Query about stopcocks and skin fittings

[KellysEye]

>If you are looking to using plastic and have any doubts whatsoever regarding using fibre reinforced through hull fittings and valves I suggest that you get a through hull fitting and try and "shear" it as some have claimed they are not reliable for.

Don't know where you got the idea of plastic from or fibre reinforced.

The Forespar marine sea-valve is made of Marelon, a polymer composite. Marelon is a proprietary formulation of polymer composite compounds using composite polymer resins and additives to produce a superior marine-grade product.

Marelon is ISO (International Marine Certification Institute) 9093-2 Certification on all Marelon integrated plumbing systems valves ('93' Series). The Forespar Marelon Ball Valves and Thru-hull fittings meet and exceed the ABYC H-27 and ISO 9093-2 Standards as presently written in all respects.

As I said I've never heard of one failing.

 

[prv]

Don't know where you got the idea of plastic from[...]

The Forespar marine sea-valve is made of Marelon, a polymer composite

Or what most people would colloquially call plastic.

Pete

 

[CelebrityScandel]

>If you are looking to using plastic and have any doubts whatsoever regarding using fibre reinforced through hull fittings and valves I suggest that you get a through hull fitting and try and "shear" it as some have claimed they are not reliable for.

Don't know where you got the idea of plastic from or fibre reinforced.

The Forespar marine sea-valve is made of Marelon, a polymer composite. Marelon is a proprietary formulation of polymer composite compounds using composite polymer resins and additives to produce a superior marine-grade product.

As prv has already said, Marelon is a plastic and is fibre reinforced. It is also not the only reinforced plastic suitable for marine use.

I do not know what the base polymer is for Marelon but would not be surprised if it was nylon as that is commonly used for other reinforced plastics for similar applications. Why I mention that is interestingly on Forespar's website they give comparisons of tensile strengths as between Marelon and other materials including nylon. Somewhat mischeiviously the tensile strength they give for nylon is for NON fibre reinforced nylon whereas that for Marelon is, of course, for the fibre reinforced polymer.

 

[CelebrityScandel]

I know its anecdotal but if the worst can happen then it usually does, luckily to someone else. And whatever is tried to be proved with anecdotal evidence can usually be disproved with a different story. Oh well!

We were in Lagos for the winter and a Dutch boat, 2 along from us, went out to anchor in Alvor, 5 miles along the coast. Alvor has a dredged entrance lined with large rocks to maintain a wide steep sided entrance channel. As they were leaving they got a rope around the prop and lost all drive causing them to drift on to the channel sides. A skin fitting sheared off and they sank.

The boat, one of the windscreen cruisers, was in the yard for a few weeks and we went aboard for a look-see. What a mess, how could so much mud come through a 2 inch-ish hole? It was sent back to Sweden for a complete refit internally. They lost a full season.
Maybe modern reinforced plastics are now stronger but its something I’ve not researched. I think you should.

Barry

As I have already pointed out, reinforced plastics used for through hulls do not shear. But like everything (including as discussed like metal through hull fittings too) there are cheap inferior products and it is not unknown, for example, as I have seen for amateurs (and maybe even some boat builders) to foolishly use ordinary flanged tank fittings as through hull fittings.

It seems a long stretch to believe that the consequences of a rope around a propeller resulted in a sheared through hull of correct material as every such fitting I have seen is practically flush with the exterior of the hull and certainly nothing for a rope to catch on. Sounds like scaremongering to me.

 

[Stooriefit]

... A skin fitting sheared off and they sank.

Do we know what type of material this skin fitting was made of?