SJ23 Tech Tip C07 - Cozy Cabin Bulkhead Heater and Vented Propane Locker.

Using a cooking stove to heat your cabin may be quick but it's also dangerous due to the lethal carbon monoxide gas that quickly accumulates in a closed cabin. If you adhere to this practice you will likely find yourself on the list of those who visit St. Peter each year, in which case you better know the answer to the secret question or he's not letting you in! Succumbing to carbon monoxide poisoning is very preventable. The other problem of heating with a stove is the moisture an open flame produces. A purpose made cabin heater with a chimney to vent dangerous exhaust fumes outside is safe and clean, assuming you allow make up air to enter the cabin.

The Cozy Cabin Heater is designed to operate when the boat is on a relatively even keel but an occasional roll from a wave doesn't bother the flame as it can stay lit and the chimney draft isn't affected. I've turned this heater on it's side and the burner stayed in place, which is remarkable since it is held in place by gravity. Before I installed my heater I operated it at 30⁰ for 15 seconds. It continued burning without a problem but the draft was reduced. Continued operation with a boat heeled over like this is inviting trouble.

You'll find these heaters used most often at the dock or anchored somewhere in the rain. Check out a rainy anchorage and watch which boat has people onboard. Nine times out ten they'll be on the heated boat, regardless of its size. I've seen people doing maintenance, partying or reading a book. There is probably nothing more soothing than reading a good book in a warm cabin with a coffee in hand. Some popcorn wouldn't hurt either. Makes you feel snug and cozy all over doesn't it? Motoring through the drizzle in a warm cabin is another experience not to be missed. Sometimes I wonder if these aren't the best parts of sailing! Alternatively there is nothing more miserable than a cold, damp cabin to drive you off the water. Given that situation I would much rather be on land where my activity can keep me warm. This is precisely the reason why I installed a heater on Panache.

When the Cozy Cabin heater was introduced in the 1970s it was available in four fuel models, diesel/kerosene or propane/compressed natural gas, with an adjustable heat output of 4000 to 6000 BTUs. To roughly calculate how many BTUs are required to heat a cabin, calculate the cabin volume by (H x W x D) = V ft³, then multiply the volume by 10 if the cabin is insulated, or by 15 if it is not insulated. The SJ23 volume calculates to (7.5W x 16.5H x 7D)=189 ft³, where the required heat is 12,000 BTU. From my experience a Force 10 heater produces adequate heat in the shoulder seasons. I seldom run it on full heat. I even use it during the winter while working on the boat.

PARTS & SERVICE - This 1970s bulkhead cabin heater (Model FT 100 PR OXD) was designed and manufactured by FORCE 10 in Vancouver, B.C. Canada. As of 2000 the unit was manufacture discontinued when the company changed their product line to stoves shown on their web site. Sig Marine now sells parts for the Cozy Cabin heater in Surrey, B.C. (Canada). Email for technical assistance or phone 1(800) 659-9768 for service.

MANUFACTURER INSTALLATION RECOMMENDATIONS for the FORCE 10 COZY CABIN HEATER.

USING THE HEATER - Regardless of which version of Cozy Cabin bulkhead heater you have, they all produce enough heat for an SJ23 cabin. However, the secret to a successful installation is to install a Caframon or other small whisper quiet fan above and to the side of the heater to drive the hot air down to the cabin floor. Now that feels good! This is the only way you will ever warm your tootsies which would otherwise be immersed in the three foot deep layer of cold air below the heater! If the top of the bulkhead is open to the ceiling then you can pivot the fan 180⁰ to send the hot air forward to dry the berth. It's so nice to crawl into dry bedding on a rainy day. The other reason for a full articulating fan is to satisfy all those 'adjusters' out there! I've never seen a fan that somebody didn't want to point in another direction. If it can oscillate, then all the better. By the way, the fan is great for cooling you off in hot weather.
- The height of the flame is adjustable by the red control knob in the photo above. The propane version will operate at full throttle for about 15 hours on a one pound disposable bottle. The diesel/kerosene version will operate about 24 hours on one US gallon of fuel, provided you maintain tank pressure. The propane version can burn unattended till the fuel is consumed. You will have to pump the tank pressure every few hours or so.
- You can restore and preserve the steel top plate of the heater with Stove Polish. This is a paste that easily restores the lustre to a black finish.
- SMART IDEA It is very advisable to leave a hatch 'cracked' open to let some fresh air in. Oxygen deprivation can sneak up on a person, making you feel lethargic and dropping your defenses to where it can be dangerous.
- DUMB IDEA It is NOT recommended to hang wet clothing above the heater. The smart idea is to hang the clothing to the side and blow hot air at it with the fan you installed.
- It is NOT recommended to use the heater while sailing, despite the fact that the flame can stay lit at 30⁰ of heel. The problem is that the hot exhaust gas will escape out the lower side of the hooded vent holes, overheating the wall and dumping dangerous fumes inside the cabin. I can only imagine the problems that can arise when wind and waves combine with fire and carbon monoxide in the cabin. You are welcome to it. The safer thing to do is pack the sails, drop the anchor, light the heater, make a pot of coffee/tea and enjoy life. By the way, this heater will keep a pot of coffee warm. You just have to find a 4" diameter pot that can fit inside the fiddles. I've also heard of people who warm soup on the heater. A can of beans would fit nice as long as you don't let it boil over. TOP

