The best of the original flap hinges was used as a pattern to locate holes for the new hinge segments. The #10 bolt holes are 9/32" from the outside edge of the hinge and centered on the hinge 1-5/8" on centers. The 1/8" rivet holes are 3/16" from the outside edge of the hinge, one hole is centered and the outer holes are 3-3/8" on centers with the inner holes 3/8" inward. All of that could be measured and done carefully by hand for one hinge. For 6 hinges, per flap, it is quicker to use a Whitney punch and duplicate the holes.
The
peened end of the hinge was opened and the pin removed.
A segment of the new hing material was used to make a master by clamping the old segment to the bottom of the master with the loops pulled snug and centered to locate the holes. The Whitney punch with a
nibless punch was used to duplicate the holes in the master.
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.
.
.
.
The new blank was then placed under the master snugged, centered and clamped so the holes could be transferred from the master to the new segment. This require another modification to the poor old Whitney punch to add a clearance for the loops. This was
easily done with a file and some
careful cleaning before putting the punch and die back in.
.
.
.
.
As each hole is punched a
cleco is installed to help assure nothing moves to mess up the hole alignment. The same process was then used to make the other halves.
.
.
.
.
.
The last thing to make was the hinge pins. These were cut from the pin stock with snips, the ends squared up
on the belt sander and, a slight
chamfer added to
deburr the end.
With the pins installed the ends were peened with a hammer making sure both ends were closed enough to keep the pins retained like the factory hinge.
The fittings and hinges are all riveted back on. Waiting for the AN442 rivets for the end of the control fitting was worth the time. They're in the worst spot to get to and were the easiest to install. With the flat head the tool doesn't have to be perfectly centered. By using one of my dies with a flat ground on one side it was easy t0 get into the tight space and squeeze them. Now I just need to finish writing up the 337.
I decided to remove all the fittings from the flaps to check for corrosion between them and the spars. The parts were all plated, poorly, or zinc chromated. There was rust on the back of all of them, stop strikers and actuator fittings. I have them all cleaned up, treated for corrosion and epoxy primed. I also did the engine mount.
The aluminum spar was covered in rust from the fittings but had no corrosion. I glass bead blasted the areas to clean them, conversion coated them and epoxy primed.
Once the primer is well cured I'll rivet them all back on and finish the paperwork.
The best of the original flap hinges was used as a pattern to locate holes for the new hinge segments. The #10 bolt holes are 9/32" from the outside edge of the hinge and centered on the hinge 1-5/8" on centers. The 1/8" rivet holes are 3/16" from the outside edge of the hinge, one hole is centered and the outer holes are 3-3/8" on centers with the inner holes 3/8" inward. All of that could be measured and done carefully by hand for one hinge. For 6 hinges, per flap, it is quicker to use a Whitney punch and duplicate the holes.
The peened end of the hinge was opened and the pin removed.
A segment of the new hing material was used to make a master by clamping the old segment to the bottom of the master with the loops pulled snug and centered to locate the holes. The Whitney punch with a nibless punch was used to duplicate the holes in the master.
.
The new blank was then placed under the master snugged, centered and clamped so the holes could be transferred from the master to the new segment. This require another modification to the poor old Whitney punch to add a clearance for the loops. This was easily done with a file and some careful cleaning before putting the punch and die back in.
.
As each hole is punched a cleco is installed to help assure nothing moves to mess up the hole alignment. The same process was then used to make the other halves.
. 
The last thing to make was the hinge pins. These were cut from the pin stock with snips, the ends squared up on the belt sander and, a slight chamfer added to deburr the end.
