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I was stumbling around the internet and ran into this article (lecture translation) from Terry Alsberg talking about building the Santa Cruz Express 27. There are some interesting comparisons between different fiberglass types and different resins.
Even though our boats were built with vinylester... i found this pretty informative.
http://express27.org/articles/terrya
So, pleez don't take what I say here as (attempted) squeezing of Mr Terry Alsberg.
His talk was given 28 years ago, and is much more tech than what I have mind for.
This was a time when vinylester began use as a laminating resin. Terry says,
Vinylester is a "vinyl modified epoxy" (Ebb always assumed that it was an epoxy modified
polyester!) However, Terry says that they were using, instead of vinylester, an "acrylic
modified epoxy". I'm chemical illiterate, except for xperiences I've had with certain resins.
'Acrylic modified epoxy' is a vinylester resin, it is a polyester blend, NOT in any way epoxy.
The distinction between epoxy and polyester is very important.
The 'peel-resistant-strength' of glass laminations made with epoxy is 'five times' that of
polyester. This is as Terry quotes a US Navy 'boil' test result during his presentation.
I'll take that as an average, as there are many forms of glass fabrics, and other materials
like Kevlar and carbon fiber. All these fibers are very smooth, non porous, unlikely
filaments to be glued by any resin. I have found (usually by mistake) that it is very easy
to take a wood chisel and delaminate A-338's original polyester composite - and almost as
easy to peel epoxy lay-ups. Resin does not get absorbed by these fabrics, no matter how
they are constructed - most we can expect is that they are surrounded or encapsulated:
mat, S-glass, X-mat, roving, woven or knitted single fabrics. The chisel 'follows' the
impregnated fabric which has 'less' resin, less resistance. Matt gets most amalgamated.
BUT the chisel may also 'follow' a cold joint, where tabbing, eg, was added after cure.
Shift from shear resistance to another attribute of epoxy. Terry (probably referring to a
slide in his illustrated talk) says US Navy tests have confirmed that the 'strength retention'
of a "modified epoxy boat will be at 93.3% of its original strength after aging, and polyester
dropped to 41.9% of its strength, and this is why some hulls go soft after a while, they
don't hold headstay tension anymore. {This is scary viz Ariel/Commander polyester.}
"The reason why they oil-can more going through water is because as the resin ages, it's
lower in strength. Another thing that happens as the resin ages, it tends to be a little more
brittle and so it cracks and you can see little microscopic cracks through it. Those little
microscopic cracks also mean more oil-canning and less headstay tension, less shroud
tension, all those sorts of things...." 'Oil-can' aging can be the result of poor engineering.
Or the result of using epoxy specs for boats using polyester blend resin composite.
Polyester resin oil-canning will age crack. Oil-canning epoxy resin will not crack, just flex.
If they built Espresso 27s with 'acrylic modified epoxy', then all Terry's brouhaha is BS!
Years ago, tried to find info on the time aging (rather than work aging) of early polyester.
Found a gov report of Navy tests on some maturing barges they had (WWII,50s,60s?)
-- they seemed unchanged, ageless.
Terry quotes Navy tests, comparing polyester and epoxy, from a time later than the 60s.
We know that epoxy gets eaten by UV - unless protected, it will rapidly decompose. But
polyester from the 60s?....SO FAR, it's only the gelcoat we ever hear about!
OK, so Terry isn't talking about Pearson Ariel/Commander isophthalic polyester of two
decades before, is he? Really, he is probably referring to the blister-prone orthophthalic
hulls of the mid '70s. He's talking in 1987. And he's talking about engineered boats.
And comparing with his Carl Schumacher, N.A. designed Express 27. "of course we hope
that the boats will last at least 25 years.* They were engineered and designed to do so."
Hope if or when LittleGull takes a glancing blow from the butt of a log 200 miles offshore,
that the peel resistance of my 50 year old sweetie.... will be as good as new!
