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What are the pros and cons of a folding prop?
I'm going to re-power soon and am also going to get new shaft and prop.
It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. Thanks, Mark , "Belle" Westsail 32 |
You will definitely will see a decent speed improvement under sail with a
folding prop. Depending on the prop you buy, you should see better power/control in reverse too. They are very reliable now, so I don't think that is a down side. The biggest downside is their cost. I have a Max prop and think it great. Paul www.jcruiser.org "MLapla4120" wrote in message ... I'm going to re-power soon and am also going to get new shaft and prop. It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. Thanks, Mark , "Belle" Westsail 32 |
You will definitely will see a decent speed improvement under sail with a
folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? |
Its real easy to test, as I can get my folding 3 blade to stay open. I can
see the boat speed, then have it fold and measure the speed. It is significant. If the MIT tests say otherwise then they are not testing reality - wanna guess what errors they made in the test or you in the interpretation??. Paul www.jcruiser.org "JAXAshby" wrote in message ... You will definitely will see a decent speed improvement under sail with a folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? |
Assuming you're talking about a sailboat, then I'm currently taking a
look at www.kiwiprops.co.nz which look neat, and the testimonials read well. But I've no personal experience. I'd like to hear from anyone who has |
Its real easy to test, as I can get my folding 3 blade to stay open. I can
see the boat speed, then have it fold and measure the speed. It is significant. If the MIT tests say otherwise then they are not testing reality - wanna guess what errors they made in the test or you in the interpretation??. sure, paul lever knows more testing props than MIT. good on ya, paul. Paul www.jcruiser.org "JAXAshby" wrote in message ... You will definitely will see a decent speed improvement under sail with a folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? |
As usual, Jax has taken some good data and come up with a completely
erroneous conclusion. The drag from the prop increases as the square of the speed. Using the MIT figures, at 8 knots you are looking at something over 430 pounds of drag. For a medium displacement boat that can add up to 15% or more in improved performance. For a 40' LWL cruiser that means an extra 20 to 25 miles a day. Paul L wrote: Its real easy to test, as I can get my folding 3 blade to stay open. I can see the boat speed, then have it fold and measure the speed. It is significant. If the MIT tests say otherwise then they are not testing reality - wanna guess what errors they made in the test or you in the interpretation??. Paul www.jcruiser.org "JAXAshby" wrote in message ... You will definitely will see a decent speed improvement under sail with a folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
"Paul L" wrote:
You will definitely will see a decent speed improvement under sail with a folding prop. Depending on the prop you buy, you should see better power/control in reverse too. They are very reliable now, so I don't think that is a down side. The biggest downside is their cost. I have a Max prop and think it great. Paul www.jcruiser.org "MLapla4120" wrote in message ... I'm going to re-power soon and am also going to get new shaft and prop. It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] grandma Rosalie |
glenn, just where is it you found you "facts" that "a medium displacement boat"
has 2,866.66666666 pounds of drag? btw, "a medium displacement boat" that does 8 knots continuous is rare indeed. btw-2: that 15% that is so often bandied about comes from a marketing department at a folding prop company. btw-3: ------ folding -------- three blade props are rare indeed. btw-4: the subject of this thread is folding, not feathering (a hugely more expensive breed of cat) btw-5, the 170# figures from MIT were for --------- three --------- bladed props. Two bladed props have much less drag, and two bladed props aligned behind the keel have even less. btw-6, when the winds are sufficient to drive ""a medium displacement boat" at 8 knots, you have more than enough wind to drive the boat at 8 knots with a bucket dragging behind just by putting up anothe 20 square feet of sail. btw-7: most folding/feathering props are promoted by their marketers as an improvement in **LITE** airs, not heavy. As usual, Jax has taken some good data and come up with a completely erroneous conclusion. The drag from the prop increases as the square of the speed. Using the MIT figures, at 8 knots