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Service Letter SL-00014 published - for RV-7/8/9 tailwheel airplanes

greghughespdx

Well Known Member
Advertiser
https://www.vansaircraft.com/service-information-and-revisions/sl-00014/

This service letter, SL-00014, has been published to the Van's Aircraft web site service info section. It covers the optional installation of a stiffener to the rear tailcone area of the RV-7/8/9 taildragger aircraft with the purpose of preventing potential deformation of the tailcone skin at the rear of the airplane. It does not apply to tricycle gear (A-model) aircraft.

Details are included in the service letter document.
 
stiffener dimensions...

Can we get details on F-00773A? I assume it's just a bit of angle, right? Thanks!
 
Van's has a kit for around $7. I would imagine the stiffeners should be installed with weight off the tail wheel, but does not specify.
 
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Good Timing

My fuse kit should be leaving Van's in the next week or so, and I'll just install this as I build. It looks like a piece similar to a rudder or elevator stiffener, and with AD3-3 rivets holding it on it must be quite thin angle.
 
Sl-00014

how about putting the kit part number in the sl?

tried putting SL-00014 into the list struck out.

Keith Rhea
RV7
 
Can we get details on F-00773A? I assume it's just a bit of angle, right? Thanks!

Van's has a kit for around $7. I would imagine the stiffeners should be installed with weight off the tail wheel, but does not specify.

My fuselage kit arrived two weeks ago. Parts were inventoried and now waiting to get air conditioning installed in my hangar before I start.

The rivet called out makes me think that it is 0.032" angle just like the skin.

How did you find the kit for $7? I just looked and searched finding nothing. I will order the parts on my next order to Van's. IF there were a call out of the angle size in the SB, I could more than likely make the parts in my hangar from scrap material I have on hand.
 
Any idea when this SB will be available in the store. Searched for F-00773A in the store and got no results.
I'm building my fuselage now so it would be really easy to do it now.
 
I’m guessing you could go to the “list” on Vans website, eventually, and see the the stiffener angle is made out of, but it would be helpful if someone mentioned it here. Most of us have this material on hand and can do this modification easily to comply with the SB. I’m guessing the stiffener angle is the same as the skin in that area - .032”?
 
Any idea when this SB will be available in the store. Searched for F-00773A in the store and got no results.
I'm building my fuselage now so it would be really easy to do it now.

I called Van's this afternoon., order 2 each. F-00773A Stiffeners.
 
Assuming this doesn’t apply to the RV4??? Wonder why....

We have not seen the issue manifest in the RV-4 or RV-3. Dimensioanlly they are different and tend to be a bit stiffer in that area. If one wishes they could, of course, do a similar installation on those aircraft models. Experimental aviation and all.

You can also apply this to the RV-6 in the same manner as the RV-7.

Can we get details on F-00773A? I assume it's just a bit of angle, right? Thanks!

The angle is made from .025 flat sheet aluminum, which is CNC punched and then bent to a 90 degree angle and trimmed. the person installing will also trim to fit as required. The initial piece is 5.55 inches x .942 inches. So, if you wish to fabricate your own from .025 that’s a starting point.

Per the service letter, there is no kit to order. Instead, the part numbers are instead listed in the letter.

  • You should order two each of part number F-00773A. Cost is $4.75 each. That part is now available if you search for it on our web store.
  • If you don’t have the rivets handy, order .01 pounds of AN426AD3-3, which will provide enough rivets for the install.
 
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Synopsis

Data from the field suggest that it is possible for high loads on the tailwheel to permanently deform the tailcone skin, such as when a tailwheel hits a steep bump while making a tight turn on the ground.
If I read this correctly, this happens if you are on the ground and doing a tight turn, swing the tail, and the tailwheel hits some kind of bump that applies a side load on it. Perhaps a lip on the entrance to a hangar, or a curb, or I guess even a rock. Good to know.
 
Well well, hundreds of posts mentioning this issue and I spent 10 yr building 2 years flying before paint and NOW, just a month out of the paint shop THIS??

