• How to Assemble a RC Model Boat

    To build and assemble a R/C boat demands a few steps and a couple of different things. This article of the site intends, in a comprehensive form, to deal with them all. At the end your lecture, you should have a guide, as complete as possible, on how to build and assemble your boat.

    The main segments to be mentioned are:
    • Hull
    • Engine
    • Drive train/rudder
    • Electronics


    Hull

    Building fibre glass hulls

    The following items describe each necessary step to build a fibreglass hull, from making the mould over a plug until finishing the hull itself. It is not an easy task but you are willing to try, these tips from Gaucho will help the job. We use polyester resin and fibre cloth, although mat could be used as well

    For easy understanding, we offer some definitions of terms used in this article.

    Fibre cloth: glass threads woven in a cloth. Unlike the mat, the threads don't get loose when used. The finish has better appearance than the mat, although the latter is stronger.

    Gel: mix from clear resin with 1% cobalt, titanium dioxide and ground glass. This is the layer that will be apparent and that will give the finish for the work.

    Industrial talcum powder:
    used to thicken the gel

    Mat: Fibreglass joined together that, covered with resin, gives strength to the hull. The reference numbers (6 oz, 7 oz, ...) refer to the weight for square foot of the mat. The higher the number, the thicker the mat.

    Micro balloons: small glass spheres that, mixed with resin, reduce the weight and increase the resistance of the mixing.

    Polishing compound: Used to polish the painting or the resin.

    Polly Vinyl Alcohol: Alcohol used as a mould releaser (taking off the hull from the mould)

    Resin: liquid that is sprayed over the fibre glass and, when cured, makes a strong compound. It can be:

    Polyester: more often used because of more reasonable price;

    Epoxy: more stable than polyester, has less tendency to shrink when cured. However, it is more expensive;

    Catalyst: resin (polyester or epoxy) to what the catalyst was aggregated to start the cure

    Wax:
    special wax that has a characteristic of preventing the hull from sticking to the mould.

    Wet sand: a sand paper that is wetted to be used. It has a lot of different grits (100, 150, 200, ...) The higher the number, the fine the grit.

    Special care: always use adequate protection to work with resin, whether it is epoxy or polyester. Use rubber gloves, protect the body-exposed parts and work on a well-ventilated area. When curing, the resin produces heat. Prepare only small quantities each time.

    Steps:

    There are 3 steps on a fibreglass hull building.
    • Plug: original part, from which the mold will be made. The part already exists, a mold copied from a hull, or the plug must be build to serve as a base for the mold.
    • Mold: it is the negative of the plug, the plug cavities are raised on the mold, and vice versa. From the mold will be extracted the hulls. If you take good care of the mold, it will last for long and many hulls can be done from it.
    • Hull: final result of the work, extracted from the mold


    Plug
    • The plug must be done on wood or Paris plaster and have a perfect finish. Remember: all the imperfections from the plug will be transferred to the mold and from it to the hull. It takes a lot more work for correcting the defects of each and every hull you made than to spend a little more time making the plug and the mold and having not to worry about the hulls anymore.
    • No curve with less than 0.03" of ray
    • To lessen the de molding, there should be no angle with less than 2.
    • After finishing the plug or if you are using a hull as a plug, fill all the imperfections with resin mixed with industrial talcum powder and titanium dioxide.
    • Wet sand with # 120.
    • Apply a layer of 7.5 oz mat, removing all the bubbles.
    • Sand the surface.
    • Wet the surface with polyester resin to fill the imperfections
    • Wet sand starting with # 300 going to # 600. After each wet sanding, wet with resin and sand again.
    • Apply 5 layers of wax, polishing each layer.
    • Apply 2 layers of PVA