you are looking at something over 430 pounds of drag. For a medium displacement boat that can add up to 15% or more in improved performance. For a 40' LWL cruiser that means an extra 20 to 25 miles a day. Paul L wrote: Its real easy to test, as I can get my folding 3 blade to stay open. I can see the boat speed, then have it fold and measure the speed. It is significant. If the MIT tests say otherwise then they are not testing reality - wanna guess what errors they made in the test or you in the interpretation??. Paul www.jcruiser.org "JAXAshby" wrote in message ... You will definitely will see a decent speed improvement under sail with a folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Rosalie, your prop was also turning while you were running the engine. that
alone is one hell of a drag. "Paul L" wrote: You will definitely will see a decent speed improvement under sail with a folding prop. Depending on the prop you buy, you should see better power/control in reverse too. They are very reliable now, so I don't think that is a down side. The biggest downside is their cost. I have a Max prop and think it great. Paul www.jcruiser.org "MLapla4120" wrote in message ... I'm going to re-power soon and am also going to get new shaft and prop. It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] grandma Rosalie |
JAXAshby wrote: glenn, just where is it you found you "facts" that "a medium displacement boat" has 2,866.66666666 pounds of drag? From the VPP diagrams and backup data on my boat, the VPP for a Beneteau First 47, C.A. Marchaj's "Sail Performance" and working backwards from Dave Gerr's figures. The VPPs were run with standard and Gori folding 3 bladed props and showed from 12 to 15% increased speeds with the folding props up to about 80% of the first reef point. 20 miles a day is a 15% improvement on a base 5.6 knot cruising speed and you are correct that folding props make the most difference in light air. Reducing drag has the advantage over adding sail area in that it does not add to heeling moment. BTW, Gori, Martec, Brunton/Varifold and others make 3 blade folders. Volvo even makes a 4 bladed folder. Now, you can continue to rant and make an ass of yourself as usual but that is all I have to say about it. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
bite me.
"JAXAshby" wrote in message ... Its real easy to test, as I can get my folding 3 blade to stay open. I can see the boat speed, then have it fold and measure the speed. It is significant. If the MIT tests say otherwise then they are not testing reality - wanna guess what errors they made in the test or you in the interpretation??. sure, paul lever knows more testing props than MIT. good on ya, paul. Paul www.jcruiser.org "JAXAshby" wrote in message ... You will definitely will see a decent speed improvement under sail with a folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? |
There aren't too many other things you can do to gain that much performance
that easily. Paul "Glenn Ashmore" wrote in message news:OI2Yc.31945$A91.27814@okepread02... JAXAshby wrote: glenn, just where is it you found you "facts" that "a medium displacement boat" has 2,866.66666666 pounds of drag? From the VPP diagrams and backup data on my boat, the VPP for a Beneteau First 47, C.A. Marchaj's "Sail Performance" and working backwards from Dave Gerr's figures. The VPPs were run with standard and Gori folding 3 bladed props and showed from 12 to 15% increased speeds with the folding props up to about 80% of the first reef point. 20 miles a day is a 15% improvement on a base 5.6 knot cruising speed and you are correct that folding props make the most difference in light air. Reducing drag has the advantage over adding sail area in that it does not add to heeling moment. BTW, Gori, Martec, Brunton/Varifold and others make 3 blade folders. Volvo even makes a 4 bladed folder. Now, you can continue to rant and make an ass of yourself as usual but that is all I have to say about it. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Uh huh, and the point would be?
"JAXAshby" wrote in message ... Rosalie, your prop was also turning while you were running the engine. that alone is one hell of a drag. "Paul L" wrote: You will definitely will see a decent speed improvement under sail with a folding prop. Depending on the prop you buy, you should see better power/control in reverse too. They are very reliable now, so I don't think that is a down side. The biggest downside is their cost. I have a Max prop and think it great. Paul www.jcruiser.org "MLapla4120" wrote in message ... I'm going to re-power soon and am also going to get new shaft and prop. It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] grandma Rosalie |
now, THAT is an informed response.
