Re: [Cal_Boats] Fixed vs. rotating propeller (was : Gear level when sailing?)

Jerry, think about it....... as the boat moves forward it "pulls" the prop through the water.... hydrodynamic forces act on free-wheeling prop to spin it. Since the prop is in essence, like a screw, it will "screw" it's way through the water, revolving the exact same way it would if the engine was turning the prop to move the boat forward, in other words.... the prop will turn in a "forward" direction as the boat sails forward. It would be impossible for the motion of the boat while moving forward to cause the prop to spin in "reverse". Again, if the prop turns in a clockwise direction while the engine is driving the boat forward, then the prop will spin in a clockwise direction as it free-wheels in neutral while the boat moves forward under sail. Drag is created by the slippage of the prop (it will be turning slower under sail than it would at the same speed under power), and friction from the cutlass bearing, stuffing box, transmission, etc. Still, it will rotate in the same direction as if the engine were providing the rotation to drive the boat in that direction. If you were to let your car coast down a hill in neutral, the tires still rotate in the same direction as they would if the engine were moving the car in that direction, the coasting car would be slowed (slightly) by the friction in the drive line (axles to differential to drive shaft to transmission), basically the same as dragging a free-wheeling prop through the water as you sail. A Helicopter in free-fall, ie: engine is not turning the rotor(s), will be slowed by the fact that the free-wheeling rotor will be spinning slower than it would be if it were powered, again due to friction in the rotating assembly. Rod Johnson, "SUNBIRD" 1979 O'DAY DS II #10201 was: co-owner of "NODROG" 1970 CAL 21 #285 On Fri, 17 Apr 2015 23:30:26 +0000 (UTC) "Gerald Sobel so… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> writes: I guess the question is, is the prop rotating in the same direction in neutral as it is when it is being used to propel the boat? Empirically, one could stop the prop by putting it in gear, while sailing, and check the knot-meter, then let it free wheel in neutral, and see if the boat is going faster or slower. If the prop is rotating backwards when the boat is going forwards, it's likely creating hydrodynamic lift in the backwards direction, which is what a helicopter blade would do in free fall. If you don't have a shaft brake, I'm guessing letting it spin will slow you down, which is maybe counter intuitive, but then, sailing upwind is a wild and crazy idea too, but it's how birds get off the ground, and they won't bother arguing with you since they have better things to do. On Friday, April 17, 2015 9:43 AM, "George Barlow ge… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: OK, here�s my take. The apparent wind traversing the plane of the helicopter rotor adds momentum to the rotation of the rotor. The rotor blades produce lift. The controls of the helicopter can be used to increase the lift to �flare� the chopper for landing, in other words to add lift at landing to counteract the sink of the chopper due to gravity. If the prop in the water is locked, the water flowing through the plane of the prop just adds drag and turbulent flow. Drag bad. If the prop is allowed to spin, the force of the water through the plane of the blades imparts rotational force to the shaft. If the shaft is not engaged, it spins freely (subject to friction at stuffing box and bearings. If the friction is too much, it creates heat. So the trade off is do you want the force to spin the prop and create heat or do you want the force to hit the fixed prop and create drag. George Barlow Want to place your ad here? Advertise on United Online http://thirdpartyoffers.juno.com/TGL3141/5531bae31ca753ae3022fst03duc

