Sounds like you have plenty enough fiberglassing experience.
The 1/8" fiberglass tube wall thickness should be fine, these are typically made with epoxy
and fine, numerous layers of cloth. Think windsurfer mast
, not boat hull
. Or you could get a 1/4 wall thickness tube and have it machined down in just the area of the hose. Or a different size (or reducer) hose may be available. I understand your concern, and would probably try to find an adaptor type hose to fit the 1/4" wall tube and failing that, would probably just go with the 1/8". (I'm overkill prone, but pragmatic when push comes to shove...)
As far as I know the fiberglass tube should be compatible with any kind of antifouling.
As for the antifouling properties of stainless, I'm not aware of any, it brings to mind a stainless steel
boarding ladder a friend of mind had hung off his dock
, in open tidal water, that had 9 months of barnacles
and zebra mussels on it. The mussels had killed (suffocated?) the barnacles
, but under them were circles of corrosion
and in some cases holes all the way through the metal (though the metal was rather thin and of unknown grade).
The cause of the corrosion is certainly mysterious. I know a little about electricity, but enough to know that it is difficult to imagine all the scenarios that can induce enough current
to cause corrosion. There doesn't have to be actual metal to metal contact. This isn't to say that this is the problem though.
As for stagnant-water-caused crevice corrosion, all the engine
usage and moving around would seem to preclude it, but not necessarily. I seem to recall
that in times past (and probably still) people would inhibit marine
growth in their kept-in-the- water boats' centerboard
trunks by pouring various liquids in them, where they were retained by differences in specific gravity.
Guess that's not much help though.
But if you do decide to do this yourself, and regardless of tube material, just a few suggestions.
I don't think it likely that the old tube can be taken out with ease, it is meant to be permanent. If you can get it out easily (without cutting into the boat), while I'm sort of a fan of 5200, popping a new stern tube in with a load of it just doesn't seem kosher to me. Maybe properly thickened epoxy
is the better route
If you do have to grind or cut the tube out, I'd start by trying to cut along the length of the tube, a little below the halfway point, along both sides and joining together where the tube meets the hull
, leaving a kind of clamshell that can be (hopefully) popped off with a hammer and chisel, leaving a saddle like affair to bed
the new log in. Tool of choice would be 4.5 inch angle grinder with 1/16" thick abrasive disc or thinnest diamond blade I could get, or maybe what we call a sawzall around here (reciprocating saw) with a medium fine 6-8 inch metal cutting blade.
Use epoxy and the proper fillers to install the tube.
Duct tape is the best shim to hold the tube centered on the shaft. (possibly even the best use for duct tape) Wind
the tape evenly around the shaft until it is the same size as the ID of the log and slide the log over it. Do it at both ends of the log and it is aligned, if you really want to get anal about it, make sure you start and stop the tape wraps at the same place. (Use the same technique with aluminum
tape (properly wound in the right direction) on drill bits to make drill jig bushings to center drill bolts broken off below the surface.)
Good luck with it and best regards,