I agree that any propwash effect would be exacerbated in a right crosswind landing and mitigated in a left crosswind. If a preponderence of shimmy incidents are occurring in right crosswind landings, there might be something to work on.
However, I think this can be at most only a part of the shimmy issue. It seems that many have had no or very few shimmy incidents (I have had none in spite of a few landings in stiff 90 degree right crosswinds). One explanation could be that some nose wheels pivot more freely than others. Those would be more susceptible to the effect of propwash and crosswinds.
I am leary of the noeswheel being turned to the right theory. If you have flown any aircraft with a self centering nosewheel that doesn’t self center, it is readily apparent that something is amiss.
I’ve flown a 172 for 109 years and in that time I became very familiar to every facet of that plane’s personality. On one flight for a few moments after take-off, the plane would not fly in an attitude in which the turn coordinator and my body agreed was coordinated. This happened for a few flights, but always seemed to fix itself.
Well it turned out that when I used the rudder I caused the nose gear to center and the problem went away until the next take-off. Since I would usually use the rudder in the crosswind turn, the ‘problem’ would go away very shortly after take-off.
A quick trip to the A&P and the problem was fixed. But the point of this story is that if the nose gear on the Cirrus is flying noticeably out of alignment with the centerline of the aircraft, I would imagine it would be very noticeable.
As additional arguments against the turned nosewheel theory, the nose gear is mostly below the prop (unless it really is tilted up), and therefore, below the propwash, which that close to the prop shouldn’t diverge significantly. I think it would be only marginally (at most) affected by the propwash. Furthermore, using some high school physics (sorry Roger, here goes my “A”), if the Cirrus is traveling between around 130 to 135 KIAS (it is indicated which counts here, isn’t it?), then what would the crosswind vector have to be to produce a turn that noticeable? Since the aircraft is almost never flying in a crosswind, the answer is the crosswind component is almost “0” and the only influencing factor is the propellor/propwash, which I believe to be minimal.
Mike, my memory is good, but not that good! Heck, I can’t even remember the name of the airport that you were landing at, let alone which way the crosswind was!!
While trying to find something else in the Training Manual, I stumbled across the comment that the nosewheel might feather into a crosswind on landing (page 33 of the SR22 Manual). The airspeed should be roughly similar to the takeoff speed when you observed the problem in the 172. Clearly, Cirrus and Wings Aloft believe that a side slip on a cross wind landing can cause enough pressure for the nosewheel to pivot somewhat but I don’t recall anyone reporting the kind of problem you had in the 172 prior to a nosewheel shimmy. So it seems in a Cirrus the nosewheel can be feathered to one side without effecting the control. It is hard to imagine that a plane with a freecastering nosewheel would be designed any other way.
Today I took off in a clean plane. It was the first warm and buggy day that I have flown since I got the plane. I put the plane back in the hangar and started cleaning off lots of bug splats. When I got to the nose wheel guess where the bugs were? On the right side. None on the left. So at least on my SR22 the propwash does hit the right side of the nose wheel. Incidentally this pattern of bugs on the right side of the nosewheel was much more pronounced than on my C182.
I don’t know if all this is worth any more than the smashed bugs. However, I do think it is worth checking out Mikes’s theory that propwash might cause more nosewheel deflection (and more shimmy incidents) in right crosswind landings and less in left crosswinds.