Insulating the boat for cold

[Pembquist]

The boat gets a fair bit of condensation sitting in the water in winter. The little cubby holes at the salon births are pretty bad. I read about someone adding that bubble wrap stuff under the ash strips in the V birth. I am curious if anyone has done a thorough job of insulating a Cape Dory. I watched a video with Roger Taylor talking about his Ming Ming and he used glued on indoor outdoor carpet squares which sounded like a potential petri dish to me but what do I know. I was thinking of 1/2 or 3/4 extruded polystyrene glued to the hull at least above the waterline. My fear would be the flammability of it all and also if it would eventually just soak up watervapor and grow mold. Any body worked on this problem?

Also It feels like the void between the hull and the liner at places like the hanging locker could be filled with pour in or expanding foam, I am assuming there is a marine version of this, any downside to this?

[John Stone]

I insulated the Far Reach, from the waterline up. I used Arlaflex AP 1/2" foam for the overhead and under the side decks (I cut the fiberglass headliner out and replaced it with a removable one so the AP foam was a good choice there). But along the hull I basically built a sandwich sleeve of two pieces of reflectix bubble wrap and an insert of 1/4" blue board. Probably R6to R8. It has made a huge difference in both summer and winter. I have sailed in the winter with outside temps at 35F and had the inside temps at 70 with my refleks heater on the lowest setting. In the summer or down in the West Indies the boat stays noticeably cooler. All the panels are easily removable. Here is a link to how we did it.

http://www.farreachvoyages.com/hullinsulation.html

[Carl Thunberg]

Not knowing your individual circumstances, and how you use your boat in the water in winter, just consider the following. Keep in mind that my boat is a northern boat and we have harsh winters. I guess it boils down to how cold is cold. I've had just enough thermodynamics course-work to question the value of insulating a boat for your typical coastal cruiser (which John Stone is not).

Think of insulation as buying you some time to resist temperature changes. It only works when there is a significant temperature gradient from inside the boat to outside. Unless there is an internal heat source in winter, the temperature inside and outside the boat will be essentially in equilibrium, and insulation will not change that. Using your house as an example, no matter how well your house is insulated, if you lose power for an extended period of time your pipes will still freeze.

For the way John uses his boat, insulation is definitely worthwhile because he has an internal heat source in winter and is subject to wide temperature changes in summer. For most of us, insulation works better in summer than winter.

[John Stone]

Carl is exactly correct and I was remiss in not providing a better answer to the OP.

If you don't have an internal source of heat, or cooling, insulation provides less value. Without that internal source of heat in winter, or cooling in summer, the only advantage is it will slow the influence of outside temperature differentiation on the inside of the boat. Conversely, when the boat finally heats up, e.g. summertime, it can be slower to cool off especially if you are unable to ventilate the boat with a cool breeze or fans.

I will offer this though, it does not take much insulation to make a difference. I have found that in hot weather the boat stays comfortable for a lot longer. It does not take much internal heat to make the boat more comfortable in the winter. The Far Reach has been on the hard this winter in NC. We keep one of the oil filled electric radiator heaters running on cold days and nights. We can keep it on the lowest setting and no matter how cold it gets, it remains remarkably warm in the boat. There are lots of interesting heating techniques that can be quite effective without resorting to an expensive option like a deadicated propane, kerosene, or wood burning heater. I know folks that swear by heating inverted clay pots over the burners on their stoves (beware CO build up) combined with a modicum, of insulation.

In the West Indies last year, we were able to sleep longer and more comfortably because it took considerably longer for the boat to warm up in the early part of the day than it would have had the boat been uninsulated. And if there was a breeze, and we kept the air moving, it was never hot in the boat despite the warmth of the day.

[Pembquist]

Right now the only heat source is an oil filled radiator when it is at the dock. I would like to add some heat but there are a lot of cons, (hole in deck for stack, big expense for webasto, thought of a mr. buddy with refillable bottles but that seems like a lot of moisture dumped into the air,) but I would like to be more comfortable when I am tied up in the winter and with the electric heat on it does encourage mildew in the parts next to the hull above water. I can't really leave anything like paper or cloth in the cubbies in the seatbacks.

