Repairing Your Rc Boat Hull: A Comprehensive Guide

Owning a remote-controlled boat is fun, but it's normal for them to get damaged if you use them. If you want to avoid buying a new boat, you'll need to know how to repair it. The first thing to consider is the type of boat you have, as there are a variety of boat types from aluminium to fibreglass to polyester or plastic. Before starting your boat repair, make sure you know what your boat hull is made of. For example, if you have a fibreglass boat, you can repair it using epoxy resin. If the damage is above the waterline, it's best to make the repair from inside the hull. You'll also need to bevel the edge of the hole and make sure you remove any wax from the area before grinding. For a plastic boat, simply use plastic modelling glue to stick the parts together.

Repairing fibreglass hulls

Before starting any repairs on your RC boat, it's important to know what type of boat you have and what the hull is made of. If you have a fibreglass boat, you can repair it using epoxy resin.

First, assess the damage. Tap the impact area with a plastic screwdriver handle to determine the extent of the damage. A solid laminate will sound sharp, while delamination will sound dull. Check inside the boat and make a circular or oval cut to remove the damaged area. Always cut out and replace damaged fibreglass with new laminate.

If the damage is above the waterline and the area is small, make the repair from inside the hull. You'll need to bevel the edge of the hole with a 12-to-1 chamfer. This will minimise the surface area that needs to be refinished after the repair.

Before grinding, wash the area around the hole with a dewaxing solvent to remove any traces of mould release or wax surfactant. Use a disk sander with a 36-grit disk to grind a 12-to-1 bevel around the hole's perimeter. Protect yourself with goggles, a dust mask, and long sleeves.

To prevent resin runs, coat the exterior surface around the hole with paste wax, being careful not to get any on the edge or inside. Mask the area below the hole.

For the repair, you'll need fibreglass fabric, gelcoat, and resin. Cut the fibreglass fabric to fit the hole, starting with two layers of 1.5-ounce mat, then alternating with 6-ounce cloth. The number of layers will depend on the thickness of the hull. Cut the first layer to the full size of the ground depression, and subsequent layers about an inch smaller.

If the repair is above the waterline, you can use polyester or vinylester resin. For underwater repairs, use epoxy resin. Mix the resin with the hardener, following the manufacturer's instructions. Apply the gelcoat to the backer, then wet it with resin and lay up the first few layers of mat and cloth, working out any bubbles. Continue laying up additional plies until the repair is flush with the interior surface.

Finish by applying a final layer of mat and cloth over the patch, then seal it to allow curing. Remove the backer, fill any imperfections in the gelcoat, and sand and polish the repair area.

For repairing deep scratches or gouges, you'll need powdered fibreglass filler, gelcoat, and a gelcoat reducer. Remove any old paint or decals, then cut a U-shaped groove into the gouge to eliminate sharp edges. Sand out the scratches, then mix the gelcoat with the hardener and filler to create a putty. Apply the putty to the gouge, then sand it down. Mix a fresh batch of gelcoat and spray the patched areas. Allow it to cure, then sand and buff the repairs for a smooth finish.

Repairing plastic and polyester hulls

Plastic hulls are the easiest to repair. For small repairs, use plastic modelling glue to stick the boat parts that have come apart. For larger holes, use a two-part modelling putty to plug the hole, then sand, paint and varnish.

For repairing polyester hulls, you will need a polyester repair kit for small repairs or a polyester laminating kit for larger repairs. You will also need safety equipment, such as gloves, a vapour mask and safety goggles.

First, clean the surface well and inspect the damage. Then, grind/sand bevelled edges into the hole or crack to allow for proper adhesion. Sand around the hole for good adhesion for the overlapping fibreglass mats.

Next, support the surface. You can do this by stretching a piece of string across a piece of cardboard. Put a little polyester putty with hardener on the edges of the cardboard.

Now you can start rebuilding the fibreglass laminate. Mix the polyester resin with about 2% hardener and apply a little polyester resin around the repair and on the piece of cardboard. Tear the fibreglass mats into small pieces and place a mat on the hole, wetting it thoroughly with polyester resin. Then, put a slightly larger piece of fibreglass mat over it and wet it again. Repeat this until you have reached the original thickness and have overlap with the substrate around the crack or hole.

Finally, let it harden for at least 24 hours and remove the string. After this, it can be sanded with a coarse grit and finished further with a topcoat, filler and varnish.

Repairing aluminium hulls

Aluminium hulls are resilient, but they can become damaged and will need repairing. The type of repair depends on the type of damage the boat has sustained. If the rivets are leaking, you can purchase a special rivet repair kit. Some people have reported success using epoxy resin and liquid weld, but these repairs only hold for a short time.

If the hull is dented, you will need to get it back into shape before fixing further damage. Have an assistant hold a hand anvil against the outside of the dented area, while you hammer lightly at the dent from the inside, tapping and straightening the bent aluminium until it is close to its original shape.

If there is a hole or crack, you will need to use epoxy to fix some scrap metal to the outside of the puncture. This will create a stable place for the brazen rod material to settle. If the hull is cracked, use a drill and cone bit to cut the crack into a V-shaped channel, with the small end of the V being the crack itself. If there is a simple hole, grind away just enough so that the brazen rod material has something to bind to. Sand it down with 220-grit sandpaper.

