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Boat Forum / Building / July 2007Copper tubing and sea water
I am thinking of using plain old copper tubing (the type you get from Home Depot) to cool the winding section of a a generator by wrapping a few turns of the copper tubing around the casing and then pumping sea water directly around the tubing. Can anyone advise whether this is going to work? Obviously I don't mind if it gets an ugly blue colour inside the tubing however I don't want to be loosing cooling efficiency with time, or worse have the tubing leak. The reason I don't want to use cuprous nickel is that it is much less malleable than standard copper tubing and I would not be able to simply wrap it around the casing. All ideas and comments appreciated. Ian > I am thinking of using plain old copper tubing (the type you get from > Home Depot) to cool the winding section of a a generator by wrapping a [quoted text clipped - 6 lines] > than standard copper tubing and I would not be able to simply wrap it > around the casing. No problems with copper and saltwater; however, doubt you will be able to get good enough heat transfer between copper tubing and generator casing to make it worth the effort. Lew >I am thinking of using plain old copper tubing (the type you get from >Home Depot) to cool the winding section of a a generator by wrapping a [quoted text clipped - 10 lines] > >Ian Certainly the concept is viable as some gen. set alternators are made with water passages built in for sea water cooling and someone advertises a cooler for a marine gear box that is simply a stainless box that bolts against the side of the transmission and has sea water pumped through it. Home made marine air con heat exchangers are often made of plain copper tubing and last quite a while, however they do corrode through eventually. An alternate would be stainless tubing but that would probably be difficult to wrap. I would think that you are going to have to use at least 1/2" tubing to absorb much heat which probably isn't going to be as easy to wrap around the generator as perhaps you envision. Last comment. Are you sure that you need to cool the generator? Bruce in Bangkok (brucepaigeatgmaildotcom)  SignaturePosted via a free Usenet account from http://www.teranews.com Ian, BTDT, go find some cerrobend (sp?) to fill the tubing so it doesn't flatten when you bend it. I do not even vaguely remember the name of the high thermal conductivity epoxy that we used to stick the copper to the generator frame. Matt Colie > I am thinking of using plain old copper tubing (the type you get from > Home Depot) to cool the winding section of a a generator by wrapping a [quoted text clipped - 10 lines] > > Ian > Ian, > BTDT, go find some cerrobend (sp?) to fill the tubing so it doesn't [quoted text clipped - 17 lines] > > > Ian I have used dry beach sand and it works pretty good. Over the years I've seen very little written about fuel economy in boats. If anyone has good data I would like to see it. I am particularly concerned with optimal speeds for planing hulls. Is it in the displacement range? Or on the plane? Does it increase monotonically with decreasing speed? Not in gallons per hour, but in miles per gallon. If one has a twin screw boat, does fuel economy increase or decrease in running only one prop? Is diesel always more economical than gas? And anything else that bears on the problem. Bob Swarts > Over the years I've seen very little written about fuel economy in > boats. If anyone has good data I would like to see it. I am particularly [quoted text clipped - 6 lines] > > Bob Swarts When I sold boats for Bayliner at Olympic Boat Center I was taught that their hull was supposed to adjust itself to the most efficient plane for the amount of throttle given to the prop. Sounded to me like a bunch of sales talk. I have crossed the Gulf of Alaska around 80 times in many types of vessels and have found 8 knots to be the most economical speed to run. I can monitor the day tank and measure gallons per day and nautical miles covered. Diesel is always more economical than gasoline all things being the same. Load, distance, same boat etc. Also, all the new fuel technology is for diesel engines, because diesel engines can run on many different things. Rudolf Diesel even tried to run coal dust, but he had too much trouble metering it and injecting it. The diesel engine can even run on peanut oil. I haven't tried it yet, but as soon as I buy an old diesel car I am going to try it. You can buy vegatable oil from discount grocery stores cheaper than Diesel fuel. I would like to see if it can be mixed! I have heard that just adjusting the pump is the only modification required. >>Over the years I've seen very little written about fuel economy in >>boats. If anyone has good data I would like to see it. I am particularly [quoted text clipped - 25 lines] > than Diesel fuel. I would like to see if it can be mixed! I have heard > that just adjusting the pump is the only modification required. You can run a diesel on a mix of veggie and diesel. My dodge ram runs on a mix of 70% veggie and 30% diesel in the summer. Doesn't work well at any mix if the ambient temp is below 40 deg F. But above that, mixes up to 70 percent work well. I have more than 50K miles on mixes... Signature“TANSTAAFL” ____________________________________________________________________________ "A prudent man foresees the difficulties ahead and prepares for them; The simpleton goes blindly on and suffers the consequences." - Proverbs 22:3 ____________________________________________________________________________ > Over the years I've seen very little written about fuel economy in > boats. If anyone has good data I would like to see it. I am particularly [quoted text clipped - 6 lines] > > Bob Swarts The reason we measure boats in gallons per hour and not miles per hour? Wind and current make miles per hour impractical. With the current against you, the