How sailboats sail

[darmoose]

The "lockers" in the Boston Harbor Island Regatta and racing across Buzzards Bay have outperformed the spinners consistently. This is measuring results only for Cape Dory vs. Cape Dory.

Btw, there have been other scientific studies, as referenced here by John Vigor, that show exactly the opposite results from the test you reference. I'm not surprised, as there are more variables involved than appear at first blush.

Neil,

That could be. It is obvious from these discussions that many sailors don't even know if or how much drag (friction) they have already built into thier drive trains, so that someone who thinks they are freewheeling (because of the friction) may as well be "locked".

As for other scientific studies, I don't remember any, certainly not as recent as 2007. I'm sorry, I do remember the MIT study, but that found for the freewheeling position, didn't it?

Perhaps you or John could refresh our memory?(except John don't wanna come near this anymore)

And, you think there are more variables than were covered in the Strathclyde/Ocean Engineering 42 page study and report? Like what?

Oh well, I don't know why I am surprised?

FWISF

Darrell

[Neil Gordon]

From Answers.com:

"Francis Kinney, an equally well-respected naval architect, maintained in Skene’s Elements of Yacht Design that “the shaft should be locked so that the propeller cannot revolve. It has been found that a revolving propeller causes more drag . . . â€

[Amgine]

I don't know if my transmission lubrication is shaft-driven (Yanmar 1GM, but I don't know the make of the transmission off the top of my head.)

Do you know what specific brand and model of transmission is on your Volvo?

[Joe CD MS 300]

I think I would have to stop the fight and give the decision to Darrell.

By shear number of punches thrown (posts) Darrell has Neil beat by 7, 45-38. But it is not just the numbers. While Darrell was throwing multiple bombs, Neil was more or less throwing a lot of weak counter punches. He was a gamer though, never quit, just didn't seem like he had the ammo. For example Darrell comes up with a detailed scientific report, graphs, charts, discussion, etc. Neil counters with some second and third hand quotes but can't come up with the underlying document. Darrell's last report has Neil bloodied and staggering. Up to that point Neil was still able to defend himself but now appears to be unable to keep his hands up. That is why I believe it should be stopped.

John on the other hand has been pummelled and is either lying unconscious in the ring or has slipped out, having thrown only 5 punches, none very hard. As the initiator of the match you would have hopped for more Darrell even climbed out of the ring into another thread looking for John to no avail. Although Neil is still standing, I think Darrell is a clear winner.

If you guys want to continue the bout I will continue to check in and enjoy the action but it will not be a scantioned bout. It will be more of a fight club thing. No refs but the crowd. Where do you guys get the time?

[Neil Gordon]

By shear number of punches thrown ...

You're thinking this is like boxing? I'm thinking tag team wrestling, myself. Better defined as "bad entertainment" than "good sport."

[Maine Sail]

Both MIT & The University of Strathclydes Ocean Engineering program have given two consistent and very scientific blows to locked props yet some folks still continue to argue. Perhaps some do not know how to read scientific papers??

As I have said before, as a racer, I have seen it both ways but more consistently than not we see an increase in boat speed when we unlock the prop but this does and can cause wear.

It's tough to argue with this type of data but some folks are never wrong after all the world is flat I have seen the edge while sailing:



I marked it up with arrows for those without a science background


P.S. This is not a minor difference we are talking about. Drags resistance of up to 100% more, depending upon speed, is not even a close race it gets somewhat closer if your drive train has resistance but still no as bad as a locked prop.

[Jim Davis]

Personally I am a locker. With the wetted surface of my boat I don't think the difference in drag amounts to much. Note number 4 is the only one with any scientific logic behind it.

My reasons are few and simple:
1. Ease on the cutlass bearing.
2. Ease on the transmission.
3. Silence of not hearing the prop rotate.
4. A spinning wheel will wind up a crab/lobster pot line faster than a fixed one.

And I "know" a full keel boat dosen't catch pot lines.

[darmoose]

I think I would have to stop the fight and give the decision to Darrell.

By shear number of punches thrown (posts) Darrell has Neil beat by a 7 45-38. But it is not just the numbers. While Darrell was throwing multiple bombs, Neil was more or less throwing a lot of weak counter punches. He was a gamer though, never quit, just didn't seem like he had the ammo. For example Darrell comes up with a detailed scientific report, graphs, charts, discussion, etc. Neil counters with some second and third hand quotes but can't come up with the underlying document. Darrells last report has Neil bloodied and staggering. Up to that point Neil was still able to defend himself but now appears to be unable to keep his hands up. That is why I believe it should be stopped.

