Useless propeller
 

After some use I've decided those two bladed folding props are useless in
any rough weather. I'm getting rid of mine and putting on a four bladed prop
with a gear reduction.

Bob Crantz

Useless propeller
 

Some Thing Is missing in your sailing.;---? Why in the hell are you
worrying about a Prop in Bad Weather? You have more than enough Sail
Power and if reefed properly, a hell of a lot smoother ride.

My 2 Blade, Folder would stay open at 200 RPM but cavitation did worry
me. I don't think a 4 Blade fixed is going to help cavitation.




http://community.webtv.net/tassail/ThomPage

Useless propeller
 

The gear reduction reduces the propeller RPM and reduces cavitation.

A nice big 4 blade does the job.

One should worry the most about propellers in bad weather.

Useless propeller
 

BC,

Cavitation is caused be the Prop not having enough water in Choppy Sea.
Reduction Gearing has nothing to do with it.

You're a Pretty Poor sailer if you are depending on a small Aux, Engine
to replace Sails in a Seaway. Even Trawlers hoist a steadying Sail in a
Seaway to improve ride quality




http://community.webtv.net/tassail/ThomPage

Useless propeller
 

Thom Stewart wrote:
BC,

Cavitation is caused be the Prop not having enough water in Choppy Sea.

Cavitation is caused by the prop spinning too fast for the forward
motion of the vessel.

Reduction Gearing has nothing to do with it.

Reduction gearing has EVERYTHING to do with it.

PDW

Useless propeller
 

"Peter" wrote in message
oups.com...


Cavitation is caused by the prop spinning too fast for the forward
motion of the vessel.

Cavitation is caused by water not being able to move fast enough to fill low
pressure spaces created around such things as a propeller. A spinning disc
has no forward speed regardless of RPM yet there is no cavitation. A
propeller is a rotating wing and the low pressure side causes the water to
"boil", hencce the creation of cavitation. Higher RPM gives higher
tangentail blade speeds and greater pressure differential between the faces
of the prop.

Useless propeller
 

"Peter" wrote
Cavitation is caused by the prop spinning too fast for the forward
motion of the vessel.


Gilligan wrote:
Cavitation is caused by water not being able to move fast enough to fill low
pressure spaces created around such things as a propeller.

Which is caused by... ?
You're both right. Peter is talking about the cause on a
macro scale.

... A spinning disc
has no forward speed regardless of RPM yet there is no cavitation. A
propeller is a rotating wing and the low pressure side causes the water to
"boil", hencce the creation of cavitation.

But what makes the water boil? Increased temps due to
friction? Tiny devil-spirits waving their pitchforks?


.... Higher RPM gives higher
tangentail blade speeds and greater pressure differential between the faces
of the prop.


Somewhat right, tip speed above a certain linear velocity
will cause cavitation no matter the dP, and if the dP gets
high enough the tip speed matters less.

You could also mention the dread voodoo curse "viscous
shear" which means that somebody is trying to force those
lazy water molecules to move faster than they are willing.

Fluid flow does a lot of things counter-intuitive to people
familiar with normal physics. One of my favorite engineering
profs used to say that fluid molecules are like basketballs
smeared with syrup, which helps intuit the behavior.

DSK

Useless propeller
 

"DSK" wrote in message
...

But what makes the water boil? Increased temps due to friction? Tiny
devil-spirits waving their pitchforks?


Lower pressure.



.... Higher RPM gives higher tangentail blade speeds and greater pressure
differential between the faces of the prop.

Somewhat right, tip speed above a certain linear velocity will cause
cavitation no matter the dP,

Then it would be the void (low pressure) behind the propeller. There is
still cavitation due to drag, which would occur with a spinning disc.


You could also mention the dread voodoo curse "viscous shear" which means
that somebody is trying to force those lazy water molecules to move faster
than they are willing



Fluid flow does a lot of things counter-intuitive to people familiar with
normal physics. One of my favorite engineering profs used to say that
fluid molecules are like basketballs smeared with syrup, which helps
intuit the behavior.

DSK

Useless propeller
 

"Gilligan" wrote in message . ..
|
| "DSK" wrote in message
| ...
|
| But what makes the water boil? Increased temps due to friction? Tiny
| devil-spirits waving their pitchforks?
|
|
| Lower pressure.

Hee hee! Lower pressure never makes any liquid boil. It makes it vaporize.
Boil is a subjective term. It only refers to that temperature at atmospheric
pressure at which a liquid vaporizes. Some engineer you are Mr. Gilligan!

