RV-7/9?

[Noah]

The RV-7 and 9 have substantially different capabilities, missions, takeoff and landing distances, cruise speeds, etc. etc. But isn't the only difference between the two kits the wing? Couldn't you build a 160hp RV-7 and then build an RV-9 wing that you could install on the RV-7 when you were doing a mission that required it? Think about it, a whole 'nother airplane for a little more than the cost of a wing kit!

I realize that structural considerations for an RV-9 limit you to 160hp engines (Ref http://vansaircraft.com/pdf/hp_limts.pdf) and I believe that these structural limitations are inherent in the wing design, not the fuselage or empennage. What other technical limitations might there be on making this work? Has anybody ever done this?

Given that a lot of builders get to the wing and never progress beyond that, there are quite a lot of partially completed wing kits out there that could be purchased at a discount. If you made your lights, pitot system, etc compatible you could make the wing plug-and-play. The factory-drilled holes in the spar for the wing-bolts might present an issue, but if those are done on a jig, doesn't it stand to reason that those should fit too?

What say ye, seasoned RVers?

[rv7charlie]

Wing chord is different. Are the spars a different distance apart?
Have you checked on whether the wing center section is the same for the two wings?

Horizontal stab/elevator is different aspect ratio to match the wing so the horizontal would need to be changed with the wing.

Charlie

[N941WR]

Noah,

The -9 has a much large HS and elevator, in addition to a different wing.

The other differences are the spar center section (The -9 has more dihedral than the -7.), the tank attach point is different as are the locations for the fuel and vent lines, the -9 has different seat ribs and seat pans, forward of the spar it is different too.

The rear spar location/size looks to be the same.

Other differences that I can think of are the side skins and some other miscellaneous parts. Oh, the -9 (taildragger) has longer landing gear than the -7 so the wing is stalled in the three point attitude. The -9A & -7A might share the same gear legs, I don't know.

Other than not wanting to remove those wing bolts, it really isn't a possible.

[dedgemon]

Originally Posted by Noah

The RV-7 and 9 have substantially different capabilities, missions, takeoff and landing distances, cruise speeds, etc. etc.

The only appreciable difference between the two is that the 7 is stressed acro (at 1600 lbs I think) while the 9 is stressed utility (at 1600)

The flight qualities are actually more alike than different. The 7 will roll a little faster with lighter forces while the 9 will stall slower (by 5 or 6 mph).

They will both fall out from under you if too slow.

Cruise speeds are "identical" compared to 7's with the same engine/prop combo. (Ask me how I know )

[Greg Arehart]

When you put the wings on for the final time wrestling with those bolts, you will probably decide that changing wings is not worth the hassle. Might be a bit easier on the 9/7 vs. the 9A/7A because of the location of the gear but....

greg

[L.Adamson]

I really see no point at all. I jumped from hours in two different 9A's, to a 6A; and it was really a non-event. A friend who owns a 9A has flown my 6, and he says the same thing. Now I realize the 6 isn't a 7, but I hear they're close enough.

So the point is.............why go to all the trouble?It's a bit on the major side of work, when it comes to mounting wings. Let alone doing it on a "whim"!

In fact, now that I've done major cross countries in the 6 as well as the 9's; I don't even think about the differences. They are so........much the same! Takeoff and landing speeds differ a bit; and the 9 is a hair more stable, and not for "simple" aerobatics. But that's about all! There is just not enough differences in the "mission" to make it worth it!.........IMO

And P.S., as previously mentioned----from experience, the 9 can fall out from under, as does the 6 .

L.Adamson ----- RV6A