How to do your own fiberglass
repairs
Fiberglass repairs are things most
people don't want to get into. For those of you who choose to do it yourself,
this paper will teach you the basic things you need to know to make strong
professional repairs of any type on any fiberglass boat. To start, you need to
plan out what exactly you want to repair. This is very important because it will
allow you to determine how much of what type materials you will need. For
structural repairs of cracks etc you will need to make a repair which is 12 to 1
times the thickness of the fiberglass in the area of the crack. To better
explain, if the crack is in a piece of fiberglass 1/2" thick, your repair must
be 6" wide. You would begin by grinding the area on either side of the crack
with a steady taper towards the center. You would then place a small strip of
fiberglass with an overlay of 1" either side of the crack, followed by another
layer 1/4" to 1/2" wider than the one below it. repeat this procedure until you
reach the edge and have a slight bulge which when cured you will grind down.
Always use a laminating table to wet out your fiberglass. This will ensure good
wetout and therefore good bonding. Also you must use a metal fiberglass roller
to remove excess resin and air bubbles. Simply roll the laminated layers with
the roller as you would a paint roller, squeezing out the excess resin. It is a
good practice to have several containers filled with acetone for cleaning your
equipment. Use one container to initially clean your equipment followed by a
second container for final cleaning. This will allow you to get the most out of
your acetone.
Fiberglass projects come in all shapes and sizes. Floors,
transoms and stringers are the most common. When repairing one of these
structures, you will be using core materials in your repairs. You have several
choices for core materials and they are project dependant. Synthetic materials
like Divinycell, Cledgecell and others are foam boards available in several
densities as well as thicknesses. When these cores are used, if done properly,
will be the last repair ever, since they will never rot or fail. Other core
materials are marine plywood, which generally will have a life of 8 to 10 years
and exterior a/c birch plywood which will last 3 to 5 years. Generally,
synthetic cores are installed using a vacuum bag procedure which creates even
pressure on the laminate and pulls out excess resin, creating the ultimate
laminate product. All repairs involving transoms, stringers or floors will
require filler products to give you the best results. You use fillers to fill
sharp corners which when laminated would result in air pockets and weak spots in
your repair. By using Aerosil, Microballoons or even talc powder mixed with
resin or gel coat you can fill these edges, fair them out and create a
continuous surface for the fiberglass to bond to. Please note, When replacing
stringers in a hull, you must support the hull to prevent it from flexing or
deforming prior to laminating the new stringers in place.