Home is a Fiberglass Hull

One of the biggest projects on my personal list for Andromeda is insulating her interior hull spaces. The benefit of this effort is brought home to me each time we spend the weekend on Andromeda and realize that it takes running the diesel heater constantly to keep the boat warm and the interior free of condensation just from our living activities. And it hasn’t even been that cold outside yet. This will only get harder as the winter progresses. Without insulation on that hull, even with the good air circulation this boat has, I can look forward to mildewed cabinet interiors and clothing that smells like mold. I feel about mold and mildew the way Mike feels about fog: it is a malevolent  force of nature that is out to get me. And I cannot let it win. Ever. My nose is a fine tuned instrument of mold detection. I can always smell a cat litter box, a wet diaper, and mildew. Gauntlets have been thrown down. Lines have been drawn in the sand. The game is on.

I would really like to find a paint product that insulates against condensation and is easy to apply. I live in a complete dream world, apparently. What I’ve found so far is Mascoat Marine Insulating Paint (or, more accurately, a ‘thermal insulation coating’). It looks like a first class product but it’s expensive and difficult to apply. It has to be sprayed on, and I have to sand the fiberglass first. Andromeda is a 47 foot boat with a ton of cabinet space.  Oy vey, that’s a lot of sanding in weird positions, not to mention all the taping off and the fact that I would have to wait until summer for the temperature to be warm enough to apply this product.

Not to mention that this is how this product is usually applied. Notice there is no cabinetry in this photo. Photo courtesy of Mascoat.com.

I would love to find something easier in an insulating coating; something I could brush or roll on, for instance. Would rubberized roofing paint work? Would the insulating paint they sell for homes work? When I’ve researched this question on the sailing forums, I have generally found ideas about what I can glue on my hull like cork, or bubble wrap insulation, etc. I’d prefer not to go this route unless I have to. I’d like the insulation to extend pretty far below the water line, and anything that I glue onto the surface has to have excellent and complete contact with the hull or mold will grow behind it. In addition, there will always be some condensation as long as we’re in cold water, so I can’t use anything that will get soggy or hold water. Water must be able to get to the bilge. An insulation coating would be much easier in many ways. Please comment if you have suggestions.


Anyhow, so while Mike was wrangling with the engine room, I spent time poking around in Andromeda’s nether regions. She has quite a lot of storage space and many cabinets have false floors, opening to reveal yet more storage space that I can only hope I never need to use. All of these need to be empty in order for me to get at the hull, so I got to emptying and suddenly it felt like being on a treasure hunt. So much stuff! At the end of the day I decided there was too much stuff taking up space and I better bring all this loot home. What I found was yards and yards of Sunbrella canvas like this:

What is this thing? It’s folded about 8 times so it’s huge. FYI these tiles are a foot across, to give you an idea of the size of this thing.

Apparently this is some kind of boat cover. It was much too big to spread out on our living room floor, so we’ll have to take it outside during the day and see how it works. I cannot imagine needing something like this in our climate, or using something like this while cruising, so it’s possible that what it represents is hundreds of dollars worth of Sunbrella canvas in excellent condition. Either way, score!

Also this:

Just long rectangles. I thought maybe windscreens, but then there is that zipper…any ideas?

In one cabinet I found a long bag made of polar fleece, obviously protecting something fragile. Upon opening it, I found these:

Maybe this is a score, maybe not.

What we have here are two panels that fit at the top of the companionway: one with a bug screen, and one made of plexiglass or something like that, creating a window to see out into the cockpit. These will be dead useful! Then there are tiny bug screens for the opening ports. These are in very poor condition, but the frames are still good so I’m putting their refurbishment on my project list. Why buy new ones when I’m fairly sure I can make these as new again? They are even labeled as to which port they are for. To the left are what appear to be bug screens for the opening hatches. To be sure, we’ve never needed anything like this in Washington, but I know we’ll want them other places.

In the drawers of the quarter berth cabin I found a pile of soft and stretchy terry cloth covers.

