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  #21  
Old 12-22-2011, 09:27 AM
SteinAir SteinAir is offline
 
Join Date: Feb 2005
Location: Minneapolis
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Most posts are fairly accurate, but the details behind them are a little bit different than people sometimes assume. The interior sizing differences between the 6/7 aren't just because the 7 is "bigger". Realize that the floor of the 6 has dihedral at the spar to match where the spars come together straight in from the wings whereas the 7/9 fuse has a flat bottom to match the separate spar carrythrough. The spar carrythrough bulkhead on the 6 protrudes almost an inch further inboard on each side than the 7. The seat ribs of the 7 actually lower your position in the fuselage over the relatively flat lower seat ribs in the 6 (they are quite different if you put the two ribs side by side to compare).

In the end we've built/flown both numerous times and I think in the end you'd be happy with ANY Van's RV aircraft. You can't beat a well built light 6 for doing wifferdills in the sky, but the 7 sure lands nice and the extra couple gallons can be nice. The 6's with the original small tails can waggle a bit in bumpy air and is good looking on TD's, but the larger tails on both the later 6's (and either version of the 7 tail) are nice for aggresive slips and xwinds.

Panel position and cowl positions are pretty much the same relative to the canopy deck rails as is the position of the engine. If you take a 6/7 put them nose to nose things are pretty much the same - though the different seating positions in the cockput may induce you to think otherwise and the extra 1" to the rudder pedals is nice for us tall folk.

The 7 is infinitely easier to build (and fix) as it's from a standardized pre-punched package, where many of the 6's were jig built.

In the end, it's like everyone says....any of them are great. There are some real bargains out there on 4's and 6's right now (barely over the cost of the FFW and systems) so if they were built good/straight/light you'll be happy with it.

Just my 2 cents as usual!

Cheers,
Stein
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  #22  
Old 12-22-2011, 10:10 AM
mikerkba mikerkba is offline
 
Join Date: Sep 2008
Location: Ely, Nevada
Posts: 229
Default You are the builder, remember that.

Quote:
Originally Posted by twsurveyor View Post
A few years ago, I saw an RV-6A at OSH with a 2250 lb GW on the data plate. Gee, that's only 600 lb over Van's recommended GW!
My 7A is certified and dataplated at 2000 pounds gross. The inspector did not ask about that since gross weight determinations are legally within the discretion of the builder, nor did he comment or question my designation as 1800 lb utility category operation and 2000 for normal category operation.

Van's educated and informed engineering commentary on gross weight selection is right on the money. My selection of an increased weight is not intended to challenge his engineering. Its was, as much as anything, a regulatory decision. I'm a aviating aviation lawyer, not an aeronautical engineer. I have never flown the plane above 1800 lbs, but I'm not going to set myself up for a violation, particularly a paperwork violation when I control that paperwork, with the FAA.

A prudent lawyer might advise Vans that any and all variations from his specific design act to reduce his (already minimal) exposure to tort claims. This would be particularly true of significant mods such as gross weight or "unusual" powerplant selections. That could ultimately make all of our creative variations from his well documented, blueprinted, and manual-specified build materials actually good for the company. We have all heard of planes so changed from the plans that reportedly Van's says, simply, "Its not an RV-3" (or 6, etc). (Following the same logic, the original builder might increase their exposure from a subsequent operator or owner of that same plane if they don't well document variations from the plane and/or call out the change(s) in some way that the other party is on notice.)
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BUILDER: N92MB RV7A (A/W 3/2009) - Sold
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Building: S-21 Outback/Titan, tail and cockpit mated (3/2020)
KELY/Ely, NV
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  #23  
Old 12-22-2011, 10:13 AM
Sam Buchanan's Avatar
Sam Buchanan Sam Buchanan is offline
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Join Date: Dec 2004
Location: North Alabama
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Quote:
Originally Posted by SteinAir View Post
Most posts are fairly accurate, but the details behind them are a little bit different than people sometimes assume. The interior sizing differences between the 6/7 aren't just because the 7 is "bigger". Realize that the floor of the 6 has dihedral at the spar to match where the spars come together straight in from the wings whereas the 7/9 fuse has a flat bottom to match the separate spar carrythrough. The spar carrythrough bulkhead on the 6 protrudes almost an inch further inboard on each side than the 7. The seat ribs of the 7 actually lower your position in the fuselage over the relatively flat lower seat ribs in the 6 (they are quite different if you put the two ribs side by side to compare).

In the end we've built/flown both numerous times and I think in the end you'd be happy with ANY Van's RV aircraft. You can't beat a well built light 6 for doing wifferdills in the sky, but the 7 sure lands nice and the extra couple gallons can be nice. The 6's with the original small tails can waggle a bit in bumpy air and is good looking on TD's, but the larger tails on both the later 6's (and either version of the 7 tail) are nice for aggresive slips and xwinds.

