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Old 06-05-2014, 08:59   #1
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TruDesign composite seacocks?

Finding myself choosing between bronze or marelon seacocks I decided to go with Forespar’s marelon, mostly because I am just done with corrosion.

I don’t want to downplay bronze. It has stood the test of time and I believe it is because of this why many people find it hard to change over to composite seacocks. Wooden boats have also stood the test of time, though I’m not about to get another one of those….at least not as long as fiberglass exists.

Bronze may have the higher tensile strength, but exactly how strong does it have to be? After all, it is a composite hull.

I consistently hear about why no one should use them, but have never heard from anyone that their boat sank because their seacock was made of a composite and not of bronze (well not yet anyway...this is where someone proves me wrong). I also find that many people nitpick over why bronze seacocks should be used under the waterline, though right after those seacocks are the usual hose clamps, rubber hose, etc…that are prone to disaster just the same.

There are cases in which Marelon valve handles break, which seems (so far) to be under pressure from the user (because the valve wasn’t moved monthly as requested by the manufactures at Forespar). In retrospect, I’ve also seen bronze handles break under force as well when they seized from corrosion.

In my quest to find the ultimate composite seacock, I stumbled across TruDesign from New Zealand. They make a below the waterline ball valve/seacock with removable handle you can service/replace.

Has anyone ever used their ball valve for a below the waterline seacock?

I’ve talked to their dealer here in the States and have been emailing with TruDesign in NZ. Apparently, they are quite popular abroad. They have an impressive video showing its strength. They try unsuccessfully to light one on fire with a blowtorch, froze one in ice and even submerged one in salt water for a year (completely barnacle encrusted) and all the while their Teflon ball valve not once gets stuck.

The only issue I see with them is that there is no flange on their seacocks. I was ensured this was not a problem. In an email from their support team they wrote:

“Yes our skin fittings (dome head/threaded, dome head/tail end, and recessed) from the ¾" size up to 2" all meet the IMCI requirement of a 155 kg static load applied to the end of the skin fitting thread. There have been no issues to date.

Our 1 ¼", 1 ½" and 2" size fittings also meet the stricter ABYC / UL1121 requirement of a 227 kg (500 lb) static load applied to an assembly of: skin fitting, ball valve, and tail where the load is applied at the end of the tail fitting (which is attached to the ball valve).

We are currently developing a 'collar' which goes over the skin fitting nut, and supports the ball valve and skin fitting, for our ¾" and 1" sizes so they too can meet the ABYC requirement. The collar basically turns our ball valve into a flanged type one where the load is spread over a great surface area. So to answer your question, yes we are developing a flange for our smaller sizes, but we don't believe it is necessary for the 3 largest sizes in our range as they already meet ABYC.

Regarding your comment on them cracking - Our glass filled nylon 6 composite has very good impact resistance, much better than bronze or brass which is prone to cracking especially at lower temperatures or if electrolysis has occurred.”


Anyways, sorry for the lengthy post I’m just really looking to hear from anyone that has any experience with these seacocks. Right now it's a dual between Forespar's Marelon and TruDesign...


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Old 06-05-2014, 10:37   #2
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Re: TruDesign composite seacocks?

thanks for posting the link. the only time ive seen a composite through-hull fail was when a 60lb spare alternator had flown around and eventually cracked it, the marlon valve though actually survived.

im with you on eliminating corrosion. when it comes time to drill the holes in my 40' build, all composite skin fittings/valves - properly installed - is the way ill go.
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Old 06-05-2014, 21:06   #3
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Re: TruDesign composite seacocks?

I've had Spartan bronze seacocks for thirty years now with no issues on a fiberglass hull. I service them every other year. Were I to buy or build another fiberglass boat I'd ensure the seacocks were those which have passed my thirty year test. If I was going to have a steel or aluminum hull I'd consider a plastic seacock.
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Old 07-05-2014, 19:19   #4
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Re: TruDesign composite seacocks?

Thanks for the replies.

Please correct me if I'm wrong (which is probably the case). Is bronze from 30 years ago made of better quality than today? I've heard that good quality bronze (marine brass w/arcenic) is very hard to come by nowadays...
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Old 07-05-2014, 20:52   #5
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Re: TruDesign composite seacocks?

Spartan still builds the same quality seacocks they made 30 years ago. Nearly all of my on-deck hardware is Spartan bronze (cleats, fairleads, midship cleats, winch bases, staysail boom pedestal, opening ports, etc) and is as good as new, better actually, it now has the 30 year old patina.
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Old 07-05-2014, 21:03   #6
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Re: TruDesign composite seacocks?

If you buy the same grade of any bronze alloy from a reputable source as 30 years ago, it will be generally as good or better in adherence to spec and consistency of constituents, and freedom from unwanted inclusions.

However, back then, it is likely that many bronze valves (especially for low volume items like seacocks and thru-hulls) were sandcast.

More mass-production foundry methods, using permanent moulds, put a premium on narrow freezing temperature ranges and fluidity at pour temperature, (for reasons of cycle time) and possibly also on the self-degassing properties of the molten metal - (sand moulds are more permeable to gasses).

The alloys also need good hot-ductility, not because it's needed in service, but because the metal mould is unyielding and there's a risk of the casting cracking, due to differential contraction of the mould when it is rapidly cooled from outside (again, for reasons of cycle time)

This means a narrower selection of bronze alloys, whose "in service" properties may conceivably be inferior to those used for sand-cast items.

I'm not in any position to confirm that they are inferior, however.
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