Replacing A Fibreglass Boat Floor: A Step-By-Step Guide

Replacing a fibreglass boat floor is a complex task that requires a lot of time and effort. It involves removing the old flooring, repairing any damaged areas, and installing new flooring. This process can be challenging, especially if you're working with a wider boat or dealing with significant damage. Online forums and video tutorials can provide valuable guidance, but it's essential to plan ahead, gather the necessary tools, and be mindful of safety precautions when undertaking this project.

Remove old flooring

Removing the old flooring from a fibreglass boat is a crucial step in the restoration process. Here is a detailed guide on how to do it:

First, clear out everything loose in the boat, including any debris and old, damaged materials like plywood or carpeting. It is important to also remove the centre console and any cables to ensure they don't get in the way during the renovation process. Make sure to keep a record of everything you disconnect or remove, so you can put it all back together correctly later on.

Next, assess the extent of the damage and identify the areas that need to be cut out and replaced. Depending on the severity of the damage, you may need a power cutter or heat gun to remove the old flooring, or you may be able to simply cut it out with a skill saw. If there is extensive rot, you may also need to inspect and repair the stringers and other surrounding areas.

When cutting out the damaged sections, it is recommended to cut at a 45-degree angle, rather than a 90-degree angle, to create a lip for the new flooring to sit on, making the repair more solid and easier. Once all the rotten wood has been removed, fill any holes in the plywood with wood filler and sand it down to smooth the surface.

Finally, before installing the new flooring, it is important to sand and caulk any gaps or seams between the new floor and the hull, posts, and stringers. Clear caulk is recommended to avoid it standing out against the fibreglass.

Prepare tools and materials

To replace a fibreglass boat floor, you will need to prepare the necessary tools and materials. This process will involve removing the old flooring, making repairs, and installing new flooring. Here is a detailed list of the tools and materials you will need:

Tools:

• Power cutter or heat gun: For removing severely damaged floors.
• Sandpaper: To smooth and prepare the surface for caulking.
• Caulking gun: To seal gaps and seams between the new floor and the hull, posts, and stringers. Choose clear caulk to avoid it standing out against the fibreglass.
• Paint rollers: For applying resin and gel coat. Use different-sized rollers for better reach and coverage.
• Safety equipment: Gloves, coveralls, eye protection, and a respirator are essential when working with chemicals and power tools.

Materials:

• Unwaxed marine polyester resin: Acts as a primer coat and should be mixed with a hardener in the correct proportions.
• Gel coat or boat deck paint: For the final coating over the fibreglass. Gel coat is tougher and more protective, while paint offers more colour options and can be non-skid.
• Polyurethane sealants: Such as clear caulk, for sealing gaps and seams.
• Wood filler: To fill any holes in the plywood before sanding.
• Fibreglass matting or chopped strand mat (CSM): Provides reinforcement and strength to the new flooring.
• Epoxy: For adhering the new flooring and sealing any fresh cuts or screw holes in the plywood.

Before beginning the project, ensure you have cleared out all loose items, debris, and damaged materials from the boat. Take measurements for the new flooring and make a note of any cables or connections that need to be accommodated. It is also recommended to disconnect and set aside the centre console and any cables to prevent accidental damage.

Sand and caulk the floor

Sanding and caulking the floor of your fibreglass boat is a crucial step in ensuring a watertight seal. Here's a detailed guide on how to do it:

Before you begin, make sure you have all the necessary tools and materials, including sandpaper or a sander, a caulking gun, and a tube of caulk. It is also recommended to wear protective gear, such as gloves and eye protection, when handling power tools and chemicals.

Start by inspecting the floor for any imperfections or damage. Look for areas that need to be filled or smoothed out. If there are any holes, cracks, or uneven surfaces, use the sandpaper or sander to smooth them out. Sand the entire surface of the floor, including the edges, to create a uniform texture that will help the caulk adhere better. It is important to sand with the grain of the wood or fibreglass, not against it, to achieve the best results. Use a vacuum or a damp cloth to remove any dust created during the sanding process.

Once the floor is smooth and clean, it's time to apply the caulk. Cut the tip of the caulk tube at a 45-degree angle, creating an opening that matches the width of the gap you need to fill. Insert the tube into the caulking gun and slowly apply a thin , even layer of caulk along the seams and edges of the floor. Use a smooth, continuous motion to ensure a consistent bead of caulk.

After applying the caulk, use a damp finger or a small piece of wood to smooth out the bead, pushing it gently into any gaps or crevices. This process, known as "tooling," helps create a neat finish and ensures the caulk fills all the necessary areas. Allow the caulk to dry completely according to the manufacturer's instructions.

If needed, you can also paint over the caulk once it's dry to match the colour of your boat's interior. Just be sure to choose a paintable caulking product and follow the drying instructions before applying paint.

Remember, taking your time and working carefully will help ensure a proper seal and a long-lasting floor for your fibreglass boat.

Apply resin

Once you have mixed your resin, you are ready to start applying it to your fibreglass mat. Cover any area of the floor that you don't want to be fibreglassed with a clean cloth. Then, using a suitably-sized roller, apply the resin to the Chopped Strand Mat (CSM). Make sure you provide adequate coverage by rolling and painting the resin on the bottom, top, and sides of the CSM.

The amount of resin you use is up to you, but it is recommended to use either 3 oz. of resin per square foot of 1.5 oz. CSM or 4 oz. of resin per square foot of 2 oz. of CSM. You can also use multiple layers of CSM to add thickness and strength. If you do this, you can use the following formula to calculate how much resin to use:

> Opting for multiple layers of glass on the tops and sides prevents common issues like cracking and flexing over time.

After applying the resin, leave it overnight. Then, apply two layers of gel coat. The first layer of gel coat can be applied with a roller, but the second layer will need to be applied with a brush to ensure a smooth finish.

Lay out the chopped strand mat

To lay out the chopped strand mat, follow these steps:

First, ensure that the surface of your boat where you will be applying the chopped strand mat is clean, dry, and free from any contaminants that may hinder adhesion. This is an important step to ensure that the mat will properly adhere to the surface.

Next, cut and position the chopped strand mat. Cut the mat into the desired shape and size, making sure it fits the prepared surface of your boat perfectly. Position the mat onto the surface, ensuring a proper fit. The chopped strand mat should conform easily to complex shapes and contours, making it suitable for a variety of applications.

Once the mat is in position, apply the resin system evenly over it. Use a roller or brush to remove any trapped air bubbles and ensure proper consolidation. The resin will secure the mat to the surface and provide a watertight seal. Make sure to use the correct type of resin for the specific chopped strand mat you are using. Different types of resins may require specific binder materials. For example, chopped strand mats that use a styrene binder need to be used with polyester or vinyl ester resin.

After applying the resin, allow the composite to cure according to the resin system's specifications. This typically involves providing adequate time for the resin to harden and fully bond with the chopped strand mat. Refer to the manufacturer's instructions for the specific cure time.

Finally, reattach any removed components, such as seats or consoles, and clean out the area. You may also want to start the engine in a secure location to ensure that all connections are working properly.

By following these steps, you will be able to effectively lay out and apply the chopped strand mat when replacing the fibreglass boat floor.

Frequently asked questions