INTRODUCTION by Luther D. Sunderland The T-18 Newsletter began in

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INTRODUCTION
by
Luther D. Sunderland
The T-18 Newsletter began in the fall of 1964 as a result of
several letters and a visit with Dick Cavin, 10529 Somerton
Drive, Dallas, Texas 75229. Dick had essentially "kicked
off" the T-18 Mutual Aid Society with his fine article in the
September 1963 Sport Aviation magazine entitled "Reflections
From Rockford" in which he told about building the T-18
fuselage in just 3 1/2 days at the EAA Fly-In at Rockford,
Illinois. But we felt that there was a real need for a
"house organ" to circulate to the T-18 builders. Sport
Aviation was fine for reaching the general EAA membership,
but the time lag was too great, and there was not the
editorial freedom found in an informal newsletter. So, Dick
and I agreed to publish a newsletter for the exclusive use of
T-18 builders with the editing and publishing being done
alternately in New York and Texas. This continued for the
first five issues. Then family illness and work demands made
it impossible for Dick to continue, so I published all
subsequent issues up through number 44 in 1976. All articles
in these Newsletters were written by me unless otherwise
noted after the title. Then in December 1979, Dick retired
from Braniff Airlines and resumed as editor, publishing t~le
next 23 issues (by October 1986).
This volume contains a reprinted version of the first 44
issues of the T-18 Newsletters, which have been edited to
omit material that is no longer applicable. Also, comments
have been added occasionally with the notation (1986 Note:)
to provide guidance to builders where we have since learned
additional information that would shed further light on the
particular subject under discussion.
Perhaps the reader is not familiar with the T-18 aircraft and
you have obtained this book as a general reference to learn
about fabrication of a riveted all-aluminum airframe. For
anyone in this category who is not familiar with the design
concept of the T-18/S-18, a brief historical sketch is
included here.
In the early 1960s, the Experimental Aircraft Association
sponsored a design contest intended to stimulate designers to
develop aircraft that would be easy for the person with
average home workshop skills to build, one that was safe for
the low-time private pilot to fly, and one that could be
converted for transport on the highway and kept in the family
I I
garage. The several finalists that were able to meet all
contest requirements, including completion of flight tests
for a prototype, were not notably good designs and are long
forgotten, for all practical purposes. However, a design
that was not completed in time for contest judging has proven
to be the undisputed winner, for it dominated the display
area at Oshkosh for years and is still a very popular
homebuilt. It has captured a number of records for
homebuilts, including the coveted first (and so far only)
homebuilt to fly around the world and to the North Pole.
This aircraft, of course, is the T-18, and its designer is
the well-known aeronautical engineer, John Thorp. The T-18
was his 18th design. Some of his other designs were the
Fletcher agricultural plane, the Thorp Sky Scooter, Piper
Cherokee 135, Lockheed P-2V Neptune, and Wing Derringer.
When John Thorp established priorities on design criteria for
the T-18, he placed construction simplicity higher than ease
of conversion to highway configuration. The wing was
constructed in four panels, each four feet wide, so standard
width aluminum sheets could be wrapped from trailing edge to
trailing edge with no spanwise drag-producing joints. The
20' 10" wing could be detached in one piece when seven
detented pins were removed. The main drawback was that it
was a three-man operation that took about 20 minutes.
In 1974, at John Thorp's suggestion, I undertook the design
of a wing that would be much easier to convert to highway
configuration. Also, I widened the cabin by two inches to
improve passenger comfort. For eleven years, I sold
modification plans using the designation T-18CW for
convertible wing with wide body. Then in 1985, after John
Thorp took the T-18 plans off the market, I produced a
complete set of new drawings for the entire aircraft. Since
such extensive changes had been made to the original T-18
design, the model designation was changed to S-18. These
construction drawings, along with complete detailed building
instructions, are marketed by Sunderland Aircraft, 5 Griffin
Drive, Apalachin, NY 13732.