So, from all I'm hearing, with my A4 I should just leave it in neutral to free wheel? david dobbs, Cal29 411 with A4 On Friday, April 17, 2015 9:01 PM, "rj… [at] juno.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: Jerry, think about it....... as the boat moves forward it "pulls" the prop through the water.... hydrodynamic forces act on free-wheeling prop to spin it. Since the prop is in essence, like a screw, it will "screw" it's way through the water, revolving the exact same way it would if the engine was turning the prop to move the boat forward, in other words.... the prop will turn in a "forward" direction as the boat sails forward. It would be impossible for the motion of the boat while moving forward to cause the prop to spin in "reverse".Again, if the prop turns in a clockwise direction while the engine is driving the boat forward, then the prop will spin in a clockwise direction as it free-wheels in neutral while the boat moves forward under sail. Drag is created by the slippage of the prop (it will be turning slower under sail than it would at the same speed under power), and friction from the cutlass bearing, stuffing box, transmission, etc. Still, it will rotate in the same direction as if the engine were providing the rotation to drive the boat in that direction.If you were to let your car coast down a hill in neutral, the tires still rotate in the same direction as they would if the engine were moving the car in that direction, the coasting car would be slowed (slightly) by the friction in the drive line (axles to differential to drive shaft to transmission), basically the same as dragging a free-wheeling prop through the water as you sail. A Helicopter in free-fall, ie: engine is not turning the rotor(s), will be slowed by the fact that the free-wheeling rotor will be spinning slower than it would be if it were powered, again due to friction in the rotating assembly. Rod Johnson, "SUNBIRD"1979 O'DAY DS II #10201was: co-owner of "NODROG"1970 CAL 21 #285 On Fri, 17 Apr 2015 23:30:26 +0000 (UTC) "Gerald Sobel so… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> writes: I guess the question is, is the prop rotating in the same direction in neutral as it is when it is being used to propel the boat? Empirically, one could stop the prop by putting it in gear, while sailing, and check the knot-meter, then let it free wheel in neutral, and see if the boat is going faster or slower. If the prop is rotating backwards when the boat is going forwards, it's likely creating hydrodynamic lift in the backwards direction, which is what a helicopter blade would do in free fall. If you don't have a shaft brake, I'm guessing letting it spin will slow you down, which is maybe counter intuitive, but then, sailing upwind is a wild and crazy idea too, but it's how birds get off the ground, and they won't bother arguing with you since they have better things to do. On Friday, April 17, 2015 9:43 AM, "George Barlow ge… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: OK, here’s my take. The apparent wind traversing the plane of the helicopter rotor adds momentum to the rotation of the rotor. The rotor blades produce lift. The controls of the helicopter can be used to increase the lift to “flare” the chopper for landing, in other words to add lift at landing to counteract the sink of the chopper due to gravity. If the prop in the water is locked, the water flowing through the plane of the prop just adds drag and turbulent flow. Drag bad. If the prop is allowed to spin, the force of the water through the plane of the blades imparts rotational force to the shaft. If the shaft is not engaged, it spins freely (subject to friction at stuffing box and bearings. If the friction is too much, it creates heat. So the trade off is do you want the force to spin the prop and create heat or do you want the force to hit the fixed prop and create drag. ___________________ George Barlow Want to place your ad here? 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The Universal Atomic Four has a modified Paragon transmission, which is mechanically engaged. It is lubricated by engine oil. Neutral allows the forward clutch plates to rotate, thus causing wear. By putting the gear in reverse, you stop rotation and wear. I still have several A4 transmissions and parts available. Which is more effective for less drag? I don't know, but why do aircraft "feather" a prop when it's engine is shut down?Many aircraft engines direct drive the prop, so if the engine stops, the prop stops. If the blades are in their normal position for pulling the plane, their blades are causing excessive drag. So, on many planes with variable pitch, the blades are turned sideways to minimize drag. If you have a Borg Warner Velvet Drive, which is hydraulically actuated, i.e. the engine drives a positive displacement pump which actuates the forward or reverse gear as chosen. When you are moving forward in the water without the engine running, the prop will rotate regardless of the position of the shift lever. While there is some "splash" lubrication and depending on engine angle the front bearings will get inadequate lubrication and will eventually be destroyed. An excellent device to lock your prop was available, the "Prop Lock" which locked the prop shaft when the engine was stopped. I have several Velvet Drives available, plus I have been rebuilding them for over 40 years. Some of you with older boats/engines may have the Paragon mechanical or hydraulic gear. They were discontinued several years ago and parts are very difficult to find. I have some old Paragons and parts. Some of you may have Hurth, ZF or Kanzaki gears. Most of these are mechanical. We do not repair them, just replace with a new one about each 1,500 hours. Check out "Dr. Diesel" on Foleyengine.com for his take on these, "one dollar an hour gears". The last about 1,500 hours and cost about $1,500. There are other options, eg. on my Cal Cruising 46, "Satori" which was built by and for Jack Jensen has a Luke Feathering Prop That is when the engine is stopped and you are sailing, the prop blades feather, turn sideways. However in my case, with a 22 X 22 three blade, there is enough pitch to rotate the prop, so Jack left me with a solution.I have a Perkins 4.236 engine driving a Borg Warner 71C, then a universal joint to a Wagner Vee drive with 3 - 1 redux.He left me a heavy leather glove and a pair of Vise Grips on a tether. I grab the output shaft coupling - Very Carefully -stop the shaft and attach the Vise Grips to one of the bolts on the coupling. This stops the prop rotation. In our case, when sailing we gain 1/2 knot of boat speed when we feather our prop. This has worked for the 33 years we have had "Satori". It is another example of Jack Jensen's genius. RIP Jack and thanks for our wonderful Cal Boats! Tom Vandiver, BSH Marine, Pensacola, FL. From: "david dobbs tm… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> To: "Ca… [at] yahoogroups.com" <Ca… [at] yahoogroups.com> Sent: Friday, April 17, 2015 9:12 PM Subject: Re: [Cal_Boats] Fixed vs. rotating propeller (was : Gear level when sailing?) So, from all I'm hearing, with my A4 I should just leave it in neutral to free wheel? david dobbs, Cal29 411 with A4 On Friday, April 17, 2015 9:01 PM, "rj… [at] juno.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: Jerry, think about it....... as the boat moves forward it "pulls" the prop through the water.... hydrodynamic forces act on free-wheeling prop to spin it. Since the prop is in essence, like a screw, it will "screw" it's way through the water, revolving the exact same way it would if the engine was turning the prop to move the boat forward, in other words.... the prop will turn in a "forward" direction as the boat sails forward. It would be impossible for the motion of the boat while moving forward to cause the prop to spin in "reverse".Again, if the prop turns in a clockwise direction while the engine is driving the boat forward, then the prop will spin in a clockwise direction as it free-wheels in neutral while the boat moves forward under sail. Drag is created by the slippage of the prop (it will be turning slower under sail than it would at the same speed under power), and friction from the cutlass bearing, stuffing box, transmission, etc. Still, it will rotate in the same direction as if the engine were providing the rotation to drive the boat in that direction.If you were to let your car coast down a hill in neutral, the tires still rotate in the same direction as they would if the engine were moving the car in that direction, the coasting car would be slowed (slightly) by the friction in the drive line (axles to differential to drive shaft to transmission), basically the same as dragging a free-wheeling prop through the water as you sail. A Helicopter in free-fall, ie: engine is not turning the rotor(s), will be slowed by the fact that the free-wheeling rotor will be spinning slower than it would be if it were powered, again due to friction in the rotating assembly. Rod Johnson, "SUNBIRD"1979 O'DAY DS II #10201was: co-owner of "NODROG"1970 CAL 21 #285 On Fri, 17 Apr 2015 23:30:26 +0000 (UTC) "Gerald Sobel so… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> writes: I guess the question is, is the prop rotating in the same direction in neutral as it is when it is being used to propel the boat? Empirically, one could stop the prop by putting it in gear, while sailing, and check the knot-meter, then let it free wheel in neutral, and see if the boat is going faster or slower. If the prop is rotating backwards when the boat is going forwards, it's likely creating hydrodynamic lift in the backwards direction, which is what a helicopter blade would do in free fall. If you don't have a shaft brake, I'm guessing letting it spin will slow you down, which is maybe counter intuitive, but then, sailing upwind is a wild and crazy idea too, but it's how birds get off the ground, and they won't bother arguing with you since they have better things to do. On Friday, April 17, 2015 9:43 AM, "George Barlow ge… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: OK, here’s my take. The apparent wind traversing the plane of the helicopter rotor adds momentum to the rotation of the rotor. The rotor blades produce lift. The controls of the helicopter can be used to increase the lift to “flare” the chopper for landing, in other words to add lift at landing to counteract the sink of the chopper due to gravity. If the prop in the water is locked, the water flowing through the plane of the prop just adds drag and turbulent flow. Drag bad. If the prop is allowed to spin, the force of the water through the plane of the blades imparts rotational force to the shaft. If the shaft is not engaged, it spins freely (subject to friction at stuffing box and bearings. If the friction is too much, it creates heat. So the trade off is do you want the force to spin the prop and create heat or do you want the force to hit the fixed prop and create drag. ___________________ George Barlow Want to place your ad here? Advertise on United Online www.adsonar.com

