Started July 10, 2004
There are three flap hinges per wing. The part that bolts to the rear wing spar consists of a "U" shaped channel and a piece of 3/4" .065 tubing that is welded inside the channel piece. The tubing is then reamed to accept a rod end bearing. The flaps are then connect to the rod end bearing with a couple of angle pieces bolted to the flap spar on each side of the bearing.
I'll make the part that attaches to the wing spar first.
The Summer 1995 Beartracks newsletter contains the plans for the welding jig used to make both the flap hinges and the aileron hinges. Here is a picture of mine ready to be put to work:
The short piece of tube there is 5/8" and still needs a hole drilled in one end so it can bolt to the jig between the upright bars.
Here is one of the flap hinges jigged up and ready to be welded:
Here are the flap hinge pieces for the left wing all welded up and ready to be installed on the rear spar of the wing:
I purposely left the tubes 1/16" too long and they ended up just right after welding shrinkage.
Here is the back side showing how the tube was welded in place through the hole in the "U" shaped channel:
The next step is to make the parts that bolt to the flap and aileron spars. These are simply .062 or .080 (depending on location), 4130 "n" sheet that has been cut to the shapes as shown in the plans, then bent to a 90 degree angle in a brake. Here they are:
The longer ones in the back row are the flap hinges and the shorter ones in front are the aileron hinges. Those with a double "hump" are for the flap or aileron push rod and are made from .080 thick steel. Single hump ones are hinges only and are made from .062 steel plate. When these were bent on the brake I made sure to set it up similar to the way we did it on the spars, to create a nice bend radius on the inside corner, to prevent cracking.
The double "hump" hinges require two holes to be drilled. One for the hinge rod end attachment and the other for the flap (or aileron) push rod attachment.
I will hold off priming the hinges until I can drill and rivet the rod end bearings in place.
Completed: July 17, 2004
Total time: 28 hours (includes making welding jig)
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