RV-14 rudder on RV-7 VS?

mburch · #1 11-01-2019, 01:20 PM

My rudder didn't manage to make the cross-country move, so I need to build a new one for my RV-7 project.

Previously I had the RV-9 style rudder with "floating stiffeners" that were not secured at the trailing edge except for a blob of RTV. The new style of rudder construction, introduced with the RV-10 I believe, has the rudder stiffeners riveted together at the trailing edge and joined at the leading edge with a "shear clip", basically turning them into built-up ribs. All else being equal, this seems like a better design, so I'd prefer to build this style of rudder for my 7 if it's possible.

The RV-14 uses this style of rudder construction, and - judging from this builder's photo of the plans - all the parts used in the RV-14 rudder have R-6xx and R-9xx part numbers. So that leads me to believe I could build an RV-14 rudder and it should just bolt on to my RV-7 vertical stab.

Anybody have any better knowledge of why this wouldn't work?

thanks,
- Matt

RV7ator · #2 11-01-2019, 06:20 PM

Matt, I have two, count 'em, two RV-7/9 rudders, one has flown. If you're somewhere near Boise, let's talk. I prefer the original 8 rudder on the 7s so these are left overs from kits I've bought 2nd hand.

John Siebold

mburch · #3 11-01-2019, 08:12 PM

Thanks John - I was actually looking forward to building a new rudder in order to incorporate a few personal touches, but I'll keep it in mind.

Bavafa · #4 11-01-2019, 09:09 PM

I did build a second rudder when I got a ding on each side of my rudder due to wind. At the time I tried to tie the stiffners together and it was going to be my own making but it was not easy so I settled for the original.

Now that I have built a 14, I really like how they tie together and if you can use the same stiffners of a 14, I believe it would make it much easier and better.

gmcjetpilot · #5 11-02-2019, 06:56 PM

Quote:

Originally Posted by mburch

My rudder didn't manage to make the cross-country move, so I need to build a new one for my RV-7 project.
thanks, - Matt

You are over thinking it. I built two RV-7 the very first early small one and the larger one. RV-7 rudder is fine in my opinion. Talk to Van's.

mburch · #6 11-02-2019, 07:10 PM

Thanks for sharing your opinion. Still hoping someone can answer the question - are the RV-14 and RV-9 (and thus RV-7) rudders the same or different?

gmcjetpilot · #7 11-03-2019, 01:40 PM

Quote:

Originally Posted by mburch

Thanks for sharing your opinion. Still hoping someone can answer the question - are the RV-14 and RV-9 (and thus RV-7) rudders the same or different?

Call Van's Aircraft Monday is my advice/suggestion. My opinion is you might not get an answer for one or more reasons..... like no one has tried it or it will not fit.... You will be the trail blazer (call Van's).

I assume you are concerned about rudder cracking at the most aft stiffener rivet? Not familiar with RV-9/-10/14 rudders with floating stiffeners or shear clips..... Sounds complicated. I can tell you on the RV-4/6 and early RV-7 rudders, the trick is to extend the stiffener flange common to rudder skin as far back as possible and rivet as far back so you can, while still being able to dimple and buck/squeeze rivet. It will never crack and no blob needed. You have to trim the upstanding angle flange to clear the opposite side of the rudder skin. Early builders left the stiffeners a full inch or more short of TE, to make riveting easier.... The skin would flex around the most aft rivet and crack. I had 900 hours on my RV-4 before I sold her, no blobs, no cracks, and I flew aerobatics, rough fields and raced it.

The "new and improved" RV-10 or RV-14 rudder may have issues yet to be discovered over time.... Cheers

Thermos · #8 11-03-2019, 03:12 PM

Matt,

I saw the same connections as you did between RV-9/10/14 rudder parts and was wondering the same thing. So when I was at the Vans factory in late June, I asked Sterling Langrell if they had thought of retrofitting the -14 rudder to the -7 and -9.

While he didn't (and couldn't, for obvious reasons) say it's ok, he also hinted that it should work. That's obviously not enough to base a decision on but it would be interesting to press Vans on the subject.

Based on other VAF threads and careful reading of several RV-7 accident reports that involve overspeed and tail separation, I don't believe Vans has the flutter margin they think they do in the larger -9 rudder - although I'm happy to be proven wrong with evidence to the contrary. Only Van's knows why the -10/14 rudder structure changed, but it does seem to be a stiffer design and I'd definitely like to know more about using it on a -7.

My $0.02...

Dave

mburch · #9 11-03-2019, 07:45 PM

Thanks Dave, very helpful info.

vernh59 · #10 11-04-2019, 04:54 AM

Quote:

Originally Posted by Thermos

Matt,

Based on other VAF threads and careful reading of several RV-7 accident reports that involve overspeed and tail separation, I don't believe Vans has the flutter margin they think they do in the larger -9 rudder - although I'm happy to be proven wrong with evidence to the contrary. Only Van's knows why the -10/14 rudder structure changed, but it does seem to be a stiffer design and I'd definitely like to know more about using it on a -7.

My $0.02...

Dave

To my knowledge, there has never been an in-flight failure of a tail component on an RV that was being flown within the designed flight envelope. The 14 rudder design may be different because the airplane is physically larger or the construction could be simplified.