How sailboats sail

[darmoose]

It is unbelievable that experienced sailors don't recognize intuitively that a propeller, otherwise unhindered, having a choice to either remain still or to spin when pulled through the water, will take the path of least resistance (which is to spin), thereby allowing the boat to sail faster. It takes considerable force to hold a propeller still when being dragged thru the water, and that force is working against the forward progress of the boat.

It is like dragging a door in a frame behind the boat and arguing if the door should be open or closed to sail faster

Neil says in my example of a sailing boat freewheeling its prop, that if i artificially slow the prop the boat will speed up. I then ask if I let go of the prop so that it speeds back up, what will the boat do, and he replys it will slow down.

So I ask anyone, how can the prop speed up while the boat is slowing down (just what do you think makes the prop speed up)?

Why dont you help Neil with that, John

Darrell

THANK YOU JOE AND MAIN SAIL

My wife says I am pig headed, stubborn, rude, politically incorrect (she goes on with this), and I just don't see where she gets it.

I don't understand either, how anyone could get irritated with this discourse, as I seem to recall one has to click on the subject to get here, and one should know what to expect by now, shouldn't one?

I would love for someone to prove me wrong, but alas, no one(not even the great "instigator") steps forward to disagree with the above quoted question and offer relevent argument.. All I ever get is abstract analogies.

The really SAD thing is not that people will believe the last man standing, but rather will believe what someone has published in a book.

And Merry Christmas to all

Darrell

[M. R. Bober]

[quote="Joe CD MS 300"]Darrel, John, Neil,

Unlike Matt who finds this thread irritating, I think it is a riot. I have pictures in my mind of all three of you laying awake at night both frustrated at not being able to convince the others of your position and endlessly trying to figure out a way to do it.

I say keep at it but try to be less polite it will up the entertainment factor. You can not allow the other side to wallow in their ignorance. Remember Winston Churchills words:

You ask, What is our policy? I will say; “It is to wage war, by sea, land and air, with all our might and with all the strength that God can give us: to wage war against a monstrous tyranny, never surpassed in the dark lamentable catalogue of human crime. That is our policy.â€

[Bill Cochrane]

...no, not me.

Chuck Husick, BoatUS magazine's tech writer, in the January '09 issue of BoatUS Magazine, retracts his previous stance as part of the locked prop camp and now is a freewheeler, although he does say that in practice it is necessary to verify that the transmission would not be harmed and that, if present, a dripless seal would be adequately lubricated.

Page 42 for those of you with access to the mag.

Somebody pass the popcorn, this is getting good.

[Amgine]

I don't have an opinion regarding the ultimate question, but to answer Darmoose's question...

So I ask anyone, how can the prop speed up while the boat is slowing down (just what do you think makes the prop speed up)?

Energy imparted to the propeller. Presumably this energy is drawn from the inertia of the vessel, and imparted via drag forces. (Which would seem to suggest the rotating prop would slow the vessel, except the motion of the prop is due to the path of least resistance; that is, the prop is going to be dragged anyway, but it will tend to follow the path of least resistance thus reducing its potential drag.)

[darmoose]

I don't have an opinion regarding the ultimate question, but to answer Darmoose's question...

So I ask anyone, how can the prop speed up while the boat is slowing down (just what do you think makes the prop speed up)?

Energy imparted to the propeller. Presumably this energy is drawn from the inertia of the vessel, and imparted via drag forces. (Which would seem to suggest the rotating prop would slow the vessel, except the motion of the prop is due to the path of least resistance; that is, the prop is going to be dragged anyway, but it will tend to follow the path of least resistance thus reducing its potential drag.)

DEAR AGNOSTIC

I have allowed ample time for those of the other persuasion to commend you on your brilliance in deductive reasoning, but alas, it seems that those pesky "proplockers" have left the building, or just simply can't bear to congradulate another where they have fallen short.

For those who didnt completely comprehend what our agnostic friend was saying, he was explaining that only when the boat goes FASTER does the propeller speed up as a result of the water rushing against the propeller at a higher velocity.