From: "Paul L" Date: 8/28/2004 2:01 PM Eastern Daylight Time Message-id: nM3Yc.321$6q.104@trnddc06 bite me. "JAXAshby" wrote in message ... Its real easy to test, as I can get my folding 3 blade to stay open. I can see the boat speed, then have it fold and measure the speed. It is significant. If the MIT tests say otherwise then they are not testing reality - wanna guess what errors they made in the test or you in the interpretation??. sure, paul lever knows more testing props than MIT. good on ya, paul. Paul www.jcruiser.org "JAXAshby" wrote in message ... You will definitely will see a decent speed improvement under sail with a folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? |
Glenn, how does it feel to have a fish hook in your mouth?
the marketing people done did snag you. 170# at 5 knots is 85# at 2.5 knots is 42# a 1.25 knots. For a fixed ***three*** blade prop. In other words, zip. In fact, a two blade at 5 knots was IIRC about 75# and a two blade behind the keel wwas about 45#. In other words, "You how the f*&*% much to gain 0.05 knots speed??" And, that damned feathering three blade cost you HOW much in forward speed because the blades are flat? Folding props are for race boat boats, and boat owners who like to brag how much *they* spent on their boat. Sorta like the suburban home owner bragging about spending $400/week to have his LARGE swimming pool cleaned. btw, glenn, Dave Gerr rehashes other people's writings without all that much verification. glenn, just where is it you found you "facts" that "a medium displacement boat" has 2,866.66666666 pounds of drag? From the VPP diagrams and backup data on my boat, the VPP for a Beneteau First 47, C.A. Marchaj's "Sail Performance" and working backwards from Dave Gerr's figures. The VPPs were run with standard and Gori folding 3 bladed props and showed from 12 to 15% increased speeds with the folding props up to about 80% of the first reef point. 20 miles a day is a 15% improvement on a base 5.6 knot cruising speed and you are correct that folding props make the most difference in light air. Reducing drag has the advantage over adding sail area in that it does not add to heeling moment. BTW, Gori, Martec, Brunton/Varifold and others make 3 blade folders. Volvo even makes a 4 bladed folder. Now, you can continue to rant and make an ass of yourself as usual but that is all I have to say about it. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
There aren't too many other things you can do to gain that much performance
that easily. sure there are. you can clean the bottom of your boat. you can thoroughly fair the hull before you bottom paint. you can take 500# of useless junk out of your boat. you can trim the sails. you can buy better sails. you can take down your dodger and/or bimini and/or 3 of your 8 solar panels. you can use a hank on jib instead of a roller furled jib. you can use a vinyl bottom paint. you can do polars on your boat to sail it smarter. you can move your anchor and 275 foot of chain to the center of the boat. you can sail more so you need 300# less fuel onboard. ----------------------- you can install a two blade prop ------------------------- which i damned cheap and damned effective. you can line up your prop with the keel. To name just a few. Paul "Glenn Ashmore" wrote in message news:OI2Yc.31945$A91.27814@okepread02... JAXAshby wrote: glenn, just where is it you found you "facts" that "a medium displacement boat" has 2,866.66666666 pounds of drag? From the VPP diagrams and backup data on my boat, the VPP for a Beneteau First 47, C.A. Marchaj's "Sail Performance" and working backwards from Dave Gerr's figures. The VPPs were run with standard and Gori folding 3 bladed props and showed from 12 to 15% increased speeds with the folding props up to about 80% of the first reef point. 20 miles a day is a 15% improvement on a base 5.6 knot cruising speed and you are correct that folding props make the most difference in light air. Reducing drag has the advantage over adding sail area in that it does not add to heeling moment. BTW, Gori, Martec, Brunton/Varifold and others make 3 blade folders. Volvo even makes a 4 bladed folder. Now, you can continue to rant and make an ass of yourself as usual but that is all I have to say about it. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
I don't know if the prop spinning under sail has more drag than one (a
three blade one) that is stationary but not feathered, It does, but quite a bit. |
uhhhhhhhh, mmc? which word didn't you understand?
