Quantcast

Experimental Ducted Fan Aircraft Designs

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

henryk

Well-Known Member
Joined
Mar 8, 2010
Messages
5,406
Location
krakow,poland
Last edited:

Steve C

Well-Known Member
Joined
Oct 6, 2008
Messages
153
Location
Lodi, CA
There's no magic with counter rotating fans. 20 years ago I made a few of them as well as the late Ralf Dvorak in Germany. We did it for exactly the same reason, which was to make a plane fly with small, scale inlets.

While they did seem to deal with small inlets well, they weigh more and you get resonance problems that are difficult to deal with. In the end i was able to get bettee performance from the small inlet with a single fan rotor and fixed stator.

EDF design went backwards for a while with many trying to make them look like turbofans. Its not that the turbofan design is flawed, but these full scale fans run at much lower rpms than a model size edf. Everybody thought they sounded great, but that turbine like sound is just turbulence in the duct caused mostly by stalled blade roots.

The Vasy fan may have a 45kw rated motor but it wasn't running at that power. Estimating voltage under load, it was closer to 28kw @ 270A.
 
Last edited:

Bille Floyd

Well-Known Member
Joined
Sep 26, 2019
Messages
296
Should have mentioned ; never seen a counter rotating DF
at the field where i fly . There are a lot of guys into EDF
in Las Vegas.

Bille
 
Last edited:

Steve C

Well-Known Member
Joined
Oct 6, 2008
Messages
153
Location
Lodi, CA
There aren't any commercially available CR EDFs and very few build their own fan units. I've been told I'm wierd. :)

That Elecroflight plane with CR props seems to have been built only to take to shows and get investors. It's been years and I never heard it flew.
 
Last edited:

Bille Floyd

Well-Known Member
Joined
Sep 26, 2019
Messages
296
There aren't any commercially available CR EDFs and very few build their own fan units. I've been told I'm wierd. :)
...
Do you have any data, from your work ; would be fun, to look at ?

And your , "Not Wierd" , (some people enjoy tinkering with the, What-If) .
For every attempt, there may be 2 failures at trying to improve something ; but
without people like You sir , technologically speaking , we'd still
be stuck, in the 15'th century.

Bille
 
Last edited:

Steve C

Well-Known Member
Joined
Oct 6, 2008
Messages
153
Location
Lodi, CA
Sorry, I was never big on static testing. As soon as I had a new fan built, I always wanted to fly it right away. In those days, electric power was pretty weak, so it was easy to see a difference.

With a small inlet duct, you might not learn much static anyway. I have a BD-5 model with naca ducts. It has horrible static thrust, but once it gets airborne you can hear a change in the sound and it really moves after that.

What I learned with the tandem fan was to use more blades. Fans with big gaps between the blades need large inlets. Large inlets are draggy.

These days I've been using a 3d printer to experiment with fans. It allows me to try more things without spending all the time with molds or laminated wood like my early ones. Last year I attempted to come up with something half way between a centrifugal and axial fan. I flew one of the 5 or 6 I printed, but it wasn't as good as an axial flow fan. It just didn't move enough air, even though velocity seemed pretty good.

It has always been my desire to build a df unit for a full scale homebuilt. I have a single seater drawn up and some of the fan calcs done.
 

Bille Floyd

Well-Known Member
Joined
Sep 26, 2019
Messages
296
...

It has always been my desire to build a df unit for a full scale homebuilt. I have a single seater drawn up and some of the fan calcs done.
Please do Not let anyone, or anything ; ever stop you from endeavoring, to fulfill
your ideas, or dreams !!!

Bille
 
Top