    Mould
    • Spray a layer of mould resin (pure, with no aggregates), with 0,02" thickness. (2 or 3 layers, perpendicular each other, without waiting the cure of the former layer.
    • The last layer must have a strong and contrasting color. In the future, the mould wearing will be apparent because the inner layers will show under the last one. Besides, the strong color will make easy the visual inspection for the correct gel application.
    • Spray a layer of mould resin (pure, with no aggregates).
    • Apply a layer of 7.5 oz cloth over the gel.
    • Cut the cloth on the corners and curves for it to settle over the mould.
    • Wait for the cure of this first layer.
    • Ad resin, removing all the bubbles.
    • Apply successive layers of cloth + resin, until a 0,2" thickness is reached. As a rule of thumb, the mould should have 3 times the thickness of the finished hull. For extremely thin hulls (like sail boats, for instance) this number can be bigger.
    • Fix the mould glassing to it pieces of wood that will give stiffness and prevent bending.
    • The mould should be cured on the plug for 24 hours.
    • After 24 hours, take the mould off the plug and wash it throughout
    • Wet sand, starting with # 400 and going through # 600.
    • Polish with # 2 polisher.
    • Put it 5 layers of wax in sequence, polishing each layer.
    • Apply 2 layers of PVA;
    • Apply 2 layers of wax, shinning each one


    Hull
    • Apply 2 layers of wax on the mould.
    • On corners and angles apply an extra layer.
    • Apply gel (preferably with pistol) with 1/64 thickness. If you wish a white hull, mix gel with titanium dioxide, if you want a colorful hull, don't use titanium and mix the desired pigment to it.
    • For laminating (to apply the cloth) the gel must be sticky but not enough to stain the finger.
    • Apply the cloth uniformly, covering all the mould curves and unevenness.
    • Apply the resin with catalyst, wetting completely the cloth smoothing the bubbles.
    • Use a roller.
    • Wait the cure of each layer before applying the next.
    • Correct the flaws of the first layer with mat or resin + talcum in a proportion of 1:3.
    • Don't use mat on tight curves. Use cloth, to prevent from bubbles. Ad mat, if necessary for reinforce.
    • Don't apply too much resin. This only increases weight without increasing the strength.
    • If you need an extremely light hull but also very strong, mix micro balloons to the resin. Reduces weight, increases resistance and ease sanding.
    • The spots hard to reach with cloth or mat (the strakes, for instance) may be filled with resin until almost even with the bottom of the hull and reinforced after that with cloth or mat.
    • Use heavier cloth on the bottom of the hull. The sides and deck may use light one.
    • Let cure for 24 hours.
    • Taking off the mould:
    • flex plastic under the flanges;
    • compressed air or water under the edges;c. use a rubber mallet on the hull and on the mould;
    • ice under the hull.


    Painting

    Preparing the hull for painting is more time consuming that painting itself. But it is mandatory for a well-done and long lasting work. Follow the steps, as per Gaucho's recommendations:
    • Planning: before starting working, make a drawing of the paint you intend to do. Use colors, for seeing in advance how the combination you imagined will look.
    • For a better job, take off the engine and all the hardware not fixed to the hull. This makes the job easier and increases it's quality.
    • Wash the hull with neutral detergent, inside and outside and let it dry completely.
    • If this is the first paint of the hull, it could be necessary to clean it with acetone, to remove any wax residue that could be left. If this is the case, after acetone apply solvent for PU paint, letting it dry thoroughly.
    • Wet sand with # 320 grit.
    • After sanding, wash with alcohol and let dry.
    • Apply primer as a first layer. As the recommended paint is Polly Urethane, be sure that the primer and solvents used are compatibles with this kind of paint. The vendor on the paint shop will know the best products.
    • Do not use spray paint. Although the ease of application, it doesn't withstand gasoline.
    • Use high-pressure pistol at 12 inches from the hull.
    • Apply primer.
    • After the primer has dried, wet sand with # 400 and start painting.
    • After each layer has dried sand the paint. Start with #400 and go to #600.
    • After this, the basic paint of the hull, the one that is the prime color and over which will be painted the details you planned, is finished.
    • Let it dry for 24 hours.
    • Make the contours of the designs that will be painted over the initial paint, using masking tape. Attention: too complicate a drawing may demand airbrush instead of air piston to be done.
    • Protect the parts that will not be painted at this stage.
    • For painting, take the same care as before.
    • Use more solvent than you used on the basic paint, to prevent "steps" on the paint.
    • After dry, and if your design demands so, use again masking tape to make the contours of the new layer. Remember: each different color demands a new step of painting.
    • Go through the steps already described, until finish the painting as planned on your original drawing.
    • For better protection, use transparent enamel over the paint, compatible with PU paint.
    • Let it dry at least for 24 hours before starting the engine.