The following sections, consisting mainly of reprints of
articles from the first 44 issues of the T-18 Newsletter,
not only give a detailed history of one of the most important
homebuilt designs, but they also present much valuable
information about how to build every part of an all-metal
aircraft. How-to-do-it articles describe making fiberglas
molds and parts, bubble canopies, plush upholstery, hand
formed ribs, no-fixture aircraft structures, etc. Also,
advice is given on how to do weight-and-balance measurement
and how to flight test an aircraft. This is a veritable gold
mine of information that is of value to anyone building any
type of aircraft.
III
The first twelve newsletters contained much material that has
been outdated, so these have been condensed into a single
section. The remaining newsletters have been placed in 32
separate sections.
IV

EXCERPTS FROM T-18 NEWSLETTERS *1-12
Luther D. Sunderland
RIVETS: by Dick Cavin. Apparently some of the newcomers are
a little confused about the use of Hi-Shear rivets and Pop
rivets. Basically Hi-Shears are high shear strength steel
rivets, with an aluminum retaining collar, that are used
instead of AN bolts. They are lighter and in some other
respects superior. They can be installed very easily, using
only a hammer and a simple installation tool. It is
perfectly acceptable to replace a number 10 (3/16-inch) Hi
Shear rivet with a 3/16-inch AN bolt of the proper length, a
washer, and elastic stop nut if you have difficulty obtaining
Hi-Shears.
Almost all aluminum rivets in the T-IB structure are liB inch
in diameter. With matched-hole tooling techniques, when the
rivet holes are made around the edges of skins, frames, and
ribs, they are punched with a hand punch that was originally
invented by the Whitney Tool Company of Rockford, Illinois.
The Whitney punch set (the #5 Jr.) is obtainable from the
Whitney Tool Company or from industrial supply stores.
(Other brand names are available in 19B6 which are very
similar, do the job, and cost less.) You should order extra
#30 punches with and without the little "nib." Or you can
easily make extra punches from drill rod on a lathe by
copying the shape of the bought punch.
You cannot put a liB-inch rivet in a liB-inch hole. It takes
a #30 hole. If you dimple the skin around a liB-inch hole,
the hole will enlarge enough so that a liB-inch rivet ~111 go
in. Also, it is accepted practice to dimple the lighter
gauge skin and countersink the thicker material (040). If
you plan to flush rivet, you might want to get a set of
dimple dies for the Whitney punch. They are needed for
dimpling ribs and frames, but they do not do an acceptable
job in external skins. (Make a hand dimpling tool for skin
dimpling as described in a subsequent newsletter.)
USING TEMPLATES: by Dick Cavin. The T-IB is constructed
without the use of jigs or fixtures through a process
developed by John Thorp called matched-hole tooling. Once
a hole pattern is laid out in a particular part, it is
transferred to the mating part with a transfer template made
of scrap aluminum. Here are some tips on the transferring
(marking and drilling or punching) of holes by the use of
templates.
The first thing the builder of a metal aircraft, using
matched-hole-tooling techniques, needs to learn is how to
properly transfer hole patterns with templates. Holes are
transferred from templates with a hand duplicator punch. A
hand duplicator punch is either the liB-inch nibbed male
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punch from a Whitney punch, or a similarly-shaped slightly
longer tool that you can make yourself. It takes a little
practice and skill, believe it or not, to properly use the
liS-inch duplicator punch. Hold it between the thumb and
middle finger and sort of wiggle it in the hole. Do not try
to push it straight down into the hole, for this will not
work. Tap the punch with a hammer, not too hard. Be sure
the punch is in the hole before tapping so as to avoid damage
to the template. Absolutely do not drill through the
template. Always use the punch that has a little center nib
to transfer the hole centers. (Make sure that the nib is
perfectly centered on the end of the punch. I bought a punch
with a nib that was off center, so I had to true it up on the
lathe.) Remove the template before you actually drill holes.
