Experimenter

May 2013

Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.

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Sometimes preservatives can be used. These should always be applied to clean areas; they can be applied by spray or brush. They are typically used in areas subject to wheel spray and other lower areas on a plane where debris settles—basically the bilge areas of your aircraft. Paraketone (pronounced "parrah key tone") can be used; it is a semi-dry amber liquid. I have applied it to wheel wells, strut housings, and speed brake wells on F-4 Phantom aircraft. It can periodically be cleaned off and replaced as it can attract dirt. Paraketone never really fully dries. We used it on our F-4s based on an aircraft carrier in a sea salt environment. Aircraft based at airports along the coastline also can have salt corrosion problems and may require more frequent washing and paint touch-ups than those in "dry" areas. I hope these comments help with the construction or restoration of your aircraft project. A little planning and preventive maintenance can give you many years of enjoyable flying without compromising the construction with time-delayed corrosion. Always be vigilant of materials or corrosives that can harm your aircraft. I have only touched on the basics of this topic. A wealth of in-depth data is available through all kinds of EAA, military, and FAA manuals. Chuck Burtch, EAA 10213, has built and restored a variety of aircraft and is a long-time member of the EAA Air Academy staff. He is also an active EAA technical counselor. Other corrosion problems on aluminum structures include exhaust trails and vomit. Exhaust residue is very corrosive and requires frequent cleaning and paint work. I personally know of a Piper Cherokee in which this is a continuous task, downstream of the exhaust. Also, if someone gets air sick, make sure it is all cleaned up. Vomit is very corrosive and not a great smell on a hot day. Carry sick sacks! Finally, battery boxes are another big problem with lead acid batteries. Keep everything clean, and use the special paint where required. Modern recombinant-gas dry-cell batteries are wonderful pieces of technology, but if the installation calls for a flooded (wet-cell) battery, make certain that the battery box is properly sealed, properly coated, and that the vents are clear. The box itself is not the only concern. The area under and around the box as well as both the interior and exterior areas around and downstream of the vents are typical locations that require special attention with regard to corrosion. Things to Remember Tese photos show vent holes drilled in longerons and diagonals as they would form a cluster over the vent holes.  Holes allow both venting and oil fow. • Never use brake cleaner on anything that is to be welded. It will produce phosgene gas which can kill or permanently harm you. • Use proper safety equipment when spraying primers, preservatives, or varnishes. • If using MEK (methyl ethyl ketone) or another solvent, follow the safety instructions and never use it with your bare hands. And use in ventilated areas only! • Never use cadmium-plated hardware or tools on titanium parts. • Beware of walking on ice melt and then entering the cockpit. Keep some flying shoes. The salt can be corrosive to the interior. • Beware of sandblasting with recycled or recovery sand that has been used on different metals, for example, stainless steel and carbon steel. Photography by Robert Quick EAA Experimenter 35

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