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-   -   Another Empenage Fairing Question (http://www.vansairforce.com/community/showthread.php?t=147687)

snoopyflys 03-16-2017 08:06 AM

Another Empenage Fairing Question
 
Hi All,

Working on fitting the empennage fairing and while it fits pretty well, I have a pucker near the leading edge on the left side.



Even after building now for these past 8 years, I'm still a little intimidated working with fiberglass. Not sure what would be the best solution other than hacking the fairing up and re-glassing to get the fairing to lay flat on the HS skin. So anyone out there have any words (pictures) of wisdom on how I can best solve this minor issue?

bret 03-16-2017 08:24 AM

Some say use heat and work it, I had no luck with that, so.......I chopped off the front off and did glass and sand, glass and sand. took a good solid month to get it right. lots and lots of sanding I did with the fiberglass stuff.

Lemmingman 03-16-2017 08:44 AM

Dan,
Can you trim the outboard edge back along the whole length? Looks like there is a lot of extra material on there. I wonder if this would eliminate the pucker, or at least make it easier to fix.

JDA_BTR 03-16-2017 08:46 AM

Would relief notches work? Then fill on the work with electrical tape protecting the aluminum?

sf3543 03-16-2017 09:49 AM

What I would do
 
I have fixed this type of issue before. What I do is remove the fairing. Put packing tape on the HS stab as a release. Cut a bunch of fiberglass strips to fit under the raised area. Wet out the strips and put them in place and cleco the fairing back in place and let everything cure. (Don't put clecos in the area being filled)
Remove and sand down to the proper thickness.
You could also use flox and epoxy instead of the glassed strips.
Set it up one evening and sand it down next day.
Good luck.

VNS 03-16-2017 07:16 PM

Remove the clecos, allow the faring to sit flat (move away from the Fuse) and re-drill to the elevator. A little heat to provide pliability to the faring may help

Robert Anglin 03-16-2017 08:02 PM

Yep it will do that.
 
You can fill or what we did with one, "on the left side also", was. Heat gun and a peace of 1X4 about 8 inches long. Heat the area between the clecos tell it gets good a soft. Then push down on the bow with the end of the board. Once you get it pliable and push it down you will have to hold it there tell it cools back down and holds shape. If you don't like it after you reshape it with heat, then fill and sand as you like. It is not a structural item. Hope this helps, Yours, R.E.A. III #80888

Scott Hersha 03-16-2017 08:04 PM

Your fairing looks pretty typical (like a piece of bacon). Doesn't look good now, but it's not hard to fix and make it so tight, you can't get a fingernail under it the entire length of the fairing - without screws. The clecoes I see in your photo are fine, but they should remain nothing but a hole to hold the fairing still while curing, that is filled later. You'll need one screw at the front on each side just forward of and slightly below the leading edge of the HS. 3 more screws each side at the very back - one one the aft HS spar flange, one on the VS aft flange, and one(or two - depending) on the longerons. You fix the 'bacon' by fiberglass cloth and flox underlayment. Here's how:

Tape some heavy duty wax paper to your HS and VS in a wide area where the fairing sits covering everything that could get touched by the resin/flox mixture. Install the fairing loosely by hand(no clecoes) and trace the outline of the fairing on the wax paper on the VS & HS, then remove the fairing. Lay wetted layers of fiberglass cloth on the wax paper along the lines drawn - on the inside of the line with just a little overlap (this part will be ground off later to give you the shape you want). Use 2-3 layers of 9 oz fiberglass tape or BID. On top of this layered cloth spread a resin/flox mixture about the consistency of peanut butter about 1/8" thick. You want it to be loose enough to flow into voids, but stiff enough to hold its shape. Then clecoe the fairing in place onto the plane. You may have to 'work' the clecoes a bit for them to slip through the glass cloth. You could put a little car wax on the clecoe to make easier to remove/clean up after the cure, but it's not necessary. Take a Popsicle stick and wipe off excess resin that has oozed out along the edge. Let it set and cure for 24 hours. Then remove the clecoes - you'll probably need to twist them a bit to get them loose before pulling them out. Pop the fairing off the empennage - you may need to use a spatula or something similar to pry it loose, but be patient - it will pop off. Remove the wax paper that has stuck to the fairing. Then you'll need some good quality sand paper and hand held belt sander or orbital sander to grind off the excess along the edge of the fairing to give it the shape you want. You'll also want to sand/grind off excess flow out on the inside of the fairing that isn't along the edge to save weight and make it lay down nicely. All this sanding takes about 10 minutes with the sanders I've mentioned and really good sand paper (available at auto paint stores). Next you'll notice the uneven 'thickness' along the previously mentioned 'bacon' edge. Use the same mechanical sander, or hand sander to take this material down - from the top - to a uniform even, thin edge thickness. You should now be able to lay the fairing on the airplane and it should sit flat and almost perfectly even and smoothly sitting on the surface - without screws. If it isn't perfect, just redo the exercise, but this time just use resin with micro (no cloth) and a little flox mixed in along the drawn line on the wax paper, clecoe the fairing in place on top of this 'scmutz' and let it cure. This layer will be a little easier to sand. You may need to do this a couple times to get an enviable tight fit, but it really doesn't take very much time. Most of the time is spent waiting for the epoxy to cure. When you have a perfect fit, fill the clecoe holes with some of your slurry mixture and sand it smooth. The clecoe holes in the skin can be just left alone - they will be covered up with the fairing. If you made the mistake of following the plans and installing the numerous, unnecessary bacon inducing pucker platenutes, - not to worry...... they can be just left alone too because the fairing will also cover up this mistake. My fairings have all been held in to place with just three screws on each side - one on the extreme front and two on the back. I'm pretty sure I could fly my plane without any screws, and the fairing would just stay in place. My fairings actually wrap around the leading edge, so that helps too.

Here's another tip - don't do it all at once. Do just one surface at a time.... horizontal, then vertical.

Hope this helps.

Kyle Boatright 03-16-2017 09:35 PM

Quote:

Originally Posted by sf3543 (Post 1158302)
I have fixed this type of issue before. What I do is remove the fairing. Put packing tape on the HS stab as a release.
Cut a bunch of fiberglass strips to fit under the raised area. Wet out the strips and put them in place and cleco the fairing back in place and let everything cure.
(Don't put clecos in the area being filled)

Remove and sand down to the proper thickness.

You could also use flox and epoxy instead of the glassed strips.

Set it up one evening and sand it down next day.

Good luck.


This is the approach I'd recommend.

Mike S 03-16-2017 11:21 PM

Quote:

Originally Posted by sf3543 (Post 1158302)
I have fixed this type of issue before. What I do is remove the fairing. Put packing tape on the HS stab as a release. Cut a bunch of fiberglass strips to fit under the raised area. Wet out the strips and put them in place and cleco the fairing back in place and let everything cure. (Don't put clecos in the area being filled)
Remove and sand down to the proper thickness.
You could also use flox and epoxy instead of the glassed strips.
Set it up one evening and sand it down next day.
Good luck.

Yep--------used flox to marry the shape to the stab, then sanded the top to the thickness I wanted.

Flox is structural strength, you do not need cloth


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