opinions re: epoxy vs. plastic hulls, lead vs. iron keels - Page 3 - SailNet Community

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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction
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  #21  
Old 08-10-2008
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Cam,

Your last paragraph says what I am attempting at saying. Epoxy has shown its benefits when done correctly. Both with one off boats, and to a degree with the Novis built boats. I will also admit, as they seem to to a point, had/have some learnig curves when using this product. Hanse is making some boats optional, other this is std, ie epoxy.

If Arglebargle is looking at a Hanse since he mentioned it, at the local Vanouver BC dealer, he likes the boat......buy it! The main thing I am seeing so far with my friends 115, is the manufacture is dragging its assets in admiting the surface gelcoat issue and fixing it, then they are more than happy with there 2nd? C&C boat, the previous being a fiberglass 38'r.

ANyway, as far as which tech, take your pick for where you sail etc.

Marty
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Old 08-10-2008
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NOTE TO ALL.
Any further posts on this thread or forum either bashing or defending the Tartan & C&C brands will be deleted. This is about boat construction materials and methods. You can discuss METHODS and MATERIALS used by different brands but NOT the brands themselves. Go to the brand threads and forums for OPINIONS about boats and brands.
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  #23  
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C'mon Cam, we're just having a little fun.
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Old 08-11-2008
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OK, perhaps this will move the thread back to topic:

So why, exactly, is epoxy resin "better" than polyester resin for fiberglass sailboats?

We've heard statements such as
"Regarding epoxy v. polyester resin systems, there is just no longer any room for debate on the subject. Poly resins are 1960's technology."
I'd like to see better reasons than "because it's old". For instance, modern steels are made with the basic oxygen method, which is 1950s technology, yet does anyone argue against cars made of steel since steel is "old" technology?

For the record, the Boston Whaler 13 debuted at the 1958 Boston Boat Show. It was made with epoxy resin. (Source: "Heart of Glass: Fiberglass Boats and the Men Who Built Them" by Daniel Spurr, page 155.) Production of boats using polyester resin started in the late 1940s. The Marco patent (U.S. Pat. No. 2,495,640) for the resin infusion process was filed June 8, 1945. None of this stuff is new, revolutionary technology.

I was wondering why there was a reference to the 1960s, until I came across a particular boatbuilder's page that said:
"Just as the introduction of polyester fiberglass laminates replaced wood yacht construction in the early 1960's, (builder's name) new epoxy laminate now makes those earlier lamination techniques obsolete."
So, perhaps I'll ask for more authoritative sources than advertising literature when describing why epoxy is better than polyester resin.

Cheers,

Tim
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  #25  
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Epoxy is a better glue in five major areas:

1. Better adhesive properties (the ability to bond to the
reinforcement or core)

2. Superior mechanical properties (particularly strength and
stiffness)

3. Improved resistance to fatigue and micro cracking

4. Reduced degradation from water ingress (diminution of
properties due to water penetration)

5. Increased resistance to osmosis (surface degradation due to
water permeability)

The disadvantage is that it is harder to work with relative to poly/vinal. Which means, maybe you don't want a Monday hull.
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  #26  
Old 08-11-2008
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Or maybe a friday before spring break or some such other long company shut down?!?!?! vs a monday hull?

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Quote:
Originally Posted by monteh View Post
Epoxy is a better glue in five major areas:

1. Better adhesive properties (the ability to bond to the
reinforcement or core)
Yes, I can see that. Epoxy sticks to wood far better than polyester resin. I would only tab bulkheads using epoxy (or at least vinylester) resin.

The only other place I can think of where adhesive properties is important is the laminate-to-core bond. When I've ever come across delamination in a sailboat, it's always been after core has gotten wet. Do we know if wet balsa sticks to epoxy better than it does to polyester resin? I once looked into injecting epoxy into a soft deck, but all the epoxy products I could find insisted the core had to be completely dry.

Quote:
2. Superior mechanical properties (particularly strength and
stiffness)
Numbers I found for tensile strength of the resins are 7,000 psi for ortho polyester and 7,960 psi for epoxy (source: Marine Composites Handbook, table 2.7).

