Your “Bearco Marine Model” scale waterline model boat may
be converted into a functional and good-looking radio controlled Great
Lakes freighter. These building directions will assist you in building such a boat.
The model is constructed of styrene plastic which easily lends it
self to modifications using items out of the “scrap” box, available styrene
structural shapes and sheet plastic as well as using a bit of creativity in the
use of other parts. On of the most noticeable, and a part purchased separately,
is the self-unloader mechanism on the main deck. Remember that
everything is a potential boat part! Once completed, the six-foot boat will draw many
NOTE: where brand names have been used it is simply for
illustration purposes and in no way is a recommendation of a particular company,
a part or suitability of the part for a particular function. The description is simply to give you,
the modeler, and a starting point from which to make decisions as to the appropriate use of
a product, technique or action step.
The author of these instructions has used many items from his scrap box and miscellaneous
sources to detail his version of the freighter above and beyond the kit supplied components.
At the time of the creation of these instructions, July 2001, the author had 42 functional RC boats
in his collection, has written newsletters for various scale marine modeling sources and has
authored numerous articles on scale boats as published in “Marine Modeling International” for
Traplet Publications of England at firstname.lastname@example.org or
www.traplet.com. Also check the web site of The “Scale Ship
Modelers Association of North America” at ssmana.org and the web site of the authors home
model boat club in Toledo, OH at http://mvmbc1.tripod.com
for the Maumee Valley Model Boat Club. Inquires may also be addressed to the author at
The freighter in its most simple form will require the following radio and propulsion gear such as:
two channel radio transmitter/receiver (using the 75
Mhz. surface band), such as a Futuba unit
one standard size servo, such as a Futaba “148” size
(two if using a bow thruster per the following instructions)
one proportional electronic speed controller with BEC (battery eliminator circuit),
such as a Novak “Rooster”
a 4 mm threaded (on the prop end) prop shaft/assembly such as a Robbe or Graupner unit
a 4 mm threaded prop of at least 60 mm diameter such as Robbe or Graupner
one metal gear box from an electric model airplane, generally has two/three gear ratios and a
4 mm output shaft.
0ne “400” size motor such as a Graupner “Speed 400”
one “U” joint to connect the gearbox to the prop shaft, should be a 4 mm opening to
match the gearbox output shaft and prop shaft. Available from Robbe or Graupner
one 6 volt gel cell sealed battery which acts as both ballast and propulsion.
various Tamyia style electrical connectors for the battery, motor and speed controller.
one rudder of approximately 1 ¾” W by 2 ¾ H size.
one Graupner bow thruster unit.
The items listed above have provided the author of these
instructions the capability of operating his “Bearco Marine Model” lake
freighter for 45 to 60 minutes of run time. The electronic style speed controller allows
for smooth easy slow speed maneuverability in forward and reverse.
The “BEC” (receiver battery eliminator circuit) circuitry allows the
radio receiver to operate from the main battery rather than the smaller and
separate four “AA” cell radio receiver battery pack.
The use of a prop shaft with a 4 mm threaded prop end allows the
use of various prop diameters. Using a prop shaft with this screw thread
configuration increases the number of prop blade choices of three or four
blades. Props that use a pin or “dog” to secure the prop are more limited in
choice of props and blade numbers.
The boat is constructed following the basic construction
techniques applicable to the static version. It is vitally important
to note that the sides of the boat hull should not be cut down as low as for
the static model.
If that is done the boat will have insufficient freeboard
(height of hull sides) to make it safe for on the water
use. The prototype boat build to prove these instructions
has a deck edge bulwark of 6 ½” at the bow, a main deck
area height of 4 ½” and a stern height of 5”.
To establish cutting marks for those height
dimensions place the hull on a level surface and make
a marking jig. That would consist of a block of wood that
supports a pencil at those various heights.
Use the main instruction booklet to establish
the horizontal length of the bow as well as the horizontal length
of the stern bulwarks (sides of hull). Or if you so desire form the shape
of the bow and stern according to reference pictures you have found in your research.