Always something . . . :D

My real question is - does it affect the torsional rigidity of the aft fuse affecting empennage flutter modes and speed. (in a positive way)
 
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IIRC The RV-6 had the J bar stiffener go all the way to the rear bulkhead where the 7/8/9 stopped at the more forward bulkhead. Istalling this stiffener is of course a good idea but I am considering using universal rivets because I doubt it's is possible to get good crisp dimples installed in that area after the build. And perhaps they will cause less damage to the paint?? Dimpling a painted piece of metal always seemed to cause damage to the paint beyond minor touch up??
 
FWIW -- The RV-14 came with these stiffeners (F-01473A) 7+ years ago.

I wonder what happened first - the skin buckling and then the FEA, or the FEA on the new design and retro'd back (finally).
 
IIRC The RV-6 had the J bar stiffener go all the way to the rear bulkhead where the 7/8/9 stopped at the more forward bulkhead. Istalling this stiffener is of course a good idea but I am considering using universal rivets because I doubt it's is possible to get good crisp dimples installed in that area after the build. And perhaps they will cause less damage to the paint?? Dimpling a painted piece of metal always seemed to cause damage to the paint beyond minor touch up??

Would countersinking be an option with that skin thickness?
 
Would countersinking be an option with that skin thickness?

I think the sheet metal in my RV8 is 0.025 which is below the threshold for countersinking. I am using the pull rivet dimpler in this area since my fuselage is completely assembled
 
IIRC The RV-6 had the J bar stiffener go all the way to the rear bulkhead where the 7/8/9 stopped at the more forward bulkhead. Istalling this stiffener is of course a good idea but I am considering using universal rivets because I doubt it's is possible to get good crisp dimples installed in that area after the build. And perhaps they will cause less damage to the paint?? Dimpling a painted piece of metal always seemed to cause damage to the paint beyond minor touch up??

Larry, I did the mod today, the dimensions Van's has are right on. My QB -7 fuselage has the J stringers to the rear bulkhead. Bottom rivet is tough to buck, so I used a MK-319BS
 
Larry, I did the mod today, the dimensions Van's has are right on. My QB -7 fuselage has the J stringers to the rear bulkhead. Bottom rivet is tough to buck, so I used a MK-319BS

Attached are the 2 pics. One of the 6 with the J stringer going all the way to the rear bulkhead and the 7 where it stops at the more forward bulkhead
 
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I ordered my pair today. I'm fortunate that I'll be able to get them installed before final paint. It will be interesting to see what the final cost will be. Delivery snafus being pervasive through any chosen company, I opted for UPS 3 Day Delivery. The pair of part sets came to less than $10; I'm betting delivery is more than twice that... but I want them to show up without lingering in some distribution warehouse for a month so I'm hoping it's worth the price.
 
Are those ordered from Van's or did you make your own?
I ordered a set from Van's, then decided to make my own. The top 4 rivets can be bucked, and with a specialty bucking bar you could probably get the bottom one. I chose a MK319BS blind rivet for the lower fastener.
 
Retrofit of stiffener

Hi all,
I had this tailcone skin deformation occur about four years ago on my RV7. At the time I couldn't remember any specific incident that would have caused it. When I contacted Vans, having sent them some photos, they suggested that I might install a reinforcement in that area but they gave me no specific details of how to go about that. So I left things as the were and now 200 plus hours later the skin deformation hasn't evolved/ increased.
Now the question is, is it advisable to install the stiffener on an already deformed skin which will require me to "flatten" the slightly deformed skin and so possibly create stress concentrations around the surrounding rivets and structure.
Any advice would be much appreciated.
Sorry but I don't know how to attach a photo.

Mike
 
Hi all,
I had this tailcone skin deformation occur about four years ago on my RV7. At the time I couldn't remember any specific incident that would have caused it. When I contacted Vans, having sent them some photos, they suggested that I might install a reinforcement in that area but they gave me no specific details of how to go about that. So I left things as the were and now 200 plus hours later the skin deformation hasn't evolved/ increased.
Now the question is, is it advisable to install the stiffener on an already deformed skin which will require me to "flatten" the slightly deformed skin and so possibly create stress concentrations around the surrounding rivets and structure.
Any advice would be much appreciated.
Sorry but I don't know how to attach a photo.

Mike

Email me the pictures Mike and I'll post them here for you because I'm sure it'll be easier for the gurus here to tell you if they can see it. Pilot135pd at hotmail
 
Thanks for your prompt reply.
Early evening here so I'll look these photos up tomorrow and pass some on.

