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Not Just Another 7 vs 9 Thread

The mission: Fly from the Midwest to Alaska and back in an airplane you built yourself.

The first considerations: What airplane, RV7 vs RV9, nose wheel vs tailwheel, c/s vs fixed, carbureted vs injected? If it weren't for Vlad, everyone would say 7 for fuel capacity, c/s for takeoff performance, injected for LOP, and tailwheel for gravel runways. But Vlad is inspiring!

Assume 180hp RV7 or 160hp RV9, no interest in aerobatics, and no interest in aftermarket fuel mods.

Are you planning to build or buy? If buying, I suspect you'll find a -9(A) faster than a -7(A). Either will serve your mission well. The rest is likely nit-picking around the fringes of your mission scope (short field, O2 at high altitudes).

When I was looking for a used kit, everything was on the table but I found a great deal on a -7A first. If I'd found a similar deal on a -9 first, I'd be flying it and be just as happy. I enjoy doing rolls and look forward to loops but that ability was not critical to my decision making.

One advantage not mentioned about an A model is lower insurance cost. The tail-wheel folks (no offense intended) never seem to compare the number of ground loops with the number of nose gears that folded :D
 
This thread, combined with further research here, other sites, Van's, etc., brings me to this summary, as relates to the 3000nm AK trip. Assume two airplanes built per Van's recommendations, i.e., 160hp RV9 and 180hp RV7:

1) 100 mi range advantage 7.
2) 100 ft takeoff/landing distance advantage 9.
3) Cruise speed 10+ knots advantage 7.
4) 8 mph stall speed advantage 9.
5) The prices are almost identical, subject to prop choice.

So the 9, with 20hp less, costs the same as the 7. What does the 9 give back in return for that 20ph?

Because I'm a contrarian, I really want to prefer the 9 taildragger. But this morning's math is providing a hurdle.

... I think there are a few things in this thread that were overlooked and possibly could be misconstrued by some. I see these numbers thrown out from Van's website for comparison purposes, and no one has mentioned (or I missed it) the fact that the RV-7 numbers on Van's site were gathered with a C/S prop, and the RV-9 numbers were with a F/P. This really changes the game as in take off and landing distances for one, as well as climb. I have a C/S on my 9 and believe me that is a real game changer. I routinely fly off a 500 ft. strip with obstacles at gross, and have yet to see that from another model. Also comparing the two aircraft at 8000' where the 7s perform there best isn't exactly apples with apples. My 9-A cruises @ 207 tas. on 7.1 gph. @8000', when up where I usually cruise 14,500 the fuel burn drops to less than 6.5 gph. with no reduction in tas. This reduction also considerably extends the range to five hrs. with reserve, (about 1,000 miles). Another thing I really like with the 9 series is the rock solid feel at higher altitudes. I fly high (16,500) when winds favor it, and the 9 doesn't even begin to drop its tail and mooch around like models designed to fly at lower altitudes. To me, for what I do the 9s are the best I have seen! The 7s in all fairness do have some advantages, as in aero rating, will fit in a smaller hangar, easier to wash, cheaper to paint, and the #7 just sounds lucky...:rolleyes::rolleyes:
 
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Allan, what engine are you using to get that TAS?

....160 HP 320. I do run my rpm up higher, as my prop is modified to work better at the higher rpm. This will allow the engine to make a few more horses. I have also paid a lot of attention to eliminating as much aero drag as possible, as well as some rigging changes etc. Thanks, Allan..:D
 
... I think there are a few things in this thread that were overlooked and consequently misrepresented. I see these numbers thrown out from Van's website for comparison purposes, and no one has mentioned (or I missed it) the fact that the RV-7 numbers on Van's site were gathered with a C/S prop, and the RV-9 numbers were with a F/P. This really changes the game as in take off and landing distances for one, as well as climb. I have a C/S on my 9 and believe me that is a real game changer. I routinely fly off a 500 ft. strip with obstacles at gross, and have yet to see that from another model. Also comparing the two aircraft at 8000' where the 7s perform there best isn't exactly apples with apples. Me 9-A cruises @ 207 tas. on 7.1 gph. @8000', when up where I usually cruise 14,500 the fuel burn drops to less than 6.5 gph. with no reduction in tas. This reduction also considerably extends the range. Another thing I really like with the 9 series is the rock solid feel at higher altitudes. I fly high (16,500) when winds favor it, and the 9 doesn't even begin to drop its tail and mooch around like models designed to fly at lower altitudes. To me, for what I do the 9s are the best I have seen! The 7s in all fairness do have some advantages, as in aero rating, will fit in a smaller hangar, easier to wash, cheaper to paint, and the #7 just sounds lucky...:rolleyes::rolleyes:

Interesting idea that something can be overlooked and thus misrepresented.