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

http://en.wikipedia.org/wiki/Boiling



Boiling is the rapid vaporization of a liquid, which typically occurs when a
liquid is heated to a temperature such that its vapor pressure is above that
of the surroundings, such as air pressure. Thus, a liquid may also boil when
the pressure of the surrounding atmosphere is sufficiently reduced, such as
the use of a vacuum pump or at high altitudes. Boiling occurs in three
characteristic stages, which are nucleate, transition and film boiling.
These stages generally take place from low to high surface temperatures,
respectively.

Nucleate boiling is characterized by the incipience and growth of bubbles on
a heated surface, which rise from discrete points on a surface, whose
temperature is only slightly above the liquid’s saturation temperature. In
general, the number of nucleation sites are increased by an increasing
surface temperature. An irregular surface of the boiling vessel (i.e.
increased surface roughness) can create additional nucleation sites, while
an exceptionally smooth surface (such as glass) lends itself to
superheating.

When the surface temperature reaches a maximum value, the critical
superheat, vapor begins to form faster than liquid can reach the surface.
Thus, the heated surface suddenly becomes covered with a vapor layer.
Because of the vapor layer’s lower thermal conductivity, this vapor layer
insulates the surface. This condition of a vapor film insulating the surface
from the liquid characterizes film boiling.

Transition boiling may be defined as the unstable boiling, which occurs at
surface temperatures between the maximum attainable in nucleate and the
minimum attainable in film boiling.

Useless propeller
 

"Gilligan" wrote in message . ..
| http://en.wikipedia.org/wiki/Boiling
|
|
|
| Boiling is the rapid vaporization of a liquid, which typically occurs when a
| liquid is heated to a temperature such that its vapor pressure is above that
| of the surroundings, such as air pressure. Thus, a liquid may also boil when
| the pressure of the surrounding atmosphere is sufficiently reduced, such as
| the use of a vacuum pump or at high altitudes. Boiling occurs in three
| characteristic stages, which are nucleate, transition and film boiling.
| These stages generally take place from low to high surface temperatures,
| respectively.
|
| Nucleate boiling is characterized by the incipience and growth of bubbles on
| a heated surface, which rise from discrete points on a surface, whose
| temperature is only slightly above the liquid’s saturation temperature. In
| general, the number of nucleation sites are increased by an increasing
| surface temperature. An irregular surface of the boiling vessel (i.e.
| increased surface roughness) can create additional nucleation sites, while
| an exceptionally smooth surface (such as glass) lends itself to
| superheating.
|
| When the surface temperature reaches a maximum value, the critical
| superheat, vapor begins to form faster than liquid can reach the surface.
| Thus, the heated surface suddenly becomes covered with a vapor layer.
| Because of the vapor layer’s lower thermal conductivity, this vapor layer
| insulates the surface. This condition of a vapor film insulating the surface
| from the liquid characterizes film boiling.
|
| Transition boiling may be defined as the unstable boiling, which occurs at
| surface temperatures between the maximum attainable in nucleate and the
| minimum attainable in film boiling.
|
|

Good info but mostly obfuscation to keeping from saying. "Oops, I
was wrong.

The facts of the matter that the verb boil means to heat to a temperature
at which a liquid vaporizes. I'm saying there is not enough heating going
on in a cavitating prop to vaporize water. Thus to say it boils is to speak
in error.

The fact of the matter is you used the word boil when you should have
corrected DSK and used vaporized instead. It's a pressure thing and
not a temperature thing,

Paladin


--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

"Gilligan" wrote in message . ..
| http://en.wikipedia.org/wiki/Boiling
|
|
|
| Boiling is the rapid vaporization of a liquid, which typically occurs when a
| liquid is heated to a temperature such that its vapor pressure is above that
| of the surroundings, such as air pressure. Thus, a liquid may also boil when
| the pressure of the surrounding atmosphere is sufficiently reduced, such as
| the use of a vacuum pump or at high altitudes. Boiling occurs in three
| characteristic stages, which are nucleate, transition and film boiling.
| These stages generally take place from low to high surface temperatures,
| respectively.
|
| Nucleate boiling is characterized by the incipience and growth of bubbles on
| a heated surface, which rise from discrete points on a surface, whose
| temperature is only slightly above the liquid’s saturation temperature. In
| general, the number of nucleation sites are increased by an increasing
| surface temperature. An irregular surface of the boiling vessel (i.e.
| increased surface roughness) can create additional nucleation sites, while
| an exceptionally smooth surface (such as glass) lends itself to
| superheating.
|
| When the surface temperature reaches a maximum value, the critical
| superheat, vapor begins to form faster than liquid can reach the surface.
| Thus, the heated surface suddenly becomes covered with a vapor layer.
| Because of the vapor layer’s lower thermal conductivity, this vapor layer
| insulates the surface. This condition of a vapor film insulating the surface
| from the liquid characterizes film boiling.
|
| Transition boiling may be defined as the unstable boiling, which occurs at
| surface temperatures between the maximum attainable in nucleate and the
| minimum attainable in film boiling.
|
|

Good info but mostly obfuscation to keeping from saying. "Oops, I
was wrong.

