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Builder Spotlight

February 2017 Issue




Restoring a Stored Homebuilt

Expect the unexpected.

What happens when you find a plane in a barn in "great condition"? You just dust it off and fly it, right?

No, the work is just beginning…

It wasn't exactly found in a barn, and I wasn't the one who found it, but it wasn't all that different, either.

It started when my friend Scott went to a nearby airport to test fly his ultralight motorglider. An older gent struck up a conversation with him, and asked if he wanted to see the biplane in his garage a couple of miles away. Not having anything better to do once his glider was packed up, Scott followed the gent to his house, where a nice little Fisher FP-404 was disassembled and gathering dust. Now, Scott didn't need another airplane. He already had the motorglider, a paramotor, and two other planes he'd built: one in storage and one awaiting repairs after wind damage. But the FP-404 was so pretty and the price was right, so he bought it on the spot and trailered it home (the deal included a box trailer just big enough for the plane).

The purchase price included a trailer that was just big enough to store and transport the plane.

As I said, Scott really didn't need another plane, so I immediately offered to take it off his hands, pointing out that with all his other projects, he was unlikely to ever fly it. It took him another two years to finally agree I was right, whereupon I promptly sold my Kolb UltraStar and became the proud new owner of the Fisher. I towed it home, pulled the fuselage out into my front yard, poured myself a Scotch, and climbed into the cockpit, sipping the whisky and soaking up the atmosphere of my new toy while looking over the logbooks.

The logbook included entries like "Stored for winter...extreme cold," and "No raccoons."

Built by Norman Shaw of California, N59LS received its airworthiness certificate in 1991. Norm flew it for around 300 hours before selling it, apparently due to health reasons, and delivered it clear across the country in the trailer. The new owner flew it rarely, logging only about 10 hours over several years, after which it sat for 10 years until Scott found it. The logbooks are…interesting. The original builder's entries are concise and professional, but the second owner was more conversational, with stapled-in copies of his medical certificate and comments like, "Stored for winter…extreme cold!" and a reassuring note that there were "no raccoons." Supplementing the logbooks was a binder containing build photos, thorough builder's notes on maintenance and flying, sketches, receipts, and catalogs.

The plane had a number of modifications from the original design: The lower wings were shortened nine inches on each side, the fuselage stretched three inches, the elevator control linkage redesigned, and some other minor mods. The big change was the use of a 40-hp Mosler (half VW) four-stroke engine instead of the original design's 50-hp Rotax 503 two-stroke. This results in a plane whose climb performance can best be described as "leisurely," but burns less than half the fuel and sounds like a biplane should, rather than a two-stroke whine.

New fuel gauge and a wooden mounting tray for a smartphone running Avare, a free GPS moving map app.

Small Problems

When I brought the plane home at the end of May, I knew it would need some minor work. Scott had pulled it out of the trailer once to test run the engine, but had done no other work. There were a couple of minor wood repairs needed (hangar rash), but otherwise the plane appeared to be in excellent condition, just dirty. I intended to replace all the fuel lines and flush the fuel system, replace all the primary structural bolts and nuts, and otherwise carefully go over the plane. I expected to be flying in a few weeks; I should have known better. I spent the next six months being perpetually "two weeks away from flying." The routine became to come home from work, pull the plane out, work on it until I ran out of daylight or parts, and put it away again.

The first order of business was to thoroughly clean the plane inside and out. Mice had taken up residence in the lower wings and tail, but other than some staining, there was no damage and the wood and fabric were sound. Fortunately with such a small plane, it was easy to hold the wings vertical and shake them until everything (fluff and acorn shells) fell out. The woodwork came next. With some West System epoxy and microfiber, I made repairs to a turtledeck stringer, a vertical stabilizer brace, and one wing-root rib.

Next came the fuel system. The rubber gasket in the gas tank cap had perished and was replaced. The blue urethane fuel line had broken in several places and needed to be replaced. I also added a new fuel shutoff valve (there wasn't one originally). The fuel gauge was just a loop of the blue hose passing through grommets in the instrument panel with (inaccurate) markings on the panel. I replaced that with a section of heavy-wall clear tubing and brass elbows top and bottom, with an orange "Piper fuel ball" floating in the tube. I also soldered plugs into the brass elbows and drilled a 1/16-inch hole through the plugs to dump fuel slosh through the tube and prevent the ball from getting stuck. Finally, I recalibrated it both for level flight and a three-point attitude on the ground.

