Folding Contra props for Adverrun and Brenner
 

What is the benefit of a folding prop vs. stationary prop?

Just spoke to an F3a friend in Japan and he says it's the obviously to get some security against extensive damage from a rough landing. He says they are looking at the same products there. While he's not certain of the reversed diameter stagger, he sees some possible benefits in flight trimming but it may just be due to the folding feature.

Interesting.

The smaller diameter rear prop is to keep the tips of the rear prop out of the tip vortices of the front prop. The folding aspect.....it is a "buffer" per se. Flexing of the prop discs reduces the peak gyroscopic load on the props during pitching / yawing. The gyroscopics can steer a plane left/right in pitch or up/down in yaw and is most noticeable on a single prop system, and least noticeable in a true torque sharing Contra (Brenner V3, V4, or RS).

I presume the hinge limits the amount of movement so the front and rear props can not cross paths?

I had ordered these props for my V4 Brenner Contra unit to try, but just before they were shipped I received and email that these will not fit the Brenner Contra units. So i was issued a refund. So to my understanding they are strictly for the Adverrun system unfortunately.