RV6A vs RV7A

[Ralph Inkster]

Have removed wings from 6,6A,7,7A,9A. The 6 & 6A were the easier of the bunch if they had to be rated. But overall they were all nasty.

[Captain Avgas]

Originally Posted by Ralph Inkster

Have removed wings from 6,6A,7,7A,9A. The 6 & 6A were the easier of the bunch if they had to be rated. But overall they were all nasty.

My experience obviously doesn't coincide with yours but I do agree that removing the wings of either a 6 or 7 is pure torture. However if I recall correctly there are 16 main spar bolts that have to be removed to take the wings off an RV7A and at least 76 that have to be removed to take the wings off an RV6A. And additionally on the 6A you have to remove the landing gear and sever all the fuselage wiring that goes through the spar web.

I've done pre-purchase inspections on 2 RV6A's and neither of them had all their centre spar bolts inserted and nuts installed. Cramped conditions and lack of access obviously made it very difficult for the builders to get some of the bolts in...so they just didn't bother. I guess they figured that there were so many bolts that leaving a couple of really difficult ones out just didn't matter.

In the end however the proof is probably in the pudding....Vans dumped the RV6 spar carry-through design when they introduced the RV7. My best guess is that this was not done for structural reasons but for access reasons. As they say, bad access is inevitably a safety issue.

Mind you, the RV7 wing attachment design also leaves a fair bit to be desired and it didn't surprise me when Vans changed their approach once again when they introduced the RV14.

[Radioflyer]

Captain Avgas (or others), please describe in a bit more detail the wing removal bolts on an a -6A. Do the 76 bolts you refers to include the multitude of screws attaching the wing root fairing strips? I have come across several -6As I would have liked to truck home due to bad engines, etc, but was afraid to because of the reported wing removal difficulties. However, if it is a perfectly good reversible process with no undue damage or modifications, I may take on such a project.

[Sam Buchanan]

Originally Posted by Radioflyer

Captain Avgas (or others), please describe in a bit more detail the wing removal bolts on an a -6A. Do the 76 bolts you refers to include the multitude of screws attaching the wing root fairing strips? I have come across several -6As I would have liked to truck home due to bad engines, etc, but was afraid to because of the reported wing removal difficulties. However, if it is a perfectly good reversible process with no undue damage or modifications, I may take on such a project.

In answer to your question, no, the 76 number refers to the bolts attaching the wing spars to the fuselage bulkhead. Removing wings in order to transport a project is certainly feasible but some of the bolts may need to be replaced if they incur damage due to scuffing. Some builders have used a rivet gun to drive stubborn bolts out of the bulkhead and several of the bolts will test your patience due to tight access. As long as reasonable care is exercised there should be no damage to the fuse or spars.

[Radioflyer]

Wow, 76 bolts for the -6A wings attachment. 38 per wing spar. I presume these include the landing gear weldment bolts. Are all 38 bolts special "tight tolerance" or just a smaller critical subset?

[Sam Buchanan]

Most are conventional AN bolts, a few are close tolerance NAS bolts.

You can get a set of plans for the RV-6/6-A on flash drive for $10, money well-spent to answer your questions:

https://shop.vansaircraft.com/cgi-bi...oduct=fd_plans

[Radioflyer]

Thanks. I think will do.

[gmcjetpilot]

Originally Posted by grubbat

The RV-6 is structurally stronger as never having an inflight structural failure. However, the -6 has more variation in the build as many were built before process automation was implemented .

The RV-7 has had several inflight structural failures but the build seems to be more consistent over the -6. The -7 is slightly larger. A well built -6 is a nice plane with lots of margins. Good luck on your search!

The hand full RV-7/A accidents that involved possible in-flight break up were explained by pilot error/loss of control and exceeding limitations (speed, G force), over stressing the air-frame, one bird strike, and one was not conclusive.

The through spar and center line spar cap splice plate of the RV-6 is a monster, but the wing wold not fail there... it would fail outboard about where the web doubler and fuel tank ends. However the Horizontal Stab might be the weaker point.

[Ralph Inkster]

Back to the joys of removing a 3/4/6 spar compared to the 7/8/9/10/14 spar attach points, is easy and simple to remove the multiples of small attach bolts compared to trying to get at and apply enough force to get the big friction fit bolts out of the later designs. The last wings I removed were a 9A and HAD to remove the gear weldments (1 hr process total for getting gear attaches out of the way, much much longer to get those bolts out), converse to the first job being a 6A where I was able to trailer it with the gear legs intact.

As for the designed strength in Vans spars- I grey out at 4.5Gs, I fly what ever RV model with specs rated to 6Gs, engineering testing was to a higher G value (9?) to a prescribed deflection of (?"), ultimate failure would be even higher than that. I feel totally safe in any RV model flying my normal 3G antics and feel its a moot point to debate an ultimate failure mode as criteria to select a RV model.

[thompsonbr87]

As a buyer, I found the differences between 6A vs 7A to be insignificant. To me, what seemed to be the biggest advantage of the 7 over the 6 is the simplification of the build process with pre-punched holes, a benefit realized by the builder, not necessarily the pilot.

What engine/HP? Prop? Avionics? Build quality? For me, these were much bigger considerations than slight improvements in gross weight, VNE, and fuel capacity.

I guess I'm trying to say is that you will likely find bigger differences comparing two specific planes than comparing the two fleets.