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Old 19-12-2012, 04:23   #31
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Re: Ventilation in Aft Cabins/Center Cockpit

Stern anchor. Not only does it improve the ventilation in all ways, but it also makes it very easy to haul in the anchor while next to the tiller and then sail off the anchor by simply unfurling the jib. No engine needed.
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Old 19-12-2012, 06:44   #32
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Re: Ventilation in Aft Cabins/Center Cockpit

On my center cockpit I put a breeze booster facing forward over a forward hatch and a second breeze booster facing aft over the big hatch in the aft cabin. Leave the doors open and ventilation is great.
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Old 19-12-2012, 06:51   #33
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Smile Re: Ventilation in Aft Cabins/Center Cockpit

Doodles,
Thanks for dropping in! I know the boat but have never had an opportunity to meet Steve. It would indeed be a good thing to talk to him since one of the models that I like is a Gulfstar.
When Barbara and I get ready to move aboard, we'll be looking at quite a few models and I have a rather long list started. I am aware of the pro's and con's of center vs aft cockpits and started this thread to get some feedback of people who have lived aboard a center cockpit and what creative ways or solutions they have invented to deal with the ventilation problems in the tropics. Of course, I may wind up staying with a moderate length and keep my beloved Tartan and save a pile of $$$

Cheers,
Tom
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Old 19-12-2012, 07:01   #34
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Re: Ventilation in Aft Cabins/Center Cockpit

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Originally Posted by Auspicious View Post
On my center cockpit I put a breeze booster facing forward over a forward hatch and a second breeze booster facing aft over the big hatch in the aft cabin. Leave the doors open and ventilation is great.

Auspicious,
Have you tried the Breeze Booster for the portlights? I would think that this would be a great thing for an aft cabin.
Port Ventilator - Breezebooster

Tom
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Old 19-12-2012, 16:39   #35
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Re: Ventilation in Aft Cabins/Center Cockpit

G'day, Mate. The large opening hatch along with 2 opening side ports, well above the water line, provides plenty of fresh air in our center cockpit Mason 53. There are no wave slap issues with the hull design. Holiday Cheers.
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Old 23-12-2012, 10:38   #36
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Re: Ventilation in Aft Cabins/Center Cockpit

It seems to me the biggest problem is getting the warm/hot air out, then the cooler air will naturally flow in from which ever source.

Has anyone tried a chimney stack? Any tall pipe mounted over a dorado would create a chiminey effect and there by create a low pressure in the cabin and allowing cooler air to flow in. If you were to mount some type of venturie system on top of the pipe, it would work even better.

A 4" PVC pipe six foot long should surfice
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Old 24-12-2012, 07:42   #37
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Re: Ventilation in Aft Cabins/Center Cockpit

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It seems to me the biggest problem is getting the warm/hot air out, then the cooler air will naturally flow in from which ever source.

Has anyone tried a chimney stack? Any tall pipe mounted over a dorado would create a chiminey effect and there by create a low pressure in the cabin and allowing cooler air to flow in. If you were to mount some type of venturie system on top of the pipe, it would work even better.

A 4" PVC pipe six foot long should surfice
I repeat; you cannot exhaust air through a dorade box. There is no direct connection between the funnel and the through deck fitting and the dorade box itself has holes to allow any water that enters through the funnel to get out, not go into the cabin.
You cannot exhaust air through a dorade box, period.
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Old 24-12-2012, 08:08   #38
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Re: Ventilation in Aft Cabins/Center Cockpit

It would be quite simple to modify a dorado or mushroom vent or even a hatch to fit a pipe on top and remove the water trap while you are at anchor.
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Old 24-12-2012, 08:14   #39
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Re: Ventilation in Aft Cabins/Center Cockpit

We're on a "walk-over" without air flow from forward cabins although we do have opening transom ports for exhausting air. Our best improvement in air flow for the aft cabin comes with having a wind scoop that extends above the height of the bimini and also opening the bimini windscreens forward to increase flow.
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Old 24-12-2012, 10:05   #40
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Re: Ventilation in Aft Cabins/Center Cockpit

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It would be quite simple to modify a dorado or mushroom vent or even a hatch to fit a pipe on top and remove the water trap while you are at anchor.
So every time you anchor, you're going to take the dorade box apart and modify it, then do it again before you sail? Let's be a little realistic here.
By the way, a dorado is a fish.
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Old 26-12-2012, 09:42   #41
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Re: Ventilation in Aft Cabins/Center Cockpit

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I repeat; you cannot exhaust air through a dorade box. There is no direct connection between the funnel and the through deck fitting and the dorade box itself has holes to allow any water that enters through the funnel to get out, not go into the cabin.
You cannot exhaust air through a dorade box, period.
Interesting. I clearly exhaust air through dorades. On a windy day I can feel the air coming out of the funnel.

I think you misunderstand something about ventilation and aerodynamics.
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Old 26-12-2012, 10:24   #42
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Re: Ventilation in Aft Cabins/Center Cockpit

One way to confirm if your dorades are venting air OUT of your cabin is to take a candle or a stick of incense and hold it near the vent to see if it is drawing. A forward facing dorade certainly catches air to bring it into the cabin and I would belive that if the boat is closed up otherwise, the aft facing dorade will draw air out. Of course, if there is a large hatch open at the same time, there won't be much draw through the aft-facing dorade for the hatch will eliminate any suction through the dorade.
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Old 26-12-2012, 11:07   #43
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Re: Ventilation in Aft Cabins/Center Cockpit

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Interesting. I clearly exhaust air through dorades. On a windy day I can feel the air coming out of the funnel.

I think you misunderstand something about ventilation and aerodynamics.
Please explain to me how the dorade in this pic could possibly exhaust air.
No matter how you apply aerodynamics, won't any outgoing air really be from the water drain holes? Ours have fairly large holes all around the base for water egress.
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Old 27-12-2012, 10:23   #44
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Re: Ventilation in Aft Cabins/Center Cockpit

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Please explain to me how the dorade in this pic could possibly exhaust air.
No matter how you apply aerodynamics, won't any outgoing air really be from the water drain holes? Ours have fairly large holes all around the base for water egress.
At anchor turn your dorades to face aft. At a dock turn them so the opening faces downwind. Then reverse the heads on all your red arrows. Stop by Auspicious and I'll show you with smoke. Alternatively read Roger McAfee's "The Warm Dry Boat." If neither of those work for you give me a holler and I'll provide the references in the professional literature.
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Old 27-12-2012, 17:38   #45
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Re: Ventilation in Aft Cabins/Center Cockpit

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I repeat; you cannot exhaust air through a dorade box. There is no direct connection between the funnel and the through deck fitting and the dorade box itself has holes to allow any water that enters through the funnel to get out, not go into the cabin.
You cannot exhaust air through a dorade box, period.
If air is scooped in, let's say by a forward hatch open, windscoop etc.. it has to exit somewhere, a rear facing dorade is an exit point due to the positive pressure coming into the boat. If the dorade is facing aft, I would imagine it has at least a feeble neg pressure .
Dont get me wrong, Not a big dorade proponant, I think dorades are probably the least efficient of any ventilation devices due to the "watertrap" design, , but good if the boat is unattended.
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