"the prop will create three times more drag when allowed to rotate than it will when locked"
http://www.shaftlok.com/FreewheelStoryShaftLok.htm
And I remain . . . locked
Shaft Brake
Moderator: Jim Walsh
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Derek Matheson
- Posts: 52
- Joined: Sep 21st, '06, 08:07
- Location: 1981 CD28 #282 Gaelic Gal
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Carter Brey
- Posts: 709
- Joined: Feb 5th, '05, 12:02
- Location: 1982 Sabre 28 Mk II #532 "Delphine"
City Island, New York - Contact:
Re: . . . and Nigel Warren sez
Fascinating! Even the experts disagree.Derek Matheson wrote:"the prop will create three times more drag when allowed to rotate than it will when locked"
http://www.shaftlok.com/FreewheelStoryShaftLok.htm
And I remain . . . locked
Well, I'll leave it to you members of the Locked/Unlocked synod to sort it out.
Two months until the cover comes off.
Carter Brey
Sabre 28 MkII #532 "Delphine"
City Island, NY
Was that a paid advertisement??
Well, i guess nobody is gonna be surprised that i have a comment or two. 
Carter,
Nice to hear from you. And nice to know that no less an authority than Dave Gerr, author of the Propeller Handbook agrees with me totally.
Now about that paid advertisement referred to by our friend Derek. Really, from 1979, and from apparently a company selling shaft brakes. Do you think this guy might have a little bit of a vested interest in convincing sailors to lock their propellers?? How ironic that the shaft brake is the perfect tool to prove that a locked propeller creates more drag than a freewheeling propeller. And Nigel Warren (who is that ) says he is going to show us a chart (i didnt see any chart).
And Derek, I would have thought you would'a just jumped all over wantin to answer either one of my questions to prove your argument. I am gonna wait right here, take your time.
I wonder what's it gonna take to get folks to capitulate here? I mean, havent we proved our case? We got it all on the line here. Is there any proplocker that can answer either of the questions I asked Derek (see above). That all it would take to convert me.
I'll just hang around here...
darrell
Carter,
Nice to hear from you. And nice to know that no less an authority than Dave Gerr, author of the Propeller Handbook agrees with me totally.
Now about that paid advertisement referred to by our friend Derek. Really, from 1979, and from apparently a company selling shaft brakes. Do you think this guy might have a little bit of a vested interest in convincing sailors to lock their propellers?? How ironic that the shaft brake is the perfect tool to prove that a locked propeller creates more drag than a freewheeling propeller. And Nigel Warren (who is that ) says he is going to show us a chart (i didnt see any chart).
And Derek, I would have thought you would'a just jumped all over wantin to answer either one of my questions to prove your argument. I am gonna wait right here, take your time.
I wonder what's it gonna take to get folks to capitulate here? I mean, havent we proved our case? We got it all on the line here. Is there any proplocker that can answer either of the questions I asked Derek (see above). That all it would take to convert me.
I'll just hang around here...
darrell
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Dean Abramson
- Posts: 1483
- Joined: Jul 5th, '05, 11:23
- Location: CD 31 "Loda May"
Vision
I keep having this vision. It's of this man sitting in his office. it appears to be somewhere in the northwestern part of the US. In the office there are various objects which would lead me to believe this man is a writer of some sort, perhaps of nautical books.
There is like an electrical current surging through the man's hands which tries to pull his fingers to his computer keyboard. But he fights it.
It is unclear whether he or the magnetic force will prevail. It is touch and go. Day after day, it goes on. It is an epic struggle.
What is this all about???
Dean
There is like an electrical current surging through the man's hands which tries to pull his fingers to his computer keyboard. But he fights it.
It is unclear whether he or the magnetic force will prevail. It is touch and go. Day after day, it goes on. It is an epic struggle.
What is this all about???
Dean
Dean Abramson
Cape Dory 31 "Loda May"
Falmouth, Maine
Cape Dory 31 "Loda May"
Falmouth, Maine
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Neil Gordon
- Posts: 4367
- Joined: Feb 5th, '05, 17:25
- Location: s/v LIQUIDITY, CD28. We sail from Marina Bay on Boston Harbor. Try us on channel 9.
- Contact:
Powered hang gliders
This from an article on powered hang gliders:
"The propeller is locked in place while soaring power off, as a wind milling propeller has more drag than a stationary one: Expect a 10 to 20% decrease in glide performance with a wind milling propeller (clutched units) and 2 to 4% decrease with a locked propeller."
