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  #1  
Old 03-15-2018, 03:53 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Location: St. Paul, MN.
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Default RV-12 side skin deburring

I'm about 350 hours into the RV-12 project and am continually amazed by the kit.

Occasionally, not often, I find some specifics in the instructions that make me say, "I wonder why that is?"

Take the Section 23 side skins (somewhere around page 7, I'd guess) in which after you drill to the longerons and remove said longerons to deburr, it says you should deburr the bottom and aft portions of the kin.

Say it with me now: "I wonder why that is?"

Why is that? Why not deburr all the edges of the skin?
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  #2  
Old 03-15-2018, 08:11 PM
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rolick22 rolick22 is offline
 
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I'm reading this as two different steps you deburr "F-01255-L-1 & -R-1, F-01270-L-1 &
-R-1, F-01270A-1 and F-1270D-L & -R and then you "Break the bottom and aft edge of both side skins

Here is the whole step from page23iS/U-07

Step 5: Remove and deburr F-01255-L-1 & -R-1, F-01270-L-1 &
-R-1, F-01270A-1 and F-1270D-L & -R. Prime F-01255-L-1 & -R-1.
Trim the tab from the aft edge of F-01270-L-1 & -R-1 as shown in
the detail view. Break the bottom and aft edge of both side skins
(see Section 5.10).

Happy building
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  #3  
Old 03-16-2018, 01:21 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Default

Quote:
Originally Posted by rolick22 View Post
I'm reading this as two different steps you deburr "F-01255-L-1 & -R-1, F-01270-L-1 &
-R-1, F-01270A-1 and F-1270D-L & -R and then you "Break the bottom and aft edge of both side skins

Here is the whole step from page23iS/U-07

Step 5: Remove and deburr F-01255-L-1 & -R-1, F-01270-L-1 &
-R-1, F-01270A-1 and F-1270D-L & -R. Prime F-01255-L-1 & -R-1.
Trim the tab from the aft edge of F-01270-L-1 & -R-1 as shown in
the detail view. Break the bottom and aft edge of both side skins
(see Section 5.10).

Happy building
Right but if you're already deburring the side skins, wouldn't that involve breaking an edge. I'm curious why there would be separate attention for the bottom and aft edges?
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  #4  
Old 03-16-2018, 02:14 PM
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DaleB DaleB is offline
 
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Deburring and breaking the edge are different. "Breaking" the edge means putting a very slight inward bend on it, so that it will lay up tight against another sheet where there's an overlap. All the edges get deburred. You'd break the bottom and aft edges, not the top and forward edges, because the forward and top edges will be overlapped by other skins.
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  #5  
Old 03-16-2018, 02:24 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by LettersFromFlyoverCountry View Post
Right but if you're already deburring the side skins, wouldn't that involve breaking an edge. I'm curious why there would be separate attention for the bottom and aft edges?
Because those are the only edges being recommended to do.

The top edges lap onto a flat surface and do not require it, and the fwd edges terminate at the firewall flange, so also do not require it.
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  #6  
Old 03-16-2018, 02:30 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Quote:
Originally Posted by DaleB View Post
Deburring and breaking the edge are different. "Breaking" the edge means putting a very slight inward bend on it, so that it will lay up tight against another sheet where there's an overlap. All the edges get deburred. You'd break the bottom and aft edges, not the top and forward edges, because the forward and top edges will be overlapped by other skins.
Ah, OK, that makes sense. I thought it was referring to knocking down the sharp edges.

I always referred to this task as "rolling the edges" or "forming the edges" (thus edge-rolling and/or forming tools). I'd never heard it referred to as breaking the edges before. Good to know.
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Last edited by LettersFromFlyoverCountry : 03-16-2018 at 02:39 PM.
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  #7  
Old 03-16-2018, 03:20 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Default For future reference....

Snipped from Section 5 of the manual -

5.10 LAP JOINTS
When riveting a lap joint, the expansion of the aluminum caused by the setting pressure and the expansion
of the rivet causes the overhanging edge of the sheet to bend upwards slightly. This creates a number of
problems, like making the lap joint appear wider than it is, making painting more difficult, etc. One easy method of minimizing this
effect is by pre-bending the last 1/4 inch of the skin downward just a small amount before it is clecoed and riveted. When the rivets
are driven, the skin will be flattened and the pre-set in the skin edge will tend to hold it flush. Except for very rare circumstances,
the amount of bend (break) is very small and when done properly is almost undetectable with your eye. The goal is to do just
enough to keep the skin lying flat but not too much or it will be obvious that it was done.
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  #8  
Old 03-16-2018, 04:26 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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I like to think I come by the term honestly.

https://youtu.be/DbAEuFbFaco
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