Resins play a multi-purpose role in boat building. They are used for gluing, fiberglassing, moisture sealing, and coating or encapsulating. Resins can also be used as a fairing compounds. There are many commercial products and types available. Before using these materials, users should have in mind the following basic information.
Types of Resins
A wide range of resins are commercially available today. There are three main types of resins for boat building:
Epoxy resins : These resins are suitable for wood boats, since they are less porous than the rest of the available types and present a remarkable ability to cover fillings. They are the most expensive type of resins.
Polyester resins : These resins are not recommended for wooden boats. On the contrary, they are more suitable for GRP boats. They are the cheapest ones.
Vinyl ester resins: This is a less popular type of resin for boat building. The cost of vinyl esters comes between the one of polyesters and the epoxies. They offer more effective moisture protection than the polyesters, and a more reasonable price than the epoxies, although the latter are considered to be the top in moisture resistance. Vinyl ester resins also present great mechanical properties; they are tougher and more flexible than polyesters. They can also endure extreme fatigue and high temperatures without distorting. However, this material is more difficult to process and requires good ambient conditions during cure in order to be more effective.
Applying Procedure for Epoxies, the most Popular Resins
Preparing the Mixture
- Mixing the resin with the hardener in a plastic or metal container, is the first step. The mixing ratios depend on the specifications of each product.
- The two ingredients should be stirred together thoroughly. A power mixer could also be used.
- Fillers could also be added in the mixture. The purpose of fillers is to thicken the mixture in order to be more suitable for bonding or fairing.
Preparing the Surface
- The bonding surfaces should be firstly cleaned of any oil, wax etc. by using acetone or any other appropriate solvent. The surface should be wiped with paper towels before the solvent dries.
- Non-porous surfaces should be sanded smooth.
Applying and Curing
- The time period between mixing and applying is called "pot life" and depends on the product's requirements.
- After the mixture is ready it should be applied to the bonding surfaces with a brush, foam roller, or plastic spreader.
- The resin should then be left to cure. It takes approximately 24 to 48 hours.
- Curing times will also vary according to the mixing ratios.
- The repaired surface should then be sanded with a 120-grit sandpaper to remove most of the excess material and a 220-grit sandpaper to polish the area.
This is the general procedure followed. Users should always consult the manufacturer's instructions.
Hazards and Safety Precautions for Epoxies
The use of resins, especially epoxies, entails health risks and certain safety measures should be taken during use:
- The ratio of resin to hardener should be carefully measured. Wrong ratios result in curing problems.
- The process of curing generates heat. If the mixture begins to heat up it should be quickly moved to a cooler environment.
- The mixture should be used after the reaction is complete and has cooled
- Glass or foam containers for epoxy resins should be avoided because of the potential exothermic heat build-up risk. Manufacturers recommend the use of plastic, metal or wax-free paper containers.
- Long exposure may cause a skin rash, so skin contact should be avoided.
- The use of gloves is necessary.
- In case of skin contact, an appropriate cleaner such as vinegar or a hand cleaner should be used. Solvents or acetone should be avoided.
- Fumes should not be inhaled.
- Users will have to make sure that they are not allergic to these materials.
Users should have in mind that the cheaper the resin the more diluted it is and of low quality. It is recommended that users only use well-known products.