Thanks,
Mike
 
I have the Condor II pneumatic tailwheel from Flyboys. Our 8 does not have any sort of deformation in that area. I wonder if the pneumatic tire is effective in preventing this type of skin deformation?
 
I have the Condor II pneumatic tailwheel from Flyboys. Our 8 does not have any sort of deformation in that area. I wonder if the pneumatic tire is effective in preventing this type of skin deformation?

I have the same setup. I've always wondered if the vertical pressure back there during continuous normal landings on grass would hurt it and if STOL taildragger aircraft were reinforced there.

Haven't heard anything about that but this SB seems to me that it's not the vertical pressure but some type of twisting pressure if you hit the tire while turning the plane on the ground. That horizontal hit from the side while the plane turns seems to twist the fuse.

If I'm not reading this correctly feel free to correct, I'm not a mechanic or a builder.
 
Pop-Rivet Dimpler!

With all due respect after building several RVs have never gotten a crisp dimple with a pop rivet dimpler. And dimpling a painted surface is ugly so a universal rivet is a consideration even if it does cost several knots. :))
 
With all due respect after building several RVs have never gotten a crisp dimple with a pop rivet dimpler. And dimpling a painted surface is ugly so a universal rivet is a consideration even if it does cost several knots. :))

Not sure why. I've built more than a few airplanes. I have never used any dimpler other than pop rivet dimpler and vice grip dimpler. I have several plaques on my wall including 2 from Sun-N-Fun.

The correct pop rivet dimpler works as well if not better than any other method.
It is a little more time consuming on large skins, but to me it's worth it.
 
IIRC The RV-6 had the J bar stiffener go all the way to the rear bulkhead where the 7/8/9 stopped at the more forward bulkhead. Istalling this stiffener is of course a good idea but I am considering using universal rivets because I doubt it's is possible to get good crisp dimples installed in that area after the build. And perhaps they will cause less damage to the paint?? Dimpling a painted piece of metal always seemed to cause damage to the paint beyond minor touch up??


Use this swivel male dimple die; Aircraft Spruce part number SM10SP-4263. You'll need to drill a piece of steel to hold the female dimple die. A few light taps with the rivet gun produces a c-frame quality dimple.
 

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Hi all,
I had this tailcone skin deformation occur about four years ago on my RV7. At the time I couldn't remember any specific incident that would have caused it. When I contacted Vans, having sent them some photos, they suggested that I might install a reinforcement in that area but they gave me no specific details of how to go about that. So I left things as the were and now 200 plus hours later the skin deformation hasn't evolved/ increased.
Now the question is, is it advisable to install the stiffener on an already deformed skin which will require me to "flatten" the slightly deformed skin and so possibly create stress concentrations around the surrounding rivets and structure.
Any advice would be much appreciated.
Sorry but I don't know how to attach a photo.

Mike

I have the same question. Has anyone done this mod to an already deformed skin?
 
Am I correct in assuming that the paint would need to be removed from this are? Leaving the paint under the rivet head doesn’t seem like a good idea...
Jim
 
It would seem to me that if the tail skin is not severely deformed, then adding the stiffeners would tend to flatten out any existing "waves" in the skin and strengthen the entire area. For dimpling and riveting, the paint should be removed from the contact surfaces.
 
Hi all,
I had this tailcone skin deformation occur about four years ago on my RV7. At the time I couldn't remember any specific incident that would have caused it. When I contacted Vans, having sent them some photos, they suggested that I might install a reinforcement in that area but they gave me no specific details of how to go about that. So I left things as the were and now 200 plus hours later the skin deformation hasn't evolved/ increased.
Now the question is, is it advisable to install the stiffener on an already deformed skin which will require me to "flatten" the slightly deformed skin and so possibly create stress concentrations around the surrounding rivets and structure.
Any advice would be much appreciated.
Sorry but I don't know how to attach a photo.

Mike


Here are the pictures of what he's describing. I uploaded than all the same way correct but for some reason it's turning them sideways but you can still see the problem.
 

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Hard landings or rough field operation is only a couple of the potential factors this SB addresses.