Soft terry covers

I think these are slipcovers for the Bottom Siders cockpit cushions to keep said cushions from sticking to skin in hot weather. A definite score! They are used and faded, and a couple of seams need to be mended, but I am totally prepared to repair  and refurbish these suckers with a little thing I like to call ‘fabric dye’.  I will have to count them to see if there are enough for all of the cushions. Another small project.

In the v-berth, I found this:

Biggest score ever.

This is a full cockpit enclosure. Yay! It looks like it is quite well made and needs only to be cleaned and one zipper replaced. When the weather warms up, I’ll give it a good scrub outside and let it dry in the sun, then take it to a canvas worker and have that zipper replaced. I am so looking forward to having an enclosed cockpit in this area.

Cheap Tricks in Boat Decorating

And speaking of refurbishing, before we left the boat this weekend, I got a wild hair and took down the curtains in the quarter berth, aft head, and master cabin. These curtains are really well made and of high quality. The fabric, however, is faded badly from the sun and from just being pretty old. However, these things are expensive to buy, and I am not in the mood to make them. Whoever did these did a damn good job on them so I’m going to reuse them.

Really nicely made curtains, faded from years of use.

I brought them home and washed them with laundry detergent and bleach, then decided I would try my hand at dyeing them. I am planning to use a combination of blues and greens, perhaps some lavenders, in the interior of this boat and I had two packages of teal green dye in the cabinet. So why not? I had no idea the fiber content of this fabric, but it felt like it was a cotton/poly blend. I brought out my big canning pot, filled it with water, added a cup of salt, a dash of laundry detergent, the two packages of dye, and some eye of newt and set it on the stove to heat. The curtains were already wet and clean so I placed them in the dye bath and commenced to saying my incantations while I stirred. There is something about dying fabric that feels so much like magic!

Lovely dye bath!

After about 30 minutes in the hot water it looked like they were dark enough. I figured they would not be perfect, but that’s the beauty of hand dyeing fabric. All those little imperfections are fine and will totally go with my vision of casual comfort below deck. Turns out the color is great, and I saved the dye bath for the next batch. Total cost of this redo? Less than 5$. That’s my kind of remodeling. Et Voila!

Once we start heading south, I’ll put some clear UV film on the ports to protect the color from fading.

I can’t wait to hang these back in the cabins and do the ones in the salon and v-berth areas.

If you have insulation on your fiberglass boat, speak up. Let me know what you use and what the pros and cons are of that substance. I’m hoping for a paint-on solution but my dreams may not fall on fertile soil.






23 thoughts on “Home is a Fiberglass Hull

  1. Wow, you really DID score, and bravo on the amazmo curtain makeover! A full cockpit enclosure? A full boat cover? In Sunbrella!? I’m calculating the costs in my head…. What a treasure chest of added-value. Looking forward to updates on uses for all of your cool finds. Happy Thanksgiving!

    • Happy Thanksgiving, Belinda! All that Sunbrella is definitely worth a small fortune. But it’s the cockpit enclosure I’m really excited about. Can’t wait to see how that works.

  2. Oh wow! If ever someone deserved a ton of loot, it is you and Mike. You see, the universe is paying you back for your generosity to us! Happy thanksgiving. Xxx

    • We were wondering today whether you and Alec were celebrating an American Thanksgiving, or whether you were on your way to either India or Canada. Email me an update!

  3. My only thought on the canvas is an extension of the cockpit enclosure? Mongojo has half a offer in place and after we found matching canvas zippered panels, we spent an hour putting the puzzle together. Two zippers need replacing, and we need an additional steel arch across the aft of the boat and we have a full enclosure. Love treasure hunts!! I found Guatemalan coins and a resort bracelet from Paradise Island, Bahamas when I was cleaning our boat out. Was so excited to know I was taking her back to warmer waters!

