Mission Control, I have a problem

This is a very painful post for me. I think I have gone through a few trapdoors that I might not be able to come back through, and I am really hoping someone here can give me some advice.

In an effort to make my floors "removable", I elected to put Rivnuts in under the floors. I thought it all went well. When I had finished up all of the wiring under the floors, I figured I could put in the floors, because I could take them out later. During the process of doing that, I "spun" two of the Rivnuts. Meaning that they were spinning in their holes, so I got not get the floor screws to go in further, nor take them out.

Picture one: This screw was halfway in, so I figured I would cut the top off, so I could lift the floor over it. It would eventually be behind the side panel, so I could live with it.



Later, when the second rivnut spun, I drilled a small hole next to screw, and put in some lock tight, locking the rivnut in place. That worked, and I was able to take out the screw, then put it back in. I can put a dot of paint over the hole, so again, I could live with it. Here it is:



Since I planned from this point on not removing my "removable" floors, I riveted in the rear baggage floor, since it was under the floors. Crisis averted, or so I thought.

Then today, realization hit me, when I was reviewing future steps. The flap fairings were not yet riveted on! And since I can't remove the floors without risking spinning more rivets, I was maybe hoping I could pop rivet these.



In my despair, I looked for more holes, and found these:



As best as I can tell they are for the rear seat lap belts, which are installed and riveted (Quick build). I'm not sure why the factory didn't put these other rivets in, but they didn't. The plans (DWG 74) call for AN426AD4-4 rivets. The factory also didn't dimple them.

So I have these 10 holes (5 on each side), that need to be riveted, but I have no access from the inside without drilling out the rear baggage floor, then removing all the screws in the main floors, possibly spinning more rivets, and having a floor become completely unremovable, and unfixable.

So I'm looking for any and all advice on how to proceed (other than drinking a lot, because I don't drink).

I would love to hear if anyone has a technique for getting a screw out of a spun rivnut, with no access to the back of the rivnut. Is drilling a side hole and adding lock tight the only or best method?

Also, any advice on drilling out pop rivets in case I do need to remove that baggage floor? With a steel mandrel and aluminum edges, I don't imagine they drill out easily (which is why I used the rivnuts in the first place).

Needless to say, not a good building day for me...

Remain calm and drill on.
Drilling out pull rivets is actually quite easy.
Take a punch and drive the center mandrel further down into the rivet. Drill the head off the rivet. Drive the remainder of the rivet body through the hole.
EAA has a pretty good video demonstration of the technique.

Will it be possible to remove the bulk of the screws from your rivnuts and then be able to lift the floor enough to get a pair of pliers on the rivnut to hold it from behind?

Another possibility is to grind the head off the screw. That allows the floor to be removed and then you can work on replacing the wonky rivnut.

If you are going to stay with rivnuts I would recommend either the serrated type or the ones with a key on them. The keyed kind take a special tool for installation if memory serves. The idea of the serration or the key is to prevent the body from spinning in the hole.

I can't offer assistance with the decision to pull rivet the flap fairings or the other question. I am not that far along yet.

Hope that is helpful. I know how aggravating things like that can be.

I could be wrong, but it looks like the holes in your picture are for the -A model step.

I hate to say this, but you may have a much bigger problem. How big of a hole did you drill in that lower longeron to get the rivnut in?

Paige

I concur with Sam...

About all you can do is remove the screws. When one turns, either grab it from the back side, or grind the head off.

Drilling out the pop-rivets is not hard at all. I like to use a larger drill bit. It kind of just mills the head down until you can punch out the center.

The five holes in the bottom photo go through an extension in the horizontal leg of the lower longeron. For some reason the longeron extends down to pick up these holes. I think it may be for the step in the A model. The seat-belt anchor is above the lower longeron and not a factor. My question would be, are the holes in the longeron countersunk under the skin? I don't know how hard it would be to tell. If they are not, I would be tempted to put in universal head rivets.

Probably should call Van's...

It really helps to put some Boelube on the screws as you put them in for the first couple of times.

Any reason not to use platenuts here instead of rivnuts?

