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  #11  
Old 01-25-2019, 11:08 PM
paul330 paul330 is offline
 
Join Date: Feb 2007
Location: Mpumalanga, South Africa
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Quote:
Originally Posted by BobTurner View Post
Actually, if you start out close to the forward cg limit, burning fuel moves the cg more forward. With the 10 you must always check cg at the expected landing configuration.
You're right, of course, at very forward CofG. I'd just never operated in those regimes - things like my mobile tool kit, tie-downs etc in the baggage compartment have always meant that my CofG is aft of the fuel datum so the CofG moves back as it is burnt. With rear seat passengers, the aft movement as fuel is burnt can become critical and the zero-fuel situation can be limiting.
The good news is that the fuel datum is close to the forward limit so it doesn't move forward much in the forward CofG situation - and it can always be solved with a bit of ballast (or tie-down kits ) in the baggage hold.

Apologies for the error.....
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  #12  
Old 01-31-2019, 09:14 AM
Kellym Kellym is offline
 
Join Date: Aug 2005
Posts: 94
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Originally Posted by F1Boss View Post
About 75lbs for the 3 blade; about 62lbs for the two blade (same as the MT 3 blade).

Make sure the prop is designed for the RV-10. Other props won’t be set up for that airframe.
The 3 blade MT prop is much lighter than the Hartzell 2 blade.
Vans shows it at 43 lbs. It is a very nice prop except for the lower cowling removal.
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  #13  
Old 01-31-2019, 03:43 PM
walker172 walker172 is offline
 
Join Date: Aug 2018
Location: Cold Lake, AB Canada
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Absolutely. I just happened to get a Hartzell 3 blade aluminum prop with my engine when I bought it. That was the reason for my post.
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  #14  
Old 01-31-2019, 06:01 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
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Quote:
Originally Posted by paul330 View Post

As for the 3 blade argument, a "few" knots slow in the cruise is, I think a myth put around by the 2-blade fraternity I was air-racing last year following a 2-blade -10 for about an hour. We tried everything to overtake him but we were just too well matched. In the end, he JUST crept away from us - maybe 1/2kt...........
I think that what is fair to say is that plane to plane variations, resulting in different speeds, will usually hide the speed difference attained by different propellers on different airframes. The (few) tests I know about - where different props were put on the same airframe - always showed the 3 blade as a bit slower in cruise, compared to a 2 blade.
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  #15  
Old 02-01-2019, 07:01 AM
Kellym Kellym is offline
 
Join Date: Aug 2005
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Quote:
Originally Posted by BobTurner View Post
I think that what is fair to say is that plane to plane variations, resulting in different speeds, will usually hide the speed difference attained by different propellers on different airframes. The (few) tests I know about - where different props were put on the same airframe - always showed the 3 blade as a bit slower in cruise, compared to a 2 blade.
Bob is correct. The amount of loss varies by actual prop model and airframe.
Mooney, being obsessed with marketing speed numbers, tested a lot of props, and for awhile offered their Ovation with a 2 blade prop on IO-550 engine. Later, they decided the speed penalty of perhaps 3 kts was worth the shorter takeoff run and better climb with the 3 blade. The speed loss is more noticeable on lower powered engines with older design props. The choice on six-cylinder engines is mostly personal preferences. Aluminum 3 bladed props are not recommended on 4 cyl engines because it is difficult to achieve acceptable balance, and blade spacing will never match up with 4 cyl firing sequence. Composite blades are better at absorbing that vibration and may be okay on 4 cyl. engines.
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