Van's Air Force
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Compatibility RV8/RV7 Empennage
- Thread starter FrenchRV8
- Start date
Hi Mickey,
I think you are right .
Vertical stabilizer is ok
Rudder has not the same trailing edge
Horizontal EMP is not the same as drawing 3 is titled RV8 only .
Thanks
The build # starts with the tail, just from a paperwork side not sure Vans is going to help you get the paperwork side right if you start with the wrong tail. I may be wrong.
Some tails parts are the same, for example the RV9 Vertical is the same as the 8, the fiberglass top and rudder are not.
If you look at the drawings, you can see what tail components are shared with other models.
Some tails parts are the same, for example the RV9 Vertical is the same as the 8, the fiberglass top and rudder are not.
If you look at the drawings, you can see what tail components are shared with other models.
The rudder and the horizontal stabilizer are different.
Mark33
Well Known Member
I’m not 100% sure if the entire empennage is completely exchangeable or will bolt right up, but I’d bet they are. I do know that the rudders are different, but as others have mentioned, other than the fiberglass caps on the rudder and VS, the 7 and 8 rudders are interchangeable. In the early days, the 7 came with the 8 rudder, but later switched to the 9 rudder. A lot of people have decided to remove their 9 rudder and go back to the 8 rudder. In my opinion, the 8 rudder is the best/strongest one Vans ever made. It’s made with thicker skins and is also a one piece “wraparound” design rather than two skins riveted at the trailing edge. If for no other reason, the 8 rudder definitely looks a lot better on a 7.
Mine was a later 6 and had the 8 rudder. I thought they actually made a 7 rudder initially, but maybe it was just the 8 rudder used on the 6. Whatever it was, I know it was quickly swapped for the 9 rudder, as Van didn't like the spin recovery characteristics. Disliked it enough, or scarred enough, to give every customer a free replacement 9 rudder. I would do some real research on the risks before swapping it out. Also not a fan of the wedge TE, but think I would rather have the option of safely getting out of a spin over a stronger rudder design or cool looks.
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There is a guy who built a mongrel RV6 with parts and pieces from the RV4 kit and what else. But this guy is an experienced builder who knew what he was doing. If you are a beginner like most of us who is building our very first kit airplane, it easier to sleep at night if you build from the plan. But this is experimental aviation and only you can make that decision. Good luck.
Mark33
Well Known Member
Yeah, there was information that Vans published back in the day regarding the differences in the spin recovery characteristics of the two rudders. From what I remember reading, I think it was a half or possibly a full turn difference, but I could be wrong. I realize everyone’s comfort level is different at different stages of flight, but having a stronger rudder at higher speeds is more important to me than a bigger one at slow speeds. Unless I’m purposefully practicing spin/recovery maneuvers at an appropriate altitude, I personally never put the airplane in a flight attitude that could potentially put it in a low altitude spin. I’d certainly never attempt to talk anyone into swapping their 9 rudder for an 8 due to looks alone, but for me the potential differences in spin/recovery as a significant additional safety factor isn’t an issue at all as compared to the benefits of a stronger one at higher speeds.
Ralph Inkster
Well Known Member
Scott gave you the right answer. The big issue is the RV8 fuselage is narrower than the RV7. The center section of the Horizontal Stabilizer in the RV8 kit will not bolt up properly to the wider RV7 fuselage longerons.
Rudders have same mounting brackets between the 7 & 8. & as you can see above, there are varying opinions which is ‘best’.
Good luck
Rudder
With the exception on one "mongrel" which was called a RV6 but was not an RV6 there has never been a structural failure accident with a RV6. Not so with the RV7.
Study the accident reports and then decide if you want the strongest rudder or one that will allegedly improve spin recovery.
With the exception on one "mongrel" which was called a RV6 but was not an RV6 there has never been a structural failure accident with a RV6. Not so with the RV7.
Study the accident reports and then decide if you want the strongest rudder or one that will allegedly improve spin recovery.
