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In the UK there seem to be a few Trapper 500's which have some trouble with the chainplates for the shrouds, i.e. some delamination of the bulkhead, and signs of small upward movement of the plates, evidenced by the bolts no longer being horizontal.
Is there a proven fix? With today's technology getting s/s plate laser cut accuately to any design is remarkably easy and economical.
Frank Marsden
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Greetings Frank
Most of the chainplate problems on Canadian boats stem from water entry down the chainplate from the deck. The entering water gets into the balsa core in the deck opening and into the ply bulkhead, both of which then degrade.
If people's chainplate bolts on Trappers are not horizontal, it suggests two problems, both serious enough to take the boat out of service immediately. First, the chainplate holes are too large, either because they were drilled that way or because they have become worn (a scary thought that suggests prolonged neglect). Second, the bulkhead holes are enlarging, either because the chainplate is moving (v. scary) or because the bulkhead ply is rotting. Both of these problems are fixable, but Job #1 is to stop the water getting past the deck cover plate.
If you are concerned about your boat or just want to do an inspection (good idea), I suggest that you have a look at the thread titled 'Chain Plates' (presently on page 2), and see if the various ideas there answer your questions. If not, get back to us.
Incidentally, the chain plates on my boat are anodized aluminum of about 1/4" thick and are very snug to their bolts. I cannot imagine that laser cutting would deliver a better fit than what was accomplished with a drill twenty years ago.
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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I have seen the same problem with a C&C27 MK1 in our club and the owner was advised to fix it, all he had to do was remove the chain plate and dig out the old and re-bed, he didn't. The next year on a club race night the chain plate let go and his mast fell in the lake, injuring a couple of crew members. It is not a difficult fix at all and if you need new plates then I would say you are on the right track.
All the Best
Bob Wilson
David,
Sending you email with picture of the port chainplate which has small signs of damage, the starboard one is ok, all components are stainless
I think that the bulkhead is in good condition (1978 boat)
I suggest adding a further strip of stainless (316) directly to the bulkhead with no spacer, and replace the backing plate on the other side of the bulkhead with a longer one.
Laser cutting is accurate to about one thou, i.e. better then drilling, but due to the slightly serrated edge not as good as reamed.
The advantace of laser is that I can draw it in Cad, and send it to the cutting company attached to an email, in DXF format, and they cut directly from that.
Frank
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Canadian chainplates are very different. I will send pics after I next visit the boat.
Looking at your photo (now at http://www.cc27association.com/photos/chainpltChant.jpg), I am reminded of several caveats:
1. I am not an engineer or NA. There probably others who can give better advice.
2. "Amateurs always overbuild." - George Cassian, aeronautical engineer and one of the C's in C&C.
3. "Amateurs built the Ark. Professionals built the Titanic." - (First seen in print in a Len Deighton novel, but that may not be the first instance.)
That said, there are two core issues - maintaining the vertical position of the chainplate on the bulkhead and maintaining the separation between the bulkhead and the upper part of the chainplate (because this will affect the effective height of the top of the plate, and because movement of the chainplate toward the bulkhead, which could be caused by deterioration and consequent crushing of the spacer material, would open a gap in the deck through which more water, annoying and destructive, could pour).
Rather than writing some long and tortuous explanation of what I would do, I've doctored the picture to show how I would extend the chain plate to match the Canadian boats' three retaining bolts, plus replace the wood under the bolt area. You could use metal or a dimensionally stable synthetic like Starboard. Whether you have the chain plate made by laser cutting or traditional means is up to you.
The upper portion of the block I would saturate with epoxy to ensure that it is impervious to water and will therefore maintain the spacing from the bulkhead. Alternatively, you could stick with wood throughout, all thoroughly saturated with epoxy then varnished (I think this would be my choice, just for ease of working).
What you do on the other side of the bulkhead depends on the condition of the bulkhead itself. If it's been invaded by water, definitely paint the hole area with unthickened epoxy, let it soak in and set, then fill the holes with thickened epoxy and redrill the hardened epoxy to the correct size for your bolts (the Gougeons have done a lot of tests on this and it seems to strengthen the wood enormously). The bolts could be backed simply by large washers and nylock nuts, as Canadian boats are. I don't think a backing plate is really imperative.
Canadian chainplates are very different. I will send pics after I next visit the boat.
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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David,
Thank you for the suggestion.
Overnight, I decided that the thing to do would be to make a strap about 8" long with two bolt holes, the upper one to fit the lower existing bolt, placed underneath the existing chainplate, replacing the wood in that area. The backing plate on the foreside of the bulkhead would be replaced by a longer three hole one.
The reason to do it this way is to make it easier to get the holes accurate, by avoiding bending the additional strap
This would end up looking very like your modified photo, and hopefully would look like it was done that way originally.
Frank
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