Sequoia Aircraft Corporation F.8L Falco, Construction Manual

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F.8L Falco Construction Manual 8–5 Revision 4, March 1, 2002
production Falcos were built entirely with Aerolite. Aerolite is highly recommended.
For those jobs where a longer working time is needed, we recommend Koppers Penacolite G-1131
resorcinol adhesive. Resorcinols are the most durable room-temperature-setting wood glues, and
Penacolite G-1131 is the best choice among the many brands available. Used on the Bellanca
Viking and the French Robin aircraft, Penacolite G-1131 is highly recommended. It isn't as easy
to use as Aerolite, doesn't gap-fill as well and requires more clamping pressure.
Because of our concerns about the temperature performance of epoxy glues, we do not recommend
their use in building the Falco. Many builders regard our concerns as excessively conservative and
cite the lack of problems with homebuilt aircraft built with fiberglass, wood and epoxy. If you
share that view and choose to use epoxy, you will not be taking any greater risk than those who
build and fly fiberglass airplanes, and you will find the ease of use of epoxies impossible to
beat—particularly because the glue can also be used as a moisture protection “varnish”.
A more complete discussion of these and other glues follows.
Aerolite
Aerolite is a urea-formaldehyde resin glue which was developed for use in the famous de
Havilland Mosquito bombers. Aerolite is a two-part glue. The glue is a white powder which is
mixed with water. This should be kept cool, and most builders keep the glue in a refrigerator.
The hardener is diluted formic acid. The glue is put on one side of the joint, and the hardener is
put on the other. The glue sets up when the two pieces of wood are brought together. The fumes
from the hardener will cause the glue to set up, so you have to be careful about that.
There are two hardeners: one normal and one fast. The working time depends on the temperature
and hardener used—you will have from 5 to 25 minutes on average. You must work quickly to use
Aerolite for gluing large sheets of plywood. Use small nails as alignment pins to correctly locate
the skin, and use a pneumatic staple gun to install all of the nailing strips quickly.
It is easy to forget to put on the hardener and never realize your omission—best to put some green
food coloring in the hardener so that you can see that you have used the hardener. Don't use red
since inspectors might take it for rot. An excellent applicator for the catalyst is one of the little
wedge-shaped, sponge-like foam paint brushes sold in hardware stores as cheap substitutes for sash
brushes. The head holds enough formic acid to wet most of a skin sheet, and the brushes are very
cheap.
Aerolite may be ordered from Trimcraft Aero, Wicks Aircraft, Aircraft Spruce and Specialty and
others. Ciba-Geigy's instruction sheet for the use of Aerolite 306 is reprinted in Appendix D of
this manual.
Penacolite G-1131 Resorcinol
Ask any expert what room-temperature-setting wood glue will produce the most durable joint.
The answer is always resorcinol, unless the expert is marketing another glue. Tests by the Forest
Products Laboratory—the world's most authoritative experts on wood technology—confirm this.
Properly glued, resorcinol results in a joint that is virtually unaffected by age, heat or moisture.
Best results do not always come in the same package with ease of use, even with Penacolite G-
1131 which is probably the easiest and most forgiving resorcinol to use. Penacolite is a two-part
adhesive, and a powdered hardener is mixed with a liquid resin. The mixing ratios are important
and require weighing—measuring by volume is not recommended. A minimum temperature of