Painting bare fiberglass boats
BOAT HULL PREPARATION
1. Since the boat may never have been painted, take extra care and time in preparing the bottom before proceeding to the system of choice. Clean surface carefully, start by removing all contaminants and "Mold Release Wax" on the surface as follows.
2. Scrub the surface thoroughly using soap and water and a stiff brush. Flush with fresh water to remove soap residue. Allow surface to dry.
Then proceed with either of the two following options:
Option 1: Apply Fiberglass Surface Prep YMA601 with a maroon, 3M, Scotch-Brite pad and scrub well. Flush with fresh water or wipe off with a clean, wet cloth ensuring that no traces of Fiberglass Surface Prep remain.
Option 2: Dampen cheesecloth with Interlux Fiberglass Solvent Wash 202. Wipe thoroughly to remove all surface contamination and cleaners. Wipe off with a clean, dry rag before liquid dries. Wipe only a few feet at a time.
3. Lightly spray the surface with water to insure all contamination has been removed. If water beads up or separates, wax is still present. Repeat until water no longer beads. At this point all mold release agents, wax and other contaminants should have been removed. Proceed to one of the following No Sand Method, Interprotect Method or Sanding Method.
BARE FIBERGLASS - SANDING SYSTEM
After the surface has been prepared as described above Sand entire surface well with 80-grit sandpaper until flat matte finish is obtained. Remember to change sandpaper frequently. Wipe off sanding residue with Fiberglass Solvent Wash 202. Apply two coats minimum of Interlux antifouling paint.
Whether the boat is new or a few years old "Mold Release Wax" and other contaminants like dirt, grime, dust, oils and even road salt can be present on the bottom of the boat. It is important to properly prepare the bottom of the boat before proceeding.
SYSTEM 1: NO SAND METHOD
Bottom painting bare fiberglass, Polyester
or Vinylester gelcoats or epoxy resin
Note: If you miss the overcoat time between the Fiberglass No Sand
Primer and the antifouling paint you may apply another coat of primer
for up to 72 hours of initial application.
- Follow the Boat Hull Preparation instructions above.
- Using a 1/8 inch foam or 1/4 inch mohair solvent resistant roller,
apply one thin continuous coat of Fiberglass No Sand Primer.
Apply in one direction only without recoating.
- Only one coat of Fiberglass No Sand Primer is required. Antifouling
overcoat times will vary due to wide variations in temperature and
humidity. The only safe method to determine when the Interlux Fiberglass No Sand Primer is "Ready-to-Overcoat" is to check the paint film using
the "Thumb Print" test. If the primer feels tacky and you can leave a
thumb print in the paint film without getting any paint on your thumb,
the Fiberglass No Sand Primer is "Ready-to-Overcoat". Test the paint
film in the area you started applying the primer no later than 30
minutes after starting the application. Continue testing every 15
minutes using the "Thumb Print" test until reaching the "Ready-to-
Overcoat" stage. Immediately, begin to apply the Interlux antifouling
paint once the primer has reached the "Ready-to-Overcoat" stage.
- One coat Fiberglass No Sand Primer applied at the recommended WFT; may not hide the gelcoat completely when applied properly.
- Fiberglass No Sand Primer cannot be used with the
following Interlux antifouling paints: VC17m® Extra,
VC17m, VC Offshore, Baltoplate, Micron® 66™, Ultra™,
Super KL or Micron Optima. Do not use with any water
based or vinyl based antifouling paints.
- Fiberglass No Sand Primer is moisture sensitive. Do not
leave containers open during application. Once project is
complete discard all remaining Fiberglass No Sand Primer.
- Do not apply Fiberglass No Sand Primer if the relative
humidity exceeds 85% or if temperature exceeds 95°F
SYSTEM 2: LOW VOC NO SAND METHOD
Painting bare fiberglass, Polyester,
Vinylester gelcoats or epoxy resin
- Follow the Boat Hull Preparation instructions on page 2.
- Apply one coat of Low VOC Fiberglass No Sand Primer
- Apply two coats of Fiberglass Bottomkote® Aqua or
Should it rain during or immediately after application, the coating
must be allowed to dry for a minimum of 24 hours before
overcoating. If temperature is less than 50°F (10°C) allow a
minimum of 48 hours prior to overcoat.
DRY TIMES FOR LOW VOC FIBERGLASS
NO SAND PRIMER YPA142
SYSTEM 3:HIGH PERFORMANCE NO SAND METHOD
For new or non-blistered hulls
- Prepare the surface as per instructions on page 2 using the
Interlux Fiberglass Surface Prep YMA601 with a maroon, 3M, Scotch-Brite padmaroon, 3M Scotch-
- Apply 1 coat of InterProtect 2000E using a 3/8" solvent resistant
nap roller. Appropriate coverage is 240 sqft/gal.
