Martin MO-1 Article & Plans
August 1969 American Aircraft Modeler
two years ago I scanned and posted just the plans for the Martin
MO-1 control line model intended for Navy Carrier events, but I
did not post the construction article. So, I finally added the article
for you. Here are plans for the Martin MO-1 that I electronically
scanned from my purchased copy of the August 1969 American Aircraft
Modeler magazine. To this day, the MO-1 is the preferred model for
the event. It will be interesting to see how the AMA's adoption
of new rules for control line competition that allows radio control
of any function other than elevator control will affect Carrier
competition. I foresee gyroscope stabilization and airspeed hold
functions. Plans for this fine model were drawn by Don Gerber and
Charles Reeves. All copyrights (if any) are hereby acknowledged.
"The Martin MO was an American observation monoplane built by
the Glenn L. Martin Company of Cleveland, Ohio for the United States
The Martin MO-1 is widely used in the AMA's
Navy Carrier vent.
The first all-metal plane designed and built in the U. S. Extremely
rugged, with a high-lift wing, it was shipboard operated.
The winning records with the MO-1 were set by Don Gerber and
son, John, in both Class I and II Navy Carrier. Difference between
Classes is use of 40- or 60-size engine.
Important features here: adjustable leadouts and hinged ailerons
instead of flaps.
Rossi 60 speed and K&B 40RR engines set up by Bill Johnson,
known as "Throttle Man."
Martin MO-1 3-view
A vintage aircraft's functional design is the basis
for this Junior-age-class record setter.
Don Gerber and Charles Reeves
One of the
most rewarding aspects of this hobby is the designing of a model
and then following through with the building, perfecting, flying,
and winning with this aircraft. I tremendously enjoy flying in competition
and am always looking for something different, something original
that I can call my own.
While going through the books in
a library 400 miles from home, I found the first bit of information
which led to the design of this model. The book, "Airplanes of the
World - 1490-1962" by Doug Rolfe and, of all people, Bill Winter,
showed a small drawing of the plane, and gave the information that
the MO-1, designed in 1921 as a shipboard observation plane, was
the first all-metal plane designed and built in the United States.
The word "shipboard" was all the incentive that I needed.
During the summer of 1967 I corresponded with the Martin Marietta
Corp. and got a photograph of the real plane and a good three-view
drawing. Invaluable was the letter from Martin Marietta verifying
the MO-1 as being carrier-based: "In response to your request for
verification of the use of the early Martin-built MO-1, our records
indicate that this plane was carrier-based along with the bombing
and torpedo squadrons of the U. S. Navy in 1924, but was classed
as a light-weight scout monoplane."
With this information
I drew the first set
of crude plans. Later that fall I started
corresponding with Mr. Don Gerber of Laureldale, Pa., who was the
current class I record holder. Since he was interested in the model,
I sent him a copy of the information that I had, and a rough copy
of the plans I had drawn. That winter he redrew the plans in detail,
developed construction techniques for both class I and class II
versions of the MO-1. He and his son (John) built several of the
planes of both classes. The contest record of their MO-1s during
the summer of 1968 is phenomenal. They had a total of six first-places,
five second-places and one third-place, and these include the AMA
class I and class II junior records and a first-place win in junior
class I navy carrier at the 1968 Olathe Nats for John Gerber. They
had done all this, and I hadn't even started construction on mine.
I should make it clear that this is a joint article presented
by both myself and Don Gerber, and that Don should receive the lion's
share of the credit for developing and testing the model.
If this plane doesn't convert a few of you rat race racers to
navy carrier, then you just can't be converted, because it sure
has the looks of a good, clean rat racer. The construction is similar
too, with the exception of the metal pan used on most rats today.
Start construction with the solid wing by gluing the 3/8"
redwood leading edge to the balsa plank and working down the wing
with a razor plane to the airfoil shape shown in the fuselage side
view and the wing tip section. Make sure the wing center section
bottom is flat, out to the point where the leading and trailing
edges begin to taper, and then works to a symmetrical section at
the tip. Don't cut out the ailerons until the wing has been completely
shaped and sanded. Notice I said "ailerons" and not "flaps." The
MO-1 had no flaps, so the ailerons are used as ailerons during low
speed to bank the model toward the outside of the circle and hold
the lines tight.
At this point it would be good to make
all the assorted hardware, such as the aileron horns (which I found
to be easy to make from mild steel welding rod material) the aileron
transfer horn, the arresting hook and tail skid on their plywood
mount; the main landing gear on its plywood mount, the fuel tank,
firewall, bellcrank mount leadout guide, and motor mounts.
