How to insulate steel hull

[Swede78]

Hi New here..
i am from Gothenburg Sweden and i own a steelhull sailboat. its 46 fot
John Pugh copy .

But i need to renovate the boat inside and rip out all the interior and redo it..
how do i insolate the hull best?

i live in northen climate and it can be a hot summerday and the next day its raining. rockwoll? or plastic? i hade a ideea to not use anthing at all just let the steelhull be and add a half a Ince wooden beam and plywood soo the hull can bread behind the Wood? .. its maybe not a good ideea but i dont want to rip it all out again after like 6 years…

any idèa?

sorry for my poor englishspelling…

[Andreas W]

Hello and welcome to the Forum.

On my steel boat I used a product called Solarshield. It's an acrylic polymer blended with ceramic microspheres. It is primarily being used on metal roofs. The layer is only 500 micron thick (0,5 mm).

I did not like to use foam for a number of reasons, the main reason being that you can't see what happens behind the foam on a steel hull.

[Lepke]

I built steel boats, mostly commercial. The best insulation was spray in expanding foam after the hull had a good protective coating. The foam lasts the life of the boat and glues itself to anything. The thickness is controlled by the spray gun. It's planed off and sealed in with a fiberglass layer and the final paneling, plywood or stringers needed for cabinets glued to the fiberglass.

On fishing boats we used about 4" foam in crew areas and in extreme temps, hot or cold, needed little heat or cooling. There should be companies that do foam in most areas of the world.
If not that, I'd use styrofoam panels.
Don't use any insulation that can absorb moisture alongside steel. Steel doesn't need to breathe, it just need a good barrier coat. I used spray on zinc. It also lasts the life of the boat, but requires ventilation if welded later.