One of the strengths of the 9, IMHO, is the lower stall speed and all that implies.

But you won?t find me ignoring the advice from Vans is it? A A pilot of an RV- 9A who is exceeding structural cruise speed, no matter how carefully and skillfully he flies, is not in control of the critical factors and is putting himself and his passengers at risk.

Have a look at the advice on engine size before pushing the limits. If you are going into that territory you might be much safer in the 7 due to its extra strength. If you choose to fly close to VNE I hope your guardian angle or whoever looks after you is looking out for you.
 
...
But you won?t find me ignoring the advice from Vans is it? A A pilot of an RV- 9A who is exceeding structural cruise speed, no matter how carefully and skillfully he flies, is not in control of the critical factors and is putting himself and his passengers at risk.
...

207 mph TAS is not beyond the Vne of 210 mph TAS. It is close, very very close.

Allan must have some tricks up his sleeve because my O-360 powered -9 tail dragger will hit the wall right at 200 MPH / 175 knots, which is just fine by me.

His comments about flying high are right on the mark. Even at 17.5 the -9 is still flying nose down. Whereas the short wing RV's are flying nose up at those altitudes.
 
207 mph TAS is not beyond the Vne of 210 mph TAS. It is close, very very close.

Allan must have some tricks up his sleeve because my O-360 powered -9 tail dragger will hit the wall right at 200 MPH / 175 knots, which is just fine by me.

His comments about flying high are right on the mark. Even at 17.5 the -9 is still flying nose down. Whereas the short wing RV's are flying nose up at those altitudes.

The point is that those speeds are getting near the edge for the RV9. Read the warning on the Vans web page link. That is dangerous territory for the 9. Good luck if you go there deliberately.

It?s not chance that link is only on the 9 page. The dangers are there for any aircraft but it?s a tighter corner for the 9.

As for how Alan gets that extra 7mph. Well I?ve seen all sorts of things claimed on the internet, I certainly don?t believe it all. Let?s hope however it?s done that he has covered the dangers inherent in that speed in the 9.
 
Tom wasn't referencing Vne. Max structural cruise speed, Vno, is something different.

....Only cruise in smooth air at the quoted speeds, and have
performed many mods to add some extra strength in critical
areas. We may offer some more of these mods on our website
in the future. We see lots of interest in these, but are still in
the testing stage at present. Thanks, Allan:D
 
The picture you posted earlier in this thread, in post #8, shows this to be false.

Looks pretty level to me. Besides, the -9 seems to fly more nose down than the short wing RV's. At that altitude, it is still nose down, just not as much as at 8,500'
 
The point is that those speeds are getting near the edge for the RV9. ... [/url]

Yep, they are close but not over.

It is up to the pilot to manage the speed. Even an O-235 powered -9(A) can hit those numbers going downhill.
 
AIRSPeed

Vno is indicated and Vne is true. Interesting huh?

Somewhere north of 8500ft, Indicated becomes secondary to True AIRSPeed.
 
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Looks pretty level to me. Besides, the -9 seems to fly more nose down than the short wing RV's. At that altitude, it is still nose down, just not as much as at 8,500'

The PFD does not show any kind of "nose down" indication. And, "Looks pretty level to me" would seem to contradict "it is still nose down".
 
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Regarding smooth air......

The two worst turbulence events I have had in my flying career (both while flying RV's at high speed cruise and bad enough to cause major head impact on the canopy even with very tight belts) were surely encounters with wake turbulence, since the air had been glassy smooth for the previous 1/2 hr and it was for the half hour after the event.
 
The two worst turbulence events I have had in my flying career (both while flying RV's at high speed cruise and bad enough to cause major head impact on the canopy even with very tight belts) were surely encounters with wake turbulence, since the air had been glassy smooth for the previous 1/2 hr and it was for the half hour after the event.

Ditto for me. Even bruised my shins from hitting the bottom of the panel.
 
That might be because "level flight" is nose down and the EFIS is so calibrated.

Likely true with some AHRS but the Dynon AD-AHRS must be mounted within 1 degree of all three aircraft axes. (Page 5-9 of the install manual).
 
The two worst turbulence events I have had in my flying career (both while flying RV's at high speed cruise and bad enough to cause major head impact on the canopy even with very tight belts) were surely encounters with wake turbulence, since the air had been glassy smooth for the previous 1/2 hr and it was for the half hour after the event.

