Common fiberglass resins are two-part mixtures. When the catalyst (or hardener) is mixed with the resin, the resin "cures" or hardens.
It is important to mix the proper ratio of catalyst to resin. With too much catalyst, the resulting product will lack the proper design strength. With too little catalyst, the resin may never solidify - leaving you with a BIG, STICKY mess to clean up.
The resin cures in an "exothermic" reaction - it gives off heat.
A LOT OF HEAT! Be careful - it can burn. (Don't ask me how I know!)
The amount of time required for the resin mixture to "gel" is called "pot-time". Depending on the application, different catalysts can be used to lengthen (or shorten) the pot-time as well as the time to fully harden the resin.
Polyester and Epoxy each have strengths and weaknesses. Each type of resin works well with the common types of cloth and tapes. Common additives and admixes also work well with both types of resins.
The primary functional difference between the two types of resins is that the epoxy resins form much better "secondary bonds", or bonds with previously cured fiberglass.
This characteristic of epoxy resins make them the preferred choice for high quality, durable repairs to fiberglass boats.
Of course, there is a downside to epoxy resins!
They are generally more expensive than their polyester counterparts. When dealing with the limited quantities involved in most do-it-yourself repairs, though, the price difference should not be a major factor.
There are many brands of epoxy resins available in consumer sizes. One of the most popular and user-friendly (and our general preference) is West System 105 epoxy. West Systems makes quality resins, admixes, and other accessories. Their resins are available in a variety of package sizes, and are available with easy measure dispensing pumps. These pumps really take the guesswork out of mix ratios!
A convenient starter kit
A convenient West Systems starter kit: Here
is available from Amazon. It contains the standard resin, hardener, and metering pumps.
This kit should suffice for small to medium size repairs.
Gallon sized kits are also available!BACK to Fiberglass Basics from Fiberglass Resins