Do you stop the prop when your sailing.

[Pilotocopilot]

I noticed on a recent thread someone was asking whether to rebuild or replace the tranny that had failed on his boat.

It got me wondering if the failure was not due to how the tranny was configured during sailing. So the question is,primarily for those with Yanmars,what do you do with your transmission when you've turned off the motor and are sailing.

I've sailed with many captains and the primary thing they do is shift the trans into reverse to stop the prop from spinning. But have found this counter to my belief that a prop spinning;1/ provides less resistance and 2/ is less likely to cause damage to the transmission.

 

[tomgrigsby]

Yanmar says leave it in neutral. Use a shaft brake if you don't want the shaft to spin. I used to lock mine in reverse, but after reading the advisory I let er spin and keep a sharp eye out for crab pots.

 

[Maine Sail]

I noticed on a recent thread someone was asking whether to rebuild or replace the tranny that had failed on his boat.

It got me wondering if the failure was not due to how the tranny was configured during sailing. So the question is,primarily for those with Yanmars,what do you do with your transmission when you've turned off the motor and are sailing.

I've sailed with many captains and the primary thing they do is shift the trans into reverse to stop the prop from spinning. But have found this counter to my belief that a prop spinning;1/ provides less resistance and 2/ is less likely to cause damage to the transmission.

For Yanmar / Kanzaki gears Yanmar insists on neutral or the use of a shaft brake. Locking it in reverse is not covered under the warranty...

 

[Pilotocopilot]

Thanks guys I was aware of that info and the reason for posting this was something I found while surfing the web this morning while having my coffee. It was from a Cat site that was actually asking the question of how much drag is induced by a stalled prop over a spinning one when sailing. It was rather interesting because it was conducted by someone that simulated the rig on his CS 36 so really comparable to both the Hunter 36/37. In the process of reading the article there was a link to the Yanmar notice and I've linked both if anyone wants to read them. I can't begin to tell you how many people ive sailed with who are addiment about putting the trans in reverse while sailing.Anyways here's the links.

http://www.catamaransite.com/propeller_drag_test.html

http://www.catamaransite.com/files/YANMAR_MSA08-003_Neutral_Sailing.pdf

 

[Maine Sail]

Thanks guys I was aware of that info and the reason for posting this was something I found while surfing the web this morning while having my coffee. It was from a Cat site that was actually asking the question of how much drag is induced by a stalled prop over a spinning one when sailing. It was rather interesting because it was conducted by someone that simulated the rig on his CS 36 so really comparable to both the Hunter 36/37. In the process of reading the article there was a link to the Yanmar notice and I've linked both if anyone wants to read them. I can't begin to tell you how many people ive sailed with who are addiment about putting the trans in reverse while sailing.Anyways here's the links.

http://www.catamaransite.com/propeller_drag_test.html

http://www.catamaransite.com/files/YANMAR_MSA08-003_Neutral_Sailing.pdf

That is all my work re-printed with my permission.... If you have any questions I am the guy to ask because those are my test results....

 

[Pilotocopilot]

Main Sail great article. Did you ever test for or have read a test of how much resistance a folding or feathering prop adds. I think you had stated the rig was good for 12ish Pounds on it's own, it would be interesting as most feathering props are so expensive to see how much additional drag is induced when it's feathered, especially if it approaches the free wheeling props resistance in your study.

 

[Maine Sail]

Main Sail great article. Did you ever test for or have read a test of how much resistance a folding or feathering prop adds. I think you had stated the rig was good for 12ish Pounds on it's own, it would be interesting as most feathering props are so expensive to see how much additional drag is induced when it's feathered, especially if it approaches the free wheeling props resistance in your study.

My results were such a close mirror of what MIT found that I would suggest reading the MIT prop study. Feathering and folding is less drag than a spinning fixed prop but a spinning fixed prop is a lot less drag than a fixed locked prop..

 

[anchorclanker]

I think the confusion comes from people attempting to compare sailboat propellers to aircraft propellers. There is no transmission on an airplane, the prop and engine share a direct mechanical connection.

It is well known that when an aircraft engine runs out of fuel, or otherwise stops producing power, the forward motion will continue to drive the engine as long as the plane is going fast enough. In fact, pilots are taught that stalling the plane after an engine out, will stall the prop and the engine will turning. Drag is reduced to such an extent that it will increase your available range remarkably to help find a safe landing area.

A boat has a transmission, and in neutral there is no force from the prop to drive anything so the prop simply freewheels. And if you lock it in gear there isnt enough power from the prop to drive the engine, so the stalled prop has MORE drag, not less.

 

[anchorclanker]

Well, It seems some helicopter enthusiasts are confused as well. In an engine out situation, the spinning helicopter rotor is allowed to freewheel, keeping the chopper in virtual freefall while the rotor freewheels to near redline. Then, just enough pitch is pulled in to keep the rotor from overspeeding. Descent rate and high speed rotor rpm are then carefully maintained until very close to the ground, at which point the pilot pulls more pitch into the rotor, turning rotor speed into generating lift. Done correctly, just enough lift is generated to pull off a soft landing before the rotor loses too much speed.