    Assembling

    Stern reinforcement

    The transom is the place where the strut and rudder will be attached and, because of this, will be responsible for supporting the all the force from the engine to the hull. A fibreglass reinforcement is essential at this place. To do this, make a mould of the stern and transfer it to a piece of 1/8 plywood. Glue this plywood into the hull and let it dry. (Picture from a Dom Mauro's boat)



    Engine rails. They are those 2 wood rails that run parallel to the hull bottom and to which are fixed the engine and the radio box. The usual distance between them is 5 inches, measured at the inner faces. This is the measure for the commercially available engine mounts and the external dimensions for the most used radio boxes. A perfect join between the rails and the hull is of utmost importance: they must be glued with fibreglass and resin, for a strong bond. Use the same technique you read on the chapter of how to make your fibreglass hull.

    Material: 5 to 7 layer plywood

    Length: 2/3 of the total length of the hull or till the wall that joins the deck to the hull, when present.

    Height: 2 inches.

    Stuffing tube. A stuffing tube is a brass tube the goes trough the hull and runs the flex cable from the engine to the propeller shaft. There are two types of this tube: with or without a Teflon liner. Although, apparently, the liner tube seems to offer less drag, r/c boaters have been reported that, under race conditions, the Teflon has a tendency of melting and lock the flex cable. So, the indications bellow refers to a non-teflon tube.

    Diameter:

    outside: 5/16"

    inside: 9/32"

    To facilitate mounting the stuffing tube and it's replacement when necessary, instead of gluing it directly to the hull, put it into another brass tube, with a internal diameter equal or a little bigger than the outside diameter of the stuffing tube. The outside tube (11/32 diameter should fit) then, will be glued to the hull with fibreglass and resin. Mark the point where the brass tube is to go trough the hull, in such a way that the inner tips will be aligned with the engine shaft. Cut a rectangle at the bottom of the hull as a passage for the tube. Fix the tube on the correct position with fibreglass mat and resin. Protect the outside part of the cut with tape, to prevent the resin and mat from dripping. After dry, sand and smooth the fibre on the outside. Put the stuffing tube into the external brass tube. A few drops of Super Bond will assure that the stuffing tube will be fixed to the outer tube. When time comes to substitute the stuffing tube, rotate it against the outer tube, to free the Super Bond, take the stuffing tube out and fix the new one the same way.

    Note: the curvature necessary to run the flex cable from the engine to the prop shaft will be present, only, on the stuffing tube. The outside tube should have, at the most a very mild curve, in order to allow the stuffing tube to go trough it.

    Picture from a Paul Govostes' boat



    Engine

    There are two engine types we are dealing here. The ones already prepared for r/c boating and the ones removed from weed eaters and that must be prepared for that purpose. The first type includes weed eater engines already prepared and special engines, made on purpose. Mounting them to the hull is all that it takes. The second group demands a little bit more work. They are air-cooled engines, surrounded by huge plastic material used to direct air over the cylinder. Using them demands taking off all this plastic stuff, useless in a water-cooled engine and that only ads to this volume and weight. The pictures bellow shows an engine before and after taking of this plastic and they give a good idea on what should be done. Take care, when cutting off the plastic, not to cut off any of the fixing devices for the engine and its accessories, the coil, for example.



    I thought I should say a little bit more about this subject, be more specific. And Mike Gillman, in a post on Jim's board - where else? - said everything that's important. He was dealing about a air cooled to air cooled conversion. I quote him:

    How do I convert a weed eater motor to go in a boat?

    Get a Homelite trimmer, take the shaft off, save the flex inside the shaft as you will cut it and use it later. Cut off the plastic shroud except by the pull start, leave that to direct the air flow over the cooling fins. Save the throttle cable and the kill switch as they can be used in a boat too. Cut the black plastic fuel tank support so you can bolt on a piece of angle alloy for a front mount and use another piece of angle alloy and a U bolt across where the shaft was for a rear mount. Cut a piece of the shaft tubing to slide in the end so when you tighten the U bolt it doesn't just crush the plastic. Open the muffler up and take out the screen, weld the hole closed and drill 2 new holes in the top 1/2" each or one 3/4". Follow Jim's hop-up tips from the main page and have fun.
    Anything I forgot guys?

