At this moment I can't afford a folding prop. Which will give me best speed.. free spinning or locked vertically, paralled to rudder, when sailing?
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Just replaced my 3 blade on H34
with a 2 blade "winglet prop" from Bob Gilian at Bay Prop. (510)-337-9122. More speed and less drag than with 3 blade. Best reverse I have ever had. If you have existing 2 balde they charge $150.00 for winglets. They are alot of things I want more for the boat than a folding prop. According to previous post, you should put the transmission in reverse so that it receives lubrication while turning.
with a 2 blade "winglet prop" from Bob Gilian at Bay Prop. (510)-337-9122. More speed and less drag than with 3 blade. Best reverse I have ever had. If you have existing 2 balde they charge $150.00 for winglets. They are alot of things I want more for the boat than a folding prop. According to previous post, you should put the transmission in reverse so that it receives lubrication while turning.
drag
Hello Jim, Locking it down or allowing it to free wheel is not suitable for all conditions. Generally allowing the propeller to free wheel at slow sailing speeds is best. Locking the propeller down at higher speeds is generally considered best. My thought process however, being a mechanical person, is what is going on with the transmission when it is allowed to freewheel? Does the lubrication of the transmission stop when the engine is not operating the trans? Because most transmissions do not have a wet sump lubrication can damage occur with extended periods of freewheeling. Locking the system down at high speeds, can we engage the transmission but find it impossible to disengage when under severe loads. Does or could that additional load to the trans create a plate problem? It has happened in the past that some mutihulls have, at high speeds, turned the motor over with a locked down props flooding the cylinders with water!! The latest was PlayStation. Boat speed was in excess of 25 knots and it turned over two 160+Hp Yanmar’s. Ouch. Similar to starting a manual car by pushing it and popping the clutch while the transmission is in gear. I would guess that most of the time people lock the system down because they don’t enjoy the noise. The other thing, all boats are different and the reaction of the above may have varying affects. Hope this helps. Kevin
Hello Jim, Locking it down or allowing it to free wheel is not suitable for all conditions. Generally allowing the propeller to free wheel at slow sailing speeds is best. Locking the propeller down at higher speeds is generally considered best. My thought process however, being a mechanical person, is what is going on with the transmission when it is allowed to freewheel? Does the lubrication of the transmission stop when the engine is not operating the trans? Because most transmissions do not have a wet sump lubrication can damage occur with extended periods of freewheeling. Locking the system down at high speeds, can we engage the transmission but find it impossible to disengage when under severe loads. Does or could that additional load to the trans create a plate problem? It has happened in the past that some mutihulls have, at high speeds, turned the motor over with a locked down props flooding the cylinders with water!! The latest was PlayStation. Boat speed was in excess of 25 knots and it turned over two 160+Hp Yanmar’s. Ouch. Similar to starting a manual car by pushing it and popping the clutch while the transmission is in gear. I would guess that most of the time people lock the system down because they don’t enjoy the noise. The other thing, all boats are different and the reaction of the above may have varying affects. Hope this helps. Kevin
Ron, You mention Winglet Prop
I was thinking of going from a 2 blade to a 3 blade on our O'Day 35. It was mainly for some additonal power in headwinds and seas and some backing improvement. If I understand it winglets on my 2 blade prop could accomplish the same thing without going to the extra drag of a 3 blade. I would not expect the power to match a 3 blade but at least improve where we are. Good Winds, Dave s/v DAMWEGAS
I was thinking of going from a 2 blade to a 3 blade on our O'Day 35. It was mainly for some additonal power in headwinds and seas and some backing improvement. If I understand it winglets on my 2 blade prop could accomplish the same thing without going to the extra drag of a 3 blade. I would not expect the power to match a 3 blade but at least improve where we are. Good Winds, Dave s/v DAMWEGAS
Winglets are to prevent slippage.
Dave: The prop that Ron is refering to is done a Bay Props in Alameda, CA. Bob Kilian is really a very innovative guy. They claim that the winglets help eliminate the water from slipping off the tips of the blades. They also cup the prop to give it a little more efficency. Bob claims that you will have nearly the same thrust as you would by changing over to a three blade prop. These props also give you the advantage of eliminating prop walk too. This could be attributed to the fact that the prop is slightly smaller once they put the winglets on. When they do this a 15" prop essentially becomes a 14" but you can have slightly more pitch too....... You should talk to him. I have only heard positive feed back about their product.
