Through Hull Replacement, Part 8: Drilling the Bolt Holes

The new counter-sunk bolt holes for the new bronze through-hulls
Regardless of whether you have opted to use your new through-hull in conjunction with a seacock or an independent flange (that is then joined to an in-line valve), you will likely want to through-bolt that seacock or flange, so that it is firmly secured to the hull. Before you can through-bolt this hardware, you must, of course, drill holes of an appropriate size and distance through the hull. It would seem that, with all of the hardware on hand and with all of it dry-fitted in place, this would be a relatively simple task. In my experience, however, this was not the case. There were a number of issues that I faced, and there were a number of tools that I employed, in order to move this sub-project from start to finish. For the sake of remembering how exactly I approached this task (or I should say tasks) I have devoted this portion of this multi-part article to the steps I took to drill the bolt holes for the new through-hull hardware on Oystercatcher, my Ericson 25.
I began by focusing my attention on the waste outlet hardware for the marine head. In order to determine the way in which I should orient the handle of the in-line valve, I had earlier cut and dry-fitted all of the new Trident brand sanitation hoses for the head (see Part 2 of this article for more details). Now that it was time to drill the holes through the hull, I thought it wise to do one final dry fit. Getting this just right was important for two reasons. First, the arm of the valve had to be oriented it a way that would allow it to swing free of any obstructions. Secondly, the flange had to be mounted to the backing plate in a way that would allow the valve to be oriented in the correct position when the two pieces of hardware were joined to each other. This sounds more complicated than it really is. All you have to do is screw the two pieces of hardware together and then make the marks that I describe below.
Having screwed the two pieces of hardware fully together (the flange and the in-line valve), and having determined the correct orientation of the in-line valve with regard to the swing of the handle, I marked the backing plate with a pencil. I have here taken the time to emphasize the importance of getting all of this right, in order that someone might not make the mistake of mounting the flange without taking into account the orientation of the in-line valve after it is fully screwed onto the flange.

