|SJ23 Tech Tip C07, (Reissued 2009-05-18, Bob Schimmel, Joe Thomas & Jim Thompson)|
A cabin heater gives you more early and late season time
to enjoy your boat. You can be comfortable onboard while others stay
home. It is probably the most comfortable way to extend your sailing into the shoulder
seasons. A warm, dry cabin can change a marginal day into a good
day and we all know that any day spent on the water is a good one.
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 that an open flame produces. A purpose made bulkhead cabin heater with a chimney to vent the dangerous exhaust gas outside is safe and clean, assuming you allow make up air to enter the cabin.
A very popular cabin heater for a small boat was the original bulkhead version manufactured by FORCE 10 in the 1970s They are fuelled by diesel/kerosene or propane/compressed natural gas. These heaters are designed to operate when the boat is on a relatively even keel. The occasional roll from a wave doesn't bother the flame as it can stay lit and the chimney draft isn't affected. However, continued operation with the boat heeled over is inviting trouble. You'll find these heaters used most often at the dock or anchored somewhere in the rain. Just go into 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. Makes you feel snug and cozy all over doesn't it? Motoring in the drizzle inside 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, but then this is one of the reasons why I installed a heater on Panache.
When the Cozy Cabin heater was introduced in the 1970s it was available in four fuel models 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. The SJ23 volume calculates to (7.5W x 16.5H x 7D)=189 ft3, where the required BTU is 12,000. From my experience of using a Force 10 heater in the shoulder seasons, it produces adequate heat.
PARTS - As of 2000 the bulkhead heaters were manufacture discontinued. Force 10 has changed their product line to stoves shown on their web site. Parts are still available from Dickenson at their Surrey, BC (Canada) location. A complete lower assembly is available through them.
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 small whisper quiet
fan above and to the side of the heater to drive the hot air down to the cabin floor.
This is the only way you will ever warm
your tootsies that will 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.
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.
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.
It is arguable which type of fuel poses the greatest potential hazard. There are pros and cons to each type and your operating knowledge of your heater, along with proper maintenance, are key. 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. I consider the heater both a safety feature and a luxury in marginal, damp weather.
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, plus any other that are required due to unique requirements on your boat. This is your responsibility to figure this out and definitely NOT a time to make a short cut.
THERMAL PROTECTION for TABLE - A 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 duct tape (reflective aluminum) 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 at left is polished aluminum (light sand paper) and the wood bulkhead always stays stone cold. Maybe I am 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 right. 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 wish 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, 450 each. 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 costs. 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 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
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 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
trips to release a snagged line. Keep in mind that the system isn't perfect!
want to hear any swearing about this!
diesel/kerosene pressure tank is best nstalled in the port locker,
up off the floor so it stays dry and where the air pump is easy to
reach. This is also a relatively safe place to fill the tank since
fuel spills stay inside the locker where they can be wiped up and fumes
evaporate, staying outside the cabin. The fuel system operates at approximately 30 psi so all
lines and fittings must be in
DIESEL/KEROSENE BURNER MAINTENANCE
is a very convenient fuel to use but it is potentially dangerous on a boat
that it is heavier than air. If it accumulates in the bilge you have a
very dangerous situation. Oh joy, another bomb waiting for a spark to ignite it!
For this reason the best place to store a propane bottle is on deck
where fumes can vent overboard. If you want to hide (cosmetically) the bottle or
protect it from the heat of the sun then install it inside a propane storage locker that
is vented outside the hull AND SEALED from the cabin. Since propane
gas is heavier than air the tank
must be installed high and the drain vent MUST be installed low, at the
bottom of the locker. The drain vent MUST also remain open when the boat is heeled.
This is one of those cases where the tank cannot be stored
low in the hull to become
part of the ballast. You also have to decide which type of tank to use;
disposable or refillable steel/aluminum, which determines where and
how it can be stored and how it is to be vented. This decision is not to be taken lightly.