'Modern engineered resins' and the boats made from them - along with 'oriented strand
S-glass' - versus Pearson's oriented strand woven roving and lots of scramble strand matt
....coupled with non-compromised, pre 1973 oil embargo, non modified polyester laminated
by farmers from the Azores...(more than 6degrees of separation there!)
The Pearson cousins mast have talked about it, never recording what was said - but what
was the expected life of our Ariel and Commander? Were they 'engineered and designed
to last 25 years' ??
The wish-I-was-epoxy sloops of the 80s have probably fallen apart*. But our indestructable
little racer-cruisers of the 60s, with authentic polyester and plain glass, keep going on,
hopefully on-going. LittleGull's Biological age is way younger than her Chronological!
Realize Terry's talk is kept posted to celebrate the Express 27's designer's and builder's
genius and expertise. Our proto-engineered A/C hulls are now twice the age of the
projected life of Express 27, now 28 years or so since first produced. Are they still around?
Or have they shattered like an engineered sugar cube? Bet these boats were trouble.*
When I sit or walk close to the hull of LittleGull...... what is that tiny tinkling I hear....?
(the crack of doom)
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*The Express 27 is a viable modern-day racing class association sailing machine.
Conceived as a legs over the rail sport boat - with a pleasant sit-down interior
with just '150# of furniture'. One was driven to Hawaii, and while logging 1100
miles, averaged 16knots in a four day run. Only similarity with a Pearson A/C
is a ballast/ displacement ratio of nearly 50%, a straight sheer, 8' beam and a
balsa core deck. 117 built in SantaCruz, most race on SanFranciscoBay. Sail
mark is a circle with a line thru it.... Obviously they haven't fallen apart, yet.
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OK, so you really want to know more about polyester problems? Here's a no-blister-
barred take, by whom else: Pascoe! He shows you 'How cheap can we make yer boat!'
The Wonderful World of Hull Blistering And Other Interesting Scams
google: Boat Hull Blisters: Blister Again? Yacht Surveyor Online
www.yachtsurvey.com/moreonblisters.html.htm
Really do have great respect for Terry Alsberg's expertise. Building the Express 27 using
vacuum-bag tecniques with vinylester is a feat to be celebrated. Of course, "acrylic
modified epoxy" is a deliberately misleading phrase for vinylester, however much it is
tweeked toward the strength expected from a boat made with 'pure' epoxy compounds.
Polyester resins have as a main ingredient (averaging 40%) a pungent 'liquid hydrocarbon'
vinyl-benzene called styrene. Volatile styrene is blended with polyester liquids to control
viscosity. Vinylester chemically reacts acrylic acids with epoxy monomer bisphenyl A**.
But acrylic acid reacted with epoxy oxirane groups no longer remains an epoxy, and the
resulting mixture is 'finished' with styrene 'as a polyester'. It is polyester with BPA in it.
What percentage of a resin product's epoxy content would chemically allow it to be called
'epoxy', don't know. Assume the DGEBPA oxirane (bispheynol A**) part is well under 60%
if styrene in the mix is around 40%. But more importantly, vinylester is catalyzed with MEKP
(methyl ethyl ketone peroxide) to cure. That makes it polyester, NOT epoxy. Have to say,
it's rather disingenuous to call what is obviously polyester: an epoxy. Even if the US Navy
pronounces a boiling test on a vinylester composite to be near the strength of boiled epoxy.
Vinylester has obviously proven itself to be a fine plastic for the Express27. Using vinylester,
instead of epoxy, even with all the set-up expense, has kept the Express27 affordable.
Sailboats, regularly raced, take a lot of punishment. That voyage to Hawaii (and back?).....
be interesting to find out the 'aging' results, if the boat had then been surveyed?
However, modern epoxy has proven itself to be a far safer* plastic for regular DIY use.
