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Backstay chainplate block replacement

 
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K.S. Bailey



Joined: 20 Oct 2005
Posts: 23

PostPosted: Mon Sep 24, 2007 9:17 pm    Post subject: Backstay chainplate block replacement Reply with quote

Has anyone moved the T37 backstay chainplate off center during chainplate mounting block replacement? I'd like to bolt the chainplate and mounting block to the hull for an extremely strong bond rather than glass in a piece of wood that may rot out in the future. Moving off center may permit through hull bolting. I removed the original backstay mounting plywood block that was glassed in same as other chainplate mounting blocks, although the glass seemed to be a bit thicker (apx 3/8 inch in places). Quite a challange grinding this out due to cramped working area. Split backstay maybe???? Looking for easy to install ideas that work

I've already sucessfully replaced four of the other water soaked delaminated plywood chainplate mounting blocks with solid (3-1/2 x 3-1/2 inch) "Ipe" ironwood bolted to the hull with 1/2 inch bolts and 5200 adhesive bedding. Did not glass over the wood, as everyone tells me this would be overkill and entrap water. Replaced chainplates with 304 stainless (same as oringal). 316 stainless is almost impossible to procure. Metal suppliers tell me that China is buying up all the 316 to build nuclear plants. Not pretty from outside, but very solid and easy to inspect. When complete, I'll make photos available.

Please send me ideas/comments on backstay mounting as I want to install this coming weekend.

Thanks,
Bucky Bailey
Sea Scouts, Dana Point, CA
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K.S. "Bucky" Bailey
Sea Scout Ship 936
Dana Point, CA
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Kamaloha



Joined: 28 Oct 2005
Posts: 225
Location: Lebanon, NH

PostPosted: Wed Sep 26, 2007 7:36 pm    Post subject: Reply with quote

I through-bolted my aft chainplate whilst leaving it centered. No need to move it off center in order to through-bolt it. Just add a sister plate on the outside of the hull to back the bolt heads.
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Charlie
s/v Kamaloha
1987 T37 #542
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K.S. Bailey



Joined: 20 Oct 2005
Posts: 23

PostPosted: Wed Sep 26, 2007 9:57 pm    Post subject: Reply with quote

Kamaloha,

Excellent idea. We are now thinking of mounting backstay chainplate on outside, maybe beefing up the glass and adding a backing plate inside if needed.

When you drilled through the stern, was the glass pretty robust where the hulls join. I'm concerned about internal voids and weak spots.

Bucky Bailey,
Dana Point, CA
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K.S. "Bucky" Bailey
Sea Scout Ship 936
Dana Point, CA
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Kamaloha



Joined: 28 Oct 2005
Posts: 225
Location: Lebanon, NH

PostPosted: Thu Sep 27, 2007 1:55 am    Post subject: Reply with quote

The T37 hull is not built in halves (port-starboard) as far as I know; the hull is mated to the deck instead. The glass is about a half-inch thick or so at the stern, plenty to support the bolts with a backing block. I've also put a 3-1/2" hole through there for my windvane and I think I might have kept that plug somewhere. It was impressive.

I did not put the chainplate on the outside; that would have required a much larger chainplate and modifying the caprail. I put a sister plate (backing plate) of much thinner material back there to support the heads of the through bolts.
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Charlie
s/v Kamaloha
1987 T37 #542
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NelleBly



Joined: 16 Nov 2005
Posts: 34
Location: Port Ludlow Wa

PostPosted: Thu Sep 27, 2007 5:28 pm    Post subject: Reply with quote

I replaced my backstay chainplate and mounted it on the outside. It did not require any caprail mods, just a backing block of UHMW seated in West System with 404 to assure a flat mounting surface for the backing block. There are pics on the FTP site as well as on my personal web site www.familyyachtclub.com under BJ and photos of "this and that"

I hope this helps.

