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Through Hulls

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Created by shane450 > 9 months ago, 30 Jul 2019
shane450
54 posts
30 Jul 2019 8:11AM
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Boat is a 2006 Model , no leaks just the usual green scale , I know the usual thing is if it ain t broke but I m all about preventative , when would you change them out ? would 12 years equal they are due to be changed ?

Plus I was thinking of going with the Tru Designs units .

blackswan
WA, 45 posts
30 Jul 2019 8:37AM
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we had one snap off in a 2010 Hanse, not a nice experience! we replaced all through hulls with Tru Design.

Its recommended to replace the brass ones that come with European production boats before 5 years.

Zzzzzz
513 posts
30 Jul 2019 9:42AM
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There has been some interesting tests done on these New Zealand glass plastic thru hull fittings while they where wet not good my choice would be these you get what you pay for.
shop.classic-boat-supplies.com.au/boat-hardware/hull-fittings/bronze-seacocks-hose-clamp/

boatbroke
NSW, 5 posts
2 Aug 2019 8:41PM
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Hi Shane,

Always a good idea to check them all when the boat is slipped each year (along with the bilge pump/battery).

After the antifouling is finished, go through all of them and make sure the ball valves move freely by hand. Spray Lanox from the out side when the ball is closed and open/close (repeat a few times).

The poo outlet will generally be the worst culprit, most likely to need changing, due to the corrosiveness of faeces.

A wire brush and a spray of Lanox to clean off the green scale inside doesn't hurt either.

However, a bit of green scale is not the real worry. If under the green scale the bronze if turning a light 'rose' colour it is a sign of electrolysis and the bronze can become brittle. This is the real worry.

Stainless are good, but they have a bronze ball (the ball valve) that is chrome coated. The skin fitting will be ok, the inside ball can still seize if not serviced or experience electrolysis.

Plastic ones don't corrode, always a good thing.

Make sure there is bungs tied to all of them regardless!

Good luck!

Adam

scaramouche
VIC, 190 posts
4 Aug 2019 4:38PM
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Can't go wrong with Tru Design

Karsten
NSW, 331 posts
5 Aug 2019 10:00PM
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Select to expand quote
Zzzzzz said..
There has been some interesting tests done on these New Zealand glass plastic thru hull fittings while they where wet not good .......


Hi Zzzzz, as you can see, some forum members are keen on "Tru Design" fittings. Would love to read about those test results you mention - any chance you could provide a pointer to them ?

Zzzzzz
513 posts
6 Aug 2019 1:29PM
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Select to expand quote
Karsten said..

Zzzzzz said..
There has been some interesting tests done on these New Zealand glass plastic thru hull fittings while they where wet not good .......



Hi Zzzzz, as you can see, some forum members are keen on "Tru Design" fittings. Would love to read about those test results you mention - any chance you could provide a pointer to them ?


Ok please bare with me I had a hell of Time finding what I had read I will copy a short bit off the forum then put the link to the full article.
here is the copy ....,.,


Re: Replacing Skin Fittings And Ball-valves The Boat's 5 Years Old.

Lagoon4us - Would you be willing to accept a thru-hull and ball valve that lost 60% or more of its strength within 7 days of installation on your boat?...




Re: Replacing Skin Fittings And Ball-valves The Boat's 5 Years Old.

Lagoon4us - I asked my question in all sincerity. If you knew that within a week of putting your thru-hull/seacocks on your boat they would loose over 60% of their tensile strength and flexural modulus, would you buy them.

I have, by the way, emailed TruDesign and asked about their thru-hull/ball valves, twice - type of resin and % and type (long/short) glass. All they were willing to tell me is that they were glass reinforced/ nylon resin. Nylon resins are pretty straightforward, the most common are Nylon 6 or Nylon 6/6. They are virtually the same for marinepurposes. It's most likely TruDesign uses Dupont Zytel glass filled nylon, or at least the nylon resin and has a local compounder make the molding pellets.


My goal was simply engage you in a conversation by asking the question: "Would you be willing to accept a thru-hull and ball valve if you knew it would lose 60% or more of its strength within 7 days of installation on your boat?" And then providing you with the following information for you to use as you saw fit.