....Actually now that you said this, it reminded me of one we experienced in one of our RV-9As, going through the Banning pass in So Cal. It was violent enough to break the canopy, and the back of it lifted up, loosing our headsets and some baggage out the opening. My G-Meter was pegged at +6 & -4.2 and must say this was the hardest hit I have ever had. When my head hit the top it almost knocked me out, causing me to loose control and 3,500 ft of altitude prior to regaining control. This took the fun out of flying for a time but the plane survived it remarkably well. A testament to how good these little planes are. ...:eek:
 
...... then I woke up. 😁

In reality, ive never hit clear-air non-forecasted severe turbulence before but it?s one thing that does keep me up at night. Those are the times you are glad you are operating with lots of margins. By the way, the -9 is better. 😂

The 9 may be better at some things. The amount of margin is not one of them. Not this post, but some of the posts in this thread seem to ignore reality and are trying to operate very near the edge.


Hope the man who over stressed his 9 to 6G had it checked by a competent engineer.
 
The 9 may be better at some things. The amount of margin is not one of them. Not this post, but some of the posts in this thread seem to ignore reality and are trying to operate very near the edge.


Hope the man who over stressed his 9 to 6G had it checked by a competent engineer.

...Yes!
That would be me. Thanks, Allan..:rolleyes:
 
The RV9 may not be the fastest model but I did outrun a M20C Mooney with 180 hp retractable gear and a cs prop with my fixed gear 150 hp and a fp prop, one person in each plane.
 
And then you can adjust it. Same as a steam gauge.

If, by "adjust it", you mean modifying the AD-AHRS mount, that would be true. There is no adjustment otherwise. Why someone would want or need to adjust this in an EFIS is the question in my mind.
 
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Question for those that hit the canopy, do you have a 4 or 5 point harness, and how close were you to the canopy, almost 14 mod?
 
Question for those that hit the canopy, do you have a 4 or 5 point harness, and how close were you to the canopy, almost 14 mod?

....When we had our experience, we only had four points, I ordered five points the very next day! I now absolutely refuse to let anyone in my airplane unfasten their belts, in flight in my RV after this incident. Had one or both of us not been fastened in, we no doubt would have been ejected for sure. The seat mod does provide about three more inches of head room, but in the case of violent turbulence, I really don't believe it would make much difference. The reason is, the attach points for the shoulder harnesses and seat belts, are really designed for a crash or forward impact, and not to help hold you down. Its not improper design, but more a case of the using the strongest points for attachment available. There is a way to remedy this, and if there is an adequate amount of interest from others, we can create a kit that will address, and eliminate the issue. If this is of interest to you, please send send a PM so we know and can look at it more. Thanks, Allan..:D
 
If, by "adjust it", you mean modifying the AD-AHRS mount, that would be true. There is no adjustment otherwise. Why someone would want or need to adjust this in an EFIS is the question in my mind.

It helps if you read the manual:

Dynon SkyView Manual said:
How to Enter the In Flight Setup Menu
When airspeed is greater than zero or groundspeed is greater than 15 knots, simultaneously pressing and holding buttons 7 and 8 when on the Main Menu will open the In Flight Setup Menu. This menu gives users access to SkyView system tools which may be useful during flight such as the Flight Angle Pitch Adjust Page and the Angle of Attack Calibration Wizard.
You may also access the Setup Menu from the In Flight Setup Menu by using the ENTER FULL SCREEN SETUP MENU? option.
 
I guess I need to get busy!!!

...Wow! Its only been about 4 hours since my last post in this thread, and
already I have nine e-mails expressing interest in the belt and harness kit or
mod I talked about. I am saving all the addresses so I can contact all the interested
parties, please keep them coming.
Thanks for your responses. Allan...:D:D
 
...Wow! Its only been about 4 hours since my last post in this thread, and
already I have nine e-mails expressing interest in the belt and harness kit or
mod I talked about. I am saving all the addresses so I can contact all the interested
parties, please keep them coming.
Thanks for your responses. Allan...:D:D

I have a lot of your great products, care to share your idea, :rolleyes: got us wondering now, are the anchor point geometries inadequate?
 
I have a lot of your great products, care to share your idea, :rolleyes: got us wondering now, are the anchor point geometries inadequate?

...Absolutely not! They are exactly where they should be to do the job they were designed to do.
What I have in mind will have them doing double duty if you will, without effecting their original
design in any way. I will post something soon with more information. Thanks, Allan..:D
 
I certainly understand that. I am trying to decide between the 7,9, and 14. I am leaning towards the 14, but as of yet, still undecided. It is a large commitment of time and money and I would like to be confident in my decision. And also my wife says I suffer from analysis paralysis, and yep, I believe she is right!
 
Question for those that hit the canopy, do you have a 4 or 5 point harness, and how close were you to the canopy, almost 14 mod?

In my case both instances were with a 4 point harness. That is just one of the reasons I am a big advocate of 5 point harnesses in RV's

Adding the 5th point and adjusting its belt properly pretty much eliminates any vertical movement, so short of doing neg. G aerobatics, I don't see why anyone would need to add modifications to the belt system.