Right! On Friday, April 17, 2015 7:12 PM, "david dobbs tm… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: So, from all I'm hearing, with my A4 I should just leave it in neutral to free wheel? david dobbs, Cal29 411 with A4 On Friday, April 17, 2015 9:01 PM, "rj… [at] juno.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: Jerry, think about it....... as the boat moves forward it "pulls" the prop through the water.... hydrodynamic forces act on free-wheeling prop to spin it. Since the prop is in essence, like a screw, it will "screw" it's way through the water, revolving the exact same way it would if the engine was turning the prop to move the boat forward, in other words.... the prop will turn in a "forward" direction as the boat sails forward. It would be impossible for the motion of the boat while moving forward to cause the prop to spin in "reverse".Again, if the prop turns in a clockwise direction while the engine is driving the boat forward, then the prop will spin in a clockwise direction as it free-wheels in neutral while the boat moves forward under sail. Drag is created by the slippage of the prop (it will be turning slower under sail than it would at the same speed under power), and friction from the cutlass bearing, stuffing box, transmission, etc. Still, it will rotate in the same direction as if the engine were providing the rotation to drive the boat in that direction.If you were to let your car coast down a hill in neutral, the tires still rotate in the same direction as they would if the engine were moving the car in that direction, the coasting car would be slowed (slightly) by the friction in the drive line (axles to differential to drive shaft to transmission), basically the same as dragging a free-wheeling prop through the water as you sail. A Helicopter in free-fall, ie: engine is not turning the rotor(s), will be slowed by the fact that the free-wheeling rotor will be spinning slower than it would be if it were powered, again due to friction in the rotating assembly. Rod Johnson, "SUNBIRD"1979 O'DAY DS II #10201was: co-owner of "NODROG"1970 CAL 21 #285 On Fri, 17 Apr 2015 23:30:26 +0000 (UTC) "Gerald Sobel so… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> writes: I guess the question is, is the prop rotating in the same direction in neutral as it is when it is being used to propel the boat? Empirically, one could stop the prop by putting it in gear, while sailing, and check the knot-meter, then let it free wheel in neutral, and see if the boat is going faster or slower. If the prop is rotating backwards when the boat is going forwards, it's likely creating hydrodynamic lift in the backwards direction, which is what a helicopter blade would do in free fall. If you don't have a shaft brake, I'm guessing letting it spin will slow you down, which is maybe counter intuitive, but then, sailing upwind is a wild and crazy idea too, but it's how birds get off the ground, and they won't bother arguing with you since they have better things to do. On Friday, April 17, 2015 9:43 AM, "George Barlow ge… [at] yahoo.com [Cal_Boats]" <Ca… [at] yahoogroups.com> wrote: OK, here’s my take. The apparent wind traversing the plane of the helicopter rotor adds momentum to the rotation of the rotor. The rotor blades produce lift. The controls of the helicopter can be used to increase the lift to “flare” the chopper for landing, in other words to add lift at landing to counteract the sink of the chopper due to gravity. If the prop in the water is locked, the water flowing through the plane of the prop just adds drag and turbulent flow. Drag bad. If the prop is allowed to spin, the force of the water through the plane of the blades imparts rotational force to the shaft. If the shaft is not engaged, it spins freely (subject to friction at stuffing box and bearings. If the friction is too much, it creates heat. So the trade off is do you want the force to spin the prop and create heat or do you want the force to hit the fixed prop and create drag. ___________________ George Barlow Want to place your ad here? Advertise on United Online www.adsonar.com

