Riding out a storm, sealed up tight down below. Watch out for CO2.

[GordMay]

CO2at very high concentrations (e.g. greater than 5000 ppm) can pose a health risk.
Refer to Appendix D, Summary of Selected Air Quality Guidelines in ASHRAE Standard 62.1-2016, "Ventilation for Acceptable Indoor Air Quality".

[Don C L]

Hence my thought that unless your boat is expecting to spend considerable time upside down, my own preference would be to keep the dorades open.

[hamburking]

A man and woman were found dead on a sailboat near Kingston, Ontario, Canada about a month ago. They appeared to have been living on the boat over the winter, and were using some sort of fuel based heater with the boat all sealed up.

https://globalnews.ca/news/5199208/k...deceased-boat/

[Cpt Pat]

Originally Posted by GordMay

At the activity levels found in typical office buildings, steady-state CO2 concentrations of about 700 ppm above outdoor air levels indicate an outdoor air ventilation rate of about 7.5 L/s/person (15 cfm/person). Laboratory and field studies have shown that this rate of ventilation will dilute odors from human bioeffluents to levels that will satisfy a substantial majority (about 80%) of unadapted persons (visitors) in a space. CO2 concentrations in outdoor air typically range from 300 to 500 ppm.
Thus indoor CO2 concentrations of 1000 to 1200 ppm, in spaces housing sedentary people, is an indicator that a substantial majority of visitors entering the space will be satisfied with respect to human bioeffluents (body odor/farts).
Note however that CO2concentration is not a good indicator of the concentration and occupant acceptance of other indoor contaminants, such as volatile organic compounds off-gassing from furnishings and building materials. Thus CO2concentration is not a reliable indicator of overall building air quality.

I can tolerate farts. It's becoming stupid from CO2 that concerns me.

I have an issue with one sentence from above: "CO2 concentrations in outdoor air typically range from 300 to 500 ppm." There is nowhere on earth that has a CO2 concentration below 400 PPM - unless the air has been processed and scrubbed to remove CO2.

That quote above must have been written in the Good Old Days when ambient CO2 was much lower. Ambient CO2 hasn't been 300 PPM since before the 1960s.


(http://scrippsco2.ucsd.edu/data/atmo...mlo_co2_record)

[Cpt Pat]

Originally Posted by Don C L

Hence my thought that unless your boat is expecting to spend considerable time upside down, my own preference would be to keep the dorades open.

You make a good point.

[MartinR]

Originally Posted by Franziska

For a practical approach, see what Sven Lundin did on his micro cruisers for this.

Very small volume, two people on board. Very seaworthy despite the size. Surely he has a clever solution.
Just Google him.

He is ducting the air from his dorado ventilators down to cabin sole level. When the boat goes inverted, the outlet will be high above the water.

Unfortunately, this is not a solution easily implemented unless the boat is designed for it from the beginning.

[john61ct]

Originally Posted by hamburking

A man and woman were found dead on a sailboat near Kingston, Ontario, Canada about a month ago. They appeared to have been living on the boat over the winter, and were using some sort of fuel based heater with the boat all sealed up.



https://globalnews.ca/news/5199208/k...deceased-boat/

That's CO, carbon monoxide, lost a friend to that myself.

But not the topic here.

[MartinR]

Originally Posted by Don C L

Hey, for a second I thought someone had stolen my idea! They may be ok, but they won't seal up when inverted, in fact the opposite.

They write that the vents seal when inverted, due to water flow. There is a video of an inversion test on their site.

[MartinR]

Originally Posted by Franziska

Very seaworthy despite the size. .

If you have a very narrow definition of seaworthiness, his boats are seaworthy. The same way a barrel is. His boats survive rolling, but they are also very susceptible to being rolled.

They have almost no windward ability and you would never be able to claw off a lee shore for example.

Sorry for the thread drift.

[Dockhead]

Originally Posted by Cpt Pat

Great idea... as long as you don't think about it. The balls will float in the open position if the boat is inverted or heeled past 90 degrees - gravity being what it is.

This is a really old issue with dorade vents. The problem is described well in: "Desirable and Undesirable Characteristics of Offshore Yachts," page 108, published in 1987.

Here's a science experiment: Take an empty water bottle with its cap removed, and plunge it inverted into water, cap end down. Very little water enters. This simulates a well-sealed boat that is perfectly inverted (in the real world, one hopes the boat doesn't stay in that popsition). Now, while keeping the cap end immersed, rotate the bottle 90 degrees so it sits sideways in the water (simulating a knockdown or entry/recovery from being inverted). What does the water do now?

That's the problem with dorde vents. The 32-year-old book sited above recommends having a threaded cap to seal dorades from below. In my case, all we had was a towel to stuff in the opening from below, which is better than nothing.

Dordes are great at keeping spray out, and even water out from boarding seas. They are not great at keeping water out when immersed on a boat heeled past 90 degrees. The whole air/water separation scheme depends on a normal orientation of gravity, i.e., the boat being right-side-up.

In my opinion, from a storm survival standpoint, and ordinary cowl vent is safer, provided the cowl can be removed and replaced with a tight fitting cap. Of course, it's far safer yet to not find yourself in a storm in the first place.

Is that really something anyone worries about? I can't see why that is any big concern. If you get rolled, you'll have much bigger problems than a little water getting into the boat through your dorades, during the brief time when the boat is inverted.



When the boat is at a 90 degree heel angle, the dorades will be high above the waterline, unless the hull is half full of water (in which case again -- you've got much bigger problems).