[John Stone]

Penbquist
Unless I missed it you have not mentioned what size boat you have or what your plans are or what exactly your heater needs to accomplish and under what conditions. A wabastco is not a particularly simple inexpensive solution. There are simpler less expensive but fully vented heaters available that might meet your needs and take up a lot less space. The hole in the deck is not an issue if you do it right, especially when you come to grips with the fact that there are already hundreds of bolt holes in the deck of your boat.

An electric oil filled heater is a great solution for dock side operations and even a modicum of insulation will have a significant positive effect on your heating efficiency. We also run a box fan year round which has nearly eliminated any sings of mildew.

You might also check some of the back issues of Practical Sailor as they have written numerous article about combatting mildew.

Good luck.

[Steve Laume]

I added the reflective bubble wrap insulation behind all the ash ceilings on Raven. I also put it in the hanging locker and made up the ash strips to cover it there as well. IT has definitely made a difference.

A few things to consider when you do are that you might want to clean up and varnish all the strips when you have them off. Make sure to use a sharpie marker with some sort of labeling system on the back of each strip. Toss out all the original screws and by new Phillips headed ones. You will thank me for this. When I first did the V berth you could see bits of the foil between the cracks. to eliminate this in the main saloon I covered the foil with black landscape fabric and it looks much better.

One of the worst offenders are all those holes used to get to the stowage area behind the seat backs. CD kind of cheaped out there by not making doors for them. I thought the whole seat back thing was kind of a bad design, so I got rid of them and made doors for the stowage areas that match all the rest on the boat. It makes a huge difference when you are sleeping, not to have cold air pouring in on you and things stay in there when the boat is getting tossed around. By closing up those spaces, you are also reducing the heated area. This is the same reason that I keep the head door closed when I am staying aboard in cold weather. I really don't need to warm the head and V berth areas.

Even though the insulation will not make the boat warmer without a heat source, it takes surprisingly little to increase the temperature. The biggest advantage is that it slows the heat swings and eliminates some of the very sharp temp differentials. This is where you tend to get condensation. Go outside on any frigid day and then come back in with glasses on and you can easily see the problem. If you were to very slowly increase the temp the way it works as the cold passes through your insulation, you don't get condensation.

As for the benefits in the summer, it will keep the boat much cooler. You will not get nearly as much heat conducting through the hull and it is mass not insulation that holds heat when things cool down outside. If you haven't heated that mass up as much throughout the day then things will cool down quicker because you have stored less heat.

I have a wind scoop for the forward hatch that works great when there is any kind of a breeze. I also installed a blower that is attached to one of the engine cowls. I can run it anytime the engine is producing heat to help keep it from entering the cabin. I usually only run it for a while at the end of the day because the noise sounds too much like a vacuum cleaner, Steve.

[Tom Keevil]

It sounds like you are happy with the oil filled heater for temperature, but unhappy about the moisture and mold. What you need is a dehumidifier. Leave that running when you leave the boat, and your mold problems will become minor. It will also be a whole lot easier than installing insulation.

We sail in the often cold and wet Pacific Northwest and Alaska. We carry our dehumidifier with us, and even after a week or two at anchorages, a day plugged in at a dock wrings most of the water out of cabin. No matter what the weather, we never leave the boat for any length of time without the dehumidifier running. It doesn't run continuously, just when the humidity rises. Also, run a small fan to keep the air moving to discourage mold.

[tjr818]

Tom,
What type of dehumidifier do you use?

[Tom Keevil]

Tim,
We first used one from Sears, which was really too large to carry around with us, so we would leave it in the car when we left the dock. After quite a few years that model was recalled as a potential fire hazard, and we left for Alaska without it. We bought a new one at the hardware store in Petersburg, AK. We bought a smaller one that can be stored under our V-berth insert. I think it is mabe a 30-pint size, but I don't offhand know the make or model. We chose the make by the fact that the hardware store carried this one brand. The motto of most SE Alaskan hardware stores is "If we don't have it, you don't need it." Since there are no roads connecting any of these towns, you thankfully buy what they have. We used the same approach in choosing a replacement head.

When leaving the boat for a long time, we change the drain so it goes out a hose, rather than into the integral bucket. We have drained into either our holding tank or the galley sink, depending upon how long we'll be gone, and how comfortable we are leaving a seacock open.

I'll be down at the boat in a day or so, and can get the detailed particulars if you like.