Plastic Classic Forum

Does anyone have experience sending a plug from their hull out to a lab for evaluation?

I was talking to a naval architect yesterday who told me that for new fiberglass inspected vessels the Coast Guard requires a full lab analysis on a plug taken from the fiberglass hull, and that this sort of full test costs about $1,500 (ouch). He suggested that there might be lower cost lab analysis available that could be useful for evaluating older fiberglass hulls.

What would you expect to learn from a core sample that you couldn't see from the sample yourself--the strata of layup, resin starvation, voids, etc (and why would it be important?)?

What exactly would they evaluate? Strength? Moisture? If the epoxy was fully mixed?

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What would you expect to learn from a core sample that you couldn't see from the sample yourself

Well that's the point...I don't know.

Apparently some people feel there is value in sending a sample to the lab or the labs would go out of business ;-)

I'm hoping that someone with actual experience using a lab can tell me more about it.

This is for manufacturers (and if I recall not all are subject) - when they build a new boat they have to get some sort of certification approved before they go into production. It's more engineering testing then anything....Strength, bonding, etc....I believe they only have to do it once pre production....

Ahh I see. Sort of like UL testing.

Actually, it sounds like (at one point, at least) UL did do fiberglass testing. I can't copy/paste from this article, but if you go to the link below and then "turn" to page 65 (as numbered in the lower-right hand corner), middle column, you'll read that Bill Tripp had some fiberglass samples from his Javelin design sent to UL for testing.

The reason for the testing was that a customer had felt that the laminate of one of these Dutch-built boats was too thin. So Bill had 4" square samples (one from each side of the hull just above the waterline) cut out and sent to UL.

The article's text describes how the "returned samples, whose resin had been burned off, showed the laminate schedule to be exactly as specified, and that the resin-to-glass ratio was ideal -- better actually than most contemporary American builders were achieving."

So that illustrates one type of result that could be achieved by testing. I'm thinking that perhaps in an older boat, the same testing could ascertain if there had been any - or how much - hydrolysis occurring? (Although maybe you would need a sample of the same boat when new to make a comparison, perhaps you could still get a meaningful figure for the current e state of the laminate?)

I hope you don't mind me piping in since I haven't had direct experience with the testing; it's just that I remembered reading about this in the article I've linked to.

http://www.proboat-digital.com/proboat/20070203/?pg=59

UL will test anything you pay them to test. Including the limits of logic.

I believe the coast guard testing your are referring to is for passenger vessels caring more than 6 passengers for hire. i think the test is mostly a fire test to see how it burns as many of the older glass boats burned real good and the coast guard didn't like that. You don't need this unless your trying to be a charter boat.

Figment wrote:UL will test anything you pay them to test. Including the limits of logic.

Do you have a link to the results?

Testing still underway, evidently. Follow progress here.

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