Mike,
Have had success in patching similiar types of damage by using #60 stainless
steel expanded metal (similiar to lathe used in stucco construction).
Measure the length and width of the damaged area in the hull and cutom cut
the expanded metal interior patch to extend 1.5 to 2 inches beyond the edges
of the damaged hull materials. Shape the expanded metal screen to match the
contour of the interior hull slope. Remove the expanded metal screen and cut
out the damaged hull material; we use an air driven die grinder and "V"
shaped router bit to cut through the entire fiberglass shell material. An
area slightly larger than the damaged area is cut and removed from the hull.
The expanded metal is put back into place and Durimix or Automix (two
component, quick setting epoxy) is used to secure the metal to the interior
hull. The cure time for the Durimix or Automix is around 20 minuted at 70
degrees F. This expanded metal gives the hull structural support in the
damaged area and acts as a spline to support the replacement fiberglass for
the exterior repair. I would also use fiberglass or kevlar mat and marine
grade epoxy to seal the interior side of the expanded metal patch. The mat /
epoxy material can be smoothed and blended to the fiberglass inner hull
(which surrounds the expanded metal patched area) using a plastic bondo
spreader. Allow the mat /epoxy patch cover to air dry and accelerate the
curing time with an IR heat lamp.
The exterior fiberglass patch can be made with fiberglass mat / resin or
stranded fiberglass paste that is catalysed with MEKP. I prefer the
stranded fiberglass paste as is quicker and can be bonded to the expanded
metal spline using the same type of plastic bondo spreader. The cured
polyester fiberglass paste can be sanded with #50 grit two (2) inch diameter
disc mounted on a right angle air drive die grinder. This grinder makes
very quick work of smoothing our the peaks in the fiberglass where is ready
for the second layer of fiberglass material. Repeat the same procedure for
the second layer, building up approximately a 1/8" to 3/16" layer of
fiberglass paste, allowing to cure and grinding smooth with the dir
grinder/sanding disc. Continue to add ply layers of fiberglass until the
material matches the thickness of the fiberglass on the adjoining hull.
Block sand the top layer to match the contour of the adjoining hull. A
catalysed marine grade polyester filler should be used to fill pinholes in
the top layer of the fiberglass and sanded smooth with a 180 grit DA sander.
Would progressively move to a 400 grit, and 800 grit DA paper and repeat the
same process. The next step is to use a penetrating marine epoxy primer to
coat the polyester filled patch area. Mix component A & B according to
manufacuturers instructions and apply with a close nap paint roller. The
first layer will penetrate into the polyester material and fill voids in the
material. Allow to flash / cure according to manufacturer's guideline. The
IR heat lamp can be used to accelerate the curing process. When cured,
lightly sand with 600 grit DA paper to remove roughness and trash in the
coating. Apply a second coat of epoxy to the patched area and blend onto
the intact gel coat adjoing the patched area. This epoxy coating makes the
patched area impurvious to water penetration of the patched area. Upon
curing, again sand smooth to remove the roughness and trash in the coating.
The hull is now ready to receive the top coat finish: can use gel coat, or
single stage urethane. Color matching of existing gel coat has presented
problems to many attempting repairs. Mike, this is your call.
Judson
"Bonasa" wrote in message
...
Hi,
I feel like I'm just barging in here as I'm not a regular poster to this
group, but I'm hoping for some advice. I've already gotten a lot of good
information from Google and doing a Dejanews search of past posts to this
group, but nothing specifically addressing my situation.
I recently ended up with a 22' sailboat for a very good price. The reason
it
was so cheap is there is damage to the hull; a crack about 3 feet long.
The
gelcoat and fiberglass are cracked clear through, from the inside looking
at
the crack you can see daylight. It looks like the side got bashed into a
dock, it's about at the right level and I can't figure out what else would
cause such a long crack.
I'm using Don Casey's Sailboat Hull & Deck Repair book as a reference
manual. The method is pretty straight forward but all the illustrations
and
the description of how to make the repair seem to be geared towards a neat
round hole. Once I cut out the ruined fiberglass I'm going to have a hole
about 3.5 feet long and 4 inches wide. I can get to the crack from the
inside, so I'll be laying acrylic over the exterior and applying the
gelcoat
as shown in the book. But because it's a horizontal repair instead of the
neat little circles of mat shown in the book I'm going to have to use big
long strips in progressively longer strips.
Even with the 12:1 taper I'm concerned about the strength of the repair.
Fortunately the crack is not on a structural part of the boat but is this
going to be a repair I can trust to hold with a mechanical bond?
Any advice, comments, or similar experiences would be greatly appreciated.
I've worked with fiberglass and epoxy before but only on kayaks. So I'm
not
a total stranger to the process but this way more than I've ever tried to
tackle. Feel free to throw in some moral support if you feel so inclined.
Thanks for any help and sorry this is so long.
Best Regards,
Mike
--
He is your friend, your partner, your defender, your dog.
You are his life, his love, his leader. He will be yours, faithful and
true,
to the last beat of his heart. You owe it to him to be worthy of such
devotion.
-- Anonymous
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