The facts of the matter that the verb boil means to heat to a temperature
at which a liquid vaporizes. I'm saying there is not enough heating going
on in a cavitating prop to vaporize water. Thus to say it boils is to speak
in error.

The fact of the matter is you used the word boil when you should have
corrected DSK and used vaporized instead. It's a pressure thing and
not a temperature thing,

Paladin


--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

Oh Bull **** Pete

You posted; "Reduction gearing has EVERYTHING to do with it."

It seems you've elected to ignore, Prop Pitch, Prop Size, and the Medium
it is operating in. You have also neglected to recognize throttle
control




http://community.webtv.net/tassail/ThomPage

Useless propeller
 

http://encarta.msn.com/media_4615415...for_Water.html

Useless propeller
 

"Gilligan" wrote in message . ..
|
| http://encarta.msn.com/media_4615415...for_Water.html
|
|
|

The diagram proves my point. Since there is no significant temperature
change involved with a propeller but there is a significant pressure change
then the water does not vaporize because it boils. Rather it vaporizes because
of the pressure change.

I'm just so brilliant. You can't even manage to misdirect me.

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

"Thom Stewart" wrote in message ...
| Oh Bull **** Pete
|
| You posted; "Reduction gearing has EVERYTHING to do with it."
|
| It seems you've elected to ignore, Prop Pitch, Prop Size, and the Medium
| it is operating in. You have also neglected to recognize throttle
| control
|

Other things being equal a larger prop with more pitch and lower
gearing is more efficient and delivers more drive per BTU of fuel
used. A one bladed prop would be most efficient but there is
a problem balancing such a thing. Three-bladed props seem to be
a very good compromise for powering sailing yachts with their
inherent slow velocity through the water.

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

"Paladin" noneofyourbusiness.www wrote in message
...

"Gilligan" wrote in message
. ..
|
| http://encarta.msn.com/media_4615415...for_Water.html
|
|
|

The diagram proves my point. Since there is no significant temperature
change involved with a propeller but there is a significant pressure
change
then the water does not vaporize because it boils. Rather it vaporizes
because
of the pressure change.

I'm just so brilliant. You can't even manage to misdirect me.


I can't misdirect you, but I can set you straight.

When water boils, as in your kettle, those "bubbles" are water vapor
suspended in the liquid water.

Cavitation is caused by the propeller slipping on water vapor suspended in
the liquid water.

Would it then be reasonable to say that cavitation is caused by water
boiling?

OR

Cavitation can only happen in your tea kettle?

Useless propeller
 

"Gilligan" wrote in message . ..
|
| "Paladin" noneofyourbusiness.www wrote in message
| ...
|
| "Gilligan" wrote in message
| . ..
| |
| | http://encarta.msn.com/media_4615415...for_Water.html
| |
| |
| |
|
| The diagram proves my point. Since there is no significant temperature
| change involved with a propeller but there is a significant pressure
| change
| then the water does not vaporize because it boils. Rather it vaporizes
| because
| of the pressure change.
|
| I'm just so brilliant. You can't even manage to misdirect me.
|
|
| I can't misdirect you, but I can set you straight.

You've done an inadequate job of it so far...

| When water boils, as in your kettle, those "bubbles" are water vapor
| suspended in the liquid water.

Agreed. But, suspended is a poor word choice. I prefer to call it
water vapor displacing the liquid water.

| Cavitation is caused by the propeller slipping on water vapor suspended in
| the liquid water.

Quaintly envisioned. Highly inadequate. Cavitation is a descriptive term used
to describe the vaporization of the water near the low pressure side of the
propeller blades resulting in over-revving of the engine. The over-revving of
the engine is caused by the prop losing contact with the water.


| Would it then be reasonable to say that cavitation is caused by water
| boiling?

Not in the case of a boat unless it was in a giant pot of boiling water
on the stove.

| OR
|
| Cavitation can only happen in your tea kettle?

Cavitation could very well be caused by operating a prop in boiling
water but the prop doesn't cause the water to boil. The fire under
the tea kettle is doing that job.

Now, who's straightening out whom?