To determine if the InterProtect 2000E is ready to overcoat,
check the paint film using the "Thumb Print" test. If the
InterProtect feels tacky and you can leave a thumb print in
the paint film with out getting any paint on your thumb, it is
"Ready-to-Overcoat". Test the paint film in the area you started
applying the primer no later than 30 minutes after starting the
application. Continue testing every 15 minutes using the
"Thumb Print" test until reaching the "Ready-to-Overcoat"
stage. Immediately, begin to apply the Interlux antifouling paint.
- Apply 2-3 coats of Interlux antifouling paint.
Up to 2 weeks may be left between coats of InterProtect 2000E but the time between the last coat of InterProtect 2000E/2001E and the first coat of antifouling are much shorter and temperature dependent. The "Thumb Print" test is the
best method to use to determine when to overcoat the
InterProtect 2000E with antifouling paint. If maximum dry
times are exceeded, apply another coat of InterProtect®
2000E/2001E and then be sure to hit the proper overcoating
interval before the application of the antifouling paint.
These overcoat times do not apply to performance or vinyl
antifouling such as VC17m® Extra, VC17m®, VC® Offshore,
Baltoplate and VC® Performance Epoxy.
To apply performance or vinyl antifoulings apply at least one
extra coat of InterProtect&Ireg; 2000E/2001E and allow to dry 24
to 36 hours. Then sand with 80-grit sandpaper. Be careful
to leave at least 10 mils dry film thickness of epoxy after
sanding. Apply the performance or vinyl paint of choice.
SYSTEM 4: INTERPROTECT® BLISTER PREVENTION METHOD
For new or non-blistered hulls
Use this system on new boats or used boats where all antifouling
paint has been removed.
See chart on page 4 for amounts needed.
- Follow boat hull preparation procedures as per instructions
on page 2.
- Sand the gelcoat thoroughly using 80-grit sandpaper.
- Remove the sanding residue by wiping with Fiberglass
Solvent Wash 202.
- Apply 10 mils (4-5 coats) of InterProtect 2000E.
- Apply 2-3 coats of Interlux Antifouling Paint.
|Remember prior to sanding the
hull, thorough dewaxing is very
important. Sanding heats any
remaining wax on the surface,
and then pushes it into the open pores in the gelcoat.
This will keep any antifouling paint or primer you apply
|YPA200 ||No Sand Primer.
||YAV135KIT ||Watertite Epoxy filler.|
|216 ||Special Thinner - To clean previous painted areas.|| || |
|YPA142 ||Low VOC No Sand Primer.||6216 ||Paint Conditioner for Low VOC System.|
|2000E ||Blister prevention system.||2316N ||Reducing solvent - For clean up.|
|YMA601 ||Fiberglass Surface Prep - Pigmented water based
abrasive cleaner for bare fiberglass.
||2333N ||Brushing Reducer - For thinning and clean up.
|202 ||Fiberglass Solvent Wash - To clean bare fiberglass
and remove mold release wax prior to application.||INTERLUX® ANTIFOULING ||Check compatibility.|
HOW MUCH PAINT DO I NEED?
Determining how much paint you will need is fairly simple.
The estimated surface area in the chart below is based on
the average boat size and type so actual square feet can vary.
It is best to actually measure the wetted surface area of the hull.
If it is difficult to do, a close approximation can be made by
multiplying the length overall, times the beam, times 85%
(LOA X Beam X .85 = wetted surface area). Then divide the wetted
surface area by the square foot coverage per gallon, of the product
you are using. The result is the number of gallons needed for 1 coat.
See product cans for per square foot coverage per gallon.
Below is an estimate of the amounts needed.
|BOAT SIZE & TYPE
||BOAT ESTIMATED SURFACE AREA
||FIBERGLASS NO SAND PRIMER 1 COAT
||ANTIFOULING PAINT 2 COATS
|18' Power & Sail
||120 Sq. Feet
||120 Sq. Feet
||120 Sq. Feet
|21' Power & Sail
||150 Sq. Feet
|28' Power & Sail
||240 Sq. Feet
||270 Sq. Feet
||330 Sq. Feet
|36' Cruising Sailboat
||350 Sq. Feet
||370 Sq. Feet
||435 Sq. Feet
||500 Sq. Feet
|53' Cruising Sailboat
||590 Sq. Feet
||650 Sq. Feet
This pdf from Interlux offers more info on painting bare fiberglass boats
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