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RV-7/7A In-Flight Breakup Accident Information

RV8JD

Well Known Member
There was some interest in a previous thread regarding the status of the investigations into the RV-7/7A in-flight breakup accidents that have occurred.

I put together the attached spreadsheet documenting the accidents I am aware of. The spreadsheet has embedded links to the respective national safety board's investigation reports, links to the dockets where available, and links to some references.

I plan to update this spreadsheet as necessary. If there are any accidents I missed, please let me know.

Clicking on the image below will take you to the spreadsheet.



Fly safe!
 
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What are you finding to be a common link? Is it the ripper rudder coming apart from possible over speeds?
 
"Aircraft pitch is approximately 30° nose-down, wings almost level. The
IAS is recorded at 244kts"

ZK DVS....it appears commonality among some accidents is overspeed. slippery aircraft flying close to VNE pointing downwards not a good mix. I flew a lancair many years ago and came to the conclusion it was awesome to roll and a lawn dart pointing downhill...its ok...but not if you screw it up. I went over VNE pulling out and eased off...luckily the surfaces did not flutter. Id like to see the rudder have a 50% margin on the speed before breakup...maybe 300 knots but perhaps thats unrealistic.

I do wonder if the "8" rudder is better in this respect being a folded trailing edge? seeing these rudders fold in the wind is a little worrying.

In this case rudder flutter caused the vertical stab to separate and one wonders if the surface was balanced well....

quote..."Van’s Aircraft has conducted stick raps and rudder pedal kicks testing to 220kts, 8 with no indication of flutter up to this airspeed. Flight at any airspeed over Vne, however, exposes the aircraft to the possibility of flutter"

I tend to think that there is somewhat of a variance in what might be experienced between different aircraft and balance of the flight controls should be of paramount importance especially after painting. You simply cannot take flutter with a grain of salt...it destroys aircraft.

So in that case..no doubt vans has done extensive testing and in the normal envelope with balanced controls we have nothing to worry about...but overspeed or overload and add flutter.....mmmm.....poor buggers.

Its a timely reminder to do two things...
1. balance your controls
2. don't fly outside the manoeuvring speeds or g loading. if you do...carefully recover....
 
I wonder how much difference builder to builder variations in the training edge make?

It would be interesting to compare differences in the stiffness of rudders on different aircraft. It might not require much shear movement in the trailing edge before balancing becomes ineffective because the top and bottom flutter independently.

A folded trailing edge seems like it would be much stiffer.
 
A folded trailing edge seems like it would be much stiffer.

Remember that folded rudders also tend to have a dab of RTV or proseal at the end of each stiffener to help prevent skin cracking. That will tie skin and stiffeners all together making a much more robust trailing edge.
 
I have the full report on C-GNDY from the TSB. In addition to the overspeed in flight (also over 240 kt if I recall) the conclusion was that the rudder was severely unbalanced. It had been inspected in an unpainted condition, and afterwards it was painted and that included some significant (up to 1/8" thick) filler used smooth the rudder and elevator surfaces. There was no evidence that the surfaces were re-balanced after the paint job.

So in addition to keeping speeds under Vne, keep your control surfaces balanced.
 
You can't blame structural failures on the airframe when it's taken over Vne and/or people are making massive control inputs at way over Va.

Step outside any of the limits and you're on your own as several pilots have sadly discovered here. Flutter and overstress are not things you can ignore and remain part of this world for long.
 
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Are builders actually balancing the counterbalanced rudders?
Thought Vans said installed the kit provided lead and that was enough on the rudder...........
Wondering now..
My original -6 rudder wasn't balanced at all.
 
Balance rudder

Are builders actually balancing the counterbalanced rudders?
Thought Vans said installed the kit provided lead and that was enough on the rudder...........
Wondering now..
My original -6 rudder wasn't balanced at all.

Manual doesn't mention balancing the rudder. Unless I haven't gotten that far. If memory serves, it's fairly aft heavy even with the weight. I would think it would take a bit of lead to get it balanced.
 
A Must Read

For anyone with limited aerobatic experience planning aerobatics in an RV, Van's An Aerobatic Epistle is a must read. That also took me to a lengthy article by Van and others that was submitted for publication in Sport Aviation. I don't know if it was ever published. "Aviation Courtesy"
The difference between the aerobatic RV's when compared to many other aerobatic aircraft is the wider range between stall and Vne, Epistle details how easy it is to impose a load of 20 G's on an RV by yanking on the stick at or near Vne.
 
