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Ducted fan


coggie49
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Me and my flying partner were talking the other day about ducted fans and air straightners, has anybody tried that on a paramotor?

if so did it work or was it a waste of time, and would air straightners stop any of the torque effect, and lastly would it add to much weight?

Dave

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General consensus on ducted fans is that the air velocities that we are dealing with on paramotors would not produce significant advantage in a ducted fan. Also, in order to work to best effect, a duct must run a very close fit to the fan, a situation that many of us have found to our cost, is not well mixed with firm arrivals and dodgy departures. In order to produce a rigid enough structure to deal with this, the weight penalty would be quite high.

Air straighteners would only reduce torque effect I should think, if they actually went so far as to produce a twisting airflow, contra rotating to the direction of engine torque. I would hazard a guess that this would not be a very efficient use of the limited thrust that we have at our disposal.

Just my two drachmas worth.

As a matter of interest, is there anyone on the forum that runs something like a PAP with a gearbox re-drive, that could say whether they experience low levels of torque due to the prop rotating counter to the engine?

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A pretwisted rudder is how paraski went about torque cancellation:

ul8.jpg

paraskistarflex.jpg

Can't find a decent rudder photo, sorry.

With the added benefit that prop airflow can be redirected via handlebars/rudder for a vectored thrust turn.

Easy to accommodate with the higher loading of a paraski and yes does it ever work well.

Also makes crosswind landings very very easy (ok so do wheels, but they have to be pointed in the right direction).

Less safe with just legs/motor/prop lest ye be twisted.

Lifting a knee on to weightshift on the other hand on a paraski is only helpful if you're farting.

fwiw...

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As a matter of interest, is there anyone on the forum that runs something like a PAP with a gearbox re-drive, that could say whether they experience low levels of torque due to the prop rotating counter to the engine?

It is hard to tell how much of the torque reduction is due to the contra-rotating prop and how much is due to the off mid line attachment of the wing onto the swing arms. In flight, torque reaction is hardly noticeable. On the ground, if you open the throttle wide, you can feel a slight rotation of the motor on your back. Nothing overpowering, but still noticeable.

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