He went into condsiderable detail to refer to the natural tendency to think, at first, that the spinning propeller would slow the boat (which it does), but went on to explain that since the freewheeling propeller would in fact take the path of least resistance, and since it is being dragged thru the water anyway, that alowing it to freely spin causes the least drag, when comparing it to LOCKING ONES PROPELLER.

BRILLIANT....

Merry Christmas and A Happy New Year To All

Darrell

[Amgine]

What I said was the rotation of the prop will increase in speed once you let go of it due to the speed of the vessel.

It will still remove some energy from the system due to drag. However, that amount of energy will, and this is important, likely be less than the energy of it sitting still. Otherwise it would tend to sit still if left unlocked.

Now the reason I clarify this is I have observed some vessels in which the propeller, when properly shadowed by the keel in front of it, do tend to sit still without a lock. Clearly this is the optimal low-drag condition for these vessels.

But it is also possible those propellers will be inefficient when the vessel is under power due to a lack of clear water to the propeller aperture.

I suspect the whole discussion is subjective based on the individual hull/keel/propeller context, which makes it a classic off-season sailboater's debate.

[Neil Gordon]

Why do we suppose that the path of least resistance is the fastest for the boat? Underwater shapes can do complicated things when water passes them. Among others, they can provide lift.

Now I'm not saying that the fixed prop provides lift; I'm just saying that the forces are complicated and "path of least resistance" doesn't prove "faster."

We know that above the water line, windage can slow the boat. But in the form of sails, "windage" makes the boat go faster. If I reduce the windage by letting go the sheets and letting the sails find their path of least resistance, I slow down quite a bit. But "lock" them and I can make 6 knots in a good breeze; a bit more if I lock the prop, as well.

[darmoose]

If I reduce the windage by letting go the sheets and letting the sails find their path of least resistance, I slow down quite a bit. But "lock" them and I can make 6 knots in a good breeze; a bit more if I lock the prop, as well.

EUREKA, another epifamy. I never thought of that. You can actually catch that UNDERWATER BREEZE if you just lock your propeller.

Good thoughts, my friend

Darrell

[John Vigor]

Why do we suppose that the path of least resistance is the fastest for the boat? Underwater shapes can do complicated things when water passes them. Among others, they can provide lift.

Now I'm not saying that the fixed prop provides lift; I'm just saying that the forces are complicated and "path of least resistance" doesn't prove "faster."

We know that above the water line, windage can slow the boat. But in the form of sails, "windage" makes the boat go faster. If I reduce the windage by letting go the sheets and letting the sails find their path of least resistance, I slow down quite a bit. But "lock" them and I can make 6 knots in a good breeze; a bit more if I lock the prop, as well.

Wow, Neil, this a profound thought. You're absolutely right. This could steer the debate in a whole new direction. Good thinking, fellow prop-locker.

John Vigor

http://www.johnvigor.com/blog.html

[Neil Gordon]

This could steer the debate in a whole new direction.

Steer? You're suggesting that spinning props affect your steering, too?

Actually we know that's true because of all the discussions of prop walk. Spinning props cause boats to move SIDEWAYS. I've never seen any suggestion that going sideways makes a boat go faster. (Isn't that why boats have keels and/or centerboards, to prevent that?)

[darmoose]

Why do we suppose that the path of least resistance is the fastest for the boat? Underwater shapes can do complicated things when water passes them. Among others, they can provide lift.

Now I'm not saying that the fixed prop provides lift; I'm just saying that the forces are complicated and "path of least resistance" doesn't prove "faster."

We know that above the water line, windage can slow the boat. But in the form of sails, "windage" makes the boat go faster. If I reduce the windage by letting go the sheets and letting the sails find their path of least resistance, I slow down quite a bit. But "lock" them and I can make 6 knots in a good breeze; a bit more if I lock the prop, as well.

Wow, Neil, this a profound thought. You're absolutely right. This could steer the debate in a whole new direction. Good thinking, fellow prop-locker.

