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#51
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Thrust vectoring
BG Jeff, you still wasting time on that imbecile? The odds on him
knowing anything about real world boat handling fall into the "minuscule to none" category. otn Jeff Morris wrote: You're absolutely wrong about this jaxie. Feynman would think you're a complete fool for invoking his "sprinkler paradox" in this case. The boat is not turned directly by the propeller, it is turned because a water flow is pressing against the rudder. "Push" and "pull" are irrelevant, and the water flow could even come from a current, or the wash from another boat. For a variety of reasons, the affect is far more powerful in foreword, but it is still there in reverse. USSailing, and Boat/US both describe this on their websites. http://www.videos.sailingcourse.com/...pring_line.htm http://www.boatus.com/seaworthy/swlines.asp And the Coast Guard http://www.uscg.mil/hq/g-o/cgaux/Pub...crew/ch10d.pdf "JAXAshby" wrote in message ... wayne, you are out of your league. *push* is required under the laws of physics. If you can't see that, just take Feynman's word for it. It is a fact of physics that you can NOT control using rudder by *pulling* water over it. you MUST push. =================== Absolutely not true. If there is water moving past the rudder, regardless of direction or cause, it can be used to create a directed thrust simply by angling the rudder away from the flow direction. The confusion arises because the prop in forward pushes a large flow across the rudder, whereas the prop in reverse pulls only a relatively small amount of water across the rudder. Small, but not zero. You don't need a degree in physics to understand this, just a little common sense. Richard Feynman would no doubt find the discussion amusing however. |
#52
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Thrust vectoring
Jax,
I may not be the brightest bulb in the box, and the last physics course I took was well over twenty years ago (I still break out in a cold sweat when I hear the words "Virial Theorem"), so if you can explain it to me I'd appreciate it. How does the rudder (or the rudder stock & pintles through which the force is applied to the hull) know whether the water flowing past it is being pushed or pulled? Now if you want to argue that the water flow across the rudder is so small that the effect of the rudder is overpowered by the prop walk, that I can buy. But to say that the water flowing past the rudder (and being deflected by it has no effect because it's motion was started by some mysterious sucking force makes no sense. Because the water column being pushed aft when in forward is of constant diameter (at least in gross terms across the distances we are toaling about), the velocity in the column is for practical purposes constant. resulting in a high velocity stream being deflected by the rudder and a large resultant lateral force. In reverse, however, there is no such water column aft of the prop. The water is being sucked in from all directions and thus it's velocity falls off as the square of the distance from the prop (again, we are taling in gross terms here). This results in a comparatively slow, but non-zero velocity as it passes the rudder. Movement of the water (regardless of it's cause) past the rudder, and its' being deflected by it causes a lateral force. JAXAshby wrote: wayne, you are out of your league. *push* is required under the laws of physics. If you can't see that, just take Feynman's word for it. It is a fact of physics that you can NOT control using rudder by *pulling* water over it. you MUST push. =================== Absolutely not true. If there is water moving past the rudder, regardless of direction or cause, it can be used to create a directed thrust simply by angling the rudder away from the flow direction. The confusion arises because the prop in forward pushes a large flow across the rudder, whereas the prop in reverse pulls only a relatively small amount of water across the rudder. Small, but not zero. You don't need a degree in physics to understand this, just a little common sense. Richard Feynman would no doubt find the discussion amusing however. -- Dan Best - (707) 431-1662, Healdsburg, CA 95448 B-2/75 1977-1979 Tayana 37 #192, "Tricia Jean" http://rangerbest.home.comcast.net/TriciaJean.JPG |
#53
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Thrust vectoring
otnmbrd wrote...
Thanks. In answer to your question, yes, but "torque steer" would not work for me, as I would be apt to apply that to "prop walk". Yep, much more appropriate; but that leaves me with no opinion. Hope you derive something useful here. Have you asked your students if they have any analogies or concepts to offer when you see the lightbulb of understanding go off in their heads that first time? |
#54
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Thrust trolling
Yea, but he always gets an "A" in the trolling category.
-- Keith __ What did you forget? "otnmbrd" wrote in message .net... BG Jeff, you still wasting time on that imbecile? The odds on him knowing anything about real world boat handling fall into the "minuscule to none" category. otn |
#55
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Thrust vectoring
I'm always learning.
