What Grit Sandpaper for Fiberglass Boat | Sanding Advice 2023

Last Updated on August 16, 2023 by Jisan

The best type of grit sandpaper to use on a fiberglass boat is 60-grit. This will remove any existing paint or varnish and provide a smooth surface for the new finish.

If you’re like most people, you probably think that any old grit sandpaper will do the trick when it comes to sanding down your fiberglass boat. But the truth is, there’s a big difference between different types of sandpaper – and using the wrong kind can actually damage your boat. So what’s the best grit sandpaper for fiberglass boats?

The answer might surprise you: it’s actually a very fine grit, like 2000 or 3000. That’s because fiberglass is a very soft material, so using a coarse grit will just end up scratching and damaging it. A fine grit will remove any surface imperfections without causing any damage.

So next time you’re getting ready to work on your boat, make sure you grab some fine grit sandpaper. Your boat will thank you for it!

How to Smooth Out Rough Fiberglass

If your boat’s hull is made of fiberglass, you may eventually notice some rough spots. Not to worry, though! There are a few easy steps you can take to smooth out your hull and make it look good as new.

First, sand the area with coarse-grit sandpaper until the roughness is gone. You may need to use a power sander for this step. Next, apply a thin layer of epoxy resin to the area and allow it to cure overnight.

The epoxy will help fill in any imperfections in the fiberglass and create a smooth surface. Finally, sand the area again with fine-grit sandpaper until it is completely smooth. You may need to repeat this step several times until you’re happy with the results.

What Type of Sandpaper for Fiberglass

If you’re working with fiberglass, you need to use the right type of sandpaper. Otherwise, you risk damaging the material. So, what kind of sandpaper should you use on fiberglass?

There are two types of sandpaper that are safe to use on fiberglass: silicon carbide and aluminum oxide. Silicon carbide is a synthetic abrasive that’s very sharp. It’s often used on hard materials like metal.

Aluminum oxide is a natural abrasive made from minerals. It’s not as sharp as silicon carbide, but it’s still effective for sanding fiberglass. Both types of sandpaper will work well on fiberglass.

However, if you’re doing a lot of sanding, you may want to use silicon carbide paper because it will last longer than aluminum oxide paper.

Gel Coat Paint for Fiberglass Boat

Gel coat is a type of paint that is specifically designed for fiberglass boats. It is a tough, durable and weather resistant coating that will protect your boat from the elements and keep it looking great for years to come. Gel coat is available in a wide variety of colors and can be applied with a brush, roller or spray gun.

What Paint to Use on Fiberglass Boat

If you’re thinking about painting your fiberglass boat, there are a few things you need to know first. Fiberglass is a tough material, but it’s not impervious to damage. The right type of paint and primer will help protect your boat from the elements and keep it looking its best.

There are two types of paint that can be used on fiberglass boats: one-part and two-part. One-part paint is easier to apply and typically doesn’t require as much prep work, but it doesn’t last as long as two-part paint. Two-part paint is more durable and provides better protection against UV rays and other environmental factors, but it can be more difficult to apply.

The type of primer you use will also depend on the type of paint you choose. One-part paints typically don’t require a primer, but two-part paints usually do. If you’re using a two-part paint, make sure to select a primer that’s compatible with the paint system you’re using.

Once you’ve selected the right type of paint and primer, it’s time to start prepping your boat for painting. The first step is to sand down the surface of the hull so that the new paint will have something to adhere to. Next, clean the hull with soap and water (or a pressure washer) to remove any dirt or grime.

Once the hull is clean and dry, apply tape around any areas that you don’t want painted (like rub rails or trim). Now you’re ready to start painting!

How to Sand Fiberglass for Paint

If you’re painting a boat or other item made of fiberglass, you’ll need to sand it first to create a smooth surface for the paint to adhere to. Here’s how to sand fiberglass for paint: 1. Start with coarse-grit sandpaper and work your way up to finer grits as you progressively smooth out the surface.

2. Use a power sander if possible to speed up the process. 3. Be sure to remove all dust from sanding before proceeding with painting.

What Grit Sandpaper for Fiberglass Boat
What Grit Sandpaper for Fiberglass Boat | Sanding Advice 2023 2

Credit: www.practical-sailor.com

What Grit Sandpaper Should I Use on Gelcoat?

There are a few different types of sandpaper that can be used on gelcoat, but the most common is grit sandpaper. The grit size will depend on the type of gelcoat you have and the condition of the surface. If you are working with a new gelcoat, you will want to use a finer grit sandpaper to avoid damaging the surface.

If the gelcoat is in good condition, you can use a coarser grit sandpaper to remove any blemishes or scratches.

What Grit Sandpaper to Use on a Boat?

If you’re working on a boat, you need to choose the right grit sandpaper. A lower number means a coarser paper while a higher number indicates a finer paper. For most boats, you’ll want to start with 60-grit sandpaper and work your way up to 220-grit.

60-grit sandpaper is great for removing old paint or varnish. It’s also good for roughing up surfaces before applying new paint or varnish. If you’re starting with a bare wood surface, though, you may want to begin with 100-grit sandpaper so you don’t damage the wood grain.

Once you’ve removed the old finish and prepped the surface, it’s time to move on to finer grits of sandpaper. 120-grit is a good choice for general purpose sanding, while 150- and 180-grit can be used for more delicate work. And if you really want a smooth finish, go all the way up to 220-grit.

Just remember that the finer the grit, the more time it will take to remove paint or varnish.

Do You Sand Fiberglass before Painting?

If you’re painting fiberglass, you don’t need to sand it beforehand. However, if the surface is damaged or has been previously painted, you’ll need to sand it down before applying new paint. For best results, use a fine-grit sandpaper and sand in the direction of the grain.

Do I Need to Sand between Layers of Fiberglass?

No, you do not need to sand between layers of fiberglass. Each layer of fiberglass will adhere to the previous layer and create a strong bond. If you are concerned about any air pockets or voids, you can use a roller or brush to help smooth out the surface before applying the next layer.

Repainting Rob's Boat Part I: Sanding


If you’re looking for a good grit sandpaper to use on your fiberglass boat, I would recommend using either a 80 or 100 grit. These will work well to remove any oxidation or stains that may be on the surface of your boat. Just be sure to follow the manufacturer’s instructions on how to properly apply and remove the sandpaper.

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