Repairing Aluminum Boats: Dents And Dings

Aluminium boats are prone to dents and dings, and there are several ways to repair them. Some boat owners opt to leave the dents as they are, especially if they are minor and the boat is used for drifting. Others prefer to repair them for aesthetic reasons or to prevent leaks. One way to repair dents is to use a hammer and dolly setup, with a hammer on one side of the metal and a dolly on the other. This method can be used for both large and small dents, but it is important to be gentle to avoid thinning the metal, which can compromise the structural strength of the boat. Another method is to use a paintless dent removal process, which involves using heat and cold to shrink and expand the dents. Fillers can also be used, but it is important to choose a marine-grade filler that is compatible with aluminium to avoid issues due to different expansion rates. For severe dents, it may be necessary to cut out the damaged area and weld in a new piece of metal.

Using heat to repair dents

First, it is crucial to determine the type of aluminium your boat is made of. The most common type used in boat hulls is 5000 series aluminium, which is not heat-treated. However, if your boat is an older model or has been welded, it may be made of 6000 or 7000 series heat-treated aluminium. To identify the type of aluminium, look for markings or, if necessary, cut out a small piece and test it.

If you have confirmed that your boat is made of 5000 series aluminium, you can attempt to repair dents with heat. The key is to heat the aluminium gently and not exceed a certain temperature. The ideal temperature for 5000 series aluminium is around 325 degrees Fahrenheit, and you should avoid going above 450 degrees Fahrenheit to prevent irreparable damage. To monitor the temperature, you can use temperature sticks from a welding supply store, which melt at specific temperatures.

When heating the aluminium, use an Oxy-Acet torch and coat the area with black soot by cranking up the acetylene first. Then, apply a gentle, orange flame rather than a blue flame. You can test the temperature by dragging a hickory hammer handle across the aluminium. When the handle slides easily and a light tuft of smoke trails it, the aluminium is ready. Be careful, as a few more seconds of heat can ruin the metal.

Once the aluminium is heated, you can shape it with gentle force. Remember, "shape and caress" the material, don't beat on it. You can use a dolly and a rubber mallet to work out the dents slowly and carefully. If the dent is on the side of the boat, have one person hold a heavy, flat piece of metal on the outside while another person uses the mallet on the inside. Always work with the aluminium's flexibility rather than against it.

It is important to note that using heat on aluminium can be risky, and there is a chance of damaging your boat. If you are unsure or uncomfortable with this method, it is best to consult a professional or consider other repair options like paintless dent removal, fillers, or hydraulic rams. Additionally, always take necessary safety precautions when working with heat and flammable materials, and ensure that any flammable materials in your boat, such as carpeting or plastic, are removed before attempting this repair.

Using a hammer and dolly setup

To repair dents in an aluminium boat using a hammer and dolly setup, you will need to first ensure that the aluminium is not heat-treated, as this can cause the metal to crumble and fall apart. The ideal temperature for working with aluminium is when it is limber but before it turns blue and smoky. To test this, you can use a hickory hammer handle, which should drag and stick across cold, non-painted aluminium. As you apply heat, the handle will begin to slip easily across the metal. Once it does so with a light tuft of smoke trailing, the aluminium is ready.

If the dent is located below the floor of the boat, you will need to remove anything that is in the way. If the dent is on the side of the boat, you will need one person on the outside with a heavy, flat piece of metal, and another person on the inside with a rubber mallet to tap out the dents. Do not use a metal hammer on the hull. If more force is needed, you can use a piece of aluminium placed against the inside of the hull and then use a heavier metal hammer.

For deeper dents, you can use a porta-power or a makeshift pump jack. Ensure that the side you are not working on is fully supported, as you do not want to push out a dent on the wrong side.

When hammering out the dents, start at the edge and work towards the centre. Aluminium on boats can be thick and tough to move, so patience is key.

Filling dents with body filler

Step 1: Assess the Damage

Before beginning the repair, it is important to assess the size and depth of the dents. Smaller dents above the waterline may be easier to repair with body filler, while larger or deeper dents may require alternative methods such as dent removal or welding.

Step 2: Choose the Right Filler

When choosing a body filler, it is important to select a product specifically designed for use on aluminium boats. Some recommended fillers include marine putty, JB Weld putty, and Bondo Fiberglass Resin Jelly. These fillers are waterproof and suitable for below-the-waterline repairs.

