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#1
posted to rec.boats.cruising
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PerfectPitch prop from CDI
Anybody have experience with these? I am about to replace my fixed 3
bladed prop on my 8.5M S2. This looks like a potentially good candidate replacement because they have already figured out which prop works for a given boat and because they say they can put a larger prop on with their "Extendo" system. I am a little worried about the plastic of this prop not being able to take my aggressive barnacle removal method. Is it easy enough to remove that re-painting it every so-often works? My old bronze prop has succumbed to corrosion and many impacts with oyster beds and with a Laser mast in the water. Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag. How does one do this? Do you simply mark the prop shaft inside the boat and then rotate it till your mark is in the right place? This really seems like a PITA considering the gawdawful engine installation on most boats. Even on my boat it requires removing an engine panel and peering down into a dark space. Is there any other system? Would the prop left in neutral auto-rotate to the lowest drag position (I have never had a two blade prop so I dont know) and stay? Could I attach a magnet to the shaft so that it engages a magnetic reed switch (non-contact) to tell me when it is in correct position? Can you get it in correct position by "bumping" the start switch? |
#2
posted to rec.boats.cruising
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PerfectPitch prop from CDI
Frogwatch brought forth on stone tablets:
Anybody have experience with these? I am about to replace my fixed 3 bladed prop on my 8.5M S2. This looks like a potentially good candidate replacement because they have already figured out which prop works for a given boat and because they say they can put a larger prop on with their "Extendo" system. I am a little worried about the plastic of this prop not being able to take my aggressive barnacle removal method. Is it easy enough to remove that re-painting it every so-often works? My old bronze prop has succumbed to corrosion and many impacts with oyster beds and with a Laser mast in the water. Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag. How does one do this? Do you simply mark the prop shaft inside the boat and then rotate it till your mark is in the right place? This really seems like a PITA considering the gawdawful engine installation on most boats. Even on my boat it requires removing an engine panel and peering down into a dark space. Is there any other system? Would the prop left in neutral auto-rotate to the lowest drag position (I have never had a two blade prop so I dont know) and stay? Could I attach a magnet to the shaft so that it engages a magnetic reed switch (non-contact) to tell me when it is in correct position? Can you get it in correct position by "bumping" the start switch? If you want the prop to *stay* lined up with the keel, you'll need a shaft lock. When you install the shaft lock, set it up so that the prop is properly lined up with the lock engaged. see http://www.shaftlok.com/ bob s/v Eolian Seattle |
#3
posted to rec.boats.cruising
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PerfectPitch prop from CDI
RW Salnick brought forth on stone tablets:
Frogwatch brought forth on stone tablets: Anybody have experience with these? I am about to replace my fixed 3 bladed prop on my 8.5M S2. This looks like a potentially good candidate replacement because they have already figured out which prop works for a given boat and because they say they can put a larger prop on with their "Extendo" system. I am a little worried about the plastic of this prop not being able to take my aggressive barnacle removal method. Is it easy enough to remove that re-painting it every so-often works? My old bronze prop has succumbed to corrosion and many impacts with oyster beds and with a Laser mast in the water. Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag. How does one do this? Do you simply mark the prop shaft inside the boat and then rotate it till your mark is in the right place? This really seems like a PITA considering the gawdawful engine installation on most boats. Even on my boat it requires removing an engine panel and peering down into a dark space. Is there any other system? Would the prop left in neutral auto-rotate to the lowest drag position (I have never had a two blade prop so I dont know) and stay? Could I attach a magnet to the shaft so that it engages a magnetic reed switch (non-contact) to tell me when it is in correct position? Can you get it in correct position by "bumping" the start switch? If you want the prop to *stay* lined up with the keel, you'll need a shaft lock. When you install the shaft lock, set it up so that the prop is properly lined up with the lock engaged. see http://www.shaftlok.com/ bob s/v Eolian Seattle (stupidly replying to my own message) Well, maybe your transmission doesn't freewheel... (I have a Borg Warner Velvet Drive, which is kind of like an automatic - regardless of the shift lever position, the output shaft freewheels when the engine is not running). If your transmission holds the shaft, then your suggestions seem like good answers, if the shaft is inaccessible (doh! It's a SAILboat). Beware of corrosion and salt spray from the stuffing box in whatever you set up. bob s/v Eolian Seattle |
#4
posted to rec.boats.cruising
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PerfectPitch prop from CDI
On Oct 15, 6:57 am, Frogwatch wrote:
...Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag.... Correct me if I am wrong but I believe the S2 8.5 is a fin keel, spade rudder set-up with the prop just ahead of the rudder. In this case there will seldom be any drag reduction advantage to aligning the blades of the prop with the keel. -- Tom. |
#5
posted to rec.boats.cruising
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PerfectPitch prop from CDI
On Oct 15, 3:45 pm, " wrote:
On Oct 15, 6:57 am, Frogwatch wrote: ...Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag.... Correct me if I am wrong but I believe the S2 8.5 is a fin keel, spade rudder set-up with the prop just ahead of the rudder. In this case there will seldom be any drag reduction advantage to aligning the blades of the prop with the keel. -- Tom. why not? |
#6
posted to rec.boats.cruising
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PerfectPitch prop from CDI
On Oct 15, 10:10 am, Frogwatch wrote:
