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Opinions and comments are strictly those of Paul Oman. Others will certainly disagree with at least some
of the things mentioned below.
Readers are encouraged to seek out alternative opinions and viewpoints rather then relying completely
on the information and ideas offered below.
Information/viewpoints are not 'vendor/manufacturer' official recommendations or specifications. Use
this information at your own risk!
TOPIC INDEX
Epoxy paint rollers (and more)
Barrier Coatings for fiberglass, steel, and cement
Boat Blisters
Brightwork
Epoxies - How to evaluate/compare
Epoxy - How Much Epoxy do I Need?
Epoxy vs. Fiberglass (polyester) Resin
Paint and Painting - Latex Paint
Penetrating Epoxies
Rotting Wood and Ethylene Glycol
Underwater Hull Surface Area Calculations
Epoxy Coating Your Boat Hull
Which Brand of Epoxy Should You Use?
Polyester vs. Epoxy Resin
Epoxy Pumps
Repairing hairline cracks in old fiberglass hulls
No Sand Epoxy Surfaces
Flexible non-skid deck surface
x
Roller Recommendations
Users recommend using a 3/16 inch nap roller specifically labeled for use with epoxies (regular rollers are
3/8 inch). An alternative would be a ‘lintless' roller. Foam rollers work also, but the foam may begin to break
off before job is complete. Regular ‘bulk' rollers will work too, but will leave roller fibers/lint on the surface
for the first 30 square feet or so.
We now sell short nap epoxy rollers.
Check out those painting 'pads' - a short nap on a foam block or plastic holder. Our tests seem to show they work
better than bushes or roller!
notes on rolling epoxies on smooth surfaces (such as hulls) click
here
Barrier Coatings for Fiberglass, Steel, and Cement Hulls
Essentially a barrier coat is simply a layer of epoxy, which is highly non-porous, applied over a rather porous
polyester resin fiberglass hull. The regular fiberglass hulls can selectively draw in water and create blisters.
The epoxy barrier coat seals the hull.
Despite what you may have read, barrier coat technology is not rocket science. It boils down applying a sealing
coat of epoxy to your hull and basically any epoxy will do the job, in fact, from what I have observed many paint/resin
companies seem to have brought obsolete and junky epoxies back to life as barrier coatings.
Nice Thing To Have In Your Barrier Coating:
1) pigment - so you can see where you've painted it and get an idea how evenly and uniformly you have been applying
it.
2) thickening and gelling agents. These two are not quite the same thing. Hopefully your barrier coat is thick
enough that you do not have to apply coat after coat to get a reasonably thick coat. How thick? No set answers,
but figure about 10 mils which would normally be about 160 square feet per gallon of a SOLVENT FREE coating. That
might equal 3 or 4 coats of ordinary varnish or interior wall paint. Thicker is better as it provides a ‘wider'
barrier to moisture migration. Barrier coat products range from 3-4 mil dry coating thickness per coat to 40 -
70 mil, Kevlar (tm) microfiber reinforced, single coat epoxy systems. These thicker coats are often used to seal
and protect cement hulls and 'rust proof' steel hulls.
Gelling agents keep the epoxy from sagging after application on a vertical surface. The opposite of gelling is
(sort of) the term self leveling. Ordinary epoxies used for boat building, repairing, etc. do not have gelling
agents in them. You can use them for barrier coating but watch for sags and expect the epoxy to flow so that the
coating near the water line will be thinner than the coating that collects down by the keel. Is this a big deal?
Probably not. More info: Click here
Which epoxy to use? click here
Boat Blisters
Most folks make a big deal over fiberglass hull blisters. They will not sink or boat and are not worth the worry
so many people give them. Consider them like teenage pimples or zits. Pop them, wash them, and medicate them (patch
them) and get on with your life. If you insist upon making a big deal about them, you can always find someone willing
to agree with you and charge you lots of money for whatever degree of ‘overkill' you are willing to pay them for.
