Attaching Plywood To Aluminum Boats: The Ultimate Guide

Boat owners may need to attach plywood to their aluminium boats for a variety of reasons, such as redecking or raising the height of a boat seat. There are several methods for attaching plywood to aluminium boats, including using rivets, glue, or screws. Before beginning any work, it is important to wear the proper safety equipment, including safety glasses, hearing protection, and leather gloves.

Use marine-grade plywood

Marine-grade plywood is a great option for your aluminium boat. It is a durable and cost-effective choice for boat flooring. This type of plywood is made from high-quality plies of wood, such as Douglas fir, that are bonded together with waterproof glue. The outer ply is typically an A-grade, smooth and paintable, while the inner plies are B-grade or better, ensuring a strong and stable surface.

When selecting plywood for your boat, it is important to consider the grade and treatment of the wood. While pressure-treated plywood is commonly used for protection against rot and decay, it may not be the best option for boat repair or building. The pressure-treating process leaves the wood with high moisture content, which can affect the bonding process and the strength of the wood. Exterior-grade plywood is another option but is generally thinner and has fewer plies, which can impact its overall strength and stiffness.

Marine-grade plywood, on the other hand, offers superior resistance to warping and cupping. It has more plies, which contribute to its overall strength and stiffness. This makes it a great choice for boat flooring, especially if you plan to use vinyl flooring or carpeting on top. It is also a good option if you want to seal the wood with epoxy or polyurethane to protect it from water damage.

When purchasing marine-grade plywood, be sure to check for any imperfections or voids in the wood. While it is more expensive than other options, it is worth the investment if you plan to keep your boat for a long time. You can often find this type of plywood at home improvement stores or lumber yards.

Additionally, when installing the plywood, it is important to consider the fasteners you will use. Rivets, bolts, and nutserts are commonly used to attach plywood to aluminium boats. You can also use epoxy or glue to secure the plywood in place, but this may not be as easily removable as mechanical fasteners.

Seal plywood with oil-based paint

Sealing plywood is essential for protecting it from water damage, wear and tear, and UV rays, while also bringing out the natural beauty of the timber. This is especially important for plywood used in boats, as moisture can cause the layered structure of the plywood to separate, even if it is pressure-treated.

Step 1: Sand the Plywood

Use sandpaper with an 80-grit measurement to sand all sides of the plywood. Sand in a back-and-forth motion, following the natural grain of the wood. Repeat the process with 120-grit sandpaper for a smoother finish.

Step 2: Clean the Plywood

Use a clean cloth to wipe away any plywood dust. Ensure that the surface is dust-free and clean before applying any sealants or paints.

Step 3: Apply a Sanding Sealer (Optional)

Use a clean paintbrush to apply a sanding sealer to the plywood. Apply the sealer with even and level brush strokes to ensure a smooth and uniform coating. Allow the sealer to dry according to the manufacturer's instructions. If sealing both sides, finish one side at a time.

Step 4: Lightly Sand the Sealed Surface (Optional)

Use 120-grit sandpaper to lightly sand the sealed surface, removing any bumps and airspaces left from the first sealing. Sand until you achieve a smooth finish without damaging the sealing.

Step 5: Apply the Oil-Based Paint

Stir the oil-based paint thoroughly and pour it into a paint tray. Using a paintbrush, roller, or spray, apply the paint to the plywood. Ensure that you wear protective gear, including gloves, a mask, and glasses, throughout the process.

Follow the manufacturer's instructions for drying times and apply additional coats as needed. Oil-based paints typically require longer drying times and may need sanding and touch-ups between coats for optimal results.

Additional Tips:

• Always work in a well-ventilated area when using oil-based paints.
• Protect surrounding surfaces with plastic masking film or drop cloths before starting the project.
• Clean the plywood thoroughly before sealing to ensure that the surface is free of dirt, dust, and other contaminants that could affect the finish.
• Consider using a sealing product, primer, or waterproofing undercoat before applying the oil-based paint for added protection.

