Self Clearing Cooling Water Intake

[Andrew Troup]

A boat I used to sail on had a very reliable engine, but on several occasions the temperature alarm sounded as we were threading a narrow, rocky passage in exposed circumstances.
Luckily, the early warning left us time to make a three point turn to a heading that gave us the best part of a minute's grace before we had to be making way under sail, engine shut down. An engine seizure (which a faulty alarm sender, loose wire, excessive noise from a certain infant, or defunct buzzer would have entailed) would have been very nasty indeed.

I hear from the owner that just a few weeks back he was repositioning the yacht at his home port. He had just left the moles protecting the shipping basin when the wind jumped to a solid 50 knots from ahead and stayed there. Sail cover on, furler and anchor lashed, the harbour entrance abeam rather than downwind .... and the alarm sounded.

He's not one for grisly details, but I got the impression he fell off to a close reach under engine for long enough to gain a scant couple of minutes' sea-room.

He did mention he cleared the offending salt water intake for the heat exchanger supply by removing the hose at the inboard end and giving it billy-o with a dive bottle.

In time, but not by heaps.

Lucky that he's so resourceful and quick thinking (he's older than about 2% of his peers).

And he's still learning ... unlike some, I guess. I think he would have the sails and anchor ready to run, given a similar circumstance in future.

And I will suggest* he fit a quick-disconnect at the cooling hose inboard end, and keep a spare RIB inflation pump nearby, with a matching coupling incorporating a check valve, so the pump doesn't backfill.

He'll probably have a better, certainly simpler idea, but it might spark an even better 'third way' - I've got a couple of other thoughts ... anybody else?

[HopCar]

It might be smart to put one of these fine mesh strainer pickups over the intake. They are pretty much self cleaning when it comes to sea weed or plastic bags.


Link; Groco Perforated Hull Strainers (APHS series)

As you can see they can also be opened when the boat is hauled or by a diver to clean out any barnacles that might grow in the intake.

[Panope]

Not self cleaning but blockages can be rodded clear with the fuel tank dipstick.

1) Stop engine. 2) Remove strainer lid. 3) Pass rod down through strainer, ball valve and out side hull (no inlet strainer fitted). 4) Replace lid. 5) Restart engine.

Process is accomplished without leaving the pilothouse and takes about 30 seconds if one has had some prior practice.

Good for general maintenance (barnicle removal) As well.

Steve

[Andrew Troup]

Might have know you'd have aced this one, Steve !

That's REALLY smart ...

Is the ball valve on a standpipe welded direct to the hull?

(ON EDIT) and is the ball-valve above the waterline (in case you needed to replace it)?

[Panope]

Yes it is Andrew.

Actually, because the location is in such a low and difficult spot (with insulating foam everywhere) I first welded the standpipe to a 5 inch diameter aluminum disc. This weld was done on the work bench so that a quality weld could be achieved on both the outside and inside of pipe.

This component was then inserted into the hull and disk welded from outside only (see pic).

Note: The stand pipe is actually 2 pipes (one inside the other). The inner pipe extends up a couple of inches beyond the outer pipe and has the threads that the plastic valve screws onto. Valve is above the waterline, naturally.

After all the welding (including the flat plate near the top) I poured epoxy into the gap between the tubes to displace moisture and prevent corrosion.

Also, I sandblasted (from the top down) the inside of the inner tube and poured epoxy primer to coat the I.D.

[Panope]

I'll mention that the above system was a direct result of my (and my fathers) experience with Panope's previous "typical" raw water set-up.

She had an aluminum, hull mounted seacock (no hull strainer) and a nearby Bronze basket strainer. About once a year, for the 18 years we used the boat in the water, something (usually a small fish) would get stuck in the seacock. Clearing the blockage required the removal of a hose and a fair amount of water ingress from the little geyser.

Of course all this is occurred while wedged down against a hot engine.

I will also mention that upon a complete disassembly of the aluminum seacock, I discovered pitting in the body (cast, un-coated) approximately 1/2 the wall thickness. This is source of my paranoia and subsequent epoxy-coating inside and out of the (doubled) standpipe.

Steve

[Andrew Troup]

I think that's one place, Steve, where the Liberace principle (too much of a good thing is precisely the right amount) is highly applicable

Kudos, Mate !

