Hull material for arctic cruising

[TollyWally]

In a former life I worked in a shipyard building steel vessels, mostly for the navy. We'd insulate them with dense fiberglass bats with a canvas like covering. We spotwelded copper "nails" on 6-8" centers and pushed the bats
over the spikes. There was a clip you pushed on over the protruding spike. Then we covered the seams with either this high tech nylon cloth tape or a fiberglass tape with lagging compound. Kind of a pain in the ass to do nice work but it was possible. Most of the time we would erect panels over the top of the insulation. All on Uncle Sam's dime so I don't know how the costs were. A bit of a hassle to remove if you needed to weld on the outside hull skin but a million times easier than if you foamed it.

[apex1]

Did you refer to "Glassfiber" saying "Fiberglass"? Something like "Rockwool"?

These glass wool, or mineral wool materials have all some problematic properties.
First, they are more or less hygroscopic, some can hold hughe amounts of water. Not what we need.
Second, they hold fumes pretty good and long. That is a problem with almost all foams too. Except the rubber based ones, like Neoprene and Armaflex.

The reason why the navies like that stuff: it is fire resistant! A good characteristic in battles.
The canvas like cloth btw. IS fiberglas fabric, if we are talking the same stuff.
We used that combination (and all the commercial fleet too), to replace asbestos / plaster on steam engines, tubing, boilers etc.

Regards
Richard

[Ad Hoc]

Richard

yes, i believe he is referring to mineral wool..or Rockwool, with its trade name. May be even FireMaster.....but all the same things really.

[rugludallur]

I expect to launch my boat next spring, most of the steel work is done, just a bit more stainless. I'll probably move directly to making the interior before blasting and insulating, then unbolt the interior, blast, paint and I'm planning on using foam unless I find a better alternative (hence the question).
Rockwool is one of the worst insulators for marine application, it soaks up water like a sponge and looses all insulation properties in the process.

R.

Jarl
http://dallur.com

[apex1]

Originally Posted by rugludallur

I expect to launch my boat next spring, most of the steel work is done, just a bit more stainless.

You know stainless steel rusts! Get it electropolished if possible (and affordable). It will last several times longer!

Regards
Richard

[rugludallur]

Yeah, all the stainless is acid pickled and polished to a mirror finish either by hand or by electropolishing, above water it's all 316/A4(31603/1.4404) but below waterline (sterntube, etc) it's 318 (2205/1.4462).

As a design principle all mounting plates/flanges are stainless and there are no through hull/deck bolts, this way I keep the insulation nice and dry There are also no plastic through hulls, where plastic sensors/transducers are mounted they are inside a steel cap so even if they are crushed the hull will not leak, they are also mounted recessed to decrease the chances of damage.

A new design which we used is to make the actual sterntube removable, it's mounted inside a sleeve and screwed in from the inside and only welded in a single circle on the outside, this way it can be replaced and this also minimizes distortion from welding and the loss of corrosion resistance inherent in welding duplex steels.
I get shutters when I look at a nice steel boat that's been blasted and painted and someone has made 100 bolt holes in it for a genoa track and winches, no doubts where rust will form and when the leaks spring the water will all be soaked up by the insulation.

Everything up here in Iceland is required to be up to spec for Arctic conditions, extra strength in the stern, extra framing and Grade A steel are mandatory for the boat to get a registration along with X-rayd welds.

Most of the work can be seen in the boatbuilding GALLERY if one is patient enough to scroll through the photos.
Regards
Jarl
http://dallur.com