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Not that there's already a shortage of things to do around here, but because I think most engineers got down on their knees to get their degrees, I'm always trying to figger out better ways to do things. Every boat has problem areas, and one place I hear about all the time is the raw water heat exchanger circuit. It's a bad concept IMO, and far, far more likely to give trouble than the freshwater part of the system.
Now given that (at least in this part of the world) we sail in damned cold water, water that is very reactive and tends to eat stuff, why are we sucking it aboard, running it through our trannys, engine and exhausts?
I'm wondering about taking the coolant from the freshwater circuit and running it through a section of looped hose epoxied against the inner hull. Glass is a reasonable thermal conductor and the water is maybe 8-9 degrees C, so the big question would be the surface area needed to conduct away heat to keep it below the boiling point.
Basically use the hull as a heat exchanger.
The thermal capacity of water is quite high, so I don't think you would need an outrageous length of hose.
I need to do some research on the surface area required, and the effects of heat on fibreglass. Anyone ever try something like this?
Sorry, but it won't work. I'm not sure which would happen first, but you would either ignite your fibreglass or toast your engine. The fibreglass hull will not adequately conduct the heat out of the system no matter how cold the water is.
What you COULD do, and many engines particularly those on work-boats have been configured this way, is run the closed coolant loop OUTSIDE the hull and create what is called a "keel-cooler". They work extremely well, but most sailors find the additional drag unacceptable (as opposed to motorboaters that are always under mechanical propulsion.)
I commend you for thinking outside the box. However, as imperfect as the heat exchanger may be, it's not so bad either.
Sorry, but it won't work. I'm not sure which would happen first, but you would either ignite your fibreglass or toast your engine. The fibreglass hull will not adequately conduct the heat out of the system no matter how cold the water is.
What you COULD do, and many engines particularly those on work-boats have been configured this way, is run the closed coolant loop OUTSIDE the hull and create what is called a "keel-cooler". They work extremely well, but most sailors find the additional drag unacceptable (as opposed to motorboaters that are always under mechanical propulsion.)
I commend you for thinking outside the box. However, as imperfect as the heat exchanger may be, it's not so bad either.
Hmm... you'd really want a better heat exchanger surface than fiberglass. Of course, if you ever had to motor in warmer waters, you'd be screwed. There is a thread on heat exchangers right now, which you might want to read.
I like your thinking, Hoffalives. Damn the torpedos, keep at it. If not this one, another. Others are doing it, and making a good buck at it as well.
Look at the gadget that keeps you from having to take the whole damn water pump bolts out when you want to change the impeller. I know, modest in comparison to your proposed challenge, but innovative nonetheless. Or the refridgeration cooling loop that coils around the galley through-hole, using the up-and-down of the boat to circulate cool water around the coil as opposed to consuming power with an auxiliary raw water pump to do the same. I'm sure you've seen that in the back of CW or similar.
Now, some advice if you're willing to take it, explore the edges of your ideas. Step away from the raw-water circuit issue per se, and look at the solution - cold water all around you, moving, even when the boat's at rest, moving even faster when under way...what else could that do for you? I don't know the answer, but the approach is worth exploring - that is, ENGINEER IMAGINATION. Take the realities around you, benevolet or malevolent and exploit them.
Ok, it's late, enough L. Ron Hubbard impersonation for today.
Fair winds.
How about to reduce the drag of a keel-cooler, have it mounted in the lead keel? Its not an idea that would be retrofitted to an older boat, but say on a new boat have the cooling pipes in the keel when its molded. Ive wondered about this myself.
Realy not that bad of an Idea for a sail boat if you put the cooling circuit in the keel and not in the hull. a lead keel with a some sort of compatable metal
cooling grid cast into it would be a good thing. No drag like a conventional keel cooler. and would get the cooler into deeper water where its always colder.
put in a condensing circuit and you have a better refrigeration or A/C.
Maybe better to cast the keel out of steele and hang some lead on it.
I thought about the keel cooler thing but didn't want those holes in the hull. I did some quick checking, and the k-value or thermal conductivity of GRP is about 1/2 that of water, which really isn't that bad (and a long way from being an insulator). The hull of the boat is in intimate contact with an enormous heat sink. It CAN be done (and there are high heat transfer epoxy resins out there (ie. TIGA R-915, K=1.46, H2O=.5 ). The issue is how big of a heat diffuser you would need to sufficiently conduct away the heat. You could build a diffusing grid on the inside of the boat using the above epoxy and glass.
The temp of the cooling water is below the boiling temp of water, waaay below any ignition temperature.
As for the amazing sail we had, it was only Sidney to Victoria, which is about 5 hrs. You couldn't ask for a better sail, and it was so good to pull into the harbor as well, seeing the lights of downtown reflected in the water.
I thought about the keel cooler thing but didn't want those holes in the hull. I did some quick checking, and the k-value or thermal conductivity of GRP is about 1/2 that of water, which really isn't that bad (and a long way from being an insulator). The hull of the boat is in intimate contact with an enormous heat sink. It CAN be done (and there are high heat transfer epoxy resins out there (ie. TIGA R-915, K=1.46, H2O=.5 ). The issue is how big of a heat diffuser you would need to sufficiently conduct away the heat. You could build a diffusing grid on the inside of the boat using the above epoxy and glass.
The temp of the cooling water is below the boiling temp of water, waaay below any ignition temperature.
Even if the K-Value of GRP is 1/2 that of water, the volume of water being pushed through the heat exchanger as compared to the surface area of GRP in contact with the closed loop would make the delta between the respective abilities of these systems to cool exponential. Your fibreglass may be transferring some heat into the water through the exterior surface of the hull (and also quite a bit of heat into the INTERIOR of the boat through the air), but it is not FLOWING over the closed cooling loop like the raw water does.
