When I had my boat surveyed, the surveyor made an interesting comment which as I think about it, makes sense. I'd like to hear some other points. Basically, he said he would never install a dripless packing gland system in his own boat. The reason being is that if a conventional packing gland blows, and you are out, you can always replace the flax with a piece of T-shirt or rag or something to get you back. If you have the dripless unit and it lets' go, You're screwed. I admit I don't have a lot of knowledge of the subject, but from what I have read, it does make sense. I'm sure there are points for both--Just curious.
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I'd agree...
Yes, those rubber bellows in the dripless systems make me a bit nervous. I haven't heard of any failures but it could be a real mess if one ripped. I went with dripless stuffing material which replaces the rings in the traditional stuffing box. Have had no leaks so far and I still have the same old stuffing box just in case. It's much cheaper and easier too...
Yes, those rubber bellows in the dripless systems make me a bit nervous. I haven't heard of any failures but it could be a real mess if one ripped. I went with dripless stuffing material which replaces the rings in the traditional stuffing box. Have had no leaks so far and I still have the same old stuffing box just in case. It's much cheaper and easier too...
You might re-post this
...as a question in the props and drive trains forum. I'd be curious to see what Kevin says; he is the expert, after all.
...as a question in the props and drive trains forum. I'd be curious to see what Kevin says; he is the expert, after all.
Concur.
With your friend and with Phil and Miles. When I mentioned this on HOW some time back it was blasphemy. But then one fellow noticed how his was leaking because the bellows lost it's tension. If the dripless were not so cheap and safe it might be worth the anxiety I suppose.
With your friend and with Phil and Miles. When I mentioned this on HOW some time back it was blasphemy. But then one fellow noticed how his was leaking because the bellows lost it's tension. If the dripless were not so cheap and safe it might be worth the anxiety I suppose.
pro dripless
Yet again I have a differing opinion. I'm no drive train expert but I've owned a H33 with a Lasdrop (very old, replaced after 15 years this last year) and now have a PSS dripless system. I've had no significant problems but I do agree that if the bellows "goes", I'm screwed! So far I've not had four drops of water in my bilge from the dripless, there is dust under my drive shaft. Since our boat, along with ourselves, are coastal cruisers we realize that we will not be days away from any port. We make occasional 24-48 hour passages, if during that time the system totally failed than we'd deal with it by the usual means (whatever on earth would stop the water is our usual means). I've owned a dripless system for years and all the other owners that I have spoke to all prefer the dripless system (either the Lasdrop or the PSS). As you said, each system has its pro's and con's, we find more pro's in the driplss for our taste.
Yet again I have a differing opinion. I'm no drive train expert but I've owned a H33 with a Lasdrop (very old, replaced after 15 years this last year) and now have a PSS dripless system. I've had no significant problems but I do agree that if the bellows "goes", I'm screwed! So far I've not had four drops of water in my bilge from the dripless, there is dust under my drive shaft. Since our boat, along with ourselves, are coastal cruisers we realize that we will not be days away from any port. We make occasional 24-48 hour passages, if during that time the system totally failed than we'd deal with it by the usual means (whatever on earth would stop the water is our usual means). I've owned a dripless system for years and all the other owners that I have spoke to all prefer the dripless system (either the Lasdrop or the PSS). As you said, each system has its pro's and con's, we find more pro's in the driplss for our taste.
