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post #1 of 10 Old 08-21-2008 Thread Starter
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New chainplate insallation

We are preparing to put the mast back in and everything is awaiting installation of the new chainplates. The new plates are much thicker and longer than the old ones (and much more expenseive $2500 in water cut stainless). The issue I'm having is what to do with the holes that don't exactly line up with the old ones. My first thought was to fill with epoxy thickened with silica for strenght and then drill new ones. The knees are plywood cores. I won't even get into the trials and tribulations of how awkward all this is going to be, but any sailor can sympathize I'm sure. I'm also thinking of using the old chainplates as backing plates (yes there are that thin) to add a little strength. Does all this sound wise to everyone else? The other issue is the external foreward chainplate that bends around the bow. The hull is 1 1/2'' solid glass and those holes don't line up at all due to the misplaced bend the machine shop put in the new plate. How would you ("you" being someone smarter than myself) go about mitigating that situation. My thanks in advance as always.
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post #2 of 10 Old 08-21-2008
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We are preparing to put the mast back in and everything is awaiting installation of the new chainplates. The new plates are much thicker and longer than the old ones (and much more expenseive $2500 in water cut stainless). ...
The hull is 1 1/2'' solid glass and those holes don't line up at all due to the misplaced bend the machine shop put in the new plate. How would you ("you" being someone smarter than myself) go about mitigating that situation. My thanks in advance as always.
Generally speaking, if I had a machine shop make a $2500 part for me and the messed it up, they would be making a new one at their expense. But of course that is me the engineer talking and the company doesn't get paid until the part is right. If you already passed them the boat bucks your leverage is shot.

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post #3 of 10 Old 08-21-2008 Thread Starter
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Well I wanted to put in bigger bolt as well as more bolts anyway, and we cut a deal with the rigger that he would polish the plates for free. So it all worked out. kinda
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post #4 of 10 Old 08-21-2008
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Originally Posted by Newport41 View Post
We are preparing to put the mast back in and everything is awaiting installation of the new chainplates. The new plates are much thicker and longer than the old ones (and much more expenseive $2500 in water cut stainless). The issue I'm having is what to do with the holes that don't exactly line up with the old ones. My first thought was to fill with epoxy thickened with silica for strenght and then drill new ones. The knees are plywood cores. I won't even get into the trials and tribulations of how awkward all this is going to be, but any sailor can sympathize I'm sure. I'm also thinking of using the old chainplates as backing plates (yes there are that thin) to add a little strength. Does all this sound wise to everyone else?
I would fill the holes with thickened epoxy. I would also highly recommend that you drill any holes through the plywood knees oversized, and properly pot them with thickened epoxy. Backing plates are a very good idea, but I'd use new stainless steel ones, rather than recycling the older chainplates.

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The other issue is the external foreward chainplate that bends around the bow. The hull is 1 1/2'' solid glass and those holes don't line up at all due to the misplaced bend the machine shop put in the new plate. How would you ("you" being someone smarter than myself) go about mitigating that situation. My thanks in advance as always.
If the bend is misplaced... they should re-make the plate or re-bend the existing plate to fit properly.

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post #5 of 10 Old 08-22-2008
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I don't see any problem with using the old chainplates as backing for the new ones; they are going to be in a non-mechanical load (the backing plate won't take much stress and therefore would never be a failure point). The only problem I see with it is that if your new chainplates don't have a precise hole pattern relative to the old ones they won't mate when you install the new ones.

Did the shop have the old chainplates as templates for the new ones? If they did it sounds like you should ask for them to re-make them or visit you in small claims court. Also why was it so expensive for 7 pieces of plate stainless and 1 with a bend? Seems like $315 per plate that does not fit exactly is rather expensive.

What thickness of plate did you go with? I have a '79 N-41 and the only chainplates that are thin are the forward and aft lowers; the rest are ~5/16" thick.

I would not re-bend the forestay; stainless can be bent once but if you work it too much it becomes brittle. In fact it might be necessary to heat treat it after it is bent to the proper shape if it was not hot-formed.
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post #6 of 10 Old 08-22-2008
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I feel your pain, honestly. I just made 12 new plates and had a machine shop mess up drilling the holes (they had the old ones and I told them they may all be different, and they were all individually number stamped). Fortunately they drilled all of them off in the same direction so I could use a milling machine to "move" (egg shape it) the hole over to match the old ones. This allowed the bolts to mate up to the bottom of each hole where the pull will be so there won't be any loss of strength. I think you could fill the holes in the bow as suggested with the epoxy and colloidal silica and then drill new holes, should be OK, but what a pain. It's a big (huge) job but I feel really good every time I look at them and I know they are new and oversized ( we went from 1.5" X 5/16" to 1.75" X 3/8"). Good luck, hope it all turns out well.

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post #7 of 10 Old 08-22-2008
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JRD—

Egg shaping the holes is a bad idea on chain plates. It will cause the chain plates to load unevenly. If you do a bit of research, you'll find that chainplates are often replaced when the holes are no longer round... You might be alright because your plates are oversized...but I prefer to have them done right... not mickey-moused. This is also the reason it is highly recommended that you have the clevis pins for chainplates properly sized to fit the holes in said chainplates.

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Last edited by sailingdog; 08-22-2008 at 07:35 AM.
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post #8 of 10 Old 08-22-2008
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I agree with filling the old chain plate holes with an epoxy/silica mixture. I did this with mine 5 years ago and they never leaked. There is a good step by step article on this at WEST SYSTEM Epoxy under projects "replacing damaged core". I followed this process with no problems. worked great.the machine shop, I would be have them remake the piece correctly.

Good luck
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Hmm... Can't say that I agree with that technique shown at West System. Why should the chainplate be epoxied to the deck? Seems like the plate needs to be able to flex/expand/contract and the epoxy is very hard compared to a caulking like Boat Life. Also if the chainplate needs inspection you can't easily remove it since it is now bonded to the deck.
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post #10 of 10 Old 08-22-2008
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SD- I would have preferred to have them drilled perfectly, believe me (long story). Since the direction of pull on a chainplate is in only one direction (up) and since all the thru bolts have even contact with the bottom of the hole there should not be any loss of strength. The holes for the pins are correct, I would have re-made them if he screwed that up. With going oversized and 6 or 7 bolts thru each I think they will be fine. But I wouldn't recommend anyone use Valley Machine in Puyallup, WA for anything. I had them polished to a mirror finish at a place called Proflections in Kent, WA, and they did an excellent job. JD

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