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first fiberglass attempt - lower empennage fairings

amaris

Well Known Member
Since I just took the Sportair Workshop for RV fiberglass, I thought I'd practice some before I get to the canopy so I made some lower fairings. This is my first attempt at making anyting on my own. (my wife is starting to get plenty of ideas though!)

I need to trim it to have a nicer line in the lower left corner, but it fits really well otherwise. No idea how I attach it though. There's only room for 1 platenut on the left and so it would need a few on the underside of the HS to hold it. Any other ideas?

Love to hear thoughts from some of the fiberglass experienced.


 
Probably know this already but . . . .

Unsolicited recommendation: You need to sand the contact areas (inside) of the upper fairing to allow it to mate to the surface better. Since the gray side is inside a mold, the lumpy side contacts the aluminum. Sanding will allow it to fit much much better. It is common for such molded glass parts.

On the topic: The plans remove some longeron rivets and install screws to hold the standard fairing under the HS.

Nice work, I just did this to my flying 7 before paint for a better overall fit.
 
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Thanks, I was thinking about clickbond too.

Bill, thanks. I've not done anything to the upper except cleco it in but have been wondering how I get that to lay flat where it's not.

Because of the radius of the fairing, the usual spots to screw to don't actually touch at the rivet lines. So I may have to go outboard and attach to the forward and rear spar rivet spots instead. Right now that's only 3 attach points but I'd like to get a few more if I can. Possibly the clickbond in the skin will be needed.
 
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I?ve done this type fairing on two of the three RV?s I?ve built. I attached my lower fiberglass fairing with a epoxy. Drill a few #40 holes for clecoes to hold in place while the epoxy/flox cures, and then fill the clecoe holes. Sand the edges smooth, a little epoxy micro, sand, and you?re done. It?s quick, easy, and looks good for when you?re on your back under your airplane.

?But what if I need to remove my HS.?

In the highly unlikely event you have to remove your HS, get out your trusty dremel with a cut off wheel and make the cut. When you put it back on, you just have to glass over that skinny line you cut. Never had to do that.
 
Proseal

My lowers on my -4 are bonded on with Proseal and a couple soft rivets. Likely, you will never need to remove them. The Proseal makes a nice sealed,paintable joint. 10 years of flying, no warpage, cracks or defects.
 
I've not done anything to the upper except cleco it in but have been wondering how I get that to lay flat where it's not.

Because of the radius of the fairing, the usual spots to screw to don't actually touch at the rivet lines. So I may have to go outboard and attach to the forward and rear spar rivet spots instead. Right now that's only 3 attach points but I'd like to get a few more if I can. Possibly the clickbond in the skin will be needed.

Remove any high spots on the underside of the pre-made upper fairing, just as Bill said. When well fitted, close any remaining edge gaps to zero with a liquid shim. Roughen the underside of the flanges with 80 grit. Tape the metal surfaces with a neat strip of packing tape. Mix epoxy with cabosil to the consistency of toothpaste. Apply a bead along the underside of the fairing flanges, screw it to the airframe, and allow it to cure. After cure, sand the edges to their final contour, a nice half-round.

Look close at the edge where the fairing meets the horizontal stabilizer. See the narrow band of cured shim material?

Emp%20Fairing%20Pinholes.JPG


A similar dot of liquid shim can be used to make a solid base under each screw location, so tightening the screw doesn't deform the surface.

Your new scratch-built lower fairing is a nice part...my compliments. Bill E's proseal glue-on suggestion is a good one. Mine is attached with three screws per side, tapped into the longeron. Whatever works.

I know most upper fairings are attached with a whole lot of screws through the VS and HS skins, but it's not really necessary. Build a "hook" at the leading edge, and it locks into place using just two screws in shear, one on each side. At the rear, I use just two screws per side.

Emp%20Fairing%20Primed.JPG


I like the screwless look. Be aware that no long fairing will fit perfectly at all temperatures; epoxy glass has a CTE about 2/3 that of aluminum.

Emp%20Fairing.jpg
 
Dan, beautiful work as usual. Looks like you have a lot less inside radius on those underside fairings than I do. Were you able to screw those into the longeron and HS inboard rib rivet holes?
Thanks for the pics, big help!
 
Dan, beautiful work as usual. Looks like you have a lot less inside radius on those underside fairings than I do. Were you able to screw those into the longeron and HS inboard rib rivet holes?
Thanks for the pics, big help!

They're just screwed to the longeron. No screws in the HS, top or bottom.
 
Whoops! Allen...told you wrong.

While preflighting yesterday I glanced under the HS and realized I had two fairing screws in nutplates on the underside.

Emp%20Fairing%20Lower.jpg
 
Dan, thanks for the follow-up! Did you form those as one piece and then cut in half or did you build as 2 pieces from the get-go?
 
Whoops! Allen...told you wrong.

While preflighting yesterday I glanced under the HS and realized I had two fairing screws in nutplates on the underside.

Emp%20Fairing%20Lower.jpg

Oh, Dan, the horrors of screws into the HS!!! My confidence in you is forever shattered!

Do the non-flush screws help with longitudinal stability?:p
 
Oh, Dan, the horrors of screws into the HS!!! My confidence in you is forever shattered!

Do the non-flush screws help with longitudinal stability?:p

Yes, of course. Those of us with powerful RV's need more feathers on the arrow ;)

Kidding aside, let me make a case. I use AN526C's with nylon washers for most glass, just because it's more durable long term. Countersunk glass always seems to end up with a wallowed out knife edge in the bottom of the hole, and chipping at the surface. A straight hole is stronger, and the nylon washers make life easy for the paint.

Admittedly it would not make much difference on something like this lower strip fairing, a part not heavily loaded or removed very often. On the other hand, I have a row of screws down the long cowl seams. After 1000 hours of heat and vibration, and being in and out a zillion times, the holes and paint remain in good shape.
 
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