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Old 04-06-2018, 12:07   #16
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Re: How important are opening portholes?

When you are aboard, but not under sail/power: If it is warm it is very important. Hot, hugely important, although it may not seem to help. Cool, it depends on you. Cold, not so much. Underway, important to be sure they are closed. Numerous variations exist, depending upon humidity (up to and including rain), the boat, and personal preference.

Not aboard: While there can be specific reasons for exceptions (particularly specific, individual opening ports) the general rule is closed.

All sort of like a land based house.
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Old 04-06-2018, 12:40   #17
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Re: How important are opening portholes?

Wolf:

As another Vancouverite and Salish Sea cruiser my take is this: Whether you have opening portholes is rather trivial but for the fact that opening portholes are leak-prone. That you have VENTILATION is very important . Ventilation is best achieved by leaving your hatches open when you can.

For times when you cannot leave your hatches open, e.g. when you are absent from the boat, when it is pouring down rain while while you are in port or anchored, or when under way in inclement weather, "through deck" ventilation as furnished for example by "Dorade" vents (named after "Dorade", the vessel that first employed them) is a far better choice than opening portholes. Dorade vents can be assisted by fans.

The trick is to keep air within the boat circulating AND at THE SAME TEMPERATURE as the air without. The reason is that the HUMIDITY of the air within the boat will then not be sufficient to condense on the insides of the hull and on the furnishings and thereby conduce to mildew.

The "proper" way to stay comfortable in a boat is therefore to put on your long skivvies and an extra sweater when required, rather than to heat the boat. In the Salish Sea doing so is perfectly feasible, for there are very few days and nights in the year when appropriate clothing and a decent sleeping bag is not sufficient to ensure comfort.

Bunks should be ventilated without being draughty and the galley should be ventilated because those two locations are the ones that generate potentially injurious excess humidity within the boat. Just how you arrange for such ventilation will vary from boat to boat.

In TrentePieds we manage nicely by keeping the hatches partially open most of the time,

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Old 04-06-2018, 16:51   #18
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Re: How important are opening portholes?

On my flush decked boat there are ten opening port holes along the hull. The ones that see greatest use are close to the bow where the hull slopes outward. This slope means that these ports can be left open in most conditions as rain does not ingress unless it's a storm. The other portholes are a PITA. One decided to leak when we were heeling and rocketing along with waves reaching it. They are expensive and require regular seal replacement. Wish I had installed dorade vents even if they make great deck obstacles.
Being in the tropics, ventilation is essential and we do this via deck hatches which are covered by a dinghy. The covered deck ventilation means we don't need a dehumidifier when absent. Moist air, like warm air, is less dense than dry cool air, so it rises. In the loo and shower room, ventilation is more considered.
An important feature not mentioned and probably not strongly relevant is the presence of large vista windows around cabin sides. In the tropics, these can quickly turn your boat into a greenhouse. Beware.
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Old 04-06-2018, 23:54   #19
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Re: How important are opening portholes?

Ventilation is critical in a boat. The more options to ventilate the better.
Opening port holes give you options. Fixed ones don't
I have a full dodger so cockpit / salon hatch is usually open. Especially nice when warm air from the cabin comes up on a cold night watch.

I have 3 deck hatches to pick from for ventilation.

I have a ceiling fan vent in the galley and one in the head that I can turn on when needed.
I have three oscillating fans in the boat to circulate air, one forward cabin, one amidships and one in the aft cabin, used as needed.

I have two fixed windows on the stern that I wish opening was an option.

I have 8 opening portholes on ea side of my boat...16 total. All of them get opened and closed as needed.


My hull is insulated, and I have a diesel heater in the salon that can also push hot air to the aft cabin.
I can keep the living space comfy most all the time.


I cant recall my bronze potholes ever sweating.



Mold can live in a wide range of temperatures but cannot live below 50% humidity.


That is one mans experience and opinion.
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Old 05-06-2018, 02:31   #20
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Re: How important are opening portholes?

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Ventilation is critical in a boat. The more options to ventilate the better.. . .
Amen! I've never been on a sailboat which had what I thought was adequate ventilation.

As Stu said, having a decently long overhanging spray hood (dodger) over the companionway is a must -- otherwise you can't even keep that open in the rain.

Dorade vents are extremely important -- and they have to be LARGE in order to do anything.

Exhaust ventilation in the galley is very useful -- otherwise you almost can't cook in hot weather.

My boat has all of that, but ventilation is still woefully inadequate, and my boat is not comfortable in hot weather. I have a raised salon with relatively large windows in the deck house, so there is a lot of solar gain. But NONE of the deck house windows opens , nor the two hull ports. I have two smallish hatches and two tiny ports into the cockpit. What you really need here is opening deck house windows, especially the forward-facing ones -- at anchor, air will pour in through that one. Oysters are well arranged in this regard.

In the forward cabins and heads, there are no ports whatsoever -- just hatches.

Aft, I have narrow opening deck house ports everywhere, but because the sides of the deck house slope inward, rain pours in if you leave these even cracked. I have hull ports, but they don't open.

Big dorades (I have 6 of them) help a lot, but by themselves are not enough. Incidentally, dorade vents are much more effective if you aim them.

You are right to ask this question, and I would certainly pay a lot of attention to this question if I were you.
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Old 05-06-2018, 02:56   #21
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Re: How important are opening portholes?

