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

ian wrote:
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

On Jun 2, 6:07 pm, Matt Colie wrote:
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

ian wrote:
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 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

On Jun 21, 7:24 am, R Swarts wrote:
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

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.

tomdownard wrote:

On Jun 21, 7:24 am, R Swarts wrote:

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


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.


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...

--
“TANSTAAFL”

__________________________________________________ __________________________

"A prudent man foresees the difficulties ahead and prepares for them;
The simpleton goes blindly on and suffers the consequences." - Proverbs 22:3
__________________________________________________ __________________________

On Jun 21, 7:24 am, R Swarts wrote:
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

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


tomdownard wrote:

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

Terry K wrote:
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


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

On Thu, 21 Jun 2007 07:24:07 -0700, R Swarts
wrote:

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