Panel position and cowl positions are pretty much the same relative to the canopy deck rails as is the position of the engine. If you take a 6/7 put them nose to nose things are pretty much the same - though the different seating positions in the cockput may induce you to think otherwise and the extra 1" to the rudder pedals is nice for us tall folk.

The 7 is infinitely easier to build (and fix) as it's from a standardized pre-punched package, where many of the 6's were jig built.

In the end, it's like everyone says....any of them are great. There are some real bargains out there on 4's and 6's right now (barely over the cost of the FFW and systems) so if they were built good/straight/light you'll be happy with it.

Just my 2 cents as usual!

Cheers,
Stein
Excellent post, Stein. This was the first time I recall seeing the differences in spar boxes/bulkheads being described and how they impact seat ribs.

Bottom line when shopping for an RV.....base the decision on the individual build quality and equipment, not whether or not it is a -6 or -7.
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  #24  
Old 12-22-2011, 11:10 AM
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Rick6a Rick6a is offline
 
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Location: Lake St. Louis, MO.
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Default Yes!

Quote:
Originally Posted by SteinAir View Post
Most posts are fairly accurate, but the details behind them are a little bit different than people sometimes assume....Stein
Quote:
Originally Posted by Sam Buchanan View Post
Excellent post, Stein....Bottom line....base the decision on the individual build quality and equipment, not whether or not it is a -6 or -7.
One thing is for certain. This perennial subject can be counted upon to generate a lot of verbage and some of it is obviously partisan in nature. While there is nothing wrong with any proud builder expressing personal preference, Stein and Sam took an entirely dispassionate approach. As far as I am concerned, these two talented builders covered just about everything that ever needs to be said about design differences and they conveyed the information with uncommon clarity. Thanks guys.
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  #25  
Old 12-22-2011, 11:42 AM
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Flyfalcons Flyfalcons is offline
 
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Location: Bonney Lake, WA
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Gurley mon! You can't hover an RV! You been following my build on the Giants?
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  #26  
Old 12-22-2011, 11:48 AM
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Mark12A Mark12A is offline
 
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Location: Huntsville, AL
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Quote:
Originally Posted by Flyfalcons View Post
Gurley mon! You can't hover an RV! You been following my build on the Giants?
Helicopters don't fly. They beat the air into submission. But I must admit that a max performance takeoff in an H53 is relatively impressive. Got the pilot in trouble, but he thought it was worth it.
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  #27  
Old 12-22-2011, 02:03 PM
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N355DW N355DW is offline
 
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Location: Port St Lucie, FL
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If the wing is stronger in the -6 than the -7 (and I have heard that also), what is it about the -6 that would limit it's acro gross weight so much more than the -7?
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  #28  
Old 12-22-2011, 03:36 PM
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JonJay JonJay is offline
 
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Location: Battleground
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Quote:
Originally Posted by N355DW View Post
If the wing is stronger in the -6 than the -7 (and I have heard that also), what is it about the -6 that would limit it's acro gross weight so much more than the -7?
You can do a search on this topic to nausium.(sp).
Basically, I don't think anybody knows which is stronger, even the factory. There where a lot of conservative numbers placed on the earlier RV's to account for build variables. The newer designs leave a lot less for the builder to do, so they are less prone to builder variance.

Those conservative numbers fit just fine with the then much lighter builds and still produced a very useful useable load. But, the poor 6 has gotten much fatter over the years. Someone needs to retest it at a current more average empty weight. I bet tests would prove it to +6 -3 at much higher gross weights than originally published. However, that is just a guess and no, you can't have my wing to test it. I use it too much!
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  #29  
Old 12-22-2011, 03:53 PM
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Flyfalcons Flyfalcons is offline
 
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Quote:
Originally Posted by Mark12A View Post
Helicopters don't fly. They beat the air into submission. But I must admit that a max performance takeoff in an H53 is relatively impressive. Got the pilot in trouble, but he thought it was worth it.
I'm talking about RC. Jon knows.
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  #30  
Old 12-22-2011, 04:10 PM
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Mark12A Mark12A is offline
 
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Quote:
Originally Posted by Flyfalcons View Post
I'm talking about RC. Jon knows.
Sorry. I had a senior moment, going back to my time in CSAR with the only experience I've had with hovering. Our 130 pilots and the helo pilots would go back and forth. We had a couple of F15 drivers who transitioned to helicopters and you would have thought they had been emasculated or something.

And I'm not going to go forward with the -8 vs -3 thing, either. Judging by the posts here, it won't get much traction.
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