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For me on the Texas coast, a small Eva-dry Dehumidifier works great for keeping the humidity down.

So for controlling moisture and mildew you prefer the dehumidifier with the Boat tightly closed without ventilation? Has it been effective?
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Old 05-06-2018, 04:56   #22
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Re: How important are opening portholes?

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Amen! I've never been on a sailboat which had what I thought was adequate ventilation.

As Stu said, having a decently long overhanging spray hood (dodger) over the companionway is a must -- otherwise you can't even keep that open in the rain.

Dorade vents are extremely important -- and they have to be LARGE in order to do anything.

Exhaust ventilation in the galley is very useful -- otherwise you almost can't cook in hot weather.

My boat has all of that, but ventilation is still woefully inadequate, and my boat is not comfortable in hot weather. I have a raised salon with relatively large windows in the deck house, so there is a lot of solar gain. But NONE of the deck house windows opens , nor the two hull ports. I have two smallish hatches and two tiny ports into the cockpit. What you really need here is opening deck house windows, especially the forward-facing ones -- at anchor, air will pour in through that one. Oysters are well arranged in this regard.

In the forward cabins and heads, there are no ports whatsoever -- just hatches.

Aft, I have narrow opening deck house ports everywhere, but because the sides of the deck house slope inward, rain pours in if you leave these even cracked. I have hull ports, but they don't open.

Big dorades (I have 6 of them) help a lot, but by themselves are not enough. Incidentally, dorade vents are much more effective if you aim them.

You are right to ask this question, and I would certainly pay a lot of attention to this question if I were you.
Our 53 is for sale, please let me know if you’re interested in better ventilation and see-through sun shades. The Air conditioning system also gets nice and cool.
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Old 05-06-2018, 06:53   #23
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Re: How important are opening portholes?

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Our 53 is for sale, please let me know if you’re interested in better ventilation and see-through sun shades. The Air conditioning system also gets nice and cool.
Ha, ha, thanks, but I'm done with production boats. Next boat will be custom!
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Old 05-06-2018, 06:59   #24
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Re: How important are opening portholes?

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The answer is, like almost everything boating, "It Depends"

If you spend much of your time at anchor with the boat weathercocked into the wind, then opening ports on the sides of the cabin do very little, and the overhead hatches do all of your air exchange.

In a marina, where the wind can come from random directions relative to the boat, the side ports are more important.

There are very well ventilated boats with few opening side ports, and very poorly ventilated ones with many opening side ports. Ventilation is a dynamic process, and it can take time to figure out what works on individual boats.
Agree 100%.

We spend quite a bit of time in marinas and that is the only time we open our ports.

That being said our yacht was built by the greatest yacht manufacturer there ever was or ever will be. Thank you Hallberg Rassy
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Old 05-06-2018, 07:50   #25
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Re: How important are opening portholes?

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Ha, ha, thanks, but I'm done with production boats. Next boat will be custom!
Ahmen brother! My last boat (center console) was a custom build - just the way I wanted it - reinforcements where wanted - holds sized properly for dive gear, a well for oversized anchors, perfectly sized engine for my family's needs, etc. Gives you a lot of pride and pleasure.

I've found that you can build brand new and custom for the same price as a production boat - only having to give up a bit on all the little yuppy details that might make it more of a yacht but certainly no more of a "boat."

The only thing to be careful of with custom is not to make it to so esoteric that it ruins marketability (resale value).
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Old 05-06-2018, 08:04   #26
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Re: How important are opening portholes?

How important are condensation and mold? Either you keep the vessel dehumidified with AC or a dehumidifier, or you rely upon ventilation with moist air that at least circulates.
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Old 05-06-2018, 08:35   #27
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Re: How important are opening portholes?

When it's hot a boat feels airtight, when cold it feels draftier than a Scottish castle. More often hot here and it's usual to sail with leeward cabin portlights and cabin top hatch open.
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Old 05-06-2018, 08:36   #28
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Re: How important are opening portholes?

I dont find them important at all. But you do need some ventilation. Portlites are ineffective at best at ventilating the boat. Boats swing bow to wind, portlites are on the side. Little air comes in.
Portlites leak, they drip into the boat most often even if the angled type. You need hatches that open toward the wind to scoop in air.
Most my opening portlites spent their life unopened. Also buy a windscoop etc for your hatches. One of those will be like a hurricane thru your boat!
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Old 05-06-2018, 08:40   #29
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Re: How important are opening portholes?

I put in a couple of solar powered vents and that pretty much solved my condensation problems. The boat smells better inside after it's been closed up as well.
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Old 05-06-2018, 10:33   #30
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Re: How important are opening portholes?

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I dont find them important at all. But you do need some ventilation. Portlites are ineffective at best at ventilating the boat. Boats swing bow to wind, portlites are on the side. Little air comes in.
Portlites leak, they drip into the boat most often even if the angled type. You need hatches that open toward the wind to scoop in air.
Most my opening portlites spent their life unopened. Also buy a windscoop etc for your hatches. One of those will be like a hurricane thru your boat!


Well I disagree. When you are on a swing mooring the port lights are much more efficient as the boat swings and air moves in and out on the other side.

Have a 44 foot boat with 3 large deck hatches. Two are facing fwd. If I open the port lights it is a big improvement.
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