Hull insulation

I am rebuilding the inside of a 29 foot grp sailboat. After I have installed bulkheads I will add insulation to the inside of the hull, which is now sanded with patches of old dual component paint still there but no cloth or glue residue left from old sins. A stupilating requirement is that I want an inside surface that is hard plastic, painted with dual component paint and one that is possible, in theory, to hose down, or at least wipe off with soapy water. No vinyl linings or glued soft materials for dust and mould to grow on. I am basically making a sandwich construction out of a single laminate hull, but only above water line, and working around existing bulkheads etc. I realize I am not getting a smooth shiny gelcoat finish, that is not a problem. It can be uneven, but must be washable.
Now to the distance material. It has to be something that I can first glue to the hull, then cover with epoxy and glass over with a suitable cloth. This rules out anything that doesn’t glue with epoxy, but on the oher hand includes a lot of materials that would react badly with polyester and its solvents.
Im leaning towards xps, as in extruded polystyrene. My current plan is to cut 10, or 15, or perhaps 20 mm thick stripes and glue them with contact cement (one that will not dissolve them) to the hull either horizontally or vertically, to follow the curvature. Then glass everything over. Why contact cement and not epoxi? Because I figure the contact cement will hold the stripes to the hull while curing and stop them from springing out. Epoxi would not do that, or am I wrong?
Anyhow. All thoughts are wellcome, since I know from experience that I always end up with new knowledge after posting these thoughts and taking in the answers.
And also: what thickness should I go for? I am not planning to sail to the antarctic, but would like to get as good an insulation as I can within my design limits. More than 20mm there isn’t room for. But is there a big difference for each millimeter? If I were to settle for only five, there are fantastically practical sheets available that would cover the job at little cost, but that seems a little too thin. A very cost effective alternative would be to go for normal white polystyrene sheets (the stuff that the packing industry uses) but that seems to fragile and I envision it being ground to dust inside the sandwich with the first little movements of the hull as I start sailing. Thoughts on this are wellcome too.
Again, I am not striving for a boat ready for sub zero temperatures, just a nice and cosy interior for those autumn evenings. (I do have heating onboard). I know there is a notable difference going from singel laminate to any kind of condensation barrier, so thats what I’m after.
Grateful for any thoughts.

 

XPS, unfortunately, in the lower densities has very poor compression and shear properties. What does this mean? Well, off the shelf xps holds the laminate so poorly, that it peels off super easy, so easy, that peelply cannot be used in laminating, so easy that even poly used or table laminated; it peels up on the edges... As for the compressibility aspect, the stuff dents so easily, just installing it will result in some crush and delam.

However, there are ways it can be used that are better. You can, for example, glue paneling to it, think a washable board. The thickness of such a board eliminates the dent/delam issue and it won't peel easily like a thin layer of fiberglass and epoxy. And, it would be hard enough that way, for say surface mounting hooks or fixtures, etc.

If you insist on the slowness and difficult method of using xps and laminating; you'll need to buy higher density and heavier material to avoid this problem. I compare removing a laminate from low density xps to tearing a sheet of paper. It shears that easily. And the higher density, special order versions of xps have higher shear and compression ratings, so more like tearing 10 or 20 sheets of paper.

Before you remodel; do a bit of testing. Even the xps and washable panel idea needs the proper glue.

 

Also, komatex may work. See if u can get samples. Although I got scared it would move too much with temp change.

Also, epoxy coated wood might be easier, say a 6mm board on epoxy coated firring strips. The strips are speed glued to the hull.

Sherwin Williams makes a beautiful water based pre-catalyzed epoxy paint for hospitals that is very washable, although not solvent proof.

 

Fallguy, I do want to take in your knowledge but I am surprised at what you say about XPS, epoxy and fiber glass. I experimented laminating a small piece, maybe three inches wide. Using the pink XPS that is sold as floor insulation here. I’ll try and post a video. It shows me standing on the board. I weigh around 230 pounds.
Admittedly, peeling off a thin layer of fiber glass laminated to xps would be another thing.