"The propeller is locked in place while soaring power off, as a wind milling propeller has more drag than a stationary one: Expect a 10 to 20% decrease in glide performance with a wind milling propeller (clutched units) and 2 to 4% decrease with a locked propeller."
Fair winds, Neil
s/v LIQUIDITY
Cape Dory 28 #167
Boston, MA
CDSOA member #698
s/v LIQUIDITY
Cape Dory 28 #167
Boston, MA
CDSOA member #698
Where In The World Is J.V.?
How come no one will even take a shot at answering my questions to Derek.
The shaft brake dont lie, and can't be fooled.
Why is it that all I hear about is flying contraptions? Does'nt anybody go into the water anymore?
Dah-Dum...Da-Dum...DaDada-Daaaahh!!!
Let's get back into the water.
darrell
The shaft brake dont lie, and can't be fooled.
Why is it that all I hear about is flying contraptions? Does'nt anybody go into the water anymore?
Dah-Dum...Da-Dum...DaDada-Daaaahh!!!
Let's get back into the water.
darrell
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Carl Thunberg
- Posts: 1287
- Joined: Nov 21st, '05, 08:20
- Location: CD28 Cruiser "Loon" Poorhouse Cove, ME
Circular Reasoning
Darrell,
Something about this entire propellor/shaft brake argument has been bugging me for several days. I believe you've fallen pray to an age-old logic trap that many before you have also fallen into. Your argument relies on circular reasoning. You have assumed a pattern of virtual observations as fact, and then used that pattern of assumed facts to prove the conclusion you want to prove. This is circular reasoning and is fatally flawed logic. You can't assume the point you're trying to prove.
A good theory explains a set of actual observations. There are no actual observations in this shaft brake analogy. To draw parallels with Einstein is presumptive at best. This will be my last post on this topic.
Something about this entire propellor/shaft brake argument has been bugging me for several days. I believe you've fallen pray to an age-old logic trap that many before you have also fallen into. Your argument relies on circular reasoning. You have assumed a pattern of virtual observations as fact, and then used that pattern of assumed facts to prove the conclusion you want to prove. This is circular reasoning and is fatally flawed logic. You can't assume the point you're trying to prove.
A good theory explains a set of actual observations. There are no actual observations in this shaft brake analogy. To draw parallels with Einstein is presumptive at best. This will be my last post on this topic.
CDSOA Commodore - Member No. 725
"The more I expand the island of my knowledge, the more I expand the shoreline of my wonder"
Sir Isaac Newton
"The more I expand the island of my knowledge, the more I expand the shoreline of my wonder"
Sir Isaac Newton
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Joe CD MS 300
- Posts: 995
- Joined: Jul 5th, '05, 16:18
- Location: Cape Dory Motor Sailor 300 / "Quest" / Linekin Bay - Boothbay Harbor
Darrell,
Who is right in this issue is of little consequence to me, my manual suggests putting the throttle into reverse when sailing and so does my yard. So that is what I do (when I remember). The loss of a fraction of a knot might be of importance to a racer or long distance cruiser but to me and my harbour hopping the maintenance and condition of my engine and transmission is far more important.
You claimed that you do not wish to offend anyone however I personally find your repeated requests that you be declared the "winner" in this debate offensive. Your sign off on one post "EUREKA, I AM RIGHT, I AM RIGHT, I AM RIGHT" (even if quoted from someone else) was kind of obnoxious.
Everyone is going to have their own opinion, right or wrong, its not the end of the world. If you are going to devote all this time and energy to convince the world that you are right about something, why don't you pick an issue of more importance. Sorry if I offended you but that is how I feel.
Who is right in this issue is of little consequence to me, my manual suggests putting the throttle into reverse when sailing and so does my yard. So that is what I do (when I remember). The loss of a fraction of a knot might be of importance to a racer or long distance cruiser but to me and my harbour hopping the maintenance and condition of my engine and transmission is far more important.
You claimed that you do not wish to offend anyone however I personally find your repeated requests that you be declared the "winner" in this debate offensive. Your sign off on one post "EUREKA, I AM RIGHT, I AM RIGHT, I AM RIGHT" (even if quoted from someone else) was kind of obnoxious.
Everyone is going to have their own opinion, right or wrong, its not the end of the world. If you are going to devote all this time and energy to convince the world that you are right about something, why don't you pick an issue of more importance. Sorry if I offended you but that is how I feel.