Poem

Aviation Courtesy starts out with a rather macabre poem about "Ace". If anyone remembers this being in Sport Aviation I would like to know.
 
For anyone with limited aerobatic experience planning aerobatics in an RV, Van's An Aerobatic Epistle is a must read. That also took me to a lengthy article by Van and others that was submitted for publication in Sport Aviation. I don't know if it was ever published. "Aviation Courtesy"
The difference between the aerobatic RV's when compared to many other aerobatic aircraft is the wider range between stall and Vne, Epistle details how easy it is to impose a load of 20 G's on an RV by yanking on the stick at or near Vne.

Links to several articles on RV aerobatics:

An article by Van himself, "An Aerobatic Epistle":



Another article by Van himself on competition aerobatics, "IAC Aerobatics in RVs". It includes a good addendum on preparing your RV for aerobatics by Ron Schreck:



An article by Budd Davisson:



And note the "Aerobatics" section on Van's website:

 
For anyone with limited aerobatic experience planning aerobatics in an RV, Van's An Aerobatic Epistle is a must read. That also took me to a lengthy article by Van and others that was submitted for publication in Sport Aviation. I don't know if it was ever published. "Aviation Courtesy"
The difference between the aerobatic RV's when compared to many other aerobatic aircraft is the wider range between stall and Vne, Epistle details how easy it is to impose a load of 20 G's on an RV by yanking on the stick at or near Vne.

I tool the liberty of stealing the excellent "Aviation Courtesy" article and reposting it on my website:

http://www.rv8.ch/aviation-courtesy/
 
There was a post a while ago, possibly referring to a Kitplanes article, about the most common cause of RV-4 wings parting company with the airplane. As I remember, it was pilots newly acquiring an RV-4, not builders, that would execute a fast low pass with a zooming pull-up. Easy to overstress any airplane. The RV series is very responsive without being twitchy but even SMALL stick inputs can results in LARGE changes in attitude. Pull the stick back half an inch at cruise and see how fast you are suddenly at another altitude.

Ya'll be careful out there now.....
 
There was a post a while ago, possibly referring to a Kitplanes article, about the most common cause of RV-4 wings parting company with the airplane. As I remember, it was pilots newly acquiring an RV-4, not builders, that would execute a fast low pass with a zooming pull-up. Easy to overstress any airplane. The RV series is very responsive without being twitchy but even SMALL stick inputs can results in LARGE changes in attitude. Pull the stick back half an inch at cruise and see how fast you are suddenly at another altitude.

Ya'll be careful out there now.....

The RV-7/7As are not coming apart in-flight because of wing failures.
 
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I believe the RV-7/7A is safe if it is operated strictly within Van’s operating envelope (airspeed, weight, and load factor limits), the rudder is properly balanced, and the jam nuts on the control surface hinges are always tight.

The problem appears to be that there are small rudder strength margins and small fin/rudder flutter margins outside that envelope when equipped with the -9/-7 rudder. Note that RV-8s are not coming apart in-flight with the same regularity and for the same reason that RV-7s are. And I don't think RV-8 pilots are any better or more careful than RV-7 pilots.

Based on the in-depth investigations of two RV-7s coming apart in-flight (by the Canadian and New Zealand safety authorities) and evidence of the others that have come apart in-flight, if I had an RV-7/7A it would have an RV-8 rudder on it instead of the RV-9 rudder that came with the kits since mid-2002. Note that the -9 rudder was designed for an airplane that has a Vne of 210 MPH, whereas the -7 has a Vne of 230 MPH. Now, of course, those speeds are designated as TAS values.

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.​

Part of the problem (but I don't believe it's the whole problem) may be that Van's has never issued a Service Bulletin or Service Letter for the older RV models (including the -7s) stating that Van's changed the definition of Vne from IAS to TAS. They did put out an SL for the RV-14, and they put out a POH revision for the RV-12s, but nothing for the older RVs. It's disappointing that Van's has not issued an SB or SL addressing their change of that critical safety-of-flight information. Many RV pilots are unaware that Vne is now in terms of TAS, instead of IAS. At higher altitudes RV pilots may operate above Vne without realizing it.

