Originally Posted by Ex-Calif
The error in science is not to be incorrect. The error is to assume correctness and ignore significant variables and valid theories that don't fit the original hypothesis.
The hypothesis I was working with at the time was because of a challenge by a friend who is an engineer
and who worked in the aerospace industry, he is a good friend but was also a STRONG disbeliever.
He was adamant, like many, that ANY prop spinning in the water created more drag than when locked
. That was my hypothesis to beat. ANY PROP SPINNING IN THE WATER CREATES MORE DRAG THAN WHEN LOCKED. It went the other way by a long shot and was not even close.
I AM however a believer that at some pitch
their could be a cross over or at least no discernible difference as I have noted less variability in drag numbers the lower the pitch
goes but still more drag when locked. Most sailboats however have rather high pitches and mostly seem to be some where between 8 & 12+ pitch because many are limited on diamter. I have tested an 8 and 12p three blade and a 12p two blade and all still create more drag locked. I'd be very curious to test a lower pitch, perhaps say a 4 pitch. If anyone cares to send me one, in 1" shaft diameter, I would be glad to throw it on the jig.
Over many months I sent him the MIT study, the Strathclyde paper and then did my own design and test. He sent back lots of equations and theories regarding wall vortexes of the tank etc. etc. as to why MIT said what they said, same for Strathclyde. I then built a rather crude jig:
and sent him photos. He surprisingly agreed that the jig was a fair test and the methodology was satisfactory to prove HIS theory. When I sent him the video and he even accused me of faking it.
I then had him come with me in the dinghy
and he saw it with his own eyes. He was left speechless and it was pure entertainment.
After months of theories and mathematical equations back and forth via email
he was left with jaw on the floor. We even tested a two blader that day and had the same result less drag spinning.
All I know is from what I have physically tested myself. My testing surely makes me question the hard and fast "rule" that a locked prop sails
faster. My boats with three blade props had never accelerated when locked and almost always accelerated when unlocked. All those years I thought I was just nuts, may still be..
Still not sold on the whirly gigs, eddy's and vortexes on my rudder
overcoming a 26 pound drag deficit but keep writing and I'll keep reading..
Perhaps I will have to bust out my digital strain gauge and have my buddy tow my boat through the water. I think I actually have enough cable to reach the helm
from the load cell but I still need the data capturing software
to really measure it well..
If anyone has a good scale/load cell software
program they want to send me please let me know via PM. A digital read out for this type of experiment
is only good when exported to a Excel but I don't have an analog load cell only digital..