Paladin


--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

Thom Stewart wrote:
Oh Bull **** Pete

You posted; "Reduction gearing has EVERYTHING to do with it."

It seems you've elected to ignore, Prop Pitch, Prop Size, and the Medium
it is operating in. You have also neglected to recognize throttle
control

It was just as valid as your response that reduction gearing has
NOTHING to do with it.

Try moving a 40,000 lb displacement boat with a 225HP 2 stroke outboard
running at 8000 rpm. Then try the same thing using a 225HP diesel
running at 1800 rpm thru a 3:1 reduction box.

You oversimplified and are now trying to dig yourself out.

PDW

Useless propeller
 

"Gilligan" wrote in message
. ..
http://en.wikipedia.org/wiki/Boiling



Boiling is the rapid vaporization of a liquid, which typically occurs when
a liquid is heated to a temperature such that its vapor pressure is above
that of the surroundings, such as air pressure. Thus, a liquid may also
boil when the pressure of the surrounding atmosphere is sufficiently
reduced, such as the use of a vacuum pump or at high altitudes. Boiling
occurs in three characteristic stages, which are nucleate, transition and
film boiling. These stages generally take place from low to high surface
temperatures, respectively.

Nucleate boiling is characterized by the incipience and growth of bubbles
on a heated surface, which rise from discrete points on a surface, whose
temperature is only slightly above the liquid's saturation temperature. In
general, the number of nucleation sites are increased by an increasing
surface temperature. An irregular surface of the boiling vessel (i.e.
increased surface roughness) can create additional nucleation sites, while
an exceptionally smooth surface (such as glass) lends itself to
superheating.

When the surface temperature reaches a maximum value, the critical
superheat, vapor begins to form faster than liquid can reach the surface.
Thus, the heated surface suddenly becomes covered with a vapor layer.
Because of the vapor layer's lower thermal conductivity, this vapor layer
insulates the surface. This condition of a vapor film insulating the
surface from the liquid characterizes film boiling.

Transition boiling may be defined as the unstable boiling, which occurs at
surface temperatures between the maximum attainable in nucleate and the
minimum attainable in film boiling.

The propeller is the thing that makes the boat go, innit?

Max

Useless propeller
 

"Paladin" noneofyourbusiness.www wrote in message
...

"Gilligan" wrote in message
. ..
|
| "Paladin" noneofyourbusiness.www wrote in message
| ...
|
| "Gilligan" wrote in message
| . ..
| |
| | http://encarta.msn.com/media_4615415...for_Water.html
| |
| |
| |
|
| The diagram proves my point. Since there is no significant temperature
| change involved with a propeller but there is a significant pressure
| change
| then the water does not vaporize because it boils. Rather it vaporizes
| because
| of the pressure change.
|
| I'm just so brilliant. You can't even manage to misdirect me.
|
|
| I can't misdirect you, but I can set you straight.

You've done an inadequate job of it so far...

| When water boils, as in your kettle, those "bubbles" are water vapor
| suspended in the liquid water.

Agreed. But, suspended is a poor word choice. I prefer to call it
water vapor displacing the liquid water.

| Cavitation is caused by the propeller slipping on water vapor suspended
in
| the liquid water.

Quaintly envisioned. Highly inadequate. Cavitation is a descriptive term
used
to describe the vaporization of the water near the low pressure side of
the
propeller blades resulting in over-revving of the engine. The over-revving
of
the engine is caused by the prop losing contact with the water.


| Would it then be reasonable to say that cavitation is caused by water
| boiling?

Not in the case of a boat unless it was in a giant pot of boiling water
on the stove.

| OR
|
| Cavitation can only happen in your tea kettle?

Cavitation could very well be caused by operating a prop in boiling
water but the prop doesn't cause the water to boil. The fire under
the tea kettle is doing that job.

Now, who's straightening out whom?

Suppose I have water in a beaker and place it in a bell jar. The air in the
bell jar is pumped out, lowering the pressure. Eventually the water begins
to boil.

Where is the heat source causing it to boil?

