ORIGINAL: CGRetired
ORIGINAL: da Rock
ORIGINAL: CGRetired
Just remember what I always say about prop'ing engine is that noise does not equate to power.
CGr.
Actualllllyyyyyy........... since you said it that way................
noise does equate to power
The extra loud noise you hear when the rpms and prop diameter match up usually is some of the power being sluffed off to create the noise. So in a sense, hearing that louder noise means you're wasting some power.
There is another benefit of not making that noise by turning a larger diameter prop slower. The pitch is almost always greater and that usually means you've got a more efficient pitch/diameter. As well as having a more efficient result from the slower rpms. Neither effect is major, but heck, it's fun to talk about, and nobody has any proof if the effects actually are enough to matter. So it's just some more noise..............
What I meant is that many seem to think that when an engine/prop is making a lot of noise, it must be generating a lot of power. This is just not so. It takes the right combination of power (engine) and the right prop to get the desired speed. And, of course, that just won't happen with EVERY airframe. The airframe will only go so fast before it begins to have harsh consequences.
So, in that case, noise does not equate to power. A perfect example was my Tiger 60 that had an OS 61 on board. I proped it, don't recall what prop I used, but I was turning about, oh, 13,500 RPM. It made a lot of noise but wasn't doing much in the air. But, it made lots of noise and it attracted lots of attention. I was better off using a good prop that got the engine in the power range of about 11,500 RPM and without all the tip speed noise.
CGr.
Yeah, I knew what you were saying, and wasn't arguing, just adding the bit about the sound from prop tips. Adding to your already good advice. With a slight bit of a new direction. I shoulda put a few more smiley faces in the post, I reckon. Good thing is that you added more examples that'll be good for beginners to read. That's the idea, after all.