Take care to keep your drill at 90 degrees to the sheet and,
in the case of fuselage sides, drill both sides and transfer
strip at one time. To transfer the hole pattern from the
skins to the bulkheads the important thing is to VERY
accurately locate a starting point. We cannot transfer hole
patterns at points where bulkheads are joggled, as this would
cause mismatch. I chose the first rivet hole above WL 42 as
my "anchor" hole. On my form blocks, I drilled a tiny hole
at this point. I tapped a wire brad lightly through this
hole, making a tiny mark on frames. On a penciled rivet hole
center line, I punched the rivet hole. Next, a rivet dowel
was used and skin transfer strip and frame were pinned and
clamped together. The hole pattern was then transferred with
nibbed punch. Sounds complicated, but it really is not.
Transfer strips should be labeled as to "up" or "out," etc.,
and extreme Care should be used so that transfer strips are
always turned the same way. THINK.
Leave the 523-1 bottom skin extend forward to cover the main
spar cutout to aid in aligning the 523-2 floor. Important!
After alignment, drilling and clecoing, cut it out. To use
rivet as a dowel through worksheet, put head on bottom, and
secure on top with tiny C clamp or piece of masking tape.
DRILLING: Great care must be taken to prevent drift during
drilling. It helps to first drill a 3/32 hole and then
enlarge to liS. Also, if two centerlines (a vertical, a
horizontal) are first drawn through the center punch mark,
they can be observed during drilling. Keep drill vertical.
Practice on some scrap aluminum.
SIDE SKIN SPLICE: If you decide not to purchase a long piece
of rolled aluminum for the fuselage side skins, make a splice
just aft of STA 179.2 (T-1S), using a 0.032 strip 2.5 inches
wide as a doubler. Four vertical rows of AN426 AD4 rivets
are used. Rivet centers should be 0.25 inches from sheet
edges. Rivet spacing is about one inch. Do not continue the
doubler under the angle at WL 42. It is much better,
however, to purchase a roll of skin material from Airparts
Incorporated in Kansas City and make the skins in one piece.
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Actually, in 1986 there is no need to use a splice in the
side skins, for it is just as economical to purchase coiled
aluminum in thicknesses up to 0.032 inches. Two side skins
can be made from a 20-foot long piece four feet wide with the
two 14-foot long skins overlapped.
FORM BLOCKS: by Dick Cavin. Have had a considerable number
of you ask "From what material do I make form blocks?" I
used a select grade of maple for all my small parts (ribs,
etc.). I used 3/4-inch fir plywood for the fuselage
bulkheads. I have heard of Beneflex (tooling masonite) being
recommended, but know it is hard to find and very expensive.
Some builders used wood chip composition board for fuselage
frame forms. If you expect to make more than one airplane
from the form blocks, glue a layer of 1/8-inch tempered
masonite to the top surface. Actually, most any wood
material will do for form blocks if it will not splinter
badly. It is important to make all form blocks in duplicate,
as you must always make a block-metal-block sandwich and
clamp it together tightly while forming. Metal will creep
from forming stress if not held tightly. The backup block
need not be a complete duplicate but can be made from pieces
of scrap wood 3/4 inches x 1 1/2 inches. Use two index pins
or 1/4-inch bolts in each side of the form block. Put pins
completely through the "sandwich" to both align parts and
restrain them. Put them near a corner so the index holes can
be punched rather than drilled in the metal part.
TOOLS: by Dick Cavin. I highly recommend another tool, the
Mead Bandsander, which looks like a small band saw. It
deburrs, sands, shapes, profiles, etc. It uses l-inch x 42-
inch belts that can be torn to 1/2 or 1/4 widths for small
areas. It is used in every aircraft factory and is
tremendous for sanding the edges of aluminum parts. Here is
something else that will save you many hours of tedious
labor. You can write Mead Specialties, Chicago, IL.
If you want to saw aluminum plate, Sears has a blade (both
six inches and nine inches) that does a beautiful job. It is
their Kremedge Non-Ferrous cutting blade. Carbide-tipped
circular saw blades are available in 1986 very inexpensively.
