Unsaturated Polyester Resin Vs Epoxy Resin For Boat Repair Projects


If you are considering some major repair or build a boat that involves fiberglass. In that case, you are attempting to decide whether unsaturated polyester resins is worthy enough to add expenses of utilizing epoxy instead of  unsaturated polyester resins for the boatMost of the DIY’s (do-it-yourself’s) have learned that the epoxy’s adhesive bonds are much more robust than polyester resin. 

Still, two additional features have the edge over in favor of epoxy, particularly for structural repairs. But unsaturated polyester resins a never-ending confusion of which one would be optimal for use epoxy or polyester resin? So in this article, below, we have precisely explained everything in detail along with the differences, which would be helpful for you in determining which resin meets your needs best.


It is discovered in another of epoxy’s natural attributes during our test of flexibility. Its dual-edged potential to detain a fantastic adhesive quality and extension characteristics. However, this is not an overly specific valuable quality, as it is discovered that resin’s dollop chips are neither much stronger nor much more complex than the polyester resin. 

Still, considering the fiber reinforcement, the whole fact modifies. What happens is the feasibility of the highly adhesive resin adds ultimate stretch to maintain the resin matrix unimpaired as the fiber bundles incorporating the laminate take up the load.

This cooperative relationship between resin matrix and reinforcement fibers is entirely contradictory to what was discovered in the ancient days of Ferro cement boat building. The composite structure is based on a matrix in the Ferro cement boats, which will miserably fail before reinforcement can be wholly engaged.

However, epoxy’s elasticity can be well-calibrated to the fibers it locks in place. The merits are most often post-cure epoxy synthesized hulls to increase the hardness and stiffen panels. 

Impactive resistance:

For destructive testing, there is something to be said, an attempted and proven approach to engineering that still has etched its place even in the period of finite element analysis. However, point-load drop resting has exposed some visible results and equally essential lessons. 

First of all, to achieve panel stiffness, you can use the core materials and lesser units of FRP reinforcement. But when it comes to maintaining a hovering log, bow of another boat, or the pliant end of our jig from entering a structure. Therefore, there is no substitution for skin thickness.

Based on strength per weight, it is discovered that epoxy resin and carbon fiber reinforcement provide the ultimate resistance to penetration, even exclusive than the Kevlar material. The latter has excellent corrosion resistance, but it did not resist and point loading and epoxy laminates/carbon fiber.

In our beginning point-load testing of a broad range of FRP sandwich samples, we discovered that the damage could be reduced caused by the administered drop test by maximizing the laminate skin thickness. Proceeding from two to two layers of ten-ounce cloth on each side of the core was enough to reveal consequential diminishing damage caused by the controlled impact.

The next question you must ask yourself is whether replacing epoxy resin with Polyester resin for Boat also enhances the impact resistance? Our findings results reveal an increase in point-load resistance connected to the switch to epoxy. It appeared to be the different measurable gain, but the different epoxies’ differences were comparatively much more minor.

Significant differences between Epoxies and resins:

Some of the critical differences between resins and epoxies below will assist you in choosing whether Unsaturated polyester resin for boat is an optimal choice or not:

1. Bonding strength:

Epoxy is popularly known for its capabilities for higher bonding. An epoxy possesses a robust strength that can hold up to 2000lbs per square inch, whereas a polyester resin can’t withstand less than 500lbs per square inch.

2. Resistance to wear:

Epoxy is more resistant to cracking, peeling, and wearing and damage or corrosion from a chemical reaction or environmental degradation. On the other hand, polyester resin is more delicate and can be used only for low-stress use or temporary fixes.

3. Cost comparison:

Epoxy is typically more expensive compared to resin because of its formulation requirements and strength. Resin is exclusively famous for jewelry and cost-efficientness. As being easily affordable, you can effortlessly attain what you pay for.

4. Resistance to moisture:

No doubt epoxy is ultimately moisture resistant, and specific construction can even be applied underwater. On the other hand, polyester resin for boat would not be an attractive choice. It has less resistance to moisture and is also considered a water-penetrable means that can get damaged easily.

5. Curative duration:

Although the curative duration varies for both resin and epoxies, based on the temperature and formulation at use, undoubtedly, resin possesses a speedier curative duration. It can be either better or worse, depending upon the speed you want to complete your project. However, both products can be influenced somewhat by lowering or raising the temperature before use. Therefore, specific epoxies are also composed for use in hectic temperatures.

6. Odor:

When it comes to odor, polyester is far less pleasing to work with compared to epoxy. No doubt its configuration is done much faster; it has etched its name for stinking poorly enough to make you breathless. So make sure to utilize correct ventilation when applying both resins and epoxies.

7. Shelf life:

There is no doubt that epoxy product lasts for extendable duration than polyester resin’s shelf life does as long as it has not been combined. For instance, you can expect to store epoxy in a garage for many years or more without losing its potentiality. On the other hand, resin get’s much more insubstantial over time.


From the above-given information, both resin and epoxy’s characteristics are discusse precisely, and no doubt each one is the best respect to the circumstances.

So it is pretty evident that polyester resin for boat is not a good choice. Still, polyester does have some characteristics that fit perfectly in the picture, like laminating fiberglass cloth into cracks or holes.

However, thickened polyester rein is also excellent for non-structural repairs, such as screw holes and gauges and making cosmetics. So it is concluded that epoxy resin is exclusively stout when it comes to adhesiveness, and no doubt it sticks excellent to boats.


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