From: "MMC" Date: 8/28/2004 3:34 PM Eastern Daylight Time Message-id: Uh huh, and the point would be? "JAXAshby" wrote in message ... Rosalie, your prop was also turning while you were running the engine. that alone is one hell of a drag. "Paul L" wrote: You will definitely will see a decent speed improvement under sail with a folding prop. Depending on the prop you buy, you should see better power/control in reverse too. They are very reliable now, so I don't think that is a down side. The biggest downside is their cost. I have a Max prop and think it great. Paul www.jcruiser.org "MLapla4120" wrote in message ... I'm going to re-power soon and am also going to get new shaft and prop. It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] grandma Rosalie |
Wanna guess just how much powered is required to pull 170# at 5 knots?
about 2-1/2 hp. that's a LOT, isn't it. |
There is another J36 at our marina, which has a fixed prop. It is
astonishingly slower than our boat. I know the sails aren't identical, but we have caught them going to windward when we didn't even have a jib hoisted. Their bottom is cleaner or as clean.On Sat, 28 Aug 2004 05:02:39 GMT, "Paul L" wrote: Its real easy to test, as I can get my folding 3 blade to stay open. I can see the boat speed, then have it fold and measure the speed. It is significant. If the MIT tests say otherwise then they are not testing reality - wanna guess what errors they made in the test or you in the interpretation??. Paul www.jcruiser.org "JAXAshby" wrote in message ... You will definitely will see a decent speed improvement under sail with a folding prop no, you won't. folding props only hve value for racing boats, where 2 seconds a mile means the difference between 2nd place and 6th. According to MIT tests, a folding prop means a savings of a mere 170 pounds drag at 5 knots (or 40 pounds drag at 2-1/2 knots, or 10 pounds drag at 1-1/4 knots) over a --------- three ------------ blade prop. ***Much*** less with compared to a two-blade, and even less compared to a two-blade rotated verticle behind the keel. Wanna guess just how much powered is required to pull 170# at 5 knots? Rodney Myrvaagnes NYC We have achieved faith-based science, faith-based economics, faith-based law enforcement, and faith-based missile defense. What's next? Faith-based air traffic control? |
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Subject: What are the pros and cons of a folding prop?
From: Rosalie B. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] grandma Rosalie Question. Your engine was running but you were in neutral gear. Why wasn't the prop feathered? i.e., does the prop "unfeather" when the engine starts or when you put it in gear? What causes the prop to feather? This is an area I'm not familiar with, though I frequently use VP/CP props. Shen |
(Shen44) wrote:
Subject: What are the pros and cons of a folding prop? From: Rosalie B. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] Question. Your engine was running but you were in neutral gear. Why wasn't the prop feathered? i.e., does the prop "unfeather" when the engine starts or when you put it in gear? What causes the prop to feather? This is an area I'm not familiar with, though I frequently use VP/CP props. I don't know what a VP/CP prop is. When our engine is running the shaft is spinning because we have a Borg-Warner transmission. Our shaft spins whenever the engine is on regardless whether it is neutral or not. The prop feathers when the engine is turned off and the shaft stops spinning. The stopping of the shaft spinning feathers the prop if I understand it correctly. You really wouldn't want the prop feathered if the engine was on - if it feathered when you went through neutral when docking or something it would be very awkward. grandma Rosalie |
putting a folding prop on Westsail is like putting Nikes on an obese man.
