keel cooling

[microlyn]

I have a glass fibre 27 foot boat with a BMW 2.5 litre turbo diesel 6 cylinder engine, i want to fit ouside keel water cooling pipes to cool the engine, can anyone give me any information about this, ie the length and size pipes and material of piping an any other usefull information please

[Landlubber]

Go to Professional Boatbuilder, Dave Gerr wrote a very good article on this subject earlier on this year, you can read it on the site.

[CDK]

Sounds easy, but isn't.
Common external cooling is done with one or two galvanized steel pipes running the length of the keel, with in- and output flanges welded to the bottom. With a GRP hull you need flexible seals and fixtures to take the weight of the pipes: there is a considerable difference in expansion/contraction, rigid seals will leak.
Stainless steel could be used because it is light, but the conduction is poor and the expansion factor is very high, copper would be much better but is easily damaged, aluminium suffers from galvanic corrosion.
Thin walled tungsten or titanium tubes would be perfect but make this a very expensive project.

[TeddyDiver]

Originally Posted by Landlubber

Go to Professional Boatbuilder, Dave Gerr wrote a very good article on this subject earlier on this year, you can read it on the site.

Dave's new book (january,2009) inludes also articles published earlier like the keel cooling/dry exhaust... Not yet available here but maybe soon? I preordered my copy allready.

There are simple ways to get around of most expansion etc issues. In a keel cooling tube the easiest is to make an U turn in the tube and put in- and out flanges side to side. Additional fastenings just are "plummer" type allowing all expansion/contrction needed..

[TollyWally]

I've seen plenty of pretty crude keel cooling setups on fish boats in Alaska. They seem quite reliable and trouble free.

[Landlubber]

The copper or other material pipe can be fixed with twin O rings, and expansion does not then affect them

[TeddyDiver]

And it's not a huge temp changes in keel cooling pipe. max from around 0 C to intermedate of the sea water (max 30 C) and cooling fluid (max 90 C) = around 60 C

[MikeJohns]

This seems to crop up regulalry, see also:

Keel cooling

converting from fresh water cooling to keel cooling

cheers

[FAST FRED]

Biggest hassle with KK for us is the water is overcooled , compared to what a radiator system would do.

The solution is an external ( to the engine)thermostat system that mixes the coolant out and in from the KK .

FF