More info: Click here
Brightwork
If your boat is like mine was, there are at least several wood surfaces that require a varnish or polyurethane
clearcoat. When living in the Gulf Coast I learned these finishes do not last long. Here is the technique we developed
using epoxy and varnish (or polyurethane). First, seal the wood with several coats of epoxy until you have a glassy
hard finish. Lightly sand the epoxy and topcoat with one or more coats of varnish or clear polyurethane. This will
provide the UV protection to the epoxy, will the epoxy protects and seals the wood. Our Floro Polymer would also
do this.
One other trick with the varnish. You can thicken it with fumed silica (often know by the Brand name Cabosil (tm))
-- so that it goes on twice as thick — two coats for the price of one!
Epoxies - How to Evaluate/Compare
Like whiskey, there are good and bad epoxies, potent epoxies and watered down epoxies. There are cheap/trashy moonshine
epoxies and performance blends. You can probably build your boat with any of them and be alright. The degree of
quality (or ease of use) is a very personal thing.....
Here are a few things you can look at to get a clue about the quality or user friendliness of your epoxy.
Blush/Amine blush - Blush is a waxy layer (sometimes visible, sometimes not) that develops on the surface of many
epoxies as they cure. It is a reaction of the curing (hardener) agent with moisture in the air. It must be washed
off or additional layers of epoxy or paint will not bond well to it. The very best epoxies do not blush and are
so indifferent to moisture that they can literally be applied underwater.
Nonyl Phenol - This is an inexpensive chemical added in small amounts to either side of a two part epoxy to produce
easy mix ratios. When added in large amounts, say more than 15%, it is a way to ‘water down the epoxy' and get
the cost down. Ask for the MSDS sheet of any epoxy you purchase and check for nonyl phenol. Nonyl is not necessarily
a completely bad thing, but a nonyl rich epoxy should not be as expensive as a non nonyl filled epoxy.
Induction Time - If you have to mix your epoxy and let it sit for some amount of time (called induction time) before
you can begin using it, you are probably dealing with a ‘cheap' epoxy.
Epoxy Crystallization - If your epoxy (part A or part B) tends to crystalize in the can over time (warming will
remelt the crystalized mass) you are probably dealing with a specialized epoxy or a ‘cheap' resin/hardener. There
are resins and curing (hardening) agents that will not crystalize. This might not be a purely price issue, but
it certainly is a ‘user friendly' issue.
MSDS - The Material Data Safety Sheet - all vendors and manufacturers are required to have these safety sheets
for each of their products. I am always surprised how difficult it is to get an MSDS from almost every Epoxy vendor.
If they will not offer up a MSDS for their base AND cure/hardener without a lot of hassle, by from a vendor that
will. MSDS information should also be available at the local marine store for all the products they carry.
Epoxy - How Much Epoxy Do I Need?
1 gallon of resin wets out:
material sq ft
.75 oz mat 64 square feet
1.5 oz mat 32 square feet
6 oz cloth 90 square feet *******
10 oz cloth 60
18 0z woven roving 40
24 oz woven roving 32
2415 bi-ply 16
******** This is a very common weight. Figure 50 square feet of coverage with 2 top coats of additional epoxy to
completely bury the cloth weave (i.e. three total coats of epoxy).
Paint and Painting - Latex
We have discovered how great exterior latex paint is on boat surfaces above the waterline and on epoxy surfaces.
A top quality semi-gloss, exterior house latex (like that used for trim or shutters at $30 per gallon) is easier
to apply, easier to clean up, keeps it shine much longer and is more fade resistant than any marine enamel I have
ever used. It is also less brittle and less subject to cracking. Being slightly porous, it resists blistering much
more than enamels. It all makes sense. Paint companies have performed a lot more R&D in the competitive, huge,
house paint market than in the much smaller marine paint niche. Another plus - with custom blending, you can get
any color you want.
Expert article on Latex on boats: click here
A second tip. Do not every use pure white paint on your boat. It shows too much dirt, etc. Instead use an off-white,
something with a slight gray or blue tint. You will find that while your off-white may look gray in the can or
at your home, when on your boat, and surrounded by other boats, it will still look pure white and much whiter and
brighter than any of the other ‘white' boats around it.
