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  #1  
Old 10-24-2017, 12:02 AM
RyanB RyanB is offline
 
Join Date: Sep 2017
Location: South Africa
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Default Drilling the HS Skin

Morning,

When drilling the skin in the empennage did you guys first use a center punch before drilling? I have been experimenting and am worried about deforming the skin around where I use the punch.

Thanks everyone
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  #2  
Old 10-24-2017, 02:16 AM
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az_gila az_gila is offline
 
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Smile

I marked the rivet lines first, measured for the rivet spacing and then drilled #50 (1/16 pilot holes in the skin.

You can then use these pilot holes to check that the rib underneath is straight enough that the holes fall on the sharpie centerline drawn on the rib.

I basically found the #50 drill was as good as a center punch for getting accurate hole locations.
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  #3  
Old 10-24-2017, 02:21 AM
RyanB RyanB is offline
 
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Great idea! Thank you Gil
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  #4  
Old 10-29-2017, 04:23 PM
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NorthernRV4 NorthernRV4 is offline
 
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Location: Prince Edward Island, Canada
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I found I could very accurately position a #40 (135deg split-point) cobalt drill bit from Aircraft Spruce. I didn't experience any tendency to wander and they are ready for a cleco without updrilling. Like Gill said though, you can easily get the feel and stop drilling when the bit makes it through the skin, then you'll note a tiny dot with on the sharpie line or just either side of it and you can slightly tweak the substructure

I found the challenge was'nt in the drilling but laying out your rivet lines/spacing on the skin to fall in just the right places on the substructure. It's a bit unnerving at first but just measure and confirm two dozen times like I did before you put the drill to the skin. Watch the location of the notches in the ribs, spacing must be adjusted to maintain edge distance.
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  #5  
Old 10-29-2017, 05:00 PM
Michael Henning Michael Henning is offline
 
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Location: Nashua, NH
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I wouldn't worry about deforming the skin with the center punch, as the skin is going to be dimpled or countersunk down the road.
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Last edited by Michael Henning : 10-30-2017 at 07:45 PM.
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  #6  
Old 10-29-2017, 05:57 PM
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JonJay JonJay is offline
 
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Split points are made to reduce/eliminate wandering. Gil's method is basically what prepunched skins (not matched drilled/punched ribs). A line was drawn on the rib/spar center line then you could push the rib around a bit as your could see the line through the hole in the skin.
If your ribs are square and straight, that shouldn't be necessary. You can drill every other hole and use an inspection mirror and light to see that you are still within tolerance for edge distance and drill the next hole. If you see the center is starting to drift, you can then manipulate the rib slightly.
I am not sure if either way is faster or slower. Doesn't matter. That is the beauty of the early kits. You just had to figure it out and do it.
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Last edited by JonJay : 10-29-2017 at 06:01 PM.
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  #7  
Old 10-29-2017, 09:35 PM
6 Gun 6 Gun is offline
 
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Smile punch

Repeating punch works great Lowes has them.
Bob
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  #8  
Old 10-30-2017, 11:23 AM
RyanB RyanB is offline
 
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Thank you for all the replies guys
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  #9  
Old 10-30-2017, 07:46 PM
Michael Henning Michael Henning is offline
 
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Ryan,
Work fast and hard. Get it done, it is a blast to fly.
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