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  #1  
Old 08-10-2018, 02:27 PM
RandyAB RandyAB is offline
 
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Default Gretz mast question.

I'm a bit confused as to the instructions for mounting the Gretz mast. The confusion involves the holes common to the backing plate and the supporting angle. The instructions seem to state to drill these holes to the skin as well but then state to use flush rivets to rivet the backing plate to the angle without mention of the skin. This would leave open holes in the skin along that rivet line. If the skin does need to be riveted to both the backing plate and angle along that rivet line would one dimple the skin and countersink the backing plate to accept the dimple or countersink the skin?
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  #2  
Old 08-10-2018, 02:46 PM
MED MED is offline
 
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Hope this helps.
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  #3  
Old 08-10-2018, 03:04 PM
RandyAB RandyAB is offline
 
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That seems to be what the instructions say . That means that the skins shouldn’t be drilled along that rivet line. I’ve seen pics of installs that have skin rivets along that line. The instructions also don’t explicitly say not to drill those holes in the skin. Quite the opposite in fact. Hence the confusion.
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Last edited by RandyAB : 08-10-2018 at 04:15 PM.
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  #4  
Old 08-10-2018, 03:04 PM
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RV-14E RV-14E is offline
 
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You might follow my 7 part series of post describing how I did mine.


Doubler plate match-drilling and placement




Wing skin hole



Mind the order of the parts (drawing from Gretz manual).





Plumbing of lines.



Though later I discarded that for a different approach.



Wiring



Doubler plate riveted in.



Mast powder coated.



Installed.

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Last edited by RV-14E : 08-10-2018 at 03:10 PM. Reason: Bigger images
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  #5  
Old 08-10-2018, 03:20 PM
RandyAB RandyAB is offline
 
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Nice pics. You can see that you put rivets in the skin along the rivet line in question while MED put them just between the backing plate and the angle. The instructions seem to point to both ways of doing it. I'm not finding them clear in this regard. Did you dimple or countersink the skin to accept the 426 3-4 rivets?
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Last edited by RandyAB : 08-10-2018 at 04:18 PM.
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  #6  
Old 08-10-2018, 08:41 PM
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RV-14E RV-14E is offline
 
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Quote:
Originally Posted by RandyAB View Post
Nice pics. You can see that you put rivets in the skin along the rivet line in question while MED put them just between the backing plate and the angle. The instructions seem to point to both ways of doing it. I'm not finding them clear in this regard. Did you dimple or countersink the skin to accept the 426 3-4 rivets?
Randy,

Thanks. More verbose explanation can be found in the links above each picture.

I dimpled all mating parts (skin, angle and backing plate). As long as you satisfy edge distance requirements, you'll probably have a more stout install if you rivet through the skin. Also, if you countersink the skin (assuming it's thick enough to accept a c/s), it may not be as strong a joining.

Sorry the Gretz instructions aren't clear. That is frustrating. FWIW, he states to "..drill the backing plate to skin holes through the backing plate and through the skin...". Then he says "Dimple the holes in the angle, backing plate and skin." So, with those two operations, it wouldn't make sense to dimple all those parts and not fasten them all together with rivets. Further, Figures 2 and 3 in his instructions show the backplate dimpled. This implies the mating skin is dimpled (which you've match drilled to the backing plate), rather than c/s'd, too.

Hope you get it sorted out and can move on soon.
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Last edited by RV-14E : 08-10-2018 at 08:47 PM.
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  #7  
Old 08-11-2018, 12:40 AM
RandyAB RandyAB is offline
 
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Quote:
Originally Posted by RV-14E View Post
Randy,

Thanks. More verbose explanation can be found in the links above each picture.

I dimpled all mating parts (skin, angle and backing plate). As long as you satisfy edge distance requirements, you'll probably have a more stout install if you rivet through the skin. Also, if you countersink the skin (assuming it's thick enough to accept a c/s), it may not be as strong a joining.

Sorry the Gretz instructions aren't clear. That is frustrating. FWIW, he states to "..drill the backing plate to skin holes through the backing plate and through the skin...". Then he says "Dimple the holes in the angle, backing plate and skin." So, with those two operations, it wouldn't make sense to dimple all those parts and not fasten them all together with rivets. Further, Figures 2 and 3 in his instructions show the backplate dimpled. This implies the mating skin is dimpled (which you've match drilled to the backing plate), rather than c/s'd, too.

Hope you get it sorted out and can move on soon.
Thanks for your thoughts. They are much appreciated. I understand what your saying with the dimples. The only pause I have is dimpling three layers as the instructions seem to imply. My experience so far is that when 3 layers are involved, usually one gets countersunk so that they nest properly. I drilled the holes through the skin along that line as you did. Iíll have to think a bit more as to how best to nest them. I will probably could btersink the backing plate to accept the skin dimple since it is captured between the two other layers as thus bit larger hole there will be less critical.
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