Fiberglass hulls were once thought to be impervious to the harsh
marine environment, but this is not always the case. All kinds of
different problems can be found with today’s hull construction, some
only cosmetic in nature, others involving complete hull delamination,
resulting in large repair bills if not caught in time !!!
the mid to late 60’s when fiberglass was being introduced as a new
construction material to replace plywood and mahogany planked
vessels; all was well for a few years. Manufacturers such as
Chriscraft used a solid laminate lay-up, with no core materials,
just a ton of resin and matting which were put together by hand.
Today, these hulls are showing no signs of construction failure. As
time went on, other manufacturers got into the glass game and
started to develop hulls constructed of a “sandwich” laminate which
consisted of an outer layer of FRP (fibre reinforced plastic) then a
core material, usually end grain balsa wood and a inner layer of FRP.
This type of lay-up was used for many reasons, mostly because of
the cost factor, as a cored construction hull was less expensive to
manufacture than a solid laminate of FRP. This also resulted in
keeping the boat’s weight down to improve fuel economy. Sandwich
cores were the standard type of construction for quite a few years
and are still being used today. A few years back, manufacturers
started to experiment with different types of core materials such as
polyurethane foams and other various man made materials, again to
save on costs and to further reduce the vessel’s weight for better
What does this mean to the boat owner??
Over time, water can get into the core material of the hull and
decks and cause a multitude of problems, from delamination of the
layers to total laminate failure if not noticed and repaired
promptly. Water can get into the core material in many ways, from
poorly installed thru-hulls, cracks and gouges caused by collision
damage or through deck hardware and fittings not properly bedded in
the sealing compound. Once the water migrates into the core material
it will stay there and, over time will cause all kinds of headaches
for the boat owner.
Another big problem with FRP hulls today is “osmosis“. This is a
condition that results from water migrating into the outer layer of
the hull and creating gelcote blisters below the waterline. The
blisters can range in size from small “crescent moon” shaped gelcote
cracks to big raised bubbles the size of a pop can bottom. Osmosis
is caused by water entering the outer laminate and seeking out the
dry areas of the matting, soaking into the strands of fibreglass.
Most of the severe cases of osmosis can be contributed to poorly
manufactured hulls, where the fiberglass matting was not properly
wetted out with resin during the lay-up of the hull, this is a
common problem. Boat builders today do not construct boats the way
they did back in the 60’s and early 70’s. I have seen boats not even
a year old suffer from some of the worst blistering possible !!! All
the major boat building companies have blistering problems with some
of their hulls; no one boatbuilder is any better than the other.
Most cases of osmosis are not fatal to the structural integrity
of the hull, but should be addressed and repaired as soon as
possible. The problem with osmosis is that it will create a
stumbling block if you ever try to sell your vessel. Most smart
buyers will obtain the services of a Marine Surveyor, and upon a
“out of the water inspection” this condition will be noticed. I have
seen a lot of deals fall apart due to an osmosis problem. Most times
the owner will say “I never knew the boat had osmosis” and he is
probably right, because he never inspected the hull bottom for
blisters. To the layman’s eye this problem could go unnoticed. An
“up close and personal” inspection of the bottom may not be possible
due to various reasons, such as heavy layers of anti-fouling paint,
or the bottom being covered in algae. Marine Surveyor’s have the
knowledge and experience to look for these kinds of problems. If you
are selling your vessel and you know that your boat has blisters,
beware. This problem will be picked up by the Surveyor and will
become an issue when negotiating over the price, believe me I have
seen this happen many times.
What can you do as a boat owner?
We offer all kinds of services for your fiberglass vessel, which
include “guaranteed” professional osmosis repair, delamination
solutions, re-bedding of underwater thru hulls and deck fittings,
core replacement for hulls and decks, stringer, bulkhead and transom
replacement. We also offer full gelcote repair services for any kind
of fiberglass boats from PWC’s up full size cruisers.