Useless propeller
 

OK Group,

What happened to the original statement; "Useless propeller" Let's get
back to that! Why is a Two Blade Folding Prop a Useless propeller and a
Four Blade fixed going to work better in rough, choppy sea?




http://community.webtv.net/tassail/ThomPage

Useless propeller
 

"Gilligan" wrote in message ...
|
| "Paladin" noneofyourbusiness.www wrote in message
| ...
|
| "Gilligan" wrote in message
| . ..
| |
| | "Paladin" noneofyourbusiness.www wrote in message
| | ...
| |
| | "Gilligan" wrote in message
| | . ..
| | |
| | | http://encarta.msn.com/media_4615415...for_Water.html
| | |
| | |
| | |
| |
| | The diagram proves my point. Since there is no significant temperature
| | change involved with a propeller but there is a significant pressure
| | change
| | then the water does not vaporize because it boils. Rather it vaporizes
| | because
| | of the pressure change.
| |
| | I'm just so brilliant. You can't even manage to misdirect me.
| |
| |
| | I can't misdirect you, but I can set you straight.
|
| You've done an inadequate job of it so far...
|
| | When water boils, as in your kettle, those "bubbles" are water vapor
| | suspended in the liquid water.
|
| Agreed. But, suspended is a poor word choice. I prefer to call it
| water vapor displacing the liquid water.
|
| | Cavitation is caused by the propeller slipping on water vapor suspended
| in
| | the liquid water.
|
| Quaintly envisioned. Highly inadequate. Cavitation is a descriptive term
| used
| to describe the vaporization of the water near the low pressure side of
| the
| propeller blades resulting in over-revving of the engine. The over-revving
| of
| the engine is caused by the prop losing contact with the water.
|
|
| | Would it then be reasonable to say that cavitation is caused by water
| | boiling?
|
| Not in the case of a boat unless it was in a giant pot of boiling water
| on the stove.
|
| | OR
| |
| | Cavitation can only happen in your tea kettle?
|
| Cavitation could very well be caused by operating a prop in boiling
| water but the prop doesn't cause the water to boil. The fire under
| the tea kettle is doing that job.
|
| Now, who's straightening out whom?
|
| Suppose I have water in a beaker and place it in a bell jar. The air in the
| bell jar is pumped out, lowering the pressure. Eventually the water begins
| to boil.
|
| Where is the heat source causing it to boil?

There is no heat source in that case but the water
is not boiling.

Go to a dictionary and look up the definition of boil.
You will note that it mentions application of heat.

Lowering pressure does not add heat. Therefore, to
use the word boil is incorrect to describe the bubbling
action lowering the pressure causes.

Water plus heat = boil
Water minus pressure = vaporization

Your thinking is sound; it's your use of the verb 'boil'
that's faulty and it muddles the issue. People like
Old Tom quickly get lost. (or should I say "more lost?")

Get it?


Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

"Peter" wrote in message oups.com...
|
| Thom Stewart wrote:
| Oh Bull **** Pete
|
| You posted; "Reduction gearing has EVERYTHING to do with it."
|
| It seems you've elected to ignore, Prop Pitch, Prop Size, and the Medium
| it is operating in. You have also neglected to recognize throttle
| control
|
| It was just as valid as your response that reduction gearing has
| NOTHING to do with it.
|
| Try moving a 40,000 lb displacement boat with a 225HP 2 stroke outboard
| running at 8000 rpm. Then try the same thing using a 225HP diesel
| running at 1800 rpm thru a 3:1 reduction box.
|
| You oversimplified and are now trying to dig yourself out.
|
| PDW
|


Precisely so...

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

Paladin wrote:
There is no heat source in that case but the water
is not boiling.

Go to a dictionary and look up the definition of boil.
You will note that it mentions application of heat.


Well, here's your problem... you seem to think that a
dictionary is the ultimate scientific reference.

I suggest a high school physics text... don't strain
yourself trying to read it, just look at the pictures!

DSK

Useless propeller
 

Thom Stewart wrote:

OK Group,

What happened to the original statement; "Useless propeller" Let's get
back to that! Why is a Two Blade Folding Prop a Useless propeller and a
Four Blade fixed going to work better in rough, choppy sea?


Well, a two-blade folder isn't really useless, it has it's
own uses and unfortunately that means it will not do as good
a job driving the boat under less-optimal conditions. OTOH
it will allow the boat to sail much better.

The problem with most folding props is
1- they are expensive, leading most people to buy the size
smaller than they really need
2- the hubs often develop some play, allowing the blades to
twist unfavorably and lose power

These two things are why they don't work well in reverse and
don't work well in choppy water.

I have a little experience with the Luke three blade
feathering prop, which is expensive but a very practical
alternative.

A good friend of mine had a small keelboat with a big
2-blade folder... the boat was very slow under power. This
was the opposite case of above, the previous owner had gone
for "conspicuous consumption" and outfitted the boat very
expensively but not efficiently. Among other things, the
prop was pitched for much higher RPM. When we were motoring
out to a race one time, we discussed the issue and since
thenengine reached full RPM easily, there was no reason not
to adjust the pitch. After two successive adjustments the
boat went almost 2 knots faster under power. It also motored
quite well in rough water... certainly much better than the
same type boat with an outboard.

