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Polyester vs Epoxy Resin for Boat Repair? What’s Better?

A collage photo of a hand holding a brush.

If you are thinking about using polyester to repair your boat, you need to rethink your decision. While 0polyester proves to be a great adhesive, it is not the best choice for boat repair. Polyester lacks the strong bonding material that you find in epoxy.

If you are going to use Polyester resin for installing fiberglass while building a boat, then by all means consider using polyester. What you need to know is, that if you plan to apply a polyester lamination resin, you need to make sure your project is not exposed to the open air. Why? Because polyester lamination resin does not fully cure when it is exposed to the open air.

When you decide to repair your boat, you want to use a strong adhesive and bond well. P+olyester has the right texture, but not the right adhesiveness, so you need to do your best. For this reason, it is best to use epoxy.

If you decide to use epoxy, make sure you purchase one that offers the highest quality.

It might cost a little more, but at least you will get a great outcome. Epoxy is made from a combination of substances. These substances bond together to create a long, strong, adhesive finish that is heat and cold resistant. It reminds you of durable vinyl.

Most people prefer using polyester because it is cheaper. Nevertheless, price should not be the only factor. If a large repair job calls for a substance that provides more tenacity, then go with it.

You should never compromise quality over price.

It is beneficial in the long run to pay a little extra for the best, instead of paying more money for a simple repair. During the job right the first time is cheaper. As stated earlier, polyester is not the only choice, nor is it the best choice for some repairs.

Best Uses for Polyester

Close up photo of a hand holding a brush repairing a boat.

While polyester might not be the right choice for boat repairs, there are other projects that polyester is perfect for. For example, if you are going to use a gelcoat finish, the filling or the lamination will need to be completed using polyester. In this case, epoxy will not provide the best consistency.

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Depending on the size of the repair, you could spend a lot of money on epoxy compared to polyester. Therefore, polyester would be a cheaper and better alternative, especially for larger repairs.

Since polyester resin is great for laying up fiberglass, it is best for repairing fiberglass boats. Fiberglass is a type of fiber that is made using glass fibers. Fiberglass is strong, lightweight, less brittle, and durable.

In docking areas where boats are kept in saltwater, fiberglass is used as a protective shield to prevent corrosion. However, the most popular use of polyester resin is for reinforcement of areas that are subject to distress, such as bulkheads or stringers.

Polyester only provides a temporary fix. What this means for major repairs, the polyester resin should not be considered. Perhaps, if you need to repair your boat until you can receive a better product, then that 0is a different story.

Just remember not to let the resin remain on too long because the compounds will begin to break down.

In all essence, it is fair to say that polyester resin does not stand up to most resins, especially epoxy. Why? Because polyester resin does not bond well with epoxy resin, a gelcoat is necessary. Some compounds lose their potency due to temperature changes, environmental conditions, or other factors.

However, some compounds do hold together better and last longer than others.

Best Uses for Epoxy

A man puting epoxy resin on a boat.

Epoxy offers the most effective adhesiveness for boat repairs because of its ability to bond under high stress and extreme pressure. Epoxy can hold together approximately 2000 pounds per square inch, which is 1500 more pounds per square inch than polyester resin.

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Compared to polyester resin, when it comes to preventing a surface from peeling, cracking, chemical damage, environmental degradation, and corrosion, epoxy resin offers the ultimate protection. It is also important to mention that epoxy is moisture resistant, and in certain cases, it can be applied underwater.

Although polyester resin has minor resistance to moisture and is water permeable, polyester resin does fracture easily. However, curing times vary for both epoxy and polyester resin. However, both resins can be manipulated depending on how soon you need to finish your repairs.

If you do not plan on completing your repairs right away, you can store your epoxy for up to several years if the epoxy is not mixed. Polyester resin has a shorter shelf-life expectancy. Water safety is as important as road safety.

When you take your boat out on the water, for the first, second, or third time, you want to be sure you have repaired your boat properly.

There are no second guesses, and sometimes there are no second chances. Whichever substance you choose, whether it is polyester resin or epoxy, you must live with your choice. Before you make a final decision, be sure to check out the ingredients and ask the necessary questions.

Is Polyester Resin Going to Repair this Damage?

Before you can get to the answer to this question, you must determine if the damage is small or major. For a small repair, you can use polyester resin, if the damage does not require a gelcoat. If a gelcoat is required, you are better off using epoxy.

Can I Put Epoxy Over a Polyester Resin Repair Temporarily?

A mans' hand holding a brush repairing boat.

This is a tricky question, and the answer may vary depending on the type of repair you need to perform. If the repair does not require extensive work, and you need to wait to get the epoxy to properly do the work, then yes. Go ahead and do a temporary patch job, but be sure to repair the boat using the proper substance as soon as possible.

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What if I Need to Add a Gelcoat?

If your boat requires a gelcoat, you can apply a polyester resin if it does not require any more repairs. For example, if you nicked your boat, and your boat accumulated a small hole, you can use a gelcoat. The gelcoat functions as a barrier and prevents water from rising in the boat.

However, if the hole is large, polyester resin might not hold as well.

Why is Polyester Resin Popular?

A worker measuring a fiberglass to repair a boat.

Polyester resin is still popular among boat mariners due to its low cost. You might think you are getting a good deal on a cheaper product, but is the quality good? When prices are high, it becomes a choice between what is affordable and what is the better product.

However, when safety is involved, price should not be a consideration, nor should it be given a second thought.

Are There Any Other Alternatives?

Vinylester Resin is a combination of polyester resin and epoxy. If you want to avoid loading shocks on your boat, the vinyl ester is the answer. It is heat resistant, stretchable, crack-resistant, and can stand up to low velocity, ambient temperatures, and moisture.

Since vinyl ester compound can change with some manipulation or chemical reactions, it is considered a double bonding substance. For this reason, it is a flexible substance that can be molded, but it cannot be reused if it is in a waxy state. Therefore, if you want to complete the best repair job on your boat, epoxy is the way to go.

It has little to no limitations when it comes to adhesiveness, bonding, or temperature deficiencies. It is waterproof, moisture resistant, heat resistant, and most importantly, it can hold up to a ton of pressure. Epoxy provides the ultimate barrier and should be used for all major boat repairs, where polyester is not the best choice.