Saturday, July 6, 2013

major setback #1

Well, it really felt good to finish the vertical stabilizer. All I had to do was bolt the upper hinge assembly to the back of the rear spar and I would be done with my first complete part—the Vertical Stabilizer.   Unfortunately,  I had a sinking feeling because the inside of those nut plates looked a bit small.   I spent some time with good lighting and some calipers and confirmed that I had made a mistake by assuming that a K1000-3 was smaller than a K1000-4.  Damn.  I think I really screwed up by installing -4's inside the assembly instead of -3's.

from a posting on Van's Airforce

I am just going by memory. If I am wrong, someone will correct me.
3 stands for 3 sixteenths or #10 screw
4 stands for 4 sixteenths or 1/4"
6 stands for #6 screw
8 stands for #8 screw
A 1 in the hundreds place means the nutplate is designed for dimpled skin.


I'll be damned if I can find any straight answers for the sizing information on these nut plates.  As near as I can find, a -3 implies that it will accept a 10-32 screw.  Great.    Now what?

From we learn  ("A"=diameter of screw, "B" = diam of head, "C" = height of pan head)

Decimal Dimensions
  “A” Flat and Pan “B” Flat Head “B” Pan Head “C” Pan Head
Size MaxMin MaxMin MaxMin MaxMin
6-32 .137.131 .279.244 .270.256 .097.087
8-32 .163.157 .332.292 .322.306 .115.105
10-24 .189.181 .385.340 .373.357 .133.122
10-32 .189.183 .385.340 .378.357 .133.122
1/4-20 .249.236 .507.452 .492.473 .175.162

To convert the decimal dimensions shown above to fractional dimensions, simply multiply by 64. The result will be the number of 64ths of an inch equal to the decimal dimension. For instance, the thread size on a 1/4-20 screw is given as .249". Converting to a fraction, multiply by 64 (.249 x 64 = 15.936). The answer, 15.936, rounds to 16/64, or 1/4 of an inch.


Corresponding Fractional Measurements
  “A” Flat Head “A” Pan Head “A” Round Washer Head “A” Truss Head
Size Approx. Dia Approx. Dia T maxApprox. Dia T maxMaxMin
4 7/32 7/32 3/32N/A N/AN/AN/A
6 9/32 17/64 7/64N/A 3/3221/645/16
8 21/64 21/64 1/83/8 7/3225/6423/64
10 25/64 3/8 9/647/16 N/AN/AN/A
12 7/16 27/64 5/32N/A N/AN/AN/A
14 1/2 31/64 11/64N/A N/AN/AN/A

With that bit of information, I can finally figure out that a 10-32 is 12/64" = 6/32" = 3/16"



small   K1000-3 ?      = 3/16 = 6/32
medium  K1000-4      = 4/16 = 8/32 
large   K1000-06    = 9/32 = 9/32

Now, I'm still confused.  These are the 3 sizes of nut plates in my kit.  I selected the smallest one because it was what I thought went with -3.  This appears to be the case, but the -3 clearly doesn't fit then AN3 bolt. 

IMG 0020 2


If I have to re-work this thing, here's the instruction sheet I made for myself.  (1-3 are unrelated  and are going to be done for QC.)

V-stab re-work:

1) remove Fwd Skin from VS Assy
2) smooth top edge of all residual excess material
3) break rear/lower edges inward
4) drill out rivets connecting VS rear spar to 
top rib, 
mid rib, 
upper main rib, 
lower main rib,
both edges of main skin
5) remove VS Rear Spar
6) drill out rivets connecting Lower Main Spar from Main Skin
7) remove Lower Main Spar
8) drill out rivets to remove incorrect nut plates from Upper Spar Cap 
9) replace with correct (K1000-3) nut plates
10) attach Upper Hinge Assy to VS Rear Spar / Upper Spar Cap !
11) re-rivet Rear Spar to Main Skins & all Ribs
10) drill out rivets to remove incorrect nut plates from lower edge of front spar
11) replace with correct (K1000-3) nut plates 
12) replace Fwd Skin Assy onto Main Skin
refer to this assembly as Vertical Stabilizer

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