Keel Cooler

[clancy]

I have often seen in ads for trawlers and work boats mention of a keel cooler. What are these?

[Art Read]

If I understand correctly, the keel cooler is simply a manifold of copper(?) piping attached to the bottom of the hull and plumbed directly to what otherwise would be the "raw water" cooling system on a boat equiped with the more usual thru-hull, wet exhaust system. The keel cooler acts as a heat exchanger, cooling the water from the engine with the ambiant temperature of the surrounding seawater as it is circulated through the manifold.

[Figment]

I've seen two versions of keel cooling.

On wooden hulls, it's generally a loop of pipe that comes down through the hull, runs aft for a while (6 or 8 feet on the lobsterboats I've seen), then makes a u-turn and returns through the hull near the other penetration.

I've also seen a 40' steel tugboat that uses 8' or so of the "deadwood" section of the keel as an integral coolant tank, and the surface area of that section of the hull conducts the heat away to the seawater.

I'm told that they work great. The downside is that you're not using coolant-seawater to muffle your exhaust on the way out, so that needs to be dealt with some other way.

[gary porter]

Originally posted by clancy:
I have often seen in ads for trawlers and work boats mention of a keel cooler. What are these?Clancy, We have a keel cooler on our old fish boat and they are quite common on this type of boat. They allow for good engine cooling without saltwater and glycol can be added as well for colder climates etc. You can also run the engine for a short time when hauled out. The one on ours is much longer than 8' I think but only has a single run down and back. (two copper pipes) some have four.
Here is a pic of ours,,,ignore the soon to be replaced plank.
Gary

http://www.imagestation.com/picture/sraid73/p27f09806e7b98a2435e6c157724de89d/fb768244.jpg

[Ian McColgin]

Figment is right - there are many cooler configurations, from a simple loop to some pretty elaborate grate like arrangements depending on the duty and horsepower. A lesser known trick, often combined with air cooled engins and sometimes with water cooled, it to have a loop for cooling the oil.

Commercial operators preferr bilge or keel coolers as there is one less thing to go wrong and they often preferr a dry stack pointed up for reasons of working safety. Yachties rarely change the load of the boat to any huge degree and therefore a transom exhaust is more convenient.

The long run to the transom is easier to handle if the exhaust is watercooled, providing yet another reason yachts like salt water or salt-heat exchanger - fresh water cooling with the waste water injectd into the exhaust.

Fast boats and many sail boats will also preferr something other than bilge/keel coolers as they are a sourse of turbulence that reduces efficiency.

No reason why a dry stack can't be as muffeled as a wet exhaust, but any level of muffeling takes away efficiency. Fishermen and tuggers and such really care more about the cost of fuel than a little noise.

Also, a sound insulated stack point straight up will toss the sound that way. I plan, with Grana's rebuild, to do that and let the noise annoy any passing gulls. The right inverse cone at the top of the stack should project the noise with relativly little noise below the muzzel. A well and drain at the bottom to get rid of rain water, perhaps a tampon for when the engin's off, and we're in business.

I've thought of two stacks partly for appearance sake and partly to have a nice big raw air intake - an engin room should have huge air circulation - that's also easy to keep engin noise from escaping into the vessel.

Many like to have engin room venting come in through ducts from the bilges to provid a bit of forced circulation there - keep 'em sweet and all - but then you get engin noise intrusion to fight.

Speaking of sweet bilges. I saw a very nice dodge on one boat where each cabin had a grate in the sole with a collection bin just under. Sweep each cabin to the grate and the junk falls into the shallow bin. Every now and then lift the grate to get at the bin for emptying. And the bit of air above the rim of the bin lets air circulate better in the bilge.

Just thoughts.

[htom]

Tom Colvin designed a steel boat that had an enclosed box-beam that was used as both keel and cooler.

[Dave Fleming]

Here is a starting point on keel coolers.

Keel Cooler (http://www.waltergear.com/kc.htm)

[skuthorp]

Well, being an Aussie I thought it was a way of keeping your beer cold under water, and maybe not a silly idea at that!

[Ian McColgin]

Old dodge for keeping you fluids cool - for those of us who've yet to join the refrigeration age:

Drape a wetted rag over as many bottles or cans as practical. Maybe keep them from rolling about by keeping the on the dishrack. Whatever for at least some air circulation.

The evaporation will take the temp down enough that your beverage will be refreshing.

[WWheeler]

What about damage due to grounding out etc? I once looked at a retired tugboat that once used for yarding logs, and wondered how practical that would be.

[Ian McColgin]

Usually you locate the cooler at the lower turn of the bilge so that both the keel and outer turn protect it.

In a grounding, a bilge/keel cooler is much to be preferred as you're likely stirring up silt and trash that will reduce the moving parts of your water pump to little black specks and may well clog the ports.

I sometimes "powerwash" Grana by backing her on a mudbank with a rising tide and just reving her in reverse for 10 minutes. Can't do that if you've a raw water intake.

[rbgarr]

Ian-

Those cabin sole grate/dustbins are a neat (no pun intended) device. Some Hinckleys have them.

But for the rest of the world, 'the New Improved SWIFFER' does the trick! ;) :D ;)

[Ron Williamson]

The local fishtug builders(all steel,all the time) use I-beam keels with the cooler tucked in beside the web protected by the flanges.
Keel coolers also don't clog with ice or slush.This is important because they fish when the price is high,not when the weather is nice.
R