The washer goes on top of the prop ( this will give you better compression as without the washer the nut could dig in on one of the flats before it gets tight enough), then second the prop nut, and last the tapered cone nut if you like.
I use the tapered cone as a locking nut to keep the prop nut from coming off.
You can put them on without the the locking nut if you like or just use the cone nut only many ppl do. I put it on my quads
just for that extra safety factor. The higher end tiger motors like my
MT 4006-13 has the capability
of using the
6MM CCW NUT prop adapter. So the prop trying to spin off would cause the nut to tighten.
But mechanically speaking it is a washer. Therefore it goes between the moving part (the propeller spinner nut/ prop nut) and the stationary part (the propeller).
How you do it is all up to you....