One online test at: https://www.youtube.com/watch?v=jI-UG9RSlJo Prop Drag Test Movie https://www.youtube.com/watch?v=jI-UG9RSlJo https://www.youtube.com/watch?v=jI-UG9RSlJo Prop Drag Test Movie https://www.youtube.com/watch?v=jI-UG9RSlJo This feature is not available right now. Please try again later. View on www.youtube.com https://www.youtube.com/watch?v=jI-UG9RSlJo Preview by Yahoo says that the FREE SPINNING PROP HAS HALF THE DRAG OF THE FIXED PROP! Watch the video. HOWEVER NOTE: Many gearboxes (my Cal 31's Hurth gearbox for instance) says in the gearbox owner's manual that allowing the gearbox to spin when under sail will damage the gearbox. The rear bearing only gets lubed when front shaft is spinning. So with the engine off and the propeller spinning the output shaft bearing is not lubricated. I've been on many other sail boats with the same gearbox warning. Some of those boats had two bladed props and the owners had marked the shaft so he could tell when the blades were vertical and thus aligned with the keel and rudder for supposedly lower drag-- (This vertical prop alignment was probably true for a old style full or 3/4 keel but probably not significant for a fin keel.)

Pretty much everything in this post is mistaken. I'm pretty sure that a free wheeling prop will always rotate in the opposite direction as a powered prop. The analogy of the car tires doesn't apply because tires are not working as a screw; the prop is. And a helicopter in free fall would be slowed even more if the rotor was turning faster--not less.

