I'm going to take my duct off soon, to re-finish it.
I'm thinking about trying to fly it without the duct, I'm concerned

about

take-off distance, climb-rate, and cooling. I'll make some

high-speed

taxi

runs first, to see how it feels.

Perry

Good idea Perry. I forgot how we measured the acceleration the last

time.

Use a stop watch and see how long it currently takes you to get to
50 MPH. Also with the duct off see what the static RPM is.

Paul Lamar

Vance W Jaqua wrote:

Good for you Perry! I will go out on a limb and predict that the take

off

run will be a bit longer but do able, and the inflight perfomance will
be measurably better. If you have not checkd my web page on prop
design, you will find some curves that give relative perf at various
disc loading based on momentum laws which set the 100percent
limits, and above 150 mph the loss due to small props is not great
Vance

When you look at that dinky 38" prop on the back of a Long-EZ with the
duct removed, you think "that couldn't possibly work"!

Perry

I ran a 38 in dia prop in my prop model, and the pedicted output seems to
say that it is far from hopeless, If you can drive your static rpm up to
the equiv of about 130 bhp you should have in the range about 300lbf
thrust, and I think you are entitled to at least 180mph where the
little prop should be about 70 percent eff. As I recall the direct
drive Suber exceeds these numbers - Take data, as Paul says.
and keep us informed - Vance

 
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