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Old 01-10-2012, 04:35 PM   #1
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Default An Idea

Through hulls are currently for the most part made out metal and quality bronze is getting expensive. There are a few semi exotic and true exotic plastics that machine well have abrasion resistance that rivals steel and best of all are inert when it comes to electrical currents.

There is a few down sides, first and fore most is expense, these are not cheap plastics. Second is that while most of them can be welded, few of them can be bonded with any form of glue and mastic would have to be a type that retains it own surface tension and remains some what pliable to work.

Just an idea I am kicking around in my head and on the drawing board (CAD). If I go as afar as a prototype I will let you folks know.

Though I would like the thoughts of any one on the forum.

Michael.
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Old 01-10-2012, 07:56 PM   #2
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Oh, Michael, find a good plastic and go for it! I'd even Beta test them, in our unsinkable cat.

My concern was that Marelon which is now used for the non-metallic through-hulls, has a terrible reputation and apparently short life.

For caulking it. 3M 5200 is such a sticky goo, I thought that everything stuck to it. And we were told many, many years ago that Life Caulk was the way to go for through hulls. Is that not true anymore?
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Old 01-10-2012, 09:21 PM   #3
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I might just take you up on that as the design bug has bitten and until I get the plans out of my head they are going to drive me nuts.

Michael
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Old 01-11-2012, 09:06 AM   #4
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G'day bloke - a fab 2012 to you. There are may 'mastics' & 'contact cements' that will stick anything to anything - even rubber heating mats to the leading edge of aircraft - quick ones too. Only been in the plastics business for a few years - just ask - if you wish. Ciao, from down-under, james other aka 'jj-geri-hat-trick'
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Old 01-11-2012, 04:40 PM   #5
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Quote:
Originally Posted by JeanneP View Post
...

My concern was that Marelon which is now used for the non-metallic through-hulls, has a terrible reputation and apparently short life.

...
...this was my opinion too. We have them in the chandlery shelves too but I never came to the idea to install them unter the water line

Now this Marelon Marine Boat Plumbing distributor uses the statement of internationally approved underwater systems.

Do they have a certification by any classification bureau (CG or GL or similar?)

Does anyone has long time experience of an istallation of marelon fittings below the water line?

Uwe
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Old 01-13-2012, 09:20 PM   #6
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Silver Raven,

I might take you up on that. I went and looked at the Marelon website and it is very interesting that the material name is a trade mark and while they will give what they say are test results I don't see a certification number from the groups that they claim.

This means that I can't back check their data. Now what I have seen from this board and doing searches for reviews and complaints is that the they don't seal well and the seacocks (ball valves) have a habit of failing. This has me wondering a good bit about the materials they are using. As the plastics I am looking at are industrial standard materials and are required to survive some pretty nasty stress.

My major problems is that while it is possible, and most of the design work has been done. Can it be done where it is cost effective to the consumer and still have a return on investment. I will have to do a bit more research there once I have sometime to do so.

Michael
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Old 01-14-2012, 08:06 AM   #7
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2nd that on Marelon. I saw a 3/4" one that sheared off when a heavy toolbox slid into it. Only very fast action from the owner saved the boat!

An old shipright told me about his sledge hammer test for thru-hulls and valves. He said if you where confident your valves could take a full force slam from a big sledge hammer then they where strong enough to go to sea with. Otherwise condemn them and put in properly installed ones.

So maybe that big sledge should be part of your product testing?

None of it effects me, as I have a steel boat with all the t-hulls welded in
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Old 02-27-2012, 08:32 AM   #8
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The material I am looking at would survive the sledge hitting it from sliding around without a problem. Finally have the new mill in shop and running (though still have finishing work to do on it) and been looking at this issue in greater depth, biggest problem is the plastics I am looking at are resistant to almost all mastics made and while they can be tapped and thread formed their very nature makes them not hold a tightening well. That leaves cotter pins and castle nuts or welding the plastic to itself ( which has it's own problems) or finally embedding isolated metal into the plastic that would then hold the pieces together.

Still kicking it around and when I have a bit of funds to cut a prototype or three will let folks know and see what we can arrange for some testing.

Michael
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Old 02-27-2012, 11:05 AM   #9
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3M makes some incredible adhesives, and their 5200 marine sealant has performed exceptionally well in so many applications - I wonder how it works with the newer plastics. And Life Seal and Life-caulk, two other adhesive sealants.