Van's did publish this article, "Flying High and Fast", on high horsepower and the concern about IAS vs TAS, flutter, and operating at higher altitudes. But it is not an acceptable substitute for an SB or SL for each model stating the new definition of Vne is in terms of TAS, since an SB or SL would reach a much wider audience of pilots and builders.

It does seem that more and more folks are putting -8 rudders on their -7s, and that’s a good thing, IMO.
 
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I'd submit that 7s are not failing at all if built properly and flown within the prescribed limits.

Other RV types have had stab failures from coarse elevator input and wing failures too as I recall doing high speed stuff.

From a similar 2012 thread - "my suggestion would be to fly the plane within it's design limits- thousands of hours of "field testing" would suggest that the designs are pretty safe if you do that.
Terry, CFI
RV9A N323TP"
 
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It does seem that more and more folks are putting -8 rudders on their -7s, and that’s a good thing, IMO.

If I had a -7, that’s what I would do.. especially because that -9 rudder feels just too big and stiff. Those folded trailing edges feel sweeter. Isn’t the vertical different too? Like the -7 crowd would need to change the stab and the rudder together? I thought the -8 balance tab was smaller and doesn’t fit the -7 stab..
 
Part of the problem (but I don't believe it's the whole problem) may be that Van's has never issued a Service Bulletin or Service Letter for the older RV models (including the -7s) stating that Van's changed the definition of Vne from IAS to TAS. They did put out an SL for the RV-14, and they put out a POH revision for the RV-12s, but nothing for the older RVs. It's disappointing that Van's has not issued an SB or SL addressing their change of that critical safety-of-flight information. Many RV pilots are unaware that Vne is now in terms of TAS…

+1. Since this is so different from the way normal (part 23) aircraft limitations are expressed, I too am disappointed in the way this information has (or has not) been disseminated. IMHO it’s a black mark for an otherwise excellent company.
 
The RV 7 rudder is originally designed for the rv9 which has a significantly lower maneuvering and VNE speeds...
 
Clarification

If I had a -7, that’s what I would do.. especially because that -9 rudder feels just too big and stiff. Those folded trailing edges feel sweeter. Isn’t the vertical different too? Like the -7 crowd would need to change the stab and the rudder together? I thought the -8 balance tab was smaller and doesn’t fit the -7 stab..

The original 7 release came with the same-as-the-8 rudder also the same as counterweighted 6 rudder with .020 skin. Let's call it the 7Short. The vertical on the 7 does not change with the rudder. I have both, the 6-8-7short hanging in my basement, 7tall/9 on the plane.

Vans shipped free tall (aka -9) rudders for early 7 serial numbers after they did spin testing and a test pilot did not like the recovery response.

A number of the inflight failures, broke the rudder, broke the forward VS spar, and folded down the HS spar - -maybe in that order the first pieces to hit the ground were the upper section of rudder w/counterweight.

These are all facts listed in reports.

What I would like to know: How much flutter margin (if that is the real issue) changes with the rudder change on a 7? I get vertigo just reading about flutter.
 
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Margins for the zipper rudder

Every design if operated within the design margin is safe. HOWEVER, some designs have narrower margins. The unzipped rudder seems to have a rather unpleasant consequence if the design is exceeded.

I removed the -7 /-9 zipper rudder from my -9 and installed a balanced -8 rudder. It was easy peasey. Probably an overkill for a non-aerobatic -9.
 
Aftermarket RV7 Folded Rudder?

What if some people with the equipment can build the folded rudder like the RV8 but with the larger size for the RV7 and sell them? I am sure some of the RV7 owners are willing purchase a stronger design that is less prone to zipping.
 
What if some people with the equipment can build the folded rudder like the RV8 but with the larger size for the RV7 and sell them? I am sure some of the RV7 owners are willing purchase a stronger design that is less prone to zipping.

I bet some would if it was lighter (like the 8), carbon fiber, stronger/stiffer in torsion and bending. Then counterweight factor could be better. Reno/racers might want it.

Can this be done in carbon?

Edit: Why lighter and stiffer? Nice discussion of flutter.
 
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Fly within the design limits of the airplane...

......about the most common cause of RV-4 wings parting company with the airplane. As I remember, it was pilots newly acquiring an RV-4, not builders, that would execute a fast low pass with a zooming pull-up.

The RV-7/7As are not coming apart in-flight because of wing failures.

