Has Anyone Seen an Insulated Steel Hull ?

[markpierce]

Spray on foam.

[Wand]

Originally Posted by catman2

...Spray in insulation will clog all limber holes and thus not allow moisture to flow to the bilge. Just because you don,t see the moisture dosen,t mean it is not there...

Spray-in insulation will probably serve the first owner well - but run from it if you're buying a used vessel. As Catman2 says, moisture WILL get in and corrosion WILL soldier on out of sight.

Good ventilation to every crevice and clear pathways to the bilge for moisture are the keys to long life in steel and wood hulls.

[goboatingnow]

Surely any form of glued in insulation will be less effective then spray on foam and merely encourage more rust. Most of the steel hull inside is out of view anyway irrespective of the type if insulation used. Given this I believe spray on is a better solution

Dave

[Unicorn Dreams]

And if you have emergency repairs at sea, hit a container, put hole in hull for example, you have to remove the spray in foam, not easy to do, and when you go to weld it will want to catch on fire or smolder.

Been there, done that on friends boat at the dock...

[Lodesman]

Perhaps maybe apply a galvanizing primer and/or epoxy tar to the metal before spraying in the foam.

[Delfin]

Originally Posted by Lodesman

Perhaps maybe apply a galvanizing primer and/or epoxy tar to the metal before spraying in the foam.

That is critical. On Delfin, the interior was heavily coated with Ameron prior to spraying 10 mils of sound deadening compound and prior to gluing on the acoustical cork. This is simply a variant on a technique I have seen on 100 year old Dutch hulls, who use tar instead of cork.

Again, one of the disadvantages of spray on insulation is that when it burns, you have your own little execution gas chamber, complete with cyanide gas. There was a product called Safety Foam being manufactured a few years ago, but it was experimental and I can't see it on the market anymore so perhaps didn't work out well.

Another disadvantage of foam is that it oxidizes, and as it does, its closed cell structure breaks down and it becomes a mop, so if used, overcoating with flame resistant paint is highly desirable, but a step that is frequently missed.

[David M]

My spray on foam has been in place since 1975 and it is holding up perfectly. If the boat catches fire I will either extinguish it or go outside.

Foam works to stop condensation because it is an excellent insulator. Other coatings are not necessarily good insulators.

[Delfin]

Originally Posted by David M

My spray on foam has been in place since 1975 and it is holding up perfectly. If the boat catches fire I will either extinguish it or go outside.

Foam works to stop condensation because it is an excellent insulator. Other coatings are not necessarily good insulators.

David, is it overcoated? I would assume so. If it catches on fire, foam also burns pretty well, which is why it is frequently painted with flame retardant paint. The reason I used cork was for it insulating qualities. It isn't as good as foam, but in combination with fiberglass batts seems to work well while eliminating condensation.

[S/V Alchemy]

Originally Posted by Lodesman

Perhaps maybe apply a galvanizing primer and/or epoxy tar to the metal before spraying in the foam.

I would hope that's a given, but my experience is that it is not.

[hellosailor]

Apparently the only open-cell spray foams are water-based products, which are somewhat newer than the traditional urethane or soy-based ones. And some folks have either used the wrong material (water-based open cell) because they were "eco-misguided" or cheap, as these foams are supposed to be cheaper as well as greener.

But given a typical, traditional, closed-cell urethane-based spray foam? No undercoating should be needed because the urethane itself is a damned tenacious adhesive. It sucks in water as it cures. Some are fire-resistant, others not. Like everything else on a boat, if you don't understand the materials and just buy one at random...

What, I can't use Elmer's School Glue for structural repairs? Why not, ITS ELMERS?!

[Capt. lulz]

I found this:
Capt'n Pauley's Virtual Boat Yard -- Projects Galore!!!: Installing Insulation in Your Boat

[Pauls]

Regarding rust under the insulation, the way to handle this is to do it right the first time. Prep the interior as you would any steel surface for paint, sandblast it. Paint it right, with an inorganic zinc primer and at 3 coats of epoxy. Then spray foam it down to the cabin sole. You do not insulate the bilge. Done this way, you will not have a rust problem under the insulation. Closed cell foam does not become soggy with water. It is a very good idea to paint the foam, after you've trimmed it to shape, with plain old cheap latex paint. It seals and hardens the surface and stops the foam from absorbing moisture. It makes it more fire resistant too.

Regards, Paul

[S/V Alchemy]

I suppose the utility of "plain old cheap latex paint" would make a nice change from the usual NASA-grade prices of marine stuff.

I'm going to go to Ameron myself (I've used two-part Endura for spot repair.) It's used to paint nav buoys, oil rigs and bulldozers that build breakwalls in Newfoundland, so it must be good.

[bangkaboat]

As Alchemy seems to be saying, don't insulate below the waterline. Sprayfoam or panels are both fine above the waterline, whatever is in your budget. Sprayfoam is cheaper, but more work. make sure all tabs, etc. are covered, or the moisture will seep through in these areas.

As for steel hulls rusting from the inside, not if properly primer/paint protected & maintained. The fact is that steel surfaces do not exhibit corrosion at the same rate as the layers between the surfaces. I've seen this so many times on marine vessels, where I cut into what seems to be a solid bulkhead/deck/deckhead, only to get through the surface layer & have the internal layers blow back on my torch & me, because the internal layersd have turned to pulp. Once that mess is blown away - without using the cutting O2 - the other outer surface is solid. That's why one has to inspect carefully on an older steel boat that one is considering buying.

[SabreKai]

Originally Posted by Pauls

Regarding rust under the insulation, the way to handle this is to do it right the first time. Prep the interior as you would any steel surface for paint, sandblast it. Paint it right, with an inorganic zinc primer and at 3 coats of epoxy. Then spray foam it down to the cabin sole. You do not insulate the bilge. Done this way, you will not have a rust problem under the insulation. Closed cell foam does not become soggy with water. It is a very good idea to paint the foam, after you've trimmed it to shape, with plain old cheap latex paint. It seals and hardens the surface and stops the foam from absorbing moisture. It makes it more fire resistant too.

Regards, Paul

This is pretty much the conclusion I've reached. I have to take all the styrofoam out, remove the roofing goop to see whats under. All the firring strips are huge, so they will be removed and replaced and I can see whats under them too. Once its all apart, it will be a bay by bay cleaning and repainting. I have a 5 gallon pail of Carboloy epoxy, which is what is on Espina, my old boat. That has been on since the fall of 2004, and aside from a bit of chalking is in great shape after 7 Canadian winters. I think it will do for my purposes.