 |
| The grounding bar with a countersunk hole |
Having determined the appropriate size and location for the grounding bar on
Oystercatcher, my Ericson 25, my next task was to construct the bar and dry-fit it to the hull. This task required me to purchase a copper bard, cut it to length, drill holes through the bar, and countersink these holes. Finally, it required me to drill holes through the boat for the eventual permanent mounting of the bar to the hull.
Earlier, during the analysis phase of this project, I had determined that a bar of 5 feet would be the maximum for this Ericson 25. Therefore, I ordered a bar of this length from Onlinemetals.com. There were various widths and thicknesses that I could have chosen. After weighing my options, I selected a bar that was 1-1/4 inches wide and 1/4 inch thick. I considered a bar that was only 1 inch wide, but I thought that a bar of this width would not be sufficient for the countersinking of the heads of the 3/8 inch bronze bolts. I received the bar in the cardboard tube that you see pictured below.
It was clean, straight, and untarnished when I removed it from the tube.
The most challenging part of this project was determining where exactly I needed to mark the inside of the hull for the drilling of the holes for the bronze bolts. In determining the location for the holes in the hull, I had to take into account the access points to the bilge. I decided that in the access point pictured below (located between the hanging locker and the head), I needed two separate bolts. The red dots mark the spots where I would later drill. I also decided that the red dot in the foreground (which was near the lowest point in the bilge) would mark the central grounding point.
You might recall, from the first posting in this article, that I had originally planned to use the original, 1/2 inch bronze grounding bolt as the central grounding point for all grounding cables. You also might recall that it had been my plan to bend the copper bar in order to route it around obstructions underneath the V-berth.
The obstructions underneath the V-berth, as you'll recall, were the cleats that supported the holding tank shelf and a separate storage shelf. The red line in the picture below marks the planned route around these obstructions.
Now that it was time for me to drill the holes in the hull, I began to rethink my plan for using the original bronze grounding bolt. For one thing, I was concerned that it would be difficult for me to bend the copper bar in a precise way. I had also become concerned about the bend itself. Having reread some of the literature on lightning protection, I had recalled that it is better for conductors to be straight rather than bent. One thing, however, that kept me pondering the possibility of bending the copper was the fact that, if I did not bend the copper, in other words, if I did not make use of the original grounding bolt, then I would need to fill this original grounding bolt hole with fiberglass cloth. Why? Because I definitely did not want to have a solitary bronze bolt just sitting there, within inches of the new central grounding point, i.e., the new bronze bolt at the aft end of the copper bar. Why? Because I didn't want the lightning to be tempted to seek this original, solitary bronze bolt, which happened to sit a couple of inches lower in the bilge. That would negate the purpose of the copper grounding bar; and even worse, it could cause damage to the hull. Therefore, I decided that the most prudent course of action would be to install the copper bar so that it would not be bent, but would instead be straight. Likewise, I decided that, as much as I did not want to do it, I needed to fill that hole where the original bronze grounding bolt had resided.
Having settled on this plan of attack, I moved forward to the V-berth and marked the hull with three red dots. You'll notice in the picture below that the aft-most red dot is in the area that would lie beneath the holding tank shelf. I, of course, could have avoided this area, but I did not want the bronze bolts for this copper grounding bar to be too widely spaced. This was the right place for the bolt, so I really had no choice but to adapt the shelf, so that I might have access to this bolt. I describe this adaptation near the end of the present posting.
In the picture below, we see the red dot that I placed in the mid-locker of the V-berth. Originally, as I said, it was my plan to install a five foot copper bar. If I had followed through with this plan, then I would have installed the forward-most bronze bolt for this bar in this mid-locker. As I explain in the descriptions that follow, I abandoned my plan for making the copper bar five feet in length.
Having settled on the placement of the holes on the hull, it was now time for me to drill the first of the holes in the copper. I should stress at this point that I
did not drill the holes in the hull prior to the drilling of the holes in the copper. I used the red dots on the hull as reference points. On a piece of paper, I jotted down the measurements between each red dot. I then transferred these measurements to the copper bar, where I marked a new set of red dots, which corresponded exactly to the spacing of the red dots on the hull.
