When we were in the demolition phase on this monster of a project, I found these strange things attached to the bottom of the boat. They looked like plastic picnic plates and had DO NOT PAINT embossed in them. I had no idea what they were, but about six inches away from the aft-most one was one of the deepest pits on the hull exterior. Fortunately, the welder who made the aft enclosure was able to fill the pit after the boat was sandblasted. But the bottom paint also had a peculiar look to it around this picnic plate. On the inside of the hull, there were threaded shafts attached to these two plates, with a single wire coming off each one.
I had no idea what these things were, but I was very suspicious, what with the hull pitting and odd, sort of blistered look to the bottom paint around one of them. So I cut the wires inside, unthreaded the bolts securing the shafts, and threw the picnic plates in the trash.
Man…was I stupid.
I learned later that in the mid-1960s, Chris Craft made Engelhard Impressed Current Cathodic Protection Systems (Cathodic Protection Automatically Controlled, or CAPAC for short) standard issue on all of the Roamer metal boat models. Those two picnic plates with the wires going to them are the reference cell, which detects whether your boat is shedding metal or protected, and the platinum anode that sends the “impressed current” out into the water, where it counteracts the metal-eating nature of various electrical forces in water in a process called “polarization.”
A fellow Roamer 46 owner managed to secure an original owner’s manual for the same model of CAPAC as mine: Engelhard Model 10A12D (pdf), although that manual was printed in 1962, seven years before my Roamer was built. This was a great find, since Engelhard hasn’t been in business for decades and I was unable to find any documentation online for this particular model. The company that appears to have bought the CAPAC intellectual property, Evoqua, offers no support for obsolete systems. But I was able to find a company that retails Evoqua reference cells and anodes that appear identical to the ones I threw in the trash: Wards Marine Electric.
The lads at Wards also had no information about Model 10A12D, but the manual they sent me for Model 90W12D (which is Evoqua IP; I am only linking to a copy of it for educational, fair-use purposes) tracks very closely with the information in the 1962 version of the 10A12D manual.
While researching CAPAC systems earlier this year, after realizing my terrible mistake, I also found an obscure article on CAPAC systems that will definitely be of interest to other ignorant metal boat owners, like I used to be, who knew nothing about these things: Cathodic Protection for Boats in Saltwater (Oregon State University, 1979).
Anyway, so with the main propulsion engine thru-hulls welded in, seacocks installed, the bottom paint mostly done, and the CAPAC control panel cleaned up very nicely, I figured I should recommission the rest of the CAPAC corrosion protection system.
$1750 worth of picnic plates and assorted condiments
The tip jar to the right is open for business! lol
Having closed up the last of the holes below the waterline…I went and opened two more
I first drilled a pilot hole for the platinum anode 16″ from the keel under the aft stateroom floor, 10′ forward of the transom (1/4 of the wetted hull length) in the vicinity of the hydraulic steering and fuel lines. I subsequently opened that hole up to 9/16″. The threaded shaft on the reference cell and anode are 1/2″, but I wanted space for some Bar Rust 235 barrier coat inside the hole.
Next, I applied the “capastic shield” outside.
The “capastic shield” diagram Wards Marine gave me wasn’t intuitive
After consulting with the engineering department, Wards informed me that 13R in the diagram above means the “capastic shield” must be applied in a minimum 22 mil thickness around the anode (not the reference cell) in a 13″ radius circle.
Three coats of Bar Rust 235 barrier coat is more than 22 mil, but what the heck…
I suspect that the pit and goofy looking bottom paint I found near the original ‘picnic plate’ was caused by the film thickness being inadequate. These platinum anodes really can blast out the current, so a thick layer of dielectric material protecting the metal substrate of the hull is absolutely essential.
Showtime!
Scoop the contents out of the cans and mix thoroughly
Then trowel it on the hull…all of it
The ‘capastic shield’ is 1/8″-3/16″ thick. And that’s on top of the Bar Rust barrier coat. I subsequently applied three coats of Bar Rust over the capastic shield, followed by two coats of Pettit Vivid bottom paint.
Reference cell on the left, platinum anode on the right
I had to laugh at the installation kit and instructions. The 1962 owner’s manual notes in a foreword addendum that “Neoprene Putty has been replaced with Butyl Bead…” Clearly, that was hi-tech stuff at the time and a major upgrade over neoprene putty. But with all of the advances in caulking technology over the last half-century, the installation kit in 2022 still comes with butyl tape!
I suspect the reason for that is that butyl tape is an effective sealant AND it doesn’t grab on quite as well as modern sealants. If anybody ever needs to remove these ‘picnic plates’ in the future, as I did in 2008, with butyl they won’t damage the plastic when prying them off the hull like might happen with more modern caulk.
Three turns of butyl tape around the perimeter of the ‘picnic plate’
They shorted me on butyl tape!!!
In addition to the three turns around the perimeter, I was supposed to put three turns of butyl around the shaft. But the installation kit didn’t include enough tape to finish the job, so I cheated and used a bit of Pettit Anchor caulk.
I pushed the new ‘picnic plates’ up against the hull on the outside, then ran inside and installed the washers and retaining nuts.
The anode is installed near where the port prop shaft exits the hull
CAPAC Reference Cell is installed amidships, just aft and inboard of the main engine and genset raw water inlets
I installed the reference cell 10′ forward of the platinum anode (again, 1/4 the wetted hull length separating the two, per the directions)
The black wire marks this as the anode; reference cell uses a white wire
The connectors that came with the kit are very robust
I believe these connectors are commonly used in domestic well and other wet-condition environments. There’s a tinned copper butt terminal that you crimp to the wires and a rubber grommet on each end that squeezes the wire when you tighten the end caps. They should have no trouble keeping the connection dry in my bilge.
Looks good
Next, I ran the anode wire up to the salon electrical panel and repeated the process for the reference cell
Wires ready for trimming
Wires trimmed to length and temporarily attached to the CAPAC controller in the salon
I didn’t have the manual with me and managed to connect the anode and reference cell to the wrong terminals. I’ll fix that when I run the 12v supply and hull ground wires in preparation for splashing Spring of 2023.
Next up in our 1969 Chris Craft Roamer 46 Refit: Helm Side Doors
1969chriscraftroamer46 