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  #781  
Old 05-28-2018, 09:01 PM
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WingnutWick WingnutWick is offline
 
Join Date: Jun 2013
Location: Lemoore
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I took it off and blended the gap, didn't like the way it looked! Wasn't sure what is was for anyway, seemed silly.


Quote:
Originally Posted by scsmith View Post
Its a cleaver trick of painting and lighting I hope -- it looks like an -8 without a counterweight on the rudder.
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  #782  
Old 05-28-2018, 09:04 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by WingnutWick View Post
I took it off and blended the gap, didn't like the way it looked! Wasn't sure what is was for anyway, seemed silly.
Are you kidding? You took off the rudder mass balance weight? It's there for flutter prevention!

I would strongly suggest you reduce your Vne while you build another rudder (per plans) and get it installed.
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Carl N.
Arlington, WA (KAWO)
RV-8, 350 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 05-28-2018 at 09:21 PM.
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  #783  
Old 05-29-2018, 04:42 AM
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Michael White Michael White is offline
 
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Location: Cartersville, Georgia KVPC
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Quote:
Originally Posted by RV8JD View Post
Are you kidding? You took off the rudder mass balance weight? It's there for flutter prevention!

I would strongly suggest you reduce your Vne while you build another rudder (per plans) and get it installed.

Carl...I think he was joking...the counterweight looks to be there in the picture.
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Last edited by Michael White : 05-29-2018 at 04:47 AM.
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  #784  
Old 05-29-2018, 07:29 PM
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WingnutWick WingnutWick is offline
 
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Location: Lemoore
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Default jesting indeed

Yes, totally joking. Fear not, the rudder weight is there and diligently preventing flutter through all phases of flight, it's just hard to see in that pic! Of note, now that we mention it, I am curious as to actual aerodynamic workings of these protruding weighted extensions. Anyone want to indulge my nerdy side and educate me?


Quote:
Originally Posted by RV8JD View Post
Are you kidding? You took off the rudder mass balance weight? It's there for flutter prevention!

I would strongly suggest you reduce your Vne while you build another rudder (per plans) and get it installed.
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  #785  
Old 05-29-2018, 07:51 PM
scsmith scsmith is offline
 
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Location: Ashland, OR
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Quote:
Originally Posted by WingnutWick View Post
Yes, totally joking. Fear not, the rudder weight is there and diligently preventing flutter through all phases of flight, it's just hard to see in that pic! Of note, now that we mention it, I am curious as to actual aerodynamic workings of these protruding weighted extensions. Anyone want to indulge my nerdy side and educate me?
I will describe the aero-balance benefit after I regain my composure.
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  #786  
Old 05-29-2018, 08:08 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by WingnutWick View Post
Yes, totally joking. Fear not, the rudder weight is there and diligently preventing flutter through all phases of flight, it's just hard to see in that pic!
I thought you might be kidding, but when I saw you were a Naval Aviator ... I wasn't so sure!

(Just Kidding, just kidding! )
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Carl N.
Arlington, WA (KAWO)
RV-8, 350 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 05-29-2018 at 09:55 PM.
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  #787  
Old 05-29-2018, 09:44 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by WingnutWick View Post
Of note, now that we mention it, I am curious as to actual aerodynamic workings of these protruding weighted extensions. Anyone want to indulge my nerdy side and educate me?
Mass balancing the control surface prevents coupling of the control surface rotation mode (the control surface rotating about its hinge line) with the main surface bending or torsion (twist) modes. The coupling of these modes could result in flutter.

The idea with (static) mass balancing of any control surface is to move the center of gravity of the control surface closer to the hinge line. This prevents the control surface from rotating when the main surface that the control surface is attached to (i.e., wing, fin, stab), moves. This prevents the control surface from "driving" the main surface and causing flutter to occur.

On many designs, it is not necessary to fully mass balance the control surface to prevent flutter from occurring within the design flight envelope of the airplane. A fully balanced control surface (100% statically balanced) means the CG of the control surface is exactly at the hinge line. For example, the rudder on the RVs are not fully balanced (the CG is still somewhat aft of the hinge line), and they do not need to be.

There is also dynamically mass balancing the control surfaces, but that is not necessary for our RVs.

BTW, as you know, your F/A-18s control surfaces are not mass balanced. Flutter is prevented by ensuring that there is sufficient actuator load loop stiffness (yielding a high enough control surface rotation frequency to prevent the control surface from coupling with other modes) to preclude flutter from occurring. The actuator load loop stiffness consists of the stiffness of the hydraulic actuator and the structural components that the actuators attach to.

See this post and the embedded video to see what happens when there is insufficient actuator load loop stiffness to preclude flutter:

http://www.vansairforce.com/communit...0&postcount=13

and the pilot is/was on VAF:

http://www.vansairforce.com/communit...2&postcount=19
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Carl N.
Arlington, WA (KAWO)
RV-8, 350 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 06-04-2018 at 12:28 PM.
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  #788  
Old 06-04-2018, 07:21 AM
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WingnutWick WingnutWick is offline
 
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Quote:
Originally Posted by RV8JD View Post
I thought you might be kidding, but when I saw you were a Naval Aviator ... I wasn't so sure!

(Just Kidding, just kidding! )
Carl,

Ha! I love it. Aviation wouldn't be what it is without its banter.

Awesome info! Thank you very much, that was exactly what I was looking for. Much appreciated. And written just at a level to which my smaller Navy brain could still absorb!
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  #789  
Old 06-30-2018, 07:41 PM
foxhound57 foxhound57 is offline
 
Join Date: Dec 2013
Location: Gold Coast Australia
Posts: 36
Default Show us a picture of your Finished RV-8

RV8S: Paint Finished March 2018.

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  #790  
Old Yesterday, 03:16 PM
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Lufthans Lufthans is offline
 
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Location: Hilversum, The Netherlands
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Quote:
Originally Posted by foxhound57 View Post
RV8S: Paint Finished March 2018.

WOW

A pre-punched Harmon Rocket...

That nose looks LONG. How are you in W&B?

A VERY impressive aircraft!
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