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Old 01-08-2012, 07:02   #1
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Join Date: Jul 2012
Location: USVI
Boat: Fountaine Pajot Helia 44
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PapaLulu Project: Approach to DIY Lightening Ground

My wife and I recently came into possession of a 1986 Dockrell 27 which we will be rehab/refurbishing from the keel up. As reference on the Dockrell 27, see [URL=""]. I plan on sharing much of the other projects on this boat in the various other forums under the 'PapaLulu Project' heading since I will need the advice of the many salty folks in Cruisers Forum along the way. As references for this particular project, I have used Ewen Thomson's "Lightening & Sailboats", as well as the ABYC guidance and the "Lightening Strikes" and other forum strings on the Cruisers Forum.

I will be replacing the 1.75" square teak compression post underneath the mast tabernacle which is basically resting with a couple of wood screws on the keel bed (no real support there). There seems to be no bonding to speak of and no lightening protection at all. There are 2 small Dynaplates on the starboard hull about 8" above the iron ballast keel-hull joint and only one of these serves as the ground for the electronics (which I will be completely replacing).

To provide better support to the mast, my plan is to install a stainless steel post with supporting plates at the ceiling (matches the 9" x 12" mast tabernacle base) and rest the bottom compression post plate on a new wood/epoxy base bolted to the keel by 2 of the nearby keel bolts (which happen to be dead center under the mast). Since the iron keel is now exposed and rusty, I plan on sandblasting it and encasing it in epoxy.

My current plan for providing lightening protection is to use an appropriate size copper/stainless steel cable (#4) from the mast head (not sure if I will attach it to the vhf or install the lightening rod above it), and have it travel down the mast, provide a robust connection at the mast step to a similar cable which would travel down the center of the stainless steel post. My dilemma at this point is whether to a) exit the hull to a new grounding plate attached to the hull, or b) simply tie it into the keel and bolt a new grounding plate through the newly applied epoxy and directly into the iron ballast. The idea here is to lessen the damage to the epoxy covering the iron ballast and reduce damage to the hull from a lightening strike.

I also plan on bringing the nav/com cables down through the same compression post but brought in via a route that circumvents the tabernacle and its base, entering and exiting the compression post via drilled holes (will be attaching surge protectors there in the futile hope that it might preserve some of the electronics).

I also plan on bonding all of the major metal components and grounding of the electronics but this would seem best to utilize the same lightening groundplate since I would want to avoid any voltage potential buildup that might occur between the Dynaplate electrodes and the lightening ground (especially if attached to the massive iron ballast). I could just tie in the Dynaplate to the new lightening groundplate if I still want to use the Dynaplate as ground for the electronics & bonding system.

Your thoughts much appreciated.

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