Better to find humility before humility finds you.
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Derek Matheson
- Posts: 52
- Joined: Sep 21st, '06, 08:07
- Location: 1981 CD28 #282 Gaelic Gal
Re: Circular reasoning et al
Darrell:
Give me a break, ole buddy. I work full-time, people are lining up outside my office, my coffee keeps going cold, I have a hour drive to work, and an hour back home. I am pleading with you now to go back and read my previous posts . . . . I don't have the time to indulge in this debate without a steady supply of frothy frosties, and a large bag of bbq fritos to give me reason to drink them.
I read your questions again and again, and have no answers that would satisfy you, as your basic premise is incorrect. Until you grasp that the force that you put on the shaft is at right angles to the drag of the prop on the boat, I can't help you.
I can, however, help myself. So I am going to get another cup of coffee.
I remain . . . locked,
Derek M.
PS, do you have a degree in Physics or Engineering? Be honest now!
Give me a break, ole buddy. I work full-time, people are lining up outside my office, my coffee keeps going cold, I have a hour drive to work, and an hour back home. I am pleading with you now to go back and read my previous posts . . . . I don't have the time to indulge in this debate without a steady supply of frothy frosties, and a large bag of bbq fritos to give me reason to drink them.
I read your questions again and again, and have no answers that would satisfy you, as your basic premise is incorrect. Until you grasp that the force that you put on the shaft is at right angles to the drag of the prop on the boat, I can't help you.
I can, however, help myself. So I am going to get another cup of coffee.
I remain . . . locked,
Derek M.
PS, do you have a degree in Physics or Engineering? Be honest now!
Joe and Derek
Forgive me, please, I do not wish to offend anybody. I attempt to inject a little humor to lighten the air, but perhaps it is not well recieved. If you havent been following this subject from its beginning, you cant appreciate the level of certitude expressed for proplocking by its leaders.
I consider this all nothing more than good fun. I dont advocate freewheeling cause i know there are other reasons to lock ones prop.
Derek, I appreciate your comments, humor, and steadfastness. You need to realize that it is the drag on the boat and the drag on the propeller that causes the propeller to "have to spin", which spins the shaft, which we can measure with a shaft brake. They are tied together like the gears of a watch. They are relative to each other, and we can draw conclusive answers regarding this whole subject by observing this mechanism.
I consider this all nothing more than good fun. I dont advocate freewheeling cause i know there are other reasons to lock ones prop.
Derek, I appreciate your comments, humor, and steadfastness. You need to realize that it is the drag on the boat and the drag on the propeller that causes the propeller to "have to spin", which spins the shaft, which we can measure with a shaft brake. They are tied together like the gears of a watch. They are relative to each other, and we can draw conclusive answers regarding this whole subject by observing this mechanism.
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Dean Abramson
- Posts: 1483
- Joined: Jul 5th, '05, 11:23
- Location: CD 31 "Loda May"
Two cents worth
Darrell,
My gut tells me that if I let the prop spin, there is less resistance. If left in neutral, it wants to spin, so to me that must be the path of least resistance.
However, letting it spin is putting wear on my shaft and bearings and, I think, the transmission. Therefore I keep it locked by putting the transmission in reverse. This is a choice, not a scientific conclusion, or anything I am a strong proponent of.
In other words, I basically agree with your premise on the prop.
What I do not agree with is that somehow folks have not been respectful of you. All these posts on a well-shopworn topic suggest that there has been ample respect for you and interest in your theories. It has all been quite civil. Until now.
You say that "This is not how serious questions of science are solved." News flash: this is not a serious question of science. This is an arcane point relating to our sailboats, our large toys. There may be questions about science involved, but when you take personally the fact that someone does not agree, or declare you the winner, and you begin to impugn others, that is about you. Not them. Not science.
In my work, I am sometimes forced to visit internet forums regarding photo imaging software. People are calling each other morons because they don't know to hit a certain key before they click. Life is too short for this baloney.
Anyway, I am declaring you the winner. The prize is in the mail.
Dean
My gut tells me that if I let the prop spin, there is less resistance. If left in neutral, it wants to spin, so to me that must be the path of least resistance.
However, letting it spin is putting wear on my shaft and bearings and, I think, the transmission. Therefore I keep it locked by putting the transmission in reverse. This is a choice, not a scientific conclusion, or anything I am a strong proponent of.
