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-   -   RV-7 vs RV-6 flying qualities & other differences (https://vansairforce.net/community/showthread.php?t=65262)

ChiefPilot 11-23-2010 11:52 AM

Quote:

Originally Posted by JonJay (Post 487494)
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.

Pat Stewart 11-23-2010 02:15 PM

One major difference not mentioned is the RV7 has the RV8 wings which include longer ailerons with crisper control characteristics.

Pat

JonJay 11-23-2010 02:47 PM

No imperical data...
 
Quote:

Originally Posted by ChiefPilot (Post 487501)
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.

JonJay 11-23-2010 02:49 PM

Sorry pat, the oposite is true.
 
Quote:

Originally Posted by Pat Stewart (Post 487553)
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.

Mel 11-23-2010 03:01 PM

Yep! It's certainly arguable.
 
Quote:

Originally Posted by JonJay (Post 487561)
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.

JonJay 11-23-2010 05:23 PM

Agreed...
 
Quote:

Originally Posted by Mel (Post 487568)
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?):cool::cool:

Sam Buchanan 11-23-2010 05:59 PM

Quote:

Originally Posted by JonJay (Post 487601)
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?):cool::cool:

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!!)

Mel 11-23-2010 06:02 PM

Same airfoil, same fuselage cross section, longer wing span.

Snowflake 11-23-2010 06:57 PM

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.

Jamie 11-23-2010 07:12 PM

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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