A Smarter Seachest?

[Maren]

Originally Posted by Roy M

Ultimately, I chose laziness over other considerations.

With all the work you’re doing on Wilderness, I have a hard time believing that could have ever been the case.

Thanks to you all for you input, I really appreciate your time considering the idea. Depending on what the interior dimensions of the centerboard trunk (as in, will the dumb end of the thru hull fit?), I think I’ll pursue this is a bit more.

[MidLandOne]

Originally Posted by camaraderie

Well...my Tayana 52 had a sea chest and it is a wonderful idea.
The large through hull connected to a sea cock and a 1.5" hose which then fed a stainless steel cylinder with 6 valved connections off of it. Inside the cylinder was a strainer basket so all water reaching the outlets was clean of debris. The top of the cylinder was a flange with 8 holes in it and fitten on top of that was a rubber gasket AND a drilled plexiglass cover. This was all snugged down by 8 bolts with wing nuts.

As I understand what you are saying is that there was a single sea cock piped to a strainer and manifold/header with branches - not a sea chest built into the bottom of the boat open to the sea (which in my experience the term "sea chest" is more commonly applied to, but sometimes to for a manifold of the type I think you describe).

As in my earlier posts we have similar to what you describe - single seacock, hose to strainer and manifold for distribution, but on a smaller scale, ours being a smaller vessel with lower demands.

Do you recall the size of the sea cock given the comparatively high demands with engine, generator, aircon, etc?

[Roy M]

Maren, You are too kind. Yes, you can use a simple thruhull in the centerboard trunk. I use two of them as the axle supports for my centerboard. I had to install them after assembling the trunk to ensure they would line up. You could install them lower in the trunk to make them easier to install from below (with the board removed, of course). I built my trunk in two halves, splitting the mahogany supports, fore and aft, in half, then glassing the radius onto the mahogany. Then I glued the two halves together using Caulk-Tex, a flexible epoxy predecessor of 3M 5200. If your trunk is built as Jim Brown suggested, without radii, you could also place a thruhull in the foreward or aft mahogany pieces. It's not likely to pick up any kelp or plastic bags inside the centerboard trunk. And if you use a plumbing tee with a cap or plug, you could "rod" it out if it did, shipping only a small amount of seawater. Kind of an horizontal seachest, as it were.

[Maren]

Originally Posted by Roy M

Maren, You are too kind. Yes, you can use a simple thruhull in the centerboard trunk. I use two of them as the axle supports for my centerboard.

Hunh. That's a really good idea!

If your trunk is built as Jim Brown suggested, without radii, you could also place a thruhull in the foreward or aft mahogany pieces. It's not likely to pick up any kelp or plastic bags inside the centerboard trunk. And if you use a plumbing tee with a cap or plug, you could "rod" it out if it did, shipping only a small amount of seawater. Kind of an horizontal seachest, as it were.

I was originally thinking about making a vertical chest out of (predictably) epoxy coated plywood and affixed to the centerboard trunk and hull. Horizontal might be the better solution for space saving reasons.

I was originally thinking about making the chest itself out of (predictably) epoxy coated plywood with a lexan top secured by latches, although Cams Tayana 52 may be the better design. The thru hull would have a 90º downward length of tubing to fill the chest. The water flow would be controlled by a seacock. The tubing ensures the water stays off the seacock and because of the pressure equalization I could control the total volume of water in the chest by shorting the tube -- but short of replacing the tube, I could only increase the water held in the chest. I think seacocks would be needed for the branches off the sea chest, but there may be a better solution. The reason why I came to this has more to do with worst case scenario planning which I think might go like this:

Say we are motor sailing and my darling informs me there is water below and the floor boards are floating. I lift up cockpit access to the engine compartment and, sure enough, there are inches of water in there too with the bilge pump going full speed but unheard over the engine. Since I might need power from the engine if things get worse or last for a long time, I can’t cut off all water. I pull the extension rods to all the non-essential seacocks, the ones which I plan to be coated in yellow vinyl. There red one (engine) is still open as is the main one. My darling cuts power to all the items on the yellow section of the panel and turns on all the items on the red, which includes a high flow auxiliary bilge. We now start looking for the problem.

I’m not 100% certain how this might work with your idea, but I like having a way to clear any obstructions

[Roy M]

Keep it Simple, Sailor! How about one seacock for ALL non-essential water lines and one just for the engine? And a large wooden bung tied next to it in case the leak is at the actual thruhull.....

