“Bearco Marine Model”

Instructions for radio control conversion


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 admiring comments.

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 usa@traplet.com 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 RCsubman@aol.com.

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 and side. 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 movement.

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 Graupner.

  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