My post was referencing exceeding the design limits of any airplane, but sited the cause of some -4 incidents. I did not infer that the -7 had a wing failure, just that it was a common cause of RV-4 wing failures as this discussion was referring to exceeding design limits during flight, a possible cause. At this juncture, we do not know the cause of the most recent referred to incident.
 
Every design if operated within the design margin is safe. HOWEVER, some designs have narrower margins. The unzipped rudder seems to have a rather unpleasant consequence if the design is exceeded.

It seems like once you go past the margins and unzip the rudder, the rest of airplane or at least the tail is not far behind it.

Does any one know if it would be possible to land or fly an RV with only the rudder unzipped/departed, and the rest of the tail intact? Otherwise I would think having a “stronger” -8 rudder just moves the failure to somewhere else on the tail, and the (tragic) results are the same once you go past the point of no return.
 
RV4 structural failure

There was a post a while ago, possibly referring to a Kitplanes article, about the most common cause of RV-4 wings parting company with the airplane. As I remember, it was pilots newly acquiring an RV-4, not builders, that would execute a fast low pass with a zooming pull-up. Easy to overstress any airplane. The RV series is very responsive without being twitchy but even SMALL stick inputs can results in LARGE changes in attitude. Pull the stick back half an inch at cruise and see how fast you are suddenly at another altitude.

Ya'll be careful out there now.....

I would be VERY interested in that article if you can .....in all my investigations,I could only find one structural failure of an RV4 ( in Australia) and after reading the report and looking at pictures of the wreckage ,it couldn't be blamed on the design ( operating outside the design limits ) and the failure was not the wing
 
What if some people with the equipment can build the folded rudder like the RV8 but with the larger size for the RV7 and sell them? I am sure some of the RV7 owners are willing purchase a stronger design that is less prone to zipping.

I bet some would if it was lighter (like the 8), carbon fiber, stronger/stiffer in torsion and bending. Then counterweight factor could be better. Reno/racers might want it.

Can this be done in carbon?

I don’t think adding a new untested rudders into the mix without it going through Vans engineering would satisfy my worries if I had a -7. Changing stiffness and mass will change the aeroelastic axis and with out proper engineering may actually reduce flutter margin.
 
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Education Please

I don’t think adding a new untested rudders into the mix without it going through Vans engineering would satisfy my worries if I had a -7. Changing stiffness and mass will change the aeroelastic axis and with out proper engineering may actually reduce flutter margin.

Could you help the flutter-ignorant engineers with some understanding please. I thought that decreasing mass, moment, and increasing stiffness of a flight control would always extend the flutter speed. Given fixed design otherwise.

I do understand the aft fuse, HS, VS structures are all involved the dynamics, and one time at low altitude I hit a burble at 130kts (straight and level) and the tail seemed to shake like a wet dog. Nothing like this has happened in 250 hrs since. It would make me happy if there was a full ground vibration test performed, but that is out of my control.

Edit: Here is a reference for the combination of lower mass, stiffer torsionally, and stiffer in bending.
 
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Thank you

What a great thread for a safety discussion regarding aerobatics in RV's.

I'm glad that VAF has not found reason (so far) to close or delete the thread for any presumption of speculative comments relating to a specific incident. Reader/Contributors - Please refrain from making that sort of comment on this thread.

I have been considering, with some apprehension, getting some instruction/introduction to some gentlemanly aerobatics in my recently completed 14A. This thread and some of the embedded links make good reading and provide much appreciated guideance.

EDIT > One question I have about aerobatics, and instruction in aerobatics is "Are parachutes required?". You can't or it isn't a recommended procedure to eject the canopy in-flight in an RV-14A, so what does a parachute do for you if they are required?
 
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I have been considering, with some apprehension, getting some instruction/introduction to some gentlemanly aerobatics in my recently completed 14A.
Although the RV-10 and -14 rudders still have riveted trailing edges, the internal structure is different from that in the-7/9. Stiffeners are tied to the rudder spar with shear clips, and the stiffeners themselves are much more robust - the horizontal flanges are joined to their mates on the opposite side with a rivet about halfway down the rudder chord. Also, the counterweight skin is integral to the rudder skin and not riveted on as with the -7/9.

My professional flight test work has only dealt with structures and flutter at a conversational level, but my sense is that these changes make the rudder quite a bit stiffer. Only Van's can say whether those changes were remedies for a weakness in the -7/9 rudder design, or if they were done for another reason.

ds
 
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Are builders actually balancing the counterbalanced rudders?
Thought Vans said installed the kit provided lead and that was enough on the rudder.
Posts like this worry me. The point of the counterbalance is to balance the rudder, just like the elevators.