In no case should you make the hull edges lower than 4 ½ inches.
After the hull sides have been cut down to the shape of a great lakes freighter you will
then install the deck. Follow the instruction in the main instruction booklet. The author of
these RC instructions makes the suggestion that the hatch covers be made from
thin strips of plastic. Further realism can be created by making the small
hatch edge/combing reinforcement vertical gussets as well as adding small lift rings of wire.
In planning the building steps you do need to keep in mind that interior access must be
provided for. This is to allow access for the mounting and servicing of the motor, radio, battery
and other RC parts. The easiest way to gain access is to cut open the roof of the stern
superstructure as well as the bow deck area. A separate piece of plastic sheet
(provide by you the builder) will be then used to create a roof or supplemental
bow deck area, which should be attached with a couple of screws to prevent loss.
The boat should ride at a realistic height in the water,
which would be as in a loaded condition meaning that half or more of the hull
side height is below the water level. This is achieved in one of two ways.
If you build the boat more or less as a static model you will have one
long 6 foot boat that is water tight and will need ballast for that entire volume of hull.
That amount will be rather significant and if so, that ballast
will need to be in removable form as the strength of the plastic hull will be
insufficient to support great amounts of permanently fixed ballast.
The alternative and recommended way is to partition the
boat into three parts. A watertight bow
section of approximately 10 inches length, a center section (the majority of
the hatch covers) would be designed as free flooding and the stern would be
another watertight section of approximately 15 1/2 inches in length.
If this manner of construction is used the
watertight bow and stern will support the free flooding center section (you
will cut a number of openings in the hull bottom) and removable ballast will
only be required for the bow and stern rather than the entire boat! If this
method is used approximately 1 to 1 ½ pound of ballast is needed in the bow and
the stern requires 5 pounds in addition to the battery and motor as set
up in the prototype model boat.
It is suggested to
use one-pound rectangular lead weights used for melting into smaller fishing
weights. If this free flooding method
is used, the hull bottom will have to have a number of holes cut in it to allow
water to flow in. You should cut four
rectangular shaped openings (approx. 4” X 6” in the bottom of the free flooding
middle section of the hull. The
air displaced by the water entering
into the hull will need to flow out of the top (main cargo deck).
This can being achieved by making one of the
hatch covers in an open position as though being lifted by the traveling hatch
crane. Two of the hull bottom water
entry openings should be near where you plan on placing the watertight
bulkheads. That location of two of the
hull bottom openings will allow hand access for installation of the bulkheads
as you will be able to reach through the top deck openings in the bow and stern
as well as from the underside of the hull.
When ready to launch the boat, place the boat in the water, the center
section fills with water overcoming the buoyancy of that section. Needed
ballast is positioned in the bow/stern and the boat is ready to run.
When removing the boat from the water simply
pick it up and the water flows out of the bottom.
Easy and practical.
With the above in mind lets proceed with the radio
controlled version of the boat.
Gather the above suggested items such a the motor, gearbox
etc. with which to make the boat into a powered radio controlled version.
Good practice dictates that you break in the
motor by first running it for a minimum of 30 minutes, 15 in forward and 15 in
reverse. Assemble the gearbox by
choosing your gear ratio you want. The
prototype boat in the pictures runs with a
ratio. Make sure the gears are free and
easily turned. Lube the motor and
gearbox with WD-40.
The prop shaft in the sample boat was cut down in size to
produce one of approximately 4 1/2 inches in length.
This was done by removing one of the bearings,
cutting the prop tube and
reinstalling the bearing. Check for free
rotation and add silicone grease lube to the prop
tube. The propshaft will
need to be cut down a corresponding amount. Silicone grease is suggested as
the lube choice and is
available in small tubes , which are generally available
at Radio Shack. Some modelers use additional
oiling tubes soldered to the prop
tube. This time consuming
method has been found unnecessary if the
silicone grease is used.