BTW, no one should be doing neg G without a secondary belt anyway.
 
I certainly understand that. I am trying to decide between the 7,9, and 14. I am leaning towards the 14, but as of yet, still undecided. It is a large commitment of time and money and I would like to be confident in my decision. And also my wife says I suffer from analysis paralysis, and yep, I believe she is right!

You better get started tomorrow, that illness will add at least 4 years to your build! :D
 
In my case both instances were with a 4 point harness. That is just one of the reasons I am a big advocate of 5 point harnesses in RV's

Adding the 5th point and adjusting its belt properly pretty much eliminates any vertical movement, so short of doing neg. G aerobatics, I don't see why anyone would need to add modifications to the belt system.

BTW, no one should be doing neg G without a secondary belt anyway.

....The -4 Gs we did wasn't by choice, and even with the 5 point a regulation size man will still hit his head in a hard downdraft at speed. I tried it with the lap belt so tight it was extremely uncomfortable (Couldn't fly like that) and you can still hit the canopy. I will show this in a video demonstration shortly.
Thank, Allan..:D
 
Edited

In my case both instances were with a 4 point harness. That is just one of the reasons I am a big advocate of 5 point harnesses in RV's

Adding the 5th point and adjusting its belt properly pretty much eliminates any vertical movement, so short of doing neg. G aerobatics, I don't see why anyone would need to add modifications to the belt system.

BTW, no one should be doing neg G aerobaticswithout a secondary belt anyway.

Edited above for clarity. I misassumed that what I meant was obvious.
 
I certainly understand that. I am trying to decide between the 7,9, and 14. I am leaning towards the 14, but as of yet, still undecided. It is a large commitment of time and money and I would like to be confident in my decision. And also my wife says I suffer from analysis paralysis, and yep, I believe she is right!

you are doing the right thing to take some time to settle on the model. whatever the choice, if you make the right decision it will keep you happy for the long run.
 
In the RV7 vs RV9 debate, have you considered the RV14? It perhaps gives you the best of both worlds?

The good thing is you can't go wrong with either of the three.

Building the -7 and -9 are pretty much the same. The -9 has a few more rivets to drive simply because it has a longer wing, which may add about an hour additional to the total build time. Other than that, the effort is the same.

The quality of the -14 kit is just stunning. So many more of the parts are pre-made. Go look at the difference in build time in hours and years between the 7/9 and the 14. It is definitely in favor of the -14.

Whichever you select, you will be convinced it is the best of the litter.
 
Staring at the numbers, it's hard to tell what really matters. For instance, baggage. Van's lists the RV9 baggage capacity at 75# and the RV7 at 100#. How can that be, if they have the same fuselage? Perhaps it's a cg thing, assuming a smaller engine in the -9?
 
Staring at the numbers, it's hard to tell what really matters. For instance, baggage. Van's lists the RV9 baggage capacity at 75# and the RV7 at 100#. How can that be, if they have the same fuselage? Perhaps it's a cg thing, assuming a smaller engine in the -9?

That's been a point of contention for so time. My builder manual lists 100 lbs and my CG allows for it.

I'm not sure when or why it was changed to 75 pounds. Scott?
 
Staring at the numbers, it's hard to tell what really matters. For instance, baggage. Van's lists the RV9 baggage capacity at 75# and the RV7 at 100#. How can that be, if they have the same fuselage? Perhaps it's a cg thing, assuming a smaller engine in the -9?
100# baggage limit in my RV9A with 1800# gross. CG within Van's specified limits. No realistic way to exceed the CG fore or aft.
 
100# baggage limit in my RV9A with 1800# gross. CG within Van's specified limits. No realistic way to exceed the CG fore or aft.

Same here. Even after painting, which moved the CG aft more, I can't get out of CG range unless the pilot (me) weighs about 40 pounds and I'm on empty fuel load (with full 100 pounds of baggage).
 
Staring at the numbers, it's hard to tell what really matters. For instance, baggage. Van's lists the RV9 baggage capacity at 75# and the RV7 at 100#. How can that be, if they have the same fuselage? Perhaps it's a cg thing, assuming a smaller engine in the -9?
It is simply a c.g. thing. Been confirmed through vans multiple times and has been documented in archives here on VAF. My cg with 0320 Catto prop and 4# crush late allows 100# in all configurations.
 
I learned about the unsuspecting violent turbulence while flying my solo cross country in a 172 earning my PPL long ago. Beautiful day , nice and smooth ,then almost got my neck broke. Luckily stayed conscious or I wouldn't be here. Going to put 5 point in my 6 when I pull it down to put my autopilot in. Should have done that long ago. OH , almost forgot....I would just buy a really clean 6. (with a 7 cowl) Wouldn't trade mine for any of them
 
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