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Old 11-08-2015, 02:03   #1
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Steel Hull Insulation

One should have access to all parts of the hull, yet steel needs insulation to beat condensation and not bake/freeze/deafen the crew.

I'm leery of sprayed closed cell foam because you don't know what's under it without ripping it off. Fire protection and out-gassing of tasty nutritious things like formaldehyde are also big points.

An alternative came to mind: sheets of foam, or rockwool encased in barrier membrane (tyvek, like in house walls) or with an integral vapor barrier (see below), attached to 3mm expoxied ply with a laminated timber rim to shape it. The interior of the hull is to be reinforced with mostly cold molded frames rather than steel (weight considerations); This would give the insulation panels something to slot into.

That way I can pop out a whole insulation panel and see the plating, even weld, without the mess & hassle of tearing out/burning/replacing stuck on foam. If I'm careful with the layout of the joinery I can cover the whole inside of the boat apart from the bilge sump and still have access any time for those regular inspections. Rough guess 2 inches total depth, and a handy panel width (space between frames) of 2 feet: tyvek comes in 9 foot rolls, so 4 panels to a width plus overlap for taping.

A suitable membrane:
http://www.dupont.com/products-and-s...qs/wb-faq.html

A suitable foam:
Zotefoams - foams for Marine

Rockwool the way the big ships use it:
SeaRox MA 700 ALU (Shiprock ALU) - ROCKWOOL TECHNICAL INSULATION

I'm still nutting out ideas for insulating hatches and portlights, and the associated ventilation and drainage. Boats are systems, everything has to work and fit together.

How have others fared with insulation on steel hulls? Other hull types are welcome too...
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Old 11-08-2015, 07:33   #2
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Re: Steel Hull Insulation

A couple of quick thoughts, Going through the same issue with my alloy boat at the moment.

I am thinking I won't insulate under the cabin seats. I'll insulate the seat and seat front using ply/foam/ ply SIP panels or similar. Same with the cabin sole and under the bunks. That way I have ready access to the hull for most areas under the water, just by opening up the lockers or lifting floorboards.

Mold and condensation behind the insulation is my big worry. Not sure how to stop this, but blown in foam seems like a good option from this point of view. Otherwise the foam panels should probably be glued or stuck to the hull.

On snowpetrel1 I used polystyrene. Never again! very messy to cut. Though to be fair it worked well.
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Old 11-08-2015, 08:52   #3
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Re: Steel Hull Insulation

Quote:
Originally Posted by micah719 View Post
One should have access to all parts of the hull, yet steel needs insulation to beat condensation and not bake/freeze/deafen the crew.

I'm leery of sprayed closed cell foam because you don't know what's under it without ripping it off. Fire protection and out-gassing of tasty nutritious things like formaldehyde are also big points.
I am afraid having insulation that prevents condensation and having easy hull access is mutually exclusive. Close cell can be painted with fire retardant after being sprayed. Even latex paint is supposed to dramatically reduce fire potential. I have read that there are fire retardant spray foams. But lets talk about reality. The spray foam is going to be buried under paneling, bunks, settees, etc. There is going to be foam filled cushions all over the living spaces of the boat. If a fire gets the spray insulation, I don't think it really matters anymore.

Foam sheets used in house construction will burn just as much if not more than spray foams.

Out gassing should not be a problem either.

Quote:
Originally Posted by micah719 View Post
An alternative came to mind: sheets of foam, or rockwool encased in barrier membrane (tyvek, like in house walls) or with an integral vapor barrier (see below), attached to 3mm expoxied ply with a laminated timber rim to shape it. The interior of the hull is to be reinforced with mostly cold molded frames rather than steel (weight considerations); This would give the insulation panels something to slot into.

...
To prevent condensation one must keep moist air from the hull. I don't see how foam sheets for houses will stop air infiltration. Tyvek and other similar products allow moisture vapor to pass through the product. So it is NOT going to help prevent moisture from the living area of the boat getting to the hull.

When I designed my house, I DID NOT use Tyvek or similar product. I don't trust it at all and used building paper instead. There are books that describe how to build energy efficient houses for different climates and what works in the high humidity of the South US is not what one wants to build in Maine or Arizona. The problem with a boat, is that the boat could travel to completely different climates... In colder climates, plastic sheets are used to seal the interior of the house from the wall spaces to prevent moisture vapor infiltration into the wall structure. If moisture vapor gets into the wall, it can then convert back to liquid which is not a good thing.

Here is a link to a guy building a Swan 55 and his take on insulation, Building Koloa (Kama Hele): Insulation

Pretty sure that Dashew is using the same insulation, Armaflex, on his boats. The concern I have with Koloa is that they are also using rock wool. The problem with rock wool compared to Aramaflex and or spray insulation is that rock wool is not going to completely seal a space. There will be air infiltration. In Koloa's case will this matter since there is Aramaflex against the hull? From a corrosion perspective I think this is ok but I wonder about water vapor turning back to liquid in the rock wool. There is a post on the link that discusses this very issue in a cold climate with steel boats and this is an issue in houses in the same type of climate.

