Bronze or plastic skin fittings and seacocks?

[Bouba]

Would anyone’s opinion change if Sea Sense had let you know his boat was made of steel? Galvanic corrosion and all that?

I’ve read on here people were worried about UV rays being reflected off the seabed and shortening the lifespan of plastic fittings. Not an issue on the East Coast of the UK I’d imagine but elsewhere?

It’s a fair point…the sun here in the South of France destroys everything…I try to cover everything against the sun but it destroys the covers which have to be continually replaced.
Most boats spend most of their lives parked in shallow crystal clear water so it might be a problem

 

[Tranona]

The lever snapped off…closed….my boat had to be towed to the takeout

But that is not the same as the sort of scenario suggested by Zing

 

[Trident]

It’s a fair point…the sun here in the South of France destroys everything…I try to cover everything against the sun but it destroys the covers which have to be continually replaced.
Most boats spend most of their lives parked in shallow crystal clear water so it might be a problem

Not according to TruDesign who tested the materials for UV (in part because many of their products are used above the waterline too) and as they say - "UV resistant - Will not degrade or discolour with ultraviolet light from the sun"

Obviously nothing is UV proof but in a plastic boat the hull should be good for at least 50-60 years as far as we know now (because that's how old they are - it may be that in 40 years time we'll be quoting 100 years) and the TruDesign fittings should last as least as long as the material around it .

People also worry about strength because they are plastic (with little reason as modern plastics, as I'm sure you know, are not like cheap Chinese toys from the 70s) but you can apply 750kg laterally to 1.5" fitting IIRC - so really fat guys standing on an unsupported seacock in the bilge is no issue. I should note I am not in any way paid by TrueDesign to promote them but they are just the best thing out there.

 

[Trident]

1 possible reason.

Metal fittings are compulsory in the “machinery spaces” of coded boats. For me that’s 6 of my 8 seacocks.

This is despite the fact that composite depth and speed through hulls are allowed in those spaces.

This will likely change - as I understand it TruDesign have been working on getting the coding authorities to catch up with technology

 

[Zing]

Can you explain exactly what sort of circumstances would result in a sound metal skin fitting or valve breaking? How would your boat hitting anything damage the through hulls or valves without damaging the hull? Suspect you have a vivid imagination. DZR is probably equally as strong as bronze. Watertightness and corrosion resistance are the key properties of through hulls and valves and bronze, DZR and composites all have those properties.

Lots of things. I’ve hit plenty of hard things in the sea. A few potential options: Floating wood, the backbone of a sleeping whale, a rock reef you don’t notice on the charts, a jet ski bike driven by a drunk etc. in every case I’d rather take that knock onto bronze than soft plastic.

BTW, DZR is weaker than bronze. Plastic, considerably weaker than both.

 

[Trident]

I should also add that I have been using TruDesign for things they were not designed for - in my case as deck fittings for dyneema loops for so called "3D" sheet controls (instead of blocks and tracks) and testing for chain plates (not yet on the boat but have passed all tests so far) . Instead of buying £200 Colligo fittings for running loops through the deck I tried the TruDesign skin fittings (£7.50) as they are perfectly shaped and smooth inside and tested them up to a 2 tonne load with zero deformation (straight pull along the length of the piece and at various small angles that the sheets might go) .. no issues whatsoever. Obviously I don't suggest anyone else do this or that its safe for you etc etc but it proved to me that they are very very strong

 

[Trident]

Lots of things. I’ve hit plenty of hard things in the sea. A few potential options: Floating wood, the backbone of a sleeping whale, a rock reef you don’t notice on the charts, a jet ski bike driven by a drunk etc. in every case I’d rather take that knock onto bronze than soft plastic.

BTW, DZR is weaker than bronze. Plastic, considerably weaker than both.

Which plastic? Have you looked that the impact resistance of TruDesign? The earlier plastic stuff and the cheap above the waterline in PVC and even the quite good Forespar stuff is nothing like the latest iteration . Also as plastic can slightly deform and rebound its perfectly feasible that it would survive better than metal . Your boat so your choice but I don't think there is an definitive evidence to your point of view.

Also, if you install through hulls flush, which is better for speed , rather than the dome sticking out , you'd need a very small point load to not have an object hitting the hull rather than the skin fitting. I know most don't as its too much work but if the likelihood of an impact worries you then you might like to consider the flush mount next time you change your fittings

 

[lustyd]

Regardless of your views of seacocks, it's important to use the correct terminology. Plastic through hulls and composite through hulls are entirely different things, with plastic only suitable above the waterline and generally not with a cock attached.
TruDesign make both, but you should only use their composite fittings below the waterline.


Both metal and composite are more than strong enough, and both can be used anywhere on a boat (unless commercial, where there are additional rules).
Bronze and composite will both last a very long time.
Composite is the only one that doesn't corrode at all or cause condensation in the bilge. As such, composite ones tend to be cleaner and more pleasant to operate.

