Through hull replacement

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roaringgirl

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Our boat has 6 through hulls below the waterline. Two have been replaced in the eight years we've owned her. We're planning a haulout around when we reach NZ, the half way point in our circumnavigation. I'm thinking about replacing all the through hulls and valves while she's out as a preventative measure. At the moment the valves are all some type of metal (DZR brass?). Why should I not replace them with plastic - I presume it lasts longer as it's not going to corrode?
 
Trudesign valves and through hulls are made in NZ.
A good opportunity to get them for free in return foe load of pub,icity

Round the world yachtsman chooses Trudesign
 
I have read on here (if memory serves correctly) that plastic is ok.
Hopefully VivCox will login and give better advice (or similar if i am actually correct .......... first for all sorts)
 
I assume you are talking about the true design ones or similar? (I did once find a valve from an IBC fitted well sikaflexd to the Hull alarmingly! It was swiftly renewed)

I cant see any reason that they are not fit for purpose, however, they are probobly more susuptable to physical damage such as striking from an object like you might get in a knockdown. The other thing to consider is where they are fitted in an engine room. The potential for fire and heat is greater, and therefore damage to it via those sources. Though one has to also consider that a fire hot enough to damage the though hulls going to have a pretty devastating effect on the integrity of the vessel!
 
trudesign valves are not any old "plastic" they are "nylon reinforcement plastic" which is near as dammit what fibreglass boats are made of.

They definitely won't corrode, ever. DZR won't corrode either but ... are you really sure it's DZR right through? Check with the supplier. There have been tales of DZR valves with brass innards.

I don't think impact risk is significant compared to metal. They have been tested hard.

I don't think the thru hulls are any likelier to burn than the hull itself....again, same material and same contact with seawater. The valves, theoretically....I suppose....

I have a DZR valve for my engine intake, but only because I was pushed for space. The rest of the boat nicely equipped with trudesign.
 
+1 for TruDesign, not ordinary plastic by any stretch. You can fit a collar for support if there's danger of something pretty heavy landing on it inside the hull.

e.g. Very heavy crewman deciding to jump on it.

I didn't bother with a collar on the one I fitted in April as it is in a pretty confined space and you'd really need to try to squeeze a foot on the valve.


As a matter of interest:
I removed a Jeanneau standard valve and skin-fitting, both have been in place since 2008 (launched 2009). The 2" ball valve surface was heavily pitted but the skin-fitting and elbow were in perfect condition. Bright metal throughout with no sign of de-zincification. The whole assembly had no electrical connection to anything on-board. Pretty good chance yours could be in decent shape. Problem is that someone might have bonded them for a while and removed the wires at some point. You also don't know the quality of parts used.

For information:
I suspected that Jeanneau would fit the cheapest parts available. However, I discovered many years ago that their replacement skin-fitting and elbow were expensive and description didn't sound like cheap brass. The ball valve was cheap and I suspected it would be rubbish. The condition of the items I removed pretty much confirmed my suspicions.

Horror story:
A friend fitted forward scanning sonar a very long time ago because he was going to sail within 10 deg. of the North pole. He got a few scrapes on the hull from growlers. :D

He then went on a longer trip around the globe and got hauled out for anti-fouling in Autralia. The pressure washer dislodged the large external sensor and it was left dangling by the wires with a large hole in the hull. Residual sikaflex and water pressure had been holding it in place. The bolts had corroded away completely. Ooops.
 
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roaringgirl said:
Our boat has 6 through hulls below the waterline. Two have been replaced in the eight years we've owned her. We're planning a haulout around when we reach NZ, the half way point in our circumnavigation. I'm thinking about replacing all the through hulls and valves while she's out as a preventative measure. At the moment the valves are all some type of metal (DZR brass?). Why should I not replace them with plastic - I presume it lasts longer as it's not going to corrode?
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If they are DZR or bronze they will not corrode. The weakness is in the skin fitting and the tails which may or may not be DZR/Bronze. The valve bodies themselves rarely give problems as they are not exposed to seawater, but the balls are usually plated brass running in teflon, and the spindle may well be mild steel as the handles often are. If they are exercised regularly the valves are probably OK, but it is difficult to tell the state of the fittings without taking them apart, although some advocate applying force to the whole assembly (big hammer) as dezincified brass fittings will likely fail this test.

