The Split Nosebowl STC allows the front of the engine and the baffles to be accessed without removing the propeller. THis can come in re4al handy at times. Well worth the time and investment. The STC is available through Fletchair in Texas.
This illustrated guide will give you detailed instructions for complying with STC SA4325NM, aka Split Nosebowl Modification. Sure makes it easy to get to the front baffles without pulling the spinner and prop. This STC is currently available through Fletchair, 1-800-FAWINGS. Splitting the Nosebowl The Split Nosebowl STC (SA4325NM) is a very helpful modification when it comes to working on your Grumman. With this mod, you can remove all the cowling and nosebowl without having to remove the prop. Add a polarized quick disconnect to the landing light and you are in business. Estimated time to complete the split can run 12 hours or more. Biggest tip: Take Your Time. An experienced shop can do it in 8-10 hours. I usually do them at home, not the shop to work uninterrupted. A large bed sheet taped to the floor will catch all the alum fillings and the fiberglass debris. If you do not have all of the skills needed for all the work, then a group project or a helper can get the project to completion. Before removing the nosebowl from the airplane, take some blue painters tape and follow the cowling split line out to the nose bowl one side at a time. I usually put the tape under the split line so the top edge of the tape is my cut line. This helps a great deal later when you have to install the metal pieces. This way you can juggle them up or down to get a perfect line. Then with additional tape make the line complete. Cut Line Creation Cut Line Creation Side View
Take a straight edge and using the cut line side of the blue tape, following the cowling line, put a pencil line where to cut along the nosebowl. You will make 4 lines, two each in each air intake. The outside nosebowl lines are already marked with the tape. Pictured below are the Right Outside, Right Center, Left Center, Left Outside.
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Now you are ready to start with the metal pieces that will form the bridges after the cowling is cut. Transfer where the holes are to be drilled from the drawing that come with the STC to each of the 4 pieces of aluminum. Cut Line Creation Side View
Quickly installing them in place (for the two straight center pieces (most inboard on each air intake), with a clamp aligning them so the cut line goes roughly through the long center line of the metal piece. You will find that the existing line of rivets (3) on the inside of each air intake make a good edge for the metal pieces, and this also acts as a stop when you are reassembling the two halves. Drill the bottom pilot holes (one equally spaced on each side of the cut line) through the alum and then the fiberglass nosebowl. This way the tears in the exit hole will be masked by the next step in drilling and the large area Tinnerman washers that will be used to secure the two halves after splitting.. I start with a 1/8 inch drill bit and then use copper clecos to hold the pieces while the bottom holes are drilled.
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