Aluminum chainplates

[Brion Toss]

Hello,
Skene's rates 1/2" thick plates for 7/32" wire, and a 7/16" pin; what size are your wires? I'm guessing much larger, but then Skene's is very conservative on this subject. If there were a vast surplus of strength I might feel good about re-using the existing chainplates, but I really need to know the loads.
If they aren't reusable, and if the dimensions make sense, simply replacing them with aluminum ones is ideal, assuming you isolate the metals better in future.
Fair leads,
Brion Toss

[mrgnstrn]

There are three shrouds attached, all navtec rod rigging:
-10
-6
-10
in that order (upper, intermediate, lower).
So the total, maximum load with all three at near breaking strength is about 26900 lb.
With a total tensile area of about 2 square inches, that is 13450 psi.
What does Skenes say?
Is this even a design condition that makes sense?
What grade and heat treatment/temper is likely to be the one used?

Thanks,
Keith

[Brion Toss]

Hi again,
You can likely count on about 40,000psi strength for aluminum, so if the radii are right, I think you are in good shape. I will get back to you about the alloy to use; do you have a fabricator in mind?
Fair leads,
Brion Toss

[mrgnstrn]

Brion,

Thanks for your reply. As for radii...?where? Do you mean surrounding the holes for the pins for the turnbuckles.
Pictures are posted here:
http://members.cox.net/btsrefit/chainplate.html

I have two leads that I am working on for getting them fixed.

#1 is to go back to the "old" C&C factory guys up in Canada, who said they have the original drawings, etc.
#2 is to go to a local machine shop, and have them mill off the corrosion, and fill it back in with weld-metal.

Yes, better corrosion protection (e.g. lanocote) would go far to help this in the future....except that I have only had the boat for 2 seasons so far....no idea what all the previous owners did.
(funny how all previous owners are scapegoats....)


-Keith