The only product that I have read about that allows sorta easy access and does prevent water vapor getting to the hull is Aramflex. One would still have to cut the material to access the hull.

Kasten has this right up on insulation, Corrosion Prevention, and mentions a paint product that is supposed to insulation the hull and prevent condensation. I am skeptical that such a thin layer of insulation would prevent condensation but Kasten knows his stuff. I certainly don't think the paint product could be the only insulation on the boat. Just no way a few inches of insulation can be the same as a few coats of paint.

Later,
Dan
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Old 11-08-2015, 10:16   #4
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Re: Steel Hull Insulation

This is a good topic for CF!

First, I am no expert on steel boats, and I have never owned one. So, take my comments below with a splash of saltwater. I am posting some of my notes and some of what I have learned by reading what steel boat owners and builders have written. I have read some books and many articles which have informed my POV but I don't claim to be an expert on their construction or maintenance. I just have a sincere and strong interest in them as I may want to own one someday.
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I have wondered about this same issue (Insulation on Steel Boats) for a long time, because I have always found steel boats attractive for various reasons.

What I have found so far is that there does not seem to be any consensus on what is the best thing to do.

Many steel boats I have looked at online were built in the 1980s and without any insulation in place. The problem here is that the typical steel boat has many nooks and crannies where the stringers and ribs join and each of these can form a pocket where water collects rather than going to the bilge. When the water stays there, it is potentially the site of rust.

Others (usually built-in the PNW) have insulation built in as the boat is constructed (often a home-built boat).

Some swear by the blown in foam. I think I understand their argument and it seems to make sense. After the boat has received a good anti-corrosion paint job in the interior (after blasting to bare metal to eliminate any corrosion) the boat is coated inside with the blown in foam that sticks to the metal surface and then creates a new "inner" surface to the boat.

I recently came across this advice from Brent Swain (designer of the "Brent boats" and "origami boats" built in steel). Because he has helped a large number of people build their own steel boats in the PNW, and they often have blown in foam, I found his POV interesting:

Buying any steel boat, if you drag your fingernails over the foam, you can hear a distinctive hollow sound where it has separated from the steel , Dig the foam out there, If you see rust, run from it. If you see thick epoxy , it is good. If you whack any low points in the hull, where water is most likely to sit, with a hammer and a centre punch, you will quickly find out if there is adequate thickness there.
As I understand it, the key to a long lived steel boat is to always fight corrosion (rust) on the inside of the boat especially. This means always watching for it and then quickly fixing it. In another thread I posted a link to a blog article that showed in photos the type of hidden corrosion (rust) that can make a steel sailboat something like "swiss cheese" with multiple points of rust eating through the steel hull. Here is that link and I do recommend people read it if they are considering the purchase of a used steel boat:
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I posted this segment in another current thread on a different topic. I am adding it here because I think it illustrates what the potential risk can be to having rust in a steel boat.

I like steel boats. I really do.

But, while they can be strong and watertight, it is prudent to look below the surface and especially inside in hidden areas for hidden corrosion.

Anyone considering purchase of one?
If so, I suggest you read the following blog post about the possible hidden things that can be missed, even by a surveyor. The interesting part is about half way down the page.

Fundamentals of Terra D'Agua part 4 — Terradagua[/QUOTE]

When you go to this linked blog and read it, carefully examine the photos in the blog.

Notice the holes that were punched through the steel plate with a screwdriver.

See the photo that shows a young woman sitting on the ladder (inside the empty hull). Notice the dark rust all around her on the steel hull. Look at the crevices, look at the panels, Notice the extent of what could NOT be seen because of the furniture (interior wood and cabinetry) that prevented seeing it.

Of course we don't know much about the boat. We don't know if it was a homebuilt boat or pro-built boat. We don't know when it was built. We don't know what kind of coatings were used on the steel. Those things matter too.
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In concept, I like the idea of removable panels of insulation of some kind. But, the issue with this (as I understand it) is that the panels allow an air space behind the panels and that is where the condensation will occur and the water will collect and then it is likely a place where rust can start.

The concept with the spray in foam is that any condensation will run down the inner surface of the sprayed in foam which it is inches thick and has created a mostly smooth inner surface so water runs over the stringers to the bilge.

The key is to get any water to the bilge where it can be pumped out. In this case of sprayed in foam, one assumes there is no corrosion (rust) behind that layer of foam. But there may still be some rust behind the foam if it separated from the hull (see Brent Swain quote above).
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Old 11-08-2015, 10:29   #5
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Re: Steel Hull Insulation

Thanks Snowpetrel, Dan & Steady.

