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Keeping A Sailboat Cool Without Shore Power

Mar 20, 2015
2,255
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
Good Morning All !

We plan on spending more time on the boat next summer and I have some questions for the nerd/engineering types and those who live in tropical climates.

Background:

  • My wife and I make every effort to acclimatize so that we can maximize our comfort outdoors.
  • We can usually handle heat due to acclimatization.
  • This summer was continuously hot and I expect it won't be uncommon now.
  • I hope to spend more time on the boat during the week at the dock, while working. (unfortunately not swinging towards the wind)
  • A 30ft sailboat doesn't really work well with the technique of sealing the interior during the day. (drapes and closed portlights work well but I can't see keeping the companionway closed all the time)
  • We don't have shore power at our marina.
  • The boat has a dodger but will have a bimini and filler piece next summer.
  • We don't see needed cooling every day.
  • The water temp in the southern portion of our lake is supposedly 20ºC to 25ºC in summer. I assume the marina is higher because it is not much deeper than the draft of the boats.
  • Peak summer air temps are around 30ºC ish. Summer humidity is well above 50%.
  • Lowering humidity would make us comfortable, but I can't see how to do that enough without having a shore power and keeping the boat closed up.

Question:
What are you using to cool the boat, if you don't have shore power ?

Has anyone here tried using a recirculation cooling loop with a solar powered fan to help cool the interior ?
I found posts online that mention using a cooler full of ice, but using the lake water itself seems like a better idea. (dry ice, combined with block ice, in a cooler sounds great for keeping food cold, but i can't see how you could reasonably do that without freezing the recirculating coolant , if only used occasionally.

A reflective boom tent would help.

Thanks all !
 
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Mar 20, 2015
2,255
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
fans, airflow in general.
Fortunately our C&C has 1 opening port on each side, a solar vent, and an opening port in the aft bulkhead between the cockpit and cabin. (In addition to the usual forward hatch)
 
Jan 4, 2006
3,905
Hunter 310 West Vancouver, B.C.
Cover your ports and hatches wherever possible.

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I'm still working on hatch covers which are more difficult but more important.
 
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Mar 20, 2015
2,255
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
Cover your ports and hatches wherever possible.
Hmmm I can see how that is better than curtains inside.
If I make them the right size they could also protect the starboard and port teak rails above the portlights.
 
Jun 14, 2010
1,726
TBD Looking for my next boat CT
Search the web for "hatch umbrella" "breeze booster" "wind scoop" "hatch scoop" etc. with the right accessories you can direct the wind from whatever direction. A hatch umbrella can be rigged to cover the hatch when there is rain (but not wind). If rain and wind, your ventilation options will be very limited.
 
Mar 26, 2011
2,937
Corsair F-24 MK I Deale, MD
At dock, box fans rule. One in the fore hatch works if you are in the cabin (also very useful on exaust if using varnish etc.). If you are in the cockpit, one that tilts is better. If you are buttoned up for rain, put it on a table in the cabin, aim it up, and think of it as a ceiling fan. In fact, on low, they don't use much power.

One came with my last boat (cruising cat), and I wondered what it was for... until the first hot day.

And all of the above advice.

PS. 30C is not hot.
 
Jul 1, 2010
869
Seaward 25, Catalina 350 Erie, Pa
I got a set of Outland Hatch covers for our boat. They work great. Between that, lots of ventilation ports, complete canvas cover over the cockpit, and some fans, we're in pretty good shape up on the Great Lakes, at least when we're anchoring. This summer has had some of the hottest stillest nights we've experienced. In the marinas, we've used our ac more than any other year (no way to run it at anchor).
 
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Jan 11, 2014
7,839
Sabre 362 113 Fair Haven, NY
To sum the many good suggestions, provide shade for the boat and don't block air flow. A boom tent works well, a fore hatch shade works well. 12v fans strategically placed help a lot.

Add a dodger and a connector to the bimini. This allows you to keep the hatch open.