Some of the other variations on the keel-cooler are interesting and I think they've all been tried with varying degrees of success. Usually what the workboats do is simply run a copper pipe longitudinally outside the hull, parallel to the keel, for a run of about six or eight feet. You also have to adapt the system to a dry exhaust.
Bolger and others have taken it even further in certain designs and eliminated even the keel cooler by going with vented air and oil-cooled engines with dry exhaust.
I worked on a house- solar\conductive heat. It had a grid of something like abs plstic set in the concrete foundation that kept the floor warm and warm air went up through the house. the trick on it was alot of very small tubes running long distances with low preasure and low flow.
It will work Hoffa but the one off, set up, would probably cost more than a new heeat exchanger and a new water pump X 5 .
the problem on the boats I worked on that were keel cooled were that the cooler was generally the stacked plate variety and barnicals and alge growth on the plates was what would kill you. It has to be a cooler that is inside the hull or keel to be maintanace free. on a steele or aluminum hull the cooler could be very efficiant. you would have to figure the surface area of the heat exchanger and the amount of cooling efficiancy of the raw water pump flow. You would have to embed a grid into the hull the insulating properties of the hull and water and hull and air may heat the air in your hull up more than the water around it depending on ambiante temps. heat generaly rises.
If you are so concerned about the effects of raw water, why not just get rid of the heat exchanger, raw water pump entirely and go a standard automotive radiator? You would need to place it somewhere and install a fan to blow air through it, but you get rid of a water pump and extra plumbing. It works fine for cars, there is no reason why it would not work on a boat.
If you are so concerned about the effects of raw water, why not just get rid of the heat exchanger, raw water pump entirely and go a standard automotive radiator? You would need to place it somewhere and install a fan to blow air through it, but you get rid of a water pump and extra plumbing. It works fine for cars, there is no reason why it would not work on a boat.
I've actually seen this done... a monstrous 65' steel ketch built from one of Roberts' plans. Unfortunately the boat burnt up before the system was really put to the test.
I'd suspect that the space required is the major negative - fab noise another and heating up of the interior, while welcome at certain times and in certain climes, not so much at other times.
The problem is the collosal amount of heat to be rejected.
A 35 hp motor operating at (say) 40% efficiency will be rejecting about 65 kW into the cabin.
You will just cook the crew.
It would be possible to make a big cowl that ducted the heated air out and into the air, but it would mean a big through-deck, and it would be a sinking risk in heavy weather.
If I were going to go the route of the cowl, I would have an air-cooled motor, and a big duct. The super-hot exhaust manifold would be the next problem... it would get seriously hot.
Air cooled motors are noisy too. I know Magirus Deutz make a few good ones. Lister used to, and probably still do.
Don't mock the "SailFan"! Just because you're stuck in your ways doesn't mean the rest of us have to be. I'm going to be posting an update soon on the SailFan experiment and when I do I'm sure you wll be amazed at the progress of this ingenious invention....
I was just rambling... And I'm with you on the corrosive sea-water -- the heater exchanger should last decades with proper use -- not bad service considering. Perhaps I'm in the minority, but I've always felt it was an elegantly simple solution.
Hey, I'm glad TrueBlue mentioned it, becuase now it occurs to me that maybe we could direct the thrust from the SailFans to also blow air on the radiator? This could be even more revolutionary than any of us realized...
You know guys, I know I'm going to catch hell on this one, But..ITS A SAILBOAT..With a note on SAIL... If you dont like the way the motor works, put the sails up.....and if you find you're spending more time motoring and less time sailing, maybe its time to go over to the DARK SIDE.......
I don't know where you live, but in the PN, we can get weeks and weeks of no/little wind in the summer. Often the best weather to be out on the water it's very still. Wind or not I'm gonna be out there. I would obviously prefer to sail, but sometimes the wind doesn't co-operate. We also have to deal with tons of shoals and reefs, very high currents, and crazy tides, and I'm glad I've got the iron jenny as backup.
Sometimes you just can't count on nature.
I dunno about your engine, but the westerbeke bolt-on components have a less than stellar rep. It is a basic system and you would think it would be reliable, but I've had to rebuild my jabsco saltwater pump 3X since I bought this crazy boat. And there have been several posts on the CSOA website with people having problems with the heat exchanger system.
I think it can be simpler, that's all. I just wonder if anyone has tried conducting the excess heat through the hull. Obviously a steel boat would be better to test this, but I don't think it's a requirement. When I get some time I would like to look at the numbers further.
Very well said. All we need our OB for is getting in and out of the marina and that's because the marina is on a large river. Next year this time we will be on a 6 month cruise in the Bahamas and engine time should be about 3 hrs for the trip.
I wonder if you had a steel hulled boat and then ran the hot water through copper coils that were fixed to the inside of the hull.....I suppose the problem would be how to keep the maximum amount of surface area of the coils fixed to the hull.
I wonder if you had a steel hulled boat and then ran the hot water through copper coils that were fixed to the inside of the hull.....I suppose the problem would be how to keep the maximum amount of surface area of the coils fixed to the hull.
I've seen motor boats with this, not planing hulls, they use single straight pipes about 10 ft long, aligned with the flow, it works. Also some steel sailing boats use no raw water inlet, the cooling water is circulated through a part of the integral keel. I suppose a GRP boat could do the same trick. Giu could have his shark modified to have pipes running down inside the fin and back.
That's it Tomaz, a variable geometry engine cooling keel. The hydrodynamic equivalent to the solar stick.
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