Tri Plane decalage ; best settings?
 

I have found that on bipes (I have built and flown at least 2 dozen different ones) that they fly best with the upper wing set at about 1.5 to 2 degrees less angle of attack than the lower wing has. Does any one have any practical experience with tri-planes as to best relative settings for the three wings?

RE: Tri Plane decalage ; best settings?
 

The upper wing on an equal-winged bipe usually develops more lift then the lower wing, and, according to theory, induced drag should be minimized by having the wings develop equal lift, by giving the upper wing lesser incidence.

However, full-scale wind tunnel tests conducted on biplanes many years ago revealed that induced drag was very slightly reduced by giving the upper wing something like 1-1/2 degree more incidence than the lower one, contradicting theory

I find that my own design aerobatic bipes seem to exhibit better line-holding on vertical uplines and downlines with about a half to one degree less incidence on the upper wing - in other words, negative decalage. I have never flown an RC tripe, but would be inclined to give the top wing about the same incidence as the other two, or maybe a degree or so less, and would be prepared to experiment a bit with still lower incidence for the top wing to see how it affects handling.