Ground Plate

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Richard G.
Posts: 64
Joined: Feb 5th, '05, 20:39
Location: "JOHNNY G" CD27 #66 MDR, CA

Ground Plate

Post by Richard G. »

Seem to have developed some leakage from the grounding plate on my CD 27. Does anyone know what the material is that is between the hull and the backing plate, which is wood? The wood is quite wet and it is the first time that I have noticed this.

Thanks,

Richard
Ron M.
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Location: CD30c Harwich,Ma.

Re: Ground Plate

Post by Ron M. »

Hull is fiberglass, roving and mat about 3/8" in that area.
Replaced the wood backing board for my ground plate with 1/2" FRP a few years back. rounded all edges as that material is sharp ! Caulked well with 4200, particularly both sides of thru bolts. Slight countersink to all sides of holes in hull and backing plate.
CD 30c #42
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Richard G.
Posts: 64
Joined: Feb 5th, '05, 20:39
Location: "JOHNNY G" CD27 #66 MDR, CA

Re: Ground Plate

Post by Richard G. »

Ron,

Thanks for your reply. Did you have any black material, almost like roofing paper between the hull and the wood backing plate?

Thanks.

R
Ron M.
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Joined: Feb 5th, '05, 11:32
Location: CD30c Harwich,Ma.

Re: Ground Plate

Post by Ron M. »

can't recall. Proper cleaning and caulking should do the job. Clean everything with solvent. No leaks in 5 yrs.
CD 30c #42
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Richard G.
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Joined: Feb 5th, '05, 20:39
Location: "JOHNNY G" CD27 #66 MDR, CA

Re: Ground Plate

Post by Richard G. »

Thanks again.

R
Maine_Buzzard
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Joined: Dec 22nd, '10, 21:15
Location: Feet Dry, Olympia, WA

Re: Ground Plate

Post by Maine_Buzzard »

I believe that the tar paper is the leftovers of the sealant, after years of water and wood staining.

+1 on a FRP backer. Sitkaflex, Lifecaulk, or 4000 will work to seal it up.

I had considered using bronze bolts backwards, using a nut and washer on the outside of the hull...
Would then have to make a 1/4" spacer plate to clear the nut and put a second nut over the zinc. Changing zincs would be easier, and as it ate away, the bolt would not loosen up on the hull. A quick turn of the outer nuts would bite into the zinc. Close trimming of the bolt at the nut would minimize drag.

And then I decided that if I had the boat in ten years, I should worry about it then.
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Richard G.
Posts: 64
Joined: Feb 5th, '05, 20:39
Location: "JOHNNY G" CD27 #66 MDR, CA

Re: Ground Plate

Post by Richard G. »

Terrific thanks. Bad news is that I just had the boat out of the water and stripped the bottom of 36 years of bottom paint. Would have been nice to have known that it was seeping before relaunching but then…

Next time in about 2 years unless it gets worse.

Thanks again for the feedback.

R
joemerchant
Posts: 181
Joined: Mar 19th, '13, 12:24

Re: Ground Plate

Post by joemerchant »

Back with StarBoard. Easy to work with and holds up very well. Sold at West Marine. We did all the through hulls last year.
Ron M.
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Joined: Feb 5th, '05, 11:32
Location: CD30c Harwich,Ma.

Re: Ground Plate

Post by Ron M. »

If I recall correctly - starboard isn't recommended for backing plates on thru hulls or fittings.....caulk doesn't bond well to it.
In fact I cut 6 backing plates out of the stuff when I replaced all of them a few years ago - but didn't install them.
Went with FRP.
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ch.ocallaghan
Posts: 37
Joined: Jul 4th, '13, 18:36
Location: Cape Dory 25D, 'Circe' Deale MD

Re: Ground Plate

Post by ch.ocallaghan »

When I bought my 25D, the backing board for the ground plate was similarly in bad shape, decayed and leaking.

I scraped everything off, used a grinder to get down to clean fiberglass, sealed the old holes with filled epoxy, and used a piece of GPO-3 fiberglass sheet as a new backing board, epoxied to the hull. I then drilled holes for the new ground plate through the hull and the new fiberglass backer and threaded them to match the new bolts.

I assembled everything together with a drop or two of 4200 in the bolt holes.

I doubt that it will leak again while I own the boat.

See Maine Sails tutorials on fiberglass backers for Thru-Hulls for details.
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tjr818
Posts: 1851
Joined: Oct 13th, '07, 13:42
Location: Previously owned 1980 CD 27 Slainte, Hull #185. NO.1257949

Re: Ground Plate

Post by tjr818 »

Beautiful work. Nicely done, . . . are this Stainless Steel Bolts? I have been under the impression that SS does not conduct electricity very well. :?:
Tim
Nonsuch 26 Ultra,
Previously, Sláinte a CD27
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ch.ocallaghan
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Joined: Jul 4th, '13, 18:36
Location: Cape Dory 25D, 'Circe' Deale MD

Re: Ground Plate

Post by ch.ocallaghan »

Thanks.

The ground plate is a GUEST Dynaplate made of sintered bronze. The bolts are 1-3" gold plated bolt & nut and 1-3" bronze bolt & nut plus assorted copper washers.
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tjr818
Posts: 1851
Joined: Oct 13th, '07, 13:42
Location: Previously owned 1980 CD 27 Slainte, Hull #185. NO.1257949

Re: Ground Plate

Post by tjr818 »

That should do the trick. Once again, very well done, and thanks for the info about the Guest Dynaplate. :)
Tim
Nonsuch 26 Ultra,
Previously, Sláinte a CD27
Northoceanbeach
Posts: 99
Joined: Sep 8th, '14, 00:10

Re: Ground Plate

Post by Northoceanbeach »

I've read my cd28 has a lightning ground plate. That's what you are talking about right? I haven't found mine yet. Where is it?
Ron M.
Posts: 1037
Joined: Feb 5th, '05, 11:32
Location: CD30c Harwich,Ma.

Re: Ground Plate

Post by Ron M. »

if you have one it would be on the exterior keel. On most CD's it is located approx. amidships about 16" above keel bottom and bolts thru the hull
into the bilge area.
Look at your chainplates, bow and stern stay plates, for #8 or 10 wire bonded to a bolt. Sometimes seacocks are bonded similarly.
These wires, (if they exist on your boat) terminate on the bolts of the grounding plate (Dynaplate) in the bilge.
CD 30c #42
S/V "Bluesails"
+ 41.69989
-70.027199
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