Steel hull isolation: alternatives to foam?

Oh yeah, I wouldn't think about it without conduits and raceways... I built a house, and I know how easy it makes changing things with that... wonder why some people still don't use it on boats...

Looks like I won't be able to escape from foam... OK, let me hear it... what foam, PU, PE,...? How are the costs? All I get here are small DIY repair tins of foam...

Is it OK to use PU sheets? I guess I really like "sheety" stuff because teh thickness is easy to be determined as opposed to something which is sprayed on and then gets inflated some more...

 

I've used self-adhesive Armaflex sheets for hull and ceiling insulation of a steel boat. The workflow was really fast and the final result was very neat. So it's thumbs up from me.

 

foam alternatives

There are better substitutes , I believe, for foam insulation. In vessels where Coast Guard regulations prohibit the use of spray foam, the use of mineral wool bats is common. The product can be purchased in dense compressed panels with a foil covering. One product available in Canada is manufactured by Roxul, the same company that makes the housing industries mineral wool. It does not absorb water, is fire proof totally, and is easy to cut. Check out www.crossroadsci.com. In the U.S. I think it is known as Navy board.
cheers, Frank

 

There are no better substitutes!
Armaflex is the material of choice! EVERYTHING else is just wasteing money, because you will remove it sooner or later.
Never think about mineral wool, polystyrene foam etc. Thats nice for a house not for boats.
Just my 2 cent, after 33 jears of boatbuilding.

Regards
Richard

 

Thanks for the inputs guys! I know of Armaflex, but I think it costs much more then foam, not to mention the housebuilding materials... I might as well use foam then...

I am afraid to use anything with fibers... it MAY NOT get soaked, but if it does, it's down with everything...

 

Richard,
how do you do insulate with Armaflex sheets around conduits for wiring? I suppose one does have to use two layers of Armaflex anyway to avoid cold spots - can one lay the conduit in a gap between two sheets in the outermost layer covered by the inner layer? With two layers of, say, 25 mm each, does then the conduit have to be foamed in to fill the gap?
For a steel hull, would you use Armaflex with a selv-adhesive side or with those needles and clips? Thanks!
Walter

 

Before Richard replies (and eventualy negates what I'm going to say...) relative to the practical installation, let me remember you that air is the best thermal insulator. Well, actually vacuum would be better, but it's out of competition here, for obvious reasons...
So Armaflex+air+Armaflex is better than Armaflex+foam+Armaflex.
But you can also avoid the inner sheet of Armaflex. The lay-up Armaflex+air+plywood sheet (or interior lining or whatever you use to plate the boat inside) will suffice.

Example:
A hull wall section made of:
- 6 mm steel
- 25 mm Armaflex 0.041 W/(m K)
- 25 mm air
- 6 mm plywood
Gives a total conductance of 0.56 W/(sq.meter °C)

the same hull, but with this lay-up:
- 6 mm steel
- 50 mm Armaflex 0.041 W/(m K)
- 6 mm plywood
would give a conductance of 0.69 W/(sq.meter °C). That's 23% more!

Finaly, this layup:
- 6 mm steel
- 25 mm Armaflex
- 25 mm foam 0.035 W/(m K)
- 6 mm plywood
would give a conductance of 0.65 W/(sq.meter °C). That's 16% more than a solution with a layer of air.

 

Hardly! If it would be so easy, why bother with any kind of insulation in the first place? You could just keep a layer of undisturbed air between the hull and a layer of inner lining and be in the clear. But unfortunately you would get condensation on the inside of the hull. That's why people like me still figure what would be the best way to insulate ...
Or am I wrong?
Walter

 

me again on polystirene... as it's CHEAP, are there ways to make it fire-proof or at least make it less sensitive to fire?

 

Northman, basically you've made the question and you gave yourself the answer.

The problem is that you need the insulation in order to prevent two phenomena: the water condensation and the thermal dissipation.
If you make a gap filled with air only, you have created the best practical thermal insulation. But remains the problem of water vapor condensating at the cold hull.
So you need to introduce another layer to your insulation. You have to sheet the cold wall with a material which will avoid the air (and the water vapor contained within) getting in contact with it. That's what Armaflex will do. It's closed-cell structure doesn't conduct the water vapor and it also act as a thermal barrier (though less efficient than air).

If you decide to fill it all with Armaflex or with a foam, you still have an effective insulation, but the overall thickness required is bigger - therefore it will cost you more and will steal the valuable space from your boat's interior.

So, to sum-up the story:
If you want the thinnest possible (but effective) insulation, the best thing is to let the Armaflex (or another closed-cell foam) insulate against humidity - and partially against heat dispersion. And then let the air gap prevent the biggest part of heat dispersion. An insulating air gap lets you save internal space, weight and money. Which is not a bad thing.

 

NO
just forget about it! Forget even the name of it. It has nothing in common with the marine environment. And on top of all possible scenarios my predecessors described so correct, it is a very weak and brittle material and unable to stand vibration. It just falls into pieces after a while if installed between two skins.

Armaflex must not be installed in two layers, it is very easy to get a perfect result with just one. No cold spots possible if done correctly. Although there are some reasons to install two layers. The engineroom for example is done best with one layer of Armaflex AF against condensate, covered by Armaflex HT for heat protection. Sometimes it is neccessary to install a third layer between those two for better sound insulation, thats Armasound RD.
AF is allways the first (outside) layer on hull plates! And if you go below waterline with it, you´ll see the first dry ship in your life!
A heat resistant material for cable and fuel conduits is Armaflex Protect R-90.
We use all of the above mentioned even in our wood epoxy yachts!`Cos condensate is an issue on painted epoxy surfaces as well! And mold is a serious enemy.
You can have all these foams in a tubular shape to insulate tubes and piping, they fit perfect on standard sized piping (both metric and archaic).
The application of these sheets are done best with the special goo Armaflex delivers, but on real flat surfaces you can use the self adhesive stuff as well.
Do not forget to insulate the frames with a thin (10mm) layer of Armaflex AF before you install the sheets on the hull. Usually 25mm is sufficient against condensate everything above may add to your comfort.
Never mix two sorts of foam, they destroy each other sooner or later chemically.
Yes Arma is not a bargain at the first glimpse, but removing crap and installing it then anyway is by far the more expensive way.
Till the early 90´s we used spray on PU foam as most of the world did, it was nice to see them boats burning some years later, when the usual repair welding was done (and it kept the yards busy). Sheets of PU get loose from the hull after a while, forming a perfect ambient for mold and rust. (so did the spray on foam too in some spots) Mineral wool does this for free right from the very first day.
If you can afford a yacht, you can afford armaflex, if not, size down!
No, I do´nt get a commission, I still have to beg for a living.

daiquiri
Before Richard replies (and eventualy negates what I'm going to say...)
Impressive enough, I did´nt.

Regards
Richard

 

Richard, thanks for the persuasive post . How do you deal (on metal hull) the instalation of Armaflex and wooden battens used for ceiling and interior elements mounting? Do you Armaflex everything and then screw the bolt on say frames through it, or do you bolt wooden elements on the bare (painted of course) hull first, and then work your Armeflex around/over it?

 

The latter, never bolt structural elements through a foam, the bolt gets loose within some days. On interior surface the wooden batten does´nt need further insulation. If connected to the steel hull and (naturally) painted, you should apply a 10mm layer on it too.
AND I edited the post..........I allways do.
R.
R.

 

I believe the first part, the second one is a plain lie.

 

I do´nt know what believe means, I´m an atheist. But begging is possible at different altitudes........................