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The Frugal Mariner
Saltwater Suzi and Cap'n Larry's "Boating on a Budget" 
How to's, Information, Education & Fun Stuff about Boats, Sailboats, and Cruising
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Insulating your Boat

There are four reasons to insulate your boat.

to keep it warm
to keep it cool
to keep it dry
to keep it quiet
For whatever reason you need to insulate your boat you get the other three for free.
If you, like most people, want to insulate to keep your boat warm, you'll find it easier to simply untie the docklines and head south.  Keep going until the butter melts.  Keep going until you find a place where people look puzzled if you use the term "snowshovel."  This would be our recommendation.  And we follow that advice when we can. 

Unfortunately, like many of you, our finances restrict such a carefree vagabond life.  Oh, we do like it though.  But if you absolutely must spend the winter in the cruel, cold north - you are either going to have to insulate your boat or put up with the cold surfaces everywhere, the condensation dripping from every surface and the divorce lawyers or you're going to have to insulate if you want to continue to use your boat or if you wish to liveaboard.

There are many ways to insulate, ranging from piling blankets and carpeting everywhere (which is tacky and mostly ineffective)  to tearing things out to the hull and insulating properly (which is messy, difficult, time consuming, effective and probably necessary.

This is what we did and we're happy we did it. 
Step 1  It's best to work in one cabin at a time.  First thing you have to do is decide which cabin you're going to start in and empty it.  This can be tough if you're living aboard.  We are fortunate in that we often house sit for friends when they are on vacation.  We try to use those times to get major work done. In our example here, we have chosen our V-berth area.  (Our boat has an aft cabin, so we could sleep there while we made the mess - however, it does make a mess, any boat project does.  Try to clean up the mess daily and take your significant other out to dinner.  It may be expensive but, again,  it's less expensive than a divorce lawyer.
This is what our v-berth looked like before we started on the work but after we emptied it all out.  We got rid of the incredibly ugly orange plaid cushions which came with the boat and Saltwater Suzi made new.  Many of the Morgan Out Island 41's have an upper and lower bunk in the v-berth which was really ideal for us when we first moved aboard and had our twin daughters with us.
Here's a view of the upper v-berth.  You can see that the original vinyl is coming unglued.  Notice the wooden stripping in the fiberglass overhead.  We had cut into it in sections to open it up for access. The problem had been that there was an opening all around the sides of the overhead.  Warm air would rise up in there, and condensation would pour back out.  We insulated up there with reflectix and spray foam insulation.  Problem solved.
Step 2  The fun part - the demolition.  (I always love tearing stuff apart.)  We ripped out the ugly vinyl and cleaned up the glue residue. We removed the door to the anchor locker.  Depending on the treatment of your ceiling you may have to remove the ceiling planks.  Label the backs and save them if you intend to reuse them.  It may seem obvious where they go as you're taking them out, but you'll find it very puzzling and time consumining sorting them out if you don't.
Step 3 After grinding the fiberglass to clean any surface dirt, scum, mildew and who knows what kind of primordial stuff that goes on back there we epoxied in some 3/4" x 3/4" x 3" pieces of wood. (We used poplar but almost any hardwood would do.)  Make sure you use a respirator or at the very least a dust mask while you're doing the grinding.  Have the vacuum cleaner in the room with you to suck it up as you go.  Mask off the door so the rest of the boat doesn't get covered with dust.  Notice the curved pieces we installed to help with the transition between the hull and the overhead.  This will make more sense as we progress.
3" x 3/4" x 3/4" wood blocks expoxied in place
Step 4 Using an insulating material called "Reflectix" (bubble pack with aluminum foil  - it's about 3/8" thick and you can get it at your local building supply store, like Lowes or Home Depot.)  We cut it with scissors and laid it in place to make sure it fit well.  Then, one section at a time we pulled it up and used a polyurethane caulk to hold it in place and, as importantly, to keep air from getting behind it and condensating.
Step 5  - Next we connected the wood blocks with 3/4" x 1/4" inch strips which will conform to the curve of the hull.  We coat each block with epoxy and the bottom of each strip and then use an electric brad gun to hold the strips in place until the epoxy dries.  We use three layers of the stripping so that, with the blocks, we have a total of 1 1/2".  Each strip ends up encased in epoxy.     Notice the gap we left below the portlights.  That's to leave room for the frame we will put around each portlight and still leave room for the opening knobs. 
Step 6 Next is another layer of insulation.  We choose a polyethelene foam in rolls because it was flexible and easy to cut and install. Again, we held it in place with caulk.
Step 7 - Another layer of Reflectix completes the insulation portion of the job.  A little high school science in case you don't remember.  There are three kinds of heat transfer - conductive, radiative and convective.  The foil pretty much takes care of the radiative - about 93% it says in the ads.  A second layer should take care of 93% of the other 7 percent.  The layers of bubble pack and polyethelene foam should take care of most of the conductive.  If you seal around the edges, you get rid of the convective.  So, at least through the hull, the insulation should be highly effective.  We've checked with a temperature gun and the surface on the inside of the boat is very much the same as the room temperature.
Step 8 The last part is hiding all your hard work.  We use a decorative wall panel of fiberglass that's available at Home Depot and made by Sequentia Corporation.  It's very thin; about an eighth of an inch and almost indestructible.  You've seen it in every bathroom at every McDonald's.   We use the tick board method of cutting it to the right size because it needs to be fitted to a compound curve.  You could make a template also, but we think the tick board method is easier.  Eventually we'll explain it elsewhere in this site if you aren't familiar with it. Once it is cut and installed, you can start installing the ceiling planks.  It's a good idea to mark above and below where the strips are so you can line up your screws precisely.

