I plan on using the dle 55ra engine to produce 5hp at 8,500 rpm. I am using it in a paramotor, and to save space I am considering using a ducted propeller similar to the Fulcrum power pod. The duct intake would have to be directly behind my back, so I plan to add around 6 inches of space to allow air intake. The engine would be mounted on my back facing into the intake. Effectively, it would be a normal paramotor with a duct around the fan blades. My estimated duct wall clearance is 1 or less mm. I need to produce 15kg of thrust, so how would I design this fan? I considered using a heating duct, which is an 18-16 reducer. This would allow me to get some benefits of the thrust tube and would make it easy to have a front-mounted propeller. Would this propeller work? It is 18x7"

TLDR: Would my combination of propeller, duct and engine produce 30kg of thrust.

Thank you! P.S. Aviation stack exchange sent me here

  • 3
    $\begingroup$ Welcome to Drones SE! Our site explicitly addresses Unmanned Aerial Vehicles, and sometimes unmanned ground vehicles, but never manned vehicles of any kind. I believe this question is still best suited for Aviation SE. Based on the fact that your original post is still open, It appears that it is an acceptable question for the Aviation SE. $\endgroup$
    – Jacob B
    Dec 7, 2022 at 0:09

1 Answer 1


Probably not.

Our usual rule of thumb is that you need 50W per lb. So 5hp (3,750W) would only be good for 75lb. I'm no expert in paragliders, but a quick google indicates that 20-30hp is common.

There some on-line calculators like E-Calc where you can try different motor speeds and propeller sizes to estimate the thrust, although they rely on test results for individual propellers and may well not have accurate data for anything this large.

A smaller prop will be less efficient, and a duct will add weight and drag. A really well designed duct can recover some of the efficiency lost by reducing the prop size, but (in the RC world) it's common for ducted fans to use twice the power for the same performance as a prop.


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