Plumbing, Head, Part 4, Construction of Panels for Manual Pump, Strainer, and Vent Valve

The epoxy-coated panels for the manual pump, the strainer, and the vent valve
Having installed the stainless steel through-hulls for the holding tank vents on Oystercatcher, my Ericson 25, my next task was to construct the panels for the manual holding tank pump, the seawater strainer, and the starboard holding tank vent valve. All three of these items would be located on the hull, or I should say the hull-liner of the boat. It would be impractical and foolhardy to screw these items into the fiberglass hull liner with wood screws. The hull liner was thin, and it was close to the fiberglass hull. The tips of the screws would either penetrate the hull or they would chafe the hull such that they would threaten its integrity. Therefore, I had no choice but to construct plywood panels that would serve as mounting surfaces for these items. The panels themselves would be joined to the hull liner with hardware that was epoxied in place. In this posting, I focus on my construction of these panels and my installation of the hardware to support them.
As I said, I needed to mount a Whale brand manual pump to the hull liner.
In the picture below, you see that I have temporarily screwed the pump to the hull liner, simply for the sake of helping me figure out where to route the hoses. I discussed all of this in my first posting in this series.
Why did I need to mount this manual pump here? Why not mount it somewhere else, you might ask? Believe me, I thought through many different scenarios before deciding upon this one. The forward bulkhead to the left in the pictures above and below was out of the question. There's no way that I could have routed a hose to it from the holding tank. This meant that the only alternative was the aft bulkhead. This could have worked, but it would have put the pump in a position that was not user-friendly. The person using the pump would not be able to draw the handle back and forth, toward him and away from him. I had used the exact type of pump many times on different tall ships, and I knew that it needed to be in this user-friendly, hull-mounted position.
In terms of the seawater strainer/filter, I had purchased a Groco brand strainer. It came with an aluminum mounting bracket that allowed the strainer to hang free of the hull.
I planned to install the bracket in the area indicated by the oval in the picture below. Again, I should note that I considered various alternatives before settling on this hull-mounted position.
In the hanging locker on the port side of the boat, I had installed a valve for the port side holding tank vent. At the time, I thought that this valve would not need a mounting panel. As we shall see in a later posting, I was wrong.
On the starboard side of the boat, I also planned to install a valve - this one for the starboard holding tank vent. This valve would need to be located on the hull. There was no way around it given the orientation of the hoses that would join it.
The most challenging panel to construct by far was the one for the manual pump. It needed to be big enough to distribute the load that the pumping action would impose on it; it needed to be thin enough to conform to the curvature of the hull; and at the same time it needed to be thick enough for mounting the pump housing to it. After much contemplation, I decided to construct the panel of two different pieces of 3/8 inch exterior grade plywood. The smaller piece would reinforce the larger one at the lower end, where it was most needed. The large, unreinforced piece would be thin enough and long enough to conform to the curvature of the hull.
I wanted the corners of the panel to be rounded, so I used one of the old bronze through-hulls to scribe the appropriate arcs.
Always seeking to wed the practical with the aesthetically pleasing, I decided to make the panel for the seawater strainer of a similar size and appearance to the reinforced portion of the manual pump panel.
I also contemplated an arrangement that would give the two adjacent panels a more pleasing appearance.
In terms of the manual pump panel, I decided that a good way to give some curvature to it would be to weigh it down with dumbbells and let it sit in a bridged position for some length of time.

Meanwhile, I focused on the size and position of the vent valve panel relative to the seawater strainer panel.
After a sufficient length of time had passed, I epoxy-coated the panels.
Each one got two coats of epoxy.

I allowed the epoxy to cure, and then I sanded each piece.
My plan was to paint these panels with two part polyurethane paint, so I needed their surfaces to be smooth but textured to receive the paint.
As far as the mounting of the manual pump panel was concerned, my plan was to use perforated base studs. I had ordered these 1/4 studs from McMaster-Carr in Atlanta, Georgia. These studs were 316 stainless steel and the company that manufactured them was named Rotaloc.
My first task was to figure out where to install the six studs that would secure the panel to the hull liner. The two sets of studs above and below the manual pump could not interfere with the two sets of mounting legs for the pump. These mounting legs would be very close to the studs, so it was important for me to be precise.
I used the long panel as a template of sorts to figure out the measurements.
I also used the long panel as a template for marking the hull liner. Before I took the panel to the boat, I drilled pilot holes through the six marks where I planned to install the six studs.
I then marked the hull through these pilot holes and drew reference lines.

