SNX-T01: Removal of vertical stabilizer

[SP1]

Hello All,
I've been finally able to get around to inspecting my recent purchase of a partially built Sonex kit (Thanks Mike S. for scoping it out for me). I notice an issue with the vertical stabilizer mounting that makes me want to remove it. There are burrs in between the Vertical Stabilizer Attach Fitting and Horizontal Stabilizer Spar fitting.

Has anyone done a vertical stabilizer removal? Is it just following the instructions in reverse?

I noticed that for this build, the builder has replaced the nut plates on the Vertical Stabilizer Attach Fitting with castellated nuts (pic 1). Is this a common deviation?

Also, it looks like they misdrilled a hole and had to put another one right next to it (pic2). For something as critical as the Horizontal Stabilizer Spar, is this something to be concerned about?

Thanks very much for your thoughts.

[rizzz]

Hello All,
I've been finally able to get around to inspecting my recent purchase of a partially built Sonex kit (Thanks Mike S. for scoping it out for me).

Welcome & congratulations :-)

First of all,
Please note that what I write below is just my personal opinion, nothing more nothing less.
Other people's opinions might vary greatly.

Now,
I'm sorry to have to say this but from what is visible in these pictures, the previous owner was demonstrating very little attention to detail, was lacking the required patience, was certainly not following good building practices and possibly going well outside allowable tolerances...
I hope he was more careful with other parts of the project.

I notice an issue with the vertical stabilizer mounting that makes me want to remove it. There are burrs in between the Vertical Stabilizer Attach Fitting and Horizontal Stabilizer Spar fitting.

Yep that's an issue and a demonstration of the bad building practices I referred to, this is evidence that the builder did not remove the vertical stabilizer again after match drilling it to the attach angle in order to debur the holes.
He was clearly trying to take shortcuts hence my "lacking patience" comment.

Has anyone done a vertical stabilizer removal? Is it just following the instructions in reverse?

That's pretty much what you have to do. Should be fairly straight forward.

I noticed that for this build, the builder has replaced the nut plates on the Vertical Stabilizer Attach Fitting with castellated nuts (pic 1). Is this a common deviation?

This is not a common deviation I think and it will make you're life a bit more complicated trying to remove the stabilizer. I think this is another demonstration of lack of patience, he clearly did not feel like removing the horizontal stabilizer again which is required to install the nutplates.

Also, it looks like they misdrilled a hole and had to put another one right next to it (pic2). For something as critical as the Horizontal Stabilizer Spar, is this something to be concerned about?

That is very bad! Seriously!
You should check with the factory but my personal opinion is that the part will have to be remade. Unfortunately that means removing the skins from the stabilizers etc. but given what I've seen here that's not a bad thing, you will get a better idea of what this thing looks like on the inside and whether more shortcuts were taken in parts that are not visible from the outside.
Perhaps it might be allowable to re-drill the hole some distance below or to the right of where it is located now if possible, check with the factory, but having the good hole & mis-drilled hole that close together (probably even connected) would not be allowable I would think.

Remember, a vertical stabilizer is subject to considerable forces especially if you decide to do aerobatics with your Sonex (spins cetrainly). You cannot fly without it, don't risk loosing it mid-air.

Thanks very much for your thoughts.

Sorry to be the bearer of bad news but there is one more potential issue I see in your pictures which could be your biggest worry of all:
The bolt holding the horizontal stabilizer forward spar angle to the left longeron looks to be drilled very too close to the edge of the longeron. I hope this is just an illusion due to the angle the photographs were taken at but you really need to check this one is within tolerances. You risk loosing your whole tail mid-flight if it's not. (has happened to a Waiex in the past, partly blamed on design & partly blamed on poor building practices, in any case, the outcome was fatal).

Given the apparent shortuts the previous builder has taken on this part of the build I would strongly suggest you inspect the whole aircraft very very very thoroughly. Check all hole-edge distances, hole deburring (where possible), even check torque on bolts installed and/or re-install them just to make sure they were not over-torqued.

[Bryan Cotton]

+1, everything Michael said.

I screwed up one of my Waiex tail spars, and replaced it. So, it can be done. I documented it on my Cotton Waiex 191 thread, if photobucket embed fix still works.

[Marrahm]

Sam and Michael,

Just wanted to say thanks for posting this kind of stuff. it really does help those of us lurking around here who, more than occasionally, feel like we have no idea what we are doing trying to learn how to and then actually build a working airplane. A year ago, I’m pretty sure I would have looked at pics like that and said (hopefully, to myself only) - so? Now, seeing captured burrs and “lightening” holes like that makes the hair on the back of my neck stand up.