John Vigor

http://www.johnvigor.com/blog.html

Hey John,

I'd like to suggest that the above would make great advertisement for your next book. Whad da ya think?

Darrell

[Al Levesque]

My older brother was a motorcycle nut modeled after the Wild One. A trick he learned and liked practicing was the emergency high speed stop as promoted by the manufacturer of his Vincent Black Shadow. He would lock the front wheel and let it slide while slowing the bike down with the rear brake. He did stop fast and there was never loss of control. Apparently, the locked front wheel had less drag than the rear that was still rotating.

It doesn't scare me half as much when I lock my prop though.

[Sea Hunt]

I am ashamed and offer my abject apologies to this Board and all of its members.

As many of you know, our colleague Neil Gordon is visiting in South Florida from his Boston area home. He returns to Boston tomorrow where the temps are projected at 22-27 degrees F. Miami today was 79 F and tomorrow is projected at 79-80 F. I categorically deny I am trying to "rub it in".

I quickly offered to go sailing with Neil on S/V Tadpole during his South Florida visit in the hopes I would learn from his expertise. He graciously accepted. I have since learned that several other Cape Dory owners in South Florida made offers to Neil with CD 30s, 33s, etc. Being the decent person he is, he advised them he had already accepted a billet on S/V Tadpole.

I had also hoped that during our sail today I could persuade Neil to announce a "cease fire" or "truce" in his ongoing world war of "fixed versus spinning" props. I am ashamed to report that after three hours of sailing I was unable to obtain a "cease fire". I used all of my negotiating skills gleamed from several Secretaries of State and peace negotiators. Neil’s final words to me on this subject were "I will fight to my last breath; I will fight to my last breath; I will fight to my last breath", apparently extracted from statements by the current Governor of Illinois. Very sad.

I did enjoy an excellent four hours with Neil. I got to meet his friend, Laura, and her mother at the sailing club dock in the morning. Laura and her mother are wonderful young ladies. Before sailing, Neil offered several helpful suggestions about repairing the damaged teak toe rail that I plan to incorporate into my repair scenario.

The winds were nonexistent (zero, nada, bupkus) when we cast off lines and motored out to Biscayne Bay. After raising sails and essentially drifting with the tide (zero wind) for the first 2 hours, we finally came into some wind (4-5 kts) during the third hour and enjoyed a great sail, albeit brief. Neil made the very best use of canvas even with these light winds. Impressive.

For those of you who have not met Neil, let me tell you he is one very nice guy - very knowledgeable about sailboats (prop locking/spinning not withstanding) and he tells some really funny stories, especially about a guy with what to the casual observer would be a very long "appendage". I am not sure if Neil enjoyed himself but I had a GREAT TIME

My only disappointment was my complete failure at obtaining a cease fire agreement for the holidays. I again apologize to this board.

P.S. For those of you still unsure of the "correct" answer, I would respectfully commend you to the formula E=mc2 by some guy named "Albert" something or other.

[M. R. Bober]

Know what I like about this thread?



Mitchell Bober
Sunny Lancaster (where none of us is as dumb as all of us), VA

[Neil Gordon]

>>I had also hoped that during our sail today I could persuade Neil to announce a "cease fire" or "truce" in his ongoing world war of "fixed versus spinning" props.<<

But that would prevent either (i) a thorough, scientific examination of the subject or (ii) converting the lost souls of spinners.

>>... I am ashamed to report that after three hours of sailing I was unable to obtain a "cease fire".<<

Maybe if you had whistled up more wind.

>>"I will fight to my last breath; I will fight to my last breath; I will fight to my last breath", ...<<

Trust me, it took most of my breath just to say that three times.

>>I am not sure if Neil enjoyed himself ...<<

You may not be sure, but I'm sure that I enjoyed myself. Thanks for the hospitality and I'm sorry I wasn't able to find the time to meet more of the Florida contingent.

>>For those of you still unsure of the "correct" answer, I would respectfully commend you to the formula E=mc2 ...<<

I would agree with that. If you could get your prop spinning at the speed of light, you'd surely go fast.