I must also note that before I marked the backing plate, I also had a friend of mine screw the through-hull into place from the exterior of the boat. This was important, for it allowed the hardware to be aligned in precisely the manner that it would be aligned when the time came for the final installation. It also allowed me to determine exactly where I should drill the holes.
It was after we had removed all of the hardware and I had inspected my pencil marks that I discovered how difficult it would be for me to drill the holes for this particular flange. It was not the flange itself that presented any problems, but the proximity of the wooden bulkhead to the work area. The only hole that I would be able to drill with my normal-sized Makita power drill was the forward one, i.e., the one to the left in the picture below.
Even though this mark was approachable with my power drill, it was still not easy to determine whether or not I was squared-up over the hole. In other words, the drill would fit in this space, but I myself didn't fit very well. After much thought and much discussion, I finally decided to go for it. I began by drilling a pilot hole.
My buddy then screwed in the through-hull while I held the flange in place on the interior of the boat. Fortunately, the pilot hole appeared to be oriented correctly.
We checked to see if the head of the bolt would clear the head of the through-hull when the time came for me to counter-sink the bolt. It looked like it would.
Convinced that all was well, I returned to the interior of the boat and drilled the real hole with the 5/16 inch bit.
We then did a test fit to make sure that the through-hull, the flange, and the bolt were all lined up the way they were supposed to be. They were.
Now, I needed to drill the other two holes. For this, I turned to my Milwaukee brand right-angle drive attachment. I had purchased this at an earlier date for a different project on this boat. I must say that this is one of the most useful tools I have ever owned.
It cost me over $50 online, but it was well worth it. I had earlier purchased a cheap, flexible extension from a home improvement store. It broke after I had drilled only about three or four holes.
When I used this Milwaukee attachment with one of my cordless drills, I could drill all sorts of holes in hard-to-reach spaces in this boat.
At the same time I had purchased the Milwaukee attachment, I also had purchased this Milescraft brand StubbyBit set. This was also a smart purchase. It made the above described set-up even more useful in the many tight-spaces in this boat.
Using the cordless drill, the Milwaukee attachment, and the 5/16 inch stubby bit, I successfully drilled the second hole for the flange. Afterwards, my buddy and I did a dry fit. Everything looked good.
Removing the in-line valve, I turned my attention to the final hole. This one presented some problems. I did not take any pictures of these steps, but I should say that for the drilling of the second and third holes I was not able to drill all the way through the backing plate and the hull with the stubby bit, while the flange was in place. Ideally, as Maine Sail suggests in his article on through-hull installation (see the Compass Marine link on the homepage of this site), you want to drill these holes while the through-hull and flange are in place. This will ensure that all three holes are perfectly aligned with the holes in the flange. For these two holes, I just couldn't do that. Instead, I would drill the hole as deeply as possible with the flange still in place. Then, I would remove the flange and complete the drilling. Even with the flange removed the stubby bit was almost not long enough to make it all the way through the hull.
I must have gotten lucky with the first hole that I drilled with the stubby bit, because it exited the hull in just the right spot. I was not so fortunate when it came to the next one. When it exited the hull, it was dangerously close to the chamfered hole for the head of the through-hull. This poor alignment caused other problems as well. In the picture below you see that the bottom bolt is projecting through the flange but that the top bolt is missing. Recall that I had already drilled the top hole with the stubby bit. I was dismayed to discover that when the bottom bolt was inserted the top hole was not visible. The same held true when I inserted the top bolt. This caused the bottom hole to be covered by the flange. Notice the pencil mark near the bottom of the flange. You can see that the flange is off the mark by about 1/16 to 1/8 of an inch. I would remedy this problem by drilling the bottom hole slightly larger.
Here's what it looked like outside after I had drilled all three holes.
I didn't want to purchase a step wrench (a tool made specifically for through-hulls) for this project, so I instead used a piece of oak, as suggested by Don Casey, This Old Boat, 2nd Edition, to screw and unscrew the through-hull during the many dry-fits. I should point out that this oak worked well in the short run, but it was not good for screwing these through-hulls in tightly. For that, I used something different, as you will see.
In the picture below you get a good sense of just how close that bottom bolt is to the head of the through-hull, and this is after I have adjusted the hole by re-drilling it and enlarging it. There's really very little room for error when drilling these holes. Even when perfectly aligned, the heads of the bolts come close to touching the head of the through-hull.
My next task was to counter-sink the heads of the bolts. I did not take any pictures of this, but I did take some when I worked on the other through-hulls.
Now it was time to focus on the hardware for the 3/4 inch through-hull that would provide raw water for the head. You see it below, on the left.
Again I wanted ensure that the in-line valve was oriented correctly. I also wanted to ensure that the right-angle tail-piece would be pointed in the right direction after everything was screwed together.
