[Public-list] On Replacing the Chainplate bolts

[Don Campbell]

Take the chainplates out and look for crevise corrosion, a major and unsuspected
deterioration of SS in both bolts and chainplates, particularly if there have been any
stress cracks develop in the chainplate due to stress from tension on the shroud. Use a
good magnifying lens to look for stress cracks . If you find any, replace the piece. (This
is galvanic action in an alloy ie different metals within the alloy allow for a galvanic
potential and that is exacerbated by salt water and no oxygen.)
    As for materials, you will need to be specific for your application and use. There are
2 recent articles in DIY boat owner 2002, #2 p 27 by Susan Canfield from Marine Associates
in Annapolis and 2005 #1 p 8 by Patricia Kearns a past assistant technical director of
ABYC and now with Recreational Marine Experts Group in Naples, Florida. I don't know if
you can get these from the electronic version at www.diy-boat.com but it is worth a try.
It would appear as if  fasteners of the grade 304 (18-8)  (18% chromium, 8% zinc.) are
used most frequently but 316 with up to 3% molybdenum is more tolerant of salt water but
not as strong (and  more expensive). Whether you can find fasteners of 316  may be the
question, but that may be the material you require for chainplates if it has the strength.
For an analysis of your present materials, I took some bronze to the scrapyard and had
them do a material test to see what I had in the alloy. They could give me a read-out to
within 0.5% of the components, and they should be able to do the same with a stainless
alloy too.
    The only reference for fasteners with both 304 and 316  I could find was White Water
Marine Hardware Inc.  in Clearwater Fla. 1-800 -572- 8871 and you may need to find someone
locally that they sell to since they are wholesale suppliers.
    The normal taper on the drill bit will centre the bit in the existing hole but use a
drill press if you have access to one for the chain plates.
Don Campbell  #528

FINNUS505 at aol.com wrote:

> Hello my Alberg 30 Friends,
>
> I've been thinking about this job for a while. There is no sign of movement
> at any of Stargazer's chainplates, but just about all of the bolts have lots
> of  red streaks bleeding from them, with no signs of water coming through the
> deck.  I take this as a sign that the SS is aging, and that is the main reason
> I am  thinking of tackling this job. That, and the testimonials of those of
> you who  have done it.
>
>
> Did you drill out the chainplates to the 5/16's hole size with the
> chainplates in place, or take the chainplates off to do the drilling out? I'd  like to
> do it in place, doing one bolt at a time, while the remaining bolts hold  the
> chainplate in place.
>
> Did you just go to a 5/16's bit, or go up to the larger hole in steps, by
> 32nds, or 64ths, or ........ 128ths :)
>
> Are there any special techniques to make sure the new hole is on the same
> center as the old hole, so the position of the chainplate does not move?
>
> Anyone do this job on an old hull (Stargazer is #255), and if so, any  tricks
> you had to do?
>
> I'm going to try to buy the bolts locally. (New Bedford, Mass) I have seen
> the references to using shanked bolts, and will look for them. Is there a
> particular grade of SS that is strongest/ best for this application?
>
> Anything else I should be asking? :)
>
> I'm not looking forward to this one.
>
> Thx,
> Lee
>
> Lee
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