Risk of dripless packings vs. packingless seals
It might also help to formulate the problem better. In my book a dripless packing is a packing for a stuffing box that does not need to be lubricated by the constant slow flow of seawater, e.g. some of the Teflon packings that provide plenty of built-in lubricity. These types of seals would NOT appear to suffer from the presumptive risks mentioned in the original post. The PYI seal, and others of the same ilk, however, try to achieve a reliable, dripless seal without any kind of packing by pressing 2 smooth surfaces together with minimal friction. If this type of seal fails there could indeed be a risk of massive seawater influx. Since I do have one of these myself and have had some problems offshore (due to overheating) I have thought about possible emergency responses. Here is what I plan to do if the bellows would rupture completely (with a partial rupture I would first try to tightly wrap a heavy piece of sailcloth or heavy plastic around the bellows and seal that in place with ss. wire, tape and/or hose clamps): (1) get every hand on board to start pumping with all available pumps except for 2 crew; (2) the better diver/swimmer of the two jumps overboard with a towel or T-shirt and tries to stem the inflow into the stern tube; (3) the other crew grabs a couple of feet of 1/2 " nylon rope (or bigger or smaller depending on space between shaft and stern tube) wraps it several time around the shaft (groping under water, of course) and starts pushing it down the shaft into the stern tube while adding more and more turns until the space between shaft flange and stern tube is completely filled up. Anxious to hear of any better ideas, of course. Flying Dutchman
It might also help to formulate the problem better. In my book a dripless packing is a packing for a stuffing box that does not need to be lubricated by the constant slow flow of seawater, e.g. some of the Teflon packings that provide plenty of built-in lubricity. These types of seals would NOT appear to suffer from the presumptive risks mentioned in the original post. The PYI seal, and others of the same ilk, however, try to achieve a reliable, dripless seal without any kind of packing by pressing 2 smooth surfaces together with minimal friction. If this type of seal fails there could indeed be a risk of massive seawater influx. Since I do have one of these myself and have had some problems offshore (due to overheating) I have thought about possible emergency responses. Here is what I plan to do if the bellows would rupture completely (with a partial rupture I would first try to tightly wrap a heavy piece of sailcloth or heavy plastic around the bellows and seal that in place with ss. wire, tape and/or hose clamps): (1) get every hand on board to start pumping with all available pumps except for 2 crew; (2) the better diver/swimmer of the two jumps overboard with a towel or T-shirt and tries to stem the inflow into the stern tube; (3) the other crew grabs a couple of feet of 1/2 " nylon rope (or bigger or smaller depending on space between shaft and stern tube) wraps it several time around the shaft (groping under water, of course) and starts pushing it down the shaft into the stern tube while adding more and more turns until the space between shaft flange and stern tube is completely filled up. Anxious to hear of any better ideas, of course. Flying Dutchman
Anxiety: suspenders and belts
We all have different anxiety levels to the point that some men wear suspenders and belts . . . If you are using your boat more than just occassionally, and you routinely monitor oil levels, water in the bilge, dripless packing glans, through hulls, etc., I can't see that it is any more dangerous than any of the other holes in the boat <grin>.
We all have different anxiety levels to the point that some men wear suspenders and belts . . . If you are using your boat more than just occassionally, and you routinely monitor oil levels, water in the bilge, dripless packing glans, through hulls, etc., I can't see that it is any more dangerous than any of the other holes in the boat <grin>.
Henk....why not just have Filler Putty on board
for "stuffing" around the shaft enterance and in the stern tube?...I think Practical Sailor just did a reveiw?(I'm not sure)......I bet there are all sorts of "clays"..."Putties" or whatever that would do a fantasic job of plugging it up (Inside and outside) the boat until you got to port..... I also know something else you could do...(from an old sailor that lost his prop shaft once)....If (big if)....you can drop the shaft (yes...bye bye propellor)....you could stuff anything (he used a big ole potato) onto the stern tube from the inside.. But I think this concern is a little unwarranted for massive failure....my old boat had a rubber connector going from the stern tube to the stuffing box....I guess that could go also ...I have heard of one bellows ripping......but that was because somehow (a diver) got air in the bellows and he never "burped" the seal. When he went to sail everything was ok....but it overheated the grahite and when he shut the engine down, it "fused" to the stainless donut.......So the next time he went out..(next weekend?) and started the boat it "ripped" the bellows slightly before the "sealed" graphite/stainless section came lose....but this is extreemly rare and typically would only happen right after leaving the dock......