Another major one is torsional loads on the tail spring.
Such as when the tail wheel drops in a hole or impacts a raised edge of concrete or pavement during a tight pivoting turn. The inertia induced side loads on he tail spring are higher than most people would ever imagine. This can cause a huge torsional load transfer into the lower aft tail cone through the tail spring weldment.

A skin that is no longer flat is compromised in strength and will not take as much load without buckling if another high load event occurs so adding the stiffeners would be a good idea even if there has been no change for a long period of time.

Installing the stiffeners on already deformed skins is not a problem as long as the distortion is not severe.
 
Not sure why. I've built more than a few airplanes. I have never used any dimpler other than pop rivet dimpler and vice grip dimpler. I have several plaques on my wall including 2 from Sun-N-Fun.

The correct pop rivet dimpler works as well if not better than any other method.
It is a little more time consuming on large skins, but to me it's worth it.

Please excuse the minor thread drift, for a question for Mel.

I have used a pop-rivet dimpler some. I have a lot of trouble with the pulling nails breaking, or getting jammed into the puller from forming barbs on the shank where the grip jaws pull.

You might say not to pull it so hard, but that is the pressure needed to form a reasonably good dimple.

Suggestions?
 
The key is the correct air pressure.

Please excuse the minor thread drift, for a question for Mel.
I have used a pop-rivet dimpler some. I have a lot of trouble with the pulling nails breaking, or getting jammed into the puller from forming barbs on the shank where the grip jaws pull.
You might say not to pull it so hard, but that is the pressure needed to form a reasonably good dimple.
Suggestions?

I always use a pneumatic puller to dimple. I set the pressure too low to pull a good dimple and slowly increase the pressure until I get a god dimple, then increase just a tad more. I can typically dimple a complete wing skin with one nail. You will have to "clean up" the barbs on the shank about every 20 or 30 dimples. I do this with a 1" belt sander.

I am just finishing up the fuselage on a Zenith Zodiac and still on the first nail. And many of these dimples are 5/32". Mostly .025 skins.
 
Here are the pictures of what he's describing. I uploaded than all the same way correct but for some reason it's turning them sideways but you can still see the problem.

Thanks for your help in posting the photos.

For your info, almost all of my flying is from a reasonably good grass runway.

Scott provides the answer to my question re installing the stiffener on an already deformed skin, so I'll go ahead and install it and keep you informed.

Thanks again

Mike
 
Stiffners

Many 7’s & 8’s I’ve looked at have various degrees of bulging in this area and/or working rivets on the bottom of the rear bulkheads. A little bit of extra beef in this area is a good thing. On my 9 I used aluminum angle to fill in for the missing stringer section.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 

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New guy question here. I thought I signed up for the updates from Van's. I' building and RV-7 so this service letter applies to me. I know service letters are different than service bulletins, but should Have received an official notification from Van's on this.
 
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Not sure why. I've built more than a few airplanes. I have never used any dimpler other than pop rivet dimpler and vice grip dimpler. I have several plaques on my wall including 2 from Sun-N-Fun.

The correct pop rivet dimpler works as well if not better than any other method.
It is a little more time consuming on large skins, but to me it's worth it.

Mel, you build the whole plane with pop rivet dimple dies? No DRDT 2 or C frame? Wow..that just seems like torture! Why do it that way vs drdt or whack-a-mole?
 
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Mel, you build the whole plane with pop rivet dimple dies? No DRDT 2 or C frame? Wow..that just seems like torture! Why do it that way vs drdt or whack-a-mole?

I never liked the C-frame or DRDT. I prefer the pop rivet dimpler. It works great and I've never had a double hole where you miss with the die.
 
Just looked at mine. Slight indent on right side and a slight bulge on left. Not sure if that’s just how everything lined up for the builder prior to riveting or if I have this damage the SL is about. The indention is just below the panel and the bulge, I can actually press in slightly. Planning to do the kit. What do I do with the placard on the left? Just put it back or relocate it?
 

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Just in time

This service letter came at a perfect time! I delayed the crating of my fuselage kit due to COVID and border issues. Added the parts for the service letters as I changed the delivery options to bypass the border issues.

Onto the thread drift topic of pop rivet dimplers. You must be using different nails than myself. I can't get more than 5 dimples out of a nail before it breaks!
 
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