 

Video does not seem to work. It shows me standing on a 20mm thick piece of XPS laminated on both sides with double layers of 450 grams biax, suspended between two blocks of wood. I do realize describing your own faulty video is poor evidence in deed, but perhaps, for the sake of conversation, you believe me.

 

Can you upload it to youtube and post the youtube link.

 

I see the video. 900 gsm glass each side is 1800 gsm and 1800gsm epoxy. Super heavy and super expensive as this thing goes.

See what a hammer hit does to it.

We also do not know the xps data. Denser xps will perform better.

 

1800 gsm is like 4 pounds of epoxy per square meter...

if you used a better core, for what you are doing 200gsm each side would be plenty

 

Ah, a misunderstanding, my fault. The heavy laminate that I made, and that shows in the video, is for the cockpit sole, where I am happy to have a very strong build and do not mind the weight. In the insulation project I intend to use a single layer of 200 g/m. I’ll try to get around to doing another test on that. But I do hear you, Fallguy. What would be a more suitable setup for the insulation? As I said, I want a sandwich construction with no trapped air and a completely closed, washable surface.
Also, the peeling scenario: Im guessing noone is about to start peeling off my laminated insulation from the inside of the hull, but one relevant factyor could be the movements of the hull while sailing. I do not want a scenario where my insulation start to delaminate behind the interior.

 

and this is the problem, 200g glass almost falls of of low density xps

just trimming the edges or cutting a piece to size with a saw will delam it

because of the compreesibility, a small bump of your hand will delam it at 200g

I have found it can work a bit better after sanding with 40 grit the entire surface which is quite a mess, but the sanding creates more surface area is all...it still peels and dents super easy

XPS can be purchased in higher density versions that will perform, but this probably lowers R value and drives cost.

How do you intend to affix the xps to the wall?

The picture was db1700. And this was the bottom of a livewell. The xps was used as a leveling shim, more or less. I added the laminate and you see the white areas? Those did not make it off the table even before delam. Peelply did it. So I gave a gentle pull and the glass sheared like tearing a single sheet of paper. I still used the xps as a shim, but glued it down and added a piece of corecell to the inside.

 

I realize you are not in US, but gluing a premade frp panel to the xps would be better if you found a good glue because the thickness of the paneling will protect the insulation from damage...you could epoxy coat the inside of the xps to reduce any chance for ingress, although water does not get in it much

this paneling would probably also allow you to screw the panels into furring, that is woth a cup washer; it will be attachable,..

USFRP.com - FRP Standard Wall Panel Prices https://usfrp.com/products/FRP_Standard.html

 

I am thinking along those lines now, as I realize epoxi and XPS may not be such a good idea…
How about this: I skip xps alltogether and instead I glue stripes (3-5 inches wide) of polyethene to a vinyl hull liner, the polyethene against the hull and the liner, naturally, forming the interior surface. These could be held in place by vertical teak battens screwed into small stringers, laminated to the hull (I have a large supply of teak) and form panels that would end up being some 13 mm thick. They could very easilly be removed, one at a time, for either cleaning or replacing. Polyethene because it is cheap, isolates well and is easy to shape against the hull. And I believe that 3m maka a range of glues that should work well.
But… If I made them into removable panels held against the single laminate hull, there would inevitably be a thin layer of air between them and the hull. Would condensation form in there and cause mould? I fear the answer is yes.
In that case, Ill probably end up glueing these panels to the hull. Admittedly, no longer having the desired ”inside of a fridge” solution, but still surfaces that are able to be cleaned thoroughly. My main concern with these foam backed vinyl liners is that they end up being dirty and torn along the edges, hence the idea of letting all edges be held down by teak battens.
In summary: this post describes an alternative path to the original topic of this thread, which was to laminate xps boards to the inside of the hull. I hope I do not confuse people with my rambling ideas! I have spent two years grinding and sanding the inside of the boat, and am now in the happy stadium of being able to start building up rather than tearing down.

 

Condesation there is certain.