RV-10 Horz Stab - Do I need to Tear it Open?

I bought an RV10 tail kit from 2nd owner about 9 months ago. There were some blemishes and now I am at the decision point on the Horizontal stabilizer to tear it open or leave it as is.

I have previously built and RV8, I am by no means a show-plane builder but am confident what I build is structurally sound. Reviewing the rivet workmanship on this Horizontal stabilizer has me puzzled. On the AN470 rivets, it appears the mfg head has been flattened and the shop heads are not flattened. Possibly the builder used a squeezer with the cup and flat set reversed. I know on some of the Vertical Stabalizer, it appears he used a -3 cup on the -4 rivets...

Are these rivets structurally unfit? If yes, do I dare try to take it all apart or have a new wall ornament...?







These images are typical of all the AN470 rivets. The AN426 skin rivets look acceptable.

I can't tell if if they are structural sound. I agree with your assessment in that it appears they got the dies backwards. If these were mine, I would drill them out and reset them properly. Especially if it allows you to sleep better at night.

Bob

The rivets pictured are not acceptable, and you should remake or rework the L bracket that has been damaged. The primer is blistered and peeling also. It is hard to be certain, but even those rivet heads in the last picture look cracked.

It is considered by some acceptable to use a flat die on the manufactured head of a 470 rivet under the conditions that it is not deformed more than 25% of its manufactured height, no cracks detectable, and the shop head must be formed in typical fashion with a flat die also. And the rivet meets all other applicable requirements.

If in other areas the same reverse die application has been completed and there are no cracks or adjacent damage you may try to hit the rivet again and properly set the tail. If all dimensions are good and there are no cracks you should be okay.

For most of the airframe there is much redundancy, but these rivets are different. Those nine rivets, and the nine on the other side, secure the front of the horizontal and vertical stabilizers, and you are trusting your life to those nine rivets every time you fly. So, It is a no brainer, don't accept anything less than very well done work in this important area.

I'm in the same situation as you. Three years ago, I bought my tail kit from another builder. I didn't notice until I got home with it that one or two of those rivet holes had been elongated to at least .20". What did he do? Went ahead and stuck a #4 rivet in the hole anyway. The rivet butt is basically flush with the angle and I can still see part of the hole. I also found a big dent in its leading edge at one of the cradle braces, like it had been dropped into the cradle. There may be other things wrong with the stab that I'm forgetting. I have been putting off reworking or replacing it, but the day is soon approaching where I'll need to get on it.

Redo

I'm with Andy on this one. Rework and sleep well.

Good Luck!
Michael

Everyone makes mistakes, but when an obvious error is repeated over and over...I would examine every little thing before accepting this piece.
Given the number of rivets that need reworking, you will need to be careful in removing them - or go oversize - or buy new parts.

The MIL SPEC actually allows for using a flush rivet set on the manufactured head of AN470 rivets and a cupped set to be used on the shop head side. There are specific requirements that are detailed in the document.
It is not possible just from photos to tell whether a lot of these rivets meet the requirements but they might.
Read through the document and then do some measuring. Pay particular attention to the 3.3.3 Driving procedure Section. Maybe you would only need to replace a few.

Scott, thanks for this link on Rivets, this is very helpful. I never knew it was approved to use flat die on Universal head or OK to use Universal die (one size smaller) on the driven head....I am taking the Mil Spec down to the basement to inspect some rivets......not sure I am going to like what I find. (I noticed this Mil-Spec is from US Army Missile Command, I worked on Redstone Arsenal for Missile Command for several years as an Engineering Co-Op....small world)

There seems to be plenty of edge distance if you find the holes are elongated and you have to drill to the next size up. So no reason not to drill them out and redo it. You can blend out those marks while you are at it.

BobTurner said:

Everyone makes mistakes, but when an obvious error is repeated over and over...I would examine every little thing before accepting this piece.
Given the number of rivets that need reworking, you will need to be careful in removing them - or go oversize - or buy new parts.

Click to expand...

This.

It worries me. This would cause me to put the entire thing under the microscope.

rivet repair methods

I might suggest looking at the FAA AMA chapter 4 section on rivet removal if you go that path. I find these descriptions and procedures to be well laid out and explained clearly. In Chapter 4 they give a nice description of rivet removal with the goal of retaining hole size and shape, always easier said than done. Well if all old news to you, please at least take my best wishes in the "repair" however you decide to go.