Fiberglass Buyer's Guide

1. Introduction to Fiberglass

Whether you're building a boat from scratch, tackling repairs, or upgrading parts of your vessel, fiberglass is one of the most essential and widely used materials in marine construction.

What is Fiberglass?

Fiberglass is a composite material made from fine glass strands woven or layered together and reinforced with resin—usually polyester, vinyl ester, or epoxy. The result is a lightweight, durable, and moldable material that's ideal for boats.

Why Fiberglass is Popular for Boats

Fiberglass has become the go-to choice for boat builders and DIYers because of its:

• Durability – Resistant to corrosion, rot, and UV damage.
• Lightweight Nature – Easier to handle and improves fuel efficiency.
• Flexibility – Can be molded into complex shapes and contours.
• Repairability – Damaged areas are easy to patch and reinforce.
• Low Maintenance – No rusting or wood rot to worry about.

2. Types of Fiberglass Used in Boating

Not all fiberglass is created equal. Each type has unique strengths and ideal applications. Here’s a breakdown to help you understand what’s best for your project.

Chopped Strand Mat (CSM)

Chopped strand mat comes in a variation of weights and widths for every project. Random chopped fibers held together with a dissolvable polyester powder binder which makes it only compatible with polyester and vinyl ester resins, NOT EPOXY.

• Features: Made of randomly arranged glass fibers held together by a binder.
• Pros: Inexpensive, easy to use, conforms well to curves.
• Cons: Weaker than woven materials, so not suited for structural work.
• Best For: Hull repairs, backing layers, laminating between stronger layers.
• Resin Compatibility: Polyester and vinyl ester

Woven Roving

• Features: A heavy, crisscross weave of fiberglass yarns.
• Pros: Strong and thick—adds bulk quickly.
• Cons: Less flexible; harder to work into tight curves.
• Best For: Strength-critical areas like hulls and decks.
• Resin Compatibility: Epoxy, polyester and vinyl ester

Fiberglass Cloth

Fiberglass cloth is most common for the finish layer, with the lightweight cloths wetting out clear, you can achieve many desired results for any project. Available in many weights and widths from 4oz to 40oz we have a range of specifications to meet your woven cloth needs.

• Features: Thin and finely woven fabric.
• Pros: Smooth finish, easy to sand and shape.
• Cons: Lower structural strength.
• Best For: Finishing layers, lightweight cosmetic repairs, surfboard builds.
• Resin Compatibility: Epoxy, polyester and vinyl ester

Explore our Forged Carbon Fiber Starter Kit and 1/2" Chopped Carbon Fiber for lightweight yet high-strength projects.

Biaxial Fiberglass (Stitched Fabrics)

• Features: Non-woven fiberglass stitched in multiple directions.
• Pros: Superior strength and flexibility without added bulk.
• Cons: Higher cost and slightly harder to wet out with resin.
• Best For: Stringers, bulkheads, and structural reinforcements.
• Resin Compatibility: Epoxy, polyester and vinyl ester

Specialty Fiberglass

S-glass, carbon fiber hybrids, and other high-performance weaves fall into this category.

• Pros: Exceptional strength-to-weight ratio and stiffness.
• Cons: Pricey and often requires specialty resins.
• Best For: Racing boats, custom builds, and high-performance upgrades.

3. Choosing the Right Fiberglass for Your Project

Selecting fiberglass isn’t one-size-fits-all—it depends on the task at hand. Consider these key factors:

• Strength Requirements: Structural areas need woven or stitched fabrics.
• Weight Sensitivity: Use fiberglass cloth or carbon for weight-critical projects.
• Budget: CSM and woven roving are affordable; carbon fiber is a premium option.
• Resin Compatibility: Some fiberglass types work best with epoxy, others with polyester.
• Environmental Conditions: If exposed to UV or saltwater, choose materials designed for marine durability.

Top Product Picks:

• Thin Epoxy Resin System w/ Hardener – Ideal for general repairs and laminating.
• Clear Polyester Surfboard Resin – Great for finish work and UV clarity.

Use our Epoxy Calculator to estimate how much resin you’ll need.

4. Preparing Your Boat for Fiberglass Application

Good prep work makes all the difference in fiberglass application. Rushing or skipping steps can lead to delamination, weak bonds, or a rough finish.

What You’ll Need:

• Fiberglass (cloth, mat, or stitched fabric)
• Resin system (epoxy or polyester)
• Brushes, rollers, stir sticks
• Mixing containers
• Safety gear (gloves, goggles, respirator)

Surface Prep:

1. Clean: Remove all dirt, wax, oil, and salt.
2. Sand: Scuff the area to help the resin grip.
3. Degrease: Wipe with acetone to remove residues.

Measuring & Cutting:

• Dry Fit: Lay the fiberglass over the area to ensure a proper fit.
• Cut Cleanly: Use sharp scissors or rotary tools.
• Label Layers: Helps during multi-layer laminations.

5. Fiberglass Application: Step-by-Step

Once everything is prepped, it’s time to apply your fiberglass.

Application Steps:

1. Mix Resin: Follow mix ratios precisely.
2. Apply Resin: Brush or roll a thin coat onto the surface.
3. Lay Fiberglass: Press the material into place.
4. Wet Out: Add resin on top until fully saturated.
5. Layer Up: Repeat if needed, allowing partial cure between layers.
6. Cure: Let it fully harden before moving on.
7. Sand & Finish: Smooth it out, then paint or polish as needed.

Try our Boat Paint Calculator to plan your topcoat.

Safety Reminders:

• Work in a well-ventilated area.
• Always wear PPE—especially eye and respiratory protection.
• Store resins and solvents in cool, dry places.

6. Fiberglass Maintenance and Repairs

Over time, even the toughest fiberglass can develop wear or damage. Staying on top of maintenance helps avoid larger problems.

What to Look For:

• Cracks: Especially around stress points.
• Blisters: Often caused by water intrusion (osmosis).
• Delamination: Separation of fiberglass layers.

DIY or Call a Pro?

• DIY: Small dings, blisters, cosmetic issues.
• Professional: Structural cracks, large surface damage, or keel repairs.

Helpful Products:

• 1/4" Chopped Carbon Fiber
• Clear Polyester Surfboard Resin
• Forged Carbon Fiber Starter Kit

7. Frequently Asked Questions

Can I use any resin with any fiberglass?
Not always. Epoxy is generally compatible with all fiberglass types, but polyester doesn’t always bond well with certain fabrics.

How long will a fiberglass repair last?
With proper prep and materials, repairs can last just as long as the original fiberglass.

Can I paint over fiberglass?
Yes! Sand the surface lightly, apply a primer, then use marine-grade paint.

Is working with fiberglass dangerous?
It’s safe with precautions—always use gloves, eye protection, and a respirator when sanding or handling resin.

8. Conclusion

Fiberglass is a cornerstone of boat building and repair for a reason—it's versatile, strong, and accessible. Understanding the types, application methods, and maintenance practices ensures your project is safe, durable, and successful.

Explore our full range of Fiberglass Supplies and Resins & Epoxy to get started on your next project.

9. Ready to Get Started?

Your boat deserves the best. Whether you're reinforcing a transom or repairing a ding, we’ve got the materials and know-how to help.

• Browse our full Fiberglass Supplies collection.
• Shop high-quality Resins & Epoxy.
• Use our Epoxy Calculator and Boat Paint Calculator for easy planning.

Questions? Reach out to our team—we’re here to guide you every step of the way.