Given that copper is a relatively soft metal, it was not very difficult to drill through the bar. The cutting oil, which you see pictured below, was a big help.
After drilling the hole, I used a countersink to chamfer the hole.
This, of course, would allow the head of the bronze bolt to sit flush with the surface of the copper bar.
The fully-drilled and countersunk copper bar with its six holes.
My next step was to return to the boat and drill the first of the holes for the mounting of the bar. In the picture below, you can see just how close the original 1/2 hole for the single bronze grounding bolt was to the new hole that I was about to drill. This new hole would be 3/8 inch, as would the other new holes. Notice that I am keeping the drill as perpendicular as possible to the hull as I begin to drill the hole.
Despite all of my careful planning, it was still a bit nerve-racking to drill a hole through that hull. I was now fully committed to this project.
At this point, I enlisted the aid of the Admiral, who assisted me with the temporary installation of the copper bar. In the picture below, you see that we have installed the first bolt in the first hole. I've not yet drilled any of the other holes in the hull.
The next several steps were especially important. I had drilled the holes in the copper bar first (instead of drilling them in the hull first), because I figured that it would be much easier to use the holes in the copper bar as a guide for the drilling of the holes in the hull, rather than the other way around. Everything was dependent upon proper measurements. You'll notice in the picture below that there is a hole to the left of the copper bar. This is the hole that would soon be filled by the new transducer. I used this hole as a reference point. Within the boat I measured the distance from this hole, in the aft locker of the V-berth, to one of the red dots, which was also in the aft locker of the V-berth. I then transferred this measurement to the exterior of the hull. I place a black dot on the spot, lined up the hole in the copper bar over this spot, and drilled upward into the hull. The Admiral, of course, held the forward end of the bar while I was doing this. Fortunately, the measurements were correct, and the hole was right on the mark.
Once I had this second bolt in place, it was easy to drill the others. All I had to do was to stick the drill bit in the hole in the copper bar and drill upwards into the hull. Notice that in the picture below I have installed all of the bolts except the one at the forward end. Now that I had the bar dry-fitted into place, it appeared to me that it was a little too long. At five feet in length, it stretched upward, toward the waterline.
This next picture gives you a better idea of what I'm talking about. It might have been okay to keep this bar at five feet in length. It's not as if it's at the boot stripe. I did, however, think that four feet in length would be preferable. The lower on the hull the better. Therefore, not long after this, I would cut this bar down to four feet.
Satisfied with the general appearance of the copper bar on the exterior of the hull, I climbed inside the boat to take a few pictures of the hardware on the interior. As you see, I used fender washers under each nut. I figured that this would provide a snugger fit. In case you're interested, all of the silicon bronze hardware that I used in this project came from Top Notch Fasteners out of Mankato, Minnesota. I learned about this company from some postings that I had read on the Cruisers Forum. I've used bronze fasteners for other projects from Jamestown Distributors in Rhode Island. The only problem with Jamestown is that they only sell nuts and washers in large quantities. Top Notch sells them individually. Notice that the aft-most bolt is larger than the other one. I needed this one to be larger, because it would serve as the central grounding point for the grounding cables. I would stack the lugs for these cables on the shaft of this bronze bolt.
The bronze hardware as it appeared in the aft locker of the V-berth.
Now that I had this hardware in place, I could figure out how large of a hole I needed cut into the shelf for the holding tank. I used my homemade hole gauge as a guide.
Back outside the boat, I made the appropriate marks on the shelf.
The hole provided just enough room to access the hardware.
I countersunk
slightly each of the holes on the interior side of the hull, so that the sealant-adhesive that I would later apply in the installation of the hardware would form a gasket of sorts between the hardware and the hull.
With this task complete, my next move was to install permanently the copper bar. That is the subject of my next posting.
This ends this posting on how I constructed and dry-fit the copper grounding bar for
Oystercatcher, my Ericson 25.
No comments:
Post a Comment