Or, is there a way that casting (extruding?) a part can incorporate (fuse) a more adhesive-friendly plastic sheathing? Marine sealants are designed to be nearly permanently flexible to reduce impact/shock or high torque stress failures. -- this is throwing out comments with a lot of lack of knowledge, so if these are "been there, done that, didn't work", I can understand that. Just curious.
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Old 03-05-2012, 11:52 PM   #10
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Hey there,

I've kept out of this discussion because as far as I can tell, the only engineered plastics which might be suitable for reliable and long lasting thru hulls will result in just as costly a component as existing bronze ones. Thus--sticking with bronze seems best for me.

When folks want to replace things because they don't work well--I'll all eyes and ears! However, cost by itself doesn't justify replacing something tried and true--especially when in the overall scheme of things, bronze thru hulls are a tiny, tiny portion of the cost of purchase or maintenance of a sail boat.

On the other hand, if you can find a way to replace stainless steel hose clamps--I just had an (above waterline single) ss hose clamp on the saltwater wash down pump break in half from hidden corrosion. Considering I bought the clamp in 2009 and it looked to be bright and shiny everywhere (except the underside of the hose where a seemingly tiny leak/trickle of saltwater had corroded it nicely!) this was quite some surprise! Heard a "thunk" as the clamp dropped from the hose (in a corner of the boat's head) and then a couple thumps of the pump starting--before hubby and I both scrambled for the head and the electrical breaker box respectively. After drying down the walls and surrounding area of the head, hubby put on another bright shiny stainless steel hose clamp. This makes me want to re-inspect every hose clamp on the boat. Gives me the willies. I know that the underwaterline level ones are double clamped but even so...

P.S. Makes me glad that we turn off the pressure pump breaker when we're not using it and that we shut down all thru hulls and double check this pressure pump to be off when we're away from the boat for more than a few minutes.
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Old 03-06-2012, 10:15 PM   #11
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I agree on the expenses side and it was only when looking at bronze for a client and seeing what the asking price was that I started working on this idea. Which currently is taking a back seat to getting the new mill up and running and large pile of CAD models converted into G-code for cutting on said Gantry router.

The Plastics I am looking at are in the HDPE family (including things denser than that) and a few exotics I know of that where designed in Austria. I have mentioned the idea to a friend of mine in Austria and he is thinking about presenting it to the company he works for as they produce the plastics in question and do a good bit of prototyping on their own.

A replacement for stainless steel hose clamps exists in the Industrial usage and I will have to go bug some of the folks I used to work with many years ago in the industrial trades. Will see what falls out of that tree and if it can handle salt water.

Michael
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Old 04-04-2012, 08:40 PM   #12
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Well been busy and no real progress on the design. Interesting item though is that I have found some mastics that will work with the plastics I am looking at and they are not cheap either. Also found some sources of bronze that are not blood money to buy (not cheap either) so have a few ideas to kick around and work that needs done so that sailing can move forward in the agendas.

I hope everyone is doing well and will try to post any further progress when it happens. I have been off the forum for a bit and life is just that busy. Take care and fair winds.

Michael
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Old 04-04-2012, 10:18 PM   #13
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Hi there--be picky about the bronzes you choose to use. Some are not appropriate to the salt water environment. Know your alloys Also, whatever plastic is used should be one which does not --for lack of a better word--hydrate. Not hydrophilic at all.
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Old 04-05-2012, 03:57 PM   #14
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Quote:
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Hi there--be picky about the bronzes you choose to use. Some are not appropriate to the salt water environment. Know your alloys Also, whatever plastic is used should be one which does not --for lack of a better word--hydrate. Not hydrophilic at all.
Agree whole heartily on the being picky on the Bronzes as most the bronzes used in modern commercial yacht production are aluminum bronzes and while usable have a much shorter lifespan and lower tensile strength than PB series bronzes (also toxic as heck for machining for instrument reeds). There are a few rather good quality bronzes I can get here in the UK, Columbia metals has a rather wide ranging selection and rather helpful.

Plastics wise, yes hydrophobic or those with an extremely high resistance to ingress of water or micro fractures (GRP Blisters anyone). Which is why even given the expense HDPE and UHMWPE are rather high on the list as materials to use. They also have an abrasion resistance that rivals some metals which is also useful.

Thanks for the advice though and take care.

Michael
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