Dave: The prop that Ron is refering to is done a Bay Props in Alameda, CA. Bob Kilian is really a very innovative guy. They claim that the winglets help eliminate the water from slipping off the tips of the blades. They also cup the prop to give it a little more efficency. Bob claims that you will have nearly the same thrust as you would by changing over to a three blade prop. These props also give you the advantage of eliminating prop walk too. This could be attributed to the fact that the prop is slightly smaller once they put the winglets on. When they do this a 15" prop essentially becomes a 14" but you can have slightly more pitch too....... You should talk to him. I have only heard positive feed back about their product.
Thanks Steve
I will give him a shout. I will give the site feedback if I go this way and try it. Good Winds Dave
I will give him a shout. I will give the site feedback if I go this way and try it. Good Winds Dave
Anyone reopen Red's?
Dave: Did anyone ever reopen Red's for their .25 cent burgers? I suppose that Oriental is a much different place than it was several year ago, now that you have that fancy new marina too.
Dave: Did anyone ever reopen Red's for their .25 cent burgers? I suppose that Oriental is a much different place than it was several year ago, now that you have that fancy new marina too.
Oriental
Unfortunately Red's is not around. Oriental is always changing. Believe it or not the new Marina really does not dominate things. There are all of about 6 boats in it and with 1200 sailboats and 1200 fishing and power boats here it will have to work hard to dominate. If you are interested where things are look in the March issue of Sail Magazine, "The Other Downeast". The guy holding the 2 on the left is me. Also you may want to check out www.towndock.net to see the happenings. You can keep up with the current stuff in the center of town by clicking on the Harbor Cam. Take Care Dave
Unfortunately Red's is not around. Oriental is always changing. Believe it or not the new Marina really does not dominate things. There are all of about 6 boats in it and with 1200 sailboats and 1200 fishing and power boats here it will have to work hard to dominate. If you are interested where things are look in the March issue of Sail Magazine, "The Other Downeast". The guy holding the 2 on the left is me. Also you may want to check out www.towndock.net to see the happenings. You can keep up with the current stuff in the center of town by clicking on the Harbor Cam. Take Care Dave
Winglets
The topic of winglets on props has been brought up many times on this site, and being in the propeller business in a previous life, the subject has interested me. This year at the International Boatbuilders Exposition I approached two different propeller manufacturers. Both replied with similar comments. The cupping is to hold more water on the prop and prevent ventilation in power boats and generally has no benefit to a sailboat. The winglets add blade area lost in the reduction of pitch or diameter. The conclusion from their investigation is that the winglets only show improvement because the original prop was not sized and/or balanced properly to begin with. BTW, every new prop out of the box is usually checked for pitch and balance by the shops that sell propellers. I don't no the situation for props installed by new boat manufacturers. I would like to see evidence of the superiority of winglets on a prop over a properly sized and balanced prop. Anyone have that information?
The topic of winglets on props has been brought up many times on this site, and being in the propeller business in a previous life, the subject has interested me. This year at the International Boatbuilders Exposition I approached two different propeller manufacturers. Both replied with similar comments. The cupping is to hold more water on the prop and prevent ventilation in power boats and generally has no benefit to a sailboat. The winglets add blade area lost in the reduction of pitch or diameter. The conclusion from their investigation is that the winglets only show improvement because the original prop was not sized and/or balanced properly to begin with. BTW, every new prop out of the box is usually checked for pitch and balance by the shops that sell propellers. I don't no the situation for props installed by new boat manufacturers. I would like to see evidence of the superiority of winglets on a prop over a properly sized and balanced prop. Anyone have that information?
Why not measure it? Here is a proposed method.....
