fittings in steel hulls

[Das_Boot]

Re: Bronze seacocks in steel hulls

My point re: the undercover painting was that is what Awlgrip said. To get the perfect finish and meet the exacting standards set by Awlgrip to satisfy their gaurantee. I only posted the Awlgrip blurb. I have just orderd arround a £1000 worth of Epigrip. It is more tolerant and they have a system that allows the hull to be primed even if it is still wet from the slurry blasting. Whicking is still a problem if you are going to use a brush or roller to paint or to dry off the boat prior to painting. It is also a problem if you allow dust to settle in the wet paint and the profile of the dust is higher than the coating you are applying. Water will be whicked to the substrate by the dust particle. I still maintain the this is the reason that rust appears in the middle of nowhere on reasonably newly painted surfaces.

 

[claudio]

Re: Bronze seacocks in steel hulls

I'm just repeating what the surveyor said, they 'do sink' in Holland and the sea does not have to freeze over, it's just the water in the pipe that has to freeze.

I suppose if you keep an antifrost heater running then provided that the standpipes are in good condition, there shouldn't be a problem.

Do you remove your seacocks to check the corrosion ?

Claudio

 

[Ships_Cat]

Re: Bronze seacocks in steel hulls

Interesting, your comments on the freezing, thanks.

We drain our deck waterways down inside the hull and out below the waterline to avoid staining the topsides. Because the drain position was in an area where the bilge turned sharply we used standpipes for them (welded in vertically so at an acute angle to the plating) as a skin fitting and valve would otherwise stick out into the boat too much, taking up locker room and mean that there would not be a straight drop down the pipe to the sea (more prone to block if not straight).

However, those standpipes are stainless steel in order to avoid the corrosion problems - one just has to epoxy up over the weld an inch or so inside of the pipe far enough to ensure covering any carbon migration from the mild steel during welding.

Not so long ago one forumite said that his standpipes would be ok as they were made from galvanised pipe. I did wonder how he thought the galvanising inside the pipe was going to last any longer than his anodes /forums/images/graemlins/crazy.gif.

John

 

[cormorant]

Re: fittings in steel hulls

I seem to have started something here. I liked the idea of standpipes until the spectre of them corroding and bursting under the pressure of ice reared its head. What do all these steel fishing boats do? Anybody know?

 

[Ships_Cat]

Re: fittings in steel hulls

They generally use steel. It is an important maintenance item and a big percentage of all vessel floodings is due to failure of steel pipe carrying seawater.

The previous recommendation by another of carrying steel standpipes up above sea level to the sea valve is, in my view, extremely foolish and should not be contemplated. You may be interested in the following document - http://www.seafish.org/pdf.pl?file=seafish/Documents/SR536.pdf.

In my view glass reinforced plastic fittings are the best solution (for the reason that one can easily produce a galvanically neutral boat using them) but they do not have a high fire resistance. However, in a small pleasure vessel (such as what most of us have) the risk of fire in the bilge is very low and usually there will be plastic piping after the sea valve in any event. My view is that if a fire in a pleasure boat (which should not have oil and debris in the bilge - we, in fact, also do not store anything in the bilge) is sufficient to melt the water filled sea valves and fittings, the time has probably long gone for one to have abandoned it.

We had one instance involving 2 penetrations (as in my previous post) where it was convenient for us to use standpipes, but these were stainless steel. However, an industrial glass reinforced plastic valve was used on them and the pipework thereafter was also plastic. Care must be taken that the ss/steel weld area is protected, but this is only an inch at most up the standpipe.

John