Fresh Breezes- Doug King

Useless propeller
 

"DSK" wrote in message .. .
| Paladin wrote:
| There is no heat source in that case but the water
| is not boiling.
|
| Go to a dictionary and look up the definition of boil.
| You will note that it mentions application of heat.
|
|
| Well, here's your problem... you seem to think that a
| dictionary is the ultimate scientific reference.
|
| I suggest a high school physics text... don't strain
| yourself trying to read it, just look at the pictures!
|
| DSK
|

The dictionary is the ultimate language reference and since things are discussed using
language the discussion must share common ground of accepting definitions of words.
Much confusion can be avoided if common ground is adhered to by those discussing even
scientific concepts. Ideally, scientific concepts need to be discussed using math as
there is agreement upon math entities. But since you have shown that you cannot even
grasp language it demonstrates how futile it would be to use math to discuss this
word "boil".

Nobody invited you into this discussion with your ignorant statements. Butt out with your
unwanted butting in...

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

Pal(?)

Once again you've neglected to consider the drag created when not using
the engine.

Please look at the Subject heading. Then try to remember what kind of
Prop was being referred two AND in what kind of sea condition were being
described.

You can "Color me Gone" with this reply.




http://community.webtv.net/tassail/ThomPage

Useless propeller
 

The propeller does boil the water. It is a scientific fact and I shall offer
irrefutable proof:

http://www.brooklyn.cuny.edu/bc/ahp/MBG/MBG4/Joule.html

Quotes:

"In the following years he took to measuring the amount of heat generated by
every mechanical process he could think of. He enclosed wooden paddles
inside an insulated container and used a falling weight to turn a shaft and
churn the paddles. Friction caused the water in the container to heat up,
and Joule measured the heat change. From this the work done could be
compared with the amount of heat that had been produced.

By 1843 he was ready to publish. Called the mechanical equivalent of heat,
this is value for the amount of work required to produce a unit of heat, and
is calculated as 41,800,000 ergs. (One erg is the work done in moving a one
gram mass through a one centimeter distance)."



So, as one can plainly see that in the mid-1800's it was recognized that the
churning of propellers heat the water. In the case of the cavitating
propeller, the slippage is so great that the energy that would normally go
into propelling a great ship forward goes, instead, into raising the caloric
content of the fluid medium surrounding said propeller causing boiling and
cavitation.

Hence, the propeller boils the water, causing cavitation.

My tea kettle has a propeller in it and boils water quite quickly with no
application of heat.

Useless propeller
 

"Thom Stewart" wrote in message ...
| Pal(?)
|
| Once again you've neglected to consider the drag created when not using
| the engine.
|
| Please look at the Subject heading. Then try to remember what kind of
| Prop was being referred two AND in what kind of sea condition were being
| described.
|
| You can "Color me Gone" with this reply.


Buh bye!

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

Precision of language is most important.

Without it evil will rule.

"Liberal" use to mean a person for liberty until FDR usurped the term.

"Conservative" use to mean small government until Bush got a hold of that.

People who subvert language are using deception. Your brain is your only
defense against such slavery that will follow.

Useless propeller
 

PDW,

When was the last time you've seen a 225HP outboard on a sailboat?




http://community.webtv.net/tassail/ThomPage

Useless propeller
 

"Gilligan" wrote in message . ..
| The propeller does boil the water. It is a scientific fact and I shall offer
| irrefutable proof:
|
| http://www.brooklyn.cuny.edu/bc/ahp/MBG/MBG4/Joule.html
|
| Quotes:
|
| "In the following years he took to measuring the amount of heat generated by
| every mechanical process he could think of. He enclosed wooden paddles
| inside an insulated container and used a falling weight to turn a shaft and
| churn the paddles. Friction caused the water in the container to heat up,
| and Joule measured the heat change. From this the work done could be
| compared with the amount of heat that had been produced.
|
| By 1843 he was ready to publish. Called the mechanical equivalent of heat,
| this is value for the amount of work required to produce a unit of heat, and
| is calculated as 41,800,000 ergs. (One erg is the work done in moving a one
| gram mass through a one centimeter distance)."
|
|
|
| So, as one can plainly see that in the mid-1800's it was recognized that the
| churning of propellers heat the water. In the case of the cavitating
| propeller, the slippage is so great that the energy that would normally go
| into propelling a great ship forward goes, instead, into raising the caloric
| content of the fluid medium surrounding said propeller causing boiling and
| cavitation.
|
| Hence, the propeller boils the water, causing cavitation.
|
| My tea kettle has a propeller in it and boils water quite quickly with no
| application of heat.


