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jimbunyard · 03-01-2017, 16:46

Quote:

Originally Posted by smj

The boatbuilder I worked for would lay a hull up in polyester but after that all secondary bonds were done in epoxy. If any resin were to touch wood it would be epoxy. Quite a few of these boats were catamarans used for snorkel trips. They were heavily abused daily in all types of weather. Not one structural failure that I know of. Compare that to the thousands of old boats with polyester tabbed bulkheads that have broken loose. Polyester has its place, but it's not secondary bonds and it is definitely not for use on wood.

Your case would be more convincing if your boatbuilder employer had made identical boats using secondary bonds of epoxy on one and polyester on the other, and compared the results, although even those results would also have been somewhat inconclusive because of the difficulties in ensuring that both boats went through the same conditions.

A purely anecdotal assertion should have no place in making any value judgement, and really has no value at all.

As for the "thousands of old boats with polyester tabbed bulkheads that have broken loose", what do you think the ratio of polyester-tabbed bulkheads to epoxy-tabbed bulkheads is, especially in 'old boats'. I'll take a wild guess at 100,000:1, and that is probably off by as much as a factor of 10; the few I've seen in real life, other than those I've made myself, were all on handmade or reconditioned boats at local boat shows. Just on numbers alone no-one should expect to see many (any?) epoxy-tabbed bulkhead failures.

Once more, and for the final time, some epoxies have some slight advantages over some polyester resins in permeability, adhesion, flexibility and sometimes longevity. Some polyester resins have advantages over some epoxies in cost, usability, and weather resistance. The most important things are understanding where to use which, and employing proper construction and techniques in their usage, regardless of which you use.

smj · 03-01-2017, 17:04

Quote:

Originally Posted by jimbunyard

Your case would be more convincing if your boatbuilder employer had made identical boats using secondary bonds of epoxy on one and polyester on the other, and compared the results, although even those results would also have been somewhat inconclusive because of the difficulties in ensuring that both boats went through the same conditions.

A purely anecdotal assertion should have no place in making any value judgement, and really has no value at all.

As for the "thousands of old boats with polyester tabbed bulkheads that have broken loose", what do you think the ratio of polyester-tabbed bulkheads to epoxy-tabbed bulkheads is, especially in 'old boats'. I'll take a wild guess at 100,000:1, and that is probably off by as much as a factor of 10; the few I've seen in real life, other than those I've made myself, were all on handmade or reconditioned boats at local boat shows. Just on numbers alone no-one should expect to see many (any?) epoxy-tabbed bulkhead failures.

Once more, and for the final time, some epoxies have some slight advantages over some polyester resins in permeability, adhesion, flexibility and sometimes longevity. Some polyester resins have advantages over some epoxies in cost, usability, and weather resistance. The most important things are understanding where to use which, and employing proper construction and techniques in their usage, regardless of which you use.

The boatbuilder I worked for drew his conclusions after decades in the business. My experience is minimal compared to his yet I have come away with the same conclusion. I'm sure the absolute majority of those in the boat building industry would agree that epoxy is more superior by far than polyester in secondary bonds as well as being more impermeable to water. But don't let me or the other experts try to convince you, may your marriage to polyester be a happy one.

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smj · 03-01-2017, 17:17

Just a thought, if epoxy were less expensive than polyester would there be a builder out there using polyester? I guess if using gelcoat as a priority there may be a couple.

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jimbunyard · 03-01-2017, 17:32

Quote:

Originally Posted by smj

The boatbuilder I worked for drew his conclusions after decades in the business. My experience is minimal compared to his yet I have come away with the same conclusion. I'm sure the absolute majority of those in the boat building industry would agree that epoxy is more superior by far than polyester in secondary bonds as well as being more impermeable to water. But don't let me or the other experts try to convince you, may your marriage to polyester be a happy one.