for "stuffing" around the shaft enterance and in the stern tube?...I think Practical Sailor just did a reveiw?(I'm not sure)......I bet there are all sorts of "clays"..."Putties" or whatever that would do a fantasic job of plugging it up (Inside and outside) the boat until you got to port..... I also know something else you could do...(from an old sailor that lost his prop shaft once)....If (big if)....you can drop the shaft (yes...bye bye propellor)....you could stuff anything (he used a big ole potato) onto the stern tube from the inside.. But I think this concern is a little unwarranted for massive failure....my old boat had a rubber connector going from the stern tube to the stuffing box....I guess that could go also ...I have heard of one bellows ripping......but that was because somehow (a diver) got air in the bellows and he never "burped" the seal. When he went to sail everything was ok....but it overheated the grahite and when he shut the engine down, it "fused" to the stainless donut.......So the next time he went out..(next weekend?) and started the boat it "ripped" the bellows slightly before the "sealed" graphite/stainless section came lose....but this is extreemly rare and typically would only happen right after leaving the dock......
Packing-less seals (responses to Jim and Tom)
To Jim: Each of the areas you mention has different safety precautions. At least I hope you DO have wooden plugs ready for thru-hull problems and you Do have a bilge pump, and so on and so forth. Well, it so happens that, at least for the larger boats, wooden plugs will not fit your stern tube if a propellor shaft is in place (unless you are ready to ditch your propellor and shaft first). Moreover, the rubber bellows of a packing-less seal (which has little in common with a dripless packing)is not made of the same, heavily reinforced rubber that USCG approved engine intake hose is made of. Our bellows became soft enough when it overheated (as a result of sideways pressure from a floorboard) to make the whole assembly vibrate strongly. If we would not have caught that problem on-time I would not have been amazed to see the entire bellows tear loose from the shaft tube, thereby creating a seawater influx that even our double bilge pump set-up would not have been able to cope with. To Tom: You are right when you are talking about applying those materials from the outside. In fact, we always carry 2 quarts of Splash Zone (or similar U/W epoxy putty) and even tested it out once to fix a small damage on the rudder foil. It works as advertised but will not necessarily be removable w/o gel coat damage later. Using it on the inside, however, is a different story. For larger vessels, such as our Legend 43, the shaft tube is almost 2 feet below the surface and leaves nearly 2 square inches of clearance between shaft and tube, thus guaranteeing a massive influx of water. If you have ever tried to quickly replace a depth transducer or log while in the water on one of the larger vessels you were probably impressed with the force of the water coming in and will have little or no illusion that you could simply stop that kind of flow with a handful of putty. Flying Dutchman
To Jim: Each of the areas you mention has different safety precautions. At least I hope you DO have wooden plugs ready for thru-hull problems and you Do have a bilge pump, and so on and so forth. Well, it so happens that, at least for the larger boats, wooden plugs will not fit your stern tube if a propellor shaft is in place (unless you are ready to ditch your propellor and shaft first). Moreover, the rubber bellows of a packing-less seal (which has little in common with a dripless packing)is not made of the same, heavily reinforced rubber that USCG approved engine intake hose is made of. Our bellows became soft enough when it overheated (as a result of sideways pressure from a floorboard) to make the whole assembly vibrate strongly. If we would not have caught that problem on-time I would not have been amazed to see the entire bellows tear loose from the shaft tube, thereby creating a seawater influx that even our double bilge pump set-up would not have been able to cope with. To Tom: You are right when you are talking about applying those materials from the outside. In fact, we always carry 2 quarts of Splash Zone (or similar U/W epoxy putty) and even tested it out once to fix a small damage on the rudder foil. It works as advertised but will not necessarily be removable w/o gel coat damage later. Using it on the inside, however, is a different story. For larger vessels, such as our Legend 43, the shaft tube is almost 2 feet below the surface and leaves nearly 2 square inches of clearance between shaft and tube, thus guaranteeing a massive influx of water. If you have ever tried to quickly replace a depth transducer or log while in the water on one of the larger vessels you were probably impressed with the force of the water coming in and will have little or no illusion that you could simply stop that kind of flow with a handful of putty. Flying Dutchman
Wow
Talk about stirring up a hornet's nest. I never thought it would get this much attention this quick. If a moderator wants to move it, please do so!
