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Buddy Sharpton
05-01-2002, 08:27 AM
I'm bolting my Marshcat back together and I have a question. The chainplates are 1 1/8" x 1/8" bronze,fashioned from bar stock. Four 1/4" holes to be used to throughbolt to the 1/2" coldmolded mahogany hull. On the back (inboard facing) side there has been milled a shallow groove, 3/32" wide, 1/16" deep running straight down the middle, bisecting all the holes, the hole for the clevis pin as well. What is their purpose? If I bed in Dolphinite, they will of course be filled. Is this some sort of water drainage channel?

Thanks for your help.

mmd
05-01-2002, 09:16 AM
Yes, it is for drainage. Due to the constant stressing of the chainplate, water inevitably works its way between the chainplate & hull and in along the bolt threads. The groove allows it to drip out into the bilge. Run a bead of bedding compound down either side of the chainplate and leave the groove area dry.

[ 05-01-2002, 10:17 AM: Message edited by: mmd ]

Buddy Sharpton
05-01-2002, 10:39 AM
Thanks for the explanation. These chainplates mount on the outside of the hull, bronze backing plates inside(which I assume good practice is to be left unbedded) I will be slathering the 1/4" bolts with polysulphide caulk. Will not this caulk, while preventing water from entering hullalong the bolt threads, also prevent water from traveling any further down the channel from the rubrail ddown to the top of the first bolt and leave standing water trapped in that channel. I can't see how water could get into any other portion of the channel which lies lower. Perhaps this channel is only appropriate for an "internal" chainplate and unnecessary for external ones? I have epoxied the bejessus out of the interior of the holes, glaseed and epoxied the topsides and epoxied the interior of the hull. I really want to head off any vulnerability to rot starting in the 11/2" thick hull from water getting into these holes.

mmd
05-01-2002, 12:21 PM
Sorry, Buddy, I thought that the chainplates were internal. I don't know why external ones would be grooved. I'll have to ask a couple of my boatbuilder buddies about this.

Bob Cleek
05-01-2002, 03:12 PM
Easy answer... stock chainplates... one size fits all... inside or outside the planking. No?

reddog
05-01-2002, 05:06 PM
Buddy;
I don't think this would be a water channel on external chain plates.It may be as Bob said,a generic design for internal or external use.My feeling is it is a bedding groove designed to be filled with compound,well slathered,and then fastened to the hull.I'd make sure the through bolt holes were well bedded also.
Earl
One afterthought.Is the channel supposed to be facing out with the other side of the chain plate bedded?