On Oct 15, 3:45 pm, " wrote: On Oct 15, 6:57 am, Frogwatch wrote: ...Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag.... Correct me if I am wrong but I believe the S2 8.5 is a fin keel, spade rudder set-up with the prop just ahead of the rudder. In this case there will seldom be any drag reduction advantage to aligning the blades of the prop with the keel. -- Tom. why not? Because, unless the leeway angle is near zero the prop will not be in the keel's wake. In cases where the prop is right behind the keel or is in a cut-out in a two bladed prop can be hidden behind the keel or skeg by aligning it. In your case the prop is a long way from the keel and even a small amount of leeway will move it into the free stream and in any case if the keel is well designed and in good condition the wake two cord lengths back will be insignificant. So, in your case alignment isn't likely to make a difference you can measure most of the time. If you are concerned about drag I would recommend a two bladed geared folding prop. -- Tom. |
#7
posted to rec.boats.cruising
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PerfectPitch prop from CDI
On 2007-10-15 12:57:14 -0400, Frogwatch said:
Anybody have experience with these? I am about to replace my fixed 3 bladed prop on my 8.5M S2. CDI really got my respect when they would NOT sell me one of those blades because they hadn't yet gotten the numbers they advertise with the blade they were developing for our engine. Have you held one in your hand? A work of art. I strongly believe that your experience with that prop will exceed their promises. Take their recommendation of anti-growth system. And get the biggest prop that will fit. Don't bother trying to hide the prop behind the fin keel or strut. Just stop it from turning some how. -- Jere Lull Tanzer 28 #4 out of Tolchester, MD Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/ Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/ |
#8
posted to rec.boats.cruising
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PerfectPitch prop from CDI
On Mon, 15 Oct 2007 21:20:57 -0000, "
wrote: If you are concerned about drag I would recommend a two bladed geared folding prop. The earliest screw propellor equipped ships had props you could raise out of the water to avoid drag while under sail, which was nearly all the time. Casady |
#9
posted to rec.boats.cruising
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PerfectPitch prop from CDI
Frogwatch wrote:
Anybody have experience with these? I am about to replace my fixed 3 bladed prop on my 8.5M S2. This looks like a potentially good candidate replacement because they have already figured out which prop works for a given boat and because they say they can put a larger prop on with their "Extendo" system. I am a little worried about the plastic of this prop not being able to take my aggressive barnacle removal method. Is it easy enough to remove that re-painting it every so-often works? My old bronze prop has succumbed to corrosion and many impacts with oyster beds and with a Laser mast in the water. Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag. How does one do this? Do you simply mark the prop shaft inside the boat and then rotate it till your mark is in the right place? This really seems like a PITA considering the gawdawful engine installation on most boats. Even on my boat it requires removing an engine panel and peering down into a dark space. Is there any other system? Would the prop left in neutral auto-rotate to the lowest drag position (I have never had a two blade prop so I dont know) and stay? Could I attach a magnet to the shaft so that it engages a magnetic reed switch (non-contact) to tell me when it is in correct position? Can you get it in correct position by "bumping" the start switch? Ever heard of a thing called paint? You can even mark a prop shaft with it. I won't charge for this piece of wisdom as I learned it about fifty years ago. (and the piant is still there!) You could easily fit a small glass spyhole in the cockpit floor. However, some sailors would argue that allowing the shaft to rotate in neutral causes less drag than locking it in the upright position, particularly on a modern fin/skeg design. Dennis. Dennis. |
#10
posted to rec.boats.cruising
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PerfectPitch prop from CDI
On Oct 16, 4:29 am, "Dennis Pogson"
wrote: Frogwatch wrote: Anybody have experience with these? I am about to replace my fixed 3 bladed prop on my 8.5M S2. This looks like a potentially good candidate replacement because they have already figured out which prop works for a given boat and because they say they can put a larger prop on with their "Extendo" system. I am a little worried about the plastic of this prop not being able to take my aggressive barnacle removal method. Is it easy enough to remove that re-painting it every so-often works? My old bronze prop has succumbed to corrosion and many impacts with oyster beds and with a Laser mast in the water. Now, one of the advantages of a 2 blade prop is that you can align it with the keel for lower drag. How does one do this? Do you simply mark the prop shaft inside the boat and then rotate it till your mark is in the right place? This really seems like a PITA considering the gawdawful engine installation on most boats. Even on my boat it requires removing an engine panel and peering down into a dark space. Is there any other system? Would the prop left in neutral auto-rotate to the lowest drag position (I have never had a two blade prop so I dont know) and stay? Could I attach a magnet to the shaft so that it engages a magnetic reed switch (non-contact) to tell me when it is in correct position? Can you get it in correct position by "bumping" the start switch? Ever heard of a thing called paint? You can even mark a prop shaft with it. I won't charge for this piece of wisdom as I learned it about fifty years ago. (and the piant is still there!) You could easily fit a small glass spyhole in the cockpit floor. However, some sailors would argue that allowing the shaft to rotate in neutral causes less drag than locking it in the upright position, particularly on a modern fin/skeg design. Dennis. Dennis. I appreciate y'alls advice, especially tsmwebb and Jere Lull. For those who suggest a folding/feathering prop, I do not consider this to really be an option due to the extreme fouling conditions I encounter. A friend who works in a boat yard says most he sees are too fouled to work around here. Cost is another issue for a boat that is 27 yrs old. tsmwebb points out that the flow is rarely directly fore and aft and I admit this had never occurred to me, however, is he correct? If he is correct, I would not expect a 3 bladed prop to cause much loss of sailing speed. As far as using paint and a sight glass as Pogson suggests, this was my initial idea but drilling a hole in my cockpit floor for the sight seems sacriligeous. I could easily rig up the magnet and reed switch I described. However, how easy is it to stop a prop in a given position unless you rotatre the shaft by hand? Can you "bump" it with the starter to a given position? I cannot believe that most sailors take off their engine cover to peer down at the prop shaft whenever they sail to align the prop with the keel. |
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