57-10-06 Rear Spar Attach Plate
The rear spar attach plate has both a left hand and a right-hand component.
Shown to the right is the part for the left side of the aircraft
These parts can be used as a replacement for the “U” Bracket used on the UL version of the Aircraft.
The following procedures are for the modification from the ultralight to the (LD) version of the aircraft. Aircraft normally is equipped with a U channel for the rear spar attach on the ultralight version of the aircraft. That you channel is attached with a 5/16 AN bolt.
We will first drill out all of the rivets around the perimeter of the attach plate. The center hole that the Cleco is installed in in this picture will be removed but we will not be replacing the rivet.
Is an X-Acto knife to peel the remaining fabric away from the sheet-metal.
Insert the bushing, The bushing will hold the centering drill in place while cutting through the three layers of .040 2024 T-3 aluminum.
In this picture here you can see where we have cut through the first layer of sheet metal and the centering bushing is still holding all of the pieces together.
Once you have made your way through all three layers of 2024 T-3 aluminum you can take a die grinder with a fine cutting carbide bit and smooth up any of the remaining saw marks.
Using a chip chaser or other implement remove any chips from between the pieces of sheet metal and or between the fabric and the side the fuselage. The interface between the rear spar fitting and the fuselage boom should be flat as possible.
If any tears occur or the fabric is loose against the fuselage a little Polytack can re-glue before attaching the fitting.
We will start by drilling the 1/8 inch rivet holes to the final size of the fitting which is 3/16 inch. Start by drilling the two holes next to the Cleco and leave the remaining holes to be drilled after the fitting has been attached to the fuselage boom side.
Cleco or bolt the fitting to the fuselage. Normally it will take about 3 to 4 Cleco’s to hold it in place while you drill the remaining holes to 3/16.
Once the fitting has been Cleco’e or bolted to the fuselage Drill the remaining holes through each of the fitting bosses. After all the holes have been reamed to the 3/16 drillbit, remove the fitting and clean up any filings from the drilling process before proceeding to bolt the fitting to the fuselage boom.
If you already have covering on the aircraft you can go ahead and cut out the access panel locations. One located on the aft fuselage boom underneath.
And one located just forward of the aft spar carry through box.
You can now access the aft side of each of the bolts to install 3/16 inch AN 3 washers and AN365-3 Ny-lock nuts.
Although the access holes are fairly tight. They have been designed to allow access to the aft side of this fitting to install the nuts and washers. These cut out holes will receive access panel covers at a later point in time.
The left side fitting with 2 bolts left to be installed. The two center bolts located on the top of the fitting can be accessed through the opposite side hole that was previously drilled with the 1 3/4″ Hole saw.
In the following picture we have the right side in its completed stage. With all of the AN-3 bolts installed.