Seacock manifold system

Is it possible to install a manifold seacock system instead of drilling numerous holes into a newly constructed hull? The side benefit would be in an emergency I would only have to shut one main valve off instead of several small ones throughout the boat.

 

Yes. The main seacock has to be able to handle the flow. Sea chests are a common design.

 

Look at the rec.boats.building newsgroup - there is a current thread on sea-chests.
Steve

 

Steve, This may sound lame but where can I find the newgroup rec.boats.building you speak of? Is it located in boatdesign.net or maybe Google?

 

kudu - you can do a group search in google - just hit the "Groups" tab and do an advanced search on "rec.boats.building", search for "seachest" during the last month or so.
Good luck - let me know if you have problems.
Steve

 

Does anyone have any photographs or drawings of a sea chest type system that they could share?

 

Cant find my drawings, but basically for my 47fter I was looking at about a 2" pipe coming up above the water line with a shut off at the bottom. and an inspection hatch at the top for cleaning and antifouling. Then individual pipes with valves coming off the central pipe. Much better than lots of holes. I have been in a situation where that set up prevented a (big) yacht from sinking.

Most of the big yachts (35m+) that I have worked on have a compressed air feed to the sea chest, then if anything gets sucked into it you just open the air valve and blow it out!

Paul

 

Thanks for the reply...Could the same result be obtained from a backflush system similar to one found on a swimming pool. Where an electric motor turns a pump that flushes water (controled by a multi-ported valve) in the reverse flow from normal, to clean the filter system?

 

I agree with you on the safety feature of the sea chest...It is beyond me why builders go through the all trouble of building a fine hull then drill several holes in it..!!!

 

The June 2003 edition of "PassageMaker" magazine has an article on DeFever yachts that features a photograph of the sea chest in the engine room that most Defever's are fitted with. One of the features of their installation that I like a lot is that the sea chest extends above the LWL and is fitted with a gasketted bolt-on clear cover so that checking for and clearing debris in the intakes is easily done.

 

Is there a screen or some other device that would catch debris before exiting the sea chest? Also, how would you measure the required volume/diameter of the sea chest needed?

 

You can install screens. Also, there is a grill on the outside. To figure out the diameter, add all the areas of all the supply pipes.

 

Seachest

Kudo,

Just wanted to pass along a recent mistake I observed in a seachest installation. The vessel though relatively small (40') is intended for commercial/quasi-military operation. I will not name the manufacturer other than they are from the U.S..

There were two immediate problems:

1. Because the engine space is cramped, the location of the seachest did not allow reasonable access for cleaning, service, etc., but it was close enough to the engine to act as a step!

2. This was the second problem. The manufacturer ran a plastic pipe ( approximately 1" dia) straight into the seachest. There was no valve between the pipe and the seachest connection. Within one week of delivery, a local swabbie stepped on the pipe using it to climb over the back of the engine, snapping it off, and creating an uncontrollable flooding situation. (He was immediately elected to stick his finger in the hole until a proper plug could be located)

While a steel seachest and piping is obviously more abuse resistant, I realize that this is not always possible. At minimum I recommend the installation of an isolation valve immediately between the seachest and each piping connection.

Regards

Ray

 

AMEN Raykenn!! My thought was to place a valve between every outgoing pipe leaving the seachest. Not sure if this is "over kill" but it does give you the luxury of isolating an entire section for servicing.

 

I find it easier to install a master seacock. Instead of drilling holes and using several trough-hull fittings, you have a single through-hull. Another advantage is that the main seacock has a threaded out, so it is possible to just screw on pipes, adaptors, reducers or anything else you need.