Kemana Modifications

Kemana's Modifications

Sink

Holding Tank

Raymarine Autopilot

Rudder Skeg

Hard Nesting Dinghy

Solar Panels

V-Berth

Icebox

Shower

Sink

The sink in the head was built using the existing cabinet door, and a stainless steel mixing bowl. It hinges closed, flush into the port cabinet, and is high enough that the through hull drain does not need to be closed on a starboard tack. Stops on both sides prevent the sink from hinging too far out.

Holding Tank

The fresh water tank in the keel is often broken or unused in the Douglas due to poor upkeep. Kemana's tank had a large chunk missing at the aft end, and was holed near the lead ballast from a lighting strike. It was very foul with bilge water for many years, and rather than try to clean it, it was converted to a holding tank for the head. This allowed the removal of the old holding tank under the V berth, freeing up a lot of storage space there. Since it is below the level of the head, there was no need for a vented loop in the plumbing.

A large section of the floor had to be removed for access. The tank is only held in place by a thin layer of fiberglass along each side that is easily cut. The tank is too large to be moved outside the boat through any hatch, so repairs must be made in the main cabin. The holes were filled, and inlet, vent and pump out pipes were added to the front of the tank.

Tank removed from the keel

Floor cutout revealing previous modifications to the water tank.

Notice that the floor is wider on the starboard side!

Rear section of the tank being repaired with fiberglass panels.

Holding tank level indicator idea:

Most holding tanks have the 1.5 inch pump out hose reaching to the bottom of the tank.

As the tank fills, each inch of this hose holds 1.76 cubic inches of water.

1 cubic foot of water weighs 62 lbs, so this 1 inch of water weighs 0.063 lbs.

To push that 1 inch of water down the hose, you need 0.036 lb / sq inch air pressure. ( 0.063 lbs / 1.76 square inches, the surface area if the hose ).

To push the water down a foot, you need 0.43 lb / sq inch (0.036 x 12 ) of air pressure.

( picture putting a styrofoam plug in the hose, and weighing it down with 3/4 lb of ball bearings )

Adapt a spare screw cap for your deck fitting, and add a low pressure gauge, and a tire valve. Pump air into the tightly sealed cap ( bicycle pump), and the air will push the water down the hose. When the air pressure is high enough, all the water is pushed out of the hose.

Read the air pressure gauge. If your tank is 24 inches deep, and the gauge says 0.8 lbs, then your tank is full.

Raymarine Autopilot

The compass was removed, and an aluminum plate and resin box were added to house the autopilot display and the engine instruments ( moved from the side of the cockpit ). Engine RPM, temperature, oil pressure, depth, fuel, and ignition switches.

Rudder Skeg

The small skeg in front of the rudder was shaved off to try to get less turbulence around the prop / rudder. My bronze prop has cavitation pits. ( pitted pockets in rows near the tips ). My 10 inch prop doesn't get enough bite ( revs go up, but speed doesn't increase ). My 12 inch prop is ok forward, but does not slow the boat very much in reverse. This mod helped docking by giving a little more power in reverse, but the prop walk is still pushing the boat to port, away from the dock on starboard. This mod was done for the 2016 season, I will try the 10 inch prop for the 2017 season..

Solar Panels

As seen in the above photo, the two 100 watt flexible panels are attached to the top of the dodger using aluminum channels on the underside of the fabric. There is an LED light built into the middle aluminum channel to provide cockpit lighting..

V-Berth

Ikea 6.5 inch queen foam matress, covered with outdoor upholstery fabric.

Icebox Conversion

Photo below, shows the existing updated foam insulation. A combination of 2 inch foam board and spray foam was revealed when the cutout was made to insert the fridge unit.

The Waeco unit draws 4 amps, for 6 minutes, twice an hour in 80 F weather. ( 4 x 12 x 24 = 1152 amp minutes, or 19.2 amp hours per day)

Our two 100 watt solar panels produce these results on a sunny day at anchor:

08 am, 2.5 amps

09 am, 4.0 amps

10 am, 6.0 amps

11 am, 7.4 amps

12 am, 8.0 amps

01 pm, 8.0 amps

02 pm, 7.7 amps

03 pm, 7.3 amps

04 pm, 6.7 amps

05 pm, 3.5 amps

06 pm, 3.5 amps

07 pm, 2.5 amps

Total = 67.1 amp hours per day, so one sunny day can run the fridge for three days.

I used a suction cup inside the bowel to pull it up tight to the underside of the floor while the glue set.

Add a Rule pump, hand sprayer, a screened lid, and some hot water!

If you make this modification, try to use a larger bowel, as this one needs to be over-filled to work well.

Test the fit through the v-berth floor opening to see if your larger bowel would fit.

I don't know the original manufacturer of this manual windlass, but it is currently sold by Italwich (https://www.osculati.com/en/11018-m-029260/italwinch-giglio-manual-windlass). The 40 year old bronze capstan is badly worn, causing the chain to slip, and a replacement is unavailable. I drilled and tapped the capstan to add 5/16 cap screws to fix the slipping chain.