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  #1  
Old 10-25-2017, 11:18 AM
Varga to Vans Varga to Vans is offline
 
Join Date: Apr 2017
Location: Rolla, MO
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Default Aileron counterweight

Building RV-8A. Started looking at steel aileron counterweight's possible interference with Garmin GMU 11 magnetometer. Questioned if a solid aluminum rod screwed in place instead of the steel pipe would be OK. Told by VAN's the weight would have to match the steel pipe exactly. Then I wonder why a counterweight is needed?? I figure an unbalanced aileron would produce about 5 lbs of force in the aileron control rods. Since ailerons are attached to each other at the control stick they would counter act each other so the control stick requires zero force. In other words the right aileron counterbalances the left aileron. It would be an extra 5 lbs of force on the control rods but is that not insignificant in comparison to the load when banking at 200mph? Has anyone dared to leave the aileron counterweights off, or replace them with an aluminum tube to provide some stiffness to the ailerons leading edge??
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  #2  
Old 10-25-2017, 11:21 AM
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Toobuilder Toobuilder is offline
 
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The counterweights are there to combat individual surface flutter, not provide a balanced "feel" for the pilot.
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  #3  
Old 10-25-2017, 11:41 AM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by Toobuilder View Post
The counterweights are there to combat individual surface flutter, not provide a balanced "feel" for the pilot.
+1. This is an area where experimenting may be extremely dangerous. Please do not remove the weights unless you are really sure of what you are doing.
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  #4  
Old 10-25-2017, 11:44 AM
Varga to Vans Varga to Vans is offline
 
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Location: Rolla, MO
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Default aileron counterweight

Now I get it. I found a youtube clip that explains the counterbalance requirement.https://youtu.be/EmfHBs9QPT8. The title is Aeroeleacticity matters. It affects wing twist.

I am still considering using a 7/8" solid aluminum rod with some aluminum tubing added to it to get the exact weight required. Attaching the rod in place with #6 screws countersunk using the rivet holes in the skin. The apparent advantage is better places to install the GMU 11 and no concern with steel corrosion.

What disadvantages of doing this am I missing?
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  #5  
Old 10-25-2017, 11:56 AM
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F1Boss F1Boss is offline
 
Join Date: Aug 2006
Location: Taylor Texas
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Default 'Get the lead out!'

You should use lead as the counterweight mass - mix shot with epoxy resin and flox to get it to stay where you want it - inside an aluminum tube, for example.

Lead is non-magnetic - as far as I can tell...so there should be no problem.
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  #6  
Old 10-25-2017, 11:56 AM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Make sure you duplicate the moment of inertia, not just the weight.
You are putting the cart before the horse. By the time youíre ready for avionics, new and better ones will likely be available so your plans may change. Nothing wrong with thinking about it, just try to not lock yourself in.
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  #7  
Old 10-25-2017, 01:32 PM
WA85 WA85 is offline
 
Join Date: Apr 2010
Location: Madison, AL
Posts: 107
Default Dynon ADAHRS in the wing nearby to steel gear legs / steel aileron pipe

I mounted my Dynon ADAHRS (with integrated magnetometer) on inboard inspection panel on the bottom of the LH wing of my RV-8. I have had zero issues with calibrating, or the operations of, the ADAHRS, despite the nearby steel landing gear legs and steel pipe in the LH aileron. I know of two other RVs (RV-8 / RV-9A) that did the same without issues. However, the Garmin magnetometer may be more susceptible to nearby ferrous materials than the Dynon, so your results may vary.
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  #8  
Old 10-25-2017, 02:01 PM
David Paule David Paule is offline
 
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Location: Boulder, CO
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Best to leave it the way it is designed.

Any substitution will affect both the mass moment of inertia and the stiffness of the aileron as well as the mass balance of the aileron, and all are factors in preventing flutter.

Dave
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  #9  
Old 10-25-2017, 02:04 PM
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Carl Froehlich Carl Froehlich is offline
 
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Default Donít look for solutions until you have a problem

I know of no reported issues as you discribe.

Carl
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  #10  
Old 10-25-2017, 05:18 PM
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Bob Kuykendall Bob Kuykendall is online now
 
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Quote:
Originally Posted by Varga to Vans View Post
...It affects wing twist...
Well, more like affects wing shaking itself off of the airplane.

Not to dogpile this, but mass balancing is pretty serious business, and you mess with what's there at your peril.

I think that way back in the way back when, the counterweights were just chunks of standard 1" or so water pipe. Somehow I think I recall that the latest couple or three generations of kits use stainless steel water pipe. If that's the case, it's probably a lot less magnetic than it used to be, and might not be magnetic at all.
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