Stern tube removal and rebedding

[Surveyor]

I was able to remove my prop (patience method) and shaft recently. When the stuffing box and hose came off I noticed that the stern tube did not appear to be sealed around its fore end inside the boat. If you look at the picture below you will see a gap between the tube and the boat. In the second picture, you will also notice that there is a broken bolt head on the aft end of the tube.

The broken bolt is going to require that I remove the stern tube to provide access to the bolt. My question is concerning what to do when I reinsert the tube to seal it. I would assume, being a noob, that I would only want to seal it around the flat mating surface at the aft end where it contacts the boat. Is this correct? Which sealant would be best? (would you use for this)

Tube


Broken bolt

[Rachel]

Hi Jim,

That looks like the original Alberg 30 stern tube, and the inside looks original too (I recognize that mountain of caulk). From what I know that's Thiokol, which as far as I was able to determine is basically polysulfide.

While there is nothing horribly wrong with that stern tube arrangement, it has enough disadvantages that if mine were already slightly broken, and I were doing a big re-fit on the boat like you are, I would just remove it and replace it with a pre-made fiberglass stern tube, glassed into the boat (there are good examples of how to do that in Northern Yacht Restoration's project logs, and probably mentions here too).

Mine was in better shape than yours so I kept it, although I did remove all that caulk, make some changes underneath, and then put in new caulk (but much less).

If you do decide to keep that one, here are a couple of data points:

1) The OD of the stern tube does not match the ID of any normal hose sizes, nor does it match the stuffing box (unless you have an odd one). This can be fixed, but if you were to put in a new stern tube you would also alleviate that problem.

2) I can't remember if those two studs are just tapped into the fiberglass or if there are nuts on the inside.

3) I think the inner part of the stern tube that you can see is a separate piece from the outer part (threaded together).

I'll see if I can dig up a few photos of mine to post.

Rachel

[Surveyor]

I just finished reading the thread you are thinking of! Lots of good info there!

viewtopic.php?f=4&t=4853&p=40905&hilit= ... ube#p40905

I think you have a point about replacing the tube. If I am going to do it, I might as well do it right.

[Rachel]

Okay, here are a few photos that will probably look familiar to you.

The outside piece:

The inside stern tube area, "before." With Whitby caulk volcano ;)

After the caulk was removed (that was fun)

Another view (that flat "shelf" you see is a solid area that just fills in the very after V section of the keel)

Since that "shelf" was flat and cleaned off at the time, I decided to add some thickened epoxy so that it would not be a place for standing water. I'm sorry but I don't have photos after this; I later re-caulked with polysulfide, as original, but with much less caulk (i.e smaller volcano and more "bare" painted fiberglass).

In a related move I machined down the stuffing box to very closely match the OD of the stern tube and also a standard hose size (I don't know if you can see it in the original photo but because the stuffing box was so much larger in diameter than the stern tube, the stuffing box hose was "gathered" on the stern tube and the clamp had cut into it. There was plenty of "meat" on the stuffing box after it was machined.

While we are on the topic of amusing A-30 construction quirks, and since you are doing a big re-fit, you might consider checking on two more things "down below":

1) The "false bilge," which lies aft of the ballast pig (under the engine, basically) and is comprised of wood and cementitious material. Mine was completely saturated with old gas and caused the boat to smell horrible no matter how much I cleaned (until I got rid of it, and gained a nice sump in the process).

2) The sealing of the ballast pig. The pig is iron, and most of the A-30's I've seen had a pretty pathetic attempt to seal it at the builder. Basically a whisper of cloth and 1/2" of plain resin, which on my boat had probably cracked in 1968. The ballast pig was rather exposed. I sealed mine with epoxy and biaxmat. Luckily mine was a dry, freshwater boat, and so there was no rust on the pig.

Many people are not bothered by #1 and #2 and/or they are not a problem on their particular boat; but if you/yours are, then I'd hate for you to get everything buttoned back up and *then* find out about it.

Rachel

[Surveyor]

Rachel, thank you for the information and I agree. I am going to seriously consider your advice. If I am going to do it, it needs to be before I move any further with the beds. It doesnt look to be very complicated to do.

[Figment]

[devil's advocate]

So, why was it built with the external tube unit in the first place?

[/devil]

[Rachel]

[devil's advocate]

So, why was it built with the external tube unit in the first place?

[/devil]

Wait, is that a trick question? Or...?

(I have some ideas about why it might have been used, but... I might not be "getting" your question.)

[Figment]

No not a trick question.
Not a genuine one either, of course, more a suggestion for pause to consider that the original builders might have brought some thought and experience to bear on the decision back in the day.

[Rachel]

No not a trick question.
Not a genuine one either, of course, more a suggestion for pause to consider that the original builders might have brought some thought and experience to bear on the decision back in the day.

Okay, I hear you on that. I guess I have seen enough evidence that brings to mind "we did it this way because it was cheaper/easier/the way we used to do it on wooden boats/the way we now think we should do it on these new-fangled fiberglass boats/this will be fine for ten years" on A-30's (and other similar boats, not that the A-30 is uniquely sub-standard or anything) that I don't really feel that way about some of the its construction details. (And also to be fair, Whitby were pressured by a large group of buyers to keep the price under $10k, so of course some things had to give).

I actually did keep my original stern tube, and simply modified the stuffing box to match, but it was in excellent condition. If it had been compromised, I would have considered replacing it with a glassed in fiberglass tube. I wouldn't by any means put the stern tube fitting on the "super dangerous get it out of there!" list.