My original -6 rudder wasn't balanced at all.
Nor is mine. But it's a different design, with different size and shape and different speed limitations on the airframe. Van did switch to a counterbalanced rudder on the -6 before they stopped selling the kit, as part of the development of the -7. A number of -6's have been upgraded to that tail, or the -8 tail, to get increased rudder authority.
 
Posts like this worry me. The point of the counterbalance is to balance the rudder, just like the elevators.

You’ve got my attention, now. To balance the rudder as per the elevators would require significantly more lead. Is the rudder’s lead there simply to bring its cg forwards “enough” for safe flight or to balance it as per the elevators? The instructions so far have not suggested that it requires to be balanced like those. Please expand, if you’re confident you know what you’re talking about - I’m keen to learn!
 
Vibration in flight...

I hit a burble at 130kts (straight and level) and the tail seemed to shake like a wet dog. Nothing like this has happened in 250 hrs since. It would make me happy if there was a full ground vibration test performed, but that is out of my control.

Bill,

I encountered a similar issue in my first -7 with the big rudder (R-901), and 3" x 1/2" wedge attached to T.E. We were heavy, aft CG but within limits, in a descent from 9500 passing 8500 at 175KTAS. Hit a slight bit of turbulence and then I could feel/hear a vibration similar to a wooden ruler held flat on a desk - being thumped and then slid over the desk --- "brrrrrrraaaaaap" (not quite the A-10 brrrrrrrp...but close :) ). Put my feet on the rudder pedals (I usually fly feet off until maneuvering) , chopped power, and the vibration ceased.

Switched to the RV-8 rudder (R-801PP), flew another 300 hours in that airplane without issue.

YMMV FWIW

B
 
So how much heavier is a 8 rudder as compared to a 7/9 rudder?

I believe the -8 is lighter, but not by much. While the -8 rudder is smaller in area compared to the -9 rudder, it uses thicker skins (.020" vs .016"). The -8 rudder has fewer parts as well (no R-916 and associated rivets, smaller Rudder bottom, shorter counterbalance skin, smaller rudder tip).
 
So how much heavier is a 8 rudder as compared to a 7/9 rudder?

The 7 Short (aka 8) rudder is smaller, lighter, and CG closer to the pivot than the 7Tall/9 rudder.


Screen Shot 2022-08-18 at 11.06.43 AM.png
Area and weights not including fiberglass. Area is from spar rivet line aft.

Thanks Brian, I have just been lazy and not installed my 8 (aka 7 Short) rudder, and will have to invest in painting it too. I did all the glass fitting but not the final ready-to-paint details. Di you find any significant changes to landings?
 
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EDIT > One question I have about aerobatics, and instruction in aerobatics is "Are parachutes required?". You can't or it isn't a recommended procedure to eject the canopy in-flight in an RV-14A, so what does a parachute do for you if they are required?

As I understand it, you are not required to have a parachute to perform aerobatics alone. You are free to kill yourself. However, if you have a passenger, you are both required to have parachutes. You aren’t supposed to kill innocent victims or, presumably, let them watch you go down with the ship, so to speak.
 
Put my feet on the rudder pedals (I usually fly feet off until maneuvering) , chopped power, and the vibration ceased.

More likely to have bad things happen with "stick free" (in this case rudder pedals free) than with "stick fixed". Control cables/tubes provide another constraint when held with control pressure.
 
...
Thanks Brian, I have just been lazy and not installed my 8 (aka 7 Short) rudder, and will have to invest in painting it too. I did all the glass fitting but not the final ready-to-paint details. Di you find any significant changes to landings?

None whatsoever; crosswind (demonstrated) to 20kts (Airport T82) at heavy weights. I tend to land a bit on the faster side however -- usually over the fence at 75kts, rounding out / flare at 65kts...
 
More likely to have bad things happen with "stick free" (in this case rudder pedals free) than with "stick fixed". Control cables/tubes provide another constraint when held with control pressure.

No argument -- I now rest the balls of my feet on the outside of the rudder pedals, takes up any slack in the cables.
 
The 7 Short (aka 8) rudder is smaller, lighter, and CG closer to the pivot than the 7Tall/9 rudder.