The person that inquired has a Westsail. This is not a racing boat. He wants to sail faster WITH the dodger and bimini, and with the roller furled jib and with the solar panels and the fuel etc. He isn't racing. Just because these are all things that can make a boat go faster doesn't mean that they are viable options for a cruising sailboat nor that the folding prop isn't also an option that he can use effectively. grandma Rosalie |
The other way of looking at it is that the Westsail needs all the help it can get ;-)) Bob Larder JAXAshby wrote: putting a folding prop on Westsail is like putting Nikes on an obese man. The person that inquired has a Westsail. This is not a racing boat. He wants to sail faster WITH the dodger and bimini, and with the |
Back in my racing days I used a Martec II folding prop. It I remember right
(Martec recommended) it was a 14x12 and replaced a 16x10 2 bladed and worked ok. It was on a Yanmar 2GM20F. Less power in forward and significantly less power in reverse. You need to be much more aggressive in reverse when docking. Lots more walk to port also. Still had to line up the shaft (I used the keyway since the two were inline) to get it to fold in light air since the weight of the prop would cause it to open. I have even heard of folks jumping overboard and putting a rubber band around them to keep it closed. If it got fouled with growth so it would not open all the way it would let you know by vibrating when trying to go forward. This is just some of the things you need to put up with when you race. I believe it did fold when going from forward to reverse. You could hear it go "clunk." With my current cruising boat I would look at feathering props if I were to upgrade. I need a good reverse and these provide it. I guess the question is did it help? I would guess so. Could I tell? No not really. I agree with JAX. There is quite a bit of stuff you can do to the bottom of the boat for speed. But bolting on a folding prop is definitely easy. The other speed improvements require hard work. "Rosalie B." wrote in message ... (Shen44) wrote: Subject: What are the pros and cons of a folding prop? From: Rosalie B. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] Question. Your engine was running but you were in neutral gear. Why wasn't the prop feathered? i.e., does the prop "unfeather" when the engine starts or when you put it in gear? What causes the prop to feather? This is an area I'm not familiar with, though I frequently use VP/CP props. I don't know what a VP/CP prop is. When our engine is running the shaft is spinning because we have a Borg-Warner transmission. Our shaft spins whenever the engine is on regardless whether it is neutral or not. The prop feathers when the engine is turned off and the shaft stops spinning. The stopping of the shaft spinning feathers the prop if I understand it correctly. You really wouldn't want the prop feathered if the engine was on - if it feathered when you went through neutral when docking or something it would be very awkward. grandma Rosalie |
"Rick" wrote:
Back in my racing days I used a Martec II folding prop. It I remember right I have been told that a folding prop and a feathering prop are different. I haven't seen a folding prop, so I don't know what the difference is. (Martec recommended) it was a 14x12 and replaced a 16x10 2 bladed and worked ok. It was on a Yanmar 2GM20F. Less power in forward and significantly less power in reverse. You need to be much more aggressive in reverse when docking. Lots more walk to port also. Still had to line up the shaft (I used the keyway since the two were inline) to get it to fold in light air since the weight of the prop would cause it to open. I have even heard of folks jumping overboard and putting a rubber band around them to keep it closed. If it got fouled with growth so it would not open all the way it would let you know by vibrating when trying to go forward. This is just some of the things you need to put up with when you race. Yes, I sometimes go over to check and see if the prop is moving freely and to wipe or chip off growth. We had a 3 blade prop to start with, and we put on a 3 blade feathering prop that was as close to the diameter and pitch of the old prop as possible. I believe it did fold when going from forward to reverse. You could hear it go "clunk." This is transmission dependent to a certain extent. Our transmission goes clunk when going from forward to reverse. I can't hear the prop feather. The only way we know if it has not feathered is that we can still hear the shaft rotating. With my current cruising boat I would look at feathering props if I were to upgrade. I need a good reverse and these provide it. I guess the question is did it help? I would guess so. Could I tell? No not really. I agree with JAX. There is quite a bit of stuff you can do to the bottom of the boat for speed. But bolting on a folding prop is definitely easy. The other speed improvements require hard work. "Rosalie B." wrote in message .. . (Shen44) wrote: Subject: What are the pros and cons of a folding prop? From: Rosalie B. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] Question. Your engine was running but you were in neutral gear. Why wasn't the prop feathered? i.e., does the prop "unfeather" when the engine starts or when you put it in gear? What causes the prop to feather? This is an area I'm not familiar with, though I frequently use VP/CP props. I don't know what a VP/CP prop is. When our engine is running the shaft is spinning because we have a Borg-Warner transmission. Our shaft spins whenever the engine is on regardless whether it is neutral or not. The prop feathers when the engine is turned off and the shaft stops spinning. The stopping of the shaft spinning feathers the prop if I understand it correctly. You really wouldn't want the prop feathered if the engine was on - if it feathered when you went through neutral when docking or something it would be very awkward. grandma Rosalie grandma Rosalie |
Rosalie B. wrote:
I don't know what a VP/CP prop is. variable pitch/constant pitch the former you can feather, the latter you can't |
What I understand from any of your postings is that you are incredibly
insecure, misinformed, and HAVE to have the last word. My point was, Rosalie had performed her own test on drag with prop folded and unfolded and stated her results. You're pointing out that her prop was turning and creating drag really didn't support your fantasy position in this discussion. My fixed prop turns too, when in forward, reverse, or in idle and sailing. In fact, the only time it doesn't turn is when the boat is dockside. Amazing, huh? I've avoided responding to your posts for years, but couldn't when you lamely tried to make Rosalie look bad when all she was doing was participating in a discussion (which she understands better than you do). "JAXAshby" wrote in message ... uhhhhhhhh, mmc? which word didn't you understand? From: "MMC" Date: 8/28/2004 3:34 PM Eastern Daylight Time Message-id: Uh huh, and the point would be? "JAXAshby" wrote in message ... Rosalie, your prop was also turning while you were running the engine. that alone is one hell of a drag. "Paul L" wrote: You will definitely will see a decent speed improvement under sail with a folding prop. Depending on the prop you buy, you should see better power/control in reverse too. They are very reliable now, so I don't think that is a down side. The biggest downside is their cost. I have a Max prop and think it great. Paul www.jcruiser.org "MLapla4120" wrote in message ... I'm going to re-power soon and am also going to get new shaft and prop. It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] grandma Rosalie |
I don't know what a VP/CP prop is. Variable pitch/controlable pitch. I use the terms interchangeably, but as you'll see, others use them slightly differently. When our engine is running the shaft is spinning because we have a Borg-Warner transmission. Our shaft spins whenever the engine is on regardless whether it is neutral or not. The prop feathers when the engine is turned off and the shaft stops spinning. The stopping of the shaft spinning feathers the prop if I understand it correctly. You really wouldn't want the prop feathered if the engine was on - if it feathered when you went through neutral when docking or something it would be very awkward. Interesting, thanks for the info. I would wonder if once you were underway and using your prop, even going from ahead to astern (unless you had a shaft brake) that the shaft would generally continue to rotate on it's own, keeping the prop "unfeathered", though I can see where the manufacturer might want to guarantee it would stay that way (just clarifying in my own mind G). Shen |
(Shen44) wrote:
I don't know what a VP/CP prop is. Variable pitch/controlable pitch. I use the terms interchangeably, but as you'll see, others use them slightly differently. When our engine is running the shaft is spinning because we have a Borg-Warner transmission. Our shaft spins whenever the engine is on regardless whether it is neutral or not. The prop feathers when the engine is turned off and the shaft stops spinning. The stopping of the shaft spinning feathers the prop if I understand it correctly. You really wouldn't want the prop feathered if the engine was on - if it feathered when you went through neutral when docking or something it would be very awkward. Interesting, thanks for the info. We have a Max-Prop BTW. I would wonder if once you were underway and using your prop, even going from ahead to astern (unless you had a shaft brake) that the shaft would generally continue to rotate on it's own, keeping the prop "unfeathered", though I can see where the manufacturer might want to guarantee it would stay that way (just clarifying in my own mind G). I'm not sure that I understand this question, or if it is a question, but in our particular configuration (which is NOT the norm) with a Borg-Warner transmission, the shaft cannot be stopped from turning by putting the gear shift lever into reverse or neutral (whether the engine is running or not) which I guess is what is done on most kinds of engine/transmission linkages. We don't have a shaft brake. [I do know one man who DOES stop the shaft rotation when under sail with vice grips but that involves pulling up the cockpit hatch covers and getting down into the engine room both to start and stop the shaft rotation.] In the beginning, we tried to ease the engine into neutral and then shut it down, but the prop would not feather doing it that way. Some people go overboard the other way and rev the engine way up before they cut the power, but that isn't necessary. All that is necessary is that you not throttle way back before you cut the engine. grandma Rosalie S/V RosalieAnn, Leonardtown, MD CSY 44 WO #156 http://home.mindspring.com/~gmbeasley/id2.html |
