Gelcoat repair

[seapuppy]

here's how you repair gel coat..


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The host of Shipshape
Boating, John Greviskis,
shows you how to repair
and maintain the finish --
also known as gelcoat --
on a fiberglass craft.
One of the tips you'll
receive on this episode is
how to repair a ding to
your boat's exterior --
gelcoat.
Figure A
Figure B
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GELCOAT REPAIR: GETTING STARTED
From "Shipshape Boating"
episode DSSB-108 -- More Projects »
In this week's episode of DIY's Shipshape Boating, host John Greviskis demonstrates how to
repair and maintain the finish -- or gelcoat -- on a fiberglass boat.
What is Gelcoat?
Boat builders start with a fiberglass mold (figure A) that is supported by metal on the outside
(to make it structurally sound) and on the inside, a gelcoat over top of the fiberglass to make it
smooth. To get the mold to pop out, a release wax is used. After waxing the mold thoroughly, a
polyester-based material called "gelcoat" is sprayed on every square inch of the mold.
A chopper gun is then used to shoot out chopped-strand mat (fiberglass) along with polyester
resin (figure B) all over the mold. The mat and resin is rolled along the entire surface of the
mold, and then the structural fiberglass cloths are added. Once all of this cures, the gelcoated
deck separates from the deck mold.
The gelcoat has been designed to cure without the presence of air.
Starting the Gelcoat Repair
Materials:
Die grinder and bits
Dust mask and glasses
1,000-grit wet dry sandpaper
1,200-grit wet dry sandpaper
1,500-grit wet dry sandpaper
Blue masking tape
Safety glasses
Dust mask
Gloves
Acetone
Rags
Gelcoat or tint kit
Mixing sticks
Plastic cups
MEKP
Marine wax
Surfacing wax
Yellow spreaders
Sanding blocks
Painter's tape
Cavisil
Buffing compound
Buffer
Buff pads
Wax pads
Terry cloth
Spoke
The first thing you need to do before repairing gelcoat is to tape off the rub rail with blue
masking tape (figure C).
1.
Put on a pair of safety glasses, a dust mask and start the process of grinding out all the
fractured areas of the gelcoat.
2.
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Figure C
Figure D
Once you've found all the cracks and damage to the gelcoat, use a high-speed tool with a
cone-shaped grinding bit on it to remove even more gelcoat (figure D) from the boat so
that you get down into some un-fractured fiberglass. This will give you a solid foundation
to be working on. (The loose material must be ground out).
3.
Feather the edge of the repair area in order to give the new gelcoat a much larger
surface area to bond to.
Tip: If you don't have a high-speed grinding tool available, you can do the repair with
some ordinary materials you'll find in your kitchen or garage. For example, a hand-held
can opener can scratch out any of the fractured gelcoat. Just be sure to come back with
some 80-grit sandpaper to bevel out the edges.
4.
Clean the area by removing all the dust and loose fiberglass from the grinding by using
acetone and a rag (don't ever let acetone touch your skin). Be sure to use a different
section of cloth for each wipe in order to keep it dust free.
Warning: If you don't remove the debris thoroughly, when the new gelcoat is applied, it
may not bond properly.
5.
In the next segment, Greviskis explains the process of mixing the gelcoat and applying it to the
craft.
ALSO IN THIS EPISODE:
Gelcoat Repair: Getting Started
Gelcoat Repair: Mixing and Applying the Gelcoat
DIY Network: Maintenance & Repair http://www.diynetwork.com/diy/cda/artic ... _13718_2...
1 of 3 10/07/2006 4:38 PM
The host of Shipshape
Boating, John Greviskis,
shows you how to repair
and maintain the finish --
also known as gelcoat --
on a fiberglass craft.
Figure A
Figure B
Figure C
Figure D
DIY NETWORK
To print this page, select File then Print from your browser
URL: http://www.diynet.com/diy/bo_maintenanc ... 03,00.html
GELCOAT REPAIR: MIXING AND APPLYING THE GELCOAT
From "Shipshape Boating"
episode DSSB-108 -- More Projects »
Materials:
Die grinder and bits
Dust mask and glasses
1,000-grit wet dry sandpaper
1,200-grit wet dry sandpaper
1,500-grit wet dry sandpaper
Blue masking tape
Safety glasses
Dust mask
Gloves
Acetone
Rags
Gelcoat or tint kit
Mixing sticks
Plastic cups
MEKP
Marine wax
Surfacing wax
Yellow spreaders
Sanding blocks
Painter's tape
Cavisil
Buffing compound
Buffer
Buff pads
Wax pads
Terry cloth
Spoke
Mixing the Gelcoat
Before mixing the gelcoat, you may want to consider some options:
A gelcoat tint kit (figure A) that comes with a base-white product and various tubes of
tint. This is a more difficult way to match the color of your original gelcoat because you
have to test the various tints in with the white base until you come up with the proper
color. Many times you may not get an exact match to the original gelcoat.