I do agree with you that there is no sense tearing things out and replacing them without at least considering why they were chosen and how they fit into the big picture (d-mned because it's all connected! ;). And I still love to watch the film of Yves Gelinas' southern ocean circumnavigation in his A-30 and see how the boat was largely stock. Granted, it was modified, but I mean I see a lot that is bone stock too. So it's a good boat. Pretty too :)

[Surveyor]

[devil's advocate]

So, why was it built with the external tube unit in the first place?

[/devil]

I have probably over analyzed this topic and tomorrow I hope to remove the parts and maybe discover the answers. From my armchair though, I would guess that the external bronze tube was designed with a fear that anything else (glass) might succumb to the elements and compromise the boat. This might be especially true if the cutlass bearing were to expand for some reason or a glass tube stressing from repeated bearing replacements (beatings). It might even be a stronger, in theory, repellent or protection from the damage of whip. Two lag bolts aligned vertically 3 inches away might not be enough to overcome that, I dont know.

The scary part, to me, is the "twist apart" aspect of the assembly. I have not seen it yet and I think "it' will have much to do with what direction I take.

[Rachel]

My guess would be similar to yours. I'm thinking that on wooden boats the glassed-in-tube option would not have existed, and so maybe this type was more popular then, so they used it? Along the same lines, their rudder evolution:

1) Very early boats: Wooden planks with drift pins. Tried and true.
2) Middle boats (like mine): FrankenRudder that had a brass skeleton with sort of drift pins/tangs, buried brass straps sort of connecting that to the filler, buried wooden strips, and a fiberglass shell. It worked fine but was clearly built with a wood-meets-glass mindset.
3) Later boats: Foam filled fiberglass rudder with the usual shaft/tangs inside.

If the stern tube were (is?) in good shape, I don't see any problem with keeping it. On the other hand, if it's in questionable or needs-a-bunch-of-work condition, I would probably would not make the same choice going back in. For one thing it has an odd, fits-no-hose sized tube (which can be overcome), and too, it is a bedded item underwater, vs. a more integral part like a glassed in tube would be.

Again, no biggie if all is well; but maybe something to consider if it's "broken." (Without unnecessarily turning a five year project into a seven year one ;)

Rachel

PS: Off topic, but who doesn't want to see photos of FrankenRudder? As built, with what you see having been under the factory fairing. The square channel is there because there are brass fingers threaded through holes in the shaft and terminating in the rudder blade where the channel is; the channel is where the nuts were. It was filled in with wood and etc. The brass straps don't attach to the shaft at all but simply rivet through to straps on the other side.

[Surveyor]

I got the stern tube out. It would only come out after I removed a good portion of the Thiokol crap. Man, that stuff is hard to work with. The best way to remove it, for me, was using a dull screw driver on the thin parts and a sharp chisel on the thick stuff. Because it is so hard to get off, I am not going to take it all out but rather just enough to do my repairs. I will shape it up a little bit so it doesnt look bad before I paint over it.

Rachel, you might be able to see that my "shelf" is much higher or closer to the shaft than yours. There is (was) only about an inch between it and the bottom of the log. And it has a fiberglass dam on the fore side about 3/4" high which creates a pool (the black area). It was soaking wet and once the tube was out I could remove the glob of caulk under it with my fingers.


The hole for the stern tube is huge! I forgot to measure but it is easily 1/2" larger than the tube. The aft 2" of the tube was wrapped with some kind of rubber gasket stuff which really wasnt doing much and had actually reacted with the Thiokol.




I dont really like this setup. I know it has worked on hundreds of boats for decades but I think it could be fairly easily improved upon.

[Rachel]

Size of hole+glob of caulk filling gap between that and the stern tube=yikes.

I bet you are glad you took that out, and it's fairly clear that it must have been leaking (mine didn't show any signs of that - maybe the hole was a tighter fit). I think having to fill that in to make it fit would put me right over the edge to a fiberglass tube. Might as well be done with it and nothing to bed/deteriorate/etc.

Interesting to see how the "shelf" in yours differed from mine (do I know what hull number yours is?). But then that shelf was probably just the termination of the filler of the back of the keel and as such, done a bit "freehand" in terms of size and shape. There was no lip on mine - it was completely flat.

When I removed the false bilge in my boat (at the bottom end of that hard/fiberglass filler), the filler did not extend below the top of the false bilge (I filled it in when I exposed the bilge sump just so it would be smooth and easy to clean). So I'm pretty sure its main job was just to hide/cover the "raggedy" bit at the deadwood.

A few more pics, because... why not.

Overview. It looks so innocent until you remember how hard it is to actually reach that area...

I feel your pain on the Thiokol - that was a real bear to remove! Too hard to easily carve; too rubbery to actually absorb the energy of what you were doing (like pounding a nail into a board on a soft surface). If it were now I think the Multimaster plus some-blade-I-did-not-have-then probably would have helped.... in the areas where it could fit. Innocent looking bucket o' Thiokol:

The scale is a bit hard to see, but there is a sort of dark "waterline" at the bottom of the bilge in this photo. The dark area is what was beneath the "false bilge." The bright white is thickened epoxy and cloth put in where it was rough and craggy because the fiberglass/filler that smoothed out the deadwood ended at the top of the false bilge. I could see that as a real dirt trap, and I wanted it to hold paint and be cleanable.

[Nomad]

I know this post is somewhat older, but maybe someone will still reply to this before i start this discussion all over. Im also replacing my cutlass bearing on my A30. I already have removed my engine. Now my question is about alignment. The stern tube is screwed into the cutlass bearing housing, which in turn is bolted to the hull. So due to this setup, even after removing it to replace the old caulk with 5200, there should be now deviation from intended alignment. Am i right or is this just simplistic thinking?