| Fiberglass
boat stress
cracks
Wow! What
a great time we had today, this boat is awesome!' you think as you
step off of your new boat and onto the dock at the marina.
Filled with pride and contentment you browse around to see who else is
around watching your homecoming with your new cruiser. You reach for
your significant others hand to help her off the boat, then the kids.
With everyone off the boat and standing safely on the dock you take in
a deep breath and with a smile, and you sigh. You stand with
your gaze fixed upon the new boat, unable to break your eyes away,
regardless of the impatient pleas of the kids to get going, and
unaware of "the look" your lady is giving you as she looks
at you, then the boat, with her arms folded with a wry look on her
face. If looks could kill! But really, you do intend to pay attention
to her again at some point in the future! One more quick scan across
the surface of the boat and you will get going. With another
deep breath and a sigh, you turn to walk away with the family. But
after the first step you take in the other direction... something
stops you. You quickly turn back to the boat, eyes wide and face
flushed... what the heck is that... that crack! You step on the boat
and rush over to it for a closer look. But wait, there's more! One
here, one there, and one over there... and one in the sink too! They
weren't there this morning when you left the dealers!
Unfortunately, the scenario above
realistically, does happen all too often. Little hairline cracks
appearing here and there on the surface of the boat. They can
appear anywhere, in and around hatches, sinks, shower stalls, bridges,
steering columns, decks, transoms... you name it.
The cause
The causes for stress cracks are much
the same as for blistering. We won't go into great detail here,
but suffice it to say that stress cracks occur because of voids under
the surface of the gelcoat, and or a lack of strength in the
underlying fiberglass or compounds used in the sub structure of the
boat. For more details on some of the things that can go wrong
in the fiberglass during the manufacturing process please refer to the
blistering article. (Click
Here).
When these voids are present, or when the fiberglass is lacking in
strength because it was not mixed properly, or because enough
fiberglass was not applied it paves the way for stress cracking.
Your boat body will flex some even during normal use. Fiberglass
is strong, and if mixed properly, and if enough is applied, the
fiberglass will take up much of that flexing. But gelcoat is
very brittle and has no strength to it. When the boat flexes and
twists, the fiberglass flexes and twists. When that happens, the
gelcoat can't flex with the fiberglass, it just cracks. Hence
you get these little hairline cracks.
What must be done?
Once a stress crack begins, it can
travel for great lengths. Sometimes a short one or two inch
stress crack can travel the length of the boat. This is because
once that fiberglass underneath has flexed, and once the gelcoat has
given way, the bond has been broken. A separation has occurred.
Then simple heat and sunlight is enough to cause that gelcoat to
continue it's meandering course across the surface of your boat.
Stress cracks can be successfully stopped however. The crack
must be ground out thoroughly. It needs to be ground deep enough
to reach good fiberglass (fiberglass that is not whited out or
"shattered") and it needs to be ground out wide enough to
reach the good fiberglass on either side and end. For voids, (a
void is a place where the fiberglass had a low spot in it and the
gelcoat didn't touch the fiberglass to bond with it) they need to be
ground out and followed down through all the way till the end of the
void is reached. Then new fiberglass must be applied. And of
course followed up with the finishing touches of shaping and
regelcoating. Normally this process will do away with the stress
crack.
Sometimes a stress crack can reappear though, even if all the repair
work was done properly. Sometimes if large surface areas are
compromised underneath, in the fiberglass, stress cracks can reoccur.
Though the portion you had fixed may be good and strong now, if that
fiberglass surrounding the area is weakened and not properly wetted,
then it is going to flex more than it should and problems are going to
continue.
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