S/V STRIDER 2010 Winter Project
Cabin Heat and a New Table
There weren't supposed to be any projects this year! After two winters of nearly full time work on the boat I was ready to do something else. She was in shape for a quick splash and departure next spring. I wasn't too upset, therefore, when the wharf owner told me he needed the space and I lost my boat shed. Strider went back to Yankee Marine and was shrink wrapped to hibernate until spring.
The December cold snap that extended all the way down to Florida and the memory of the damp wet of last May's cruise got me thinking about cabin heat and I found myself inexorably slipping into commitment to my largest and most complex upgrade yet. After a couple weeks of pondering various alternatives, I decided that the solid, radiant heat of a unit in the cabin was preferable to the thin heat of a complex and expensive hot air or radiator system even if it did mean a major rearrangement of my interior. It would also be about half the price.
I installed this highly regarded Dickenson Newport diesel heater since I can carry a lot of diesel and it's the fuel that is available almost anywhere.
This unit has a water coil that will provide hot water so I can save boat stove alcohol heating water for dishes and have hot showers without having to hook up to shore power. The installation was very complex to design due to fitting it into an existing boat that wasn't planned to have a cabin heater. I needed to have a water tank above the heater so that water would circulate water by convection in order not to have the power draw of a circulating pump or need to shut the heater down in the event of pump failure. The solution was to make the heat shield for the heater and flue pipe a thin water tank.
This tank is set off from the bulkhead so also serves as a heat radiator with 12 square feet of surface that will significantly increase the efficiency of the heater as well as continuing to heat the cabin for a few hours after the diesel heater is shut off. It wasn't practical from the standpoint of either weight or money to make a tank of this shape capable of holding the boats water service pressure so it is a vented tank that operates at atmospheric pressure. This also avoids problems with expansion when the water heats up.
Turning off the valve behind the small hole to the left of the flue and opening the one in the middle of the three pipes at the bottom allows water to be circulated with a pump through a heat exchanger loop in the boat's main hot water tank.
This piping under the head vanity allows the hot water faucet in the head to be switched between the regular system and to draw small amounts of heated water from the bulkhead tank for washing up.
The three way yellow valve selects between the gravity feed from the bulkhead tank coming in at the top and the pressure water system coming in from the hose at the bottom. The small silver valve is for filling or topping up the bulkhead tank. The three pipes from the previous picture connect below the shelf. The bulkhead tank overflow goes back to the main water tank through the hose at the top bulkhead penetration and the two lines to the main hot water heater loop are on the left. The red valve is for draining the bulkhead tank completely back to the main water tank.
Strider's head has a 3" dorade vent cowl vent in it which keeps it nice and fresh but just a little bit too fresh on cold mornings. I like a warm head so the cabin heater is mounted on an 1/8" aluminum "pan" and a hole is cut in the head bulkhead. This will pump heat into the head and also provides access to the piping.
The two fittings in the middle are the connections to the Newport hot water coil which extends through the aluminum mounting "pan".
The last task in this project was installing this grill to cover the heat vent to the head:
The bulkhead tank and mount were beautifully constructed by Casco Bay Welding and were painted with high temperature stove paint that was a good match for boat's interior
You can get an idea of the complexity of the design and piping layout from this drawing:
The circulating pump for the loop that heats the main hot water tank:
It is not a marine unit but a nifty little pump made for the solar heating industry. It's intended to be connected to a solar panel so as to automatically turn on and off and circulate water through the collectors only when the sun is shining.
There is no motor as such and no bearings, shafts, seals, or brushes. A circuit board has a ring of projecting metal rods that surround a magnet in the pump. The electronics create a rotating magnetic field that spins the pump rotor which is completely sealed from motor. I'm sorry I forgot to take a picture of it before reassembling it with silicone to waterproof the electronics. The pump has no mounting brackets so I fabricated the brass mounting with vibration isolation. The pump is very quiet but it was easy to add the soft plastic washers.
Current draw is just .42 amps and if debris should jam the pump rotor, it won't burn up or blow the fuse due to the electo / magnetic drive.
The smoke head is a discontinued ABI unit that can be sealed watertight with a flush deck plate when the "Charlie Noble" is removed. The latter screws solidly into place so is less likely to be kicked overboard. This was an expensive and painful purchase dictated by the need for the flu to exit in the middle of the main sail hoisting and reefing area. I need to be able to remove the smoke head and stand in that spot.