No reason not to use TruDesign - the hole and thread sizes are the same but the bodies are larger which might cause problems. however from the way you describe your boat I would guess it is a "quality" boat and the original fittings would be of a high standard (unless it is an HR which is likely to have brass fittings! There is a lot of hogwash surrounding through hulls as plain brass has been almost universal for European boats for the last 30 or 40 years and there does not seem to be a rash of sinkings because of failed through hulls!
 
It’s not hogwash it’s pure luck. Plenty of people have snapped them off and plenty more have easily broken them during replacement. The metal turns to a weak pink foam which is clear to see and obviously a safety issue.
 
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lustyd said:
It’s not hogwash it’s pure luck. Plenty of people have snapped them off and plenty more have easily broken them during replacement. The metal turns to a weak pink foam which is clear to see and obviously a safety issue.
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Indeed.

A gate valve on Jazzcat was seized, so I left well alone until I was on the hard for the winter. My efforts to remove the hose removed the gate valve and a good bit of the through hull as well, and I wasn't using a lot of force, just hand pressure. Glad that didn't happen in the middle of the ocean - or even the middle of the Solent!

All the other through hulls survived a good thump with a rubber mallet, so I figure they can wait until next time.
 
lustyd said:
It’s not hogwash it’s pure luck. Plenty of people have snapped them off and plenty more have easily broken them during replacement. The metal turns to a weak pink foam which is clear to see and obviously a safety issue.
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Work out the number of brass valves and fittings in use as underwater seacocks - anywhere between 6 and 12 on modern boats, it runs into hundreds of thousands. Then find the number that have failed and resulted in a sinking. Sure, some dezincify and although they lose strength, they are not normally under any load and only fail when they are subject to loads outside the normal. That is seacocks don't just fall off the fittings - and it is the skin fittings and tails that dezincify rather than the valves.

That is what I mean by hogwash - it is more complex than "your boat will sink if you have brass valves and fittings" and people need to keep a sense of proportion..
 
Tranona said:
only fail when they are subject to loads outside the normal.
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The one I referred to snapped off when I tried to twist the hose off with my hand. I wouldn't call that a load outside the normal. No, my boat didn't sink, but rocking in a wake could have cause something in the locker to fall on it. If the boat had been unattended on the mooring at the time, I wouldn't bet a lot on her not sinking. Extreme case? Yes, unheard of? No.
 
vyv_cox said:
I know of several skin fittings that failed when someone fell on or levered against them when doing other work. There are several examples on my website under Brass and Bronze.
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The skin fittings on the Bavaria are hidden away in cupboards so difficult to accidently fall on. In my case they were just subject to normal use i.e. turning on an off when arriving or departing the boat.
 
I replaced all mine with Plastic Trudesign units.
They are absolutely brilliant, and I'm well impressed.
I also fitted the Load Collars, just to increase the mechanical strength as my hull is particularly thin (scarily so)
I know of a few Charter company's that are fitting them to all their boats.
Here's their website: Tru Design
 
Stemar said:
The one I referred to snapped off when I tried to twist the hose off with my hand. I wouldn't call that a load outside the normal. No, my boat didn't sink, but rocking in a wake could have cause something in the locker to fall on it. If the boat had been unattended on the mooring at the time, I wouldn't bet a lot on her not sinking. Extreme case? Yes, unheard of? No.
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That is a different load from the "normal" - that is when attached to the boat and doing its job there are no loads on it - yours did not break in normal use. You applied a different kind of load - which may also occur if something falls on it, but most are located where this would not happen.

The point I am making is that the incidence of boats sinking because of a dezincified fitting is very small and it certainly makes sense to "test" them and to make sure any replacements are DZR or composite.

Very relevant today as just decided to move the water inlet with the re-engine and it will be interesting to see the state of the valve and fittings. Like relatively recently installed. All other below water valves are Blakes.
 
The entire point of the seacock is the ability to remove and replace the hose while afloat. As such, that is a normal load.
 
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One slight issue with the TruDesign seacock is that it is larger than the equivalent metal unit, so if you have a tight space available then you may not have room for the TruDesign.
 
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