    • Could be. When the weather warms up, we’ll try putting it all together down at the boat and see. I think two different owners did the blue canvas and the cream canvas. The sail covers and most of the winch covers are cream, but the older winches that are still on the boat have blue covers. We also found two Mexican blankets, some Mexican disposable diapers in the engine compartment, and some Mexican soap. There are some really cute water color prints that might be from Mexico, too.

  4. It’s hard for me to imagine *any* paint being an effective insulator that’s because no matter how good an insulator it is, it will be applied in a thin film.

    Your best bet may be spray-applied urethane foam. It’s what they use on the steel narrow boats in England, under the interior finishing.


    • Thanks for you suggestion, Bob. Mascoat is actually put on fairly thick and is more of a ‘coating’ and less of a ‘paint’. It must be sprayed on in layers. That being said, you make a good point about any kind of regular paint. And the urethane foam bears further investigation.

  5. Hi! Really enjoying your adventures!

    The next first thing you should do is buy 2 dehumidifiers of the 30 to 40 pint/day size. Run them 24/7. The condensation, mildew and odors will be minimized and the boat will feel warmer. It took me 20 plus years of boat ownership to figure this one out!

    The next step is to find and seal any and every leak in the house and decks. Check all ports, hatches, chainplates, stanchions, etc every place you have access to where a hole has been drilled thru to the inside of the boat. Do what ever it takes to keep the rain outside where it belongs.

    Before you spend the huge amount of time, effort and BoatBucks required to insulate the hull try adding more BTU’s or consider moving somewhere south of 32 degrees north!

    • Hi Jeff! Glad to have you along for the ride. You are so right about the dehumidifiers. Friends of ours who live on a Nonsuch 30 in the Seattle area introduced us to comfortable living aboard when they showed us their dehumidifier. We are certainly in the market for those as soon as we’re finished bleeding green over the engine and all its accoutrements! 🙂 Likewise, your comment about sealing leaks falls on fertile ground here. I have located a couple of small leaks that will be fixed either while the boat is on the hard, or this summer when it will be warmer and rebedding deck hardware will be easier. Now if only it were possible to move south of 32 degrees just now! I fear that one will be waiting a little bit longer.

  6. We installed a fiberglass insulation with a foil cover (<1/2" thick) on the hull of our aluminum fishing boat. After we taped the seams, the volume of condensation decreased remarkably. One small humidifier will remove the moisture with two aboard. The insulation can be covered with wood or frp to achieve a factory look. No mold observed.

  7. WOW, check out all that stuff! I’m impressed. It reminded me of when we emptied our boat after buying her, we still have so much stuff in the closet in bins. GREAT score on all that canvas and cockpit enclosure. I bet the big canvas is a sunshade. You’ll need one in the tropics I would think to keep the boat cool.

    I hope you find something for the insulation…spray foam insulation may be the way to go if you can tape off the areas that need to be protected.

    • Having to insulate after the boat is all fitted out is just a pain in the behind no matter what direction we go. I’ll probably test a couple of different things and then decide.
      Don’t know if the canvas is a sunshade or not. I think it might be a boat cover but we’ll have to wait for the weather to calm down before we can really work with it.

  8. Hi folks:
    As I continue to renovate Arabella, I found some patches of incredibly durable insulation inside a couple of lockers, obviously added since she was built 35 years ago. I took a sample to every marine place I could imagine to match without success. I tested it and it appeared to be pretty well immune (well, sort of) to flame and is a closed cell graphite grey foam with smooth surface both sides and impervious to water penetration. I figured it may be a product made for sound insulation on automotive products. Still no luck!
    I finally found a match at the “Foam Zone” here in Victoria. http://www.foamzone.ca/ Product available in approx 5′ X 8′ sheets both 1/8″ and 1/4″. There were no brand stickers on it. I bought 1/4″ and have applied it to hull in lockers with sprayed contact cement. Works like a hot-damn! Looks really good too. The good news is that it is under $1.50 sq ft.
    Cheers, Tony