That's about 14% higher, but it's actually the glass reinforcement that provides most of the strength and stiffness in a laminate, not the resin. A blend of glass and resin isn't going to be as sensitive to changes in resin strength, so the actual improvement for the total laminate will be considerably less than 14%. (The only production builder using epoxy resins uses E-glass reinforcement, which is the economy fiberglass normally used by other production builders so their reinforcement isn't any stronger.) I couldn't find what the difference in strength and stiffness would be for a completed panel using e-glass and epoxy vs. polyester.

Quote:
3. Improved resistance to fatigue and micro cracking
Paul Miller of the U.S. Naval Academy studied fatigue of J/24s which are light weight, cored hull boats. His "high mileage" sample boat had an estimated 11,300 hours of use in a sailing school in the roughest part of San Fransisco Bay over 14 years. He measured the stiffness of this boat had dropped by 18% due to fatigue and micro-cracking.

That's a fairly extreme boat usage example, yet the boat was still far from failing. Is fatigue and micro-cracking a real problem on production sailboats using polyester resin?

Quote:
4. Reduced degradation from water ingress (diminution of
properties due to water penetration)
There was an old study of early USCG 40 foot patrol boats (built in 1952) to see how fiberglass properties changed with age and exposure to water. To quote:
"In 1962, Owens-Corning Fiberglass and the U.S. Coast Guard tested panels cut from three boats that had been in service 10 years. In 1972, more extensive tests were performed on a larger population of samples taken from CG Hull 40503, which was being retired after 20 years in service. It should be noted that service included duty in an extremely polluted ship channel where contact with sulfuric acid was constant and exposure to extreme temperatures during one fire fighting episode. Total operating hours for the vessel was 11,654. Visual examination of sliced specimens indicated that water or other chemical reactants had not entered the laminate. The comparative physical test data is presented in Table 4-5."
The properties in the table didn't change much. Probably epoxy would have performed better, but there are a lot of old polyester fiberglass boats (Pearson Tritons are coming up to their 50th birthdays) that still seem to be OK.

Quote:
5. Increased resistance to osmosis (surface degradation due to
water permeability)
This is certainly true. But how bad is blistering on newer (< 10 years old) boats? Many builders have been using iso-gelcoats and vinylester skincoats, which seem to work pretty well. I know Island Packet offers a 10 year warranty against blisters.

So, yes, I can see that epoxy resin by itself does have better properties than polyester resin, but when it's combined into the total system of a production sailboat, is the total boat measurably better? No doubt the boat will be more expensive, but do we have real benefits to offset that cost? Or, put another way, is using epoxy solving real problems rather than perceived problems?

Cheers,

Tim
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Interesting data. As for the cost to value question, anyone know how much extra Hanse charges for an epoxy hull and if it's any lighter?
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Unfortunetly I only have current pricing for the 35 and 32 versions, which do not have the "E" option. The 37 does, IRC about a 1000 lb drop in wt. I am recalling 15K vs 14K for the E version. I do not have pricing on the 37, as that is a bit bigger than spouse and I want to go when we go bigger, then again, who knows, just might of the$$ are there etc. I am also recalling about a $10K option, do NOT quote me on that. Might be less, might be more, how much?!?!?!?!?!

1000 lbs for a boat that size, certainly would give one a bit more SA/disp figure. If one is looking at strictly performance, should be worth it in lighter airs, which I get here in the NW puget sound region frequently. Last 3 races were in winds less than 6 knots!

"ON edit!"
For the 37, the difference is 900 lbs, 15900 vs 15K lbs. SA/Disp is 19-1 for the FG version, and 19.78 for the epoxy version. The 40 is 1100 lbs lighter, the 430 is about 1000 lbs lighter per the website. I'm not going to do the SA/disp figures, as they should be in the +.5 to 1 increase similar to the 370.

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Last edited by blt2ski; 08-11-2008 at 08:19 PM.
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  #30  
Old 08-11-2008
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on hanse 370/400 (+/- "e") additional price for epoxy are 9 553 and 10 897 US$ and 6400/7300 euros.

Last edited by ArgleBargle; 08-11-2008 at 10:24 PM. Reason: typo
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