More than 95% of all boats, truck & car bodies made of fiberglass are made primarily of E-glass, an orthothalic polyester resin and isothalic polyester gelcoat.
Therefore, items constructed with these materials should be repaired with the same or compatible material. LBI’s 301 orthothalic polyester resin is a good choice for most repairs. It provides a chemical bond to the existing laminate with similar strength & flexural characteristics.
Ortho polyester, isothalic polyester and vinylester resins are compatible, they all have styrene (commonly known as the “fiberglass smell”) and chemically bond to one another.
When higher strength, bond and water resistance is required (such as keel, rudder repair, or out-board transom replacement) use LBI’s 302 Isothalic Polyester Resin.
To achieve the highest bond strength and water resistance use LBI’s 901 Vinylester Resin.
Vinylester is essentially a styrene modified epoxy resin. It adds excellent strength, rigidity, adhesion, water and chemical resistance.
KEEP IN MIND
- Epoxy adheres to wood much better than polyester does. To cover wood, a laminate using epoxy resin and 10 oz, cloth will yield a much better job than 10 oz. cloth and polyester resin. The epoxy/cloth laminate is comparable to using polyester resin with 3/4 oz. mat and 10 oz. cloth however the epoxy laminate requires much less labor to fair.
- A polyester laminate job is somewhat less expensive in material costs than an epoxy laminate project of the same size.
- Fiberglass mat should not be used with epoxy because the binding material in the mat will NOT dissolve in epoxy resin.
- Either mat, cloth or woven roving may be used with polyester or vinyester resin.
- Since mat sticks much better to wood than does cloth, always make mat your first layer against the wood to be covered in a polyester laminate project.
- We recommend using a layer of mat between layers of cloth for maximum adhesion between layers.