EDF Torque Effect?

[redfenix]

I'm planning on designing a scratch-built model, a VTOL using electric ducted fans. I'll be using two fans for the main lift. My question is: if both of these fans rotate the same direction, will it cause yaw torque in the craft? I realize that DFs are much different than props or heli rotors, less inertia, higher rpms, etc. So, do they exhibit much, if at all torquing? Also, both fans will be in a saddlebag configuration, so they are not centered in the craft. This, I believe would minimize any torque effect.

BTW, I have looked for reverse pitch fans and have had absolutely no luck.

Thanks for any comments or ideas.

--Kevin

[Gary Warner]

If the fans have any torque transferred to the housing and they both turn in the same direction, they will apply a torque force to the airframe, even with your mentioned placement.

The *ideal* fan does not have any torque transferred to the housing mounts/air frame. The EDF50 fans do have some. A fan I designed has zero torque. It all depends on the design and placement of the stator fins (usually integrated as motor mounts).

If the fans you plan to use have any torque, it can be cancelled out with the addition of stator fins in (or on the outer edge of) the exhaust housing. Experiments will be need to select and adjust the fins for zero torque. Also, many fans will have changing torque depending on the power level. This may need to be considered.

Gary
--