Having extension rods seems like an unnecessary complication for something that probably will never be needed, and can be activated by simply getting on your knees and reaching into the bilge. And remember, even if the main hull were to fill with seawater to the point where it stopped filling, you would still not sink, though a new engine would probably be on the to-do list.

Lastly, a horizontal seachest, of either epoxy ply or bronze pipe fittings, is still pretty vulnerable to being broken off by someone who loses their balance or steps on it in a rough seaway, unless it is strongly secured to a bulkhead. Keep this idea simple, and strong, and seaworthy. That's probably why I chose individual, localized thruhulls for each function. Murphy's Law hasn't been repealed yet (contact your representative in Congress to remedy that).

[Maren]

Originally Posted by Roy M

Keep it Simple, Sailor! How about one seacock for ALL non-essential water lines and one just for the engine? And a large wooden bung tied next to it in case the leak is at the actual thruhull.....

Having extension rods seems like an unnecessary complication for something that probably will never be needed, and can be activated by simply getting on your knees and reaching into the bilge. And remember, even if the main hull were to fill with seawater to the point where it stopped filling, you would still not sink, though a new engine would probably be on the to-do list.

Lastly, a horizontal seachest, of either epoxy ply or bronze pipe fittings, is still pretty vulnerable to being broken off by someone who loses their balance or steps on it in a rough seaway, unless it is strongly secured to a bulkhead. Keep this idea simple, and strong, and seaworthy. That's probably why I chose individual, localized thruhulls for each function. Murphy's Law hasn't been repealed yet (contact your representative in Congress to remedy that).

A couple of years ago, I was in an Engineering/Cognitive Science class on invention and design. I remember the professor mentioning a series of studies showing, while there is no specific single reason, solutions to problems tend to improve greatly through the first seven iterations. Unfortunately, management usually tends to limit the number to three which is why we see so many marginal products.

I like the idea of using a single seacock for all the non-essential lines and I whole-heartedly agree that any solution needs to simple, strong and seaworthy. But a horizontal sea chest can sit across vertical plywood supports which run all the way down to the bilge and cross braced by another piece of plywood drilled with holes acting as vertical tool storage in addition to support. Or the whole thing can be vertical. While I don't think either will be stepped on, both should engineered survive such a situation. I think AYBC demands it too.

I'm not sure which, if either, is better. One spot to cut off all the water (and maintain) sure sounds great, but that is a lot of hose with water in to leak. Having three or more thru hulls does not make me happy. On the other hand, the individual lengths of hose are shorter and finding a leak should be a bit easier.

Back to the drawing board.

[camaraderie]

Midland...don't recall exactly but would estimate 1.5-2" max. on the intake.

[MidLandOne]

Many thanks for the feedback Camaraderie.

I have now checked our (smaller, 40 foot boat with fewer demands) and is 1-1/4 and runs all the things I mentioned earlier with no problems.

Can fit a lot of water through little holes - useful if wanted, big panic if not wanted .

John

[Jmolan]

Maren as you know I have a centerboard Tri identical but smaller than Roym's. I have two thru hulls. One fwd. that comes off the centerboard trunk and a bigger one aft that comes off the same trunk. Both are located about half way up the trunk and are just inside the compartment so I can see them and get to them boat wihout removing anything.
The aft one supplies the seawater foot pump for the sink. It used to supply the inboard engine but that is gone now.
The fwd. seacock is the same, supplies the foot pump for the sink up fwd.
With aboat that cannot sink, I have not given a lot of attention to these things other than check the hose for cracks and make sure the hose clamps are secure....:-)

[Zach]

Does that centerboard trunk have a removable lid... So you can clean out those through hulls without going over the side?

(Sigh...) Such a cool idea!

[Jmolan]

Originally Posted by Zach

Does that centerboard trunk have a removable lid... So you can clean out those through hulls without going over the side?

(Sigh...) Such a cool idea!

Zach, in fact it does. Another of the great ideas (I am biased) in the Searunner design is that the center board in in the sole of the center cockpit. The whole boat is centered around the board. The mast is stepped on it, you controll everything from the middle of the boat....:-)
But yes the board has a lid (mine is solid, but I need to change that) and if the cockpit were ever pooped (very hard to do) the entire thing would drain through the centerboard top....:-)
With these boats anytime you have a problem under water you can always beach them. I have done that many times.

