Building Custom Foam Insulating Batts for Inside the Hull

[Bene505]

What do you think about covering an inside section of the hull with wax paper or wd-40 and then spraying-in a layer of expanding foam.

After it dries, I'd cut it in half vertically so I can get it out, then trim it to a uniform thickness. Once trimmed for thickness, I'd put it back in place. This would make the insulation removable if I wanted to get rid of it.

I figure this would work for a lot of places where I have clear access to the hull. I would have to protect everything nearby (e.g. bulkheads) so that the foam wouldn't stick to them. I could choose a thickness that works well, perhaps an inch or two.

Any thoughts on this?

And, if you did this, how thick would you make it?

Regards,
Brad

[sailingdog]

Well, a lot depends on how you're going to be covering the foam. It will need some protective interior facing to protect it from damage.

[Bene505]

SD,

I was thinking about using Reflectix on both sides, after I got the custom fit made. Then marine vinyl over the interior Reflectix.

I'm on the boat now, setting up the webcam I got for it. That's another story -- I can't see the webcam from the internet (the marina's ISP can't give me a port mapping), but I can push out a snapshot every x seconds to my ftp server. So that wil be very good for checking to make sure it's plugged-in



I looked up the R-factor of epoxy as an insulator. It was very close to concrete, About 1/100th the insulation of Reflectix, if I got it right. (There are Europeon R-factors and U.S. R-factors. I may have gotten them mixed up.) When I got here, it was 45 degrees with 1500 watts of heating and 30 degrees outside. So a little bit of insulation will go a long way.

Regards,
Brad

[Faster]

That spray foam is pretty hard to control once it's released and has space to expand.. I suspect it would be quite difficult to get consistent results. It's also one of the stickiest substances known to man if it gets away on you.

It'll be interesting to see how well it works in reality vs theory!

[mitiempo]

Brad - that means you are our guinea pig. Hope it works. Keep us posted.

[JimMcGee]

Brad,
I'm not sure what parts of the hull you want to insulate, but have you thought about using rigid foam insulation with a layer of reflective foil applied with spray glue?

I'd think it would be easier to work with. You could score the back side to help it bend to the hull shape.

Jim

[scottyt]

jim reflectix is basicly bubble wrap with a mylar coating. IIRC it alone is about r3 per 1/4 inch.

[mitiempo]

Actually less. The figures are for 1" and Reflectix is only about 5/16" thick.
From this site: Capt'n Pauley's Virtual Boatyard -- Projects Galore!!!: Installing Insulation in Your Boat

[sailingdog]

Instead of reflectix, I'd use a mylar "space blanket" that was laminated to the foam. It won't add bulk, but will add a fair bit of insulation, at least in terms of reflecting heat.

[hellosailor]

Brad-
I would expect that any material which blocks off the inside of the hull, without actually being sealed to it, is going to create problems from condensate and mildew. Bad problems.
The traditional ways to prevent that are to either allow ventilation (i.e. by lining the hull with batts or lathing strips, and using those to create a vented air space) or to apply the insulation with adhesive, sealing it to the hull and moving the condensation zone into the interior of the insulation--where condensate can't form. Contact cement or basebard cement applied to the hull (a mildew resistant one, or one with added mildecide) and then a layer of ensolite or similar closed-cell foam would be a way to do that, sealed particularly well around all edges.
What's the worst that would happen if you spray foamed the hull? The foam might prevent a puncture from breaking through. And if you were holed, the foam can easily be torn away to effect repairs. I don't see it being an issue, except for access and aesthetics. (I wouldn't foam up into blocking the hull/deck bolts, for instance.)
If you DO decide to just lay something up against the hull, I'd suggest first cleaning the hull with bleach, etc., then spraying the hull with a mildecide to add that extra toxin before laying down the insulation. Once mildew gets a foothold....ugh.