another theory question???????????

[Sked]

I thought I might raise another hopefully interesting question to see what kind of thoughts there are on this. I'm staying out of this one and letting you guy's have all the fun. Enjoy. Here you go.
Does a propeller work as a screw or as a pump?

[WILDERTHANU54]

IT SPINS ROUND AND ROUND AND ROUND, AND MAKES BOATS GO REALLY FAST, LOL! ! !
GEOFF

[FlatRacer]

BOTH!.........and NEITHER!
-uh,-
I DON'T FRIGGIN' KNOW!!!! :mad:
The voices,... they're coming back,...oh, crap... eek!

[Kindsvater Flat]

Makes you wonder.......Does it pull or push? At least it don't squirt!!

[superdave013]

WILDERTHANU54:
IT SPINS ROUND AND ROUND AND ROUND, AND MAKES BOATS GO REALLY FAST, LOL! ! !
GEOFFlol, it spins around the outside round the outside!

[Rexone]

Ok, I'll bite, it's a screw because to be a pump it would have to have a containment housing to move the water through. It's also a screw when you hit something because it screws up everything under your boat and then screws up your bank account fixing all the crap :D plus, if it was a pump it would suck and we all know prop boats don't suck!

[pgf127rt]

Great topic and an excellent answer Rex, the basis is all pumps unless they are the diaphragm type have an impeller and all propellers propel by screwing their way through air or water.

[WILDERTHANU54]

Rexone:
It's also a screw when you hit something because it screws up everything under your boat and then screws up your bank account fixing all the crap :D LMAO!!!!!!!! :D

[Snowboat]

It works as a screw, and pulls. There is no push, that's where the slip comes in, as in ventilation. It only pulls.

[boatguy222]

It's a trick question!!!!
It all depends on if you own a Jones, or If you own a Biesemeyer :D
[ October 11, 2002, 08:23 PM: Message edited by: boatguy222 ]

[Infomaniac]

I cannot decide if I would rather be screwed or pumped. Sounds painful either way.

[GofastRacer]

Infomaniac:
I cannot decide if I would rather be screwed or pumped. Sounds painful either way.http://www.plauder-smilies.com/happy/roflmao.gif http://www.plauder-smilies.com/happy/roflmao.gif http://www.plauder-smilies.com/happy/roflmao.gif

[INEEDAV]

Ken
Are you sure the prop is pulling water in the front, or is water running in to fill the void left by the water being pushed out the back?

[DaveA]

Weeellll...
Let's all hop in under the water and take a look as the propeller goes by over our heads- Nothing better than first-hand experience.
Jet boats are not JETS- they don't suck and squeeze and BOOM! and blow- they're just pumps. Got one of them in the dishwasher that sprays water all over everything. See the parallel?
Just axx any of the aeroplane mechanics here.

[CircleJerk]

JSSK88:
I thought I might raise another hopefully interesting question to see what kind of thoughts there are on this. I'm staying out of this one and letting you guy's have all the fun. Enjoy. Here you go.
Does a propeller work as a screw or as a pump?BOTH! Newtons law pushes a boat forward. I think a propeller is a screw-pump, pushing water to the rear and moving me to the front of the pack. JERKAGUESS

[FlatRacer]

Nope, not me,....I'm not saying a freakin' word!

[FlatRacer]

Christ, I can't stand it!!! :mad: Okay, here's the answer:
Niether. It's a foil. :p
[ October 16, 2002, 01:20 PM: Message edited by: FlatRacer ]

[stix818]

I'm going with Rexs' answer. It pushes and it's a screw. Snowboat what are you talking about when you say ventilation? Are you talking about cavitation?

[Stab-n-Steer]

Snowboat is correct. A boat prop is a screw, hence the name. I pulls rather than pushes. Compare it to a prop on an airplane that "pulls" it through the air. A turboprop (jet) would be the equivalent to a jet boat pump where it pulls in air (or water in case of a boat) through a large intake, compresses it and forces it out a small outlet creating thrust to propel it...
My theory anyway... :D
S&S

[schiada96]

S&S what about airplanes with the propeller on the back?

[superdave013]

I'm not bitting on that one!
But let me ask you this. Do you think this screws or pumps??
http://www.groove2000.com/mollyfoto/m92free/molly92002.jpg

[126driver]

Now that's the kind of theory question I'm talking about! :cool:

[Stab-n-Steer]

Infomaniac:
I cannot decide if I would rather be screwed or pumped. Sounds painful either way.Geez, If I've heard that from my wife once, I've heard it a thousand times! :D
S&S

[missilemud]

:rolleyes: :rolleyes: ummmm......

[21rayson]

it depends if your on top or bottem.

[dossangers]

It SCREWS the competition I CRACK MYSELF UP!!! :mad: :mad:

[Stab-n-Steer]

schiada96:
S&S what about airplanes with the propeller on the back?I knew someone would ask that! It's still doing the same thing as the prop on the front, "screwing" itself through the air... Man, this is a boat forum, how'd we get onto airplanes??? wink
S&S

[FlatRacer]

Stab-N-Steer: If an airplane propeller just screws itself through the air, then why would its blades have a cross-section similar to that of a wing? Why wouldn't the propeller blade just be flat?
Here's why: Picture an airplane prop sitting on a table face up, or for that matter picture a helicopter blade as it sits on the craft. Its top surface is curved and its bottom surface is flat. Why? So that when it passes through the air, the air that gets split off and passes over the top side has a longer distance to travel than the air that passes under the bottom. The same number of air molecules pass over it as pass under it. Therefore, the air that has further to travel will be less dense. High pressure on bottom, low pressure on top = lift.
Invert the wing and you place the high pressure side on top to generat downforce. Spin the wing around a horizontal axis and you've got foward thrust. (Low pressure on the front side and high pressure on the back side. Objects tend to move away from areas of high pressure to areas of low pressure.)
So, a propeller is just a spinning wing creating a pressure differential to induce the craft to move. And it works just the same in the water as it does in the air. Any fluid medium will do.