If I put a new fan in my EDF, which has 5 blades, and I go up to six, will I notice any performance increase, all things being equal as to motor and esc?

Depends on the pitch and blade area.....too much load will be bad

anyway , if "all things are equal" , they will be the same...Hehe

Your friend , down under

Originally Posted by SON OF PALEFACE

Depends on the pitch and blade area.....too much load will be bad

anyway , if "all things are equal" , they will be the same...Hehe

Your friend , down under

Exactly so

Ok. I was wondering about that. A while back I seem to remember someone doing an article on a ducted fan plane and the fan had six blades. They claimed that by taking off every other blade and turning it into a 3 blade fan that there was a big performance boost. It's been so long ago that I don't remember the plane that was reviewed.
My own experience with propeller planes has been that I got more speed from 2 blades vs 3 but I wasn't sure about how that worked with EDFs.
Thanx.

We used to do that with Wattage Powerfans. Fewer blades draw less current (subject to pitch), and can be spun at higher RPM. (Meaning you can use higher voltage).

It's just Ohm's Law - If you want to use more voltage to produce a given power level (watts), you can use less current to get there.

You want to avoid bogging a motor down by drawing too much current (making it work too hard).

A rough analog is trying to start a car off in third gear.

Full scale planes vary the pitch in flight - Coarse (high) pitch gives "torque-y" power at low speed, for taking off, climbing, etc. Then when you're at altitude, you flatten out the pitch, and maximize dynamic thrust.

Bottom line: put it on the meter and see what your motor/battery/fan combo draws.

Originally Posted by randall1959

Ok. I was wondering about that. A while back I seem to remember someone doing an article on a ducted fan plane and the fan had six blades. They claimed that by taking off every other blade and turning it into a 3 blade fan that there was a big performance boost. It's been so long ago that I don't remember the plane that was reviewed.
My own experience with propeller planes has been that I got more speed from 2 blades vs 3 but I wasn't sure about how that worked with EDFs.
Thanx.

Aaaaah , you have that round the wrong way.........

Quote
"Full scale planes vary the pitch in flight - Coarse (high) pitch gives "torque-y" power at low speed, for taking off, climbing, etc. Then when you're at altitude, you flatten out the pitch, and maximize dynamic thrust."

The air is thinner at altitude and you need more pitch.....max RPM AND fine pitch for take off and climb out

Ian

Originally Posted by SON OF PALEFACE

Aaaaah , you have that round the wrong way.........

Quote
"Full scale planes vary the pitch in flight - Coarse (high) pitch gives "torque-y" power at low speed, for taking off, climbing, etc. Then when you're at altitude, you flatten out the pitch, and maximize dynamic thrust."

The air is thinner at altitude and you need more pitch.....max RPM AND fine pitch for take off and climb out

Ian

correct, you increase pitch as airspeed increases.

An automatic "constant speed" prop will increase pitch as you increase speed durring takeoff.

You can think of it as low pitch = low gear.

For climbing a steep hill a truck will use low gear. for maximum climb performance an airplane uses low pitch.

For maximum efficiency at speed you use high gear (high pitch)

If the speed is excess for the gear and engine rpm the truck will be using the engine as a brake. If airspeed is excess for rpm and pitch the prop acts as a brake.

This analogy never fails.

******************

for the EDFs that worked better by clipping half the blades.. a higher power motor would have been better than the original. When clipping blades out imnproves thrust you started out with too much load on the motor.