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We have a '74 PA-28-180 - the first year this model was called an "Archer".
The cowl is not in the greatest shape, partly because of its age, and partly because one of the partners a few years ago landed on a runway that was about 18" too short and slid gently into the chain link fence at the end :-( Engine has had all the AD required inspections, etc, but the cowl did get a few bruises. We're into our annual as of yesterday and we have two problems that need to be dealt with ASAP. The first is that there is a slot in the back of the bottom cowl were it slides over the nosewheel strut. To keep the two halves of this slot from flapping around aafter it's installed, a (roughly 12- 15" long) aluminum "bridge" is screwed across the gap after the cowl is put in place, held in place by four screws and large trim washers that go through the fiberglass of the cowl and into the aluminum bridge. Two of these screws, at the outer ends of the bridge, are fine. The two nearest the slot, however, have been pulled away from the fiberglass, and now have nothing to go through. The corners of the fiberglass that they used to go through are simply gone. Someone at some point riveted a strip of aluminum to the back edge of the fiberglass, and the screws now go through this, but the aluminum strips are bent and the cowl no longer fits flush. We really need to remove the cludgy aluminum strips and redo the fiberglass so that the cowl fits better. Of course one problem is that this area is very oily from years of Lycoming Leakage (LL). My first question is, what is the best solvent to remove the oil so that a repair has a chance of adhering? I plan on cleaning everything and then thinning the glass a bit roughly 1.5 inches back from the edge, and then feathering and building up the area with glass cloth and epoxy to remake the back edge of the cowl (I've done a lot of boat building and repair, so this isn't rocket science to me, although I've always worked with polyester resins before). Next questions are, what is the best fiberglass for this? mat or cloth? S-glass, E-glass or something else? What epoxy is the best for repairs? Is there a kit available somewhere with everything (glass and epoxy) I need? If I want these quickly, what source should I use? I've seen complaints about Aircraft Spruce. Would Wicks be better for fast turnaround? Someone else? The other problem with the cowl is that there has been some delamination near the top of the low cowl where the propeller shaft opening is formed. This area has a lot of curvature, and there is a foam or balsa wood reinforcement bow epoxied into this area behind the curved opening. The cowl molding has pulled away slightly from this reinforcement bow. Not very much, but the A&P thinks that this should be closed up before the delamination propogates further. This is a more difficult problem, because there is very little clearance to get anything into the gap, there doesn't seem to be an edge to overlay a patch onto, and of course I have no idea how much oil has drifted in there that would prevent adhesion. My current plan here is to wash it out with some solvent to get most of any oil film out of there, and then inject a thin epoxy as deeply as possible into the crack with a syringe. Questions here are mostly about what solvent won't dissolve the reinforcing bow if it's a foam and not balsa wood, and where can I get a really thin, watery epoxy. Also, does anyone have any other ideas about fixing this area? Of course, we'd like to get this all done before the annual is done, so that the plane doesn't have to sit outside without a cowl. The last question is, is there someplace someone can recommend that we could have this done? I really don't have the time to do this, but will make the time in order to get it done right if necessary. I've thought of calling bodyshops that specialize in Corvettes, and boatyards, but they don't usually deal with weight issues. I can just see a quarter inch of heavy polyester and glass roving added to the inside of the cowl. I'd rather not have to log a major CG change. Anyway, any and all suggestions and advice would be greatly appreciated. I woke up early this morning thinking about this. Maybe I can go back to sleep now. Thanks, guys. -- Bob (Chief Pilot, White Knuckle Airways) |
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