Snowpetrel:

You've certainly got it easier with interior moisture-related corrosion problems with your alloy hull, though in your case dissimilar metals are the danger. Lead fishing sinkers, brass swivels, copper wire offcuts, nuts & washers....I suspect if something like that sat in water against the hull and a herd of wild electrons meandered through the results might be sad.


Dan:

Thanks for the detailed info and the link; the boat is awesome. Yes, Karsten is good value, I wish I had the cash to spring for his Valhalla 44, but 40 grand is too much for me; then again, perhaps it is also too much boat. I've looked at Armaflex and found a suitable product, the Class B variant, which gets me to an insulation thickness of either 40 or 52mm, I think I'd go for the thicker variant and have snug peace of mind if I go to cold places:
Armacell - ArmaSound Industrial Systems: Acoustic Pipe Insulation Systems Which Minimise Corrosion Under Insulation

The rockwool & tyvek solution mainly appealed for reasons of cost, but the vapour problem has been nagging. The foam product I linked above, Plastazote, entered my thoughts from studying Roger Taylor's fitting out of his Achilles 24, Mingming II. He simply stuck it on the inside of the hull, being THE Simple Sailor. So, I'll compare Armaflex and Plastazote. Mounting the stuff on ply backers was my idea of protecting the insulation and improving appearance: I'd be using plenty of light coloured paint and mirrors to make the insides of a small boat seem larger. The foam is closed cell so it won't ever see any vapour, and the hard ply surface will help further: they'll compress the insulation against the hull, not by much, but enough to keep air (and its water passenger) out.

As for the bilges, I'll consider Karsten's special paint, but I'll keep digging for a solution. The goal is dusty bilges!!

One thread already went on the insulation trail and fizzled after two pages.....there are likely more:
Metal Boat Owners - A Query on Moisture Control
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Old 11-08-2015, 10:39   #6
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Re: Steel Hull Insulation

Remember, I really, really LIKE steel boats.

Want to buy an old Steel Boat?
Read this article and look carefully at the many illustrative photos. They show how destructive rust can be to a steel boat. The rust scale was amazing.

The saving of WhiteBird

Here is a quote from the author of the article and the owner of the boat that was undergoing the repair due to years of rust. This particular caption was below a photo showing the owners scraping the blown in foam off the hull interior, revealing the rust behind the foam.

"I have read old books on steel boat building saying how good blown in polyurethane insulation is in steel boats... BULLSHIT! Water soaks it and retains it. the steel was a mess under the crap."
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Old 11-08-2015, 10:44   #7
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Re: Steel Hull Insulation

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Originally Posted by Steady Hand View Post
....

The concept with the spray in foam is that any condensation will run down the inner surface of the sprayed in foam which it is inches thick and has created a mostly smooth inner surface so water runs over the stringers to the bilge.

The key is to get any water to the bilge where it can be pumped out. In this case of sprayed in foam, one assumes there is no corrosion (rust) behind that layer of foam. But there may still be some rust behind the foam if it separated from the hull (see Brent Swain quote above).
Insulation is only part of the system to protect the inner hull. After the interior hull has been cleaned, the steel needs to be correctly painted with several layers of epoxy paint. The paint is going to keep the steel from rusting. The problem(s) occurs if the paint is not applied correctly or if the paint is chipped somehow. Insulation should protect the paint AND prevent condensation from reaching the raw steel.

Getting the steel prep and painting done is the most critical issue on a steel boat. Frankly, I think it is on a aluminum boat as well. However, many aluminum boat bilgers are not painted which I think is a problem. It is not a problem UNDER the insulation but in the bilges where non aluminum metals could make their way and cause corrosion. A couple of layers of epoxy paint would prevent that issue. Dashew recently posted test results of one of his older aluminum sail boats and the plate metal seemed to be as thick as it was when build. I dont' know if that bilges were painted but based on his FPBs boats, I don't think they were painted.

I was reading an article in an old issue of Pro Boat Builder about refurbing an aluminum boat that was built back in the 70s or early 80s. The boat had corrosion issues on top of some tanks that really puzzled the yard. They could not figure out why. Turn out the boat used copper pipe for plumbing and a water supply line was leaking over the tanks. The water leaking from the copper pipes manage to pick up enough copper that over time caused the corrosion! Who would have thunk it.

Later,
Dan
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Old 11-08-2015, 10:56   #8
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Re: Steel Hull Insulation

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Originally Posted by Steady Hand View Post
Want to buy an old Steel Boat?
Read this article and look carefully at the many illustrative photos. They show how destructive rust can be to a steel boat. The rust scale was amazing.

