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11-12-2008, 02:49 PM
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moderator
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Join Date: Dec 2004
Location: Mill Creek, WA
Posts: 617
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Quote:
Originally Posted by erich weaver
My understanding from WW is that the "avoid" statement is CYA type thing. It is not based on any testing specific to the WW prop - they adopted the statement based on testing Hartzell did on their props. I question whether that is really applicable at all, but Im no expert
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My understanding as well.
__________________
Randy Lervold
RV-12iS, empennage/tailcone complete, wings currently, fuse in box
RV-3B, first flight 2007 - sold
RV-8, first flight 2001 - sold
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11-12-2008, 03:57 PM
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Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,574
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"RECOMMENDED"
Hi All,
I just heard back from Greg Anderson, and he clarified that the manual says 'recommended to avoid', I think for the reasons stated above.
I think there is no issue.
The resonance problem is from a particular propeller being sensitive to a certain resonant frequency. the engine is always putting out two bumps per rev, so 2300 x 2/60 = 75 hz, for example. If the prop blade has a resonance at 75 hz, it needs a restriction. its not the engine's fault.
Typically, a composite blade is lighter and stiffer, so its frequencies are all higher - with no test data its hard to say, but very likely that there are no resonance issues in the operating range. So I think the 'recommend' is based on the observation that certain rpms have been hard on SOME props, so just be careful.
I'm content
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 625
LS6-15/18W sailplane SOLD
bought my old LS6-A back!! 
VAF donation Jan 2020
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11-12-2008, 04:36 PM
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moderator
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Join Date: Dec 2004
Location: Mill Creek, WA
Posts: 617
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Not only are composite props lighter and stiffer, but they are inherently more damp than almost any metal. When was the last time you saw a fiberglass tuning fork?
Every object that has any mass has a resonant frequency, but the properties of the material determine the amplitude of the resonance -- composites just don't exhibit as much gain at their resonance frequency as aluminum.
__________________
Randy Lervold
RV-12iS, empennage/tailcone complete, wings currently, fuse in box
RV-3B, first flight 2007 - sold
RV-8, first flight 2001 - sold
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11-13-2008, 08:56 PM
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Join Date: Jan 2005
Location: Chandler, AZ
Posts: 2,904
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No real issues @ any RPM
I think I was one of the early purchasers of the 200RV. (Got it when it was still in CA.) When I began flying the prop I tested it at 50 RPM intervals from 1800 to 2650. I could find no real problems at any RPM range. I do avoid the recommended rpm's but have no problem with flying there for transient time periods.
I might add that it is really important to get the prop balanced. I did and it was balanced to a 0.00. This is a perfect balance. The guy said he has never had one before. It is smooth beyond works.
Finally, I've found that the "sweet spot" for my engine/prop combination is 2450 RPM at WOT. Supersmooth, fast and efficient.
Use with confidence.
__________________
Darwin N. Barrie
Chandler AZ
www.JDair.com
RV-7 N717EE-Flying (Sold)
RV-7 N717AZ Flying, in paint
EMS Bell 407,
Eurocopter 350 A-Star Driver
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11-13-2008, 09:06 PM
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Join Date: Feb 2006
Location: Baltimore, MD
Posts: 1,039
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Quote:
Originally Posted by RV7Guy
I might add that it is really important to get the prop balanced. I did and it was balanced to a 0.00. This is a perfect balance. The guy said he has never had one before. It is smooth beyond works.
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In my 200RV owner's manual (Rev2003-1) it states "The engine/propeller must be dynamically balanced before first flight."
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11-14-2008, 06:47 AM
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Join Date: May 2005
Location: Eagle, CO
Posts: 84
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Dynamic Balancing
Quote:
Originally Posted by nucleus
I've been meaning to mention this... Interesting isn't it? There ARE RPM restrictions on a 200RV prop. They need to either change the website or the manual...
Also, it says in the same manual that you should dynamically balance the prop before you fly it, has everyone seen that?
Hans
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I had my WW dynamically balanced based upon the POH statement. The initial test showed a .05 inch deflection. This is exceptionally good, consequently no additional balancing was necessary. The WW is a very smooth prop. I have over 400 hours on mine and am quite happy with both the prop and the support.
__________________
Rick McBride
Eagle, CO
RV-6 Built and Sold
RV-8 Built and Flying
RV-10 Under Construction
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11-24-2008, 12:04 PM
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Join Date: Jan 2008
Location: Cupertino, CA
Posts: 78
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Update soon on 200RV service interval & harmonics
I understand from talking to one rep that a whole lot of additional testing has been completed and they will hopefully soon announce a major extention to the initial service interval (may be as high as 2000 hours and 7 years).
Also, as Steve posted, the harmonics should be way higher and indeed they are. The primary resonance is at 340hz and they expect to take off any RPM restrictions as previous RPM concerns were not really based on test data.
This is all prelim, I'll look forward to the actual announcements!
Tim
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