    Mike Gilman


    Fixing the engine to the hull

    Before fixing the engine to the hull, you need to adjust the CG of the boat. What is CG: center of gravity, the point over which the boat is on balance, in equilibrium. If you lift the boat by the sides of the hull, using one finger from each hand, the CG is that point where the boat balances fore to aft. This point will determine the attitude of your boat on water and is of utmost importance: too forward and the boat runs with the bow deep into water, will be hard to plan and get speed; too far back and the opposite occurs: a high lifted bow makes the boat unstable, rolling on the sides and sliding on the turns. As a rule of thumb, this point should be between 27 - 30% of the total length of the boat, measured from the bow to the transom. In other words, on a 50" boat the CG should be between 13.5 - 15", measured from the transom. Boats with very powerful engines may operate with the CG more forward. In this situation, 32% should be a good starting point. Of course this measurement should be taken with all equipment installed - engine, transmission, radio, rudder, gas tank and so. The heaviest item is the engine and, because of this, it's the most important component for adjusting the CG. This is one of the most important tasks when assembling a boat because fixing the engine only can be done after adjusting the CG.



    How to do it:
    • Mark, on the sheers, the points where the CG is intended to be;
    • fix all the components (except the engine) to the hull, in the position they are supposed to be;
    • put the engine, plus the pipe, into the rails;
    • check the CG: if after the correct point bring the engine back, otherwise bring the motor trough the bow. Repeat the operations until the checked CG coincides with the ideal.
    • mark the motor position and the holes for fixing it.


    Always use rubber mounts to fix the engine to the hull, otherwise the vibration will destroy the hull and/or the radio. If your engine didn't come with the supports and you don't want or can't buy them, make your own. Look at the picture bellow the initial stage of making supports for a Husqvarna engine. Check your motor for the best supporting points. It's important that it is supported at front and back, for a good fixing. Remember that, anytime you will need to take the engine out of the hull. Make supports that allow the motor being taken off with a minimum of additional disassembling. Use good quality aluminum: easier to fold, light weight and resistant. For the rubber, use automotive cushions: easy to find, gasoline resistant and cheap. Remember that all this stuff is supposed to fit into rails with 5" with.

    Attach the engine so the drive will be as close to the bottom of the hull as possible. If you are using a drive, the stuffing tube and the flex cable run parallel to the bottom of the hull. If so, the engine has just a little inclination. But if you are using a strut for the prop shaft, the stuffing tube and the flex cable will go trough the hull in a acute angle and will make a curve towards the strut. In that case, the engine will have a greater inclination in a way that it's shaft will be perfectly aligned with the stuffing tube and the flex cable. This alignment is important. Lack of with causes drag and wear on the stuffing tube and/or the flex cable, besides putting a strain on the engine bearings.

    Wayne Mills made the bellow drawing and authorized me to use it. It shows, precisely, how to connect all the accessories on an engine. Thanks Wayne.



    Drive Train/Rudder

    The drive and rudder system of your boat consist of:
    • square drive or collet;
    • stuffing tube;
    • flex cable;
    • ferrule;
    • strut;
    • propeller shaft;
    • drive dog;
    • propeller;
    • bushings and washers;
    • tail nut;
    • rudder(s)


    All those parts are described on the Definitions segment of this site. Take a look to familiarize yourself with the names used.

    Even before getting authorization, I decided to use this drawing that Ron Frank posted at Jim's site because it illustrates, precisely, the assembling of a drive train.



    Square drive or collet. at Shark Racing we use square drive exclusively; our experience with collet was not the happiest. At work, the effort to transmit the engine power makes the flex cable contract. If using a collet, where both tips of the cable are fixed, it's necessary to leave a gap between the prop and the strut, to take care of this. Because of it's design, where the tip close the engine is free, the square drive doesn't need this gap. Besides, mounting and disassembling the flex cable is easier.

    After fixed on the engine shaft, the square drive should be 1" (2,5 cm) from the tip of the stuffing tube and aligned with it.

    Stuffing tube.
    Above, you have seen how to fix the brass tube that will support the stuffing tube. Remember that it should do a smooth curve to the strut and end close to the transom or till the ferrule. At the engine side it should end 1" (25 mm) from the square drive.

