14000 RPM? Ooooh kay..

Noise does not equate to power. Turning 14000 RPM means absolutely nothing if it does nothing for performance. You can put a 9-5 on an OS 46 and get 15000 rpm and the only thing you will succeed in doing is destroying that engine.

It has been said so many times here in the Beginners Forum that the RPM numbers quoted by manufacturers mean absolutely nothing to use in actual flight.

Prop these things so that you get good performance. It takes several trys to get the right engine, airframe, prop combination that suites your aircraft. Excessive RPM does nothing but chew up aluminum and internal parts of your engine.

Here is how it works: the prop has two numbers: Diameter and pitch.. 12-8 for instance. This is a 12 Inch diameter with an 8 inch pitch. The pitch number will tell you how far that prop would move in absolutely perfect circumstances, in one revolution. So, a 8 inch prop will move 8 inches per revolution. At 10,000 RPM, this is 80,000 inches per minute. Do the math. That is 6666.666 feet per minute or 111.11 feet per second. 88 feet per second is equal to 60 miles per hour, so 111 feet per second is probably somewhere around 75 miles per hour... in perfect conditions.

Increase the pitch and you will increase the speed, but at the cost of load to the engine, and lower RPM.. thus most likely you won't get better speed out of that prop. It's a big circle.

Keep the RPM of your standard off-the-shelf 40 - 60 size engines below 12,000 and you will be just fine.

CGr.