Another real plus. If you are like me and work on the boat during the weekends, this can save you an entire work
session. Latex paint can be applied to just applied, still wet, epoxy without waiting for the epoxy to even begin
to cure. This work, at least, with the non-blushing marine epoxy I use. I cannot say for certain if it works with
other, more common, name brand epoxies which do suffer from amine blush. It is nice to fill an dent or gouge with
epoxy and then immediately carefully brush or dab on the matching hull/deck latex paint instead of waiting a week
to repaint the repair.
For the finest above the waterline hull coating (white only) I would recommend our LPU
100 - a two-part linear polyester urethane (compare to Awlgrip) over a primed surface. For more information about
epoxies and urethanes see our Chemistry of
Epoxies/Urethanes page. For more info about LPU 100 - CLICK
HERE.We now also sell LPU 100 in clear. One idea is to paint the hull in whatever
color enamel or latex and then topcoat with the clear and durable LPU 100 clear. The LPU 100 will go on fine, but
I have no data or feedback as to how long such a system would last.
Penetrating Epoxies
This has become such a critical topic that a dedicated web page has been assigned to Penetrating Epoxies.
Click here to link to: www.epoxyproducts.com/penetrating4u.html
Epoxy vs. Fiberglass (polyester) Resin
Standard fiberglass resin (polyester resin with styrene) is used to make fiberglass boats. It is inexpensive, smelly,
dissolves foam, sticks will to itself, tends to be slightly porous (can absorb water and form blisters), and does
not stick well to wood, metal or other surfaces.
Epoxies are as messy as polyester resins to work with and cost a lot more. However, they do not smell as badly,
generally will not dissolve foam, sticks great to nearly everything (except ‘milk carton' or ‘gas can' plastics),
and are much less porous than polyester resins.
For fiberglass on fiberglass repairs, you might use polyester resins, but even in those cases, and certainly for
all other situations (especially when wood is involved), use epoxy resins.
Note that all epoxies are not created equal, but even the worst of the epoxies is probably more than adequate for
about any task you might put them too.
Rotting Wood and Ethylene Glycol
I don't know why the use of Ethylene Glycol (ie. regular automotive Antifreeze) to kill and treat the fungus that
causes wood rot causes such strong reactions in many people. Obviously the best solution to rot is to cut it out
completely and replace the damaged area. If you cannot or will not do that (such as on the top surface of an otherwise
good wooden dock piling), then liberal use of antifreeze on the rotting wood will kill the fungus. The antifreeze
will evaporate, leaving begin just a slight residue. The rot fungus will eventually return - the glycol have evaporated
away. The wood is still damaged and rotted, but at least you've checked the rotting for the moment. If somehow
patched or coated/repaired the rotting will probably not continue hidden under the patch.
Third party article: click here
I cannot speak for other epoxy brands, but the non-blushing brand of epoxy I use does bond to anti-freeze coated
surfaces. I have even mixed antifreeze into the liquid epoxy and it cured just fine, although I can see no reason
for every doing this.
Underwater Surface Areas
General Rules of Thumb (Based upon information for Interlux Boat Painting Guide)
boat size wetting surface area
18 ft day sailer = 120 squ feet
21 trailerable = 160 sf
28 racer/cruiser = 250 sf
31 racer/cruiser = 270 sf
36 cruiser = 330 sf
41 cruiser = 435 sf
53 cruiser = 590 sf
motor boats
18 runabout = 120 square feet
21 runabout = 150 sf
28 cruiser = 240 sf
32 sportfish = 300 sf
36 cruiser = 350 sf
42 cruiser = 500 sf
53 cruiser = 650 sf
formula:
LOA times beam times 0.85 =wetted surface area.