The tank vent was simply open inside the fuselage (bad), so I piped it outside to the top of the cowling, pointing forward for some ram air effect. To prevent spillage on a hot engine in the event of a nose over, I put in a check valve that allows air in, but won't let fuel out. The fuel tank itself was removed and flushed out, and a new finger strainer installed. While the tank was out, I found another broken glue joint on a tab holding the fuel tank straps. That one wasn't strong enough to begin with, so I reinforced it before reinstalling the tank.

A broken glue joint on a tab holding the fuel tank straps. It was reinforced before the tank was reinstalled.

Forward of the firewall, the gascolator was hard piped to the carburetor and hanging only from the pipe elbow, just asking for a cracked fitting. I fabricated a new bracket to mount the gascolator to the firewall, with flexible tubing going to the carburetor. I then did a fuel flow test since I had changed the plumbing. The oil cooler lines looked fine, but I bought new hose to replace them anyway, waiting until after I ran the engine, so I could warm it up before draining the oil.

When I first tried to start the engine, I had a great deal of trouble. There was low compression on one side, which I hoped was just a sticky valve from sitting for a long time. When I eventually did get it started, it ran fine, and the compression was better afterwards. I drained the oil, replaced the oil hoses, installed an oil temperature gauge and new spark plugs, and set the valve clearance.

Finally I was ready to mount the wings to identify the hardware I wanted to replace. With the help of a friend, I got them on, and as the weather was good, I left the plane tied down in my front yard for a few days (no doubt cementing my reputation as the neighborhood nut) while measuring and noting bolt sizes and grip lengths.

Around this time I got the plane registered in my name. Scott never registered it or even got an official FAA bill of sale for the plane, so I had to travel to another state, meet the previous owner to get his signature on the form, and then I had to visit the FSDO to get a replacement for the missing airworthiness certificate, along with my new registration. As it turned out, it was on the day after the old registration expired.

Next was the replacement of most of the critical bolts. This involved multiple orders from Aircraft Spruce, as I went back and forth trying to reconcile the sizes given on the very faded drawings and what was actually used on the plane, where (as is often the case) many things didn't quite match the prints. I ended up buying a lot of extra bolts, one grip size longer and shorter, just in case. There were a number of places where completely inappropriate fasteners were used, most of which I suspect were used by the second owner during disassembly/reassembly, as all of the less accessible fasteners were correct.

Big Problems

Around this time I found the first serious problem. The Fisher plans call for aluminum tubing with flattened ends as tail brace struts, but the builder used steel cables instead with formed strap eyes and swaged ball ends. Such terminals are adequately strong when properly used, but he bent the ends so the bolts could pass through the surfaces and into the corresponding terminal on the other side. Something made me want to look closely at the straps with a magnifier, and when I did, I found most of them were cracked on the outside of the bend. Yikes. This meant more delay while I worked out a replacement, in the end using new thicker bent tangs with cable thimbles and Nicopress sleeves like my Kolb had. Stacking more or fewer washers under the tangs allowed tension adjustment.

The original builder used steel cables with formed strap eyes and swaged ball ends instead of tail brace struts .

Notice the cracks in the strap eyes.

These were replaced with new thicker bent tangs with cable thimbles and Nicopress sleeves.

By this time it was the end of July and the flying season was half over. August was filled with planning and traveling to my daughter's wedding on the other side of the world, so not much got done. September saw new top wing center section covers to replace missing ones, new pitot and vacuum lines, rubber instrument panel mounts, new shoulder harness and supporting cable, new brake cables, greasing wheel bearings and landing gear spring struts, repairing the radio antenna cable, making a new mount for the handheld radio, and no doubt other things I've forgotten.

At the end of September a miracle happened. There is a long wait for hangars at my local airport, and I didn't know what I was going to do, but one opened up a half hour before I arrived to buy a can of avgas. I was in the right place at the right time, and a few days later I moved the plane to the airport and scheduled an A&P for the condition inspection.

