RC Plane Electric Ducted Fan Engine Performance

I like the idea of a RC delta wing plane with a screaming jet engine and an EDF certainly delivers on the noise requirement, but what is not clear at all, is how much thrust an EDF can actually deliver. So, today, I made an engine static test stand, that can sit on top of a small electronic scale.

An EDF engine mounted in the open doesn't look very nice on a plane, so I also tried a Starbucks Coffee Cup Conversion, to see what effect that has on performance.

To cut a long story short:

The only way that I could increase thrust, was with a better battery.

For this 12 bladed 70 mm EDF, the manufacturer claims a maximum thrust of 2400 g. However, with a 6S 1500 mAh battery, the maximum measured thrust was 1100 g and with a 3700 mAh battery, it was 1300 g.

Any kind of coffee cup added to the engine exhaust, reduced the static thrust by 10 to 15%. I slit the cup and tried an opening size from 68 to 55 mm with masking tape to hold it all together and keep the cup from flying off and the smaller the nozzle, the less the thrust - Simple as that.

My suggestion for best performance is to mount an EDF on top of the wing with unimpeded air flow. On top of the wing, you will get less grass and sand in the engine during landing. If you want the EDF enclosed for aesthetics, then you need to factor in a thrust reduction of 15% or more.

You need to take the engine manufacturer specification with a (big) grain of salt.

As for how much engine to buy for your plane, if the TOW of the plane is 1000 g, then you should look for an EDF with at least 3000 g rated thrust, so that you can maybe get 1500 g actual thrust, otherwise it may be a struggle to get the plane into the air.

La voila!

Herman

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