Design > Engineering board
Effect of Propeller Rake...
John Leidle:
Recently I was informed by someone that in a prop driven boat rake will determine the angle at which the boat travels forward... meaning more or less rake will raise the nose or raise the transom. Is there any of the same effect in an airplane & does it affect toy plane like what we fly?
john
Howard Rush:
No.
Steve Helmick:
While Howard's answer is interesting VD~ I wonder if the data presented LL~ has been thoroughly tested?
Some basic tests could be done with one of John's planes that uses APC props, to see what happens. Use hot water to sweep the blades aft about 10 degrees. Pay close attention to tracking, and pitch, of course.
From what I know about boat props (bass boats, in the 60-75 mph range), I think it would definitely do something, and my guess it would be BAD! Maybe even VERY BAD! Report on your tests, John... y1 Steve
phil c:
Raking the prop blades can make a major impact on the noise. Look way back to the first APC props. They were designed to be quieter and had the blades raked 5-6 deg. The problem was that with more than a couple degrees(what they currently use) the blades were very subject to bending and fatigue failure. Even on sport planes after a dozen or so flights the blades would be showing chordwise cracks in the plastic. I tried some on combat planes. After 3 flights you could just snap the blade tip off with a light twist. Never had one break in flight though. APC uses good plastic and reinforcement.
John Leidle:
Good idea Steve,, the boats I'm refering to are the piston powered Unlimeted hydroplanes speeds upwards of 135MPH I know they are capable of going faster but these guys dont want to bust them up going 150 mph. I just might try a test or 2.
John
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