Some of the special construction techniques developed by Don
for this model are now apparent. His first MO-1 had a solid balsa
wing which failed in flight, so the redwood leading edge was incorporated
to strengthen the wing. Special motor mounts were needed to tie
the nose to the wing to eliminate a stress crack in the fuselage
at the wing leading edge, so mounts were laminated from birch plywood
to tie together the wing, bell crank mount, firewall, landing gear
mount, and the fuselage bottom. Also the top block on the nose was
changed from balsa to bass and extended back over the leading edge
of the wing. Oh yes, the motor had to be moved as far forward as
the nose would allow to keep the center of gravity in a decent location
and since it has been mounted in a sidewinder fashion like on a
combat plane, no outboard tip weight is required.
about the control unit and then we'll continue with the construction.
The bellcrank is the J. Roberts inverted unit with the bellcrank
cut to 2 3/8". These can be purchased from Sturdi-Built, or you
can get the custom assembled unit from Bill Johnson, the "Throttle
Specialist." Bill's units are made from Sturdi-Built parts, but
because he only does custom work, he can get a better fit and smoother
operation. All his units are assembled with countersunk rivets,
which adds to their safety factor. I also recommend the use of his
fuel metering system which allows the hottest of racing engines
to be run on pressure and yet to be throttled like the best R/C
engine. The single throw set-up for the exhaust slide and fuel meter
is also available from him by ordering the Don Gerber MO-1 single
Now that most of the small details have
been discussed, let's start assembling these little parts together
to make an operating model. Cut out the ailerons, shape their leading
edge, glue the horns to them, and hinge them to the wing with the
horns running through the slots in the bottom of the wing. Glue
the cap strip over the slots and the lead out guide to the inboard
tip, and the wing is finished.
To start the fuselage construction,
drill the motor mounts for the mounting bolts and bolt the motor
to them using blind mounting nuts. Then glue in the firewall and
main landing gear. Next, mark the centerline on the bottom of the
wing and glue the wing to the motor mount unit making sure to align
the motor mount and wing centerline perfectly. Attach the leadouts
to the bellcrank, bolt the unit to the plywood bellcrank mount,
and glue the whole unit to the bottom of the wing with the bellcrank
hanging down. This will go right around the motor mount.
Cut out two identical fuselage sides and glue the tank to the
inboard side. That's right - glue it on! Add filler blocks between
the motor mounts and the fuselage side, and glue the inboard fuselage
side to the motor mount-wing-landing-gear unit. Make the elevator
pushrod long enough to reach to the vicinity of the elevator horn
and attach it to the bellcrank. Also, make up the throttle pushrod
and run it to the engine. This has been omitted on the plans because
of the many types of throttles that can be used. Install this to
suit the type of throttle that you are using on your engine. After
this has been installed, the engine should be removed, filler blocks
added to the outboard side of the motor mounts, and the outboard
side of the fuselage glued on.
the rudder, stabilizer and elevators hinge the elevators, and glue
these together as a unit. Now position the stabilizer on the rear
of the fuselage, adjust the pushrod to the correct length, and glue
the unit to the fuselage, pulling the rear end of the fuselage together
at the same time.
The arresting hook and tail skid
unit can be installed along with the rest of the aileron linkage.
The spring should be just strong enough to pull the hook down and
deflect the ailerons, but not strong enough to flip the plane up
on its nose. With the addition of the fuselage planking on the top
and bottom, this thing finally looks like a plane. But wait, it
doesn't have any motor now! You took it out. Remember? Build a removable
cowl section into the outboard side of the nose. This should be
just large enough to get the motor in and out, and to get to all
the plumbing and throttle linkage required for your engine.
The finish consists of two coats of clear dope lightly sanded, one
coat Hobbypoxy Stuff wet sanded, and one coat of Hobbypoxy color
sprayed on. The color scheme is gray fuselage and wing and stab
bottoms with yellow wing and stab tops. With red: white, and blue
stripes on the rudder, and the white star with red center on a blue
circle on the top and bottom of each wing, it makes a colorful little
plane. The total weight should be 24-26 ounces. With this lightweight
and small size, the MO-1 is a real competitor, so why don't you
build one and compete?
Martin MO-1 Navy Carrier Control Line Plans
<click for larger
The AMA Plans Service offers a full-size
version of many of the plans show here at a very reasonable cost. They will scale the plans any size for you. It is always
best to buy printed plans because my scanner versions often have distortions that can cause parts to fit poorly. Purchasing
plans also help to support the operation of the Academy of Model
Aeronautics - the #1 advocate for model aviation throughout the world. If the AMA no longer has this plan on file, I
will be glad to send you my higher resolution version.
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Posted February 3, 2013