Lock that prop: the truth at last

[Dick Barthel]

Is this a belief (which means science doesn't matter) or do we look at empirical evidence?

Loren

Thanks for the link Loren. In good humor I would question your use of the phrase "empirical evidence". If I read the report correctly the freewheeling conclusions were achieved solely through calculations specifically because the experimental set up did not permit freewheeling. I believe "empirical evidence" relates to experience or observation.

As for Mr. Vigor, I think provocateur is the word of the day. He created the initial thread which has provided countless hours of fun and fellowship. A quick read of the MIT paper gives me the impression they were having fun also.

Dick

[CD-Sailor]

DELETED

[SurryMark]

... Fixed-vs.-Free-Wheeling-Prop-Testing-Data ...

avoid needless repetition?

And the humor award goes to. . .

[Bill Goldsmith]

Does this boat also have a nesting dinghy?

[darmoose]

Do here we go again? As the Seuthslayer-in-cheif (dare i say) can you imagine my surprise when in the middle of traveling, I log onto my favorite website to find that a long ago forgotten "put to bed" irroneous belief has once again arisen!!

This is the I suppose to be expected aftermath of having failed to obtain complete and utter capitulation from the defeated "author" of this silly position having to do with propeller drag and propeller positioning.

Kudos to Mitch and Mainsail and others who quickly brought forth the facts of the matter (not that the facts matter to the proplockers). Well, neverfear, I have run this query past no less an authority than the guy who operates a very complicated and expensive piece of machinery at my marina (the travel lift), who is obviously more qualified to render a conclusive opinion than another" author" (on maintenance of boats, no less) and he states without a doubt that freewheeling ones prop is the correct path to less drag and greater speed when sailing. So There!!

I do hope that this time around we can extract the requisite capitulation from J.V., although I also note his silence since firing his first shot. Really, John, Don Casey over Strathclyde University, Oceans Engr., MIT, etc.........

Darrell

[Loren]

Dick,

I believe that in the experiment (michigan 3 blade) he first locked the prop and on second run allowed it to spin. He stated that it was not allowed to spin with minimal resistance (true free wheeling) as he was trying to replicate the prop on his boat so he applied a level of resistance similar to the shaft on his boat. I believe it was an observed result.

http://www.youtube.com/watch?v=jI-UG9RSlJo

Lorenjavascript:emoticon(':)')

[Loren]

Dick,

I believe that in the experiment (michigan 3 blade) he first locked the prop and on second run allowed it to spin. He stated that it was not allowed to spin with minimal resistance (true free wheeling) as he was trying to replicate the prop on his boat so he applied a level of resistance similar to the shaft on his boat. I believe it was an observed result.

http://www.youtube.com/watch?v=jI-UG9RSlJo

Lorenjavascript:emoticon(':)')

[Maine Sail]

Dick,

I believe that in the experiment (michigan 3 blade) he first locked the prop and on second run allowed it to spin. He stated that it was not allowed to spin with minimal resistance (true free wheeling) as he was trying to replicate the prop on his boat so he applied a level of resistance similar to the shaft on his boat. I believe it was an observed result.

http://www.youtube.com/watch?v=jI-UG9RSlJo

Lorenjavascript:emoticon(':)')

Here's a link to a more in-depth explanation:
http://forums.sbo.sailboatowners.com/sh ... ostcount=1[/url]

[SurryMark]

Everybody has experimented with this, right? Has anybody found marked differences from my effort? Over about forty minutes last fall I sailed with prop locked or in neutral. The wind was fairly steady. I experimented on different courses, with and against the current. I switched from neutral to reverse about a half minute apart, or several minutes apart to allow for the drag, or lack of it, to have an effect. The gps showed varying speeds, as it always does. I saw no appreciable and consistent correlation between slowing or speeding up and being in neutral or reverse, even when all other conditions - wind direction and speed and sail trim - seemed identical, or as identical as they could be inshore. Based on all this I am prepared to affirm, without qualification, that sailing with a locked prop is better.

[bill2]

Given the preponderance of free wheeling posts lately I'm tempted to chose a contrarian position ( so that we may continue to enjoy this topic into perpetuity

( but be forewarned - next time I'll likely argue the other side

quote "
The conclusion from these calculations is that a substantial reduction in drag, and thus gains in boatspeed, can be realized when a fixed pitch propeller is allowed to freewheel.
"

Pretty conclusive for the test conditions - yep.

ah - but therein lies the rub.

Being CD'ers we have full keels and there are those that have been heard to mark their prop shafts so as to align their fixed two bladed props with the keel ( methinks they be called racers if there is such a thing among cd owners ? fwiw - maybe the " secret " of cd racers though I suspect they had much more in their bag of tricks - ie skill ! ) .

And being in the " shadow " of the keel ( the deadwood ) was specifically not addressed in the two tests cited earlier .

So not being a scientist , nor having a ged in anything I would be remiss in putting forth any speculation that the results of a fixed two bladed prop locked to align with the deadwood would have much less drag than a " free wheeling " two blade prop . I did notice that the fixed two bladed prop tested did fall in the middle of all props when it was in the " exposed " flow of water - hmmmm . And I wonder if we did not cover this territory before ? ( did we agree that this was the best scenario ? )

However maybe more knowledgeable than I can help out and the fun continue ? ? ?

[Troy Scott]

Dick wrote:
"let's all just be happy the world didn't end yesterday.."
Hmmm..., it didn't?. Wow. I guess now I have to get up and go to work after all...

[Troy Scott]

I just wish I could hurry up and get a prop on my boat, among several hundred other necessities, and get my boat in the water so I could at least have the option to lock, or not.....

We're still making progress despite occasional interruptions like work, reading discussions like this one, more work, life, etc...

Have fun, guys. Locked or not, just go sailing.

[Loren]

I think there is agreement that with the CD full keel and a 2 blade prop there is an advantage to locking the prop in the "shadow" of the keel.

Loren

[Dick Barthel]

To add to Loren's point about what we agree on don't we also agree that even if free wheeling could produce a modicum of speed increase it also quite likely would be harmful to the transmission and perhaps other parts thus making the right answer academic?

[Troy Scott]

to Dick and Loren. BUT..., giving up the powerful three-blade prop for a questionable fraction of a speed increase does seem a little impractical. At least to me. If you really want to speed up a little you could close up the prop aperture COMPLETELY. That might help noticeably. Then you might as well pitch that pesky engine and the associated prop overboard. But then what would run the generator to run the frig for martini ice? The domino effect has seriously kicked in. This could lead down the wayward path, fellows. Maybe we'd better quit while we're ahead, and while we still can make ice, and while we can still develop enough thrust with our three-blade props to get un-stuck occasionally....