---In Ca… [at] yahoogroups.com, <oshnek@...> wrote : Pretty much everything in this post is mistaken. I'm pretty sure that a free wheeling prop will always rotate in the opposite direction as a powered prop. The analogy of the car tires doesn't apply because tires are not working as a screw; the prop is. And a helicopter in free fall would be slowed even more if the rotor was turning faster--not less. ummmm no. that's not right. think of it like a fan. turn the fan on and it blows air towards you. walk to the other side of the fan and you will see it drawing (sucking) air from that side. if there was no power to the fan but you were to blow air through the fan, from the back , the fan would turn the same direction as it had under power. think about it. air blowing from the back of the fan, turning the fan prop, is moving in the same direction as air that the fan was pulling to blow out. no difference between the fan and your prop. different fluids, one about 10X as dense as the other, but still fluids; bound by the same laws.

---In Ca… [at] yahoogroups.com, <oshnek@...> wrote : Pretty much everything in this post is mistaken. I'm pretty sure that a free wheeling prop will always rotate in the opposite direction as a powered prop. The analogy of the car tires doesn't apply because tires are not working as a screw; the prop is. And a helicopter in free fall would be slowed even more if the rotor was turning faster--not less. also: when a helicopter is in auto-gyro the rotors (it's not a propeller but a rotating wing) are pitched in such a way that the air moving past the rotors, as the chopper falls, causes the rotor to turn as it normally would. this happens even though the air is moving backwards from the direction it normally flows over the blades. why? well, rotors are angled so that the air pushes against the trailing lower edge of the rotor. in this way, it is acting the same as a propeller; screwing through the air. since the wind flying by the rotors has the turning as they normally would, the leading upper edge of the rotors creates lift, as it normally would. this lift is what slows the chopper as it falls. so, of course it would be slowed more if the rotors were spining faster. in fact, spin them fast enough and it would still be flying. but, really , the helicopter is not a good analogy. a helicopter is a rotory winged aircraft. it is not an aircraft with a big propeller on top of it. a propeller is an air (or water) screw. the rotor of a helicopter is really spinning wings; the spinning is what forces air over the foil to create lift just as a jet or propellerd plane forces air over the foils of the wings by pushing the plane through the air.

sorry. my last two posts might be a little confusing. i put my post under the history and it seems you can't tell where the original post ends and mine begins. oops.

Despite the statement “This feature is not available right now. Please try again later.”, the movie will play if you click on the link. Harleigh From: Ca… [at] yahoogroups.com [mailto:Ca… [at] yahoogroups.com] Sent: Saturday, April 18, 2015 12:00 PM To: Ca… [at] yahoogroups.com Subject: Re: [Cal_Boats] Fixed vs. rotating propeller (was : Gear level when sailing?) One online test at: https://www.youtube.com/watch?v=jI-UG9RSlJo Prop Drag Test Movie <https://www.youtube.com/watch?v=jI-UG9RSlJo> <https://www.youtube.com/watch?v=jI-UG9RSlJo> <https://www.youtube.com/watch?v=jI-UG9RSlJo> Prop Drag Test Movie This feature is not available right now. Please try again later. <https://www.youtube.com/watch?v=jI-UG9RSlJo> View on www.youtube.com Preview by Yahoo says that the FREE SPINNING PROP HAS HALF THE DRAG OF THE FIXED PROP! Watch the video. HOWEVER NOTE: Many gearboxes (my Cal 31's Hurth gearbox for instance) says in the gearbox owner's manual that allowing the gearbox to spin when under sail will damage the gearbox. The rear bearing only gets lubed when front shaft is spinning. So with the engine off and the propeller spinning the output shaft bearing is not lubricated. I've been on many other sail boats with the same gearbox warning. Some of those boats had two bladed props and the owners had marked the shaft so he could tell when the blades were vertical and thus aligned with the keel and rudder for supposedly lower drag-- (This vertical prop alignment was probably true for a old style full or 3/4 keel but probably not significant for a fin keel.)

Yeah, my bad; I guess the free wheeling prop will continue to turn in the same direction because the force acting on the prop is working on the other side of the blades. I got caught up in the helicopter analogy; in that case (where the active side of the rotor blades is always on the bottom), when the rotor becomes free wheeling, it will reverse direction of rotation IF the pitch of the rotor is not reversed. Anyway, I apologize for my reflexive wrong-headedness.