Talk about stirring up a hornet's nest. I never thought it would get this much attention this quick. If a moderator wants to move it, please do so!
Henk, you have a 2" log?
You said there is 2 square inches around d the shaft. This would indicate a 2" ID log around a 1.25" shaft. Do you need 3/8" clearance to accommodate the engine mounts? A round hole, 2 square inches of area, 24" below the water line, would yield about 75 GPM. That's 4,500 GPH, in bilge pump terms. WOW!
You said there is 2 square inches around d the shaft. This would indicate a 2" ID log around a 1.25" shaft. Do you need 3/8" clearance to accommodate the engine mounts? A round hole, 2 square inches of area, 24" below the water line, would yield about 75 GPM. That's 4,500 GPH, in bilge pump terms. WOW!
Yes, Peter, I think those numbers are correct;
both with regard to the ID of the shaft tube and the expected influx (with the shaft in place). Alas, I am in Park City, USA right now and unable to verify the log ID, but approx. 2" is my best estimate and the shaft OD is indeed 1.25" Our total bilge pumping capacity (2 electric bilge pumps plus the engine pump (via a Kingston valve) and two Whale footpumps (on a good day) would be about 3,600 gph, if I remember well. So, that still does not leave a whole lot of time to plug a catastrophic PYI PSS bellows leak. Yet, I do like our PYI seal, especially after we replaced it with the active watercooled version. However, it is certainly not a device to neglect for a very long time. Flying Dutchman
both with regard to the ID of the shaft tube and the expected influx (with the shaft in place). Alas, I am in Park City, USA right now and unable to verify the log ID, but approx. 2" is my best estimate and the shaft OD is indeed 1.25" Our total bilge pumping capacity (2 electric bilge pumps plus the engine pump (via a Kingston valve) and two Whale footpumps (on a good day) would be about 3,600 gph, if I remember well. So, that still does not leave a whole lot of time to plug a catastrophic PYI PSS bellows leak. Yet, I do like our PYI seal, especially after we replaced it with the active watercooled version. However, it is certainly not a device to neglect for a very long time. Flying Dutchman
There are Glands and there are Glands
David, I am aware of two types of packless gland. Both rely on a flat face rubbing against a piece of low friction material. One type has the flat face fixed to the log tube and a piece of Ferodo moulded into a bellows which in turn is held on to the prop shaft with two jubilee clips. The bellows look fragile with a thin wall and look easily torn. I had one of these and it slid up the shaft when going hard astern to get out of my berth with the keel just in the mud. The engine pulled back against its flexible mountings and allowed a gap when in forward gear. The water poured in, but the first thing I knew was seeing a pair of sailing shoes come floating along the cabin sole towards me. I nearly sank because I could not locate the leak. Fortunately the hand pump kept pace and I was only 2 miles from harbour. The other type of gland has a much heftier bellows which are attached to the stern log tube. These carry the carbon seal. On the shaft is a large stainless collar, secured with two grub screws plus loctite and this bears against the carbon face on the bellows. I do not see this ever failing and consequently sleep easy with this arrangement. may I suggest you look into what is available before prejudicing the safety of yacht and crew. Merry Christmas.
David, I am aware of two types of packless gland. Both rely on a flat face rubbing against a piece of low friction material. One type has the flat face fixed to the log tube and a piece of Ferodo moulded into a bellows which in turn is held on to the prop shaft with two jubilee clips. The bellows look fragile with a thin wall and look easily torn. I had one of these and it slid up the shaft when going hard astern to get out of my berth with the keel just in the mud. The engine pulled back against its flexible mountings and allowed a gap when in forward gear. The water poured in, but the first thing I knew was seeing a pair of sailing shoes come floating along the cabin sole towards me. I nearly sank because I could not locate the leak. Fortunately the hand pump kept pace and I was only 2 miles from harbour. The other type of gland has a much heftier bellows which are attached to the stern log tube. These carry the carbon seal. On the shaft is a large stainless collar, secured with two grub screws plus loctite and this bears against the carbon face on the bellows. I do not see this ever failing and consequently sleep easy with this arrangement. may I suggest you look into what is available before prejudicing the safety of yacht and crew. Merry Christmas.
