Sequoia Aircraft Corporation F.8L Falco, Construction Manual

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F.8L Falco Construction Manual 8–6 Revision 4, March 1, 2002
70°F is required, and this glue does not fill gaps as Aerolite does, thus the surfaces of the pieces of
wood must be machined surfaces. Glue pressures are important with resorcinols and Penacolite is
less sensitive to glue pressures that others.
The Bellanca Viking was made with Penacolite G-1131, as are the French Robin series of wood
aircraft. Since it is ordered direct from the manufacturer, the glue is not widely known among
homebuilders, but many Falco builders have used the glue, and they have sent in glowing reports.
We are not aware of any Falco builders using Penacolite for the entire airplane—nor do we
recommend it since Aerolite is a better choice for those poorly-fitting joints you don't like to
admit having made. Use Aerolite for most of your work, and when you need more working time
and have a good fit, use Penacolite—particularly for things like the spar and fuselage frame
laminations.
Penacolite must be ordered direct from Koppers Company. See the F.8L Falco Kit Price List for
ordering information. Koppers Technical Bulletin on the use of Penacolite G-1131 is reprinted in
Appendix D of this manual. (Because Weldwood Resorcinol glue is also widely used, we have
reprinted the Product Data Sheet in Appendix D as well.)
Plastic Resin Glues
Weldwood Plastic Resin glue is the best-known glue of this type, which is a urea-formaldehyde
glue like Aerolite. Aerolite uses an acid as the hardening agent, while “plastic resin” glues use a
dry powder catalyst that is activated in the presence of moisture. It is almost foolproof to use and
economical. It requires moderate clamping pressure but is not sensitive to glue pressures. Like
resorcinol, this glue does not have good gap-filling characteristics. This glue has been used for
years on the Pitts Special and is used on the Christen Eagle. This was also used on the wood-wing
Mooney aircraft.
We do not recommend the use of this glue with birch plywood. For reasons that are not
understood, Weldwood Plastic Resin glue does not adhere well to birch plywood. With some of
the first Falco ribs, this glue was used for the gussets. When the staples were removed, the gussets
fell off!
Epoxy Glues
The development of epoxies has revolutionized the use of wood in boatbuilding, providing such
moisture protection that it has virtually eliminated rot, paint peeling, warping and high
maintenance. The Gougeon Brothers' West System is largely responsible for the revival of wood
boats. The “latest generation” of homebuilt aircraft are built of fiberglass, which is epoxy and
fiberglass cloth. Epoxy resins have much to recommend them. They are easy to use, require little
clamping pressure and can be used as a “varnish” as well as the glue. Before you build a Falco
using epoxy glues, you should know of their limitations.
The principal limitation is that epoxies soften with heat, and the room temperature cure epoxies
used on boats and homebuilt airplanes have poor performance at elevated temperature. Tests by
Bellanca Aircraft showed that the two most popular epoxies used by homebuilders, Chem-Tech
T-88 and FPL-16A, begin to soften at 125°F, have about 25% of their original strength at 150°F,
and have a shear strength of only 40 psi at 175°F—about the same strength as library paste. (The
epoxy industry is notorious for its lack of ethics in sales literature: Chem-Tech's literature for T-88
claims a shear strength of 1,000 psi at 180°F. Don't believe any claims unless you have run tests.)
Tests by others have indicated that the West System epoxies have slightly better performance.