The saving of WhiteBird
Yeah, buying ANY old boat can be a problem. Lets not talk about blisters and having to fix lamination issues on plastic boats. I have seen projects on plastic boats that looked as bad as the WhiteBird.

It looks like he was painting the interior after the repairs. He does not mention, or I did not see, if the hull was painted when built. That is the key question. I don't think I would touch an older steel boat that was built without the use of epoxy paint. Having a qualified surveyor test the plate thickness is required. No, If, and, or Buts.

Later,
Dan
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Old 11-08-2015, 11:44   #9
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Re: Steel Hull Insulation

Revisiting an old thread and something very important......detecting and removing salt from steel as part of the pre-paint prep.

Chlor-rid International Inc. - Soluble Salt Testing and Removal

Here is a primer (heheh, get it? primer, heehee, in a corrosion related thread, hahaha, ahaha...ha....ahem) from that site aptly named Salts 101 (pdf warning):

http://www.chlor-rid.com/saltinfo/Salts101.pdf

The cobwebbed dis-masting thread of yesteryear and the tip from Eric Sponberg, unstayed mast champion and cool boat wizard extraordinary:

Dismasting - Why Does it Happen - How to Prevent it
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Old 11-08-2015, 12:59   #10
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Re: Steel Hull Insulation

As a former commercial fisherman that also built/repaired boats, I saw lots of before and after foam jobs. Usually blown in, expanding foam is used in the fish hold. Tuna is held at below 0 F. Holds will have 1-2' of foam, planed smooth and then a heavy fiberglass layer. As long as the steel was blasted and properly painted, the steel even after a decade or more was in fine shape.
In new construction, the living quarters and some other spaces were foamed about 4-6" deep all around -floors, sides, overheads. Then plywood and fiberglass. The fiberglass sealing the vapor problems of foam. The engine rooms were not foamed because of fire danger.
Besides insulation, the foam greatly dissipated engine noise. In a steel 80' dragger we built, with all engines running (800hp main, generator and hydraulic engines), in the galley you could not hear the engines.
Even in wood boats, properly prepared, foam didn't seem to cause problems. But that was before the EPA took away the good wood preservatives.
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Old 11-08-2015, 13:08   #11
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Re: Steel Hull Insulation

Thanks, Lepke. It would be interesting to hear what it was it like doing repairs to plate that had been covered with spray foam.

How far away from the weld zone was acceptable for safety, and how well did the new foam bond to the old afterwards? Also, were any pipe or power conduits submerged in the foam?
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Old 11-08-2015, 14:01   #12
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Re: Steel Hull Insulation

I have a 29 years old boat with spray in insulation.

(1) It should be a criminal offense to put stringers in a steel boat, they are an invitation to water traps and have caused almost every corrosion problem I have had with the boat.

(2) Spray in foam with a sealing coat of acrylic paint over blasted and painted steel appears fairly corrosion proof, does an excellent job of preventing condensation and sound reduction and the one used in my boat appears to be fairly inflamable in that it only smoulders which ceases when the heat source is removed.

(3) The places I have had corrosion were where the frames allowed water ingress under the foam. This appears to be a problem easily solved either by fully welding in thr frames or using stand-offs between hull plate and flames.
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Old 11-08-2015, 14:22   #13
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Re: Steel Hull Insulation

I wanted to do Armercell, but half the boat is already done with spray and it just made sense to stick with what has worked. Here's what we did a few weeks ago on our aluminum boat:





Here's what was installed before in some areas:





Here is a sheet we we're welding today thanks to corrosion. The DEA drilled into the keel cavities looking for cocaine and left them exposed. Water intruded and caused corrosion where the lead ballast is. It's a fun project in Florida summer heat!

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Old 13-08-2015, 15:23   #14
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Re: Steel Hull Insulation

Nice work, very interested to find out more about your foam kit. I thought it was only a professional option. What sort of cost was the unit?

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Old 13-08-2015, 15:47   #15
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Re: Steel Hull Insulation

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Nice work, very interested to find out more about your foam kit. I thought it was only a professional option. What sort of cost was the unit?

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We thought the boat was entirely insulated when we bought her, but the ex, ex-owner drug runners hollowed out the old foam and extended the ceiling planks away from the hull a few inches to fit more cargo.... Not a fun surprise. Anyway, the first kit was $290 for 200 board feet worth. We were actually able to do about 4' x 8' on two side with this to a thickness of 1.5 inches. We've since ordered a 600 board foot kit for $580 and will do the galley, head, pilothouse and quarter berth and touch-up a few missed areas in the vberth. I'm just thankful they left the zinc chromate primer intack.

They also offer a flame retardant version, but I was told even though it is closed cell, it has a better chance of getting moisture intrusion. We're covering the ceiling and overhead with marine plywood so any flame resistance seems a bit lost on us.

Matt


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