 

[Zing]

Which plastic? Have you looked that the impact resistance of TruDesign? The earlier plastic stuff and the cheap above the waterline in PVC and even the quite good Forespar stuff is nothing like the latest iteration . Also as plastic can slightly deform and rebound its perfectly feasible that it would survive better than metal . Your boat so your choice but I don't think there is an definitive evidence to your point of view.

Also, if you install through hulls flush, which is better for speed , rather than the dome sticking out , you'd need a very small point load to not have an object hitting the hull rather than the skin fitting. I know most don't as its too much work but if the likelihood of an impact worries you then you might like to consider the flush mount next time you change your fittings

TruDesign use a glass reinforced plastic. We have used similar plastics to make components in plastic injection machinery in our factory. We’ve tested them and they can indeed be massively stronger than polypropylene for example. They are also massively weaker than bronze.

A countersunk/recessed thru-hull is indeed superior. I have them - particularly superior for hydrodynamics.

 

[lustyd]

They are also massively weaker than bronze.

That may well be, but Bronze is also stronger than the composite hull in most boats. Strong enough is strong enough, no point arguing the toss over irrelevant specifications.

 

[Zing]

That may well be, but Bronze is also stronger than the composite hull in most boats. Strong enough is strong enough, no point arguing the toss over irrelevant specifications.

It needs to be as it is protecting a hole in your boat from being exposed. A blow to a thru-hull is not the same as a blow to any section of the hull.

 

[Trident]

TruDesign use a glass reinforced plastic. We have used similar plastics to make components in plastic injection machinery in our factory. We’ve tested them and they can indeed be massively stronger than polypropylene for example. They are also massively weaker than bronze.

A countersunk/recessed thru-hull is indeed superior. I have them - particularly superior for hydrodynamics.

I don't have any TruDesign figures to back this up but they say that have impact tested against bronze (back before 2014 when this email was written) and their reply to enquiry on impact resistance was
"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.”

 

[Trident]

“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).

 

[lustyd]

It needs to be as it is protecting a hole in your boat from being exposed. A blow to a thru-hull is not the same as a blow to any section of the hull.

So are you suggesting that the testing and certification of TruDesign is invalid and you know better?

 

[Bouba]

Not according to TruDesign who tested the materials for UV (in part because many of their products are used above the waterline too) and as they say - "UV resistant - Will not degrade or discolour with ultraviolet light from the sun"

Obviously nothing is UV proof but in a plastic boat the hull should be good for at least 50-60 years as far as we know now (because that's how old they are - it may be that in 40 years time we'll be quoting 100 years) and the TruDesign fittings should last as least as long as the material around it .

People also worry about strength because they are plastic (with little reason as modern plastics, as I'm sure you know, are not like cheap Chinese toys from the 70s) but you can apply 750kg laterally to 1.5" fitting IIRC - so really fat guys standing on an unsupported seacock in the bilge is no issue. I should note I am not in any way paid by TrueDesign to promote them but they are just the best thing out there.

Yes, I agree the TrueDesign are the way to go.

 

[Trident]

I think impacts are very unlikely and TD meets all the standards required in all countries and they claim stronger in impacts than bronze . Whether that is correct is moot but it should also be noted there is bronze and there is bronze... not everyone knows whether the booze they buy will last decades like in the olden days.

Personally I will use nothing else but TruDesign now on my boats and when fitting for others but each to their own and Zing has clearly given his choice a lot of thought and decided differently. Again it's his boat and his choice but good to know people actually think about it. I am often asked, what's cheapest as opposed to what's best when doing work on boats and have to point out that 's not a wise question on things that can sink and kill you!

 

[Bouba]

When all is said and done…the idea of taking a perfectly good watertight hull…and then drilling holes all over is pretty stupid

 

[rogerthebodger]

When all is said and done…the idea of taking a perfectly good watertight hull…and then drilling holes all over is pretty stupid

This is why I only fitted the bare minimum number of skin fittings below the waterline and using a manifold to distribute any water inlets inside the boat

 

[PaulRainbow]

Simply cannot see any logic at all. Metal through hulls and valves perform exactly the same function as non metallic and if the correct grade material is used will last just as long and are generally cheaper. The fact that they are attached to a GRP structure is completely irrelevant. The non metallic valves are a different material to GRP and are isolated from the hull in exactly the same way as metal valves. If you are worried about your engine water intake simply replace it with a DZR (as I have just done) and it will outlast you.

So no logical reason for using non metallic valves and I am afraid it is you that has confused "logic", not others.

You are mistaken, metal will not last as long as composite. You are also mistaken about the cost, by the time you buy a decent through hull, sea cock and hosetail it costs more than a composite unit.

 

[Trident]

You are mistaken, metal will not last as long as composite. You are also mistaken about the cost, by the time you buy a decent through hull, sea cock and hosetail it costs more than a composite unit.

Absolutely - if you want decent Bronze or stainless it will be much much more than TruDesign - even cheap metal is often more expensive. It's win win