View attachment 29671
Area and weights not including fiberglass. Area is from spar rivet line aft.

Thanks Brian, I have just been lazy and not installed my 8 (aka 7 Short) rudder, and will have to invest in painting it too. I did all the glass fitting but not the final ready-to-paint details. Di you find any significant changes to landings?

Interesting that the 8 rudder CB weight is 1.85lbs vs the 7 rudder is 1.43lbs
 
Interesting that the 8 rudder CB weight is 1.85lbs vs the 7 rudder is 1.43lbs

Plans for the -7 big rudder (RV-9) call for the E-612-020 weight. Which according to Van's weighs in at 1.85lbs.
 

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I bet some would if it was lighter (like the 8), carbon fiber, stronger/stiffer in torsion and bending. Then counterweight factor could be better. Reno/racers might want it.

Can this be done in carbon?

Would it be as simple as producing a skin that folds at the edge rather than being riveted? How about a piece of .062 or even thinner bent to scab on over the trailing edge?
 
Plans for the -7 big rudder (RV-9) call for the E-612-020 weight. Which according to Van's weighs in at 1.85lbs.

Ok now I'm confused.
According to the Van's website for the -20 weight:
"Counterweights for optional 0.020 Skins, RV-6/6A, Early RV-7/7A"
 
Would it be as simple as producing a skin that folds at the edge rather than being riveted? How about a piece of .062 or even thinner bent to scab on over the trailing edge?

From the manufacturing perspective, a folded rudder will cost more material since less number of rudder skin can be cut from a larger sheet of raw stock because of the odd shape. For a zip leading edge, more smaller rudder skins, left and right skins are identical, can be stamped from a larger sheet, thus, more economical use of the raw stock. We all love the low prices of Vans aluminum parts.
 
edit: confirmed the 7 tall-9 has the E-614-020 (1.85#) called out.

Yes but "I think" that was for the early 7 rudder (which was the 8).
The RV8 plans call for the -20....

Update: Van's tech support (Stirling) just confirmed both rudders (7/8/9) use the same -20 weight.
 
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From the manufacturing perspective, a folded rudder will cost more material since less number of rudder skin can be cut from a larger sheet of raw stock because of the odd shape. For a zip leading edge, more smaller rudder skins, left and right skins are identical, can be stamped from a larger sheet, thus, more economical use of the raw stock. We all love the low prices of Vans aluminum parts.

I understand the reason. Shipping for all the tail kits that go out is big too. Im looking for a way to strengthen the zipper. If I took a 4" piece of .062, bent it to about 160 degrees (not sure if that is the correct bend) and then epoxy or rivet to the trailing edge? That would strengthen it considerably and maybe help with AV type wind damage too.

I flew today and on my walk around, I tried flexing the rudder like it would in the wind. It feels pretty solid, but I can see how a wind gust could weaken it and after several smacks, I could see it weakening. I imagine flutter do the same thing in seconds.
 
Comments

Things I haven't seen mentioned;
Utah airplane was in an area of possible moderate to severe turbulence.
Utah airplane was "estimated" by NTSB to be 128# over aerobatic gross weight.
The Washington airplane was never recovered from the water except for a few small pieces. Therefore the probable cause is loss of control for undetermined reasons. Although this was an experienced pilot the NTSB does not address aerobatic experience. I believe in this case it is POSSIBLE that the airplane was in a fully developed accelerated spin with full power that exceeded Va and failed the rudder which was fully deflected in excess of Va.
Apples to oranges but Jurgis Kairys in the SU26 and SU31 did accelerated spins that transitioned into snap rolls. Approximately 14 turns, at the halfway point the rotation was considerably faster than one can count. Now consider a RV pilot, relatively inexperienced in spins, inadvertently enters a spin with full power and elevator neutral. Panics and maintains the full power and full redder deflection.
 
Flutter

The Polen Special is derived form the Midget Mustang I which was designed by a Pier Engineer in the 40's. The Polen flew successfully for many years and then developed rudder flutter. The fix was a carbon fiber rudder.
Years ago I met a Harmon Rocket builder/pilot who bragged about flying at 300 indicated. It would seem that if the -7 does have a rudder problem the first thing to consider would be the construction and balance of the rocket rudder.
Again apples to oranges but since the starting point for the Harmon Rocket is RV4 parts, maybe John Harmon and other HR builders know things that would be applicable to the RV7.
 
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