Hull Insulation

Early on in the project, I had decided to add 'insulate hull' to my list of upgrades. It seemed like an easy thing to do and while the interior was being torn down it seemed like a good time to do it. I figured it would add a week or two to the project. I was wildly wrong in that estimate. If I had known how much work it would add I might have skipped it. I am glad I didn't know however because I am quite happy with the results. A warm dry interior regardless of outside temperatures and conditions is quite nice.

After doing some online research I settled on a product called Armaflex AP. Its a closed cell foam marketed specifically for the marine industry. Closed cell to resist water absorbtion, built in fungacide to resist mold growth, resistant to fire and has a low toxicity level when it does catch fire, its flexible and adheres tightly to the hull which eliminates any dead space where condensation can accumulate, and it is dead easy to apply. After looking over the information I figured 3/4 inch thick foam would be more than adequate. When I talked with the tech rep he suggested 1 inch foam. More is better right? The insulation comes in 3 foot squares or 48 inch wide rolls. I ordered two rolls and have used about a roll and a half.

The plan was to cover the entire hull within the cabin space including under the cabin sole. I left the cabin top alone for three reasons: 1.) It would be hard to do with all the compound corners. 2.) It would reduce the headroom. Headroom was one of my most important priorities when I searched out this boat and I wasn't going to reduce it any more than necessary. 3.) I had hoped the balsa coring would add some insulative qualities of its own and it would be enough.

The insulation covers the entire hull within the cabin area and therefore, everything that attaches to the hull must be in place before cementing the insulation over the rest of the exposed hull interior. This complicated the job because I had to have everything else planned out before the insulation could go in and yet the insulation was really the first thing that had to go down before anything else could be built on top of it. It made for a lot of late night thinking sessions.

Once I was sure and was ready for the insulation, the application itself was quite easy. The foam is cemented in place with a proprietary contact cement that looks an awful lot like Dow 1300L; a yellow smelly gooey substance that really works well. Cut the foam to fit, paint the hull and foam with the contact cement, wait two minutes, place the foam in position, get it right the first time because the foam bonds instantly with the hull. When I did mess up I cheated and squirted a bit of expanding foam in a can into the gaps.

Before the insulation went in, I had to make allowances for the inner paneling that would cover the insulation. The foam is soft and I needed to protect it. That meant attaching small blocks of wood to the hull or narrow fiddles to the bulkheads so that inner panels could be installed that would form the inside of the hull surface. I have a lot of storage bins located against the hull so much of the inner liner is common 1/4 inch fir plywood, sealed with linseed oil and painted with Bilgekote. Cherry veneered plywood and some upholstery liner also make up the inner surfaces of the cabin area.

More because 'it can't hurt' than anything else, I added some foil lined 'Reflectix' insulation inside the foam insulation. My thinking is that the foil will help reflect radiant heat. I don't really know if it adds much or not. The hull is curved and the interior panels are straight (it was just too much work for too little gain to do otherwise) leaving a a gap between the foam and the panel. Since the Reflectix is secondary, I simply laid it over the foam and sandwiched it between the foam and the protective paneling.

The insulation project is ongoing but here are some pictures to demonstrate what is happening.

Behind the settee backs which will all be storage lockers.

Basically the same thing behind the galley.

Unfortunately, I didn't take pictures of the insulation under the settees. Picture this, fir 2x2's cut to follow the contour of the hull. They are then glued to the hull about 2 feet apart. Foam insulation is glued between the fir and then plywood panels are screwed down to the fir strips. That is what the following picture shows.

The head and hanging locker areas had the same treatment. After the pictures were taken, insulation in the head area was continued down the hull where the head seacocks are now. Under the shelf that the toilet sits on is insulated too.

Its hard to see but there is some insulation peeking out from under the V-berth water tank and to the right under the storage area to starboard and aft of the tank. To either side of the tank, the white is the painted inner plywood liner covering the insulation. Insulation goes up the sides in the V-berth too. Covered with upholstery, this should be nice to snuggle up against.

That's the general idea for the insulation. More specifics, if any explanation is warranted, will be under the specific sections of the project pages.