  9. No matter which insulation you use, use a closed cell system in order to keep water out of it.

    I’d say Armaflex, probably what Tony Roberts has searched for in his above comment. I know it form the HVAC world on this side of the pond.
    Flexible sheets of grey closed cell foam with a strong adhesive on the back. Used to insulate the external air intakes in order to keep condensation out of the equation. 10mm is plenty enough for 30°C temperature difference. (5F outside, 60F in the insulated attic. – Sorry did not have more of a difference lately. 😉 )

    So that should be pretty much what you need. Clean the fiberglass and glue sheets directly onto it. It is a also available without glue backing. – But then you need to apply a special glue by hand, probably not that useful.

    An issue is cost, at least on this side of the pond. 10mm: ~$3 per sq feet. Prices may be better in the US.
    There are variants of this product, even a Lloyds approved one. (So use in ship building is pretty much guaranteed.)
    Also, other companies should have similar products so this should be at least a start for another search.

    • Yep, like all boating supplies, its mighty expensive foam. Biggest challenge has been to get it to stick securely. A primer coat of contact adhesive, followed by another liberal coat about 30 minutes later seems to do the trick. One coat was less than satisfactory and air pocket voids resulted.
      Good luck!

      • Armaflex seems to be the standard for people who want a solid insulation that sticks to the hull. Too bad about the problems you had getting it to stick, Tony. That’s disheartening, especially as you are right about the price. We are swamped with the engine and propulsion refit at this point so I have had to put my dreams of hull insulation on hold. But once this part is done, I’m getting back to it!

    • I’m wondering if any of the closed cell foam variants are less expensive than the brand name. With a 47 foot boat, we have a lot to cover. Also your comment makes me wonder if buying something from the HVAC world might be cheaper and work the same way. We all know that once you slap the word ‘marine’ on it, an item sells for twice the price. Thanks for the information!

  10. Uhm, that is already a HVAC price over here.
    It is next to impossible for me to find US prices. So the following ones again local, this time from a single insulation vendor and without VAT to make them somewhat comparable.

    AF/Armaflex, the normal one
    10mm self adhesive 18 Euro m^2
    10mm non adhesive 11 Euro m^2

    NH/Armaflex, halogen free, Lloyds certified
    10mm self adhesive 53 Euro m^2
    10mm non adhesive 43 Euro m^2

    Ensolite is an industrial variant made by the same company which has four versions. – Can be bought in other places but has different characteristics.

    Competitors, a quick peek at data sheets showed very similar characteristics.
    Aeroflex Firo
    10mm self adhesive 10 Euro m^2
    10mm non adhesive 9 Euro m^2

    Aeroflex HF is a halogen free version but has no certs as far as I can tell.

    Kaiflex KK+
    10mm self adhesive 15 Euro m^2
    10mm non adhesive 11 Euro m^2

    Kaiflex HF, halogen free with a Lloyds cert
    10mm self adhesive 43 Euro m^2
    10mm non adhesive 34 Euro m^2

    K-Flex ST
    10mm self adhesive 11 Euro m^2
    10mm non adhesive 7 Euro m^2

    K-Flex ECO, halogen free with a Lloyds cert
    10mm non adhesive 25 Euro m^2

    So there are definitely competitors, after all Armaflex is proud to be on the market for over 40 years. There also should be some competitors based in the US, the above are all Europe centric.

    Armaflex has the big advantage that it is flexible and can be glued on the whole surface. No voids, no air, no water, no mold.
    Another option is to go for extruded polystyrene foam (XPS) aka the pink stuff. (Not Styrofoam.) The color is vendor specific.It’s probably the cheapest closed cell insulation I know. (20mm thick 3.50 Euro m^2) The problem is that it is not flexible, which means voids, now you need to fill them or have a working rear ventilation. – And probably still risk mold. Something to consider.

    (PS: If you do the conversions and the prices are too mind boggling, here is a diversion: gas converts to $7.75 a gallon – no brand, regular. 😀 )

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