    Flex cable. Your better alternative is buying a 1/4" flex cable on a weed eater seller. The cable has 2 square ends and is good for 2 flex cables for your boat. Before cutting it, check carefully the length, taking in account the square drive and ferrule lengths. After marking the part to be cut, clean it and cover it with solder, to prevent the wires get loose. Use the Dremel cutting wheel or a metal saw.

    Ferrule. The first rule to a good solder on your flex cable:
    • Clean it.


    Second rule:
    • It's not good enough. Clean it again.


    Start heating the cable and, with a wire brush, clean all the mess that come from inside. Let it cools of and use acetone or lacquer thinner to complete the cleaning job. If you are using a propane torch, heat it like porcupines make love: carefully.

    Tin the cable by heating it with and applying flux. Don't use too much, just enough to the solder to stick to the cable. Apply a small amount of solder, enough to cover the cable with a thin layer, after what the cable should be silver. Take the ferrule and clean it inside. Again, acetone or lacquer thinner will do. Mount the ferrule on a prop shaft, clamp the shaft to a vise and heat the ferrule. Do not concentrate the heat in just one spot, go all the way around. Put a small amount of flux into the ferrule and thin it with solder. Put the cable into the ferrule. If properly heated, the cable will go all the way down. Don't use to much heat or the cable will be brittle. Let it cool, it should be good.

    Strut. Some degree of adjustment must be provided for height and angle. Adjust it so that the prop shaft is level with the keel, for a surface drive. This is an initial setup. On cats you may try 1/4 to 3/8 over the sponson, on monos 1/2 to 5/8. We only use stainless steel screw on our hardware, because we use our boats on salt water. Even if this is not you application, be sure that s.s. will give you less problems and service. Mark the place for fixing the strut, make sure it is on level, and make the holes with a drill 1/64" (0,5 mm) bigger than the screws to be used. Fix the strut without using excessive force.

    Prop shaft.
    The prop shaft should turn freely into the strut. Any drag means unnecessary use of engine power. If necessary, adjust the clearance.

    Drive dog. The drive dog is that 2 "ears" part which is fixed to the prop shaft by means of set screws. The "ears" engage to the prop and transfer to it the rotational movement of the engine. After marking the position where the drive dog will be, file a flat spot on the prop shaft for the set screws.

    Propeller. It is the most obvious part of the drive train. Adjust the strut so the prop shaft will be 3/8" (9,5 mm) over the sponsons (cats) or levelled with the keel, for monos. The distance from the prop to the transom should be 4 1/4 to 4 1/2 inches. Once again, this is a starting point, you should try other adjustments and discover which one is better for you.

    As many (if not all) questions in this hobby, there is no a single, unique answer to it. A prop far from the transom, besides getting clear water, helps correcting excessive lift at the bow because every time this happens the prop and shaft will be deep in water, in such an angle that tends to lift the transom. BUT - there is always a "but" - this also may cause porpoising. So, use the strut from the reputable manufacturers and experiment from that.

    Prop balancing is of the utmost importance. An unbalanced prop causes vibration that, depending on the extent, can damage the boat's drive train and cause interference to the radio. If you have no access to a commercially available prop balancer, improvise one with two pieces of wood and two razor blades, that will support the prop shaft. Fix the prop on the shaft and let it turn freely on the razor blades. The heavier blade will turn down. Mark that blade and remove material. Always take material from the back side of the prop, that is, the side closest to the transom. A tool like a Dremel makes the work easy, but files can also be used. Works by steps, taking off just a little material at a time and always checking the balance. After balancing, the prop should be polished with a fine grain sandpaper (250 first, 400 afterwards) and sharpened at the leading edge, which should improve performance. After polishing and sharpening, recheck the balance, redoing if necessary.

    There is an old saying between R/C boaters: "If it (the prop) isn't cutting your finger, it's not sharpened enough". Sharpening the propeller helps reduce prop walk. The sharper, the better. Unless you have expertise, never use big electric tools to sharpen a prop. It's more prudent to use wet sandpaper and time. Protect yourself against the dust that results from the process. Copper-Beryllium props produce a residue dangerous for your health. The final polishing can be done with a Dremel or 400 grit wet sand paper. The material should be removed from the prop side near the transom (convex side or drive dog side). When sharpening, create a transition area with more or less 3/8" from the sharpened edge, so there will be a very gradual ramp till the rest of the blade. The concave side - working surface - must be cleaned but must not have it's design altered, to do so would change the pitch and cup. Cooper-beryllium props are softer and easier to work with and are available in a greater variety of diameters and pitches. Stainless Steel props are stronger but more difficult to work with.