We cut and installed each - then removed and labeled its location on the back and finished it.  We used mahogany and finished it with three coats of satin polyurethane.  We let our screws show - in case we have to pull them out later.  We have made all of our built-ins so that they can be removed if we need to.   There are devices that can dress the ends of the screws if you find them unsightly.
Here it is with the rest of the ceiling planks in place.  Notice the trim strip along the bottom to hide all the plank edges.  It doesn't show once the mattress is in place, but it makes me feel better.
A few other words about insulation while you glance over the next couple of photos that show the finished product with the cushions and pillows made by Saltwater Suzi:  the hatch above is a horrendous heat loss in the winter and a heat gain in the summer when it is closed.  We cut a piece of 1" thick polyurethane insulation which fits snugly into the opening below the hatch cover.  Once we close the screen below, it's hardly notceable in the winter.  Sometimes, on the really cold days we put bubble pack cut to fit between each portlight and its screen as insulation. It still lets light in but keeps out most of the cold.
To help keep the heat out in the summer, Suzi made covers for each of the hatches out of Sunbrella.  Beneath it we put a couple of layers of Reflectix.  It stays there year round.  We have also insulated the mast by wrapping it with Reflectix and taping it in place and then Suzi made a wrap of a flannel backed vinyl to go around the outside.  A strip of velcro on one edge catches the flannel on the other edge to hold it together.  The mast then does not act like the huge heat sink it can be when bare.
One thing which we discovered was an added bonus - we asked a tugboat what our radar signature looked like.  We were concerned because our radar reflector halyard had broken and we hadn't replaced it. He said we looked like the Queen Mary.  We could only attribute it to the Reflectix we had on the inside of our hull the length of the boat.
Marks to show where the strips are.
A final addendum:  As I sit here writing this, at the end of December, 2010 the temperature outside is about 30 degrees.  There is ice on the water around the boat.  We have two 1500 watt space heaters going - one in the main cabin and one in the aft stateroom.  The temperature on board is 74 degrees. 

One additional thing we add when we have to stay north for the winter:   We put carpeting on the sole - especially in the areas where the sole is in contact with the hull and the cold water outside the boat causes the moisture in the air inside the boat to condense on the sole.. 
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