The propane tank, refillable or disposable, must always be clamped vertical inside the locker to achieve a gas feed from the top of the tank, unless you have a tank that is designed to be installed horizontally. The first device out of the tank valve should be a pressure gauge (connected to the valve) to allow you to easily and frequently leak test the gas distribution system for a leak. Immediately after the gauge, you should connect an electric solenoid valve for emergency shutoff controlled by a gas detector. Finally there is the supply line to the appliances. The supply line that is ported out through the propane locker wall, MUST go through a gas tight bulkhead fitting. Consider one of the following ideas for a locker:INSIDE LOCKER THAT VENTS OVERBOARD - A good place to install a propane storage locker on an SJ23 is inside the port locker just aft of the opening under the seat. Build a strong sealed box and mount it securely so it and the bottle stay put regardless of how much motion the hull goes through. The box MUST be 100% vapour sealed except for the purpose made vent holes. In addition, the forward facing door should be easy to operate so you can reach inside to operate the valve or replace the bottle. The box may be made from fibreglass, heavy duty vinyl or plywood that is saturated with epoxy to seal the wood. If you have to go through all the work of fabricating a box then you may as well make it big enough to house a 5 lb refillable bottle. Remember to leave some room above the bottle for a pressure gauge and a shutoff valve. The preferred method of venting this style of locker is from the bottom of the locker to the transom via a 1/2" ID hose. Install the drain vent fitting on the port side of the transom, away from the outboard engine, below the bottom of the locker and above the water line on all angles of heel. Install the inlet vent line from the top of the compartment to a fitting installed high up on the transom. It is OK to include an upward loop to prevent water from coming in. Now your propane storage compartment can vent heavier-than-air fumes over the side, which is the safest place. This is a very safe installation for an SJ23. You might also consider making the locker removable so you can crawl into the locker and go aft to inspect the nuts and bolts through the transom. This will require some creativity.
THAT VENTS INTO THE COCKPIT -
A variation on the locker described above is to vent into the cockpit. This method
uses the cockpit drains as the final path to vent
the heavier than air propane fumes overboard and is acceptable ONLY IF your cockpit drains
go through the transom and you anchor bow into the wind. HOWEVER,
the propane locker will also
become part of the cockpit water draining path. See Tech
Tip B17 for installing cockpit transom drains. In this configuration the bottom of the locker
must be about 1/2" above the cockpit sole. Drill
a 1" hole, about 1/2" above the cockpit floor, through the
cockpit wall into the propane locker. Cover the vent hole with a small stainless
steel clamshell vent. Fumes more than 1/2" deep inside the
can flow out the drain hole and down the cockpit drain. Thanks to
Thompson for this idea.
TANK MOUNTED ON THE PUSHPIT - Another common storage place is to clamp a 5 lb bottle to the stern rail or transom. This is not as elegant as a concealed storage compartment but definitely safe, serviceable and easy to install. A variation of this technique is to clamp the bottle upright at the aft end of the cockpit sole. This location is suitable ONLY if the cockpit drains through the transom.
TANK MOUNTED IN THE ANCHOR LOCKER - Another ingenious idea is to store the propane bottle in the bow anchor locker. This works ONLY IF the locker is totally sealed from the rest of the boat AND the locker has a drain hole to spill propane fumes overboard. You must ensure that the drain hole is NEVER plugged with mud or weeds. See Tech Tip B11. As an added benefit, you might be able to smell leaking propane fumes if the bow is upwind of you. Due to the humid conditions in the anchor locker, I suggest using an aluminum tank.
DISPOSABLE BOTTLES - If you decide to use a disposable propane bottle because you don't want the complexity of constructing a vented storage locker then consider one of the following solutions. You will run out of propane one day so carry a spare! If you carry disposable propane bottles they should be stored outside the hull in case one of them starts venting. I have no idea how a business is allowed to store boxes of bottles inside a retail store full of people.
PROPANE (LPG) SUPPLY LINE INSTALLATION - Having decided on a storage place for your propane bottle, you also have to take into consideration the supply line. Support and protect it along its full length and check it regularly for chafe and leaks. This being the case, it should be installed where it can easily be inspected. Consider one of the following safety tips:
OXYGEN CONTENT - The Force 10
propane heater consumes cabin air and is equipped with an oxygen
depletion device that shuts off the heater when the cabin oxygen
level falls below 95% of normal. Mine works very well.
If your internal
tank is not
vented outside the hull, please install vents
immediately. I prefer not to read about an SJ23 sailor in the
obituary column! Besides, it's too nice a boat to blow up!
HEATER MANUAL - Want to buy a manual for your Cozy Cabin
Heater? Please specify which fuel your heater uses, diesel/kerosene or
LPG/CNG, because the description in the manual matches the fuel. No
point in buying the wrong manual. I manage this
web site during my spare time and share the information freely. It takes a lot of work to measure, record and document the
information accurately. Such is also the case with these two manuals
that I reproduced. For this reason I charge $5.00 for a soft
copy that you can print.