Actually, most people I get into these discussions with (I'm not an instructor in any sense of a formal course, though I've taught more than one "newbie") are people with experience that have a problem or need to figure out a reason for what they are seeing/experiencing. Frequently the discussion revolves around "inboard" turning and "outboard" turning props (no one here picked up on that difference, which I find interesting, yet many were concerned with using rudders when going astern, which I was not discussing). I'm still hoping to see some other responses to my responses, since how others see things, can be as educational as how I see things BG. otn Frank Maier wrote: otnmbrd wrote... Thanks. In answer to your question, yes, but "torque steer" would not work for me, as I would be apt to apply that to "prop walk". Yep, much more appropriate; but that leaves me with no opinion. Hope you derive something useful here. Have you asked your students if they have any analogies or concepts to offer when you see the lightbulb of understanding go off in their heads that first time? |
#56
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Thrust vectoring
Boat static in slip. Put in forward gear. move rudder port and
starboard, stern moves accordingly. Put in reverse gear, again same result. 'splain dis to me,Luci? On 25 Mar 2004 21:57:40 GMT, (JAXAshby) wrote: t can also be applied to moving ahead, no, it can not. water *pushed* over a rudder can cause a rudder to turn a boat, while water "pulled" over a rudder can not. |
#57
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Thrust vectoring
geesh, jeffies, you CLAIM to have a degree in physics, yet it is plainly
obvious you don't even begin to understand what is going on. You're absolutely wrong about this jaxie. Feynman would think you're a complete fool for invoking his "sprinkler paradox" in this case. The boat is not turned directly by the propeller, it is turned because a water flow is pressing against the rudder. "Push" and "pull" are irrelevant, and the water flow could even come from a current, or the wash from another boat. For a variety of reasons, the affect is far more powerful in foreword, but it is still there in reverse. USSailing, and Boat/US both describe this on their websites. http://www.videos.sailingcourse.com/...pring_line.htm http://www.boatus.com/seaworthy/swlines.asp And the Coast Guard http://www.uscg.mil/hq/g-o/cgaux/Pub...crew/ch10d.pdf "JAXAshby" wrote in message ... wayne, you are out of your league. *push* is required under the laws of physics. If you can't see that, just take Feynman's word for it. It is a fact of physics that you can NOT control using rudder by *pulling* water over it. you MUST push. =================== Absolutely not true. If there is water moving past the rudder, regardless of direction or cause, it can be used to create a directed thrust simply by angling the rudder away from the flow direction. The confusion arises because the prop in forward pushes a large flow across the rudder, whereas the prop in reverse pulls only a relatively small amount of water across the rudder. Small, but not zero. You don't need a degree in physics to understand this, just a little common sense. Richard Feynman would no doubt find the discussion amusing however. |
#58
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Thrust vectoring
over the nee, you be a stew pid as jeffies.
go ahead. TRY to back that thing up. BG Jeff, you still wasting time on that imbecile? The odds on him knowing anything about real world boat handling fall into the "minuscule to none" category. otn Jeff Morris wrote: You're absolutely wrong about this jaxie. Feynman would think you're a complete fool for invoking his "sprinkler paradox" in this case. The boat is not turned directly by the propeller, it is turned because a water flow is pressing against the rudder. "Push" and "pull" are irrelevant, and the water flow could even come from a current, or the wash from another boat. For a variety of reasons, the affect is far more powerful in foreword, but it is still there in reverse. USSailing, and Boat/US both describe this on their websites. http://www.videos.sailingcourse.com/...pring_line.htm http://www.boatus.com/seaworthy/swlines.asp And the Coast Guard http://www.uscg.mil/hq/g-o/cgaux/Pub...crew/ch10d.pdf "JAXAshby" wrote in message ... wayne, you are out of your league. *push* is required under the laws of physics. If you can't see that, just take Feynman's word for it. It is a fact of physics that you can NOT control using rudder by *pulling* water over it. you MUST push. =================== Absolutely not true. If there is water moving past the rudder, regardless of direction or cause, it can be used to create a directed thrust simply by angling the rudder away from the flow direction. The confusion arises because the prop in forward pushes a large flow across the rudder, whereas the prop in reverse pulls only a relatively small amount of water across the rudder. Small, but not zero. You don't need a degree in physics to understand this, just a little common sense. Richard Feynman would no doubt find the discussion amusing however. |
#59
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Thrust vectoring
if you can explain it to me
I'd appreciate it. Dan, will do. it is getting late tonight. will do tomorrow. |
#60
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Thrust vectoring
shlackoff, you are lost to this universe. metaphor does not count for squat.
btw schlackoff, did you know that the climb rate/service ceiling on a Cessna 336/337 was greater single engine on the aft engine than the forward engine? of course you knew that. wayne, you are out of your league. *push* is required under the laws of physics. If you can't see that, just take Feynman's word for it. I have to agree with Jax on this one. Why else do you think all airplanes have the propellor in the back. Steve |
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