The difference between polyester, vinylester, and epoxy—and why it matters.
Leading yacht builders today use vinylester in the outer layers (for waterproofing and osmotic protection) and polyester in the non-critical inner layers. This is a common and smart mix in catamaran construction: better than polyester alone, but more affordable than full epoxy. HH uses only epoxy. Although more challenging to work with, epoxy has so many advantages that I can’t imagine you’d want anything else. Here’s an overview:
✅ Epoxy:
Stronger adhesion to various materials
Better resistance to water and osmosis
Higher chemical resistance
Stiffer and stronger
More expensive than vinylester
✅ Vinylester:
Cheaper than epoxy but more expensive than polyester
Better resistance to water and chemicals than polyester, but less than epoxy
More flexible, better impact resistance than polyester
Easier to process than epoxy (comparable to polyester)
✅ Polyester:
Cheaper and easier to process but has less strength and durability
Easier to work with
⚠️ Limitations and Considerations:
Adhesion: Epoxy adheres better to carbon than vinylester; vinylester adheres better than polyester, but epoxy remains superior in fiber bonding.
Strength: Epoxy provides higher strength and stiffness values—preferred for critical applications (e.g., masts, high-load zones).
Temperature Resistance: Epoxy has higher heat resistance (Tg) than standard vinylester.
Polyester is cheaper and easier to process but has less strength and durability.
For osmosis prevention and high-end applications, epoxy is often chosen; for the production of more affordable boats where flexibility and cost play a role, vinylester is often used.
In summary:
Epoxy: Higher quality, better protection and strength, but more expensive
Vinylester: Good middle ground between epoxy and polyester
Polyester: Suitable for smaller boats where stiffness and strength are less important. It’s cheaper and easier to process but has less strength and durability.
Property Comparison:
| Property | Polyester | Vinylester | Epoxy |
|---|---|---|---|
| Adhesion | Limited, mainly to polyester | Better than polyester, less than epoxy | Very good, to various substrates (wood, metal, old laminate) |
| Osmosis Resistance | Moderate | Good | Very good |
| Stiffness | Less stiff | Slightly stiffer than polyester | Stiffer and stronger |
| Price | Cheap | Mid-range (more expensive than polyester, cheaper than epoxy) | Expensive |
| Warping/Shrinkage | More shrinkage | Less shrinkage than polyester | Minimal shrinkage |
HH uses prepreg carbon in many areas, where the fiber is already impregnated with epoxy during production. These so-called “prepregs” are incredibly strong relative to their weight. Daggerboards are tested to support the full weight of the boat, while rudders and rudder stocks are indestructible.