Epoxy coating your boat hull
Disclaimer: these are only theoretical suggestions based upon my knowledge of certain epoxy coatings. They are
not vendor/manufacturer/supplier recommendations or approved techniques. Decision to follow or not follow these
suggestions, rests completely with the purchaser or end user. There is no warranty, refunds, liability etc. implied
or suggested regarding the selection, preparation, application, or results involving these products or suggestions
mentioned here.
Wood Hulls
I would always think twice about applying an epoxy skin or coating over a wooden boat and would do so only if I
felt I had run out of options for maintaining the original wood surface. I would consider only epoxy coating the
hull below the water line.
Inside the Hull - I would use 3 coats of our coal tar epoxy, with the first coat thinned 10%. I would only use
if I had exposed (uncoated) wood to cover. The thinning would help penetration of the first coat. Coal Tar epoxies
are relatively flexible, but do not like being painted over, hence the reason for internal application.
Outside the Hull - One or two coats of thin Low V epoxy (maybe even thinned 10% for better penetration) and then
1 coat (or 2) coats of our Hi Flex epoxy. If budget or time constraints apply, the single (or double) coat of Hi
Flex would work without the "penetrating Low V" epoxy.
For the finest above the waterline hull coating (white only) I would recommend our LPU
100 - a two-part linear polyester urethane (compare to Awlgrip) over a primed surface (we also have a less expensive
white 2-part acrylic urethane now). For more information about epoxies and urethanes see our Chemistry
of Epoxies/Urethanes page. For more info about LPU 100 - CLICK
HERE.We now also sell LPU 100 in clear. One idea is to paint the hull in whatever
color enamel or latex and then topcoat with the clear and durable LPU 100 clear. The LPU 100 will go on fine, but
I have no data or feedback as to how long such a system would last.
Fiberglass Hulls
Inside or out - Our fiber reinforced FC 2100, or the fiberless NSP 120 epoxy is the choice for both an exterior
barrier coat and bilge coating. Both use cycloaliphatic curing agents and are non-hazmat to ship. Second choice
would be our Hi Flex 3 epoxy.
For the finest above the waterline hull coating (white only) I would recommend
our LPU 100 - a two-part linear polyester urethane (compare to Awlgrip) over a primed surface (we also have a less
expensive white 2-part acrylic urethane now). For more information about epoxies and urethanes see our Chemistry of Epoxies/Urethanes
page. For more info about LPU 100 - CLICK HERE. We now also sell LPU 100 in clear. One idea is to paint the hull in whatever color enamel or
latex and then topcoat with the clear and durable LPU 100 clear. The LPU 100 will go on fine, but I have no data
or feedback as to how long such a system would last.
Steel Hulls
Inside or Out
A standard 3 coat industrial system (zinc primer, epoxy, poly topcoat) - click
here
OR
2 coats of CORRO COAT FC 2100
Water tolerance before curing allowed the hull to be refloated immediately after the final FC 2100 application.
Completely free of volatile solvents – no smell or air pollution in the drydock during spraying.
Ability to apply at 10 – 80+ mils with no sagging.
Compatible with residues of all existing coating types.
For the finest above the waterline hull coating (white only) I would recommend
our LPU 100 - a two-part linear polyester urethane (compare to Awlgrip) over a primed surface. For more information
about epoxies and urethanes see our Chemistry
of Epoxies/Urethanes page. For more info about LPU 100 - CLICK
HERE. We now also sell LPU 100 in clear. One idea is to paint the hull in whatever
color enamel or latex and then topcoat with the clear and durable LPU 100 clear. The LPU 100 will go on fine, but
I have no data or feedback as to how long such a system would last.
Aluminum Hulls
I am not yet comfortable with aluminum hulls. Aluminum can be the most difficult metal to coat and I frankly do
not know what to suggest here.
For the finest above the waterline hull coating (white only) I would recommend
our LPU 100 - a two-part linear polyester urethane (compare to Awlgrip) over a primed surface. For more information
about epoxies and urethanes see our Chemistry
of Epoxies/Urethanes page. For more info about LPU 100 - CLICK
HERE.
Which Vendor's Epoxy/Epoxies Should You Use?
We now have an entire site on this - Click Here
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