Jim Ledger turned the beautiful mounting pad out of a still un-identified piece of tropical hardwood. You can see how I shaped the bottom to fit the cabin top here.
The heat shield where the flu goes through the cabin top:
You can see the scaring of the bulkhead where the folding table and shelf unit was removed. Covering up these scars without undertaking the complete refinishing of the bulkhead was another purpose of the water tank.
The cabin heater is supplied with diesel fuel by this tank, also built by Casco Bay Welding.
This is another multi purpose item. It was installed under the end of the quarter berth (converted into a gear storage area last year) and is connected into the discharge from the fuel polishing system so that it is constantly being refilled with just filtered fuel.
Fuel goes into the tank at the middle connection and overflows back to the main tank at the top. The supply to the cabin heater is at the bottom. To refill the tank if the heater draws it down, I only need to turn on the polishing pump for a few minutes. No need to watch for when the tank is full, it's self regulating. Forget the pump and the fuel just gets a little cleaner. The tank also serves as a 1 hour reserve of fuel if the main tanks should be sucked dry since there is a cross over from the polishing system to the engine supply. The complete fuel schematic can be seen here.
The copper line at the top goes to a vacuum breaker which lets fuel flow back out of the tank to the stove or engine.
A Forespar Marlon MF 841 Vent/Duck Bill replacement kit for their anti-siphon vent loops fits a 1/4" compression fitting like it was made for it. Another compression fitting goes on the tank and the copper tube is run as high as possible. Air trapped in the tank top and tube will keep fuel from reaching the valve.
The tank with the hull liner replace showing the removable panel for valve access:
Finally, for the heating system, here is the the filter for the heater. It came without any provisions for mounting so I fabricated brass mounts. The flat sided elbows used for the piping are great for easy pipe mounting.
Cabin Table
The new table is supported by a 1" dia. S.S. stanchion between the cabin sole and the overhead with another rail running forward from that and attached to the side of the head longitudinal bulkhead.
The table support also serves as a guard rail to keep anyone from being thrown hard against the hot cabin heater and as an additional handrail. The handrail tubing was not stiff enough to feel secure or take the impact of a person falling against it without bending. I therefore used the thinner wall tubing for both and inserted and epoxied length of 7/8" dia heavy wall dimensional steel tubing in each piece. The ends are capped with epoxy plugs so the steel is completely sealed from moisture.
A short seizing of rope around the stanchion cushions the table leaves and this simple catch holds them together with the stanchion preventing swinging:
The wood block that supports the pin has a felt surface since the tables can slide along the rail making for a very flexible interior arrangement.
The simple hinge design makes for a very narrow table when folded down and the interior of the cabin did not feel a bit obstructed or cluttered as I feared it might. I'm very happy with my winter's work.
April 25.
I ran the heating system all day today while working on the bottom and other
projects.
Started with gravity circulation to the bulkhead tank. The top was noticeably warmer than the bottom within 15
minutes of getting the Newport started. The gravity feed hot water to the head was comfortably warm in an hour,
normal washing temperature in two, and almost two hot in three.
I then switched over to the circulating pumped loop to the main hot water tank. Four hours got the pressurized
hot water to what felt like about half the temperature you would want for a shower but it's definitely working.
The estimate of 8-10 hours at the outset for heating up the main hot water tank looks like it will be pretty close.
I could have taken a shower at the temperature it reached but it would have been barely tolerable running full
hot.
A pleasant surprise was still being able to get hot water in the head with the main tank circulation loop going.
The flue throws off enough heat that is soaked up by the bulkhead tank that the temperature didn't seem to go down
a bit.
There was some boiling and burping with the circulating loop running but some tweaking of the flow rate should
minimize that. The gravity loop to the bulkhead is absolutely quiet as the thermally driven circulation is self
regulating.
The only thing that didn't warm up as much as I expected was the head. The aluminum panel behind the stove doesn't
get very hot, at least with the boat's skylights wide open to dissipate the heat. I needed the hole and the removable
screen for piping access anyway. When the heater has been running for a couple days, I think it will still take
the chill off the head.