You mentioned that the fittings met ISO 9093-2. I'm well versed in ISO 9093-2:2002E and have raised a few questions regarding the wording of the standard, which no one at ISO seems capable of answering.

In ISO 9093-2 there is the following:

4.5 Mechanical properties
Materials for fittings shall meet the following minimum physical properties at room temperature in dry condition:
? tensile strength: 60 MPa (ISO 527); 8,700 psi
? flexural modulus: 2700 MPa (ISO 178); 391,600 psi
? impact strength: 9 kJ/m2 (ISO 180/A).
NOTE The mechanical properties relate to the materials in the non-stabilized condition.

My questions were:

1. Why would you use a "dry as molded" (at this point there is virtually no moisture in the part) for a standard when the part will spend its life saturated in water?

2. Why would you want to test the parts in a "non-stabilized condition?" Especially when nylon becomes stabilized with moisture.

They weren't able to provide an answer.

The ABYC has a similar statement in their H-27 standard.

The fact is some plastics degrade in water, and some degrade in water in a serious way. Nylon is one of those plastics. Nylon is great as rode, it absorbs moisture and elongated (stretches) and swells. There are a lot of excellent plastics out there that would give bronze and SS a run for their money, nylon is not one of them, I've worked with nylon and just don't feel it the plastic for that purpose.

The fact is nylon is hydroscopic, it absorbs tremendous amounts of water. It softens and swells. Forespar's Marelon, (AKA Dupont Zytel 13% glass filed nylon 6/6) will lose 57% of its tensile strength and 64% of its flexural modulus within a week of being put in the water. Nylon 6 is nylon 6. I can tell you with 98% certainty the TruDesign fittings will do the same.

Nylon's a wonderful product, just a plastic I'd use for a thru-hull or seacock on a boat.

I'll stop there for now.

Good luck and fair winds

Zzzzzz
513 posts
6 Aug 2019 1:39PM
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Here is the full forum you will note Trudesign never answered why they only do the test dry and not wet absorbing water is the weakness.
www.cruisersforum.com/forums/f139/through-hull-warning-102317-6.html

woko
NSW, 1514 posts
7 Aug 2019 7:55PM
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Well I just read through that link to another forum and it sorta deteriorated into an argument. The focus was on older style forspar gear. And I guess it stands to reason if you apply shear pressure to a tube, plastic will give before a metal one ( good seamanship would dictate that loose cannons shouldn't be stowed near seacocks) .l must of missed the part about the material absorbing water and losing strength.
for the sake of curiosity I have a trudesign seacock to be installed, I will weigh it and soak it to try and determine its water absorption

shane450
54 posts
9 Aug 2019 5:55AM
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Select to expand quote
boatbroke said..
Hi Shane,

Always a good idea to check them all when the boat is slipped each year (along with the bilge pump/battery).

After the antifouling is finished, go through all of them and make sure the ball valves move freely by hand. Spray Lanox from the out side when the ball is closed and open/close (repeat a few times).

The poo outlet will generally be the worst culprit, most likely to need changing, due to the corrosiveness of faeces.

A wire brush and a spray of Lanox to clean off the green scale inside doesn't hurt either.

However, a bit of green scale is not the real worry. If under the green scale the bronze if turning a light 'rose' colour it is a sign of electrolysis and the bronze can become brittle. This is the real worry.

Stainless are good, but they have a bronze ball (the ball valve) that is chrome coated. The skin fitting will be ok, the inside ball can still seize if not serviced or experience electrolysis.

Plastic ones don't corrode, always a good thing.

Make sure there is bungs tied to all of them regardless!

Good luck!

Adam


Thanks Adam

shane450
54 posts
9 Aug 2019 6:03AM
Thumbs Up

I m still researching , many fair points for both sides of the argument , I am leaning towards Tru Designs above the water line and Bronze/SS below still weighing up , I haul out in October so I have a few months yet to make a final decision .

I have taken some very good advise and in every bilge I have a plug kit ready to go for the specific thru hull sizes in that bilge , before I just had a emergency kit in the utility room .

thanks all for the replys



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