By the time the dorades hit the water, the boat will be most of the way to being inverted. No monohull which has not lost its keel (in which case, again, you've got much bigger problems) will stay in that posture for more than a few seconds.


I think this is a total non-issue, and I do not indeed close my dorades in storm conditions, and do not intend to. I did get knocked down 90 degrees in the North Sea once, and no water came in through the dorades (another story concerning the stupidly open companionway scuttle )


And so to the OP's question -- in a storm with the wind shrieking in the rigging, and blowing through the cabin via the dorades, CO2 is the last thing I worry about.

[GordMay]

Originally Posted by Cpt Pat

... I have an issue with one sentence from above: "CO2 concentrations in outdoor air typically range from 300 to 500 ppm." There is nowhere on earth that has a CO2 concentration below 400 PPM - unless the air has been processed and scrubbed to remove CO2.
That quote above must have been written in the Good Old Days when ambient CO2 was much lower. Ambient CO2 hasn't been 300 PPM since before the 1960s.
(Primary Mauna Loa CO2 Record | Scripps CO2 Program)
...

Interesting observation.

The information (300 to 500 ppm) was quoted from ASHRAE (undated) Technical “Frequently Asked Question” Document ID 35, which references ASHRAE Standard 62.1-2016, which suggests a publication date of later than 2016.
➥ https://www.ashrae.org/File%20Librar....03-FAQ-35.pdf

AIRS (Atmospheric Infrared Sounder on the NASA Aqua spacecraft) has shown that carbon dioxide is not evenly distributed over the globe*; it is patchy with high concentrations in some places and lower concentrations in others. The gas’s transport and distribution through the atmosphere is controlled by the jet stream, by large weather systems, and by other large-scale atmospheric circulations. The findings from AIRS have raised new questions about how carbon dioxide is transported from one place to another—both horizontally and vertically—through the atmosphere.
➥ https://earthobservatory.nasa.gov/im...carbon-dioxide


* Perhaps this explains the counter intuitive range (300 - 500 ppm).

[MartinR]

Originally Posted by Dockhead

I I think this is a total non-issue, and I do not indeed close my dorades in storm conditions, and do not intend to. I did get knocked down 90 degrees in the North Sea once, and no water came in through the dorades (another story concerning the stupidly open companionway scuttle )


And so to the OP's question -- in a storm with the wind shrieking in the rigging, and blowing through the cabin via the dorades, CO2 is the last thing I worry about.

I think it is an issue, unfortunately. Modern wide boats with little superstructure have far too good inverse stability. I would think they can stay inverted for minutes, not seconds, if you are unlucky, depending on wave action. Maybe this would be mitigated by water flowing in, creating free surface effects, but who knows.

I just compromise and leave some vents open, some I close.

I also do not think that CO2 or O2 is really a problem in heavy weather for normal yachts. They are not that tight.

[Dockhead]

Originally Posted by MartinR

I think it is an issue, unfortunately. Modern wide boats with little superstructure have far too good inverse stability. I would think they can stay inverted for minutes, not seconds, if you are unlucky, depending on wave action. Maybe this would be mitigated by water flowing in, creating free surface effects, but who knows.

I just compromise and leave some vents open, some I close.

I also do not think that CO2 or O2 is really a problem in heavy weather for normal yachts. They are not that tight.

OK, well, how many of us have "wedgie" boats and how many of those who do, take them out in storm conditions?


But even on those -- you will not have a problem with water getting in, when the boat is entirely inverted -- water can't come in, when there's no place for the displaced air to go. Water will come in only when the boat is on her side AND is low enough in the water so that some dorades are underwater and and others are not. I just don't think this is really possible, even on a wedgie, unless the boat is already half full of water.



And even a boat with a lot of inverted stability, which might stay fully inverted for a while, will not indeed stay at 90 degrees for more than a few seconds at most, unless she's missing her keel.


I'm not a boat designer, but I would bet dollars to doughnuts that the designers calculate the waterline when the boat is at 90 degrees heel and make sure that no dorades are underwater in that posture. My boat is certainly like that -- the dorades are all well inboard and it's simply impossible to imagine their being in a posture to let any significant amount of water into the boat.


Much more likely to cause problems are cockpit lockers (on aft cockpit boats) and lazarettes without water-tight lids. Real blue water boats have watertight lids on the lazarettes which can be dogged down tight, and the edges of the laz hatch well inboard; mine is like this. Center cockpit boats don't have cockpit lockers.

[GordMay]

Top 5 Sinking Ship Footage
A compilation of the best clips of sinking ships, caught on camera.
# 5: Is a military/coast guard, filmed sink from a nearby vessel.
# 4: Is a bulk carrier who sinks during cargo operation.
# 3: Is the American destroyer UUS Radford, that was intentionally sunk to make a artificial reef.
# 2: Is a tourist catamaran boat, that capsizes and sink off the Costa Rica coast. The whole accident was filmed by a passangers gopro.
# 1: Is the cruise ship Oceanos, that sank in 1991. A rescue helicopter filmed when the ocean liner went down.

https://www.youtube.com/watch?v=ZE3J9yLYu_Q

15 tips to prevent your boat sinking
➥ https://www.boatsales.com.au/editori...sinking-56379/

[Dockhead]

Originally Posted by GordMay

. . .

15 tips to prevent your boat sinking
➥ https://www.boatsales.com.au/editori...sinking-56379/

Note dorades are not on the list.