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Why, thank you, and may your astonishing reading comprehension and understanding of basic logic enable you to continue to live a life of enlightened bliss...

ramblinrod · 03-01-2017, 17:32

Quote:

Originally Posted by smj

Just a thought, if epoxy were less expensive than polyester would there be a builder out there using polyester? I guess if using gelcoat as a priority there may be a couple.

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There are many advantages to using polyester resin. Perhaps
the most important is keeping the workforce on the job instead of
off work due to contact dermatitis or cancer.

Of course there are all the other advantages like gelcoat can be reliably applied (and remain adhered for more than 2 years), not requiring UV protection
else rapid failure, ability to extend the layup schedule over many days or weeks, just to state a few.

There are a lot of posts talking about the difference in adhesive and water permeation characteristics, but in reality, it is negligible. Polyester resin adheres and resists water, just fine.

smj · 03-01-2017, 17:40

Quote:

Originally Posted by jimbunyard

Why, thank you, and may your astonishing reading comprehension and understanding of basic logic enable you to continue to live a life of enlightened bliss...

If you were able to read and research the properties of both epoxy and polyester we wouldn't be having this conversation.

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smj · 03-01-2017, 17:44

Quote:

Originally Posted by ramblinrod

There are many advantages to using polyester resin. Perhaps

the most important is keeping the workforce on the job instead of

off work due to contact dermatitis or cancer.

Of course there are all the other advantages like gelcoat can be reliably applied (and remain adhered for more than 2 years), not requiring UV protection

else rapid failure, ability to extend the layup schedule over many days or weeks, just to state a few.

There are a lot of posts talking about the difference in adhesive and water permeation characteristics, but in reality, it is negligible. Polyester resin adheres and resists water, just fine.

I've already stated the advantage of polyester is its ability to adhere to gelcoat. I would rather have a gelcoated boat rather than painted but am happy with an all epoxy build. Just wondering, do they put a polyester barrier coat on an epoxy boat?
I'm also guessing MEK isn't that great for the health either?

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Scout 30 · 03-01-2017, 17:57

There are now epoxies available that can be gelcoated. I'm surprised that a "professional" isn't aware of this. Also, the cost difference between epoxy & polyester resin should never be the reason to use polyester resin. Anyone who's been around boats for a while knows that using inferior materials on boats in order to save a buck actually ends up costing you more in the long run. Of course, if you're a service provider it's your customer that ends up with the bill down the road.

jimbunyard · 03-01-2017, 18:00

Quote:

Originally Posted by smj

If you were able to read and research the properties of both epoxy and polyester we wouldn't be having this conversation.

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What conversation?

smj · 03-01-2017, 18:08

Quote:

Originally Posted by jimbunyard

What conversation?

The one you are having a hard time contributing facts

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ramblinrod · 03-01-2017, 18:31

Quote:

Originally Posted by smj

I've already stated the advantage of polyester is its ability to adhere to gelcoat. I would rather have a gelcoated boat rather than painted but am happy with an all epoxy build. Just wondering, do they put a polyester barrier coat on an epoxy boat?
I'm also guessing MEK isn't that great for the health either?

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MEK is a solvent, MEKP is a catalyst to cure Polyester resin.

smj · 03-01-2017, 18:33

Quote:

Originally Posted by ramblinrod

MEK is a solvent, MEKP is a catalyst to cure Polyester resin.

Most accurate info you've posted on this thread yet, congratulations!

jimbunyard · 03-01-2017, 18:38

Quote:

Originally Posted by smj

The one you are having a hard time contributing facts

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See post #64 (and of course any of my other posts that have actual numbers and examples, rather than your assumptions and assertions), but you're welcome to the last word, of course, since I won't be responding to any more of your silliness.

smj · 03-01-2017, 19:03

Quote:

Originally Posted by jimbunyard

See post #64 (and of course any of my other posts that have actual numbers and examples, rather than your assumptions and assertions), but you're welcome to the last word, of course, since I won't be responding to any more of your silliness.

Here's post 64
Why, thank you, and may your astonishing reading comprehension and understanding of basic logic enable you to continue to live a life of enlightened bliss...
I see no actual numbers or examples.