They will last almost indefinitely. If you have a band saw,
get a skip-toothed blade for best results, although you can
use ordinary wood cutting blades if you use a wax or grease
stick to lubricate them and keep the teeth from clogging.
MAKING FITTINGS: by Dick Cavin. You can make your own
fittings of aluminum plate quite easily. Saw them oversize
and sand or file down to a scribe line. An ordinary disk
sander works fine. I used a rubber-backed five-inch one in
areas that I could not get to with the sander, followed by
sanding with the little Mead bandsander. If you turn the
rotary files very fast, they will chatter. Take very light
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cuts, too. Final sanding is by hand using wet-or-dry
sandpaper in progressively finer grades. Make all scratches
parallel to the part edge, not perpendicular. Sprinkle a
little Bon ami on the sandpaper. This (or toothpaste) makes
a fine light abrasive. If you want to get fancy and do real
first class work, buff your fittings with a cloth buffing
wheel, using emery buffing compound, working down to tripoli
or jeweler's rouge for a true mirror finish that rivals
chrome plate in brilliance. Before you get carried away,
however, remember that all aluminum fittings must be sprayed
with zinc chromate primer to prevent corrosion, so your
nicely polished parts will not be visible for very long.
Actually you should always finish aluminum edge to as fine a
finish as possible, so as to eliminate starting places for
cracks. This gets very important on thin sheet parts (ribs,
etc.) that do more flexing. Finish the edge of sheet parts
to the extent that there are no visible scratches or nicks
perpendicular to the sheet edge. This also applies to
deburring holes. Always deburr holes before dimpling, as the
forming stress of dimpling may possibly crack light skin. If
this happens, you will have to drill it out and use an
oversize rivet.
FORMING RIBS FOR THE T-18: by Dr. B. John Shinn.
Introduction: I had always looked at formed metal ribs,
bulkheads, etc. with a sort of envious awe. I dreamed of
building my own all-metal plane, but thought that the cost of
special tooling would be too high. Having things like ribs
hydropress formed would also be too expensive.
But, then came the series,of Sport Aviation articles on the
T-1B. John Thorp made it sound like an ordinary guy could
make acceptable ribs himself with only a mallet, a bucking
bar, and some wood form blocks. Besides that, he mentioned
an alloy, 6061-T4, which could be formed without annealing.
To me, all aircraft sheet aluminum had been 2024-T3, which
required considerable care even in bending straight line
corners, let alone compound curves. My interest mounted to
the point that I was mentally stretch-forming ribs, so I
decided I would just have to build the T-1B.
Although the article in Sport Aviation ("Building the T-1B"
Part 3, July 14, 1962) was well written, I feel that a look
at my rib forming experiences might be helpful to those who
are also now ·'tin benders. '1
Form Blocks: After reading Part 3 in Thorp's articles,
checking prices on form block material (maple, birch, birch
plywood, tempered masonite, etc.) I decided on birch. It
has a fine-grained surface for non-bumpy layout, and does not
split out under heavy pounding. Besides that, it COmes in
widths (6 inches to 9 inches) which are more manageable than
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large sheets of plywood. Thickness should be 3/4 inch to
allow forming a good flange out to 5/8 inch. (1986 Note:
Today 1986 builders might find solid birch hard to locate and
very expensive, but most lumber yards have good quality 3/4-
inch birch plywood that is used for making cabinet doors.
This stands up quite well when used for rib form blocks.
Also, it is quite difficult to find 6061-T4 aluminum sheet.
Most suppliers have only T6, which can be used for ribs, but
it is much more difficult to stretch form. Phil Tucker who
bought Ken Knowles' Sport Aircraft Inc., 104 E. Avenue, K-4
Unit G, Lancaster, CA 93535 has T4 sheet, however.)
