N195AK Construction Log

Photos and commentary from the construction of Murphy Moose #195SR by Mike Davis.
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PostPosted: Fri Feb 18, 2005 1:57 am 
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Joined: Fri Oct 15, 2004 6:27 pm
Posts: 112
Location: Fairbanks, Alaska
As I was finishing up with the prep work on the new stab tip rib and stainless doubler I started thinking about how to incorporate the sea fins. I want my sea fins to be removable, since I won't be on floats initially anyway, and with 7 months of winter here in Fairbanks, even when I have floats, they will only be on part of the year.

The first thing I notices was the instructions for the modification show the rib and stainless piece being riveted together using standard RV-1410 rivets, which have the rounded head on them. This would not allow the sea fin to sit flush against the tip rib like it's supposed to. Simple enough... use RR-4412 counter sunk rivets right? Well the next question is to counter sink, or to dimple... .032" ribs are thick enough to counter sink, almost... at least MAM has you counter sink in .032" material in other areas. But if you pay close attention you'll find that to truly get those rivets flush, you'll cut deeper than the thickness of the skin. What this means is you end up enlarging the hole and the rivet doesn't fit tightly in the hole anymore, and that's not good. OK, time for a phone call to tech support. Talked to Robin and he suggested dimpling the rib, then counter sinking the stainless behind it to make room for the dimples in the rib. Well I tried this, and you can see the results in the photos below... this is NOT the thing to do. Talked to Robin again, and we decided that counter sinking the rib is the way to go... even if the holes are a little over sized when you're done, with 28 rivets holding the 2 pieces together everything should be just fine.

I'll post some more pictures when I make up new pieces... these are going in the failed experiment box!


Attachments:
File comment: Skin dimpled, and the stainless doubler counter sunk to try and make room for the dimples in the rib.
2005_0217_135529AA.JPG
2005_0217_135529AA.JPG [ 56.88 KiB | Viewed 28928 times ]
File comment: Here you can clearly see that the two pieces just won't lie flat together anymore... back to the drawing board!
2005_0217_135625AA.JPG
2005_0217_135625AA.JPG [ 45.24 KiB | Viewed 28927 times ]

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