Insulating a Hull- Does it Work-How to Do?

[Cheechako]

I would stay away from bubble wrap, have found it's looses air just sitting around often.. then you are left with nothing but a plastic sheet.

[roverhi]

Boat was in the water and didn't see an advantage to going below the water line where temps would be pretty steady and not as extreme as areas exposed to ambient weather. Condensation is a problem above the water line especially the overhead and cabin sides because of condensation from your breathing as well as temp differential in and out.

FWIW, wintered over in Norfolk, VA in an uninsulated boat with electric heaters. Condensation was a MAJOR issue. Fiberglass liner and every surface was dripping throughout the winter till temps got into the 50s. So much condensation it pooled in low areas and so heavy thought I had deck leaks. A dry source of heat would make life a lot more comfortable. All those fixed port lights are going to be a major source of condensation.

Listen to Cheechako. Have built and rebuilt a couple of boats. No matter how hard you try not to, boats suck up money. At least start with a better boat than the POS Buccaneer. At least you'll have something to show for your efforts with a better boat. Have seen decent boats in no worse condition offered for only a few thousand. There is a glut of smallish boats on the market and few buyers. Possibly a result of income disparity as large boats are moving but not at the lower end.

Originally Posted by biker6977

Roverhi- why just down to the waterline- or did I misunderstand? I thought at the waterline is where the condensation would happen the most. The boat I'm looking at is really bare so I"m thinking I"ll insulate all that I can get to. All the cabinets etc will come out so I don't think there will be much that I won't be able to get to. I am lucky that a good friend built a wooden shrimp boat and has lots of FG experience and a woodshop so that's a big+ for me- and he loves doing this! A few 6 packs and we'll be rolling. I am already envisioning what the interior will be like- guess the bug bit me already and I haven't even seen it in person yet!

[Matt sachs]

I used closed cell fire retardant spray-in expanding foam to insulate the hull above the waterline. It's 2-3 inches thick on the hull, and 3-6 in the overhead. Its not cheap, but its cheaper than rust repairs.

[biker6977]

Cheechako- good point on the bubble wrap- but it would have been easy. Will have to do more thinking and investigating.
Duck55- makes sense. I am thinking I'll insulate everything I can get to which should be quite a bit, also figuring it will help with sound deadening- Cars I"ve used sheets of lead but best not to add weight to a boat. I think the rubber self stick would do a good job of that as well.

[Cheechako]

Originally Posted by roverhi

Boat was in the water and didn't see an advantage to going below the water line where temps would be pretty steady and not as extreme as areas exposed to ambient weather. Condensation is a problem above the water line especially the overhead and cabin sides.

FWIW, wintered over in Norfolk, VA in an uninsulated boat with electric heaters. Condensation was a MAJOR issue. Fiberglass liner and every surface was dripping throughout the winter till temps got into the 50s. So much condensation it pooled in low areas and so heavy thought I had deck leaks. A dry source of heat would make life a lot more comfortable.

yes, same up here in the PNW. water dripping off everything in the winter with two small electric heaters. Hull was cored above the waterline on one boat and that helped some on that one, but hatches portlites etc still drip alot.

[jwing]

Condensation occurs when a surface is cooler than the dewpoint of the air around it. You can try to keep the surfaces of the inside of a boat from getting cold by insulating, but if you don't add heat, the surfaces will eventually cool down anyway. Insulation slows heat transfer; insulation does not stop heat transfer. Many boat owners, like me for instance, can show you mildewy boat insulation that gets soggy from condensation.

What you want to do is lower the dewpoint inside your boat so its is less than the outside temperature (water or air). You lower the dewpoint by lowering the relative humidity (RH). You lower the RH by either raising the air temperature or extracting water vapor out of the air (usually through condensation and proper collection and removal of the condensate through a drain - this is how dehumidifiers work), or both.

So you can insulate to retain heat, but you will have to add heat. With a boat that small, you might be able to get by with a small electric heater, powered by PV, and skip the insulation process. If you have acces to shore power, you could use a dehumidifier.

I solved my condensation problem by covering my boat with a tarp and an air space between the tarp and the deck, which cuts down on convective and radiant heat loss at night, and keeping the companionway and a hatch open, which allows daytime air, with its low RH and high temperature, to heat and dry the boat out naturally.

One last thing: before you try to insulate or heat your boat or do anything to get rid of mildew, you must first make sure there are no leaks into your cabin and no standing water (like in the bilge). Otherwise all you efforts will be for naught.