Step 3: Prepare the Surface

Before applying the body filler, clean the dented area thoroughly. Use a wire wheel to remove any dirt, debris, or corrosion. This will ensure that the filler adheres properly to the aluminium surface.

Step 4: Apply the Filler

Start by applying a thin layer of the body filler to the dent using a putty knife or similar tool. For deeper dents, you may need to apply multiple layers, allowing each layer to cure before adding the next. Bring the final layer slightly above the surface of the aluminium to ensure the dent is completely filled.

Step 5: Sanding and Finishing

Once the filler has cured, use a coarse-grit sandpaper (such as 80-grit) to sand the filler down to a level that is flush with the surrounding aluminium surface. Then, progress to a finer grit sandpaper (such as 400-grit) to smooth out the repair. Finally, wet sand the area with a very fine grit (such as 1500-grit) to achieve a smooth finish that is ready for priming and painting.

Tips and Precautions:

• Always work in a well-ventilated area when using body fillers and wear appropriate protective gear, including gloves and a respirator.
• Be cautious when sanding aluminium, as excessive sanding can thin the hull material and compromise its structural integrity.
• Some body fillers may require the use of a primer or etch primer before painting to ensure proper adhesion. Always follow the manufacturer's instructions for the specific product you are using.

Fixing from the inside

Fixing dents in an aluminium boat from the inside is possible, but it depends on the location of the dent and the type of boat. If the dent is located below the floor of the boat, you can simply remove anything that is in the way and use a hammer and dolly setup to repair the dent. Be sure to replace anything you removed after finishing the repairs.

If the dent is located on the sides of the boat, the aluminium is likely too thick for paintless dent repair (PDR) methods to be effective. In this case, you would need to clear the area and use a hammer and dolly or a rubber mallet to work the dent out. Start at the edge of the dent and work your way towards the centre. Aluminium on boats can be tough to work with, and it may require significant force to remove the dent.

When using a hammer and dolly, one person should be on the outside of the boat with a heavy piece of flat metal, while the other person is on the inside with the hammer and dolly. The person on the inside should use a rubber mallet to gently tap the dent out, being careful not to use too much force and cause further damage. If more force is needed, a piece of aluminium can be placed against the inside of the hull, and a heavier metal hammer can be used.

For larger dents, you may need to use hydraulic rams or a porta-power to apply more force. These methods can be more complex, and it may be advisable to seek professional help.

It is important to note that using heat to repair dents in aluminium boats is a controversial topic. Some people suggest using an oxy-acetylene torch to gently heat the aluminium, being careful not to exceed the annealing temperature, which can cause irreparable damage to the metal. Others advise against using heat at all, as it can cause the aluminium to become brittle and crumble. If you choose to use heat, it is crucial to take the necessary precautions and monitor the temperature closely to avoid damaging your boat further.

Fixing from the outside

If the dent is accessible from the outside, you can try to repair it without having to go inside the boat. Here are some methods you can use:

• Hammer and dolly method: This method involves using a hammer and a flat piece of metal (called a dolly) to work the dent out. Place the dolly on the outside of the dent and gently tap it with a rubber mallet or a body shop hammer. It is important to use a rubber mallet or a soft-faced hammer to avoid damaging the aluminium. Start at the edge of the dent and work your way towards the centre. This method is most effective for shallow dents and may not work for deeper dents.
• Heat and cold method: This method involves using heat and cold to shrink and expand the metal, which can help to remove dents. It is important to be very careful when applying heat to aluminium, as it can easily become too hot and crumble. Use an oxy-acetylene torch to heat the area around the dent, being careful not to overheat the metal. You can test the temperature of the metal using temperature sticks, which change colour at specific temperatures. Once the metal is hot, use a hammer and dolly to work the dent out. To cool the metal and shrink it, you can use a cold pack or a can of compressed air.
• Paintless dent removal: This method uses specialised tools and techniques to remove dents without damaging the paint or the metal. It is often performed by professionals, but there are also DIY kits available. This method is most effective for shallow dents and may not work for deeper dents.
• Filler and sanding: This method involves using a filler to fill in the dent and then sanding it down to create a smooth surface. It is important to use a filler that is specifically designed for use with aluminium, such as a marine-grade filler or a product like Bondo. Be sure to follow the instructions on the product carefully. After filling and sanding the dent, you can paint over it to match the colour of your boat.

Remember to assess the size and depth of the dents and choose the most appropriate method for your situation. Always take the necessary safety precautions when working with tools and materials.

Frequently asked questions