Has Anyone Seen an Insulated Steel Hull ?

[Honey Ryder]

like you, i am about to insulate my steel trawler.

the question is whether to cut pieces to fit or spray. there are pros and cons to each method.

cut to fit - this takes a long time and the pieces must be cut accurately to fit well. if i do it this way then i intend to glue some spacers to the hull so that the insulation sits off the hull. condensation will then run down to the horizontal stringers and pass through the limber holes i have drilled ultimately ending up in the bilge where it will be pumped out. doing it this way means that i can easily inspect the hull in the future by lifting out the insulation which can then be replaced. i intend to lay further insulation over the vertical steel ribs.

spray - very quick, but if i want to inspect the hull in 5 years time how can i do it without scraping the stuff all away. and then how to replace? and if any condensation does occur, how does it escape? i have read stories and seen pictures of rusty hulls behind spray foam.

it has taken me a lot of effort and time to spot blast the interior hull (2hp compressor, potblaster with 2mm nozzle and garnet abrasive) and i am about to paint with amerseal and amercoat epoxy system which should be good for a good few years. i don't want to make the wrong decision now about insulation.

while the spray option is attractive because it is quick, i fear that i may be risking problems down the road.

the fact that superyachts use spray foam is not convincing...boats these days are consumer products built to sell, and do the manufacturers really care about the consequences of spray foam in 15 years?

i would love to convince myself that spray is the way to go, it would save me a lot of time and effort. but my instinct is telling me that cutting and fitting is better.

i am curious about delfin's use of cork and fibreglass, what is the theory here?

[Delfin]

Originally Posted by Honey Ryder

like you, i am about to insulate my steel trawler.

the question is whether to cut pieces to fit or spray. there are pros and cons to each method.

cut to fit - this takes a long time and the pieces must be cut accurately to fit well. if i do it this way then i intend to glue some spacers to the hull so that the insulation sits off the hull. condensation will then run down to the horizontal stringers and pass through the limber holes i have drilled ultimately ending up in the bilge where it will be pumped out. doing it this way means that i can easily inspect the hull in the future by lifting out the insulation which can then be replaced. i intend to lay further insulation over the vertical steel ribs.

spray - very quick, but if i want to inspect the hull in 5 years time how can i do it without scraping the stuff all away. and then how to replace? and if any condensation does occur, how does it escape? i have read stories and seen pictures of rusty hulls behind spray foam.

it has taken me a lot of effort and time to spot blast the interior hull (2hp compressor, potblaster with 2mm nozzle and garnet abrasive) and i am about to paint with amerseal and amercoat epoxy system which should be good for a good few years. i don't want to make the wrong decision now about insulation.

while the spray option is attractive because it is quick, i fear that i may be risking problems down the road.

the fact that superyachts use spray foam is not convincing...boats these days are consumer products built to sell, and do the manufacturers really care about the consequences of spray foam in 15 years?

i would love to convince myself that spray is the way to go, it would save me a lot of time and effort. but my instinct is telling me that cutting and fitting is better.

i am curious about delfin's use of cork and fibreglass, what is the theory here?

I wanted something that if it is exposed to flame, won't burn, and if it smolders, won't kill you with toxic gases.

Acoustical cork is used in building skyscrapers to provide sound insulation. It has a polyurethane binder, so is waterproof. If you have a solid paint system on the bare metal, covering the hull with cork eliminates condensation, and as I said, it not very dissimilar from what was used on steel hulls for the purpose for centuries. It also has excellent sound deadening qualities through absorption of vibration. If you have to remove it, it can be scrapped off without much difficulty.

Before applying the cork, I sprayed the hull with a product called QuietShip. It has a new name now but there are other manufacturers. It adds 10 mils of a compound over the paint that should make it last indefinitely, as well as providing further sound deadening. For rust to appear, you have to have oxygen. If done correctly, there will be no oxygen next to the Quietship, and if there is a trace, it won't make it through the paint system to work on the steel.

The Coast Guard fiberglass batts are for insulation and are made to conform to CG regulations on fire safety. The CG doesn't care whether it is good heat insulation or not, but 2" is sufficient for us in addition to the R value of the cork.

[hellosailor]

FWIW there are fire-resistant foams, AND fire-retardant (not just resistant) paints. Probably a worthwhile investment on a boat.

Rule of thumb for household fires is that they double in size every 30 seconds, and the average small extinguisher will only help in the first 30, i.e. a desk trash can's worth of fire.

[Delfin]

Originally Posted by hellosailor

FWIW there are fire-resistant foams, AND fire-retardant (not just resistant) paints. Probably a worthwhile investment on a boat.

Rule of thumb for household fires is that they double in size every 30 seconds, and the average small extinguisher will only help in the first 30, i.e. a desk trash can's worth of fire.

If you read the product descriptions even for foams containing retardants, they still advise you that they can still burn, and when they do since they all have isocyanate in them, they all give off cyanide gas. topcoating with a flame retardant paint seems to me to be well worth the cost and effort as well.