Rivnuts

This is strictly my own opinion but I would generally stay away from Rivnuts. I use nutplates on everything. Rivnuts, as you have learned, like to come loose and spin. Installing nutplates can be tricky but if you use the singled side or angle plates, you can get a nutplate in the tightest of spaces. Hard ones to rivet, I use pop rivets to secure the nutplates.
4 airplanes and no rivnuts so it can be done.......
I've worked on other airplanes that used rivnuts and had to remove them and go to nutplates since they spun out....

Floors

We back-drilled the holes for flap fairings from the fuselage with 6" and 12" long drills. As an earlier poster said, pop rivets are easy to drill out if you drive the mandrels out with a punch first. Sorry and good luck.

Holes

Hi, I am about the same place on my RV-8A and those 5 holes are for the step only on the left side see plans page 80. I am waiting for my van`s shipment of nutplates AN515 8R8`s and wiring kit so we are in the same spot.
Russ Emick,Jr

Remove the rivnuts

Remove the screws and grind off those that spin. At this stage it's probably easier to just replace the floor panels if they are simple flat sheets like the other RV's. If you replace them it makes the grinding easier...

When the floor panels are off, remove all of the rivnuts, drill the holes out to 1/4 inch (I think they are 0.240 for the rivnuts) and buy a 1/4 nutplate jig. If you get the correct jig it will have the same rivet spacing as the #8 nutplates that you should replace them with.

I too have had poor luck with rivnuts, and if I have to use them I file a small rounded notch on one side of the hole to give something for the rivnut to expand into and grip and prevent rotation.

However, nutplates are better....

Update

Ok, floors removed. One other rivnut spun, but I got it out. The back holes are for an RV-8A, so thanks for that. I don't need to pull up the rear baggage floor.

Paige - Holes are 0.24". I'm not the first (see Matronics Matt's Ruby Vixen 2). But I'm curious, do you think that weakened the strength of the longeron?

Bruce - In hindsight, no more rivnuts. But getting nut plates into some of those locations is extremely difficult. I saw others had done it, so that is what I did. It's tough sometimes building solo.

Gil - Do you happen to know the full part# for the #8 Nutplate that you are referring to? I would think the wings would be too close to the hole already there. I wouldn't mind checking out this option. Alternatively, I need to somehow key the rivenuts as they are, now that I have access.

I really appreciate the feedback!

One more thing

You might want to reconsider your earlier decision and learn to appreciate good whiskey.

cdeerinck said:

But getting nut plates into some of those locations is extremely difficult.

Click to expand...

99% of my plane has been done solo...try Clickbond fasteners (http://www.clickbond.com) if you want to mount nutplates and can't or don't want to drill the jig or can't get to the rivets. They're pricey, yes, but boy oh boy, they are easy to work with if you prep the area properly. I'd think they'd be an easy answer for removable floors.

cdeerinck said:

Alternatively, I need to somehow key the rivenuts as they are, now that I have access.

Click to expand...

Use the search on Aircraft Spruce for "keyed rivnuts". I have used a few of these without any problem - just file the required notch with a small 3 corner file.

Rivet`s

Hi, Just an after thought on your flap fairings. after My wife and I riveted them on I wish I had used pull rivets on the ones behind the bulkhead because the empty space between causes a ugly area inside after driving the rivets. I think the correct flush pull rivets would be a MK319-BS replaces AN426-3-3 1/2 and would cause less flat spots on the outside.
Are you working on a 8 or a 8A?
Russ Emick,Jr.

Russ - I'm not sure I understanding your "behind the bulkhead" reference, they are all under the longer one in the same area. Do you happen to have a picture?

I'm making an 8 ( non-Canadian )

cdeerinck said:

Paige - Holes are 0.24". I'm not the first (see Matronics Matt's Ruby Vixen 2). But I'm curious, do you think that weakened the strength of the longeron?

Click to expand...

I'm sure it did. The question is how much? Only Vans can answer that. I personally can't remember seeing anything bigger than a 3/16 hole in a 3/4" longeron. In my -8 they had us drill and tap the lower longerons for #8 screws in the forward cabin.

Paige

bulkhead

Hi, the rivets I am talking about will be below the 5 empty rivet holes in your picture above the large hole for the step. The faring will cover that large hole.The rivets in front of those 5 take normal rivets ( the ones where every other rivet hole is empty I think there are 7. hope that help`s
Russ Emick,Jr.