How To Fiberglass A Boat

If you know to to fiberglass a boat, you may find yourself coming up with all sorts of creative things to do with fiberglass or even just with the resin that is used with the fiberglass. Fiberglass is made up of strands of glass. Depending on its use at the time, you may want to use woven fiberglass, which is more like a sheet of flat material great for working with flat surfaces. The strands of glass used by themselves are also very easy to work with, but without a chopping gun (chopper), they can be difficult to manipulate. For the purposes of learning how to fiberglass a boat, we will be using the woven fiberglass material for ease of use.

Items needed: 

Depending in the size of the project, you will need a variety of materials. Please note that most, if not all of these materials can be found at paint and bodywork stores. 

  • Fiberglass woven material
  • Resin
  • Catalyst
  • Accelerator (optional and recommended only for experienced users)
  • Face mask
  • Appropriate size brush with wooden handle (2" brushes normally work fine)
  • Cardboard cups or buckets
  • Sandpaper in either 80 grit or 40 grit
  • Acetone
  • Metal utility knife and blades
  1. Be safe! Fiberglass and its counterparts come with some health and environmental hazards. Be sure to observe proper disposal laws for your area. You can learn about safe practices by contacting the Environmental Protection Agency. For your own protection, be sure to wear a face mask so that you can avoid the fumes associated with fiberglass production. Do not use plastics of any kind as the catalyst tends to destroy the material.
  2. Prepare the area. To prepare the area as you learn how to fiberglass a boat, you will need to "rough up" the area with the sand paper. If you do not do this, the fiberglass will simply peel off once it is dry. Clean the area thoroughly. If needed, mask off areas that you do not wish to fiberglass. Roughly measure and cut your fiberglass by laying it on the area to be glassed. It is fine if there is an overhang of fiberglass as you can trim this later.
  3. Mix the resin. The resin is what makes the fiberglass transform from a flexible material into a solid, hard material. Mix the resin with the proper amount of catalyst by measuring it as in instructed on the resin can or catalyst can. There are a variety of types of catalyst and each of them have their own ratio suggestions. Note that once the catalyst is mixed with the resin, a chemical reaction occurs, limiting the amount of time that the material is easily manipulated.
  4. Apply the resin. Using your brush, you will apply a light coat of the resin to the area where the fiberglass will go.
  5. Add the fiberglass. Lay the fiberglass material on the resin.
  6. Coat the fiberglass. Using your brush, apply the resin in a thin layer that saturates the fiberglass. Apply a thin layer to the entire amount of fiberglass, giving the resin a chance to soak in. You can add more as needed later on.
  7. Remove air. When the fiberglass and resin hardens, air bubbles that are left in the glass will create hard air pockets as the fiberglass dries. Later, these pockets can be easily burst and cause flaws in the final project. Remove the air bubbles by applying pressure with the brush, blotting the resin into the fiberglass until it adheres to the area below the fiberglass. Remove any air bubbles by applying slight pressure to the brush until you no longer see or feel the air bubbles.
  8. Cut the excess material. Test the hardness of the material. Once the material begins to dry, trim the excess fiberglass with the knife. It's best to wait until the fiberglass is hard enough to cause it to not be flexible anymore. The knife should cut easily through the fiberglass without dragging it off of the underlying material.
  9. Clean up. Fiberglass a boat and you will likely find you have a sticky mess! Clean the area before it hardens by washing the area with limited amounts of acetone.