Posted 19 December 2009 - 07:54 PM
I think I may know the reason why Eli is asking the question as I sold him some Revell P-38 props awhile back. The prop profiles are such that it is hard to tell which is the leading edge of the prop and the trailing edge, as molded. This problem also arises with other products which also exhibit symmetry in the molded product and it is difficult to tell the leading from trailing edge. Hence the question, which way is up? Rather than avoid the problem by putting the props at a fully feathered pitch (when using individual blades as is common with resin AM) or 0 degree pitch, a little research into the individual aircraft can go a long way to determine the rotation of the blade.
It can be difficult. The Lightning I sold to the British in WWII did not have counter-rotating props. The F-82 twin Mustang started with counter rotating props going clockwise and then switched to props going counter clockwise. Merlin engined Spit props went one direction, the Griffon engined props went the opposite direction.