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12-06-2011 06:29 PM

TBrum

Re: Loud Props!!! or quiet props

Love It!!!

And a Pitts!!! Too bad they can't rip props

Awesome Vid

12-06-2011 03:27 PM

bradleyban

Re: Loud Props!!! or quiet props

Must be a valley thing ripping the prop..........LOL

You Tube

12-02-2011 10:58 PM

bradleyban

Re: Loud Props!!! or quiet props

Ohh I just got a raging semi! ..... LOL

Thats the sweetest sound ever!!!!!!!!!!!

12-02-2011 07:00 PM

fsone

Re: Loud Props!!! or quiet props

Nice piece of flying.Great vid!!!!!!!!!

12-02-2011 04:27 PM

Bdegan

Re: Loud Props!!! or quiet props

OOOOOOHHHHHHH..... thats Awesome

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12-02-2011 04:11 PM

Mike Anderson

Re: Loud Props!!! or quiet props

One reason why ripping props should be part of scale aerobatics . . . . . . Not really a good reason, but one reason.....

+ YouTube Video

11-20-2011 02:30 PM

wingburner

Re: Loud Props!!! or quiet props

Some good reading...Thanks for the info Mike.

11-20-2011 01:08 PM

Mike Anderson

Re: Loud Props!!! or quiet props

FYI: I've been involved in a similar discussion here:
https://www.rccanada.ca/rccforum/showthread.php?t=102759

Check out my contributions for references to noise calculators, articles, tables etc. plus my pet theories.

I've seen articles on the net that suggest that optimal performance comes when tip speeds are in the 0.85 to 0.9 Mach range. They all deal with full size aircraft. But others that clearly say that is too noisy at sea level and typical ground temperatures.
I found this calculator that follows this max performance (ignore noise) principle here:

http://www.pponk.com/HTML%20PAGES/propcalc.html

And I found another article supporting the low noise approach to prop sizing here:
http://www.angelfire.com/wizard2/qui...llor_noise.htm

Best all-around prop performance calculator:
http://prme.nl/home/prop-power.xls

11-20-2011 12:02 PM

wingburner

Re: Loud Props!!! or quiet props

Quote:

Originally Posted by Mike Anderson

How to make your prop rip.

It's all about tip speed, which is all about RPM. Any tip over 0.6 Mach (sea level) will rip. Exceed any of these dia/rpm combos and you'll be ripping (2 bladed props)

Dia Rip RPM
16 9,580
17 9,016
18 8,515
19 8,067
20 7,664
21 7,299
22 6,967
23 6,664
24 6,387
25 6,131
26 5,895
27 5,677
28 5,474
29 5,285
30 5,109
31 4,944
32 4,790
33 4,645
34 4,508
35 4,379
36 4,258

Thanks for the chart...Totally agree, prop tip speed creates the noise.

Anybody know why some are louder than others when spinning approxiamtely the same rpm?

Is it tip shape, blade shape, blade material etc.?

One more thing, I've read/been told that any rpm over where the prop starts to rip does not help in performance...anyone have any insight into this allegation?

11-20-2011 11:48 AM

Mike Anderson

Re: Loud Props!!! or quiet props

Quote:

Originally Posted by Bdegan

Mike,Is it possible to add a couple more measurements ?
33
34
35
36

Done - added to my original post above.

here's the formula:
Rip RPM = (TipMachLimit x 760 x 5280) / (P x PropDia/12 x 60)
where TipMachLimit = 0.6.

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