February 8, 2015 - Backing Strips/Nutplates

My next task is to fashion aluminum backing strips and attach nutplates to them to give the spar bolts something to screw into.  Now this is something I know how to do -- and I have the tools -- since I installed hundreds of nutplates in the RV.  Frankly, I am the nutplate king!

First I made 28 little 1-1/4" by 3-3/4" rectangles out of .032 aluminum.  The metal cutting blade on the bandsaw went throught the aluminum like a hot knife through butter.
   
Of course, each aluminum edge needs to be smoothed.  I used the scotch-brite wheel on my bench grinder to do the heavy work.
   
Then I used the file, the emery cloth, and scotch-bright in progression to get the edges nice and smooth.  Unsmooth strips on the right, smooth strips on the left.
   
Then I drilled the backing strips to the spar ladder and screwed them down with brass screws per the plans.
   
Then flip the spar ladder over and using the spar ladder bolt holes as a guide, drill through the aluminum backing strip.
   
This is what it looks like after "match-drilling" the backing strip.
   
I labeled each backing strip with my Engraving Tool.  I had bought it a long time ago from Harbor Freight for use on the RV project.  Only a few bucks.  It's great for labeling aluminum parts.  Magic marker smudges off too easily.
   
Now drill the nutplate holes, using the nutplate itself as a template.
   
All the nutplates holes are drilled for a single spar ladder.  The backside nutplate holes are countersunk using my deburring tool.  I use special "oops" 3-3.5 rivets for nutplates.  They have a smaller head than the normal 3-3.5 rivet so you don't have to countersink; just a few extra turns with the deburring tool does the job.
   
I used the my "Main Squeeze" tool to rivet the nutplates to the backing strips.
   
Looking at the other side of the backing strip.  You can see how the rivet manufactured heads are flush.
   
Screw the backing strips on to the spar ladder for the second, and last, time.
   
I like to make sure  each AN-3 and AN-4 bolt screws through the spar ladder and into the nutplates properly.  All of them did except one, and a little work with the needle file took care of that.  Better to do it now, than have an issue when spars are all sealed up and the nutplates are inaccessible.
   
 
   
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