We added some DIY sun shades that make a big difference. These are rectangles of a shade material with multiple grommets. The shades are moved from place to place in the cockpit depending on the sun angle. We used something like this fabric from Sailrite.
 
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Mar 20, 2015
2,255
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
PS. 30C is not hot
:biggrin:

That is what the "ish" is for. We hit 36 or 37 this summer. Likely 33 as an average high.

I can handle 38 39 40 but sleeping in that with high humidity sucks. (-40 is ok too but the water gets hard)

The Admiral has never done as well for cold and hot extremes. I suspect she needs to live in Hawaii. Hehe.

Unless I misunderstand, box fans don't work for long with only solar and batteries ?
 
Mar 20, 2015
2,255
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
If rain and wind, your ventilation options will be very limited
Fortunately our marina is very sheltered.

This summer has had some of the hottest stillest nights we've experienced. In the marinas, we've used our ac more than any other year
Yup. Exactly why I posted this question.
At anchor it was fine but at the dock it sucked. Especially when our marina is nice and sheltered
 
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Jul 1, 2010
869
Seaward 25, Catalina 350 Erie, Pa
Concerning 30c and hot...If it were 30c and 90 + % humidity, this northern raised guy would check into a hotel for a night's sleep! Luckily, we never saw night time temps that high this summer, but had every bit of the humidity, which made sleeping hard at times, even at anchor. In the marinas, it was much more uncomfortable (until we turned the ac on :) ). We leave SC in the summer to get away from that, but some of it followed us up as far as Lake Michigan this year.

Concerning ventilation in the rain...We put 3 eyebrow hatch covers on 3 of our side hatch windows. It keeps the rain out so long as it isn't blowing sideways much. Also made a sunbrella cover for the hatch over the vbirth. It gets anchored on 4 corners and spinnaker halyard holds up the center. Works well until tstorms blow the rain in sideways.
 
Mar 20, 2015
2,255
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
We added some DIY sun shades that make a big difference.
Good idea. I made one for the south facing sides of a pavilion/pergola I built this spring. For some reason I didn't think of it for the boat.

The boat already has a dodger so besides a filler piece and a Bimini, it looks like I will be sewing a lot.
 
Mar 20, 2015
2,255
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
I found a post on sailnet that discusses the the idea of using sea/lake water as a cooling loop with a fan.

Evidently the rule of thumb is you need a minimum 12- 20 F difference to affect any cooling. With a marina, (and many anchorages) being too shallow, it would be so borderline to be effective enough for the effort.

That thread does mention that a misting system, on deck, on a fresh water lake.. works well and consumes little power.

I have a spare 12 VDC sprayer so that might be a fun experiment once I make the bimini and filler piece and see what the boat's existing DIY boom tent looks like.
 
Jan 4, 2010
983
Farr 30 San Francisco
A dip in the water can cool you down. With me swimming somehow lowers my core temp a little bit and allows me to be OK in the heat for hours afterwards. The sun is beating down with 1000W per square meter. Shade is important. Paint your boat white.
 
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Mar 26, 2011
2,937
Corsair F-24 MK I Deale, MD
:biggrin:

That is what the "ish" is for. We hit 36 or 37 this summer. Likely 33 as an average high.

I can handle 38 39 40 but sleeping in that with high humidity sucks. (-40 is ok too but the water gets hard)

The Admiral has never done as well for cold and hot extremes. I suspect she needs to live in Hawaii. Hehe.

Unless I misunderstand, box fans don't work for long with only solar and batteries ?
Yeah, I know people that think a season low of -5C is winterizing.

Depends on the fan and the battery bank. At dock, of course, it does not matter. At anchor, we only used it a few times when we had to button-up for a combination of rain and bugs. Run on low it's about 40W or 3 amps at 12V DC. They move a lot of air compared to little marine fans, and you probably have one you could try. And they're only ~ $25.

I had a cruising cat at the time, with 3 group 27 batteries. But I use it only my F-24 at dock when working on something, particularly in the cabin. Really sucks the fumes and dust out.