I'm not denying that mechanical energy applied to water will cause
its temperature to rise but it doesn't cause it to boil in the case
of a yacht's propeller. There isn't enough energy outputted to any
ship's propeller that can cause the ocean around it (and cooling it) to boil.
No, it isn't the boiling of water that causes cavitation. It is the lowering
of pressure that causes the water to vaporize.

The very chart to which you posted a link proves this to be true.
http://encarta.msn.com/media_4615415...for_Water.html
It shows there are a couple ways to skin a cat. Water can
be vaporized by adding heat, or by lowering pressure. A prop might
add a tiny bit of heat but it subtracts great amounts of pressure.
It is the subtraction of pressure that causes cavitation.

Ready to say UNCLE yet?

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

"Gilligan" wrote in message . ..
| Precision of language is most important.
|
| Without it evil will rule.
|
| "Liberal" use to mean a person for liberty until FDR usurped the term.
|
| "Conservative" use to mean small government until Bush got a hold of that.
|
| People who subvert language are using deception. Your brain is your only
| defense against such slavery that will follow.
|

IAWTP. And, nobody ever accused DSK of having a brain...

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

"Paladin" noneofyourbusiness.www wrote in message
...

"Gilligan" wrote in message
. ..
| The propeller does boil the water. It is a scientific fact and I shall
offer
| irrefutable proof:
|
| http://www.brooklyn.cuny.edu/bc/ahp/MBG/MBG4/Joule.html
|
| Quotes:
|
| "In the following years he took to measuring the amount of heat
generated by
| every mechanical process he could think of. He enclosed wooden paddles
| inside an insulated container and used a falling weight to turn a shaft
and
| churn the paddles. Friction caused the water in the container to heat
up,
| and Joule measured the heat change. From this the work done could be
| compared with the amount of heat that had been produced.
|
| By 1843 he was ready to publish. Called the mechanical equivalent of
heat,
| this is value for the amount of work required to produce a unit of heat,
and
| is calculated as 41,800,000 ergs. (One erg is the work done in moving a
one
| gram mass through a one centimeter distance)."
|
|
|
| So, as one can plainly see that in the mid-1800's it was recognized that
the
| churning of propellers heat the water. In the case of the cavitating
| propeller, the slippage is so great that the energy that would normally
go
| into propelling a great ship forward goes, instead, into raising the
caloric
| content of the fluid medium surrounding said propeller causing boiling
and
| cavitation.
|
| Hence, the propeller boils the water, causing cavitation.
|
| My tea kettle has a propeller in it and boils water quite quickly with
no
| application of heat.


I'm not denying that mechanical energy applied to water will cause
its temperature to rise but it doesn't cause it to boil in the case
of a yacht's propeller. There isn't enough energy outputted to any
ship's propeller that can cause the ocean around it (and cooling it) to
boil.
No, it isn't the boiling of water that causes cavitation. It is the
lowering
of pressure that causes the water to vaporize.

The very chart to which you posted a link proves this to be true.
http://encarta.msn.com/media_4615415...for_Water.html
It shows there are a couple ways to skin a cat. Water can
be vaporized by adding heat, or by lowering pressure. A prop might
add a tiny bit of heat but it subtracts great amounts of pressure.
It is the subtraction of pressure that causes cavitation.

Ready to say UNCLE yet?


I can tell I am battling against a person of towering intellect who does not
back down when guided by the light of truth.

I must give in and say Uncle.

Who is this man so knowledgeable in the ways of science?

Useless propeller
 

"Thom Stewart" wrote in message
...
PDW,

When was the last time you've seen a 225HP outboard on a sailboat?