I have been around sailing discussion fora long enough to know that this is one of the many sailing-related topics that does not appear to have a simple answer. IMHO, all indications are that it may well differ from vessel to vessel, from propeller to propeller and possibly as a function of boat speed and a number of other factors. So, why not simply measure it for your own vessel? The most obvious method, namely changing over from locked to freewheeling while underway is more complicated than it looks because the effect is likely to be minor and boat speed is constantly changing (although a well-dampened log or GPS may not always show that). So, here is the test I propose: On a calm day, just anchor in a tidal estuary, e.g. the Chesapeake Bay, and measure the speed of the tidal current with a log (your GPS won't work under these conditions, of course). As soon as the current registers approx. 1 knot you should switch from locked to freewheeling while measuring the change in pull on the anchor chain. Then repeat that at 2 and at 3 knots (or possibly more if your tidal flow permits). How do you measure anchor pull? Either with an oversized spring balance or calibrated strain gauge or with a simple heavy elastic snubber attaching your anchor chain to the bow (make sure the spring or the elastic snubber are stretched approximately halfway their maximum extension). To read the extension of the rubber snubber you will need a reliable, finely graded ruler as a yardstick. (also, you would need to calibrate this crude but effective weighing device later with some known weights in order to get quantitative results). If anyone goes to the trouble of actually measuring this we will finally have some real data to talk about rather than just so much hot air, prejudices and parroted opinions. Have fun! Flying Dutchman have fun
I have been around sailing discussion fora long enough to know that this is one of the many sailing-related topics that does not appear to have a simple answer. IMHO, all indications are that it may well differ from vessel to vessel, from propeller to propeller and possibly as a function of boat speed and a number of other factors. So, why not simply measure it for your own vessel? The most obvious method, namely changing over from locked to freewheeling while underway is more complicated than it looks because the effect is likely to be minor and boat speed is constantly changing (although a well-dampened log or GPS may not always show that). So, here is the test I propose: On a calm day, just anchor in a tidal estuary, e.g. the Chesapeake Bay, and measure the speed of the tidal current with a log (your GPS won't work under these conditions, of course). As soon as the current registers approx. 1 knot you should switch from locked to freewheeling while measuring the change in pull on the anchor chain. Then repeat that at 2 and at 3 knots (or possibly more if your tidal flow permits). How do you measure anchor pull? Either with an oversized spring balance or calibrated strain gauge or with a simple heavy elastic snubber attaching your anchor chain to the bow (make sure the spring or the elastic snubber are stretched approximately halfway their maximum extension). To read the extension of the rubber snubber you will need a reliable, finely graded ruler as a yardstick. (also, you would need to calibrate this crude but effective weighing device later with some known weights in order to get quantitative results). If anyone goes to the trouble of actually measuring this we will finally have some real data to talk about rather than just so much hot air, prejudices and parroted opinions. Have fun! Flying Dutchman have fun
New Winglets
Just got my reworked prop back (9X12) for our '77 h27. I'll report on performance in June, but I've got to say it sure is handsome, all polished up from Bay Prop. I bought it because of good reports on this site, and because there is a good theoretical reason for improved performance. A prop blade is a wing that has been twisted to keep a constant angle of attack to the oncoming water, while the outside of the wing (blade) is moving much faster than its root. All wings shed turbulent vortexes off their tips - these vortexes are always major sources of drag. They do cause noise and vibration, and may contribute to prop-walk. (Some idea about the vortex on the lower blade being more powerful because it is shed in a higher pressure (deeper) flow than the top blade. That what I learned in engineering class in the Navy, for what its worth.) Winglets _do_ make a more efficient wing (blade) for the exact same reason you see them on airplane wings - they reduce the size and effect of the tip vortex. Better efficiency would also reduce prop-walk. I doubt we can prove the noise/vibration theory. There is a great article about props in Good Old Boat this month. It explains that the wide variation in relative operating speeds is a real problem for sailboat prop designers. (Versus a power boat that probably operates at around the same speed much of the time.) It's possible that Bob at Bay Prop may have a better idea for tuning the variation of pitch in a way that fits sailboat use. All he said to me is that props often need to have their pitch corrected. Anyway , the excitement builds - only 8 weeks until we test it! Hooray...oh well. David Lady Lillie
Just got my reworked prop back (9X12) for our '77 h27. I'll report on performance in June, but I've got to say it sure is handsome, all polished up from Bay Prop. I bought it because of good reports on this site, and because there is a good theoretical reason for improved performance. A prop blade is a wing that has been twisted to keep a constant angle of attack to the oncoming water, while the outside of the wing (blade) is moving much faster than its root. All wings shed turbulent vortexes off their tips - these vortexes are always major sources of drag. They do cause noise and vibration, and may contribute to prop-walk. (Some idea about the vortex on the lower blade being more powerful because it is shed in a higher pressure (deeper) flow than the top blade. That what I learned in engineering class in the Navy, for what its worth.) Winglets _do_ make a more efficient wing (blade) for the exact same reason you see them on airplane wings - they reduce the size and effect of the tip vortex. Better efficiency would also reduce prop-walk. I doubt we can prove the noise/vibration theory. There is a great article about props in Good Old Boat this month. It explains that the wide variation in relative operating speeds is a real problem for sailboat prop designers. (Versus a power boat that probably operates at around the same speed much of the time.) It's possible that Bob at Bay Prop may have a better idea for tuning the variation of pitch in a way that fits sailboat use. All he said to me is that props often need to have their pitch corrected. Anyway , the excitement builds - only 8 weeks until we test it! Hooray...oh well. David Lady Lillie
Measurements made, Simple answer available
In the July 15, 2000 issue of Practical sailor PS says "In 1993 we worked with graduate students and professors at MIT to test a nuber of propellers. One of the tests checked to see if allowing a prop to freewheel created less drag than locking the prop in place. The answer was that "substantial" savings in drag can be had freewheeling "across the whole range of speeds." This test assumed that both props were located in the open behind shaft struts not in apertures of full keels."