Assemble the motor/gearbox combination, the U-joint and the
prop shaft to get an idea of the length of the assembly. To make a mounting and reinforcing pad for
the motor and gearbox cut a piece of
modeler’s plywood to fit the stern hull bottom section of the boat. This does not have to be a close fit but simply
acts as a hull bottom reinforcement and provides an easy place to mount other
items. The motor in the prototype boat
was mounted using a metal electrical conduit strap. This inexpensive item is available for approximately 20 cents and
is a very useful and versatile motor mount.
Add two wooden blocks to lift the motor and to position it at the angle
of the props shaft assembly.
Next determine where the prop shaft will be positioned to
exit the bottom rear of the boat.
Remember to check the pictures of the prototype boat for positioning
information and to use your own prop to determine exact location. NOTE:
the prop should be close enough to the hull in both a vertical and
horizontal position to allow room for
the rudder to be hung/mounted behind it.
It is critical to allow enough room in the stern area for the rudder and
linkage to connect it to the rudder servo.
The next step is to position the rudder.
Make sure it is centered side to side
and that it appears vertical when
viewed from the rear
The prototype boat uses a unique
rudder to servo linkage.
Typical practice is to use a
rudder control arm positioned at a 90-degree angle to the centerline of the
boat to move the rudder. This has been
dispensed with and in the prototype boat the linkage points straight ahead down
the centerline of the boat. The rudder
servo is glued with CA instant glue to a block of wood or foam to bring it to
the height of the rudder control arm. The servo is positioned ahead of the
rudder and has a custom made arm of plastic attached with screws to the round
servo wheel. This custom made arm (see
picture) is slotted down the middle so that the side-to-side movement of it
allows a screw with a washer under it
to slide in the long slot. Works well
and this principle can be applied to other boats and applications. The rudderpost, where it enters the interior
of the boat, should be reinforced with one of the two part epoxy tapes that
create a sort of stiff putty after being kneaded together.
You should consider making a boat stand. The prototype boat uses a couple of blocks
of foam to support it and to keep the hull and vulnerable prop and rudder clear
of any surface that could damage/break them.
See the prop location in the
pictures, which shows that the prop does hang down below the flat bottom of the
boat. It will be very easy to bend or
break a prop blade off (off course you carry a spare?) so support the
boat. Also remember that during the
remainder of the building process leave the prop and rudder off as
often as you can to prevent breakage. The author of these instructions stores
his boat in the shipping box. Add some
foam to the bottom to support the boat, keeping the prop and rudder from touching
the bottom of the box and add more foam to the ends to prevent back and forth
Now is the time to create the two inner watertight
bulkheads. At this stage in building
the boat has had the hull sides cut down, the main deck installed, the four
water free flood access holes in the hull center section formed. To prepare for
the bulkhead installation disconnect and remove the motor/gearbox and the “U”
joint from the prop shaft as well as the rudder. This will allow room in which
to work to install the bulkheads.
The boat has the four access holes cut out of the hull
bottom as well as having the stern cabin top and bow deck area cut out which allows easy hand and arm
access to the interior of the boat.
The prototype boat had measurements taken of the exterior dimensions of
the hull and that transferred to light cardboard to create a template for the
inside of the hull. It will be
necessary to cut and fit the template several times till there is a good fit.
Make one template for each end as the ends (bow/stern) probably vary in
internal dimension just a bit. These
templates and ultimately the actual bulkheads will fit through the deck level
openings (in the bow or stern) or through the hull bottom access holes. To
construct the bulkheads use sheet plastic cut to the inside dimension of the
hull per the dimensions of the templates.
Cut some scrap wood or plastic to make reinforcements along the edge of
the bulkhead. Mount the bulkheads
checking all four sides for contact to the hull and deck. Glue in place and then add the reinforcing
pieces to strengthen the bond between boat and bulkhead.
