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Old 11-04-2008, 02:10   #1
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Composite boat-building materials & techniques

I think that epoxy vs. vinylester, balsa vs. foam, and other similar questions deserves its own thread, so I'm starting one. Also, I'm hoping posters will add all kinds of tips on techniques, suppliers, etc.
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Old 11-04-2008, 02:21   #2
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Vinylester vs. Epoxy, round 11 zillion and five, or maybe six?

From, Zoltek: Industry News :Carbon Fiber Manufacturer/Companies, Aerospace Composites, Carbon Fiber Uses and Applications, Carbon Fiber and Alternative Energy, Investing in Wind Power, Carbon Fiber, Alternative Energy

"For its more cost-sensitive J/145, the company used a carbon fiber product specially developed by Toray Carbon Fibers America (Flower Mound, Texas) to be compatible with vinyl ester resin. The use of vinyl ester brought the cost of the final laminate down vs. epoxy while reportedly maintaining 95 to 98 percent of the overall properties"

The problem with a generic question / answer is that there is no hard and fast answer. You can't build with a non-specific resin. You must build with an actually existing resin, and when you do, you can get actual strength figures for that product.

In another thread, I posted links to specifications for two vinylesters. Fastcat 435 posted the specs for the epoxy he uses. The tensile strengths in psi (pounds per square inch,) were very similar for one vinylester (from Reichhold,) and Fastcat's epoxy. The other vinylester (from AOC) was 17.6% stronger. My examples are for fire-resistant resins, and fastcat's epoxy is not.

When I look at theoretical figures for epoxy resins, they are always quite a bit higher than those for epoxy resins which are in a actual use in boat building. From this I am inclined to suppose that there is some problem with the strongest epoxies that makes them unsuitable for boat-building.
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Old 11-04-2008, 11:55   #3
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Hetron vinylester resins

Ashland Composite Polymers - EPOXY VINYL ESTER RESINCOMPOSITES

It turns out that Ashland's Hetron vinylester resins are also a lot stronger than Fastcat's epoxy-His epoxy has a tensile strength of 70 to 80 MPa, whereas Hetron 92FR fire resistant resin has a tensile strength of 119MPa. Hetron 92FR has a class one flame resistance with no antimony compounds added. Hetron vinylesters can have a strength of up to 130 MPa, if fire resistance is not a requirement.
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Old 11-04-2008, 12:52   #4
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Link to a page comparing some different vinylesters

http://www.aoc-resins.com/images/upl...007VEGuide.pdf
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Old 11-04-2008, 22:47   #5
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Does an epoxy vinyl ester have the same toxicity of epoxy and the problems of styrene?
Robert
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Old 12-04-2008, 01:54   #6
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Side effects of resins

Quote:
Originally Posted by Robertcateran View Post
Does an epoxy vinyl ester have the same toxicity of epoxy and the problems of styrene?
Robert
Vinylester has styrene in it, but the new cross linked styrenes cross link the styrenes so that they don't escape. They also have quite a bit less styrene than they used to-maybe 40% less. If you are infusing resin, it is only when making secondary bonds such as bulkheads that you might be exposed to styrene. I'd suggest wearing an industrial breathing mask with an 'organic vapor' cartridge, and plastic gloves if doing hand laminating with any resin, or if spraying paint or resin.

I have read that about half of those who work with epoxy will end up with allergies to it, some of them quite serious. A lot of people prefer vinylester, which has similar mechanical properties, for that reason. Any problems with styrene seem to be theoretical rather than based on case studies. I have not heard of even one case in which it is said that someone had some sort of problem caused by styrene.
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Old 12-04-2008, 02:32   #7
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Properties of materials

Bigcat,

Resin is used to bind and transfer shear stress between load bearing fibers in a composite matrix. The tensile strength of a resin is only one consideration. The tensile part of strength of a laminate should be taking by the fibers anyway.