engine can be running at 6000 RPM for an hour and you have only covered two miles. I have seen that in the Inside Passage around the Fraiser River. Too big of a veriable there. RPM's and fuel used can be realistically monitored. Tom, the trouble with using gallons per hour is that it doesn't measure fuel economy. If I burn twice the gallons per hour, but go three times as fast, then burning at the higher rate yields greater economy. I will grant that if you are comparing identical boats at identical speeds then gallons per hour would give the desired result. BS > The reason we measure boats in gallons per hour and not miles per > hour? Wind and current make miles per hour impractical. With the > current against you, the engine can be running at 6000 RPM for an hour > and you have only covered two miles. I have seen that in the Inside > Passage around the Fraiser River. Too big of a veriable there. RPM's > and fuel used can be realistically monitored. The only measure that makes sense is miles per gallon, drift, tide, wind effects excluded, your choice of units.. Calculated against dollers per hour time on vacations aboard (what price freedom?) I calculate time at 10 bucks an hour for me, shopping for bargains, whatever. The guests can do as they please. Terry K > The only measure that makes sense is miles per gallon, drift, tide, > wind effects excluded, your choice of units.. [quoted text clipped - 6 lines] > > Terry K Someone receintly said that as long as gas cost less than designer water nobody was ging to worry about it. Now there's a place in NYC selling water for over $50 a quart. And people are buying it!!! Richard If >one has a twin screw boat, does fuel economy increase or decrease in >running only one prop? > >Bob Swarts Hi Bob, I sail a keeler but last year in my job I was aboard a planing hulled launch powered by two 1250 HP turbo charged MTU diesels, each driving its own propellor. I don't know the physics of it, but I experienced a situation where a single engine used far more diesel than twins. We went at speed (about 45 to 50 knots) over a shallow patch and somehow a stone got sucked into one of the two water intakes, smashing the perspex (later replaced with polycarbonate) cap plate. Unfortunately this was placed directly under the air intake for the turbocharger which sucked the intake water directly into the starboard engine cyclinders. Result - instant stoppage on that engine. It was decided to slowly motor with one engine back to our home base where repairs could more easily be done. We originally had more than sufficient fuel to get back home uinder two engines and then some. We ran out of fuel about two thirds of the way and had to be towed into port. As I said, don't understand why. For my keelboat, I normally calculate useage by the rule of thumb - a tenth of a litre per horsepower per hour. Mine develops 37.5 HP at full revs of about 3,000. According to the fuel usage curve in the supplied manual, the best efficiency is at about 1800 revs which is what I usually run it at - developing a lot less than 37 HP - probably 25 as I use about 2.5 litres per hour at those revs. Hope this helps Peter > Result - instant stoppage on that engine. > [quoted text clipped - 3 lines] >ran out of fuel about two thirds of the way and had to be towed into >port. As I said, don't understand why. For one thing, the off center thrust will push the hull through the water sideways, even with rudder keeping the thing headed in a straight line. Also on plane is more effecient than going too fast at displacement speeds. Casady Stepped hydroplanes? Aeronautical work on flying boats and multi- stepped hulls suggest power economy concerns at takeoff speed and some intermediate speed transitions. The hull speed equation is only one indicator. Hull shape is important. A displacement hull will likely go faster, further and cheaper than a planing hull at certain speed / power combinations. it's finesse, I think, as opposed to fine-nese, though hobie owners report incredible speeds with knife shaped hulls. It's all about pushing an equal mass of water aside while climbing on top of it before it can move. It's delta-vee, rocket science versus frictional area, versus disturbances in the water (wakes) left behind by hurried boaters. Think about a nice sailing boat bumkin sliding down a pushing wave as opposed to a water sucking vacuum behind a square transom. It costs gas to keep a hole in the water charmed for a long time. Include ball bearings made of air in there, and you are coming to grips with most of the problem. The transition to wing in ram air ground effect is particularly interesting, hovercraft like. I'd like to see exhaust gas used as friction reduction near the planing surface of a waterfoil wing almost airborne, almost cavitating, in ground effect. A water jet intake at the front could effect certain things, like elimination of wake in a steady speed submarine. Would leaving a bubbly, cavitated wake be more stealthy to a satellite looking for large area reflective patterns on clear days? Take a look at power / weight / speed curves with reference across all hull forms at the surface. Terry K > I am thinking of using plain old copper tubing (the type you get from > Home Depot) to cool the winding section of a a generator by wrapping a [quoted text clipped - 10 lines] > > Ian A German fellow from WW2 (NAZI) showed me a trick that worked fairly well for me. He pinched off one end of the copper tubing and filled the soft copper with sand. Then pinched off the other end. Did all the bending, then cut the ends that were pinched off with a tubing cutter. Not one kink anywhere! No flattened tubing no matter how I twisted and bent it. Drained the dry sand back out after bending. I had to twirl it around, but I could have just blown it out with an air hose. Stick with me Ian, You will be wearing rocks as big as diamonds. My Dad used to say that. |
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