PROS & CONS - The FORCE 10 Cozy Cabin Heaters were manufactured in four fuel types, each with their pros and cons. All are bulkhead mounted. They are now manufacturer discontinued but parts are still available at the time of this writing.

Pros and Cons of Liquid Versus Gas Fuel.
	LIQUID FUEL - Diesel or Kerosene	GAS FUEL - LPG or CNG
Preheat	The burner MUST be preheated by burning a combustible paste spread in the basin under the burner. If the preheat is incomplete (burner too cold to support combustion) then the fuel will not ignite when it comes out the burner. If the burner temperature is almost hot enough then it will produce a low yellow flame that will burn sooty till the burner heats up. The flame may also flare up while the burner heats up. Flaring can be dangerous in a confined cabin and the valve should be shut off immediately. The problem can be minimized with a judicious application of the volume of paste. Soot coming out the chimney will stick to things on deck.	The LPG & CNG versions start immediately, provides virtually instant heat and burns clean all the time. While preheat is not required the flame sensor must be heated during start up which requires you to press and hold the knob for 10-20 seconds. LPG is heavier than air making it dangerous when accumulated in the bilge. CNG is lighter than air, making it safer. Both gasses are very explosive.
Operation	The flame should burn with a solid blue colour. You may see the occasional yellow tipped flame which is OK. The tank looses pressure as the fuel is consumed but with a bit of experience you'll know when to apply a few more strokes on the pump to maintain a hot, clean burning blue flame. Usually every 90 minutes, modified by gas consumption and flame height.	The heater will burn as long there is fuel in the tank since the evaporating gas in the tank is what creates the pressure for the burner.
Fuel Tank	The pressurized tank for the diesel or kerosene versions must be installed lower than the burner as an extra safety measure to minimize the risk of liquid fuel flowing on the cabin floor after the flame goes out. The tank must be installed (clamped) with the hose at the bottom to achieve a liquid feed. All fuel must be filtered to prior to going into the tank.	If you equip the heater with a refillable propane tank, it must be stored in a vented locker. (see propane locker). All styles of propane tanks must be clamped vertical with the valve at the top to achieve a gas feed. The continuous propane supply hose (flexible fire-resistant UL or CGA equipped with 3/8" flare nuts on each end) without couplings or Ts should have an automatic shutoff valve to protect against a leaking hose. Requires a high quality low pressure regulator; 11" water column or .0274bar (.5psi).
Safety	Spilled diesel or kerosene is unlikely to ignite and less dangerous than propane gas settled in the bilge. However, it MUST be wiped up immediately. On land it is OK to use a liquid fuel to preheat the burner. On a rocking boat you must use a paste that can't spill. The starter paste must be lit with a flame from a BBQ lighter or a match, not a spark lighter. See safety note below.	Heater is equipped with an automatic fuel shut off to guard against a flame out or oxygen depletion. If the internal piezo-electric igniter fails to spark the gas can be lit with a BBQ flame lighter (not a spark igniter). Use a flame since leaked raw propane gas will collect in the bilge where it can accumulate to a potentially dangerous quantity. See safety note below.

