Quote:
Originally Posted by brak
so the bottom line - 25lbs of pull saved by freewheeling?
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No not necessarily. On this jig it related to 25 pounds and this jig showed roughly a 50% difference. Due to the angle of the rope and some other factors it is tough to calculate an accurate drag number.
I also load tested the jig alone, without a prop, at WOT and it had about 12+/- pounds of drag so you would need to subtract the 12 pounds from the 25 or 50 pound numbers to even get close. I think it is safer to say something like "nearly double" the drag difference rather than apply a number in pounds. I leave the .001's up to MIT...
Actually now that you brought this up I just double checked the MIT study again they show the Michigan 3 blade at about 13 pounds of drag at 3.5 knots which is the max speed I could get out of it. If you subtract the 12 pounds of test jig drag from the 25 pounds measured on the scale you are within a pound or two of the MIT study..
Pretty close an not bad for a back yard hack who did not go to MIT...