Done improperly (pitch added in too soon), and the helicopter either stalls just above the ground, and then falls because the rotor spun down, or, can actually climb before losing lift, then fall from higher altitute. In both cases the copter is likely destroyed, not to mention the pilot and anyone crazy enough to have ridden along.

 

[Pilotocopilot]

One of the owners I've sailed with had always stopped the prop, the motor had probably close to 4000 hours on a Perkins 135 TC diesel. On the trip south we managed to get as far as Charleston from Boston without issue, and as he and the crew where running out of time to get it down to Ft Lauderdale he decided to leave it in Charleston to get some work done.

The next day after we had left, he's maneuvering the boat into the launch ramp and the trans completely packed in. Twelve thousand dollars later a new one was installed.

I can't say it was the manor in which he used the trans but it may have been a contributing factor, no reverse no forward, nothing. It was,after examination gear failure, from what I don't know but certainly not beyond the realm of possibility that it was caused by engaging reverse when sailing.It's original prop was a fixed three blade since 1986,and only for the last few years had he changed over to a feathering one which doesn't load the trans.

 

[anchorclanker]

While the trans could certainly have been damaged due to gear selection while sailing, it sounds like whoever done the repair raped him pretty good. Talk about taking it up the wazoo without a thankyou.

 

[Pilotocopilot]

Big transmission and he insisted on a new one. The biggest issue was having to remove the generator so someone could crawl behind the motor and remove the trans. The boats a 60 Gulfstar Ketch and the engine room is a packed. You have to be a contortionist just to check the tranny fluid.

The total bill was over 20k including a bottom job new dripless tighten the steering cables redo the Vacuflush seals buff the hull and storage for a month and a half haul out blocking and put in.

The biggest rub was around Jacksonville when the Hood in mast furling packs it in with the main a third out after we picked up the boat and continued down the coast.

After arriving in Lauderdale the guys at Nance Underwood find that a squirrel had nested in the mast using the wire insulation for the furling motor shorting out the system when the boat was out in Charleston.

 

[Blaise]

Any pilot, and yes I am a pilot, will tell you to stop the prop. A spinning prop has the same resistance as a solid disc of the prop's diameter. A stopped prop has only the resistance of the individual blades. That is why pilots of multiengined aircract stop and feather a dead engine.

 

[Maine Sail]

Any pilot, and yes I am a pilot, will tell you to stop the prop. A spinning prop has the same resistance as a solid disc of the prop's diameter. A stopped prop has only the resistance of the individual blades. That is why pilots of multiengined aircract stop and feather a dead engine.

But we're not flying planes.... Multiple studies have now been conducted, including one by MIT, on sailboat props, in water not air, and determined that a locked prop, typical of that used on a sailboat, will create more drag locked.

 

[anchorclanker]

Any pilot, and yes I am a pilot, will tell you to stop the prop. A spinning prop has the same resistance as a solid disc of the prop's diameter. A stopped prop has only the resistance of the individual blades. That is why pilots of multiengined aircract stop and feather a dead engine.

In an aircraft engine out situation, the spinning prop is turning the engine at 1000 rpm or better, and takes a lot of power. Stopping it reduces drag immensely in that situation. Its nowhere near the same as a prop freewheeling behind a boat with the transmission in neutral, or fully feathered into the slipstream of an airplane.

As a pilot you should know, that all thats needed to restart the engine is to unfeather the prop and drop the nose to pick up some airspeed, and the prop will get it turning again.

Anyway, the testing has been done, ya just have to read it.

 

[Stu Jackson]

Time to add "shift lever position" to the anchors & making coffee lists.

If you have a Universal engine, things are different than Yanmars.

http://www.c34.org/wiki/index.php?title=The_Right_Transmission_Gear_for_Sailing

Just sayin'...

 

[Pilotocopilot]

Not necessarily, from the Torreson link on Universal diesels with Hurth Transmissions. "CAUTION: TRANSMISSION MUST BE LEFT IN NEUTRAL WHEN SAILING, DO NOT LEAVE IN FORWARD GEAR WHEN SAILING WITHOUT POWER AS IT WILL DAMAGE GEAR."

 

[Maine Sail]

Not necessarily, from the Torreson link on Universal diesels with Hurth Transmissions. "CAUTION: TRANSMISSION MUST BE LEFT IN NEUTRAL WHEN SAILING, DO NOT LEAVE IN FORWARD GEAR WHEN SAILING WITHOUT POWER AS IT WILL DAMAGE GEAR."

Leaving a Hurth/ZF box in forward will ruin it. However they CAN be left in either reverse or neutral just not the same direction as the direction of travel eg: forward..

 

[splax]

Blaise,
You have made an incorrect statement about resistance in the airstream. Please make sure of your information before making statements for all pilots or that are technically incorrect.

Randall Phelps

 

[anchorclanker]

Splax,

Blaise was correct in regards to aircraft, it just doesnt apply the same way to boats. Pilots are taught to stall the plane after a loss of engine power, so the prop stops turning the engine. The amount of drag the prop creates turning the engine is enormous compared to being stopped, and the reduced drag increases you glide range significantly.

The sailboat prop can freewheel in neutral, so it doesnt have the increased drag of also turning the engine. In that situation, the stopped prop creates more drag.