A question about insulation in sub-tropical summers

[hd002e]

I have been on a lightly insulated Beneteau (8mm balsa cored deck with 10mm inside foam insulation) and the majority of my cruising is done in the mediterranean. Lately I have been getting ready to move onto a very well insulated Canadian made sailboat (4+ cm cored deck) and I am curious how that will affect my summers in the sub-tropical sun.

The Beneteau has been good, as long as I can get a nice breeze through the boat, it cools off shortly after the sun goes down and middle of the night I typically find myself pulling a sheet over myself with the fan blowing on MID. Except for mid-late August, I find no reason whatsoever why anyone would need an AC on a sailboat here.

With my new insulated boat, I have not had any summer experience but in the winter I realize that without any internal heating it takes longer for it to catch up with the greenhouse effect and warm up after the sun comes up on a sunny winter day. The Beneteau used to warm up much faster in the winter mornings.

I am calling on thermodynamics experts and insulated boat owners to share their insight and experience on this topic. Thank you!

[tkeithlu]

Think of it this way: Insulation is a thermal barrier. Heat does not cross it easily. A better insulated boat will better resist internal changes in temperature in response to outside changes in temperature. An uninsulated boat will promptly match whatever the outside temperature may be.

So, with the better insulated boat on a cold day, expect it to hold the heat that you add inside better than your old boat. On a hot day, the
better insulated boat will better hold the cool air that you flushed through it during the night.

That's all good, but what if the boat is cold soaked? Don't count on the morning sun to thaw it out. What if it's heat soaked? You'll have to actively pump in cool air, or sweat.

Second level: The internal temperature of the boat is not just air temperature. It is the temperature of all internal parts that themselves hold heat, as well. Water is the all-time winner when it comes to holding heat. Your tanks may resist changes in temperature. If your hull below the waterline is not insulated (they forget that) you're going to be fighting the ambient water temperature, whatever you want. It's tough to heat (cool) the whole Atlantic Ocean.

[sv_pelagia]

Is this the boat?
https://www.usedvictoria.com/sail-boats/35780732

The insulation will help, not hurt. It will help keep heat in during the night.

If too hot, open the hatches, use fans, and use canvas sun coverings (as shown in the photos on the above website).

In winter, the insulation is definitely a plus (but heat will be lost through the hull/water, as mentioned already). In some places, heating may still be needed (such as in British Columbia).

[JPA Cate]

Another thing is that running the heater for a little will eventually extend your winter time on the boat. It's all good. We found a wind scoop forward helped cool air get down into the boat in the hot places.

Ann

[hd002e]

Originally Posted by sv_pelagia

Is this the boat?
https://www.usedvictoria.com/sail-boats/35780732

The insulation will help, not hurt. It will help keep heat in during the night.

If too hot, open the hatches, use fans, and use canvas sun coverings (as shown in the photos on the above website).

In winter, the insulation is definitely a plus (but heat will be lost through the hull/water, as mentioned already). In some places, heating may still be needed (such as in British Columbia).

Yes!! That’s the boat, are you familiar with it?

I noticed in the hot sun the deck feels very hot under my feet compared to an uninsulated Beneteau. I wish I understood thermodynamics better

[hd002e]

Originally Posted by JPA Cate

Another thing is that running the heater for a little will eventually extend your winter time on the boat. It's all good. We found a wind scoop forward helped cool air get down into the boat in the hot places.

Ann

I need to sew a wind scoop and also rotate the hatches so they open forward instead of the aft position they are currently in.

[sv_pelagia]

No, not familiar. Was easy to find with Google.


I would re-consider rotating hatches, especially on foredeck. Less chance of water ingress facing backwards. In this case, a wind scoop will properly direct wind, even if open facing backwards. (Although, your forward hatch is not on deck but higher, on cabin, so not as big an issue.)


All our hatches on Pelagia face backwards. We replaced them all in 2018, but kept them facing backwards, and use windscoops to direct airflow.

[Mike Banks]

If you have cored decks, you need to go under them and using a fine drill, a millimetre or two, drill into the core at two foot by two foot intervals. That will stop the core delaminating--as pressure build-up in tropical heat can escape BELOW decks instead of creating tiny fissures in the deck above--and the inevitable pumping of moisture into the core and ultimate wetting and rot as the problem slowly worsens.

Such a simple ploy--and yet not many seem to know about it.

For extra insulation and sound-proofing, I used foam neoprene tiles, get about eight millimetre or more--(but any thickness is better than nothing) glued to the hull with spray neoprene adhesive, and painted them white with water-based plastic bathroom paint containing anti-mould benzalkonium chloride.

[ftamburrano]

Originally Posted by Mike Banks

If you have cored decks, you need to go under them and using a fine drill, a millimetre or two, drill into the core at two foot by two foot intervals. That will stop the core delaminating--as pressure build-up in tropical heat can escape BELOW decks instead of creating tiny fissures in the deck above--and the inevitable pumping of moisture into the core and ultimate wetting and rot as the problem slowly worsens.

Such a simple ploy--and yet not many seem to know about it.

For extra insulation and sound-proofing, I used foam neoprene tiles, get about eight millimetre or more--(but any thickness is better than nothing) glued to the hull with spray neoprene adhesive, and painted them white with water-based plastic bathroom paint containing anti-mould benzalkonium chloride.

WOULD IT BE POSSIBLE FOR YOU , MIKE, TO EXPAND THIS SUBJECT? Why there should be a pressure build-up if the deck is solid and does not contain liquids (nor their vapour pressure increasing exponentially when the ambient temperature increases) ? What is escaping from the little holes? Thank-you

[Mike Banks]

Air is always within the core material--and sometimes there is a small percentage of moisture because the decks are laid up in a work shed not a vacuum--and even if the core and fibreglass are vacuum bagged, that vacuum inevitably fails with time, and in any case the foam contains a heat-expandable CO2 or halothane gas and then the problems begin.

So to forestall the problems once the resin, glass and core are initially bonded, the holes will let any vapour pressure or pressure from the blown foam trapped in the sandwich escape harmlessly, below decks.

[hd002e]

This is very interesting and something that makes some sense. I noticed that any fitting installed on the boat from the inside (like a spice har rack) was also bedded with PU, so the previous owner was very meticulous about not letting any moisture into the core wven if it meant from the inside of the boat.

Originally Posted by Mike Banks

Air is always within the core material--and sometimes there is a small percentage of moisture because the decks are laid up in a work shed not a vacuum--and even if the core and fibreglass are vacuum bagged, that vacuum inevitably fails with time, and in any case the foam contains a heat-expandable CO2 or halothane gas and then the problems begin.

So to forestall the problems once the resin, glass and core are initially bonded, the holes will let any vapour pressure or pressure from the blown foam trapped in the sandwich escape harmlessly, below decks.