The complete airfoil template was laid out on 0.040-inch
aluminum and 0.025 inch (the thickness of the rib material)
was trimmed off the complete perimeter of the template. The
airfoil coordinates given in the plans have the exact
dimension of the main spar height. So, when a form block is
made for a specific thickness rib (0.025, 0.032 or 0.040),
then the appropriate thickness must be removed from the
original airfoil contour to allow for the thickness of the
rib material. Several 1/4-inch indexing holes were punched
to align nose and center rib sections. The location of these
locating holes is important for they must be reachable with
the Whitney punch when there is a 7/8-inch wide flange on the
rib blank. Put two of these holes along the lower side of
the nose rib portion of the template so there is adequate
distance from the bend line for the spar flange on the
shortest rib.
This airfoil template was laid on top of two 3/4-inch birch
boards and the indexing holes were drilled through
the boards simultaneously. A couple of 1/4-inch metal dowel
pins held the template on one board for the layout marking.
A sharp knife was used to trace around the template. Then a
pencil, sharpened to a fine wedge shape, was traced lightly
through the knife groove. This made an accurate layout line
which was easy to saw along. The template was "flopped"
over, doweled, and traced by knife and pencil on the other
piece of birch for the "opposite hand" rib.
For the sawing process it was discovered that the band saw
was the most practical. By carefully staying about 1/32 of
an inch from the pencil line, with this cut I avoided
excessive sanding time later.
The rough-cut form blocks were then sanded to the center of
the knife groove outline. A sanding disc mounted in a table
saw works well for this. The disc was tilted so that it
undercut the form block to compensate for the spring back of
the rib after forming. About four degrees was used for
"straight" sections while a six-degree tilt was used for the
more highly curved nose of the rib. (It is important to note
that it is much easier to make this spring-back allowance
with the initial sanding than it is to first sand to the line
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perpendicularly and then try to add the angled undercut
without over-shooting the mark.)
The edges of the form blocks were rounded to give the proper
bend radius of 3/32 inch. It was found that a small Stanley
Surform file made quick work of this with only a minor amount
of sandpapering to smooth it out.
Rib Blanks: For quick layout of the rib blanks, a 0.040
metal rib blank template was made for the nose ribs and
another was made for the center section ribs. (For the rest
of this article, we will concentrate on the nose rib
fabrication since it is the more difficult.) The airfoil
template was laid on a piece of scrap aluminum and traced
around for the nose rib section. A pair of dividers set for
7/8 inch was used. By trimming this metal to the outer mark,
a 7/8-inch flange was left all around this nose rib blank.
This blank was again placed under the airfoil section and the
indexing (locating) holes punched through. The cutout at the
front of the nose rib was made in this nose rib blank
template per the 201 drawing. It is strongly recommended
that the cutout in the actual ribs be made only after the rib
has been formed. If it is made before forming, it is almost
impossible to prevent sharp double-back creases at the front
edges of the nose rib. So, leave the rib blank at least 1/2
inch longer than the form block at the leading edge. When
the excess is trimmed off after forming, it will remove most
of the folded-back part of the flange.
Holes were also punched through this template for the corner
relief (as indicated on the prints) for the 201-1, -3, and -4
nose ribs. The -1 and -2 were close enough alike to use the
same relief holes.
Cutting Out Blanks: The 3' x 12' sheet of 6061-T4 was
unrolled on a rug in the family room (to prevent scratches)
and a few quick trial and error layouts with the rib blank
templates produced the most economical layout. A "grease
pencil" was used for this since it has enough contrast to be
visible and is easily wiped off when desired. Since the ribs
were to be trimmed after forming and generous flanges were
allowed it was not necessary to make precision layout marks-
just a quick trace around the rib blank with the grease
pencil was all. Again, do not mark the nose cutout.
For cutting up the sheet, I found that the 6061-T4 sheet was
cut up with least waste and least scratching by using a
regular pair of straight sheet metal shears. The two sides
of the sheared piece were spread apart (by one hand and one
foot) so the shears did not bind. This resulted in a slight
curvature of the new blank but it was insignificant when
compared to the stretching it was soon to undergo. The
blanks were then placed under the rib-blank template, the
locating holes were punched, and the nose cutout was scribed
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