Repair stabilizer tip damage

[tom.corso]

Shortly after trailering N179ES home I was moving stuff around in and around the hangar (in the dark) and I bumped the trailer into the right tip of the horizontal stabilizer. I made a gash about 2 inches deep at the deepest point and about 4 inches long. A few days later (December in an unheated hangar in WI), I fashioned a piece of foam about the right shape and put a few strips on high quality duct tape over the booboo. It is still there and the plane flies just fine but it looks pretty trashy.

What I plan to do is remove the current patch and make a new piece of foam that is as close as possible to the exact shape and cement (Probably epoxy) it in place. I will then apply a layer of fiberglass cloth overlapping the original tip by about 2 inches and use polyester resin to secure that. Then bondo, sand, repeat until it looks good enough for me and then prep and paint the stabilizer tip.

I have never done any work with rivets so I am not keen on removing and replacing the stabilizer tip. I'm probably too cheap to pay Sonex for a new part. I would first have to cough up the hundred bucks to be an official Sonex owner and then order and pay for the part. Does anyone know what a stabilizer tip costs? I don't.

Again, I humbly ask you knowledgeable folks to pass judgement on my repair plan.

Thank you

[WesRagle]

Does anyone know what a stabilizer tip costs? I don't.

https://www.sonexaircraft.com/eshop/cart.php?target=product&product_id=16485&category_id=306

[sonex1566]

Hi Tom,
You do need to be careful with what type of foam that you use with the particular resin that you use. Polyester resin will dissolve the white expanded polystyrene foam. Epoxy works fine with this stuff, but you would really need to use epoxy resin with glass cloth cover up the foam. If you've got the all the stuff sitting in your shed it works, but if you go shopping for everything that you need it will probably get close to the cost of a new one. As I am a fully qualified Aussie tight arse, I'd fix it. But I'd choose to drill the rivets out and fix it from the inside, which would save a lot of filler and a bit of weight. You can use a scrap of aluminium preferably with the plastic still on it, and clecoe it to the outside of the tip. This forms a neat mould that you can then fibre glass with ordinary polyester resin and cloth from the inside. Once it's set, the aluminium peels off easy as pie with the added bonus that the outside is usually pretty well right and is quick and easy to sand up and respray. I know it sounds like a lot of work, but I reckon that it would be neater and lighter than bogging it up from the outside and still take about the same amount of time. It will keep you out of trouble for a day while you're fixing it. Good luck.

[Scott Todd]

Check with your local EAA chapter for help. It will take an experienced person about 5 minutes to drill those rivets out and remove the tip. It will take an experienced fiberglass person an hour or so to fix it like new. Borrow a riveter and it should only take a few minutes to put it back on. This could make a great EAA hands-on meeting.

[tom.corso]

Thanks to all who have provided guidance and wisdom on my repair.

I believe I will drill out the rivets and repair the stabilizer tip. I do know enough about fiberglass work to handle that. I will form the shape on the outside of the tip, possibly with modeling clay and wax paper and apply my glass cloth and polyester resin on the inside. If it doesn't seem rigid enough I will apply a little glass matt to the inside also. A little bit of Bondo and sanding should work to hide the fact that it is a repair.

I looked through my plans and if I am reading correctly the stabilizer tips are held in place with CCP-42 rivets. The Sonex catalog says these are 1/8" diameter and .225" length and made of stainless steel. Am I likely to find these rivets at a good hardware store? So I believe a 1/8" diameter drill should be used to drill them out. I do have a fairly sturdy pop rivet tool. I don't think I have ever used anything but aluminum rivets to fix gutters and downspouts. I suppose the stainless rivets are a bit tougher. It appears that the edge of the tip is "sandwiched" between the rib and the stabilizer skin. I'm guessing I will have to reinstall the tip before I can mask and paint it to be pretty.

Comments and suggestions are always welcome.

Thanks,
Tom

[GraemeSmith]

Get a fine parallel sided punch and use it to tap through the center of the rivet to drive the mandrel back out the inside of the rivet. Then drill off the head. That way your drill tip will not wander when it hits the central mandrel.

[Bryan Cotton]

All of my fiberglass parts are riveted on with aluminum rivets.

[DCASonex]

Graeme's instructions for removing rivets is right on. but as for type of rivet to use for fiberglass, I prefer the rivets supplied by Zenair and sold by Aircraft Spruce, PN # 12-05538 for the A4 - 1/8' rivets. These are aluminum, (Plenty strong for fiberglass) but the big difference is that they have a band that bulges and then pulls up to clamp the materials where as the Sonex rivets (and most such pull rivets) budge along their full length to fill their holes and thus form their heads within the fiberglass and providing little holding power and damaging the holes in the fiberglass. For domed rivets, Zenith uses countersunk, flat head and pulls them to domed head by a recessed nose piece in the riveter for a nice tight compact appearance, The price for their riveters is high, but can make your own nose piece simply by running a standard 118 degree drill (or 120 degree countersink) bit into a standard nose piece. (Get a cheap riveter from hardware store in case you mess this up.) Run the drill bit in just deep enough that the diameter of your countersunk hole in the nose is a few thousands of an inch under the diameter of the head of the rivets.

I think the Zenair rivets "may" be Avex brand and these are also sold as such by Aircraft Spruce, and available with standard domed head domed head for stock riveter nose pieces. Note, while Zenith uses these rivets for primary structural purposes, i do not like them of that, the bulge that forms and then pulls the parts together does not expand within the holes and thus there is play in each connection. If wanting to compare to the Sonex rivets, fasten two long pieces of scrap at right angles with just two rivets about 1/2" apart, then try to move the two parts. But for fiberglass, they seem superior.

David A.

[Rynoth]

All of my fiberglass parts are riveted on with aluminum rivets.

For the tail tips, the plans do call for ss rivets. I questioned Sonex on this at one point, and they said those tips should be fastened with ss rivets as they're structural and in the airflow.

[Bryan Cotton]

All of my fiberglass parts are riveted on with aluminum rivets.

For the tail tips, the plans do call for ss rivets. I questioned Sonex on this at one point, and they said those tips should be fastened with ss rivets as they're structural and in the airflow.

Now that I think about it, I actually used #6 screws and nutplates on the tail tips. I can't remember what I used to rivet the little bulkhead in.

My wingtips are definitely aluminum rivets.