In the July 15, 2000 issue of Practical sailor PS says "In 1993 we worked with graduate students and professors at MIT to test a nuber of propellers. One of the tests checked to see if allowing a prop to freewheel created less drag than locking the prop in place. The answer was that "substantial" savings in drag can be had freewheeling "across the whole range of speeds." This test assumed that both props were located in the open behind shaft struts not in apertures of full keels."
Free or Spin?
Drag isn't the whole issue here. A free-wheeling prop can possibly result in damage to your transmission. As another post mentioned, many transmissions rely on the engine running to provide proper lubrication. I'd check with your boat or engine manufacturer for some solid facts and advice. A locked (generally in Reverse to do any good!) prop does cause some drag, and a 3-blade has more than a 2-blade. But my sense is that it's not so much to be concerned about unless you're a rabid racer. In that case, you would shell out big bucks to purchase a feathering or folding prop anyway. Others on this BB have mentioned about 0.5 knot loss at hull speed, but I couldn't verify that one way or another. I have a Catalina 320 with a 3-blade fixed prop. And, I lock it while under sail. --Ron
Drag isn't the whole issue here. A free-wheeling prop can possibly result in damage to your transmission. As another post mentioned, many transmissions rely on the engine running to provide proper lubrication. I'd check with your boat or engine manufacturer for some solid facts and advice. A locked (generally in Reverse to do any good!) prop does cause some drag, and a 3-blade has more than a 2-blade. But my sense is that it's not so much to be concerned about unless you're a rabid racer. In that case, you would shell out big bucks to purchase a feathering or folding prop anyway. Others on this BB have mentioned about 0.5 knot loss at hull speed, but I couldn't verify that one way or another. I have a Catalina 320 with a 3-blade fixed prop. And, I lock it while under sail. --Ron
lubrication for Yanmar *gm transmission with engine off
The link below is an explanation for the Yanmar gm transmission operation with the engine not operating but the boat underway sailing. The biggest no no for one of these is to leave it in forward while sailing since it will probably still turn, especially at higher speeds but the drive cone will be engaged, leading to needless wear. With the transmission in reverse, the propeller shaft will positively not turn. As the diagrams show, the transmission depends on the large gears to distribute oil to the bearings and these gears turn only with the engine. As a practical matter, since there is small thrust load on the shaft while freewheeling, taking advantage of the small amount of drag reduction benefit from freewheeling is not going to hurt for day racing.
The link below is an explanation for the Yanmar gm transmission operation with the engine not operating but the boat underway sailing. The biggest no no for one of these is to leave it in forward while sailing since it will probably still turn, especially at higher speeds but the drive cone will be engaged, leading to needless wear. With the transmission in reverse, the propeller shaft will positively not turn. As the diagrams show, the transmission depends on the large gears to distribute oil to the bearings and these gears turn only with the engine. As a practical matter, since there is small thrust load on the shaft while freewheeling, taking advantage of the small amount of drag reduction benefit from freewheeling is not going to hurt for day racing.
Terry
You mentioned "freewheeling is not going to hurt for day racing", yet the link you posted states in item # 3. " ALWAYS SAIL BOATS WITH IGM, 2GM AND 3 GM TRANSMISSIONS WITH SHIFTER IN REVERSE. Why does your conclusion override the manufacturers recommendation?
You mentioned "freewheeling is not going to hurt for day racing", yet the link you posted states in item # 3. " ALWAYS SAIL BOATS WITH IGM, 2GM AND 3 GM TRANSMISSIONS WITH SHIFTER IN REVERSE. Why does your conclusion override the manufacturers recommendation?
David, contradictory recommendations?
David, I posted the Yanmar transmission photo spread several years ago mostly to educate myself. The conclusion defived from the diagrams showing the GM transmission layout is the same as Yanmar's recommendation, put it in reverse while sailing. Then later, when I became aware of the MIT testing described by Practical Sailor which concludes less drag while freewheeling, I concluded that for day sailing for a few hours or less, especially when somebody is closing on me, I put it in neutral to take advantage of whatever advantage there is in freewheeling since there is little thrust on the shaft or load on the bearings under these conditions. Crossing an ocean would be a different situation and I would then definitely keep it in reverse.
