What Is The Best Fiberglass For Boat Hull Repair?

Owning a boat comes with the burden of repairing it whenever required. While it’s recommended to maintain a routine to keep you boat in good condition, sometimes there is a need to repair the hull or a specific region if something goes wrong. If you need to repair the boat hull and are analyzing the best fiberglass for it, it gets daunting. If you’re a beginner, you need to keep reading.

The ideal fiberglass for boat hull repair is E-glass fiberglass, but you can also use S-glass, carbon fiberglass, blended fiberglass, and Kevlar fiberglass. The choice of fiberglass depends on your budget, boat type, nature of damage, and skill levels of resources. 

Some boaters also choose epoxy resin to repair boat hulls. Deciding on the best fiberglass is tricky. To get this right, here’s a detailed guide of different options of fiberglass available for you and the exact method to repair your boat with fiberglass. 

Let’s begin!

Types of Fiberglass For Boat Hull Repair

When you spot a hole or a dent in the boat hull, it’s possible to take advantage of glass fabric and fix the same. However, it also depends on the skill of the resource to tackle the issue. 

Most beginner boaters assume that the procedure to repair a boat hull is simple and straight forward. I will say my first time doing fiberglass was a bit difficult.

Let’s look at possible types of fiberglass to repair your boat hull. 

E-Glass Fiberglass

Think of boat repairs; this type of fiberglass tops the list. It’s mainly due to its high durability and promising tensile strength. It’s considerably affordable. You can use e-glass fiberglass for a wide range of applications, and it’s very versatile. 

S-Glass Fiberglass

Also called structural glass, it is comparatively stronger and more durable. This type of fiberglass is ideal if you own a racing or high-performance boat where tensile strength is of utmost significance. 

Carbon Fiberglass

In the case of minor repairs, you don’t need fiberglass with high tensile strength to fix it. You can invest in a lightweight material that fixes the issue but is also extremely stiff to avoid the likelihood of the same problem in the future. 

Most experts or boat hull repair technicians use carbon fiberglass in association with other types to take advantage of their individual properties. 

Kevlar Fiberglass

Are you looking for the strongest fiberglass that ranks the best in multiple aspects? Kevlar fiberglass is your answer. Not restricted to reliability and strength, this type of fiberglass is resistant to chemicals and UV rays. It’s the most expensive of the lot but performs the best. 

Blindly use it for your boat hull, and don’t worry about puncture or any high-impact actions on the hull!

Blended Fiberglass

Certain scenarios don’t need high-end material to fix the issue. However, you may want to take advantage of the property associated with it. In such cases, you can choose blended fiberglass fabrics where you blend S-glass and E-glass or any other type and balance cost, durability, reliability, and stiffness. 

Note: The only downside is that the technician needs to know how to deal with composite fabrics. Otherwise, it loses its purpose. 

How To Repair Your Boat With Fiberglass?

The fiberglass on your boat can get damaged due to a wide range of reasons. When it’s small enough, you can easily get hold of a fiberglass repair kit and follow the instructions to fix the same. However, when the repair size is large, the process is long and needs expertise as well. 

If you’re looking for a step-by-step guide to repairing your boat with fiberglass, here you go:

Step 1: Inspect damage

The first step is to determine the damage and cut it away. You need a plastic screwdriver to tap on the impacted area and determine the degree of damage. Repeat this process until you find all the impacted areas on the boat. 

Once you inspect the damage, it’s time to cut the impacted area in a circular/oval form. 

Okay, we hear your question on how to cut the area! You need an orbital saw to start the process and a sanding disk embedded in a driller to properly cut it out. 

Tip: The key is to clear the area of any delaminated fiberglass. If you miss even a small part, it can cause a weak point that grows over time.

Once you delaminate, tap on the area with the screwdriver handle. You can hear a dull, shallow noise. 

There is a professional service where an expert will sonogram your boat for weak points in the fiberglass. You need to search the area you live in to see if this is available, but it is a sure way to find weak points in your boats hull. Sailing UMA on youtube had an episode about this. 

Step 2: Preparing a new glass 

Depending on the level of damage, you should decide on the working methodology. For instance, damage that’s over the water line and small, is a much easier approach then something below the waterline that’s a foot long.

In this step, you’d begin scarfing where you sanded a normal scarf angle of 12:1 (12 units of sanding for 1 unit of repair thickness) in the old fiberglass and then prepare the new fiberglass. 

As soon as you sand it down, remember to clean the area and apply acetone to avoid residues or debris settling on it. 

Step 3: Dewax, mask, and fix 

As a rule of thumb, always use a dewaxing solvent to clean the damaged area and its surrounding before you continue working. This will help strengthen the bond. 

When you mask the layer, follow the steps below:

  • Mimic the original cloth type and thickness to achieve the original tensile strength. 
  • Wet the cloth and then apply it to the location. 
  • You need a peel-ply cloth to eliminate air bubbles and a vacuum bag to strengthen the laminate-laminate bond. 

Working on the fiberglass fabric ideally means stacking 2 layers of a 1.5-ounce mat followed by a conventional mat and a 6-ounce cloth. 

Tip: The first layer of the mat should essentially cover the completely affected area. Measure and cut accordingly. 

Epoxy fabric is widely used to fix any repair over/under the waterline. Vinylester or polyester resins are also available. However, the latter would need a layer of laminating resin. 

Note: Don’t use epoxy for a repair surface that’s made of a gel coat. 

Step 4: Finish & paint

As soon as you lay the mat and also use a resin roller to free bubbles from the surface, you should allow the surface to dry thoroughly for 24 hours. After sanding, priming, and painting, your fiberglass boat is ready to use. 

More Tips!

-Remember you can use too much fiberglass. Dont overdue it. 

-It can get messy, make sure to have gloves and extra rags available.

-Start with a small damaged area and practice, before tackling a huge hole in the hull.

If you need a schedule of things to check on your boat, click the image below!

Final Thoughts

Repairing the fiberglass of a boat’s hull is challenging when you lack the expertise or access to necessary resources. For any repair, you should always have a screwdriver, cordless drill, orbital saw, vacuum pump, sandpaper, grinding disks/pads, fiberglass cloth, peel ply, drill disk, epoxy, and a hose handy. This will relieve you from stress and also enable you to fix the repair on the go. 

Always do extra research and practice on a small area before tackling a big project. Trust me!

Happy repairing!


Boatlifehq owner and author/editor of this article.

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