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08-04-2013, 09:14 PM
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Join Date: Feb 2008
Location: Pensacola, FL
Posts: 374
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Mass balancing engineering question
The ailerons use a steel tube for a mass to balance them. I am directed to cut it to a specific length. But what if someone does not prime inside? What if I heavily prime? Obviously the weight is small, but is must be significant enough to measure I would imagine.
Any active aero engineers that can answer this? I can't find my old text books and those classes...well...they are a bit fuzzy!
I imagine the tiny weight differential would/could be offset by trailing edge geometry. Just curious, not worried!
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RV-? in planning stages.
RV-14 #140050 SOLD
Permanently willing to contribute fuel for RV rides
Helicopter ATP/CFI(I)
ASEL/AMEL Commercial/Inst/CFI(I)
Aerobatic Instruction available
Atlanta based.
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08-04-2013, 09:18 PM
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Join Date: Dec 2008
Location: Los Angeles, CA
Posts: 301
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My take
Although I am by no means an expert compared to others on this site, I believe more mass actually helps with flutter control. The farther in front the aileron's CG is from the center of pressure (of the aileron) the more flutter resistance the surface has. But I will let others correct me.
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John
2016 dues paid since 2008
- High hopes fade on a warm hearth stone,
he travels the fastest who travels alone-Kipling
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08-04-2013, 09:22 PM
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Join Date: Feb 2010
Location: Perth, Western Australia
Posts: 1,647
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Isn't the tube stainless steel?
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rgmwa
RV-12LR 912ULS
120346
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08-04-2013, 10:11 PM
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Join Date: Mar 2009
Location: Sydney, Australia
Posts: 617
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The tube is galvanized iron and does need to be primed internally.
I agree with Johnny's comment about the extra weight in front of the CofG being OK.
Not enough weight where the wright is behind the CofG and the aileron is unbalanced if I recall is very bad.
Cheers
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Eddie Seve
Sydney Australia
First Flight 16th July 2012
RV-7 Phase 2, 30 Oct 2012
1100 hrs Feb 2020
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08-04-2013, 11:41 PM
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Join Date: Nov 2010
Location: Australia
Posts: 53
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The amount of paint on the aileron will probably have more effect on total mass balance than the amount of primer on the inside of the galvanised tube.
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08-05-2013, 12:18 AM
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Join Date: Oct 2006
Location: Melbourne, Australia
Posts: 427
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The idea behind balancing is that any vertical motions/accelerations/forces are applied directly to the centre-of-mass of the control surface so as not to cause any unwanted control deflection
If they balance on their hinges, all is well.
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08-05-2013, 06:35 AM
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Join Date: Dec 2012
Location: Greenback, TN
Posts: 534
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Mass balance
If your building the RV14 the tube is stainless and the instructions say there is no need to prime. With that said, should you choose the prime the extra weight would not hurt in any way.
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Marvin McGraw, 5TN4
RV-14. #140039 Complete
Flight hours: 500+
2020 Dues Paid
The Dues Paid note is a reminder for me
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08-05-2013, 08:48 AM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
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My aileron tubes (9A kit) were 304 stainless, no priming needed.
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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