Polyester's main highly volatile ingredient styrene is carcinogenic, MEKP toxic. Using this
stuff requires expensive breathing gear, a high degree of technical expertise in keeping
the workplace safe and the vacuum-bagging ballet totally flawless.
Why deal with that to save a buck?
Resin and fabric projects in and around the Ariel and Commander, choosing epoxy is the
only way to go. Modern laminating epoxy is a wonderful non-proprietary, almost* safe
brew any practical sailor can learn to use. It's expensive, not flawless, but more reliable
and satisfying to use. If sensitized, rashes from epoxy can easily be avoided. 100% solids,
intelligently formulated. low VOC, non-flamable, 2-part epoxy* is, after you get the beat,
almost as fun as varnishing;)....(*epoxy is NOT safe without proper safety precautions.)
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*NOT WetsSystem epoxy sold by WetsMarine.. Their 105 resins contain "vapors"...
flammable solvents, formaldehyde, and can amine blush. Used as a sealer, blush causes
subsequent coatings or laminations not to adhere, to soften, or not cure. If you aren't a
factory and have to break for lunch on a project without the weave filled completely
let's say... would you want to come back and attempt to scrub out amine grease from
the rough surface with soap and water, to continue laminating? The competition does
it better. Without dangerous volatiles you can work with 100% solids epoxy inside the
boat. It's an insult to sell cheaply made amine blush epoxy to DIYs. IMCO
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**Epoxy's bisphenolA is a Medusa-like polymer that has transfixed regulating agencies
into loving it. The CDC's Biomonitoring Summary says, "Finding measurable amounts
of bisphenolA in urine does not imply that the levels of bisphenolA cause an
adverse health effect." This is nasty death-wish doublespeak, unless CDC speaks
for God, OR the too-big-to-be-regulated unethical chemical companies... Right: Both!
BPA is a clear thick honey-like liquid, part A, into which we mix part B, which
itself is a broth of amine based 'reactive dilutents', that lower the viscosity of part A,
at the same time kicking it into polymerization reacton that gets the mix to harden. It's
used to make polycarbonate - line waterpipes - thermal paper sales receipts. Epoxy
seals the inside of every metal can, every can leaches bisphenolA into its contents.
91% of ALL Canadians between the ages of SIX and 79 have measurable
levels of BPA in their urine. Terrorists couldn't dream of better poisoning
results than that!! That's only what's getting out of the body! It's 93% in the US.
In 2010 Canada declared it a toxic substance (an endocrine disruptor) that mimics the
hormone estrogen. It does not naturally occur in the environment. Human body can't
tell it from its own stuff. Linked to 'heart & prostate disease, breast cancer, fertility
issues and developmental problems (autism) in children.' {Probably old guys, too!}
These resins are 'for profit' chemicals, including 'safer' to use epoxy. Protect yourself.
At the end of 2014, USFDA's 'own experts have found no information to change their
previous safety assessment of BPA in food packaging at this time'. Protect yourself!
'SAFE TO EAT. If a problem occurs, we have a healthy pharmaceutical industry
happy to provide you a slew of palliatives to ease your pain.' At extortionate prices.
Instead of going all out to develop a safer BPA, they continue to produce
millions of tons of this toxic pollutant every year, NON STOP! Perfectly OK
for it to be in our bodies...because everybody has it in their body!!
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Despite what the published pundits say, polyester has no place in the refurbishment of
an Ariel or Commander. Polyester laminating resin is a lousy mechanical glue. If you
cold-joint repair a hole in the hull with it, you are asking for trouble. Also a dangerous
explosive. Its short open time and extra wax coat makes it a real PITA to work with.
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:cool:Get the Orthotic & Prosthetic point of view!!
What Resin Am I Using? Let the Truth Be Known - May 2013
http://www.oandp.com/articles/2013-05_11.asp
ebb, breath! Breath! whew.
all I know is that I have been very happy with Epoxy Products standard non-blush 2-part epoxy. and at nearly half the cost of WestSystem it's a no-brainer.