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On the slip I removed three old thru-hull fittings. Two were for a pump-out toilet that was not on the boat when I got it and was not gunna be replaced. The valves take up valuable space under the v-berth area and I got a bit nervous some time back when I was sanding and bumped the valve handle enough that it started weeping.

The third valve was under the sink. With its handle I could not tell by just looking if it was open or closed. The wood bases of the valves were rotting away which didn't give me confidence. And the sink valve was in a place that kept getting in the way of nearly everything I was trying to store under the sink.



Taking the valves out was easy enough. Couldn't unscrew them so used a multitool to cut through the wood base and through the pipe.



Used a grinder on the inside to make the large recessed area, cut a heap of different sized fibreglass circles (okay, most of them were more square than round), stuck plastic on the outside and put the wetted cloth on the inside. To wet the cloth I put about half the thickness of circles in an icecream container and poured the epoxy onto it. That was easier for me to make sure it was thoroughly wetted than other times when I lay the cloth down dry then wet it.



After it was dry I sanded flat. Under the sink I cut a new hole and installed the new valve.

Why didnt you use old holes?

bornfreee wrote:Why didnt you use old holes?

Too small for fishing through.

The old under-the-sink hole was close to the front of the cupboard meaning I had trouble trying to use the space in the cup effectively. By moving it back 30 cm it makes it way more usable and for me it was worth the extra work.

troppo

Might pay to replace that plastic valve with a bronze ball valve Troppo.

Phillip wrote:Might pay to replace that plastic valve with a bronze ball valve Troppo.

Hi Phillip

I was wondering if some observant person would notice the valve. Well spotted! Valve and thru-hull is actually made of Marelon [http://www.forespar.com/what-is-marelon.shtml so I am hoping it is as tough as they say.

troppo

Troppo,

The important part of all that data is this one....Flexural modulus and relates to impacts.

The Marelon only comes to 1,300,000 mPa

Whereas bronze is a high 15,000,000 mPa

That means a bronze fitting will be over eleven and a half times stronger.

To put this into context we had a Top Hat leave the Camden Haven some years ago
and on crossing out over the bar struck a couple of big waves which, while causing the Top Hat
to rear up and down a bit did not seem to be a problem, or so they thought!

A little later they found water in the cabin and had to call for help.
They were towed back and pumped out until they went onto the local slip.

Turns out that one of their batteries had torn loose during the bar crossing and it
had smashed a plastic through hull fitting.

They put a bronze one back!

End of lesson.

Phillip,

I think that you may be misjudging Marelon. Every magazine article I have read about it said it is an excellent material for through hull fittings and valves. Marelon is not a new material and is now well proven.

I do not know whether it is superior to the best quality bronze, but nowadays it is difficult to know what quality of bronze you are buying so you may be better to buy Marelon.

Regarding the comparative strengths of bronze and Marelon, the figures on the Marelon website show that bronze has a tensile strength 30% higher than that of Marelon. A high tensile strength is undoubtedly desirable. However, as you point out, the flexural modulus of bronze is many times that of Marelon. I would think that, for through hull fittings and valves, a low flexural modulus is highly desirable as it means that Marelon will deform more readily and therefore absorb (without breaking) the knocks from a roving battery much better than bronze.

Therefore I think Troppo should feel reassured that his Marelon fittings are well suited for their use and probably better than bronze.

I replaced my plastic fittings (unknown type) by bronze about ten years ago, but next time I replace them I will probably choose Marelon.

Steve

Whilst I am an advocate of bronze fittings, it sounds to me like the errant battery was the bigger culprit in the example cited.
Cheers,
Tom