RV7-RV9

[airguy]

Originally Posted by Captain_John

Don't listen to Bill. He has a 9...

There is nothig that a 9 can do that a 7 can't!

. CJ

You mean other than cruise at 155 KTAS at 17,500 on 6 gph? Come on out and form up on me, we'll give it a shot...

They are both great airplanes, just with slightly different intended missions. The 9 wing is optimized for more efficient cruise at altitude where the 7 was designed with gentlemans aerobatics in mind.

[rvbuilder2002]

Originally Posted by Kyle Boatright

I've never seen anything from Vans that supports this claim.

Because it has nothing to do with the airplane being approved for aerobatics.....

[ChiefPilot]

Originally Posted by airguy

You mean other than cruise at 155 KTAS at 17,500 on 6 gph? Come on out and form up on me, we'll give it a shot...

Many RVs can do that - it's not that difficult. Most that can probably don't even need to go that high.
Here's an RV-6A doing it at 11k (12.5k DA) on 180hp: https://www.youtube.com/watch?v=dSDvj4cvP8A

[MikeyDale]

Originally Posted by airguy

You mean other than cruise at 155 KTAS at 17,500 on 6 gph? Come on out and form up on me, we'll give it a shot...

They are both great airplanes, just with slightly different intended missions. The 9 wing is optimized for more efficient cruise at altitude where the 7 was designed with gentlemans aerobatics in mind.

Originally Posted by ChiefPilot

Many RVs can do that - it's not that difficult. Most that can probably don't even need to go that high.
Here's an RV-6A doing it at 11k (12.5k DA) on 180hp: https://www.youtube.com/watch?v=dSDvj4cvP8A

Better get the popcorn! I see where this threads headed!

[Captain_John]

Originally Posted by airguy

You mean other than cruise at 155 KTAS at 17,500 on 6 gph? Come on out and form up on me, we'll give it a shot...

They are both great airplanes, just with slightly different intended missions. The 9 wing is optimized for more efficient cruise at altitude where the 7 was designed with gentlemans aerobatics in mind.

Greg, honestly I've never tried to go that slow in cruise configuration.

I will give it a try on my way to the airshow and let you know how I make out. Are you going to be at the beer thing on Sunday? We can talk there.

CJ

[PerfTech]

Originally Posted by alpinelakespilot2000

Except glide substantially farther when your engine fails and land 10 knots slower so that you are more likely to survive the ensuing off field landing!

Seriously, to the OP, this has been hashed out numerous times on this forum. Do an RV-9 vs RV-7 thread search and you'll have plenty of reading.

....Don't forget speed, 9 is faster, more economical, takes off shorter, lands shorter, climbs faster, and allows you to say,"Mine is bigger than yours".

[rmartingt]

Originally Posted by ChiefPilot

I've never really thought along those lines before. "Stiction", eh?

Bottom line is that the -7 airframe is, in fact, stronger. Opinions vary, but numbers don't lie: the -7 is rated to +4.4G at 1800lbs gross weight while the -9 is rated to +3.8G at 1750lbs. Drop it to 1600lbs, at the -7 is rated to +6G while the -9 is rated to 4.4G.

Unless you are doing aerobatics, that should have no practical bearing on your decision though. Both are good airplanes.

Most likely it's related to bending moment at the wing root. The longer wings on the -9 will generate more bending moment for a given amount of lift than on a -7. The design trades g loading for cruising efficiency and somewhat lower stall speeds. And while the lower aspect ratio and different airfoil on the -7 may well be capable of a bit more AOA before stalling (I don't know), that's not a primary driver in the design, nor is it related to g capability.

I've kicked around the idea of making my wingtips quick-swappable and building a pair of raked "cruise" tips for my -7. I could swap them out for longer trips and realize some small efficiency gains, at the cost of giving up some g capability while they're installed. But I'd have to do the engineering on that to make sure I wouldn't be increasing the bending loads outside the original design envelope. I do know it's been done before on a -6.

[airguy]

Originally Posted by Captain_John

Greg, honestly I've never tried to go that slow in cruise configuration.

I will give it a try on my way to the airshow and let you know how I make out. Are you going to be at the beer thing on Sunday? We can talk there.

CJ

Unfortunately no - my airplane is (finally!!) in the paint shop right now and won't be out in time for Oshkosh, and I am completely buried at the office right now (good thing, not complaining) so I'm out for Oshkosh.

As for the performance - I know my 9A is superior to all other aircraft, because it's mine!

How's that logic fer ya?

[Captain_John]

Originally Posted by airguy

Unfortunately no - my airplane is (finally!!) in the paint shop right now and won't be out in time for Oshkosh, and I am completely buried at the office right now (good thing, not complaining) so I'm out for Oshkosh.

As for the performance - I know my 9A is superior to all other aircraft, because it's mine!

How's that logic fer ya?

Lol, I love it!

I always say that there are two kinds of planes out there... RV's and everything else. I suppose we could all say that there are two kinds of RV's also... Mine and everyone else's!

Hahaha

I did a little math. If you take your 155 knots at say... 7 gph (I am not bringing oxygen to Oshkosh, so 7 gpg at 12,500 will have to do), it comes back at a little over 22nmpg. Lets say I plan 160 knots at 8 gph, it comes back at exactly 20 nmpg.

I wonder what happens if I bring the black knob out a little bit farther and dial in your aforementioned 155 knots?

I will let you know what I discover!

CJ

[CubedRoot]

You guys with your fully built RV's, bragging about which one is faster and/or more efficient...

And here I am, poking around in my 47 year old Cessna wishing my RV was done. HAH!