ORIGINAL: rhall999
See my comments above in red. I hate to be rude Major, but it seems to me as though you are grasping at straws now, trying desperately to cling to your theory[img][/img] Just kidding, I know how hard it can be to accept things sometimes when your brain is certain of something else, I can be pretty stubborn myself sometimes!!!!!!
Well, you see, I've been an aero engineer for 35 years now, and I've been looking for an answer to this particular question for 25 of those. I'm not grasping at any straws. Simple facts
1. slipstream spiral was not mentioned in any of the aerodynamics texts in the FAA library in OKC (about 30 aerodyanamics books) until after the publishing of "Stick and Rudder"
2. It is the ONE and ONLY one aerodynamic property that is not quantified ANYWHERE! The ONLY mention of an acutal measurment of the supposed effect is mentioned in ONE NACA wind tunnel report. AND THAT report is an imperical statment that the fin needed 3 degrees of offset. Again no math to support it, just what it took to make the model have zero yaw. Which they arbitrarily attributed to slipstream spiral.
3. as posted by pimmnz above, there just isn't any photo graphic proof of it either.
Everyone who believes in it states it because that was what was told to them. The ultimate irony of this belief was found in the intro to one of the aerodynamics books menttioned above says to the effect; Question everything; until YOU are satisfied with the answer! Then he goes on, in a VERY deep mathematical analysis book to just state the spiral slipstream exists.
As for the boat prop video, sorry but due to the quality and brevity of the video I just don't see any spiral