Important resin property considerations include shear strength, strain to first failure, Young's Modulus, water resistance, shrinkage... To say that ultimate tensile strength is the determining property of a good matrix binder is a gross simplification.

-John
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Old 12-04-2008, 02:52   #8
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Quote:
Originally Posted by planetoftheapes View Post
Bigcat,

Resin is used to bind and transfer shear stress between load bearing fibers in a composite matrix. The tensile strength of a resin is only one consideration. The tensile part of strength of a laminate should be taking by the fibers anyway.

Important resin property considerations include shear strength, strain to first failure, Young's Modulus, water resistance, shrinkage... To say that ultimate tensile strength is the determining property of a good matrix binder is a gross simplification.

-John
This is why I publish the links to the properties, but I find that not everything you mention is available. What I noticed is that not one epoxy advocate trotted out a different statistic and cited how it was 1) superior in epoxy, and 2) vital for a reason that they were happy to explain. You didn't actually explain which characteristic you found more significant, and why, or under what circumstances, either.

I am actually fairly aware of basic engineering. I know, for example, that an unstayed mast is in compression of the lee side, and in tension on the windward side, whereas a stayed mast is always in compression and the stays and shrouds are always (when loaded) in tension.

As a real world reality check, I publish links to quotes from boat builders citing the claim that the ultimate properties of the actual laminates are 95 to 97% as high as with epoxy. I have found several of them.

Unfortunately, none of them give the exact vinylester that they are using, so we can't analyze the facts further.

Finally, you left out two other characteristics I find vital, viscosity of the resin before it hardens, and fire resistance. I think it is extremely rational to chose a resin 95% as strong and vastly more fire resistant. I am less concerned about the price of epoxy than I am about getting a fire retardant resin that is non-toxic to work with.

I am extremely chemically sensitive and have many allergies. Something that adversely affects 1/2 of those exposed to it is sure to lay me low. I have never had a bad reaction to styrene, but I would always make sure I had good ventilation where it was in the air.
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Old 12-04-2008, 04:57   #9
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As far as I can see, it is most important that the resin has reasonable elongation before failure and to be weaker than the fibers, otherwise there is no crack stopping and you end up with a material more like glass, ie brittle. Therefore I would like the Youngs modulus, the ultimate braking strain and, to avoid the arithmetic, the ultimate elongation before failure. Only then can I really make comparisons. The question of the toxicity of the epoxy component of the vinylester still hasn't been answered. I have no idea if this is a potential problem or not. I do know that the catalyst, MEK, is pretty hazardous and can blind and cause neurological damage.
Robert
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Old 12-04-2008, 05:06   #10
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Quote:
Originally Posted by BigCat View Post

I have read that about half of those who work with epoxy will end up with allergies to it, some of them quite serious.
From my personal knowledge of people who work with epoxy, to say about half will suffer from allergies is far from accurate.

I have personally met over a dozen builders who use epoxy, I have communicated by e-mail and telephone with around a dozen more, and of those, only two people have had reactions, (one of them me) both very minor in nature - small rashes in areas of repeated contact, which quickly cleared up when the person was more careful to avoid the repeated contact. (In my case I was rubbing epoxy into my wrist when taking off the rubber gloves.)

In neither instance has the effect been enough to stop them from building. A few of the people I know have worked with epoxy full time for several years and have had no reaction to it whatsoever.
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Old 12-04-2008, 05:44   #11
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Old 12-04-2008, 06:44   #12
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Epoxy is yummy

(note the feet on Jullian in the fore ground, me in the back ground)

This was doing the hulls of my last 30 foot cat.

I dont swim in it quite like that anymore.

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Old 12-04-2008, 07:22   #13
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for the cat i just built i frequently wore bare feet and would have to peel off my epoxy shoes at the end of the day, i have however as the build progresses become more aware of the potential for allergies and so have upped the safety factor(i now wear gloves)
sean
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Old 12-04-2008, 12:23   #14
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More about resins

A lot of this was discussed in the "Will I know the difference if I compromise thread."