    The prop to be used on each boat depends on the type of the hull, drive train, engine and even the way you drive. It's impossible determine the best prop without testing. There are, indeed, general indications as a starting point, from where you must do your testing to found the best prop for your boat.

    Below, some recommendations picked from Jim's board. They came from very experienced boaters and we included our experience too. We did not mention specially re-worked props because they are out of the scope for beginners.

    Hull: mono or cat

    Surface drive

    Engine: gas, 25 to 35 cc

    Recommendations: Octura x-467, x-470, x-472, x-572, 1475

    Prather: 270, 275, 280

    If you want to go deeper on this subject, go to the http://www.modelpowerboat.com/forum/Propellers page.

    Bushings and washers. The prop shaft runs between bushings or bearings. Those bushings must be perfectly aligned and with enough clearance (but not too much) for the shaft turning with little drag. At the tips of the shaft, between the ferrule and the strut and between the strut and the drive dog use teflon washers. They absorb stress on the system and doubles as a very easy way of adjusting the length of the cable.

    Tail nut.
    It is the last part of the drive system. It holds the prop on the shaft. Between the tail nut and the prop place a piece of fuel tubing that will be compressed by the tail nut and will act as a absorber and locker for the nut. We prefer the type which is hold to the shaft with set screws, although there are threaded shafts to which the tail nut is screwed. Shark Racing has the two types.

    Rudder. The rudder design recognized to offer the best performance is the wedge type. Short and thin is the best design. It must not be installed too far from the prop. Too far to the back, it becomes too sensitive, too far to the front reduces turning efficiency. The best location is where the front edge is even with the front edge of the prop to where the front edge of the rudder is 1/4" behind the trailing edge of the prop. In other words, the leading edge of the rudder should be between the leading edge of the prop to 1/8" (6mm) from the trailing edge of it. For cats, the rudder can be mounted closer to the transom.

    The leading edge should be sharpened and its bottom rounded.

    For less drag the rudder should be 5/8" (16 mm) under the propeller blade and 2 to 2.5" (5/6 cm) from the transom center. For better turning control it could be a little deeper than 5/8".

    Trim Tabs. Metal fins at a 90 angle, affixed to the transom to adjust the boat's attitude on the water. The bigger the angle, the more the transom lift. On more complex assemblies, 2 pairs are used. They may be made from #16 stainless steel (if you want them flexible and adjustable) or on 1/8" aluminum. Mount them (the external ones) at 1/16" from the bottom and between 1/2" to 3/4" from the outside edge.

    Electronics. The radio system gives the hobby its name: radio controlled boats. It is a system that allows, from the shore, turn the boat, open and close the throttle. There are 3 types of radios, according with the way they transmit signals to the boat:
    • AM: amplitude modulation: the radio wave length varies and this variation encodes the information to the receiver. It is the radio that has the best range but, at the same time, the one more prone to interference;
    • FM: frequency modulation: the wave length is constant, the frequency variation encodes the signals. Has less range but is less prone to interference;
    • PCM: it is a FM radio that, additionally, the signals are encoded with a specific code. With this, they are almost immune to interference, because the receiver only recognizes as genuine signals the ones with the transmitter code. On a price range, AM radios are cheaper, PCM the most expensive.


    To allow more than one boater using the radio at the same time, they are capable of transmitting their signal in different frequencies within it's bandwidth, according to the crystal they have at the moment.

    There are several frequencies range used on R/C hobby (Brazil and USA, Europe use others as well):
    • 27 MHz: for boats and cars;
    • 36 MHz: (Australia);
    • 40 MHz: (Australia);
    • 72 MHz: only for planes;
    • 75 MHz: only for boats.


    Within each bandwidth there are intermediates frequencies, that permitted the simultaneous utilization of several radios at the same time. It is advisable having more than one crystal set, so you can drive your boat with your friends. On Technical chapter, Radio Frequencies Table, we present the available frequencies.

