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  #1  
Old 01-31-2019, 06:46 PM
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mulde35d mulde35d is offline
 
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Default HS Tip Fairings 12-6

I was tracing and trimming the fiberglass for the Horizontal Stabilizer Tip Caps and came across an issue that I think is normal, but looking for confirmation.

After match drilling the tip caps in place I noticed the fairing tip extended beyond the elevator fairing and was skinnier in the middle. As you can see in the photo



For a moment I considered filling the tip with flox and sanding it back, but then realized I needed to bow the fairing in the middle which gave it the correct shape that matched the elevator fairing. As these pictures show.



My thought is to leave the wood block in while attaching the backing patch which is discussed in 12-6. I imagine once the fiberglass lays up it will hold the fairing in the correct position and I can remove the wood block.

Can someone confirm this assumption, or is their another method more appropriate? Thanks
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  #2  
Old 01-31-2019, 07:20 PM
n982sx n982sx is offline
 
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That is exactly what I did.

I used some balsa wood to get the profile right then sealed the wood all over with epoxy and epoxied it in. Then I just sanded down the exposed face of the balsa until I had the shape correct. Then covered the now exposed balsa with epoxy and micro balloons and finished off the surface.
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  #3  
Old 02-01-2019, 12:38 AM
lr172 lr172 is offline
 
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I formed a piece of rigid foam inserted at the edge to make the shape and provide support for the layup. Once cured, peel off the foam. If the foam is loose, a couple dabs of bondo will hold it in place and grinds off later.

Larry
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  #4  
Old 02-01-2019, 06:49 AM
Reflex Reflex is offline
 
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Location: Kansas
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Jon,

I went through the same thing. I also found that the elevator fairing was slightly "thicker" (top to bottom) than the HS fairing. I cut two 1/4" balsa sticks and slid them back and forth in the HS fairing until I got a match in both directions. A little dab of 5 minute epoxy held the sticks in place until I got the back of the HS fairing glued/fiberglassed in. I then removed the balsa (5 minute epoxy holds poorly) and was done.

I figured I was the only one that had this issue!

By the way...lots of fun getting that 1/8" gap "just right" eh?

Fred
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  #5  
Old 02-01-2019, 07:16 AM
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mulde35d mulde35d is offline
 
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Quote:
Originally Posted by Reflex View Post
Jon,

I figured I was the only one that had this issue!

By the way...lots of fun getting that 1/8" gap "just right" eh?

Fred
A whole lot of fun. 3 hours of put it on, mark it, take it off, sand, and repeat.
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  #6  
Old 02-01-2019, 11:51 AM
KeithB KeithB is offline
 
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I used a foam block to both spread the tip and fill the opening, with the foam extending out into the 1/8 gap. I then wrapped sand paper on the elevator tip and by swinging the tip up and down, the sand paper forms the block to perfectly match the shape of the elevator tip. Add a little backing under the paper and sand some more. Repeat until the gap is the size you desire. (Before attaching foam block, I made a V groove along the outer edge of the foam about .25 wide.) Lay up 2 layers of glass on the foam, after filling the V groove with micro. Perfect fit.
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  #7  
Old 02-02-2019, 03:03 PM
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mulde35d mulde35d is offline
 
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Default Update

After reading the other methods to tackle this problem I went to lowes and got a 2'x2'x1" piece of insulation for $6, cut it with a band saw to rough shape, and final sanded with 80 grit to the correct dimensions. Shoved it into the tip cap and it works great without any glue or adhesive. Really easy way get the right shape very quickly. I have the fiberglass patch laying up right now and will attach it tomorrow with the foam in place. Once it cures then it should be as simple as removing the foam and making the filet joint IAW the directions. Thanks for the advise on other ways to approach the issue. Greatly appreciated.

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