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  #11  
Old 11-23-2010, 11:52 AM
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ChiefPilot ChiefPilot is offline
 
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Quote:
Originally Posted by JonJay View Post
When equally equipped, empty weights are nearly identical. The 7 is a more modern design and has a bit more efficient airframe. Might see a touch higher cruise in the 7, but marginal.
How is the 7 airframe more efficient? I'm building my -6A in the same hangar as a -7 is also going together, and excluding the placement of the third wheel and the canopy opening design (tip-up vs. slider) the only differences I see externally are :

1) The -7 has the larger counter-balanced rudder same as a -9. My -6a has a smaller counterbalanced rudder similar to a -8.
2) The -7 has the sheared wingtips; my -6a has the Hoerner style tips.
3) The -7 has a slightly wider span than my -6A.
4) The -7 has a flat bottom skin between the wing spar and the cowling where the same skin on the -6A matches transitions from flat behind the cowling to a slightly convex shape to match the dehiedral angle at the point where the spars enter the fuselage.


The same cowling, wheel pants, fairings, etc. are used on both.
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  #12  
Old 11-23-2010, 02:15 PM
Pat Stewart Pat Stewart is offline
 
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One major difference not mentioned is the RV7 has the RV8 wings which include longer ailerons with crisper control characteristics.

Pat
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  #13  
Old 11-23-2010, 02:47 PM
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Default No imperical data...

Quote:
Originally Posted by ChiefPilot View Post
How is the 7 airframe more efficient? .
Only from what I have been told from "engineers" who ought to know(hint) and my own experiences flying side by side. The 7 was designed, as the 8 was, computer aided. The 6 was pretty much designed by hand.

I am sure it is arguable.
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  #14  
Old 11-23-2010, 02:49 PM
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Default Sorry pat, the oposite is true.

Quote:
Originally Posted by Pat Stewart View Post
One major difference not mentioned is the RV7 has the RV8 wings which include longer ailerons with crisper control characteristics.

Pat
The shorter winged 6 has a faster roll rate. If you have a chance to roll an 8, then roll a 6, you can tell the difference. You can search "roll rate" for the many discussions about this in the past.
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Last edited by JonJay : 11-23-2010 at 02:54 PM.
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  #15  
Old 11-23-2010, 03:01 PM
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Default Yep! It's certainly arguable.

Quote:
Originally Posted by JonJay View Post
Only from what I have been told from "engineers" who ought to know(hint) and my own experiences flying side by side. The 7 was designed, as the 8 was, computer aided. The 6 was pretty much designed by hand.
I am sure it is arguable.
I know of nothing in the -7 design that would make it "more efficient" than the -6.
The primary purpose of the -7 was to make the kit easier to manufacture and easier to build.
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  #16  
Old 11-23-2010, 05:23 PM
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JonJay JonJay is offline
 
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Default Agreed...

Quote:
Originally Posted by Mel View Post
I know of nothing in the -7 design that would make it "more efficient" than the -6.
The primary purpose of the -7 was to make the kit easier to manufacture and easier to build.
Because I dont want to break my golden rule of never arguing with those wiser (Mel)! THere may not be anything behind it, but I was told the 7 had the benefit of some pretty sophisticated aerodynamic modeling software to assist in its design. Software that was not available when the 6 was designed. But, even if that is true, there would be no way of knowing without some extensive side by side testing of like machines...so, I retract that statement. (can I do that?)
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  #17  
Old 11-23-2010, 05:59 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by JonJay View Post
Because I dont want to break my golden rule of never arguing with those wiser (Mel)! THere may not be anything behind it, but I was told the 7 had the benefit of some pretty sophisticated aerodynamic modeling software to assist in its design. Software that was not available when the 6 was designed. But, even if that is true, there would be no way of knowing without some extensive side by side testing of like machines...so, I retract that statement. (can I do that?)
RV-6's and -7's have been flying side-by-side for several years now, not sure why anyone would consider the -7 aerodynamically different from the -6. They are for all practical purposes the same airframe. The only software I am aware of that was applied to the -7 design was CAD which allowed match drilling of holes and computer generated drawings. This resulted in greater manufacturing and assembly efficiency, but not aerodynamic enhancements.

Consider your statement retracted. (except in the archives where it will live forever!!)
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  #18  
Old 11-23-2010, 06:02 PM
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Same airfoil, same fuselage cross section, longer wing span.
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  #19  
Old 11-23-2010, 06:57 PM
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Snowflake Snowflake is offline
 
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This is just speculation, but having a complete computer model would allow some very rapid iteration on design choices. If the 6 was hand designed, there would have been less iteration and more building. The design would have been finalized and moved on. Having the ability to optimize the design more on the 7 means that they could remove excess weight, shift this component slightly, shift that component slightly, etc. and still end up with essentially the same plane.
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  #20  
Old 11-23-2010, 07:12 PM
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Jamie Jamie is offline
 
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One advantage of the -7 over the -6 is if you break something. For the most part, -7 parts are plug and play. For example when my rudder was banged up in a hangar door incident I built up a new rudder and bolted it right on. The non-prepunched parts on the -6 make fabbing new parts a little tricker, although obviously still doable.
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