Sam, while i’m just on my wings having finished my tail, my knowledge is well below that of michael and others. But that disclaimer aside, I would consider either opening up one side of all the key surfaces or at least installing some new inspection ports and using one of those cheap inspection cameras to check out everything. Wireless Endoscope THZY 1200P HD 10m WiFi Borescope Inspection Camera 2.0 Megapixels Snake Camera for Android iOS Smartphone, iPhone, Tablet iPad Blue https://www.amazon.com/dp/B074DS6DXS/ref=cm_sw_r_cp_tai_jIkuBb2KZ3GGC

Just the piece of mind alone woudl be worth the effort to me. And based on what you’ve found already, I can’t imagine that you will not find something else fun to fix.

Just my $.02.
Good luck and be safe.
Mike

[NWade]

Sam -

I know this really isn't what you want to hear, but I am also chiming in to agree with what others on this thread are saying.

If you haven't read much on Homebuilt aircraft construction methods & standards, I highly recommend getting Ron Wanttaja's "Kit Airplane Construction". It clearly illustrates a lot of the basics, like how far apart holes need to be from each other, why you need to debur holes, how to properly install and torque bolts & washers, etc.

Many of the items I just listed in that description were obviously not done properly in the photos you have shared:

• Holes are clearly not deburred (which makes me worry that the rivet holes were not well-drilled or deburred either)
• Loose metal was not cleaned out from between the parts - so they will shift and loosen up over time, while also allowing the grit & chips to act as "sandpaper" and scrape away material on both parts - reducing the structure and possibly encouraging cracks to form.
• Sockets or wrenches were obviously used to turn the heads of some bolts (instead of keeping the bolt still and turning the nut); that's bad for getting the proper torque and it also scratches the heck out of the parts
• Some of the photos make it look like the edges of the parts were never filed/sanded smooth. Many kit parts come with a "rough" edge from where they were cut to shape, and the kit instructions explicitly state that those edges need to be smoothed out and cleaned up by the builder. Rough edges are a great place for cracks to start forming as the part vibrates with use.
• Its not clear in the photos whether washers were consistently used under every fastener

I know this is probably bitter/disappointing. My best advice is to take heart in knowing that you can rebuild any (or every) part that you need to. No single item on the Sonex is a bank-breaking item, and almost anything can be removed and replaced without a ton of work - that's the beauty of this simple airframe! Better to do it right and have confidence in your safety, than try to shave a few hours off of the project and put yourself (and any passengers or bystanders on the ground) in jeopardy.

Knuckling down and doing it right and having a great airplane at the end is well worth the effort! We'll all be here to cheer you on and offer help and support throughout the process. And if you can find an experienced Sonex builder near you (or at least an experienced set of folks at a local EAA chapter), I highly recommend getting together with them - both for knowledge and for moral support.

Take care,

--Noel
Sonex #1339

[JimP]

Thanks for that book recommendation. Just ordered a copy. I am just getting started in investigating a build and at this point Sonex is at the top of my list.

[SP1]

Thanks for all your inputs, and thanks for catching an additional potential issue. Looking from above, I did see that the longeron hole is very close to the edge. I'll call Sonex on Monday and let you know what their suggested fix is. I suspect it will be a doubler of some sort.

Thanks again for taking the time to point out a potentially fatal issue, and its implications. . Empennages are typically mandatory for flight. ;-) I'm borrowing a boroscope to see if there are other similar issues.

[rizzz]

Is that another mis-drilled hole next to the bolt visible in the last picture? That’s where the bolt actually should be, I wonder what happened here?
Definetly time to contact the factory. Let us know what they say.

[SP1]

Kerry recommends I replace the longeron or weld the holes shut. The former is the most straightforward, albeit the most labor intensive. The latter may affect the temper of the surrounding metal through annealing.

The third alternative would be a doubler. Would bridging the area with an aluminum piece as thick as the longeron be sufficient? If it's as thick, it should take the loads fine. If I sandwich the damaged longeron on both sides, then the bending axis will be the same (or is that overkill).

[NWade]

If I sandwich the damaged longeron on both sides, then the bending axis will be the same (or is that overkill).

The problem with stiffening one area with doublers like that is you concentrate the bending stresses where the "added stiffness" ends abruptly. This is why wing spars have a smooth taper, and/or are made of several layers that end at different locations so that the strength & stiffness tapers off over distance.

I think replacing the longeron is your best bet. Its not hard to cut and clean up another piece of angle, drill out the rivets for the existing one, and replace it. The longeron is your major structural member running the length of the fuselage; better to take 2-3 hours of work and make sure its done right!

Over the course of a ~1000-1500 hour build project, even 50-100 hours of extra labor to replace and refit items is just a drop in the bucket; and we're not even talking about that much labor to address the issues we've seen so far.

Good luck,

--Noel
Sonex #1339