Home > VansAirForceForums

-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

Go Back   VAF Forums > Model Specific > RV-6/6A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Thread Tools Search this Thread Display Modes
Old 11-27-2020, 05:03 PM
plehrke's Avatar
plehrke plehrke is offline
Join Date: Sep 2006
Location: Defiance, MO
Posts: 1,740
Default Reskinning RV-6 Rudder to Eliminate Cracks

I built my rudder 23 years ago and has the original 0.016 skins. I had a few cracks develop years ago at the first stiffener rivet just aft of the front spar. During this Covid isolation I have decided to re-skin my rudder with the 0.020 skins.

Lots of advise I have seen over the years on stiffener attachment to keep from getting the cracks, everything from pro sealing the entire length of stiffener to just a dollop of RTV at the trailing edge.

Obviously my rudder plans/drawings are 23 years old. Question I have is what do the current plans say? Do they still just say to just rivet on the stiffeners or are they calling out some type of goo?
RV-6A - flying 14+ years, 950+ hours
Based at 1H0 (Creve Coeur)
Paid dues yearly since 2007

Last edited by plehrke : 11-27-2020 at 05:16 PM.
Reply With Quote
Old 11-27-2020, 05:05 PM
Ed_Wischmeyer's Avatar
Ed_Wischmeyer Ed_Wischmeyer is offline
Join Date: May 2005
Location: Savannah, GA
Posts: 1,378

Pretty sure that the fix is 0.020 skins... Somebody else can confirm.

RV-9A at KSAV (Savannah, GA; dual G3X Touch with autopilot, GTN650, GTX330ES, GDL52 ADSB-In)
Previously RV-4, RV-8, RV-8A, AirCam, Cessna 175
ATP CFII PhD, so I have no excuses when I screw up
Too many safety posts purged without notice...
Reply With Quote
Old 11-27-2020, 05:45 PM
Desert Rat Desert Rat is online now
Join Date: Aug 2018
Location: 50-50 Wichita KS & Scottsdale AZ
Posts: 488

It's not specific to the rudder, but on my 7 it's called out in section 5.7 of the build manual. With respect to folded trailing edges, you should stick the aft end of the skin stiffeners together with a wad of pro seal or RTV.
Terry Shortt
AGI, CFI, CFII, MEI, A&P, Janitor
RV7 Empennage & Wing done
Fuselage in process
Reply With Quote
Old 11-27-2020, 06:07 PM
Sam Buchanan's Avatar
Sam Buchanan Sam Buchanan is offline
been here awhile
Join Date: Dec 2004
Location: North Alabama
Posts: 4,370

But that doesn't address the cracks that appear at the leading edge of the rudder.

Cracks appeared in my 1999 0.016" RV-6's rudder at the spar very early in its life, propagated a short distance and haven't grown in the years since. I've consider a reskin of the rudder and if I do will incorporate some means of stabilizing the stiffeners near the leading edge.

This is challenging due to the way the rudder get closed up. I've considered actual ribs for the rudder that will be closed up with pulled rivets on one side of the rudder skin. Another thought is ribs that only extend about a 1/3 of the way back from the spar, enough to stabilize the problem area. This would also require some pulled rivets on one side.

And yet another thought is to extend the forward end of the stiffeners enough for them to be attached to the spar. This would require shims on the spar so there would be a uniform surface where the skins are riveted to the spar.

What complicates this whole thing is the possibility of moving the CG aft on an RV-6 with a fixed-pitch prop. My plane can't have the CG any further aft if baggage capacity with low fuel is to be retained. But with careful design of the mod this might not present a problem if 0.016" skin is used.

If someone comes up with a clever way to anchor the stiffeners near the spar I'm all ears.
Sam Buchanan
Fokker D.VII replica

Last edited by Sam Buchanan : 11-27-2020 at 06:15 PM.
Reply With Quote
Old 11-27-2020, 06:44 PM
azrv6's Avatar
azrv6 azrv6 is offline
Join Date: Mar 2006
Posts: 231

I developed a small crack in the aft rivet of one of the stiffeners on the 0.016 thick left elevator after only 4 hours of flight time following the first flight in May 1996. Stopped drilled it and hasn't changed in 24.5 years.

My current plan is to let it go another 24.5 years and see how it is then.
Dave Binkley
RV-6, O-360-A1A, C/S
1932 Monocoupe 110, Warner 145 (
Sedona, AZ
Reply With Quote
Old 11-27-2020, 07:22 PM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 5,742

Sorry, Phil, my 7 plans are just like your 6. Maybe Vans guys can send you a current PDF of the drawing or give the latest revision.

I remember Fast Bob Mills posted some rudder stiffening mods for his super 6, if you are interested in mods.

Lord Kelvin:
I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.
Reply With Quote
Old 11-27-2020, 09:19 PM
Martyrv6a Martyrv6a is offline
Join Date: Jan 2005
Posts: 105

I built my -6A rudder some 20 years ago using the .020” skins. I recall gluing the stiffeners their total length using 3M Scotch-Weld 2216 B/A gray epoxy adhesive. Learned this from the Matronics RV List! I also used some RTV on the trailer edges to dampen vibration. I used a greased 1/8” inch dia rod in the trailing edge to make a hole for moisture to run out when closing up. The RTV didn’t stick to the rod so it was easily removed, once the RTV was cured. Same process on the elevators.
Reply With Quote
Old 11-28-2020, 01:38 PM
Ralph Inkster Ralph Inkster is offline
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,213

If you are replacing the rudder skin, you will also probably be replacing the stiffeners too. I suggest you trim the forward end of the stiffeners different from the plans, extend them so you can apply a bit of proseal between the stiffener and the rudder spar. This will eliminate any chance of the forward cracking you see on some rudders. This will be additional to the proseal glob you apply to the rear end to connect the two stiffeners. Results is a solid rudder that will never crack.
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more
Reply With Quote
Old 11-28-2020, 05:55 PM
Dean Pichon Dean Pichon is offline
Join Date: May 2006
Posts: 543

I built a new rudder for my -4 with 0.020 skins some years ago after I developed a number of cracks. I used Pro-Seal along the full length of each stiffener. My original rudder had globs of RTV at the trailing edge in accordance with the plans at the time. Since the 0.016 skin cracked with the RTV, I did not bother to use it the second time around. This second rudder now been in service for about 800 hours with no cracks. (The first one developed cracks before 200 hours.)

I just finished building a new set of elevators, also with 0.020 skins. Again, I used Pro-Seal along the full length of each stiffener (again, without RTV).

I received new/current plans and instructions with the new tail kit (June 2019). These instructions also direct the builder to put RTV or Pro-Seal at the trailing edge.

Someone on Van's Builder Support line recommended using Pro-Seal to bond the stiffeners to the skin. I had called with an unrelated question regarding this second build and this advice was unsolicited, and had already been incorporated, but was much appreciated, nonetheless.

Good Luck,

Reply With Quote
Old 11-28-2020, 06:27 PM
Ralph Inkster Ralph Inkster is offline
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,213

I can't see how prosealing the length of the stiffener helps. I do see how skin can flex in the short unsupported area between the front spar & stiffener, and behind the stiffener to trailing edge areas, and how this will cause a crack at the last rivet on the stiffener. So I believe in supporting those unsupported areas as much as I can without adding too much weight.
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more
Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -6. The time now is 03:33 PM.

The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.