SB 14-01-31; RV-6, 7, 8

[David-aviator]

Originally Posted by Snowflake

Possible new info:

I initially thought I was crack free, having pored over the photos I took of the four corners in great detail. However, I happened to open them up again and noticed something I had missed on first review... The photo below is taken with the camera in the space behind the front spar, and the lens oriented roughly towards the passenger wingtip. So you're looking at the top right stress point in the SB.

Look at the rib at the right of the photo though, specifically the bend in the flange that joins it to the back of the front spar. Right beside that top rivet, is a crack that extends down at least the width of the rivet head. It's very faint to see, but the rivet head is just above the center of the photo, the crack just to the right of it.

I wonder if this is related to the failure in the SB, and if people should check for this as well... Maybe my shear web didn't crack because this part did?

In any case, as the crack in question would be fixed if I did the SB, I'll be ordering the kit.

Rob,

It appears the shear web is not cracked, just the rib flange. Seems like that could be repaired with a doubler along the rib flange down to the second or third rivet. The SB does not address a cracked rib flange.

The front spar bend of 6? is a bucket of worms. Cracks are occurring in the vertical sheer web at or near the bend perhaps because it is not assembled perfectly or the area is under stress because the parts do not match perfectly. The notch may facilitate cracking since there is less material to carry the load through the bend.

How come late RV-8 HS-702's do not have the notch whereas early RV-7's have the notch where cracks are occurring, the data indicating more frequently than without the notch? And now the SB advises to make the notch .25" or greater if it is not present?! This seems inconsistent with the data concerning the occurrence of the problem. The SB doubler probably will prevent cracking of the vertical sheer web though the bend but why make the big notch? It did not prevent cracking from the git-go.

[JonJay]

Originally Posted by John Collier

If I find cracks...I'd prefer to build another horizontal stab...my workmanship was at its lowest on the tail. So...has anyone installed a new stab on an aircraft? The above quote about match drilling it to the fuselage has me questioning whether I should go this route. Any experience is greatly appreciated. PM is fine as I don't want to derail this thread. If I go this route...or get any good info...I'll start another thread.

Thanks!

Match drilling aluminum through aluminum with a hole already drilled to finished size is always going to be a challenge even when you have good access to the work piece. Scott's concern is very legitimate in that you will have much less than perfect access added to a tricky procedure.

While I have not replaced a HS, when I encounter this situation, I fabricate a drill bushing. For one time or very limited use, that bushing can be made from almost any material, however, steel is best. I make my own on the lathe but there are commercially available drill bushings in many OD and ID sizes.

With the bushing to protect the hole, you can drill the pilot hole accurately. Once the pilot hole has been drilled it acts like a guide.

You will need a 90 deg. drill. Without a bushing getting the 90 deg drill straight in a limited access area will be tough. The bushing insures you drill a straight hole.

[Walt]

The question of log entries came up in another tread but I thought it would be useful for folks that may not see it there.

When you notate in the logbook you should state how you complied with the SB.
Example:

C/W SB XXX dated xxxx by inspection, no cracks noted at this time. Re-inspect due at next annual inspection.
or:
C/W SB XXX dated xxxx by installation of doublers HS-XXXX and Rib Flange angles. This repair is considered terminating action.

[Walt]

Originally Posted by JonJay

Match drilling aluminum through aluminum with a hole already drilled to finished size is always going to be a challenge even when you have good access to the work piece. Scott's concern is very legitimate in that you will have much less than perfect access added to a tricky procedure.

While I have not replaced a HS, when I encounter this situation, I fabricate a drill bushing. For one time or very limited use, that bushing can be made from almost any material, however, steel is best. I make my own on the lathe but there are commercially available drill bushings in many OD and ID sizes.

With the bushing to protect the hole, you can drill the pilot hole accurately. Once the pilot hole has been drilled it acts like a guide.

You will need a 90 deg. drill. Without a bushing getting the 90 deg drill straight in a limited access area will be tough. The bushing insures you drill a straight hole.

I agree with the above, it will be very difficult to do this accurately with the limited access and back drilling with a 90 deg drill. This is the main reason I will probably do the repair vs building a new HS.

[selhardt]

Inspected mine yesterday.

Most of the time spent removing paint - had gotten clear coat in this area - really just the top and it had to be sanded slightly before I could get any traction with a Q tip and PPG reducer. Didn't sand to metal of course - just enough to get going with the Q tip.

Finally got everything to shiny aluminum and touched it up with NAPA 7220 and a Q tip when done.

RV8, 82960
IO360,
CS Wirlwind RV200
90 hrs. total
Mostly Asphalt, but grass ops too
Acro
No Notches
No Cracks

[walkman]

Originally Posted by skylor

I'm still trying to figure what hair style has to do with cracks!

Skylor

Apple speling autokerrect. Decided to leave it as is for the laffs

[Bavafa]

Originally Posted by selhardt

Inspected mine yesterday.

Most of the time spent removing paint - had gotten clear coat in this area - really just the top and it had to be sanded slightly before I could get any traction with a Q tip and PPG reducer. Didn't sand to metal of course - just enough to get going with the Q tip.

Would a dye penetrant work over this kind of paint and if so which kit works best?

All this conversation is creating enough doubt in me to go back and do the same.
I examined mine with a 2x magnifying visor (I could not get closer with stronger magnifying glass to be focused) and the pic that I took, could zoom it in for real close up. There is certainly no crack shown in the pic but I might go and remove the paint though that would not be an easy task with the clear coat and all.

[az_gila]

Originally Posted by Walt

I agree with the above, it will be very difficult to do this accurately with the limited access and back drilling with a 90 deg drill. This is the main reason I will probably do the repair vs building a new HS.

If I had to do it, I think I would fabricate a stiff metal template that referenced the rear spar to the mounting holes on the main HS spar.

The template could be easily pilot drilled with the old HS off the plane, and then used to drill the new HS while it is inverted on the workbench.

IMHO trying to backdrill the forward spar mounting holes would be a recipe for disaster - just getting the drill and your hands inside the fuselage would be difficult.

[Lars]

Originally Posted by DanH

Good question for the group: This is a small area in an awkward location tucked into a nest of separate parts. All factors considered, what is the best way to strip the paint for a really close inspection?

MEK and a whole lot of cotton swabs in my case.

[wera710]

2006 RV-8 (Slow Build)
488 TT
O-360
Hartzell CS Prop
Pavement and Grass
Light Acro
Tons of formation
No Notches
No Cracks