I think the twin-wall idea is a stroke of genius, in the context you describe. I bet you thought about it for a while before settling on that...

(and I bet the geysers had their own charm .... or, at least, a frisson of excitement!

I have visions of the aforementioned small fish balanced on the sweet spot of the geyser, like a Dr Seuss drawing)

[Andrew Troup]

At the risk of (further?)embarrassing Steve

One of many things I particularly like about that concept is that it strikes me as a much better option than a seachest in particular respect of jellyfish, and (I suspect) large plastic bags.

I can also see some merit in having a single inlet, but concentrating on making it unconditionally strong and reliable and easy to clear. It does seem that in gradual fouling conditions, by the time one inlet of a twin-inlet system is blocking up enough to make its presence felt (eg to blow an alarm) it is possible that the other inlet is already blocked, in which case switching a Y-valve might be a jump from the pan to the fire.

It's also great to see Panope's standpipe braced back at a high point.
It certainly looks massively secure, what with the larger diameter outer pipe and all . . and it's excellent the way any stresses from that bracket, even if they cracked that outer pipe, would not cause a leak.

Taking the general case, rather than Panope:

Even for short standpipes on alu hulls particularly, I think it can be worth thinking about whether something heavy (like a spare anchor chain, or a battery broken free), charging through the bilge, say in a pitchpole) might conceivably snap off a standpipe. Situations like that are highly improbable, but they're highly consequential, so the risk factor is, I suppose, arrived at by multiplying the two considerations.

Admittedly most alu boats have so much in the way of structure below the waterline that this degree of accidental spontaneous restowage is unlikely, but boats following the "Strongall" precedent might be vulnerable...

[Dockhead]

Here's what I use:

Aquafax » Marine & Industrial Equipment

It takes about 20 seconds to clear any blockage -- close the sea cock, pop off the lid (two thumb screws), open the sea cock, ram a big screwdriver right through and out the through hull, let the little geyser clean out the remaining debris (why God made engine room bilge pumps . . .), close sea cock, screw down the lid, open the sea cock, restart engine, good to go.

It's what UK fishing boats use, hence it's called the "Fisherman Sea Strainer". Simple, cheap, foolproof, effective. It was part of the original build of my boat.

[Blue Crab]

Originally Posted by HopCar

It might be smart to put one of these fine mesh strainer pickups over the intake. They are pretty much self cleaning when it comes to sea weed or plastic bags.


Link; Groco Perforated Hull Strainers (APHS series)

As you can see they can also be opened when the boat is hauled or by a diver to clean out any barnacles that might grow in the intake.

I just checked online and Walmart doesn't carry these. Now wot?

[HappyMdRSailor]

Originally Posted by Blue Crab

I just checked online and Walmart doesn't carry these. Now wot?

If ya squint hard enough.... It sorta resembles 1/2 of a crab claw.... Just yank one off... bisect it and poke some teeny holes in it.... Affix to hull with barnacle glue....

[Blue Crab]

Originally Posted by HappyMdRSailor

If ya squint hard enough.... It sorta resembles 1/2 of a crab claw.... Just yank one off... bisect it and poke some teeny holes in it.... Affix to hull with barnacle glue....

Vision. Some has it some don't.

I figgered I could get HopCar going here but I forgot he's chairman of the board. Probably doesn't get to work til noon. Then it's lunch time ...

[HappyMdRSailor]

Originally Posted by Blue Crab

Vision. Some has it some don't.

I figgered I could get HopCar going here but I forgot he's chairman of the board. Probably doesn't get to work til noon. Then it's lunch time ...

Yea.... I thought it was a stretch even as I was typing it.... Shoulda had 1 more sip o joe first....

I know the chairman position..... I don't feel guilty just yet.... Today....

[Blue Crab]

Originally Posted by HappyMdRSailor

Yea.... I thought it was a stretch even as I was typing it.... Shoulda had 1 more sip o joe first....

I know the chairman position..... I don't feel guilty just yet.... Today....

Sip o Joe my butt! You da Mai Tai Man.

[HappyMdRSailor]

Originally Posted by Blue Crab

Sip o Joe my butt! You da Mai Tai Man.

Shhhh... headed to town for Mardi Gras supplies (mai tais)...