[partgypsy]

hope it's not too late to comment on this old post. Defever and others provide sea chests for some of the reasons mentioned. Here's one http://www.cruisersforum.com/attachm...ff2ba68d69.jpg

I have a 65' boat with sea cocks all over the place! One sea chest in the engine room would replace through hulls for 3 a/c pumps, jet-head toilet water pumps, watermaker, wash-down, etc, etc. next time I have her hauled...

[James S]

Originally Posted by partgypsy

hope it's not too late to comment on this old post. Defever and others provide sea chests for some of the reasons mentioned. Here's one misc :: Sea chest on deFever 49 picture by PartGypsy - Photobucket

I have a 65' boat with sea cocks all over the place! One sea chest in the engine room would replace through hulls for 3 a/c pumps, jet-head toilet water pumps, watermaker, wash-down, etc, etc. next time I have her hauled...

I wish I would have given it a harder look when I was doing my "BIG" work.
I deleted 4 sea cocks and could have gotten rid of another 2....now only two are below the water line when sitting flat.
One thing a sea chest does is increase dramatically your hose run lengths...but still worth a look.

[Maren]

Originally Posted by Jmolan

But yes the board has a lid (mine is solid, but I need to change that) and if the cockpit were ever pooped (very hard to do) the entire thing would drain through the centerboard top.

This is something I was really impressed with. If you look at a lot of production boats you find they have a few 1-1/2" holes to drain though whereas the Searunner has that ginormous slot to drain through.

[s/v Jedi]

I don't understand the worry about one big thru-hull & hose leaking. Those setup's are not sea-chests, they are a regular sea-cock with manifold.

A sea chest is safe by design. It's normally a square or rectangular hole in the hull with a hinged perforated lid on the outside. On the inside of the hull are four walls than go up to well above waterline. All the thru-hulls and seacocks are in the four walls. The top lid is just for preventing splashing and surging water to come in.

For smaller yachts I would change it a little because you don't need a big hole like the traditional sea chests have. I would take a 3-4" thru hull fitting and mount that in the desired location. Use the nut on the inside and leave enough thread for a bronze cap to be screwed on top during maintenance or emergencies. Now put up the four walls with reinforcing triangles around it and glass & epoxy everything solid and foolproof. Now you can install all thru hull fittings in the walls (2 each wall), cap the ones not needed yet and sea-cocks on the ones used. Reinforce the top of the walls with a flange and cut a nice 1/2" thick plexiglass lid. Cut a gasket from 1/8" thick neoprene rubber.

On the outside, install one of those scoop-strainers with hinged lid.

Now, for any work or maintenance, open the lid, screw the cap on the big thru-hull and run a pump or something to evacuate most of the water, using a sponge or shop vac for the rest, and you can service any fitting/seacock/valve dry while still in the water. It doesn't get better than that.

For discharge, you can do something similar and these are called standpipes. You need enough height above the thru-hull so you can go above waterline. May be you have to move the location somewhat to find a suitable spot. Remove thruhull and replace with a piece of fiberglass pipe. Bevel the hole on the outside for more contact area, and epoxy it in. On the inside, form an epoxy fillet. After cure and sanding, use 2" wide fiberglass tape and epoxy to create a good pipe-to-hull joint. Cut 1 foot lengths of tape; wet pipe and surrounding hull out with epoxy, take a length of cloth and put it around the pipe (much like a neck-tie) with the ends next to each other on the hull. Wet it out and repeat all around. After that, cut a 1 foot diameter circle from cloth, plus a hole in the center that fits over the pipe. Drop it over the pipe onto wet epoxy, covering all the tapes and a little up the pipe. Wet it out and fill the weave. Paint it with BilgeKote. That's one valve/thru-hull less. Cut 4 inches exhaust hose that fits the pipe (the pipe is sold for exhaust service) and fit on top of the pipe. Take a schedule 40 PVC T and glue a piece of pipe in the center connection so that 2" of pipe stick out. Put that into the exhaust hose. Now you can glue reducers and adapters to thread in the T for two discharge connections. You can make bigger PVC manifolds if more connections are needed. Not a single valve.

Jedi has three standpipes for all discharge and they have been maintenance free for the past 7 years. We haul only once every three years and use a rod to clean them out (flushing toilet or something to rinse it out ;-) and paint the inside with anti-fouling.

cheers,
Nick.