When assembling the plane at the airport, I found the next big problem. I don't know how I missed it earlier, but much of the rib stitching in the bottom wing was broken. Clearly it would have to be dealt with, but as the A&P was already scheduled, I figured I'd have him do the inspection at this time anyway and discuss how to fix it. He didn't like the broken stitching, of course, and he also didn't like the way the trailing edge strip (which forms the cove for the ailerons) was curled up due to fabric tension, with resultant minor puckers in the fabric along the ribs. I later learned that this is a common problem with this and similar designs; there isn't adequate support for that strip, and the fabric tension tends to pull it up. This causes the tension to relax, with resultant puckers in the fabric. The A&P didn't find anything else wrong with the plane, but the wing issues needed to be fixed.

For the trailing edge repair ¼-inch plywood gussets, curved to clear the ailerons, were glued into place while clamps pulled the strips back into position.

This turned out to be complicated. Not only was the stitching broken, it had been done with very light thread instead of normal rib-lacing cord. At first we thought the trailing edge issue and the relaxing of the fabric tension caused the stitching to break, but it later appeared that mice had chewed it. At some point, one of the previous owners had attempted to repair and reinforce the trailing edge, but not very effectively. At this point the A&P and I had a disagreement. He was dubious about any trailing edge repair, but was adamant that broken rib stitching could not be repaired since there is no "standard" repair for it in AC 43.13. He felt the wings would have to be recovered. I pointed out that it's not a "standard" airplane. Without resolving the disagreement, I removed the lower wings and brought them back home. The top wings were fine; with no ailerons the trailing edge design is different and mice never got into them so the stitching was intact.

The trailing edge repair turned out to be fairly easy. Some ¼-inch plywood gussets, curved to clear the ailerons, were glued in, while clamps pulled the strips back into position, which in turn pulled out most of the wrinkles. Having the ailerons off also allowed me to better look through access holes in the rear spar and verify there was no further damage to the wood inside.

Instead of a continuous strip of finishing tape over the new stitching, there are 254 individual pinked patches over each stitch. The idea is if one patch comes loose, it won't take the whole strip with it.

I decided to restitch the existing covering, going through the existing finishing tape rather than disturbing it. Instead of a new continuous strip of finishing tape over the new stitching, I used individual pinked dollar patches (254 of them, which my wife volunteered to cut for me) over each stitch. The theory here was that if one patch came loose, it wouldn't peel back and take the whole strip with it (none have come loose so far). The finish used was an issue; the plane was painted with automotive enamel over the now discontinued Ceconite 7600, raising questions about gluing the patches on. Rather than attempt to remove the paint and go down to the bare fabric, I scuffed it and glued the patches on with 3M Fastbond, which is reportedly the same thing as the Stewart Systems adhesive. The Stewart process is approved for repairs to other finishing systems, and Ceconite 7600 was in fact a predecessor to the modern Stewart system. Some brushed-on gray waterborne primer as a UV blocker and filler, followed by the original enamel applied with a hobby airbrush (I got some remaining enamel with the plane, which surprisingly was still good after 25 years), and I was done. I'm not a great painter, but from 10 feet away you can't tell, and I think if I ever get around to compounding it out, it'll blend in even better. I did test the repair technique on a test frame first. All of this was done in the cramped quarters of the 12-foot trailer with space heaters running all night to allow the epoxy and paint to cure in the now cold weather.

The A&P was still uncomfortable with the "non-standard" repair, but I talked to another A&P who understood that this is Experimental aviation, and the plane was signed off in late November. The first flight took place the next day, six months after I started. It's a sweet flying plane with, as I said, "leisurely" but "adequate" performance.

Epilogue

It's been said that a long-stored plane or engine will often seem fine at first and then develop problems; indeed that is what happened over the next six months. The magneto soon failed, fortunately on the ground while taxiing. That story, and my journey through surplus and rebuilt magnetos and related parts, can be found in "Magnetos for Half VW Engines," in the July 2016 issue of KITPLANES®. I was still having intermittent problems with hard starting, poor idle, and the engine occasionally quitting on the landing roll, which led to me rebuilding the carburetor and (what eventually fixed it) removing the cylinder heads and having the valves ground.

The improvements continue. As an engineer by trade and temperament, I'm rarely able to leave things alone. I designed and built a new oil separator and tailwheel, added baffling to improve the oil cooler effectiveness, improved the wheelpant attachments, and numerous other minor things. The plane is flying reliably now, and I have (as of this writing) a bit over 50 hours on it. But I still have a "to-do" list. That's what makes it "Experimental," isn't it?

A year and a half after restoration, the FP-404 is still flying great. (Photo: Theresa Hague)

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