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Author Topic: Standard stuffing box vs. PSS seals vs. "self aligning" gland  (Read 409 times)

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Patches

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Re: Standard stuffing box vs. PSS seals vs. "self aligning" gland
« Reply #15 on: October 26, 2021, 08:40:54 PM »

Interesting, the concern about the PSS bellows.  It seems to me a pretty rugged piece of hose.  What is the the failure mechanism which concerns those about the PSS bellows, but not regular stuffing box hose?  Is it that something will come in contact with the PSS bellows which will cause it to fail, because it isn't as "thick" as regular stuffing box hose?

Not sure I understand.  I do understand the concern about the rotor backing off, relaxing the bellows, and allowing water ingress.  What am I missing?

And WBev:  why would having a keel stepped mast vs. a deck stepped mast cause you to choose one over the other?  That one stumps me too.

Patches
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Noah

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Re: Standard stuffing box vs. PSS seals vs. "self aligning" gland
« Reply #16 on: October 27, 2021, 09:27:17 AM »

Patches—my “fear of bellows failure” is NOT based upon any firsthand knowledge of any failures. It is just my vibe that it seems more exposed, is a lighter material, more complicated a set-up and more vulnerable to failure than the traditional stuffing box system. As far as deck step vs keel step: I think what he was getting at was if your goal for having dripless was a “dry bilge”; if you have a keel step mast you will have water coming into the bilge via the mast so the goal of a dry bilge is more difficult to maintain. Albeit water coming down the mast would be fresh water.
« Last Edit: October 27, 2021, 09:48:02 AM by Noah »
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1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig

WBev

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Re: Standard stuffing box vs. PSS seals vs. "self aligning" gland
« Reply #17 on: October 27, 2021, 05:07:44 PM »

Patches - Noah nailed it.  The Pearson is dry as a bone, so the PSS keeps it that way.  While fresh water from the mast is better than salty (Chesapeake Bay) water, the dampness is not prevented and the "bang for your buck" diminishes.  That is the main reason why I chose not to install the PSS. 

The rubber boot on PSS is light, and is much thinner than the standard tunnel rubber. It is pliable and quite strong.  I knocked into it many times dealing with other issues on the Pearson, including with the pointy end of a wire hanger I had to put in to keep a hose off of it during a week long trip.  The real issue I see is if the PSS bellows tears, by its very nature it will likely allow a lot more water in than a standard stuffing tube will.  It is made to fill with water and does so fairly quickly.  A good rag or something might slow it down some, but it does seem like it would allow swift ingress.  (While waiting to be lifted, I did push the bellows aft, separating the seal, and a lot of water came in. This was intentional, purely my curiosity, and the boat was in the slings.)
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Wobegon II
1992 C-34 MK 1.5
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Magothy River, MD

Trillium

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Re: Standard stuffing box vs. PSS seals vs. "self aligning" gland
« Reply #18 on: November 14, 2021, 10:43:42 AM »

Interesting conversations around the stern gland wear.

One aspect that should be considered is cutlass bearing wear and what the total alignment is through the cutlass bearing, stern tube and gland and coupling. I have just changed my cutlass bearing and noted that the shaft is not concentric in the P bracket, as indicated by the collets on the removal rig.  I studied the old bearing, as I have with numerous journal bearings on large rotating equipment units to determine the shaft alignment, and determined that it appears to have been running in the 11 o'clock position and that there was no rubber left in that area of the old bearing.  The new bearing is also compressed more in the same position indicating a lack of concentricity.  I have checked the coupling alignment in the past and repacked the stuffing box; but now I have the opportunity to split the coupling and after checking the shaft "journal" area for wear, check whether the shaft has changed its position within the cutlass bearing having been released from the engine coupling.

I would have thought that the problems with the stuffing box may arise from either coupling misalignment or a cutlass bearing/bracket problem since the stuffing box should float on the shaft.  If there is damage to your stuffing box gland it may be a symptom of problems elsewhere rather than being part of a root cause, in which case it may pay to look further rather than just change the type of seal.

Nigel
Trillium 2004 Catalina Mk II #1683
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tmac

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Re: Standard stuffing box vs. PSS seals vs. "self aligning" gland
« Reply #19 on: November 14, 2021, 07:25:19 PM »

I'm certainly no expert on this problem, but as I was reading through this discussion the thought occurred that you might check to see whether the strut that holds the cutlass bearing has ever been bent (however slightly).  Could have been from a slight grounding, or maybe by a boatyard accident as it was being placed in a cradle.  Since you've already eliminated the more common issues, you may have to look at the more unusual...
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Tom McCanna
Bayfield, WI , Apostle Islands 1988 std. rig C34, #818 M-25xp, wing keel
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