On Sat, 28 Aug 2004 12:48:25 -0400, Glenn Ashmore
wrote: 20 miles a day is a 15% improvement on a base 5.6 knot cruising speed and you are correct that folding props make the most difference in light air. Reducing drag has the advantage over adding sail area in that it does not add to heeling moment. BTW, Gori, Martec, Brunton/Varifold and others make 3 blade folders. Volvo even makes a 4 bladed folder. Now, you can continue to rant and make an ass of yourself as usual but that is all I have to say about it. For what it's worth: Buddy of mine with a steel Wallstrom-designed (partner to Brewer) 1979 ketch popped for a three-bladed AutoProp, a feathering design. He had to haul out for many reasons: 1) to confirm the exact geometry of his hull around the shaft; 2) to cut back his rudder at that point for the install; and 3) to get the prop itself on. 1) was because it's essentially a custom casting, and NOT cheap (about $3,500 Cdn.). After three seasons now, he's happy as a clam with his decision and outlay. He says the following: Advantages: Bigger prop, better bite and power curve. He's got a 35 HP Volvo (probably 15-25 HP too small for a 28,000 lb. boat), but according to him, the power he transmits to the prop is greatly increased. His top speed without redlining has gone from 6.5 to 8.2 knots, or approximately hull speed. He says he gains 1/2 knot due to the self-feathering action, a significant gain in typical light Lake Ontario air for this essentially blue-water cruiser. He backs down (after a quick rev to feather out the blades) far more effectively now. He stops far more rapidly. His docking is far more controlled. He can move his heavy, trad. keeled boat like a minivan now. It's quite interesting to see. Disadvantages: The cones in his transmission have been wearing far more quickly and have required replacement. He can handle this himself as a repair, so it's more an annoyance than a tragedy, and spares from Volvo are pricey. He figures that shifting the gears with a bigger, heavier prop is causing wear and tear beyond the engine spec. You can hear the "clunk" of his shifting outside the boat, actually. He is consulting with a marine engineer to determine a better course of action, but he is leaning towards a shock-absorbing coupler and a thrust bearing designed to isolate the engine transmission more effectively from the sheer inertia of this otherwise fine prop. Overall, he is so happy with the performance, however, both under sail and power, that he would consider getting a new diesel to make full use of the prop, rather than sticking with the small but still viable diesel that perhaps doesn't have the beef at the back end to cope with God's Own Feathering Prop G. Hope this little tale helps. R. |
rhys, hate to tell you this, but an Auto-Prop doesn't feather.
Still, the clown spent $3,500 Cdn, so you gotta expect him to tell you *something*. 20 miles a day is a 15% improvement on a base 5.6 knot cruising speed and you are correct that folding props make the most difference in light air. Reducing drag has the advantage over adding sail area in that it does not add to heeling moment. BTW, Gori, Martec, Brunton/Varifold and others make 3 blade folders. Volvo even makes a 4 bladed folder. Now, you can continue to rant and make an ass of yourself as usual but that is all I have to say about it. For what it's worth: Buddy of mine with a steel Wallstrom-designed (partner to Brewer) 1979 ketch popped for a three-bladed AutoProp, a feathering design. He had to haul out for many reasons: 1) to confirm the exact geometry of his hull around the shaft; 2) to cut back his rudder at that point for the install; and 3) to get the prop itself on. 1) was because it's essentially a custom casting, and NOT cheap (about $3,500 Cdn.). After three seasons now, he's happy as a clam with his decision and outlay. He says the following: Advantages: Bigger prop, better bite and power curve. He's got a 35 HP Volvo (probably 15-25 HP too small for a 28,000 lb. boat), but according to him, the power he transmits to the prop is greatly increased. His top speed without redlining has gone from 6.5 to 8.2 knots, or approximately hull speed. He says he gains 1/2 knot due to the self-feathering action, a significant gain in typical light Lake Ontario air for this essentially blue-water cruiser. He backs down (after a quick rev to feather out the blades) far more effectively now. He stops far more rapidly. His docking is far more controlled. He can move his heavy, trad. keeled boat like a minivan now. It's quite interesting to see. Disadvantages: The cones in his transmission have been wearing far more quickly and have required replacement. He