Originally Posted by neilpride
In other words, lots of groundings.....
That, or that the boats were in harbors where there were excessively high levels of stray current
in the water
. Which you KNOW has caused corrosion
at advanced rates in the bolts.
BTW, if you're seriously thinking on replacing the bolts, & it sounds as if you are. Aside from getting the original specifications & blueprints on the keel attachments, it'd be wise to consult with an engineer
to see what your other options aside from plain stainless steel
For instance; Nitronic-50/Aquamet, Monel or Monel K-500, the "old standbys" (such as various Bronze alloys), & other options, besides: 304/306 or 316 Stainless. Which tend to have longer lifespans when immersed.
Some of the information on these materials can be found on www.matweb.com
such as their strengths. But you also should look into their cost, (relative, respective) longevities, & corrosion
I state all of the above, because if the original keel bolts are made out of a couple of the more common stainless steel alloys, there are a lot better choices to make/replace them with. And such choices needn't be exceedingly expensive either.
Also, as already mentioned, while the proactive maintenance
is to be applauded. Unless you know that there is a problem with the current
bolts, it's pretty early on in their life to be swapping them out. Especially given that doing so can be incredibly expensive (and highly, technically, involved).
Even just replacing them with the exact same replacements
, may require; an engineer
, specialized yard work, custom tooling, special materials, controlled destruction of certain portions of both the keels & hulls, plus later rebuilding of same....
In addition, I don't think that it's been mentioned yet in this thread. But it's fairly common practice, if one is possibly contemplating replacing keelbolts. To pull out one or two for inspection
, first. In order to ascertain as to whether doing such an involved & expensive job is necessary at the present time.
And even just pulling one or two, for inspection
, often is quite expensive.
Also, I believe that there are methods of non-destructive testing, which allow for inspection of the bolts, without their even having to be pulled out (as in, not even one or two). So, such would definitely bear looking into. As would determining what the current bolts are made of, & how they were fitted into their attaching structures.
So basically, as stated by others already, the more information which you can find out from the original designers & builders, so as to prevent unnecessary, expensive "wrenching" on the boats, the better.
Talk to the already mentioned sources, in addition to some of the well qualified engineers & surveyors on here, & found via the standard resource bodies for such. And also, you'd likely be well served by doing some focused reading in Professional Boatbuilder
(magazine). And or, by contacting some of both the writers for/in said periodical, as well as it's editing staff. Who tend to be exceedingly well educated on such subjects, & many others.