I used the reference lines for the manual pump panel to determine where to draw the reference lines for the seawater strainer panel.
Then, in turn, I used this second set of reference lines to draw the reference lines for the vent valve panel.
Afterward, I returned to the manual pump reference lines and made more detailed marks.
At last, I knew exactly where I needed to mount the perforated base studs.
Now I needed to sand away the gelcoat, so the studs would have a clean fiberglass foundation onto which the epoxy could bond.
As I said, these studs were manufactured by Rotaloc.
I used my Rockwell Sonicrafter to sand away the gelcoat in the six spots.
The acetone removed the dust and revealed a nice, clean surface for the studs.
After I was finished, I re-marked the center of each circle to create a reference for the mounting of the studs.

Some of the studs were longer than they needed to be, so I cut them down to size in advance.
Yes, a Dremel with a reinforced cutting wheel will cut through a 1/4 inch 316 stainless screw, but it takes some patience. On another project on the boat I had burned up a Dremel trying to do this too quickly.

To secure the studs to the hull liner I used Devcon 5 minute epoxy.
I'll say right now that this product does not always live up to its advertised PSI strength.
In my experience with this project (and another project on this boat), you cannot tighten down the nuts too much on these studs, if you have glued them to wood, and yes, I was meticulous in my following of the instructions for the application of this product.
Maine Sail, that well known writer on the various sailing forums, had sung songs of high praise for Weld Mount - an epoxy product that actually stands up to a lot of abuse. I considered purchasing Weld Mount from Jamestown Distributors in Rhode Island, but I decided that it was prohibitively expensive for someone like me who only needed it for a few studs. It certainly made sense for someone like him, being the marine professional that he was, and if I had to mount things on the hulls of boats all the time like he does, then I would have made the investment.
I would install six of these studs on the hull liner with the Devcon epoxy. Interestingly, not a one of the bonds for these studs failed, not even the ones for the two studs at the middle - the ones that received the most abuse in terms of the torque I put on the nuts. It was, as we shall see, the bond on the wood for one of the legs of the pump that failed.
Now back to our subject. Below you'll notice that the stud on the right is not perfectly aligned with my reference marks.
Despite my best efforts to center the studs on the marks, some of them were slightly off. Therefore, I had to drill out the holes in the panel to a larger diameter.

I gradually increased the size of the holes until they were all 1/2 inch in diameter.
At last I was able to fit the panel on the studs.
Then I began to tighten down the nuts. The studs in the middle held up to my tightening down of the nuts, even though this was the area in which there was considerable stress due to the curvature of the hull. Yes, the panel itself was bowed, but it was not bowed as much as the hull.
Back at the work table, I used a pen to mark the holes I needed to drill in the small reinforcement piece.

These holes, of course, were for the studs on the hull.
Afterward, I drilled holes in the small piece of wood for the pump's mounting legs. Then I used these holes to mark the large piece of wood.
On these marks I placed the studs for the legs of the pump.

Then I whipped up another batch of the Devcon 5 minute epoxy.

It was the bond for the top left stud that would eventually fail when the time came for me to tighten down the nuts.
Onto these studs I placed the small piece of wood - but only after I had enlarged the holes so that the piece could fit. These studs, like those on the hull, had shifted slightly during the glue-up.
As a result, I had trouble mounting the legs of the pump on the studs.
I had to enlarge some of the holes with my drill in order to achieve a proper fit.
In the boat, I installed the entire pump and panel assembly. I thought it looked good. Everything seemed to be coming together well. The assembly was solid, and the hull liner did not flex or bow when I pulled the handle of the pump back and forth.
This convinced me that my choice to mount the pump in this location was a good one.
My sentiment about this was only strengthened when I temporarily reinstalled the old toilet and saw that there was plenty of room for the lid of the toilet to swing backward. The position of the lid also confirmed that my choice for the location of the other two panels that I would soon install was also a good one. From a visual perspective, the seawater strainer and the vent valve would be easy to see and inspect, even with the lid up.
Now I could focus on the mounting of the studs for the seawater strainer . . .
. . . and the holding tank vent valve.
I double-checked my marks.
Then I got to work with the Rockwell Sonicrafter.
Now it was time to clean up the area and glue the studs into place.

This time I used Ace brand epoxy, which, if I recall correctly, had a higher PSI rating than the Devcon.
It had the same blue and white appearance as the Devcon.
The disappearance of the blue indicates that you've mixed the two ingredients together thoroughly.

It took several batches.