can handle this himself as a repair, so it's more an annoyance than a tragedy, and spares from Volvo are pricey. He figures that shifting the gears with a bigger, heavier prop is causing wear and tear beyond the engine spec. You can hear the "clunk" of his shifting outside the boat, actually. He is consulting with a marine engineer to determine a better course of action, but he is leaning towards a shock-absorbing coupler and a thrust bearing designed to isolate the engine transmission more effectively from the sheer inertia of this otherwise fine prop. Overall, he is so happy with the performance, however, both under sail and power, that he would consider getting a new diesel to make full use of the prop, rather than sticking with the small but still viable diesel that perhaps doesn't have the beef at the back end to cope with God's Own Feathering Prop G. Hope this little tale helps. R. |
mmc, go away. you are a lying sack of squat trying to get people hurt. go
away. From: "MMC" Date: 8/29/2004 12:01 PM Eastern Daylight Time Message-id: What I understand from any of your postings is that you are incredibly insecure, misinformed, and HAVE to have the last word. My point was, Rosalie had performed her own test on drag with prop folded and unfolded and stated her results. You're pointing out that her prop was turning and creating drag really didn't support your fantasy position in this discussion. My fixed prop turns too, when in forward, reverse, or in idle and sailing. In fact, the only time it doesn't turn is when the boat is dockside. Amazing, huh? I've avoided responding to your posts for years, but couldn't when you lamely tried to make Rosalie look bad when all she was doing was participating in a discussion (which she understands better than you do). "JAXAshby" wrote in message ... uhhhhhhhh, mmc? which word didn't you understand? From: "MMC" Date: 8/28/2004 3:34 PM Eastern Daylight Time Message-id: Uh huh, and the point would be? "JAXAshby" wrote in message ... Rosalie, your prop was also turning while you were running the engine. that alone is one hell of a drag. "Paul L" wrote: You will definitely will see a decent speed improvement under sail with a folding prop. Depending on the prop you buy, you should see better power/control in reverse too. They are very reliable now, so I don't think that is a down side. The biggest downside is their cost. I have a Max prop and think it great. Paul www.jcruiser.org "MLapla4120" wrote in message ... I'm going to re-power soon and am also going to get new shaft and prop. It seems that in my boat class (Westsail 32), some people are going to folding props to help speed under sail. I'm for increased speed, but also want reliability. My current bronze propeller is pitted and old. Every time I turn around and look at it, it is full of sea growth. That makes me think I'm getting poor performance. So, I'm for an improvement, but I am unsure of what kind. Any opinions from boaters that have encountered this situation would be appreciated. We have a feathering prop (vs a folding prop) and we do get an increase of about 1/2 knot under sail, and it also backs better under power. I haven't tried to quantify the backing under power - it is just what we feel. Disadvantages are - you lose a bit of power forward because the blades are flat and the prop takes a bit more maintenance than a fixed prop. [We were sailing but had the engine on in neutral so the prop was not feathered - we were running the refrigeration- and when we had finished that, we turned off the engine and feathered the prop, and our speed increased 1/2 knot - same wind and current. Now I know this is not a completely scientific test, but it is significant to us. There are also people in our group who did tests with a fixed prop over a measured course, and then did the same tests with a folding prop over the same course and found a similar result.] grandma Rosalie |
now, THAT is an informed response.
"JAXAshby" wrote in message ... mmc, go away. you are a lying sack of squat trying to get people hurt. go away. |
On 30 Aug 2004 03:34:57 GMT,
JAXAshby wrote: rhys, hate to tell you this, but an Auto-Prop doesn't feather. The blades rotate until they are inline with the shaft axis, how is this not feathering? Still, the clown spent $3,500 Cdn, so you gotta expect him to tell you *something*. What would have done the job as well, for less money? -- Jim Richardson http://www.eskimo.com/~warlock 'Windows' really does make a fine swear word, representing all that's taboo and awful - just like '****', '****', etc." -- Mark Hughes, sdm |
paul, AC is a newbie who has been deliberately trying to harm people with his
nonsense posts. AC is the kind of person you tell to go pull a fake gun on a cop late at night. AC, has no value in any fashion. now, THAT is an informed response. "JAXAshby" wrote in message ... mmc, go away. you are a lying sack of squat trying to get people hurt. go away. |
The blades rotate until they are inline with the shaft axis, how is this
not feathering? take a look at the blades. they rotate and thus *reduce* drag, but they certainly don't "feather". |
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