Heat the area around the puncture with a propane torch, then scrape it with a wire brush to roughen the surface, which will help the brazen rod material bind to it. Hold the heat steadily on the puncture while applying the tip of the brazing rod over the sides of the puncture, allowing it to melt and flow into the gap. Ensure the melted material overlaps itself and fills the gap entirely. As it cools, use the wire brush to scrape away the slag and residue.

Once it has cooled entirely, use a flat file to remove any excess brazen rod material that extends past the aluminium panel, getting it even without digging into the brazen weld. Remove the scrap aluminium from the outside of the hull, and you're done!

Waterproofing the boat

Waterproofing your RC boat hull is essential to ensure that your boat stays dry during races and outings on the water. Here are some detailed instructions to help you achieve a fully waterproof hull.

Fixing Electronics:

First, ensure that all electronic components are securely installed and protected. Check that the ESC, switch, and receivers are firmly adhered to the inside of the hull. Use a strong tape like Parma's Pro Servo Tape to hold them in place. This will prevent them from detaching during shipping or operation.

Protecting the Drive System:

The drive system, which includes the drive shaft and tube, needs to be properly lubricated to reduce friction. Remove the drive shaft or flex shaft and apply marine grease to it. Pro Boat and AquaCraft offer suitable marine grease products. This grease will also help with waterproofing by creating a seal between the drive shaft and its tube.

Radio System Setup:

The radio system's setup is crucial for optimal performance. Ensure you use an antenna tube to keep your antenna as high as possible, improving signal reception. If your system uses two antennas, such as Futaba's FAAST or Spektrum's marine receivers, position the secondary antenna vertically to the primary one, mounting it above the waterline inside the hull.

Applying Polyester Resin:

Polyester resin is a vital component in waterproofing your RC boat hull. Mix the resin with two drops of catalyst in a can and then pour it into the boat. Ensure that all hull surfaces and joints are covered. This step will effectively seal your hull, preventing water from entering and ensuring your boat remains buoyant during races.

Additional Tips:

• Always use fresh batteries in your transmitter to avoid signal loss due to dead batteries.
• Seal the joints between the canopy and hull with tape to create a super-sealed barrier against water ingress.
• When waterproofing, pay close attention to the hull bottom and sides, ensuring they are adequately settled and treated with polyester resin.
• Close the hull setting correctly and permanently seal any holes to make the hull watertight.

Sanding and refinishing

Preparation:

Before you begin sanding, it's important to identify the type of boat hull you have, as the process may vary for different materials. Common hull types include fibreglass, aluminium, plastic, and polyester. Knowing the material will help you choose the appropriate tools and techniques for sanding and refinishing.

Tools and Materials:

For sanding, you'll need sandpaper or sanding blocks with varying grit sizes, such as 80 to 100 grit for initial sanding and finer grit sizes like 240 or higher for a smoother finish. You may also need a razor plane or a sanding stick for harder-to-reach areas. Additionally, wear protective gear like goggles and a dust mask to safeguard your eyes and lungs from dust and debris.

Sanding Process:

• Mark the edges: Use a magic marker to outline the edges of the deck and keel, providing a visual guide during sanding and helping to prevent over-sanding in specific spots.
• Sand the hull: Using your chosen sanding tool, start sanding the hull along the length, following the contour of the hull. Focus on areas with inconsistencies or bumps. Pay close attention to the shape and fairness of the deck, keel, and chine shelf.
• Transition areas: Pay close attention to the transition between bulkheads, deck, and chine shelf (or stringers). Use a straight sanding block or stick to ensure a smooth finish in these areas.
• Sanding technique: When sanding, work in the direction of the length of the hull. Avoid using coarse sandpaper, as it can tear the surface. Instead, opt for medium-course sandpaper.
• Final shaping: Once you're satisfied with the sanding, give the hull its final shaping. This includes ensuring that the keel is sanded to an edge, providing a flat area for the planking to adhere to.

Refinishing:

• Clean the surface: After sanding, thoroughly clean the surface of the hull to remove any dust, debris, or residue. Use a solvent or acetone-dampened rag to wipe down the area.
• Filling and patching: If there are any gouges, deep scratches, or holes, fill them using an appropriate filler or epoxy resin. For larger holes, you may need to use fibreglass mesh or modelling putty before applying epoxy resin.
• Drying and curing: Allow the filler or epoxy to dry and cure completely. Follow the manufacturer's instructions for curing times and techniques.
• Sanding the filler: Once the filler or epoxy has cured, sand it down to ensure a smooth and level surface. Use finer grit sandpaper for this step to blend the repaired area with the surrounding hull.
• Painting or varnishing: After sanding, you can repaint or revarnish the repaired area to match the colour and finish of the rest of the hull. Choose a paint or varnish that is suitable for the material of your boat hull.
• Final buffing: Optionally, you can use a professional buffer with a wool buffing pad and buffing compound to give the repaired area a high-quality shine. This step will enhance the overall appearance of your RC boat.

Remember to take your time during the sanding and refinishing process, as it is crucial for achieving a durable and aesthetically pleasing repair. Always follow safety precautions and work in a well-ventilated area when using chemicals or power tools.

Frequently asked questions