It is arguable which type of fuel poses the greatest potential hazard. There are pros and cons to each type and your operating knowledge, along with proper maintenance, is key. LPG (propane) is an excellent and convenient fuel if used in accordance with rules, safety and common sense. Neither of the liquid fuels are as explosive as the gaseous fuels but if they puddle that fuel can also be dangerous. Regardless of which type you have, it is a wise to stay awake (both feet on the floor and sitting upright) while the heater is burning. It is also wise to install a carbon monoxide detector in the cabin, especially if you intend to nap, even if for only five minutes! Thankfully not many people can sleep comfortably with a heater burning, however slight the hissing noise of the flame is. The smartest thing that most people do is keep the cabin heated till the sun fizzles below the horizon and then snuff the flame, preferring to rely on the warmth of a good sleeping bag and the comforting knowledge that you won't succumb to carbon monoxide poisoning overnight. In marginal, damp weather I consider the heater both a safety feature and a luxury.

BULKHEAD INSTALLATION in a SJ23 - While an SJ23 has a roomy cabin for its length, there is really only one practical place to mount a bulkhead heater, against the port bulkhead. If you find this spot too intrusive you may want to invest in a portable heater like an Origo alcohol stove that can be placed on the floor. However, if you operate your boat in an area with lots of marginal weather then a permanent cabin heater is the best way to go. The FORCE 10 diesel/kerosene heater shown at right was installed on "Gecko" by the original owner who worked for Clark during the summer. Joe Thomas now owns her and has sailed her out of Seattle for many years. The FORCE 10 propane heater shown below was installed on "Panache" by Bob Schimmel. TOP

FIRE PRECAUTION - Fire at sea is the most feared of all hazards for a sailor. There is virtually no way to escape from it. Going over the side it hardly a solution and riding it out in the dinghy is only marginally better. Fire prevention is everything. For this reason you MUST install this heater with ALL the safety precautions recommended by the manufacturer in the manual, plus any other that are required by the unique requirements on your boat. This is your responsibility to figure this out and definitely NOT a time to make a short cut.
Check gas connections for a leak at the start of each season and whenever else you think it necessary. Turn the heater valve OFF. Open the gas valve of the supply tank. Note the pressure. Shut off the gas tank. The pressure should stay constant for 10 minutes.

THERMAL PROTECTION for TABLE - A forward section of the port leaf of Panache's table was cut out to clear the body of the heater. Ooh it hurt to cut such nicely finished wood work! However, the cut out section created the required 2" air gap around the heater, thereby keeping the edge of the table cool when it is up. Long term heating of the table fiddle shouldn't be a problem. However, I will apply reflective aluminum tape to the fiddle as a precaution. I may not be onboard if someone else operates it! The top metal plate radiates lots of heat sideways and a lot of hot air passes out of the heat exchanger holes at the top. The flame also radiates heat sideways but not nearly as much the plate and the holes at the top. At the height shown in my installation, it is quite easy to light or service the burner, which is an important consideration.

THERMAL PROTECTION for BULKHEAD - Use high temperature fiber washers under the mounting feet to insulate them from the bulkhead (shown below). To keep the bulkhead cool I mounted sheet metal behind the heater (shown at left) but I've also seen ceramic tile used. This is important if you operate the heater for an extended time, especially if it's a really good book! If you use sheet metal, install it loose against the wall so the slight air gap behind it can't conduct the heat to the bulkhead. Most of the heat will be reflected if the sheet metal is shiny. Panache's installation shown above is polished aluminum (light sand paper) and the wood bulkhead always stays stone cold. Maybe I'm anal about this stuff but I regularly check the heater for over heating while it runs. TOP

STACK - The chimney stack doesn't have to go straight up as shown in Joe's installation at left. To keep hot exhaust gas away from poly deck lines I installed Panache's deck cap about 8" off to the side of the heater. This was beyond the limits of a bender so I cut the stack in two places, 30⁰ each, and welded the assembly back inline. Polishing was accomplished with a Dremel tool using successively finer compounds. As an alternative to offsetting the deck cap you could use a straight stack and raise the deck cap above the deck lines with a thick wood spacer ring. The extra height has the added benefit of keeping more solid water out. As you can see in the photo below I offset the stack and raised the deck cap.