Cheers

BJ Benson
T-37 NelleBly
#518
Port Ludlow Wa
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K.S. Bailey



Joined: 20 Oct 2005
Posts: 23

PostPosted: Sat Oct 20, 2007 9:06 pm    Post subject: Reply with quote

Thanks for all the chainplate replacement info. Like Kamaloha, I mounted my backstay chainplate external centered on stern with wood block inside (I used Ipe ironwood). Shapped block to fit inside stern, and glued iin with West Systems epoxy. Covered with 1/4 inch of glass (many many many layers of 12 OZ and 2 layers of heavy duty roving also iwth west Systems epoxy. New 304 stainless steel chainplate externally bolted to vessel using 1/2 inch 316 stainless bolts. Glassing in stern backing block may be overkill, but I wanted to make it very strong.

Monting blocks on port and starboard chainplate installed same method, using 1/2 inch 316 stainless carriage bolts through hull. Bolts can now be removed to check for corrosion in future. At first I had only bolted the blocks (no glass), but based on info for this forum, I glassed them in place like original.

T37 newbe so I have other systems to go through. Never ending!
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K.S. "Bucky" Bailey
Sea Scout Ship 936
Dana Point, CA
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Kamaloha



Joined: 28 Oct 2005
Posts: 225
Location: Lebanon, NH

PostPosted: Sun Oct 21, 2007 9:11 am    Post subject: Reply with quote

Nelly Bly, yours is not quite like mine (Kamaloha) - mine is mounted internally, where the original was. The bolts, however, go through to the outside, and a sister (backing) plate is there to hold the heads of the carriage bolts. I used no extra glass, but I did fill the void between the hull and the existing wood block with epoxy so it could handle the compression of the bolts. The nuts are still on the inside, the carriage bolt heads are on the outside. This is the same arrangement I did with the shrouds. I didn't want to move the chainplates to the outside of the hull, as that would have involved modifying the cap rail and lengthening both the shrouds and the spreaders, and it would have meant I could not bring the jib in as far, thus not allowing me to point as high.
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Charlie
s/v Kamaloha
1987 T37 #542
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NelleBly



Joined: 16 Nov 2005
Posts: 34
Location: Port Ludlow Wa

PostPosted: Sat Oct 27, 2007 10:24 am    Post subject: Reply with quote

Charlie

I agree that moving the shroud chainplates outboard would reduce sheeting angle, a compromise that I do not think I would be willing to make. So far I have had no trouble with the shroud chainplates. I rebed them about every other year, and have taken core samples from the mounting blocks looking for water intrusion. So far so good. The backstay chainplate did not get enough attention as one would have to send a small child in to access the nuts to remove and inspect it therefore is was never tended to until I purchased the boat and began obsessing over all her issues. I removed the aft starboard locker in order to gain reasonable access. When taking a core sample I was nearly drowned with all the stinky water rushing out of the encapsulated mounting block. I prefer to not encapsulate wood as it seems wood really likes to breath. In the application of the chainplate mount I believe the compression of the mounting block to the hull spreads the load evenly over a broad surface eliminating the possibility of a stagnant moist environment for a wood mounting block. UHMW takes it a step further.
That said most of our fixes that I have read to the chainplate issues that we face are plenty strong and will last many years. Just being aware and monitoring the various systems on our boats is key to eliminating structural and system failures.

Cheers

BJ Benson
T-37 #518
NelleBly
Port Ludlow Wa
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Kamaloha



Joined: 28 Oct 2005
Posts: 225
Location: Lebanon, NH

PostPosted: Sat Oct 27, 2007 12:19 pm    Post subject: Reply with quote

I know what you mean - I'm not a "small child" but I am only 135 lbs. I go back to the stern all the time, it seems, due to the servicing of the SSB tuner, the Cape Horn windvane quadrant, and the chainplate. I added a little shelf between the hull and the bottom of the port propane locker which I slide along on my right side, having pre-dangled tools on strings down the rudder post access hatch. It seems to work, although I scared myself once when I got a "hot pot" of epoxy while stuck in there and it started smoking in my face. (My aft bilge bottom is now lined with epoxy after it melted through the tupperware.) I've never been able to bring myself to cut out the starboard lazarette like you did, although it makes a lot of sense to do so.
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Charlie
s/v Kamaloha
1987 T37 #542
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