David, I posted the Yanmar transmission photo spread several years ago mostly to educate myself. The conclusion defived from the diagrams showing the GM transmission layout is the same as Yanmar's recommendation, put it in reverse while sailing. Then later, when I became aware of the MIT testing described by Practical Sailor which concludes less drag while freewheeling, I concluded that for day sailing for a few hours or less, especially when somebody is closing on me, I put it in neutral to take advantage of whatever advantage there is in freewheeling since there is little thrust on the shaft or load on the bearings under these conditions. Crossing an ocean would be a different situation and I would then definitely keep it in reverse.
Terry, when complex problems appear to have
simple answers, it may be high time to go sailing for awhile. I remember studying the MIT test data reported by Practical Sailor in detail because we had just purchased an expensive three-bladed Maxprop (after moving up from a two-bladed to a three-bladed fixed prop) and I was anxious to see whether this was money well spent or not. To the extent that any of the data and conclusions in that report could be called straightforward (let alone "simple")it may be sobering to realize that only one or two basic hull shapes were tested. I very much doubt that this included a "typical" Hunter 34 hull with u/w appendages. Also, it may be worth keeping in mind that the original poster was asking about the effect on boat SPEED. The lively discussions about transmission wear and tear (no matter how interesting) would appear to be missing the point a bit.... Have fun! Flying Dutchman
simple answers, it may be high time to go sailing for awhile. I remember studying the MIT test data reported by Practical Sailor in detail because we had just purchased an expensive three-bladed Maxprop (after moving up from a two-bladed to a three-bladed fixed prop) and I was anxious to see whether this was money well spent or not. To the extent that any of the data and conclusions in that report could be called straightforward (let alone "simple")it may be sobering to realize that only one or two basic hull shapes were tested. I very much doubt that this included a "typical" Hunter 34 hull with u/w appendages. Also, it may be worth keeping in mind that the original poster was asking about the effect on boat SPEED. The lively discussions about transmission wear and tear (no matter how interesting) would appear to be missing the point a bit.... Have fun! Flying Dutchman
Henk, couldn't agree more, sorta.....
I'd say that when simple problems are made needlessly complicated, then it's time to go sailing. The earlier referenced PS article did not equivocate and as I said in an earlier post, the conclusion PS presents is very simple, viz: testing a number of propellers indicated a substantial reduction in drag when allowed to freewheel as opposed to locking. If you have the original MIT work and are qualified to present it and feel that it does not say what PS concludes, , then do so please. Till then, I and indeed, any thinking poster will stick with PS. Transmission discussions of course logically and inevitably come up with any freewheeling discussion since there is always the concern of damaging the transmission when it is operated with the prop driving the shaft which is decoupled from the engine. For the *GM series, the single most important conclusion anyone can come away from this discussion with is do not sail with the transmission in forward.
I'd say that when simple problems are made needlessly complicated, then it's time to go sailing. The earlier referenced PS article did not equivocate and as I said in an earlier post, the conclusion PS presents is very simple, viz: testing a number of propellers indicated a substantial reduction in drag when allowed to freewheel as opposed to locking. If you have the original MIT work and are qualified to present it and feel that it does not say what PS concludes, , then do so please. Till then, I and indeed, any thinking poster will stick with PS. Transmission discussions of course logically and inevitably come up with any freewheeling discussion since there is always the concern of damaging the transmission when it is operated with the prop driving the shaft which is decoupled from the engine. For the *GM series, the single most important conclusion anyone can come away from this discussion with is do not sail with the transmission in forward.
Issue that important <?> then get a feathering <g>
If you're trying to maximize by either letting it spin or not, it seems you have just elevated your interest to the level where you might as well buy a feathering. Feathering really makes a difference in winds driving you at less than hull speed. Obviously after that, it makes little difference if you have a feathering prop, or if the prop is spinning. But in those lighter winds, it is really fun to blow by the other boats without feathering props.
If you're trying to maximize by either letting it spin or not, it seems you have just elevated your interest to the level where you might as well buy a feathering. Feathering really makes a difference in winds driving you at less than hull speed. Obviously after that, it makes little difference if you have a feathering prop, or if the prop is spinning. But in those lighter winds, it is really fun to blow by the other boats without feathering props.
Terry
Thanks for your response. Now I understand your short term freewheeling ideas. However, in another post, you state "any thinking poster will stick with PS." I disagree, any thinking poster will be suspect of any PS conclusions! Many, not all, of PS conclusions are based on subjective rather than objective anaylsis.
Thanks for your response. Now I understand your short term freewheeling ideas. However, in another post, you state "any thinking poster will stick with PS." I disagree, any thinking poster will be suspect of any PS conclusions! Many, not all, of PS conclusions are based on subjective rather than objective anaylsis.
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