[hellosailor]

I would suggest that anything which allows for warm moist air to stagnate in the insulation, like fiberglass, will rapidly become a mold farm. You want 100% sealed insulation, which may mean using spray foam, or closed-cell material that is glued and sealed to the hull in a manner that prevents any stagnant warm air from being trapped. Given half a chance, mold and mildew will take over your boat.

[biker6977]

I've been thinking - yes I know that's a bad thing. I live in the south on the gulf so I need to not only stop condensation but keep it cool. I'm now thinking I should be a reflective barrier against the hull then insulation like on a house- the reflective part goes on the side usually hot. Question- what will this do when the water is cooler than the air which is almost always- I think. Also- I will be plumping and wiring this boat as well. Is it reasonable to run some pvc along the hull to use to run the wiring and for any future wiring runs? I don't think I'll need much plumbing other than the galley sink. I plan to use a composting head and no sink in the head. I'm not sure about a shower at this point but feel I should prepare for the possibility. I"m also leaning toward spray foam. Easy to Use

[roverhi]

For the summer, keeping the sun off the deck will make the boat infinitely more livable. Making a tarp that you can string up over the boat from mast to stern will be a god send. Lived comfortably through a Tahiti summer with a tarp over the main deck and a pup tent like affair on the foredeck that kept the sun off the deck as well as acting as a windscoop.

Would think if you are talking southern Mississippi, it's heat that's going to be the issue not the cold.

[biker6977]

I'm in LA ( Lower Alabama) and it is hot and humid here more often than not. So I do need to keep it cool and I will be making a tent type thing to cover the deck and cockpit along with getting a bimini. I will be making wind scoops as well. I do not want to go the AC route so will do all I can to eliminate the need for that. Now I"m wondering if I should leave the hull below the water line uninsulated to help cool off the boat???? And insulate only above the water line since heat is more of an issue than cold but then the part below the water line will for sure get condensation on it. Anyone else down in the warm humid climates have any words or experience of wisdom to bestow upon me???? Just when I think I have it figured out I start to rethink!!!!

[JPA Cate]

Biker, windscoops are great, but I think you'll need some 12 v. fans to move the air for sleeping.

You can set one up to suck cooler night air into the boat, and let convection clear out the warmer.

Are you planning to be self sufficient for electricity? I'm thinking aimable solar panels at the stern. If you're clever with it, you could de-mount them when you pass the boat along.

Y'all have a great attitude. Sounds like you're going to have a lot of fun with your project.

Ann

[duck55]

Reflective material only works if there is an air space to reflective the heat back to. With out the air space it dose not do anything. They do not do much unless there is a large difference in temp.

Changing our boat paint color made a huge temp difference for us in the summer. We only have 1 AC and it's in the cop pit. We do not use a lot of heat, but do use 3 dehumidifiers.

I have never wintered where the water temp was below 50*f. Everyone puts on sweat paints and when sitting around you grab your blanket. We do heat the cop pit and the living room as needed (60*f).

Years ago when I had a Caterman we did a lot more heating and cooling. I'm sure all my thoughts on this would change if I changed the type of boat I have.

[sapient sue]

Hi Biker 6977

Our boat was built in Sydney Australia for the tropics and is cork lined (1"thick) from the waterline to the deckhead. However, when we cruised to the Pacific North West we soon realised we needed to insulate from the waterline down as our lockers were filling with condensation.

We used what was available in Port Townsend and used the normal insulation used in the housing industry (hence available in any hardware store). It is a silver coated bubble plastic. We used 3 layers with spray adhesive glue ( be careful to take enough breaks as the glue can be toxic when head down in lockers, we used plenty of fans). This worked really well but next time we visit we shall be sure to purchase a de-humidifier.

Best wishes for your project - Sue

[biker6977]

Ann- I will for sure being getting some 12V or solar fans- I would like to be as self sufficient as possible which is why I don't want AC- my understanding is that it would be very hard to power AC with Solar even if I had a cat to have a solar farm- which I don't. I am very much looking forward to doing this and enjoy all the ideas and knowledge shared here.
Duck- so the reflective won't help- ok, I"ll scratch that part- thanks!
Sue- did you have any condensation problems in the tropics from the water line down?
Will condensation only be a problem in colder weather due to dew point?

[biker6977]

I have an appointment to go look at the project boat this Sat. Ihaven't broken the news to hubby yet- perhaps I should send him out diving for the day.....