Air Cowls

[backcreeksailor]

On most older sailboats you see the classic poor man's air conditioning air cowl snorkels on either side of the mast and sometimes on the bow for cabin ventilation. And then again on the transom to vent any fumes that might be present in the engine compartment.

I know there are the solar powered fans/vents that can be used in place of the cowls. But I don't see those on new boats either. So how do most modern boats (those that don't come with marine air conditioners), keep the cabin and engine compartments ventilated?

[backcreeksailor]

Was this a dopey question...?

I'm asking because the boat I'm about to acquire has 2 cowls by the mast that seem like they're just going to be tripping hazards and 2 on the transom. So I'm thinking about capping off the one's by the mast, adding a forward hatch solar vent set to draw air in. And then capping off one of the transom vents and installing a solar vent in the other set to draw air out.

The idea being to create a draft of air through the entire boat to reduce the heat and humidity throughout the entire cabin.

But I was just wondering if newer boat designs have come up with a better (possibly more concealed) way to keep things ventilated below deck?

[capttb]

Usually the 2 on the transom vent the engine compartment, one with a blower that exhausts and hopefully the other will act as an intake. They are usually connected to the engine compartment by 3 or 4 inch flexible ducting like a clothes dryer vent. The idea is to create a slight negative pressure in the engine compartment so diesel and other "fumes" from an operating engine do not enter the "living areas" of the boat. One drop of diesel stinks to high heaven in a confined space and if you've ever had some on your hands you know it seems impossible to wash off.
Newer boats rely on larger and more numerous opening ports to ventilate while occupied but don't seem to address an unoccupied, closed boat.
When its hot and still boats feel airtight, when cold and windy they feel like their made from screen doors.

[Faster]

If the "cowls" are protected by proper dorade boxes (esp the ones forward) so that water can't get directly below then they will be very useful in providing ventilation - the draft from the upwind facing cowl can be considerable.

Agree that the ones aft are for engine space ventilation.

But if there's no water trap, consider installing blanks when at sea, and reinstalling the cowls in harbour.

[mgmhead]

backcreek,

My experience is the cowl vents on the cabin roof are not truly tripping hazards. Sure anything can cause a trip but I've not tripped on mine. Don't know about yours but mine are vinyl and simply "stick" in place, so I guess you could kick one without anything worse than knocking it out of place. I find the ventilation they provide most beneficial, especially at anchor. Also useful at anchor is a "breeze booster" or similar device that channels the breeze into the forward hatch. If you're going to anchor out I highly recommend such a device. There are a couple of types on the market and I have not interest in any of them so choose the one that best suits your needs. I simply prefer the breeze booster style as it is self supporting.

All the best...MGM

[backcreeksailor]

Keeping in mind that this will be a mostly Chesapeake Bay application, not out on blue water with presumably more constant heavy air... Would you say that a 3"x4" cowl or a 1000 cu ft per hour solar powered vent will pull more air into the cabin?

The one in-going, one out-going solar vent set up would create the "negative pressure" you mentioned in the engine compartment. So is there any reason why the setup I described would be a bad idea?

Oh... and I'm thinking of this more in terms of underway than anchored. But yes, the breezebooster on the forward hatch definitely looks like it would be the way to go at anchor.