On my -7A, I built it with the larger 9 rudder with the wedge 18 years ago. Nine years ago, I re-skinned it prior to getting a paint job because I has stop drilled several cracks emanating from rivets. It remained pristine until a year and a half ago when it got whacked by a gusty tailwind, which bent/broke both of the rudder locks I had on it. While it was serviceable after some re-bending, it never flew quite the same as before the incident.
At that point, I said enough, so I built an original 7/RV-8 rudder, which I just installed on the plane. I feel like I have my old plane back. Frankly, I can't really tell the difference as I fly exclusively cross-country. For confirmation, I noted at Oshkosh this year that Van's RV-7A demonstrator has the same original 7/RV-8 rudder installed on it.
At that point, I said enough, so I built an original 7/RV-8 rudder, which I just installed on the plane. I feel like I have my old plane back. Frankly, I can't really tell the difference as I fly exclusively cross-country. For confirmation, I noted at Oshkosh this year that Van's RV-7A demonstrator has the same original 7/RV-8 rudder installed on it.
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RV8JD
Well Known Member
Rudders
I would not put an RV-9/7 rudder on an RV-8 (or an RV-7). Early in the history of the RV-7, the RV-9 rudder was adopted and supplied with all RV-7 kits after 5/20/2020, hence the RV-9/7 nomenclature.
My post linked below explains why the the RV-8 rudder provides larger strength and flutter margins than the RV-9/7 rudder:
https://vansairforce.net/community/showpost.php?p=1627863&postcount=16
Note also that the RV-9/7 rudder was originally designed for the RV-9, which has a Vne of 210 MPH TAS. The RV-8 and RV-7 have a Vne of 230 MPH TAS.
FWIW, to my knowledge Van's has not tested the RV-8 with the RV-9/7 rudder. The RV-8 (1995) flew before both the RV-9 (1997) and the RV-7 (2001).
Instead of rehashing it all again in this thread, newer forum members can view this thread:
I would not put an RV-9/7 rudder on an RV-8 (or an RV-7). Early in the history of the RV-7, the RV-9 rudder was adopted and supplied with all RV-7 kits after 5/20/2020, hence the RV-9/7 nomenclature.
My post linked below explains why the the RV-8 rudder provides larger strength and flutter margins than the RV-9/7 rudder:
https://vansairforce.net/community/showpost.php?p=1627863&postcount=16
"... For the reasons given below, the -8 rudder would provide larger strength and flutter margins in case of an inadvertent excursion outside the published flight envelope:
- The -8 rudder has thicker skins (0.020") than the -9/-7 rudder (0.016"), making the -8 rudder stronger and stiffer.
- The -8 rudder has a folded trailing edge, which makes the -8 rudder stiffer and stronger than the riveted trailing edge of the -9/-7 rudder.
- The -8 rudder has less area than the -9/-7 rudder, creating smaller unsteady (oscillatory) aerodynamic forces (which are an important item in the flutter equation) than the larger -9/-7 rudder. ..."
- The -8 rudder has thicker skins (0.020") than the -9/-7 rudder (0.016"), making the -8 rudder stronger and stiffer.
- The -8 rudder has a folded trailing edge, which makes the -8 rudder stiffer and stronger than the riveted trailing edge of the -9/-7 rudder.
- The -8 rudder has less area than the -9/-7 rudder, creating smaller unsteady (oscillatory) aerodynamic forces (which are an important item in the flutter equation) than the larger -9/-7 rudder. ..."
Note also that the RV-9/7 rudder was originally designed for the RV-9, which has a Vne of 210 MPH TAS. The RV-8 and RV-7 have a Vne of 230 MPH TAS.
FWIW, to my knowledge Van's has not tested the RV-8 with the RV-9/7 rudder. The RV-8 (1995) flew before both the RV-9 (1997) and the RV-7 (2001).
Instead of rehashing it all again in this thread, newer forum members can view this thread:
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