Combating the Moisture

As I have said before, the moisture here in the PNW is rough on liveaboards. As much as I love all of the snow we get in the mountains and the incredible skiing that is a direct result, the condensation that forms on bare fiberglass is a bit much to handle. Insulation was at the top of my list.

First we must ask, why does condensation form? To answer this, lets think of a glass of ice water on a warm day. It has everything to due with relative humidity and a thermal gradient (temperature difference). When water in the glass is cold, and the air around it it hot and full of water, the glass will actually draw the heat out of the air surround it, after all thermodynamics tells us everything want to hit equilibrium. The glass pulls the heat from the warm air surrounding it, and with it comes the moisture. When the air is humid enough (contains enough water) the water in the air undergoes a state change, it becomes a liquid! Water vapor in the air condenses and it condenses at the point where it contacts the thermal gradient (the glass). That same principle is working against you in a boat. There are three means to combat moisture, and only one is passive i.e only one will work without and work being added to the system. That one is to add insulation, think adding a coozie to the glass. The thermal gradient is reduced due to the insulation properties in the foam coozie, thus preventing insulation. That is what I will do to my boat. For the record the other means to combat condensation are airflow and dry heat.

If you remember from the original post, Cinderella was taken down to bare fiberglass hull she was raced to Hawaii in the Pacific Cup.

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I had my work cut out for me. What kind of insulation should I use? Where do I find it? How much do I need?

I quickly resorted to what I know best, google, to the forums I went! It turns out that boats intended to be used in cold weather usually have a layer of foam sandwiched between the fiberglass of the hull, but how do I emulate that?

I found another blog outlining one mans attempt, it seemed to work well for him, so I thought I would give it a whirl. The plan, glue 1×1 stringers to the hull, cut foam in insert between the stringers, cover with “ceiling.” For some reason boat walls are covered in ceiling and the “roof” of the boat is usually covered with a headliner.

For this project I went to my local Loews and picked up Reflectix and Polystyrene home insulation. Reflectix is basically bubble wrap with foil which is very easy to work with and makes almost no mess, however the main insulation property of Reflectix is radiant heat, I wanted to also combat conductive heat. To combat the conduction heat, I decided to use polystyrene, polystyrene is “closed cell” so it is impervious to moisture and therefore mold. I chose to sandwich 1/2″ polystyrene foam between 2 layers of Reflectix. Polystyrene is messy to work with, pieces of foam go everywhere and stick to everything when you cut it.

The end result made such a difference! No more damp boat!

I started by gluing in the 1×1 stringers which the ceiling would be affixed.

boat insulation, sailboat, insulation

I tried several types of glue during this process, regular silicone, liquid nails, and gorilla glue construction adhesive among others. Considering I once glued a propeller back together in a pinch using gorilla glue and it held up, its no wonder it turned out to be the best candidate here. For the stringers I used pressure treated 1×1, these are commonly used for porch railings, so I would skip the “marine grade” and save some $$.

Pro tip – the shorter you cut the stringers the better, especially if your hull has a very sharp curvature.

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The foam was then glued to the hull in between the stringers. Again I can’t speak highly enough about construction adhesive! To glue the foam layers together I used 3M spray on adhesive, it was a quicker way to cover lots of area, and worked very well.

Once the stringers are glued in and the foam is inserted, its time to add the ceiling. Classically, sailboats used wooden slats that interlocked with each other and are stained to prevent moisture intrusion and add to the aesthetic. I, however don’t have the time to wait for stain, and I don’t want to bother with cutting so many boards, I want to stop the moisture now!

That was when it hit me, flooring! Flooring is meant to take abuse, and is usually highly water resistant, and you can buy it ready to lock together, stained and ready to go, perfect! Thanks Bob Villa.

Boat ceiling, insulation, Cinderella, sailboat insulation

Again I put my trusty Ryobi kit to work and before long, Cinderella had a whole new look!

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Of course I had to place the wine box into the photo to highlight my progress.



2 Replies to “Combating the Moisture”

  1. Really nice work! So valuable to see. We are in the same situation, this winter we will take averting out and replace the interior of our boat.

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