http://mymacforsale.blogspot.com/

http://www.macgregorsailors.com/phpB...5c10 0fd04a3e

Useless propeller
 

"Gilligan" wrote in message . ..
|
| "Paladin" noneofyourbusiness.www wrote in message
| ...
|
| "Gilligan" wrote in message
| . ..
| | The propeller does boil the water. It is a scientific fact and I shall
| offer
| | irrefutable proof:
| |
| | http://www.brooklyn.cuny.edu/bc/ahp/MBG/MBG4/Joule.html
| |
| | Quotes:
| |
| | "In the following years he took to measuring the amount of heat
| generated by
| | every mechanical process he could think of. He enclosed wooden paddles
| | inside an insulated container and used a falling weight to turn a shaft
| and
| | churn the paddles. Friction caused the water in the container to heat
| up,
| | and Joule measured the heat change. From this the work done could be
| | compared with the amount of heat that had been produced.
| |
| | By 1843 he was ready to publish. Called the mechanical equivalent of
| heat,
| | this is value for the amount of work required to produce a unit of heat,
| and
| | is calculated as 41,800,000 ergs. (One erg is the work done in moving a
| one
| | gram mass through a one centimeter distance)."
| |
| |
| |
| | So, as one can plainly see that in the mid-1800's it was recognized that
| the
| | churning of propellers heat the water. In the case of the cavitating
| | propeller, the slippage is so great that the energy that would normally
| go
| | into propelling a great ship forward goes, instead, into raising the
| caloric
| | content of the fluid medium surrounding said propeller causing boiling
| and
| | cavitation.
| |
| | Hence, the propeller boils the water, causing cavitation.
| |
| | My tea kettle has a propeller in it and boils water quite quickly with
| no
| | application of heat.
|
|
| I'm not denying that mechanical energy applied to water will cause
| its temperature to rise but it doesn't cause it to boil in the case
| of a yacht's propeller. There isn't enough energy outputted to any
| ship's propeller that can cause the ocean around it (and cooling it) to
| boil.
| No, it isn't the boiling of water that causes cavitation. It is the
| lowering
| of pressure that causes the water to vaporize.
|
| The very chart to which you posted a link proves this to be true.
| http://encarta.msn.com/media_4615415...for_Water.html
| It shows there are a couple ways to skin a cat. Water can
| be vaporized by adding heat, or by lowering pressure. A prop might
| add a tiny bit of heat but it subtracts great amounts of pressure.
| It is the subtraction of pressure that causes cavitation.
|
| Ready to say UNCLE yet?
|
|
| I can tell I am battling against a person of towering intellect who does not
| back down when guided by the light of truth.
|
| I must give in and say Uncle.
|
| Who is this man so knowledgeable in the ways of science?
|

And, it's a rare pleasure to meet a man who's willing to learn and
admit his (very rare) mistakes. But, I suppose you're as learned
as you are because you're willing to consider alternate views
with an open mind as well as a fondness for language as a tool
and a standard. (unlike the likes of DSK). I'm willing to bet
you're either a libertarian or a staunch Goldwater conservative.

One must wonder. Does the faulty use of language produce a
liberal or does liberalism result in a faulty use of language...

Paladin

--
Posted via a free Usenet account from http://www.teranews.com

Useless propeller
 

Paladin wrote:

Go to a dictionary and look up the definition of boil.
You will note that it mentions application of heat.

OK:

From my Funk and Wagnalls:

boil v.i. 1. To be agitated by escaping gaseous bubbles, usually from
the effect of heat: said of liquids.

Clearly the application of heat is not necessary.

I'm sure you have heard of people involved in high altitude research
talking of the possibility of having ones blood boil if exposed to near
vacuum. You appear to be engaging in an act of sophistry.

Cheers
Marty

Useless propeller
 

Thom Stewart wrote:

PDW,

When was the last time you've seen a 225HP outboard on a sailboat?

http://community.webtv.net/tassail/ThomPage

The all new Mac26XXX ?

Cheers
Marty

Useless propeller
 

"Martin Baxter" wrote in message ...
| Paladin wrote:
|
| Go to a dictionary and look up the definition of boil.
| You will note that it mentions application of heat.
|
| OK:
|
| From my Funk and Wagnalls:
|
| boil v.i. 1. To be agitated by escaping gaseous bubbles, usually from
| the effect of heat: said of liquids.

Looks to me as it this definition also speaks to the application of heat.

|
| Clearly the application of heat is not necessary.

Not according to the definition above -- note the word 'usually.'
This means there might be a rare case or two where 'to boil' does
not result from application of heat such as blood boiling when
one is mad but that case is only a euphemism.

When one is talking in the realm of physics, as is the case
of a cavitating propeller, boil has a definite meaning - that
of adding heat. But, since a prop subtracts pressure to a
much greater extent that it adds heat, vaporization occurs
because of low pressure vaporization and not high temperature
boiling.

| I'm sure you have heard of people involved in high altitude research
| talking of the possibility of having ones blood boil if exposed to near
| vacuum. You appear to be engaging in an act of sophistry.

And, they are incorrectly using the verb boil. If exposed to a
vacuum the human body will freeze and not boil or explode as
shown in some silly movies . And, if it should happen to out gas,
it would be due to a very temporary pressure differential and
will have little to do with temps.

There's nothing deceptive about a reasoned use of language.

Paladin

--
Posted via a free Usenet account from http://www.teranews.com