Relocate Holding Tank and Batteries (Nov-Apr 2001/2)

“A piece of cake”

We had sensed, for a long time, that the boat sailed with its bow down in the water. This was also obvious from the pictures of the boat sailing. This, we deduced, was due to the fine entry of the hull and the location of the holding tank in the v-berth area of the hull. Whenever the holding tank was empty, we could measure a better performance level.

We examined the possible spaces in the boat that could be used to relocate the holding tank to a more rearward location. We found an “under- utilized” space on the port side, aft and below the bunk board and forward of the stove compartment. This space was about half consumed by a too-large battery box. The other half was empty and used to store the hatch boards while we were underway. We carefully measured this space and found that an available holding tank would, probably, fit in this space. This tank, a Kracor, PN 2-73821S, 21 gallon capacity, seemed to be designed to fit this space.

The installation of a tank in this space is dependent upon relocating the two batteries to another location. We found a smaller space, below the stove compartment, with a door, that is large enough to slide a battery through. On the left is a view looking down into the space with the stove compartment removed. This space is adequate for the two batteries. We built a suitable floor and installed two battery trays, with hold down brackets, in his space. We also relocated the battery cables.

On the right is a view looking aft into the new battery compartment. During installation, one battery is slid inside the compartment, clamped in place and the cabling is attached. Then the second battery is slid into its mount, secured and the cabling is attached. Each positive terminal is protected by a red plastic boot. 

Having found a place for the batteries, we carefully studied the space to assure that there is enough space for the chosen holding tank and its fittings. This included making a foam core mockup of the tank, based on the dimensions given by Kracor and fitting it onto the space. With the assurance that it would fit, we ordered the tank.

The space required some modification to accept the tank and its fittings. The fore and aft centerline rib is cut down so that it supports the bottom of the tank and lateral ribs are added for further support. The ribs are bonded to the hull with 3M 5200 adhesive. The forward athwartship rib was cut down to allow insertion of the tank and to clear the fittings on the front of the tank. The inside surface is painted with Interlux Brightside Polyurethane paint.

The bunk board that covers the tank space had been supported by the fore-aft and athwartship hull ribs. To provide this support, a new frame work is built over the tank space. This frame work, constructed of oak is mounted with fasteners so that it can be fitted after the tank is installed. The picture below shows the tank and frame installation. The frame accommodates the tank vent hose, tank access port, tank inlet and drain ports. We did install a Sealand vent filter to satisfy our olfactory receptors.

The space forward of the holding tank is still used for storage. See lower picture. The inlet and drain plumbing, which runs through this space, does not interfere with its use. This space also contains the thru-hull fitting and valve for the head supply water. The inlet pipe continues through the main bulkhead and connects to the hose in the head compartment. The drain, pump out, hose continues forward, past the head compartment to the old fitting in the anchor well because we did not wish to create another hole in the deck. This tank and plumbing have performed well since it was installed. 

Once all the bunk boards are back in place there is no evidence of this major renovation.

All of this effort did cure the bow-down problem and improve performance. We did see the boat sail better to windward and through choppy seas on other points of sail. “Keep the weight out of the ends” is still good advice. Also, we said good bye to the old, stinky tank.

{Lessons learned:

1. Make sure that you have measured the space correctly and have good dimensions from the supplier.
2. Make mockup pieces. They are a lot easier to deal with. Measure again.
3. Take time to dry fit all the pieces before you apply any glue.
4. Painting the space makes it more pleasing.}