By following these steps, you can effectively seal plywood with oil-based paint, ensuring its longevity and enhancing its appearance.

Use pop rivets to attach plywood

Using pop rivets to attach plywood to an aluminium boat is a straightforward process. Pop rivets are ideal for this task as they provide a strong, durable hold that can withstand the twisting and pounding that a boat takes when navigating waves.

To begin, you will need to purchase the appropriate pop rivets for your project. It is recommended to use aluminium pop rivets to avoid corrosion. Make sure to select the correct size and grip range for your specific application. You can find pop rivets at hardware stores or specialised suppliers.

Next, determine the placement of the rivets. Decide whether you will be using a template to mark the rivet locations or drilling new holes. If you plan to use a template, create one that aligns with the existing rib structure of the boat. This will ensure that the rivets are centred correctly.

Once you have determined the rivet placement, drill the holes in the plywood. Apply a sealant, such as epoxy or marine adhesive, to both sides of the plywood and around the drilled holes to protect against water intrusion.

Now, you are ready to install the pop rivets. Using a rivet gun, insert the rivets through the drilled holes and secure them in place according to the manufacturer's instructions. Ensure that the rivets are installed tightly and securely.

By following these steps, you can effectively use pop rivets to attach plywood to your aluminium boat, creating a strong and durable bond that will withstand the elements.

Avoid treated lumber

When building platforms or flooring for an aluminium boat, it is important to avoid using treated lumber. Treated lumber is wood that has been treated with chemicals to make it more durable and resistant to rot. While this may seem like a good idea for a boat, which is often exposed to water, the chemicals used in the treatment process can actually be harmful to the aluminium structure of the boat.

The most common type of treated lumber contains copper, which can corrode softer metals like aluminium when the two come into contact. This corrosion may not be immediately visible, but over time, it can cause pitting, indentations, and eventually, holes in the aluminium. This is because water causes the chemicals in the treated wood to leak out, allowing the copper to eat away at the aluminium.

To avoid this issue, it is recommended to use untreated wood that has been sealed with a waterproof coating, such as polyurethane, resin, epoxy, or exterior paint. This will protect the wood from water damage without risking corrosion of the aluminium. Another option is to use a non-wood material altogether, such as aluminium sheets or composite decking, which will not rot like wood and can be lighter in weight.

If treated lumber is already present in the boat, it is possible to create a barrier between the wood and the aluminium to prevent direct contact. However, this may require additional work and expense, and even then, the copper chemicals may still find a way to leak out and cause corrosion. Therefore, it is best to avoid using treated lumber in aluminium boats altogether if possible.

Use solid rivets to connect aluminium and plywood

Solid rivets are one of the oldest and most reliable types of fasteners, having been used by ancient civilisations like the Egyptians, Vikings, and Romans. They are also commonly used in modern times for construction, manufacturing, aerospace, automotive, and boat building.

Solid rivets are a good option for connecting aluminium and plywood because they are permanent, easy to install, and can be removed without damaging the parent material. They are also ideal for applications where reliability and safety are important.

To use solid rivets to connect aluminium and plywood, follow these steps:

• Drill matching holes in the aluminium and plywood: The holes should be pre-drilled and matching in size to ensure a tight fit for the rivet.
• Insert the solid rivet: Place the rivet through the holes in the aluminium and plywood. The rivet will have a smooth cylindrical shaft with a head on one end, and the end opposite the head is called the buck-tail.
• Deform the tail: Using a hammer or a rivet gun, deform or flatten the tail of the rivet. This will cause the tail to expand to about 1.5 times its original diameter, holding the rivet in place and creating a strong joint between the aluminium and plywood.
• Inspect the joint: Solid rivets allow for easy inspection to ensure that the installation has been done correctly.

It is important to note that solid rivets require access to both sides of the workpiece, unlike blind rivets which can be installed from one side. Additionally, the setting pressure for solid rivets can be high, so choosing the right size and power of the rivet gun is crucial.

Frequently asked questions