Through hull fittings

That "thing " pictured ,the sea chest is very poor design. How do you evacuate the water for sea chest service ? Who is going to reach their arm down thru all the stinging jellyfish ? How do you shut off the water supply ? The filter plate at the bottom has a very very, very small surface area filter . Normally the minimiun size of the filter is 2X the intake diameter. A plastic gag would clog it in a minute. Large filter surface area can only be achieved by a big cyclindical filter. That meter high sea chest beast takes up huge space in the engine room and would have to be mounted dead center of the vessel. No need to invent a new sea chest design. The sea chests Ive been sailing with for decades work perfect.

 

nobody's expecting you to understand.. neither recommending a sea chest to a smaller vessel..

 

On even the smallest vessels sea chests are serviceable. The 40 footer next to me has two. Two seacocks and two vetus style seachests. The chests are plumbed together like a double fuel filter assembly...with a single outlet servicing a manifold to supply seawater to equipment. The chests can be run together or isolated independently and the filter cleaned while sea water is being used to cool the engine. No need to invent silly standing box's when elegant solutions are available and well proven

 

Take a breath now and take a look in the Vetus online cataloque http://viewer.zmags.com/publication/fd2b8fee#/fd2b8fee/1 and tell me what you mean. Anyway I don't find seachests there, and have a feeling that you are talking about water strainers in pages 54-55 ?

 

Michael!!! waiting some response..

 

Que pasa Miquel..

 

I suspect Michael is talking about a parallel raw water straner set up where you can isolate a clogged or semiclogged one for cleaning and simply use the other. Back in the thread someone mentioned his seacocks were seized. This is usually the result of not using them regular a similar situation to hand brake cables on a vehicle. Once a year on the hard i usually lubricate mine with plain old vegitable oil which i also pour about a 1/4 cup into my head every two weeks or so when in the water. I also close all my below water seacocks when i turn in for the night and when i leave the boat. Had a friend drown when a hose failed trapping him in the cabin he was sleeping in. The most famous incident being Mel Fishers Son Dirk, his wife and a baby all drowned in their cabin while sleeping when a engine cooling hose failed on their big salvage tug. Does anyone else out there follow this habit, i think it would be a good routine to follow.

 

That's a good habit.. anyway it keep's them in working order, and then you pay attention to those hoses and they never get a chance to fail
What comes to Micheal I'm a bit irritated how he without the ability to see any difference btw stainer and sea chest can't admit his mistake, but maybe next time he's able for a five seconds reconsideration

 

Are you saying that thru-hulls, which could be located several feet under the waterline, should be raised above the waterline and install the sea cock there - probably several feet away from the thru-hull?

Best regards
Singleprop

 

Can anyone explain the advantages of flanges over a simple ss pipe nipple welded in? I can see corrosion problems under the steel flanges, inaccessible and hard to inspect or maintain paint on, , and the steel pipe below it, as well as that under the foam, where condensation drains down into. SS pipe nipples welded in have none of these problems , are far cheaper than any other option and are far more fireproof than any plastic through hulls.

 

The advantage would be following best practice and not using dissimular metals below the water line. If the flange is a few inches off the hull cleaning and painting under is no different than say a flanged frame or an angle stringer,dito for the short mild steel pipe to the flange. The 1-1/2" weld flanges I used were less than $20 for the pair, not exacly a bank breaker there. either one works so use what you like.

Tom

 

Kiwis have been using ss nipples for over 40 years with no corrosion problems.
Getting the back side of flanges sandblasted can be a trick.
As ABS rules state
1.5.2
The committee is at all times ready to consider alternatives & scantlings which can be shown through either "SATISFACTORY SERVICE EXPERIENCE," or a systematic analysis , based on sound engineering principles , to meet the overall safety and strength standards of the guide."
Basically it is stating that what has proven to work over many years, is just as approved as what is based on calculations. '
40 years qualifies , probably far less satisfactory service expereince qualifies, in all aspects of yacht design, far beyond the issue of through hulls, including hull construction, etc etc.
This makes the definition of "Best practice " anything which has been well proven to work,over many years.

 

I don't quite see what you're getting at here. If you're welding a stub of steel pipe to the hull with an inboard flange a few inches off the inside of the hull plate then going to a stainless ball valve you've still got dissimilar metals below the WL. Also getting behind it to blast/wire brush/paint is going to be a PITA. I'd think that, if you didn't want to use stainless, welding a flange with studs on the inner side into the hull plate would work. Bolt the flanged valve body direct to the welded-in flange and no places that are hard to get at. I'll have to think on that one...

There seem to be plenty of ways that actually work out OK in practice however. Also ones where it's obvious luck has played a big role in the boat's longevity. I saw one of these recently - a plastic through-hull on a steel boat with the engine cooling pipe connected directly to the through-hull - no valve.

PDW

 

PDW
The flanges are isolated from each other, whatever type of valve you use bronze or stainless would be isolated from direct contact to hull. When you need a low profile situation the heavy threaded plate welded in the hull to match a flanged valve with gasket and isolate the valve bolts works too.

In my case I didn't feel comfortable welding stainless pipe to hull so I uses
1-1/2" sch 80 pipe about 4" long welded in hull, 1-1/2" weld flanges like we use in irrigation wells, there about 3/4" thick , the upper flange has a short sch 80 pipe nipple welded in with bronze ball valve, Bottom flange has an support brace a few inches long connected to a long. pretty stout setup with nothing more than mild steel in direct contact with hull. Now there is some here that think I should have just used a sch 40 stainless pipe welded to the 10 gage hull with no doubler plate or support to the pipe because thats the simple way well I say no way on my boat
Tom

 

Thanks, that makes sense. I missed the isolating gasket when I read the previous post. Agree about weld-on pipe flanges, I use a lot of Taperlock weld-on bushings to make up drive flanges and the like, makes sense for pipe fittings. I think I'd rather have a bolted flange than a screwed fitting as valve bodies etc can freeze to the threads and be difficult to remove especially where access is limited (ditto tightening them) whereas you can always give a bolted flange a good whack with a soft faced hammer to break the joint loose.

Yes, a pipe welded directly to thin plate (I don't know what thickness 10G is and I'm not about to look it up either, why oh why do you guys hold out against metric????) is not great, too much potential leverage. A big doubler would help of course.

Soon I'll have to give more than casual thought to this subject.

PDW