Yes, indeed, MEKP is quite dangerous. I learned to fiberglass in the early 70s, and at that time I was told that not only would it make you blind if you got it in your eyes, but that washing it out wouldn't help. I used to swim in resin and acetone, too. I remember how chilled my hands would get from washing them in acetone, because it evaporates so quickly. It's masks and gloves these days.

Actually, for infusion, if the resin is CHP compatible, that is better for infusion, as it doesn't heat the resin as much, and therefore results in less shrinkage. The Vipel fire retardant vinylester whose statistics I published is CHP compatible. I don't know if there are safety issues with CHP.

Derek Kelsall loathes epoxy, and it is he who claims that 1/2 of those exposed to it develop allergies to it. I have heard stories elsewhere of developing allergies to it, but I doubt if anyone has valid statistics. The fact remains that I have read no, I repeat, no stories about allergies to either polyester or vinylester. I posted a page on the other thread that goes into the epoxy toxicity issue in detail, complete with horror stories.

Toxicity / allergies are critical to me-in my house we use baking soda and vinegar instead of harsh cleansers, use unscented soaps and shampoos, etc. I get a pounding headache if I venture down the soap aisle is a supermarket, and react similarly to perfumes. I could go on, but you get the idea. My wife is the same.

I pay careful attention to elongation figures-The fire resistant Vipel, k023 has an elongation of 4.3%, Ashland Derekane 510c has an elongation of 5.5%, and Ashland Hetron 922 has an elongation of 6.7%.

I notice that in Gideon's epoxy, elongation seems to be inverse to tensile strength, with one hardener giving more tensile strength and less elongation than the other. A lot of the resins with the highest properties are to viscous to use for infusion, so the real world properties of laminates won't reflect the engineering figures because hand layups aren't as strong as infused layups with the same resins and reinforcements.

Gideon's epoxy has an elongation of 4 to 5% with one hardener, which gives more tensile strength, and 5 to 6% with the other, which gives less tensile strength. If a range is given, obviously you must use the lowest when engineering, so I don't see the alleged huge advantage for epoxy here.

On the other thread, someone has just posted than an AfricanCat burned and became a total loss, which adds realism to the fire retardancey issue. Vipel k023 has a flame spread rating of 15. Something that won't burn is zero, and red oak is 100 on that scale. Vipel k023 needs no antimony compounds to achieve this.

The USCG is requiring my (149 passenger-rated) cat to have a motorized fire pump that can pump 50 gallons a minute, (no-electric isn't allowed, but you can drive it with a propulsion motor,) an 1.5" UL rated fire hose and professional fire nozzle that can reach the whole boat, really encourages fire retardant resin and requires lots more stuff if you don't have it, and smoke detectors in all inhabited compartments.

They also require an automatic / manual fire system in the engine compartments, and a fire detector alarm in the engine rooms. They don't allow plastic foam mattresses because they are too flammable. I imagine that the many required watertight bulkheads help in a fire, too.

Think they are concerned about fires aboard? Bear in mind that their regulations are usually generated after disasters make needs clear.

In the 'Do you really need a liferaft in a multihull' thread, the main reason that posters could find for saying yes was, you guessed it, a fire aboard
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Old 12-04-2008, 13:51   #15
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We have over 50 people in our factory working with epoxy over 6 years now and only one person has developed an allergy for epoxy , she now works in our store room and has no more problems, the got a rash when touching epoxy and when out of the factory it left her within one day.
I know of people that get epoxy allergies and all these people have been careless in touching epoxy . all our personel is protected with gloves and covered cloting , eye glasses etc to prevent them from touching epoxy , since we resin infuse all the parts in the boats this touching can only happen when we laminate parts together .
Since hull number 004 we even infuse the deck to the hull so even there the epoxy is used in a closed mould situation.
My 2 cents

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