In other words, I basically agree with your premise on the prop.
What I do not agree with is that somehow folks have not been respectful of you. All these posts on a well-shopworn topic suggest that there has been ample respect for you and interest in your theories. It has all been quite civil. Until now.
You say that "This is not how serious questions of science are solved." News flash: this is not a serious question of science. This is an arcane point relating to our sailboats, our large toys. There may be questions about science involved, but when you take personally the fact that someone does not agree, or declare you the winner, and you begin to impugn others, that is about you. Not them. Not science.
In my work, I am sometimes forced to visit internet forums regarding photo imaging software. People are calling each other morons because they don't know to hit a certain key before they click. Life is too short for this baloney.
Anyway, I am declaring you the winner. The prize is in the mail.
Dean
Dean Abramson
Cape Dory 31 "Loda May"
Falmouth, Maine
Cape Dory 31 "Loda May"
Falmouth, Maine
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bottomscraper
- Posts: 1400
- Joined: Feb 5th, '05, 11:08
- Location: Previous Owner of CD36 Mahalo #163 1990
- Contact:
A Joke
This may or may not have anything to do with the discussion but it happens to be one of my favorite jokes.
Milk production at his Vermont dairy farm was low so the farmer wrote to the University of Vermont, asking for help. A multidisciplinary team of professors was assembled, headed by a theoretical physicist, and two weeks of intensive on-site investigation took place. The scholars then returned to the university, notebooks crammed with data, where the task of writing the report was left to the team leader. Shortly thereafter the farmer received the write-up, and opened it to read on the first line: "Assume a spherical cow. . . "
Milk production at his Vermont dairy farm was low so the farmer wrote to the University of Vermont, asking for help. A multidisciplinary team of professors was assembled, headed by a theoretical physicist, and two weeks of intensive on-site investigation took place. The scholars then returned to the university, notebooks crammed with data, where the task of writing the report was left to the team leader. Shortly thereafter the farmer received the write-up, and opened it to read on the first line: "Assume a spherical cow. . . "
Rich Abato
Nordic Tug 34 Tanuki
Previous Owner Of CD36 Mahalo #163
Southern Maine
http://www.sailmahalo.com
Nordic Tug 34 Tanuki
Previous Owner Of CD36 Mahalo #163
Southern Maine
http://www.sailmahalo.com
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Cathy Monaghan
- Posts: 3503
- Joined: Feb 5th, '05, 08:17
- Location: 1986 CD32 Realization #3, Rahway, NJ, Raritan Bay -- CDSOA Member since 2000. Greenline 39 Electra
- Contact:
Note from the Webmaster...
I'm glad to see that some of the statements made in this thread are "nothing more than good fun", especially since they could and may well have been taken otherwise.darmoose wrote:Forgive me, please, I do not wish to offend anybody. I attempt to inject a little humor to lighten the air, but perhaps it is not well recieved. If you havent been following this subject from its beginning, you cant appreciate the level of certitude expressed for proplocking by its leaders.
I consider this all nothing more than good fun. I dont advocate freewheeling cause i know there are other reasons to lock ones prop.
Derek, I appreciate your comments, humor, and steadfastness. You need to realize that it is the drag on the boat and the drag on the propeller that causes the propeller to "have to spin", which spins the shaft, which we can measure with a shaft brake. They are tied together like the gears of a watch. They are relative to each other, and we can draw conclusive answers regarding this whole subject by observing this mechanism.
Everybody, please try to keep the focus of the discussion on providing comments and opinions regarding the question that started this thread:
darmoose wrote:Calling all CDers,
I am thinking of installing a shaft brake on Mystic Rose. I would like to be able to slow the shaft"s spinning, maybe even stop the shaft completely, while under sail. I dont want to use the transmission (by putting it in gear) because my Volvo manual (and the dealer) recommends against it on this particular model.
Can anyone explain how a shaft brake actually works? I am wondering about the force necessary to slow down the spinning shaft and even to bring it to a stop? Do you think it would take more or less force to actually stop the shaft than just to slow it down? (hhhmmm)
Sure would appreciate any wisdom that might be gleaned from this august board.
Thanks in advance
Darrell
s/v Mystic Rose
Please don't forget that everyone is welcome, allowed and encouraged to both agree and disagree with everyone else's opinions without fear of being chastised, belittled or attacked.
Thanks,
Cathy
CDSOA Webmaster