Speaking of Emergency Seals..
..years ago I read that marina patrols kept a supply of wax toilet base seals aboard since the wax could be quickly worked to fill even a pretty large leak ..up past an inch. I have only used it once, but it worked well and I keep a couple aboard. Only costs a buck or two. Also, I have a dripless unit and this discussion will make me check it next time I am at the boat. However, I have only heard of one unit that had a bellows leak, but know several boats that lost conventional packing FWIW. I tried dripless packing in another boat (V32), but had to change out the plastic gland for a bronze one to accomodate the material. I still had some leakage, tho. Later switched that one for a PY unit. Rick D.
..years ago I read that marina patrols kept a supply of wax toilet base seals aboard since the wax could be quickly worked to fill even a pretty large leak ..up past an inch. I have only used it once, but it worked well and I keep a couple aboard. Only costs a buck or two. Also, I have a dripless unit and this discussion will make me check it next time I am at the boat. However, I have only heard of one unit that had a bellows leak, but know several boats that lost conventional packing FWIW. I tried dripless packing in another boat (V32), but had to change out the plastic gland for a bronze one to accomodate the material. I still had some leakage, tho. Later switched that one for a PY unit. Rick D.
Seal Failure
I am a retired engineer from the chemical industry and the PYI type of seal is very similar to the mechanical pump seals which has almost totally replaced packing for seals. The problems with the slight leakage of packing is totally unacceptable for hazardous chemicals. In these mechanical seals the very best materials and trained labor is used for installation and maintenance. And the bottom line is they all fail in service after a while. The majority last for years but they are not permanent! I will go with the conventional setup with teflon type packing. Even Teflon needs replacing every once and a while.
I am a retired engineer from the chemical industry and the PYI type of seal is very similar to the mechanical pump seals which has almost totally replaced packing for seals. The problems with the slight leakage of packing is totally unacceptable for hazardous chemicals. In these mechanical seals the very best materials and trained labor is used for installation and maintenance. And the bottom line is they all fail in service after a while. The majority last for years but they are not permanent! I will go with the conventional setup with teflon type packing. Even Teflon needs replacing every once and a while.
Rick...that is the stuff I heard about !! Henk,
I would try the "wax toilet base seals" material. You could even try a "dry run" trying out the stuff (actually it might be wet...lol)... But It would be a good test....go out on the water on a nice day.......let the boat drift......and then go over trying to wedge all this "toilet wax" up in the space between the shaft and the hull....I don't know your boat, but on mine it wouldn't take too much material to fill up that space well. Then when you think you did a decent job then just test it out!...If you have one of these dripless shaft seals all you would have to do is pull back the bellows and see what amount of water comes in.....I'll bet you wont have much........ And the beauty of this drill is that it is completely reversable....just go back over and pull(dig) the stuff out and you are on your way, it won't be permanent............ In a real emergency you would just have to monitor the shaft log to make sure you are keeping the water at bay....in case there is any water that starts up again....just go over and "plug up" more
I would try the "wax toilet base seals" material. You could even try a "dry run" trying out the stuff (actually it might be wet...lol)... But It would be a good test....go out on the water on a nice day.......let the boat drift......and then go over trying to wedge all this "toilet wax" up in the space between the shaft and the hull....I don't know your boat, but on mine it wouldn't take too much material to fill up that space well. Then when you think you did a decent job then just test it out!...If you have one of these dripless shaft seals all you would have to do is pull back the bellows and see what amount of water comes in.....I'll bet you wont have much........ And the beauty of this drill is that it is completely reversable....just go back over and pull(dig) the stuff out and you are on your way, it won't be permanent............ In a real emergency you would just have to monitor the shaft log to make sure you are keeping the water at bay....in case there is any water that starts up again....just go over and "plug up" more
Hey Don,
I'm sure there are different strengths of materials depending on the brand chosen. As I said,I personally don't have much experience on the matter. (personally, I use the traditional and it is working, therefore, I'm not going to fix it). You do bring up an interesting point though and I'm sure the info is appreciated by all who have read this. I'm suprised to see the many different responses to this article and some of the "quick fixes" should the unthinkable happen. Hopefully everyone can walk away with a little something from this forum, as that's what it's all about.