You can use the manufactured tubes of gelcoat that are sold for most crafts as an "after"
product, but remember, over time the entire surface color of your boat may change
slightly, and the original product will be the perfect original color.
You can get a company to match the original gelcoat by sending a sample such as a
hatch to a storage area. Many companies will take sample and scan it in to a computer
(figure B), where the computer will match the color. This method will give you an exact
color match. This is the option that host John Greviskis went with for this particular on-air
project.
Before you mix up the new gelcoat, you'll need to add a few items to the mixture:
Add MEKP (Methyl, Ethel, Ketone and Peroxide), which is a type of hardener used for
polyester-based material. You simply add about 1 ounce of the MEKP, which is a ratio of
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Figure E
Figure F
Figure G
After your boat's gelcoat
is repaired and shiny, it's
time to take it out on the
water and have fun!
10 percent MEKP to gelcoat.
You also need some kind of agent inside the gelcoat in order to cut off the outside air
supply. This agent is called a surfacing wax. Use five percent by volume here. (Gelcoat
will never harden, no matter how much hardener you use if left exposed to the outside
air.)
The final touch is to add a thickening agent -- colloidal silica, also known as "Cavasil" --
to the gelcoat to get the right thickness (like thin paste or creamy peanut butter --
figure C).
1. Stir gelcoat mixture until it is smooth.
Outline each repair area with masking tape so you only get the gelcoat to the areas
needed and no drippings.
2.
Add enough material to the repair area so that the height of the new gelcoat is slightly
higher than the height of the surrounding gelcoat (figure D). This way when it cures you
can come back and sand the gelcoat down.
Note: It's best to let the gelcoat cure for at least 24 hours. You want to make sure it's
dry and solidly formed.
3.
Using a rubber sanding block and 320-grit wet/dry sandpaper, wet sand the gelcoat down
trying to stay as close to the new gelcoat (figure E). Sand the area going in several
different directions. Make sure that your keep the paper wet by occasionally dipping it
into a bucket of water. You want to do all the damaged spots like this.
4.
Now, switch out to 500-grit wet/dry sandpaper and wet sand just a little farther out away
from the center of the repair than where you sanded before. This is how you blend this
area to the rest of the boat. At this point you don't want to use block sandpaper. It's
easier to bevel out the edge if you use the regular sandpaper by hand.
5.
Now it's time to progress to a 800-grit wet/dry sandpaper. Again taper out the sanding
just a little bit further. Each time you go up in grit paper your actually sanding out the
scratches that we just cut into the gelcoat with the previous grit paper.
6.
7. The final sandpaper you'll use is 1,200-grit wet/dry. Copy the previous two steps.
The final sanding doesn't involve sandpaper at all. You'll use a variable-speed buffer and
some medium course rubbing compound. You'll need compound that equates to about
2,000-grit (coarse) wet/dry sandpaper.
8.
First, put a dab of the compound on a dry lambs wool buffing wheel (figure F). Smear it
onto the area of the boat, applying it in circular motions. Set the speed on the buffer to
1,500 RPM and go to work. Tilt the wheel so that the top third of the pad is coming in
contact with the boat hull. Rotate any slower and the rubbing compound will not
adequately cut into the gelcoat, and if you rotate any faster and you might wind up
burning through he gelcoat.
9.
Make sure to overlap your strokes.
Safety Alert: Be sure to wear safety goggles and a dust mask when buffing the gelcoat. You may want to consider
wearing a protective suit as well.
Tip: If the buffing wheel becomes clogged with dried gelcoat compound, a great way to clean it is to turn the machine
on, insert a spurring tool (figure G). Insert the tool at a 45-degree angle and turn the buffer on. This removes the
entire dried-up compound.
10.
Waxing the Boat
The only thing left to do is wax, which is used to seal the gelcoat and protect it from oxidizing. It protects the longevity
of the gelcoat and is what keeps it from getting chalky.
Using a quality marine-grade wax, first apply it to the hull sides using a wheel. Use tiny overlapping strokes. Once you
get a side done let it haze over so that it is completely dry and then use a clean terry cloth towel to remove all the
haze.
Note:
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For southern climates, wax the hull every six months and the deck every three months.
For northern climates, wax the hull every 12 months and the deck every six months.
ALSO IN THIS EPISODE:
Gelcoat Repair: Getting Started
Gelcoat Repair: Mixing and Applying the Gelcoat