Thanks Josh, Neil, Yes, I had people help me remove the mast and when the corrosion was evident, both sailors working on the connections told me the plates had plenty of metal and I should just clean them up - which I will definitely do.
I'm still curious about replacement cost so while the plates are removed I'm going to get some estimates. From the numbers Neil just mentioned It sounds like 1/4" stainless would have the equivalent strength, so I'll see what that costs - but I agree with Rob Ball in that the tops could be serviceable or re-inforced but I'll see what the pros say when I take it in for costing - at least I'll know. Chees, Dan I'll report back to the list afterwards. Cheers, Dan On Wed, Aug 14, 2019 at 11:28 AM Josh Muckley via CnC-List < cnc-list@cnc-list.com> wrote: > 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 >> >> _______________________________________________ > > 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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