57-10-09 Wing Fold Fitting Overview
57-10-09 Wing Fold Fitting Installation Procedures
The new style wing fold fitting will significantly improve the fit of the fabric around the transition from the wing to the fuselage. The should improve the fit of the fabric as well as reduce the total amount of drag while retaining the ability of the wing to fold in the same fashion as originally design.
57-10-09 wing fold fitting is a replacement for the old style "U" channel that was installed on the prototype aircraft. The fitting is fairly large because it has to fit around the 2 inch diameter forward spar tube. This left a lot of material outside of the typical airfoil cross-section. The new design will allow us to maintain the same wing fold system and is interchangeable with the old-style system yet is much cleaner, stronger, and lighter weight than the original design.
Wing fold bracket
The pivoting wing fold bracket is held in place using an AN5 Bolt which acts as the primary pivot for the wing fold system. We will remove the old-style bracket and still use the original adapter (57-10-26 fuselage wing adapter) which fits inside of the 2 inch diameter forward crossover spar on the 4130 steel frame.
Old style fitting
In this picture here you can see the 5/16 bolt and Castle nut that act as the primary attachment for the wing fitting.
Wing adapter fitting
After disassembling these parts we will retain the original fuselage the wing adapter fitting part number 57-10-26 shown in anodized blue.
Old filling versus new fitting
The new wing fold fitting attaches to the main wing spar on the inside rather than on the outside like the old "U" Channel. All the parts are shown together here.
The wing fold fitting and the fuselage adapter should be assembled with a very small amount of anti-seize in between the two fittings. Than the 5/16 bolt should be installed and port up to the point that there is resistance to turning but you should be able to rotate the two parts with your hands. The next step is to install a cotter pin into the castle nut. In this picture here where showing how the cotter key installed in the conventional manner could interfere with the cross bolt that is used to attach the fuselage adapter fitting to the 4130 steel fuselage frame.
By using a punch we can insert the punch through the perimeter of the fitting to ensure that it clears the bolt and castle nut.
Clearance for through bolt
In this picture here we can see that the draft punch is not able to align itself properly because of the cotter pin interference. Because the wing fold pivots and the 5/16 bolt may rotate as well it's very important that the cotter pin not make contact with the cross bolt.
Cotter pin installation
Instead of installing the cotter pin in a conventional manner we recommend that you use the tuck method. This will allow the cotter pin to be installed securely and not be able to rotate while still providing maximum safety. We wrote an article on cotter pin installations that goes through the proper procedures for the Method for the EAA/Experimenter magazine.
After proper installation of the cotter pin install a bolt or pin through the attachment hole to ensure that it does not make contact with the bolt before installing the assembly onto the 4130 steel fuselage frame.
Torquing the Castel Nut
Proper installation the fitting can be checked by affixing the fuselage adapter fitting into a vice and using your hand try to rotate the wing fold fitting. You should be able to rotate it but we would like to have as much pressure as possible just up to the point that it becomes very difficult to rotate. With a little Anti-seize compound in between the two fittings the fitting should rotate smoothly without being loose. Maximum torque on the castle nut should be limited to 140 inch pounds. But as with any castle nut the amount of torque necessary will depend on the alignment of the castle nut with the hole for the cotter pin.
With all of the fittings now installed the wings are ready to bolt directly onto the fuselage assembly.