So I have a question for the 'brains trust out there. My latest project boat is aluminium hulled(plated in 5083 grade) and we made a skin fitting for the engine water intake out of a solid billet(probably structural grade?).
My concern is I'm worried it might eventually 'fizz up' in the salt water. I do not like plastic skin fittings under the waterline and on any other boat or yacht, I would normally replace with bronze or S/S.
That is okay on a glass or wooden vessel, but aluminium has no other compatible metals that I'm aware of either.
Can't get hold of any marine grade aluminum skin fittings.
Which way do I go with this?-Cheers CR. 
Select to expand quoteCoolRunnings said..
So I have a question for the 'brains trust out there. My latest project boat is aluminium hulled(plated in 5083 grade) and we made a skin fitting for the engine water intake out of a solid billet(probably structural grade?).
My concern is I'm worried it might eventually 'fizz up' in the salt water. I do not like plastic skin fittings under the waterline and on any other boat or yacht, I would normally replace with bronze or S/S.
That is okay on a glass or wooden vessel, but aluminium has no other compatible metals that I'm aware of either.
Can't get hold of any marine grade aluminum skin fittings.
Which way do I go with this?-Cheers CR.
How does epoxy go with Aluminum The true designs usually are epoxied in place Id send them a email and ask them in N.Z They also sell a back up washer thats fitted between between the ball valve and the skin fitting
as an option which gives you more certificates to flash at the insurance companies
support@trudesignplastics.com
Marine grade Aluminum
You might have to get them made out of billet and turned down
I would be reluctant to epoxy the True Design valve direct to the hull HG.
Another function of aluminium is that it is hard to get paint or anything else for that matter to stick to it.
But, you have given me an idea. I might trawl the 'net' and see if there are composite skin fittings available out there.
Got to be better than plastic.
Select to expand quoteCoolRunnings said..
I would be reluctant to epoxy the True Design valve direct to the hull HG.
Another function of aluminium is that it is hard to get paint or anything else for that matter to stick to it.
But, you have given me an idea. I might trawl the 'net' and see if there are composite skin fittings available out there.
Got to be better than plastic.
Titanium reacts with almost nothing.
I would of thought a alui tube welded in the hull with reinforced hose connecting to a plastic, bronse, S/S seacock would be fail safe..
make sure you use double hose clamps though for insurance reasons!
Southace has got it there. On my alloy Peterson 42 I did exactly that. I had a piece of alloy pipe welded in with an internal backing plate with four gussets.
The pipe was threaded to take an alloy bodied ball cock with stainless ball and teflon seal rings. They are available but where is the puzzle.
Where I you, which I am not, so the decision is yours, I would weld in the threaded stand pipe and screw onto it a top quality ABS plastic ball cock.
Just to clarify terminology here.
There are valves, of which there are three types. Screw down, screw down non return and gate. All are actuated by a wheel on a threaded shaft.
There are cocks, of which there are two types. Tapered and ball. Both are actuated by turning a lever 90 degrees.
There are some variations on the above two plumbing items but for our purposes on yachts, that covers it.
Edit:- With aluminium hulls, weld in your skin fittings.
Select to expand quoteHG02 said..
its does when there's a Ducati bolted to it 
Methinks you are perhaps thinking of magnesium.
Appreciate all the input good people-Gives me a plan of attack now.
On advice offered,was going to weld a tube onto the hull, but then followed a link from HG, where you can in fact get certified composite skin fittings.
As the hull is finish painted inside and out, I will run that way now.
Had the hull been still in the 'raw' and maybe on the next one, will do a welded standpipe style for anything like that.
Thanks again.
CR.
Select to expand quoteLooseChange said..
HG02 said..
its does when there's a Ducati bolted to it
Methinks you are perhaps thinking of magnesium.
My Dy mags were magnesium not on frame
Hope it works out for you C.R. I'm envious of your skills