I'm sure there are different strengths of materials depending on the brand chosen. As I said,I personally don't have much experience on the matter. (personally, I use the traditional and it is working, therefore, I'm not going to fix it). You do bring up an interesting point though and I'm sure the info is appreciated by all who have read this. I'm suprised to see the many different responses to this article and some of the "quick fixes" should the unthinkable happen. Hopefully everyone can walk away with a little something from this forum, as that's what it's all about.
Agree with Gene
I also am a chemical engineer, and, like Gene, have watched a LOT of mechanical seals fail. Unlike packing, they don't drip; they gush. They give no warning of impending failure. They fail suddenly and catastrophically, and there is no sealing them readily once they fail. I have listened to a great deal of discussion on the packing-less seals, and I understand their strong appeal. I will never have one on 'Syzygy'. I have watched too many of them work supremely well, and then, eventually and inevitably, fail. They are wonderful, until they fail, and they all do. Eventually, inevitably, unexpectedly, and gushingly. Carl s/v 'Syzygy'
I also am a chemical engineer, and, like Gene, have watched a LOT of mechanical seals fail. Unlike packing, they don't drip; they gush. They give no warning of impending failure. They fail suddenly and catastrophically, and there is no sealing them readily once they fail. I have listened to a great deal of discussion on the packing-less seals, and I understand their strong appeal. I will never have one on 'Syzygy'. I have watched too many of them work supremely well, and then, eventually and inevitably, fail. They are wonderful, until they fail, and they all do. Eventually, inevitably, unexpectedly, and gushingly. Carl s/v 'Syzygy'
Carl, how many have you actually seen fail??
At least the ones that are used on Sailboats...(the ones used in industrial uses are not exactly the same)....Really I think you are being dramatic here...Tell me how many sailboats you have *personal* knowledge of failure........ You are doing a diservice to everyone by your statement.....no they are not infallable....but nothing is. I know there are alot of very good boat manufacturers that put the PSS Shaftseal as standard equipment. Do you have any hard facts on catastrophic failures on sailboats???
At least the ones that are used on Sailboats...(the ones used in industrial uses are not exactly the same)....Really I think you are being dramatic here...Tell me how many sailboats you have *personal* knowledge of failure........ You are doing a diservice to everyone by your statement.....no they are not infallable....but nothing is. I know there are alot of very good boat manufacturers that put the PSS Shaftseal as standard equipment. Do you have any hard facts on catastrophic failures on sailboats???
Now you've got me thinking
Reading all these responses got me thinking about what I'd want to have on hand if we blew out the stuffing box on Symphony...I'm thinking of taking a tapered seacock plug, drilling a hole down the middle with the same diameter as our shaft, and the sawing it in half lengthwise. The idea being that I could then assemble the two halves around the shaft and drive them into the log...has anybody done this? Am I missing something reason why this won't work?
Reading all these responses got me thinking about what I'd want to have on hand if we blew out the stuffing box on Symphony...I'm thinking of taking a tapered seacock plug, drilling a hole down the middle with the same diameter as our shaft, and the sawing it in half lengthwise. The idea being that I could then assemble the two halves around the shaft and drive them into the log...has anybody done this? Am I missing something reason why this won't work?
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