I decided it wouldn't be a bad idea to bring in the new head for this dry fit. This was a Raritan PHII. I had purchased this to replace the original Raritan PHI. The new one had the same dimensions as the old one.
Everything looked good.
Just as before, I marked the backing plate with a pencil while the hardware was in place.
I drilled the first hole, and heard from my buddy on the outside that it was well positioned with regard to the large chamfered hole for the through-hull.
To make sure, we reassembled all of the hardware.
Satisfied, I removed the in-line valve and proceeded to drill the next two holes, using the holes in the flange itself as the guides.
This whole job went much more smoothly for me. It helped somewhat that I already had the experience of installing the larger flange, but it was especially helpful that I could drill these holes in an unrestricted fashion with the regular power drill.
It all came together well when we tightened everything down.
I was pleased to see that the edges of the flange overlapped the mahogany ring that served as the foundation for the backing plate.
Afterwards, I climbed outside the boat to see how it all looked.
The bolts were evenly spaced around the chamfered hole. You should notice that, with the 3/4 inch through-hull, the heads of the bolts do not encroach on the chamfered hole as much as they do with the larger, 1.25 inch through-hull. In other words, the margin for error is not as small. The reason for this is that the size of the flange is the same for both through-hulls. Therefore, there is more space between the bolts holes and the 3/ inch through-hull head.
My next task was to countersink the heads of the bolts. For this I again had to rely on my Milescraft brand right-angle attachment. You'll recall from my earlier posting that when the time came for me to drill the new hole through the new backing plate I had to purchase the Milescraft attachment. I needed the traditional screw-down chuck of this Milescraft attachment to hold the hole saw. Now I needed this chuck again to hold the countersink bit. Of course, the whole reason why I needed a right-angle attachment in the first place was because the bunk of the trailer impeded access to the work area with my Makita power drill.
The last area on which I focused was under the galley sink.
This through-hull would serve as a drain for the galley sink.
As with the first two through-hulls, I wanted to make sure that the handle on the in-line valve would be oriented correctly after I had mounted the flange on the backing plate. I decided that the orientation you see pictured below would allow the easiest access and would not obstruct the small storage area forward of the backing plate. The shelf you see is a modification that I was in the process of making for the purpose of utilizing a lot of wasted space in this compartment. Notice that I have drilled two holes in the plywood. One is for the sink drain hose. The other is for the freshwater tank hose. This picture should give you a good idea of the interconnectedness of many of these projects. I had to solve problems on at least two different projects before I could get to this stage of this project.
Satisfied with the orientation and alignment of everything in this space, I removed the in-line valve and prepared to drill the holes.
Despite the size of the space, I was able to use the Makita power drill in an unobstructed fashion. I drilled the first hole with the flange in place.
Then it was on to the second one. Again, I kept the flange in place.
I did the same for the third hole.
Afterwards, I screwed everything down. Stepping back and taking a look, I thought it wasn't so bad. This through-hull was easier than the last one, and it was far easier than the first one.
All that remained was the countersinking of the heads. Fortunately, the bunk of the trailer did not offer an impediments to my progress.
When countersinking these holes (and the other holes for the other through-hulls), I obviously took my time and made sure not to countersink them too deeply. After all, the point is to have plenty of fiberglass to support the heads.
For each hole I tended to sink the head 1/16 of an inch beneath the surface of the hull. I emphasize the word hull here. There is, of course, bottom paint on the hull. I did not include this in my calculations, since I intended to cover the whole work area with bottom paint when I was finished.
After I had finished working on the galley sink through-hull, I returned to the raw water intake through-hull for the head. I had not been fully satisfied with the way the head of the through-hull was seated in the chamfered hole. Therefore, I broke out the Dremel and made some fine adjustments.
I was much more pleased with the fit after I had made these fine adjustments.
I took a few close-up pictures to remind myself how it all looked.
These cracks and holes, of course, would soon be filled with adhesive/sealant.
As I said earlier in this posting, I found the oak stick method of screwing and unscrewing the through-hulls to be effective, but only to a certain point. The wood tended to slip off of the small nubs within the through-hull. As an alternative, my buddy devised a modified step wrench using the tools you see pictured - the combination wrench and the vice grip. It worked very well.
The last bit of drilling that I did on these holes consisted of using the countersink on the interior. I did not go crazy with this. I simply put a slight bevel on each hole. I did this at the advice of Maine Sail, who argues that this is beneficial when the time comes to apply the adhesive/sealant. The idea is that the adhesive/sealant will form a small gasket around the hole.

For the large through-hull I again had to take special steps to get the job done. The Milescraft right-angle attachment was essential. There was no other way for me to access these holes.
When the day was done, my good buddy and I decided to celebrate the completion of this part of the project with some wings and beer. Not a bad way to spend a Sunday.
This ends this posting on how I drilled the bolt holes for the new bronze through-hulls that I would install on Oystercatcher, my Ericson 25.

No comments:

Post a Comment