pressure
on the inflatable lips as it flows around and over them.

If the ID is 36 inches and the OD is 48 inches or a six inch
wide inflatable lip that is about 252 square inches of projected area.
If the average pressure vector is 10 inches of water that is
.37 psi or about 100 pounds of additional static thrust.
I think a one foot wide inflatable lip or a five foot OD duct
for takeoff would be doable.

Paul Lamar

I may be sorry that I stepped into this conversation, but I am interested
in ducted fans (prop within a duct) but not sure that I have the time
right now to presue this at the moment.  Still It is a very interesting
subject, and concept so if anyone would care to step in and bring forth
the pros and cons of this configuration, I would appreciate it.  It would
give me food for thought, and maybe even a path to travel.
My very nature is to experement :-) so I like to experement on most
everything.
Royce

The key is ducted fans become more efficient than a prop at over 450 MPH.
If you have enough HP (1000 HP) to go 450 MPH than a ducted fan should be looked
at. Once you get that much HP the take off performance becomes a moot(s?)
issue.

Paul Lamar

High speed ducts and low speed ducts have different shapes.  The high
speed ducts actually slow the air down before it reaches the fan.
They would have terrible low speed performance with low HP like
mine, but work for the huge HP you mention.

The low speed ducts like I have increase the airspeed in front of the fan
to increase mass flow.

I have no doubt your inflatable lip idea would work, it's just too
complex to pursue at the moment.
--
Perry Mick
Duckt N7XR
http://www.ductedfan.com

The story of my life :-)

Paul Lamar

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