Now is an ideal time to test the boat and bulkheads for
leaks! Do so prior to continuing on
with the building. Of course install
the prop shaft and rudder or temporarily seal those holes.
Is the boat watertight?
You did make one of the hatch
covers removable to act as an air vent?
A good safety measure, to insure flotation, is to add a thin layer of foam to the
underside of the main deck in the free flooding area. On the prototype boat a spray on expanding foam, which was
applied through the bottom access holes.
It was determined that with this method it was hard to control the depth
of the foam as well as the side-to-side
coverage of the expanding foam.
Additionally it was sticky and when trimmed down to create a level
surface lots of foam particles were
made. A better method would be to cut small rectangular
slabs of foam from a larger sheet of high density (blue or gray) foam. These pieces can be slid through the access
holes and glued in place.
Motor and prop shaft installation.
At this stage of construction the boat should be water
tight and soon capable of floating in an stable position after ballast is
added. The gel cell battery as shown in
the building pictures acts as a significant percentage of the ballast in the
prototype boat. Add all of the motors, rudders and drive battery to the boat
but leave out the radio so it does not get wet if water gets splashed into the
interior during ballasting. Remember to
position the battery so it does not slide.
The builder of the prototype boat positions the battery and removable
ballast weights using various pieces of glued in foam. Have your ballast ready
to add to the boat. Leave the bow and
stern top access openings open. Let the
boat settle to its waterline as it takes on the water ballast. Start adding small amounts of ballast to see
how the trim of the boat is affected in a front to back ride height. Most lake freighters seem to ride higher in
the bow than the stern. Also check for
side-to-side balance. Add the bow and
stern superstructures and check the ride height again. When satisfied hook up
the radio and go for a test run! The
boat constructed as in the preceding instructions will be light, strong and easily
modified as needed. The boat as built
weighs approximately 6 pounds. The
addition of battery, radio receiver and ballast brings the operational weight
to approximately 13 ½ pounds.
The prototype boat also had a bow thruster added. The boat as built with just a rudder is
quite capable of easy turns and maneuverability. The author of these instructions wanted more real type operation,
which is the reason for adding a bow thruster.
With such a unit the boat can be turned in its own length when stopped! Such units are available from Robbe or
If you choose to add a bow thruster test fit it
to the bow area in the watertight bow area.
The sample boat has it installed about 8” back from the bow. Cut holes down low in the hull side to accept
the water transfer tube. Cut of any
excess tube length and test the bow area for leaks. A two-channel radio was used on the boat necessitating the use of a “Y” harness connected to the radio receiver receptacle for the rudder servo. One leg of the “Y” harness accepts the
rudder servo lead while two 24” servo extension cords were connected to the
other leg of the “Y” connector and lead forward through the stern watertight
bulkhead. The extension cord was glued
to the underside of the deck prior to installing the foam floatation
material. Chances are that the joining
connection for the two extension cords will occur someplace in the free flood
area. Therefore waterproof that
connection. The author used the liquid
plastic dip material that is used to make rubber like handle grips on tools.
The extension cord is lead through the forward watertight
bulkhead. Another servo is placed in
the bow area to activate switches that will control the thruster motor. A small battery pack of 6 “AA” batteries was
added to power the thruster unit. The
author used four micro switches ganged together in pairs and activated by the
servo arm. Set the servo to activate a switch group when the
rudder swings completely to one side. A
swing of the rudder to the right to turn the boat right activates the front
servo to turn on the thruster sending a water jet to the left/port side thus
moving the bow to the right. With this
set up the boat (when stopped) can be rotated on its axis such as when turning in place in a harbor or a
river! Try using the prop in partial
forward or reverse and see what maneuvers you can complete.
Thank you for choosing a “Bearco Marine Model” and we wish
you good luck and many happy miniature voyages! Should you have questions please contact the author of these
instructions and the developer of the RC conversion. Contact George A. Snyder in the Toledo, Ohio area at RCsubman@aol.com.
Form GAS-5-01 rev 6-14-01