If you want to make smooth bends then use a stainless steel tube bender on the stack. Don't use an electrician's conduit bender as it does not grip the tubing which will kink it due to the properties of stainless steel. An alternative to bending is to cut and weld the tubing, especially if the desired turning radius is tighter than the limits of the bender, which is usually a 5" radius. Grind the welds smooth to eliminate hot spots, meat hooks and to improve the cosmetics. The maximum number of bends allowed are two, 45⁰each. You could split a single 45⁰ bend into two 22.5⁰ bends to achieve a smoother transition, but this complicates the welding more and adds to the labour. Still, certain installations might require it. Leave about a 1/8" air gap between the end of the stack and the bottom inside of the cap for thermal expansion. This helps to protect the cap from being pushed up off the deck and maintains the deck seal.

THERMAL PROTECTION for the CHIMNEY DECK HOLE - The deck hole for the chimney must be 2" ID which creates 1/2" clearance all around the 1" OD stack. A hole saw is perfect for this job. Drill half way through from the top then finish the hole from the bottom. The ceiling finishing ring is missing on Joe's chimney at right but it illustrates the installation. Seal the exposed deck core in the stack hole with epoxy to maintain the strength. If the cap is to be installed where you expect solid water to come over the deck, then I suggest using at least a 2" thick wood spacer ring to minimize the amount of water that can find its way below.

Taper the sides of the ring to 30⁰ so a deck line can slide over the cap. The cap is fastened to the top of the ring with three wood screws and a fibre thermal washer between them. Do not use sealant here. The wood ring is fastened to the deck with three wood screws from below (inside the cabin) and sealed with Sikaflex to the top of the deck, forming a fillet around the base of the ring to keep water out. The thickness of an SJ23 deck adjacent to the mast is 5/8". Remember to face the cap opening aft to keep spray out. Position the bottom ring mounting screws between the cap screws for maximum strength. The stainless steel inside finishing ring also keeps the stack centered in the deck hole and in the chimney cap. Use it as a template for the bottom ring mounting screws. Judging from the cap diagram the chimney stack ends right at the top, inside the cap. This keeps the exhaust fumes from entering the cabin, protecting the crew. With all the exhaust gas evacuated outside, the deck hole should stay relatively cool. A favourite trick is to line the perimeter of the deck hole and wood ring with thin aluminum or stainless steel sheet metal. The metal reflects most of the radiant heat keeping the deck cool. This is very important if you operate the heater for an extended time. If the chimney stack is a wee bit short of the cap then stuffing loosely crumpled aluminum foil inside the deck hole should create a seal to prevent fumes from entering the cabin. If you ever have to service the heater or the stack, remove the heater from the bulkhead and allow the stack to drop out of the cap. This maintains the water tight integrity of the cap to the deck. If you have to remove the cap then release the three screws on top of the ring, leaving the wood spacer ring sealed to the deck. If the cap is sheared off in an accident, seal the deck hole with a rag or tapered wood plug. Now aren't you glad you sealed the edge of the deck hole with epoxy! TOP

WHERE TO INSTALL THE DECK CAP (Charlie Noble) - Remember to mount the deck cap with the opening facing aft and to use a hard wood ring under the cap for thermal insulation to the deck. If you sail in an area where you expect to receive lots of spray or solid water over the deck, then make this ring at least 2" thick to minimize the amount of water that can flow down the chimney. The higher the cap is off the deck the less water you will take in. Use Sikaflex to seal the ring to the deck. Coat the ring with Sikkens Cetol Marine as this is the only finish that will survive the heat of the chimney whereas varnish will flow off. Install guard rings over the deck cap so you have to make fewer trips to release a snagged line. Keep in mind that the system isn't perfect! I don't want to hear any swearing about this!
The cap at right belongs to Joe's boat. The cap to the left belongs to Panache. The spacer and guard rings are my design. For service I simply remove the guard rings and cap screws. The spacer is fastened with screws from the bottom, inside the cabin, and sealed to the deck with Sikaflex. I doubt the spacer ring will ever be removed. The reason why I used such a thick spacer ring is to vent the hot exhaust above the deck lines. If I ever kick it, well the spacer can stand up to the force better than the cap and I will probably utter a few words in the process! So far it is totally out of the way. I'm happy about this because I spent a fair amount of time assessing this location, going through all my usual motions and contortions. I found this spot to be ideal for both venting and foot clearance. It's not often that you can satisfy all requirements. TOP