Page 18. MAINE COASTAL NEWS November 2008
Epoxy vs. Polyester When Working with Fiberglass
By: Tom Pawlak, West System number of ways. Polyester resin is still used excellent moisture barrier when used as a resin and epoxy are industrial chemicals and
Technical Staff Member to build most production fiberglass boats coating and it adheres to many different should be used with care.
Thirty-five years ago, many boats were because it’s the lowest cost option for new substrates including wood, metals, cured Epoxy is stronger
built and repaired primarily with chopped construction when combined with fiberglass polyester laminates, vinyl ester laminates Tests comparing WEST SYSTEM ep-
strand fiberglass and polyester resin. The reinforcements. Due to polyester resin’s and epoxy laminates. It binds extremely well oxy and DCPD (dicyclopentadiene) blend
repairs were usually successful if done by an brittleness, randomly-oriented chopped to graphite fibers, so it’s often used for polyester resin on well-cured DCPD blend
experienced professional. strand fiberglass is typically used between making high-strength composites. polyester/fiberglass laminate show each
Chopped strand fiberglass isn’t very layers of woven or stitched fabrics to effec- Epoxy is more versatile product’s repair effectiveness. Made of
strong when compared to woven and tively transfer loads between structural fi- Polyester resin manufacturers recom- multiple layers of stitched 2315 triaxial fiber-
stitched strand fabrics. However, hulls made berglass plies. Without the chopped strand mend their products be cured in tempera- glass with mat, this laminate represents a
with chopped strand fiberglass and polyes- fiberglass, micro cracks can develop over tures above 60º F. Repair yards often have to typical side of a cored-composite, high-qual-
ter resin are built thick and are stiff and heavy time in the resin between structural fiber- work in much cooler conditions. Extra MEKP ity fiberglass boat. A precise 12:1 bevel (the
as a result. To repair these laminates, the glass layers. (methyl ethyl keytone peroxide) catalyst can minimum angle recommended for repaired,
technician would grind away the damage and Polyester resin is normally air-inhibited, be added to assist the cure in cool tempera- cured composites) was ground along one
sand a gradual taper around the perimeter which means it typically remains uncured tures, but cured physical properties suffer edge of the laminates. The repaired area was
before laminating with new fiberglass and (sticky or tacky) on the surface when ex- because of it. Shelf life of general-purpose then final sanded with 80-grit sandpaper.
polyester resin. posed to air. To cure reliably, general-pur- polyester resin is six months to a year from Different repair resins were used to ap-
The chemistry of polyester resin has pose polyester resin needs to be applied in at the time it is manufactured. ply multiple layers of fiberglass (the largest
changed over the years. Today, many hulls least 15 to 25 mils (.015" to .025") thick. WEST SYSTEM epoxy is routinely used ply first, each ply separately laid and wet out
are built thinner and more flexible so they’re Partially because it will not cure thoroughly to repair structural damage to fiberglass with resin) to gradually fill the beveled sec-
more difficult to repair effectively. The resin in thin films, it’s ineffective as an adhesive boats over a wide temperature range. Hard- tions to achieve the original thickness. The
cross-links more completely during cure, re- and only marginally effective for repairing eners are available for curing it from 40º F on repair was allowed to cure for a few days and
sulting in fewer available sites for primary well-cured polyester/fiberglass laminates. up. The shelf life of WEST SYSTEM epoxy then the repair zone was sanded perfectly
bonds. A few boatbuilders using new poly- Polyester resin is not recommended for fixing is several years. smooth. G-10 fiberglass laminate tabs were
ester formulations are now glass tabbing in vinyl ester or epoxy laminates. Epoxy gives off less fumes added to both ends of the tensile specimens,
their bulkheads with epoxy instead of poly- Epoxy is very effective as both an adhe- Fumes from polyester resin are strong providing a grip area for the test machine.
ester resin. Because epoxies form superior sive and a laminating resin for wetting out and flammable while the fumes from WEST They were allowed to cure for two weeks
secondary bonds, they readily adhere to structural fabrics and a coating. It resists SYSTEM epoxy are slight in comparison and
Continued on Page 26.
properly prepared, cured polyester. micro-cracking better than polyester resin not a fire hazard. However, both polyester
Comparing epoxy and polyester and has excellent thin film characteristics.
Polyester resin and epoxy differ in a WEST SYSTEM epoxy offers 3.5% to 4.5%
tensile elongation at failure compared to 1%
to 2% for typical polyester resin. It’s an
The Boat School to Offer
S
Composite Technician Course
NOWE
The 3-day training course for the Workforce Program Director at 207-623-
American Composites Manufacturers 7974
ADDRESSES...
Association (ACMA) Certified Composites Participants must have at least a year of
Technician credential and testing will be experience with composites in the industry
offered by The Boat School – Husson at and will sit for their ACMA certification test
Continued from Page 15.
their Eastport campus Thursday, January at the end of the 3 day course.
3-axis CNC machining Midcoast Fishermen’s Association; Sally
23rd through Sunday January 25th, 2009. “Overall, the Boat School’s ACMA
Marine mill trim
McGee of Environment Defense Fund;and
The deadline for registration is CCT program is designed to elevate
Teak & mahogany
Dr. Daniel Holland, Research Scientist in
December 15, 2008. The program is limited to standards in the industry, enhance
Resource Economics at the Gulf of Maine
Transom name boards
30 participants. individual performance, and recognize
Research Institute
The 3-day course is $ 450. These those who demonstrate a fundamental level
Custom teak handrails
“We all share the goal of giving our fish
Seminars Have Been Approved by Maine’s of knowledge in a specific specialization,”
Cabinet doors & drawers stocks the best possible opportunity to re-
North Star Alliance Initiative for 60% says Boat School administrator John Miller.
Table & counter tops
cover, for without viable, sustainable popu-
Funding Assistance for those that qualify. In order to make the training more affordable
Corian
lations, there would be no fishery at all. But
Maine’s North Star Alliance Initiative is for participants we work with the local Inns
at the same time, we must ensure that while
Hardwood
made possible through funding received and B&B’s as well as local restaurants to
that rebuilding is taking place, we do not
from the U.S. Department of Labor provide discounted rooms and meals for
Meganite
inadvertently bankrupt an industry that has
Workforce Innovation in Regional those attending the CCT training here at The
Swim platforms played such a vital role in our state’s
Economic Initiative. For information on Boat School – Husson.
Teak or King Starboard
economy and heritage for centuries.”
funding you can contact Ginny Carroll, “As a Certified ACMA Composites
Experienced cabinetmakers
Technician, you are a recognized expert
& marine varnishers
among your colleagues and
Maine Coastal News
throughout the industry,”
says Dean Pike, The Boat
contact Gardner Pickering
is online! School’s ACMA certified
gardner@hewesco.com
composites teacher.
Blue Hill, Maine
Check it out at:
“Certified Composite
207-374-2275
Technicians are becoming
www.hewesco.com mainescoast.com
more valuable industry-
wide as the industry
becomes increasingly
competitive and employers
seek qualified individuals,
“says Pike.
The Boat School-
Husson offered this same
120 program this past winter
and attracted participants
from all over Maine. Every
member of the winter 2008
ACMA CCT training at The
Boat School passed their
exam with flying colors.
If you would like to
register, or for more
information, contact The
Boat School – Husson
Bath Industrial Sales
administrator John Miller at
56 New Meadows Rd.
207-853-2518, or e-mail him
West Bath, ME 04530
at jmiller@boatschool
(207) 442-9754
www.bistools.com
husson.net
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