I had to widen some of the holes with the drill, but soon both panels were in place.
To disguise the holes, I used fender washers underneath the nuts.
Now I could start to snug down all the nuts.
All was going well until I snugged down the nut for the top left leg of the pump. All of a sudden I heard a pop, and I realized that the bond had failed. In the picture above and below you see a yellow circle. I should have placed the circle a little lower. It wasn't the stud at the center of the circle, but the one just beneath it.
I removed the panel-pump assembly from the hull and took it back to my work room. There, I disassembled it and inspected the studs. It was obvious that these studs with this Devcon epoxy would not bond well to wood, even if it had been fully epoxy-coated and sanded.
With a chisel and a dead blow hammer I removed the other studs.

My remedy for the problem was to drill holes and install the studs on the backside of the large panel.
You might ask how I planned to secure these studs to the backside of the panel.
I had no choice but to secure them to the back of the panel with epoxy soaked cloth. More on this later.
More important to me at the moment were the studs on the hull of the boat. These had never failed, but I did worry about the two studs at the center of the pump panel. These were the ones that had to bear the bulk of the load whenever I worked the handle of the pump back and forth. These were also the ones that pulled the panel inward in an arc that corresponded to the curvature of the hull. This arc or bow was one of the things that gave this panel its strength.
I decided that it would be smart to reinforce these studs with epoxy soaked cloth to ensure that they never broke free from the hull. Therefore, I broke out the quarter sheet sander and removed much of the gelcoat around these studs.
I also figured that this cloth would give additional strength to the hull liner and thus further reduce the chances that the liner would flex when I employed the manual pump.
As you can see in the picture above, this sanding of the gelcoat created an incredible amount of dust.

I cleaned up the work area with xylene, and then I broke out the 12 ounce biaxial cloth.
I cut three pieces of biax to the appropriate size.
Before I laid up the cloth, I wet-out the bare fiberglass with neat epoxy. I used RAKA 127 resin and 350 non-blush hardener.
Then I laid up each layer of cloth, one layer at a time, soaking each layer of the biax with neat epoxy before laying up the next.

Since I was doing this work on a vertical surface much of the neat epoxy ran down the hull liner. The plastic helped to block any drips from my brush, but not those drips on the hull. I had to monitor the work area for almost an hour to clean up all the drips with acetone before the epoxy hardened and clean-up became impossible.
I was satisfied with my work for the moment, and decided to move on to other things.
Specficially, I moved on to the securing of the studs to the back of the panel with cloth.
Yes, it was ugly, but it did the job, and no one would ever see it.
A day or two later I dry-fit the pump onto the studs.
Some of the epoxy from the backside had crept through the holes. I had to remove this epoxy before I could obtain a good fit.
Now that I had mounted the studs to the backside of the large panel, there was no reason for me not to glue the small panel to the large one with epoxy.
For this, I called upon my old friend named RAKA.
First I wet-out the pieces.
Then I thickened-up the neat epoxy with colloidal silica.
I used clamps to ensure a good bond, especially since these panels were, by design, slightly bowed.
Afterward, I used the leftover epoxy to create a fillet around the joint.
A day or two later I used my sanders to smooth out all the cured epoxy.
The Dremel was a big help in cleaning up the rough edges of the fillet.

Sanding the cured epoxy in the boat was not fun. The biaxial cloth was like concrete. The dust would have been unbearable without my respirator, mask, gloves, and long-sleeved shirt.
There was no way in hell those studs would ever come off that hull liner.
Afterward, I added a few finishing touches to the panels.
I could have stopped here, but why not make these panels look like they truly belonged to this beautiful boat? That's what I thought. Therefore, I broke out the Pitthane two-part polyurethane and got to work.
I've spoken many times about this paint, so if you'd like to read more about it, just click on the word Pitthane in the Labels sidebar.
I applied the first coat to each panel.

The next day I lightly sanded the panels with 100 grit paper to remove the imperfections and give the surface some "tooth," as they say.

Afterward, I used the thinner to remove the sanding dust.
This thinner is essential, not necessarily for this task but for the thinning of the paint. Without it, the paint will not lie down.
I always use a new tray and roller for each batch, whenever I use this Pitthane. I also always wear my respirator and heavy duty nitrile goves. This stuff packs a punch. Thin blue nitrile gloves dissolve quickly when they come into contact with the thinner.
The second coat of Pitthane brought this lengthy project to its conclusion.

This ends this posting on my construction of the panels for the holding tank manual pump, the seawater strainer, and the holding tank vent valve for Oystercatcher, my Ericson 25.

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