    Besides, radios can have 2 or more channels. Each channel controls a different servo, that's why your boat needs 2 channels: throttle and rudder. FM radios are usually found with 3 channels minimum, even if the third channel won't be used. In a ascending price table radios are becoming more and more sophisticated, with digital controls, trims for each channel, reversing servos, memory, and so. The sky (and your wallet) is the limit.

    All the above radios can be found in two types: pistol and stick. The pistol radio has a trigger, which actuates the throttle and a wheel for the rudder. This is the universally adopted type for cars and boats. The stick radio, as the name implies, has two sticks, one for the throttle (up and down movement), other for the rudder (left and right). The airplane people uses this type almost exclusively because each stick can provide, at the same time, left and right, up and down movement, which gives 4 channels with only 2 controls. On boats they are more often used on sail boats, where the trigger is not very appropriate.

    The radio system of your radio consists of:
    • transmitter;
    • receiver;
    • servos;
    • batteries, and
    • additional devices for safety.


    The transmitter stays with the pilot. It sends the signals that will be decoded on the receiver and will command the servos to actuate the rudder and throttle.

    The receiver is in the boat, protected (hopefully) from water into the radio box. It decodes the signals from the transmitter and commands the servos.

    The servos are little electrical motors that rotate by receiver command. This rotation is transmitted to cables or rods that turn the throttle or rudder.

    The batteries supply electrical current for the system to work. There are two sets: one goes in the transmitter, the other in the boat. In some types of radios (AM normally) you can use normal or rechargeable batteries. We do prefer the rechargeable ones: given time they are cheaper as, to be on the safe side you must use a new set of non-rechargeable batteries each day at the pond. In the transmitter, the quantity of batteries to be used is determined by the design of the batteries holder, on the receiver one can use 4 non-rechargeable batteries (4 x 1,5V= 6V) or 4 or 5 rechargeable cells.

    With 4 cells you have 4 x 1,2V=4,8V, with 5 you will get 6 V. Whenever possible use the higher voltage, the speed and torque on the servos will be higher, which is important when pulling a throttle against a strong coil or turning a rudder on a speeding boat. If using a BEC receiver (very often used on cars) the receiver can take a 7.2 V pack used in cars because a internal device sends just 6 V to the servos. Besides, always use a battery pack with the biggest amperes available: more amperes = more time of use which is an additional safety margin. The amperes (actually miliamperes) is marked on the battery pack or on the individual cells, if you buy them. Nowadays, capacities over 1200 mA and above are common.

    Additional safety devices are used to stop you boat if something goes wrong. Look at the Technical segment, Fail Safe chapter. Don't use your boat without one. It's a cheap protection to protect a expensive investment and, mainly, to prevent an accident with personal injuries.

    Important Notes:
    • Always charge completely your batteries before putting the boat on water.
    • Check the range of your radio before putting your boat on the water: Turn on the transmitter and collapse it's antenna, turn on the receiver and start the engine - for gas boats - and move away 15 yards (30 for AM radios). Ask a friend to check the operation of the servos while you operate the transmitter with the antenna collapsed. Be sure the servos are not vibrating or making strange noises. Don't launch your boat if your radio is erratic. Erratic operation even with fully charged batteries demands professional attention.
    • Never cut or coil the antenna inside the boat. It should be inserted in the antenna support in a vertical position, to allow for better reception.
    • Keep the electronics tight into the radio box, do not allow them to bounce around.
    • Keep the radio box as water proof as possible. Keep the receiver and batteries in a plastic bag or balloon, closed with tape. Seal the radio box. Remember: water, especially salt water, is enemy of your electronics.


    Finally: you got here a guide, as complete as possible, on how to assemble your R/C boat. But it's impossible to cover all the aspects of this hobby, so we limited our recommendations to gas engine boats, using mono or cat hulls. There is no mention to outriggers. Maybe someday we will be able to assembly and drive one. On that occasion we will feel more comfortable to talk about them. Remember, the recommendations are those that USUALLY work better for the boat type in question. However, they are just a starting point. We suggest that you, from this starting point, make your own experiences. The Attitude page makes a deeper examination on the issue. The only thing you could loose is the fear of trying.

    Carlos Andrade