John on the other hand has been pummelled and is either lying unconscious in the ring or has slipped out, having thrown only 5 punches, none very hard. As the initiator of the match you would have hopped for more Darrell even climbed out of the ring into another thread looking for John to no avail. Although Neil is still standing, I think Darrell is a clear winner.

If you guys want to continue the bout I will continue to check in and enjoy the action but it will not be a scantioned bout. It will be more of a fight club thing. No refs but the crowd. Where do you guys get the time?

Joe,

Thank you for your clear and unbiased review of the facts as well as your blow by bow very clever and humerous analysis. Yours has been a voice of reason and understanding throughout this ordeal.

Incidently, I do not relesh carrying the ball all the time , so you or any other thinking sailor is more than welcome to contribute any time you wish (I know I don't need to tell you that).

In looking back at this epic discussion, I am truly amazed that I, nor others didn't bring this to a halt years ago. This argument is ludicrous on its surface, and can only be excused (in my mind) by the distraction that was created of helicpoters and such.

I am very gratified that when you read the Ocean Engineering report, they make several references to drive train friction and shaft braking in developing thier analysis. These are things that I have been talking about for quite some time.

All sailors out there, if they want to get optimum performance from their boats, should pay close attention to the friction in their drive trains.

Thanks again

Darrell

[Maine Sail]

All sailors out there, if they want to get optimum performance from their boats, should pay close attention to the friction in their drive trains.

Thanks again

Darrell

Yup and a PSS is a big friction reducer or Gore GFO in a regular stuffing box..

[darmoose]

Both MIT & The University of Strathclydes Ocean Engineering program have given two consistent and very scientific blows to locked props yet some folks still continue to argue. Perhaps some do not know how to read scientific papers??

As I have said before, as a racer, I have seen it both ways but more consistently than not we see an increase in boat speed when we unlock the prop but this does and can cause wear.

It's tough to argue with this type of data but some folks are never wrong after all the world is flat I have seen the edge while sailing:



I marked it up with arrows for those without a science background


P.S. This is not a minor difference we are talking about. Drags resistance of up to 100% more, depending upon speed, is not even a close race it gets somewhat closer if your drive train has resistance but still no as bad as a locked prop.

Mainsail,

That is very helpful. I hope it helps my friend, Neil.

Thanks

Darrell

[darmoose]

By shear number of punches thrown ...

You're thinking this is like boxing? I'm thinking tag team wrestling, myself. Better defined as "bad entertainment" than "good sport."

Neil,

Tag team, huh? Where's your partner?


Darrell

[Maine Sail]

Seeing as this is a Euro study the resistance was measured in "N" and the speed in "M/S".

At max study speed, as close as I can guess based on the graph, it looks to be about 3.8 meters per second or 7.3 knots.

Fixed Prop - At 7.3 knots the fixed propeller developed about 325 N or 73 pounds of resistance.

Freewheeling - At 7.3 knots the freewheeling propeller developed about 60 N or 13.5 pounds of resistance.


Go drag a 13 pound weight around your yard then do the same with a 73 pounder. While certainly not an exact comparison it is a rough estimation of the drag resistance between the two..

[Andy Denmark]

I don't believe I've ever seen a more wanton waste of space on this board than this thread. Since it has dwindled down to only a couple or three participants, I wonder why you guys don't go to Private Messages to conduct this intellectual circle jerk? I'm embarrassed that anyone coming to this board seeking positive benefits and seeing this vapid inanity would think us Cape Dory people are a bunch of mindless idiots.

Email me and I'll tell you how I really feel..........
________
Buy Volcano Vaporizer

[Joe CD MS 300]

Andy,

I wouldn't get too worked up about it. Although personally I don't think it has a whole lot of significance for Cape Dory owners, if this were a J-Boat racing board there would be a lot more interest other than the three principle combatants here. There has been some scientific info provided so it is not a total waste. It's pretty funny to me and its is pretty tame compared to some other boarts that I participate on. If you want to see some nastiness and circle jerking (intellectual or otherwise) visit a high school football board.

There is a ton of good information on this board but it can be too sugary sweet at times. I start to gag every time I see "of course I always carry charts" with any discussion of GPS or "I have no financial interest in the company...." when recommending a product.

There has been some poking between these guys but all and all they have been polite to each other. We got to have some fun too.

Joe

[Loren]

I am thankful to the sailors who researched the topic and found results from credible institutions that seem to put this discussion to rest. I added my 2 cents a while back in a couple posts and drew my own conclusions but to now see the results of the scientific investigation of the topic is satisfying. Without this discusion (arguement) I would just believe by faith - now there appears to be science behind it. Thanks for the effort.

Fair winds,
Loren

ps:If you dislike a string why would you read it?