Eastward:
You say: "I’m not sure the difference in stern tube ,shaft log,cutlass bearing..." Fair enuff. A great number of people - even yotties of long standing - are guilty of "terminological inexactitude, so let's knock the confusion on the
head before we get into the
repair procedures,
Shaft log: No frozen snot
boat has a real shaft log. When "auxiliary engines" were first fitted to
boats and ships, which were in those days of wooden construction, a real "log" (a piece of timber) was fitted on top of the "keelson" (the main longitudinal
member of the
hull which you would prolly call "the keel") The after end of the Shaft Log butted against the stern post, and the fore end was dead-ended somewhere aft of the
engine compartment. This Shaft Log and the stern post were bored fore'n'aft to accommodate the
propeller shaft and it's associated
gear. Frozen snot
boats, being monocoque, have neither Shaft Log in that traditional sense, nor Stern Post. What they often have, though not always, is a metal weldment that bolts onto the bottom and/or the transom of the
hull. This weldment, even though it is not a "log" and doesn't look at all like a piece of timber, is nowadays called a "shaft log"
Stern Tube: It was necessary when using a wooden Shaft Log to protect the bore in it from ingress of water. A metal tube - the Stern Tube - was therefore inserted throughout the length of the Shaft Log and through the stern post imbedded in bedding compound, usually "red lead".
On a modern "shaft log, this "stern tube" is an integral part of the weldment and is clearly visible since there is no actual log to encase it.
Stuffing box: Affixed to the fore end of the stern tube is a primitive bearing called a "stuffing box" because i9n days of yore you needed to "stuff" it with cotton twine impreganted with tallow. The fore end of the stern tube had a "cup" on and that cup had an internal taper. On the outside of the cup was a thread so that another, larger cup could be screwed onto it. This cup had a straight bore and was a "slip fit" on the
propeller shaft. When you screwed this external cup down onto the stern tube it squizzed the "stuffing" (the impreganted twine) down into the conical cup so it constricted around the propeller shaft. You tightened the cup until, when the shaft was turning, water seeped in around the propeller shaft into the
bilge at a rate of a drop every five seconds or so. That is what provided the lubrication and
cooling for the turning shaft. These days we have far more sophisticated stuffing boxes.
Cutless Bearing: The term is “cutLESS bearing”, not cutLASS bearing”. It has nothing whatever to do with the weapon called a “cutlass”. A cutless bearing is a bearing “without cuts”, i.e. a cutLESS bearing. The appellation was orginally a “brand” name, way before the
concept of “brands” even existed. A “plain” bearing at the
outboard end of a propeller shaft would inevitably collect particles of dirt and be scored (“cut”) thereby. The bearing design you know, a fluted sleeve of “rubber” (these days, “neoprene”) permits the flow of water through the flutes to flush out any grit as well as to cool and lubricate the bearing, which therefore is maintained free of “cuts”, i.e. it is a “cutless” bearing.
Now, the little engines we use are quite rattley, vibrating affairs, and the connexion twixt them and the assciated propeller shaft is primitive. Ideally a “flexjoint” should provide that connexion, but for reasons of cost containment (I assume) builders do not provide that. There are several possibilities , but the best IMO is based on the Hardy-Spicer Constant Velocity joint. Two of those on a short intermediate shaft inserted between
transmission output flange and propeller shaft input flange will compensate for any misalignment of
engine with shaft and preclude
transmission of engine vibration to the sterngear and in consequence preclude the kind of stress cracks you appear to suffer from where your stern tube goes through the bottom of you hull.
Insertion of such a joint would IMO be impractical in your case. It would be a major, major and expensive retrofit :-)!.
You can get by with the sort of
repair you've already undertaken. Once you are into it, it's not so bad. The objective is to build up the thickness of the existing
layup, as it came from the factory, to something that will last a suffient number of years before another repair becomes necessary. If I were you, I would determine the thickness of the existing
layup by drilling a 1/8” hole right through it, somewhere within the cracked area, and testing the thickness with the tongue of a vernier caliber. Then, observing all the niceties of doing
work in fibreglass, I would, over an area enclosing the stressed and cracked area, lay up an equivalent thickness on the outside of the hull and an equivalent thickness on the inside of the hull.
I hope your new toe rail on the EH24 turned out well :-)
TP