Thread: Prop-pitch
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Old 10-07-2008, 12:19 AM   #10
Marin
Scraping Paint
 
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Join Date: Oct 2007
Posts: 13,745
RE: Prop-pitch

Quote:
nomadwilly wrote:

Willard over proped the 30 footers 250 rpm .. quite a bit. Marin says GB did it too .. sinfull I say.*
This is a bit apples and oranges, but we "overprop" the planes we fly on every flight.* For maximum horsepower at takeoff we put the prop in fine pitch to generate the maximum rpm for maximum hp.* In cruise we back the pitch off (increase it) a lot for lower rpm, maximum cruise speed, and reduced throttle setting.* If we tried to take off (in the plane I fly) with the prop set for cruise, at full throttle we'd blow all the cylinder heads off.

Slightly overpropping a trawler-type boat can be more efficient IF the boat is going to be run at lower power settings.* Which is why most of the trawler manufacturers do this, or at least did this when the engines going into their boats were fairly slow-turning, non-turbocharged engines.

And no, I don't thing engines get weaker with age.* They wear out with age, but they are physically as strong as the metallurgy and design they were originally built with.

*
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