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  #11  
Old 07-01-2015, 07:57 AM
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greghughespdx greghughespdx is offline
 
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Also note that Whirl Wind will build a 200RV prop with counterweights if you ask them to. They don't advertise it per se, but they have told me they'll do it if I ask for it. Same applies to the 74RV. Costs and weighs a little more, of course. Calling and speaking with them is time well-spent.
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  #12  
Old 07-01-2015, 10:08 AM
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donaziza donaziza is offline
 
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I've got a Whirlwind CS on my 8. Called the company. They said Gentlemen's acro was fine. Do them all the time including the cuban 8's. No problems.
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  #13  
Old 07-01-2015, 10:41 AM
luddite42 luddite42 is offline
 
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In addition to oil pressure loss issues, aerobatic props are also designed to withstand snap roll and tumble maneuvers which put high gyroscopic stress on the blades and hub. If you're not doing those or any maneuvering that causes significant, extended oil pressure loss, there is nothing to worry about with a non-acro prop. Virtually all RVs see nothing but simple positive G loops and rolls. Like Smokey says, pull the throttle back if you happen to hear a surge.
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  #14  
Old 07-01-2015, 11:04 AM
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ronschreck ronschreck is offline
 
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Quote:
Originally Posted by luddite42 View Post
In addition to oil pressure loss issues, aerobatic props are also designed to withstand snap roll and tumble maneuvers which put high gyroscopic stress on the blades and hub. If you're not doing those or any maneuvering that causes significant, extended oil pressure loss, there is nothing to worry about with a non-acro prop. Virtually all RVs see nothing but simple positive G loops and rolls. Like Smokey says, pull the throttle back if you happen to hear a surge.

I wouldn't even worry about high gyroscopic stress on any composite prop. The blades are very light, compared to metal blades of the same size and the hubs are generally the same for metal and composite blades. Now, having said that, I recall that Whirlwind has taken some metal off of their hubs and this is possible because of the smaller loads imposed by lighter blades. Never heard of a hub failure due to aerobatics. Anyone?
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  #15  
Old 07-01-2015, 11:32 AM
luddite42 luddite42 is offline
 
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Quote:
Originally Posted by ronschreck View Post
I wouldn't even worry about high gyroscopic stress on any composite prop. The blades are very light, compared to metal blades of the same size and the hubs are generally the same for metal and composite blades. Now, having said that, I recall that Whirlwind has taken some metal off of their hubs and this is possible because of the smaller loads imposed by lighter blades. Never heard of a hub failure due to aerobatics. Anyone?
In the past 10 years I know of around seven Whirlwind acro prop failures - 150/151 and 200C. Thrown counterweights, thrown blades. Not sure the failure mode of all of them. All were flown beyond "gentlemen's acro". Not sure if the actual hub failed, but Hartzell has had aerobatic hub cracking in the past with metal blades. Fixed now. None of this should concern anyone here.
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  #16  
Old 07-01-2015, 01:01 PM
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RV7Guy RV7Guy is offline
 
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Location: Chandler, AZ
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Default They're fine

Flew my 7 over 800 hours and did lots of aerobatics. No issues at all. Most all positive but would occasionally pause inverted during a 4 or 8 point roll.

The failures were the early 151's and 200C's. Some being pushed pretty hard. The new blade, according to WW, is for 200 hp or more. No advantage over the 200RV if used on lower HP engine. The only thing lower will be your wallet
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  #17  
Old 07-01-2015, 02:30 PM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
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Default Props

Quote:
Originally Posted by luddite42 View Post
In the past 10 years I know of around seven Whirlwind acro prop failures - 150/151 and 200C. Thrown counterweights, thrown blades. Not sure the failure mode of all of them. All were flown beyond "gentlemen's acro". Not sure if the actual hub failed, but Hartzell has had aerobatic hub cracking in the past with metal blades. Fixed now. None of this should concern anyone here.
How many failures over the years on MT's??? I would venture far more than Whirlwind. I had a failure years ago on a three blade MT that was not reported.
The early Hoffman aerobatic constant speeds failed to flat pitch with loss of governor pressure.
If installed in EAB, 4000 r/m does not mean the engine is trashed. The parallel valve 360's have thousands of hours of operation in the 35-3600 r/m range. They will likely tolerate one overspeed to 4000 r/m. The angle valve engines are not quite as tolerant of high r/m but still survive in the 3500 r/m range. The Red Devils/Christen Eagles Airshow Team used fixed pitch props because they wanted to make noise. 25 years operating in the 3500 r/m range. Hilliard's Pitts was always angle valve 360. I can pretty well tell what the r/m is on a 75" diameter prop just by the sound. They start to make a lot of noise above 3000 r/m and a LOT of noise at 3500 r/m.
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  #18  
Old 07-01-2015, 06:41 PM
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izzybear izzybear is offline
 
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Location: Dallas, TX
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Default Thanks for your input!

Thanks everyone for your input - I really appreciate it. I now have a better understanding of the advantages and disadvantages of the non-aerobatic prop and specifically, the 200RV. Thanks also for the extra ideas as I move - more confidently in the direction of my decision.
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  #19  
Old 07-01-2015, 08:06 PM
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Default It'll do great

I have inverted fuel and oil and a dual seat-belt with ratchet in my -8. The 200RV does great during aerobatics.

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  #20  
Old 07-02-2015, 07:29 PM
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osxuser osxuser is offline
 
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Quote:
Originally Posted by jrs14855 View Post
How many failures over the years on MT's??? I would venture far more than Whirlwind. I had a failure years ago on a three blade MT that was not reported.
The early Hoffman aerobatic constant speeds failed to flat pitch with loss of governor pressure.
If installed in EAB, 4000 r/m does not mean the engine is trashed. The parallel valve 360's have thousands of hours of operation in the 35-3600 r/m range. They will likely tolerate one overspeed to 4000 r/m. The angle valve engines are not quite as tolerant of high r/m but still survive in the 3500 r/m range. The Red Devils/Christen Eagles Airshow Team used fixed pitch props because they wanted to make noise. 25 years operating in the 3500 r/m range. Hilliard's Pitts was always angle valve 360. I can pretty well tell what the r/m is on a 75" diameter prop just by the sound. They start to make a lot of noise above 3000 r/m and a LOT of noise at 3500 r/m.
I'm going to venture a guess that those thousands of hours have overhauls between them. The aero engines I used above 3500rpm rarely had more than 50 hours on them between disassembly and inspection. Same with the props, a 4000 rpm rapid acceleration will most likely stretch the connecting rods beyond limits. This kind of event is very different from a fixed pitch prop turning at 3500 RPM. Robinson helicopters has experience with a lot of these in botched starts with the throttle opened too far.

My favorite event was Reno with the TIO-540 that went flat pitch/closed wastegate all at the same time. That was in excess of 8000rpm before the engine seized. The Hartzell retained all 3 aluminum blades, but both the prop and engine were really trash. Stretched the prop mounting studs 1/8" or so if I remember correctly.
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