EDF How Much Thrust Is Needed?

[Frederik Edvardsen]

Hello. Does anyone know how much thrust is needed for a 2 kg airplane? Is there any optimal thrust to airplane weight ratio? Will two of these EDF's (which in total provides about 1.2 kg thrust) be enough? US$20.99 % HTIRC 50mm 11 Blades Ducted Fan EDF Unit With 3S D2627 4900KV Brushless Motor For RC Airplane  RC Parts from Toys Hobbies and Robot on banggood.com

Thank you.

 

[RandyDSok]

This isn't as straight forward of a question as many new folks may think. The type of airplane it is, type of wing, the actual wing loading, how long ( and type ie grass or paved ) of a runway you have... even temp and humidity come into play when trying to calculate the amount of power you want for a given airplane. Most sport and scale type planes will have a little over a 50% power ratio ( about 0.6 thrust to the weight )... a 3D type will often be a 1:1 ratio or slightly more.

If this is a plane that is built as scale from an actual plane... then look at the amount of thrust the original has for a starting point for your own model.

 

[Tony]

I agree with what Randy posted above. It is completely going to depend on what kind of plane and what kind of surface you are taking off from. Your thrust numbers and the AUW of the aircraft will theoretically make it fly, but it's going to feel heavy on the sticks and dropping a wing (wing stall, bank stall, whatever you want to call it) is going to be a real issue. If you are talking off from grass, you are going to need ore thrust, I can almost assure you. One thing to remember, EDF's are cool and sound awesome, but they are not the best at thrust compared to a prop. You must keep airspeed up to use them.

 

[Frederik Edvardsen]

Thank you for answers. The reason I would like to use EDF's are because they don't get as easily scratched and damaged as propellers do, but I can see it has some downsides unfortunately. I think I'll just go with four engines then, just to be sure?

 

[Tony]

If you have the space, you can do that. Just remember you are going to be adding more weight because you are going to need more battery to run those extra two motors. Something to calculate. Might be worth it, might not. Just depends on the wing loading area and such.

 

[Frederik Edvardsen]

Ugh yeah I know. I believe it will be to heavy to fly with four of those engines. I looked at another type though, which is 64mm instead of 50mm. US$35.71 % FMS 64mm 4S 3S 11 Blades EDF Unit With KV3150 KV3900 Brushless Motor RC Parts from Toys Hobbies and Robot on banggood.com. I don't know, maybe that will create enough thrust, or will it still be hard and heavy to control? I know it depends on a lot of factors, but with an airplane of 2 kg flying in "normal" weather of 15°C or so at ground level, will it be enough? Thank you.

 

[Tony]

IMO, there is really only one way to find out. I have two 64mm EDF's that I have played around with a few times and some experiments work, some don't. Dual EDF's in an FF-22 works absolutely awesome. A single one in an F-16 didn't work worth a darn lol. But if you can fit two 64's, I would definitely suggest them over the 50's for sure. More than likely you are only going to draw a little more power, but you have way more surface area and should have more static thrust. I would give it a go if it was me, but I"m kind of crazy like that lmao.

 

[Frederik Edvardsen]

Sounds great! I'll go with the 64's then, they weren't much heavier or much more expensive then the 50's, so no problem there. Thank you Tony!
Btw I'll actually save power by going with two 64's instead of four 50's, so no downsides I guess? I'll give it a try.

 

[Tony]

Let us know how it goes. This thread has me wanting to get more into EDF's again lol.