Neil, you mentioned fatigue cracking in aluminum. What about stress corrosion cracking in SS?
Dan, my thought is that the plates are safe for use of the boat. I believe it is more likely that the standing rigging will fail before the chainplates do. I don't know about you but I have plenty of other boat projects that are more worthy of my money. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Wed, Aug 14, 2019, 10:15 AM Neil Gallagher via CnC-List < cnc-list@cnc-list.com> wrote: > Dan, > > Grade 316 stainless is about two to three times as strong as aluminum, > it varies a lot depending on what grade Al you're using. (Some numbers: > utlimate tensile strength of 316 SS is about 84,000 psi, aluminum > 6061-T6, a common marine alloy, is 42,000 psi) SS is also less prone to > cracking under fatigue loading. > > IMHO those chainplates aren't all that bad, the holes are not elongated, > just a little rough. It'd be nice to see the top of the holes where the > load is transferred, but what's visible is decent. There's no > significant wastage in thickness, appears to be mostly the surface > coating that has worn off. If you're really concerned you can have them > dye penetrant tested for cracks, could be done in place. > > Of course free advice is worth what you pay for it.... > > Neil Gallagher > Weatherly, 35-1 > Glen Cove, NY > > > On 8/14/2019 9:42 AM, Dan via CnC-List wrote: > > Fortunately our yard doesn't get involved with stepping and unstepping > > masts so it's 100% my discretion. > > > > I know a guy who does stainless. I was thinking about getting him to > > check out the plates and quote me on new ones made to spec, except > > instead of 1/2" thickness throughout, I would ask for the below deck > > portion to be 1/4" or 3/8" thickness. I'm under the impression that > > stainless is much stronger and can be thinner to achieve the > > equivalent strength to the aluminum plates. I'm not an engineer, but > > I'd sail with that setup. > > > > If these aluminum plates are fine as is for another 5 years or so I > > can put this job off. I've seen much worse corrosion. > > > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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