Using Dry Ice

[Mick Young]

My partner and I intend this new years break to drag the boat the 1000km (800 miles) both to and from Melbourne to Sydney. The plan is to get there the day before News Eve and leave 5 days later, cruise around the harbour, watch the spectacular fireworks and generally have fun. Over the 4 days of our melbourne cup weekend we just used normal Ice and it got through, though it was rather cool. I was wondering if anybody used dry ice for the esky/ice box? I know about the hazards of touching it and it freezing anything it touches but other than that any sugestions?

Keep it black side down

Mick

[hellosailor]

Mick-
Assuming you used block ice and not cubed ice, since block ice lasts much longer. With dry ice normally it comes in layers of brown paper or envelopes made of layers of brown paper, and if you leave it that way it is safe to handle the envelopes. The cold gas diffuses out through them.
Haven't tried it in a boat box but did stick some leftover dry ice in the refridge freezer section at home once, and the compressor didn't run for three days.
But some of us have some concern about using it on a boat since it will be turning into CO2 (not CO) and that will be displacing air in the boat. I'd be somewhat concerned about ventilation, especially if there's a drain from the ice box that the cold gas can creep out through.
With adequate ventilation it should be good, and I've heard of folks using it. I just have no idea of how to *ensure* adequate ventilation. From what I've been told, CO2 poisoning won't kill you in your sleep like CO does, it is supposed to wake you up with headaches and shortness of breath, or something similarly uncomfortable but giving you a chance to get out.
With this being your summer and assuming you'll have the boat opened up and vented...probably safe enough for you.

[Cruisingdad]

We have used it before on long runs. It works well. We wrap it in several layers of newpaper then tear small holes in them to regulate the temperature. Our use is more to keep the fridge from running and minimize power consumption that to "keep things reall cold" though. I will tell you that if you just drop it in there without any wrapping, you will probably freeze everything solid! So, it works. Also, you have SOOOOO much wind blowing offshore I would not be concerned too much about any kind of gas buildup - unless you are eating freeze dried food or handing out beans for rations.

- CD

[chris_gee]

Well we know you are short of water there mate. How well dry ice would last depends on the size, how good the insulation is, the outside temperature and how full the box is with frozen goods - not beer obviously. A freezer needs to be -18c (0 f) while a fridge is 3c (40 f).
Dry ice is at -78.5 c. It will melt in a freezer quite quickly. Assuming you bought the frozen things and ice on arrival for seven days you would need about a 100lb of dry ice taking up just over a cubic foot. Although dry ice is colder than real ice it is a much less effective coolant because most of the cooling effect comes from not it's temperature but the heat absorbed to melt, which is less than that for ice.
It is also poisonous at over 5% in air so you would need to watch the ventilation.
It would work but would not be a great advantage. There is also the problem of buying it, but I guess that goes for ice too. I guess if you have to import bottled water you could freeze the bottles and that would solve two problems at once.

[Bill Mc]

CO2 gas is 1.5 times as heavy as air, thus if released to the air it will concentrate at low elevations. The Bilge. Air containing more than 10% CO2, if breathed, can be life-threatening. Exhaled air contains as much as 4% carbon dioxide. CO2 on a boat could be a silent killer without the proper monitoring and safeguards.

[sailingdog]

I'd have to second Bill's warning about CO2 being dangerous in high concentrations, and due to it being heavier than air, can actually end up concentrating inside the cabin of a boat. If your boat has fairly good through ventilation, it shouldn't pose much of a danger, but it is something to consider, and a CO detector probably won't detect high levels of CO2.

Keeping the icebox as full as possible will help stabilize the temperature and help keep the contents cooler. CD and Hellosailor seem to have covered its use fairly well though...

[Culinary411]

I've used dry ice quite a bit. What I do is put down a layer of regular ice, then set dry ice on top (wrapped in 1 layer of thin newspaper) and then another layer of regular ice. The dry ice keeps the regular ice from melting. Works like a charm. Works like a charm. As far as CO2 build up, I've never had a problem. I've kept the companionway open most of the time and ventilation was good.



-Nick

[Goodnewsboy]

I hate to be the bearer of bad news.

CO2 smothers fire by displacing oxygen. It is, as has been said, much heavier than air and likes to collect in closed-bottom containers like a boat hull. It isn't toxic like CO, but it asphyxiates its victims. It will kill you in your sleep just as efficiently as CO. Read the warnings on CO2 fire extinguishing systems ashore. There is a reason why marine fire extinguishing systems rarely use it. If you can't be certain that your ventilation is good enough to get it out of the boat, I'd think twice.

[paulk]

We used dry ice in our icebox for a tranatlantic trip and found it quite helpful keeping things frozen longer. CO2 emissions were a concern, however, and we kept hatches open as much as possible. We did not use a lot (perhaps about 50 pounds total) figuring if it simply helped keep stuff in the box cool for just an extra week, that would be enough.

[Mick Young]

I figure on only buying around 5lbs of the stuff, so I dont think the gasses will be to much of a problem? The hatches will be open during the day a we sail around Sydeny harbour and if you think that it wil be a problem overnight then I can stick the esky into the cockpit when we turn in. The thing using both normal ice and dry ice seems like a great idea. Our meals will frozen when we go away so that we will just have to find an anchorage and reheat precooked tucker to save time and that gives us more time sailing around.

Keep it black side down

Mick