Steel hull isolation: alternatives to foam?

Don´t worry about sharing .
First we find the forest, then we get the gun.............................finally it may happen we share the bearskin.

Welcome Murielle.

Richard

 

It was a quest alright, but I finally got my truck load of insulation. Maybe I'll come around to writing the whole story. In brief local distributors being such a rip off I did get my insulation from a distributor over 1200km away from here. Unfortunately, shipping ended up not being as strait forward as it should of been and our pricey load was temporary lost.....I discovered myself some surprising Columbo skills and found my insulation within reasonable time. Circumstances leading to the shipment being lost were ridiculous, I'm still shaking my head. Anyway, it's here and I'm starting insulating.

Was wondering, is there a trick other than a sharp blade and patience to cutting Armaflex?

Murielle

 

Not that I would know one. My guys use a large sized scissors on occasion.

 

Something for the task. Not sure if it's better than scissors with Armaflex but a must with foam cushions http://www.bosch-pt.co.uk/boptocs2-...m Rubber Cutter/101352/GSG 300/5753/index.htm

 

Hi everyone.
First post on the forum... that was quite some thread to read through! I'm looking to insulate my dutch barge. For various reasons its not practical to put any wood panelling over the top, and I wonder whether anyone could give me advice on whether you can paint armacell/armaflex? If so do you need a special type of paint? If so, where can I buy it?
Can anyone recommend an armacell/flex supplier in England for a small quantity?
In addition, I live in the south of England, could someone advise me how thick the armacell/flex will need to be to avoid condensation (for the same practical reasons I can't cover it with wood pannelling, the thinner I can get away with the better)?
Thanks in advance,
Will

 

I was about to post the same thing as Daquiri mentioned that if there is space between the stryofoam and the hull it will still condensate--it will be a ***** to get that to stick to the hull at every square inch..and you dont want moisture water pooling into one little section that didnt stick. im not sure how you get the styrofoam to stick well to the hull?--epoxy works but how do you clamp it tight to form the seal???
having said that i know if people who have used it...i have no idea how it turned out..for my small area- 510 sq ft.--ill have it sprayed on i think...

 

Actually gaps between a metal and the insulation don't condensate you get condensation only at the dew point in the temperature gradient. So providing the insulation is reasonable fit in the cavity you can have a gap between it and the plating.

 

mike not sure i understand that--if the insulation is to stop the metal from condensating--then where is the demarcation line--se we should let the insulation have gaps? leaving a 1 inch gap is ok?--then maybe a 6 inch gap is better? would 1/4 inch gap be worse or better??..to me the temp gradient would be there ONLY if there was something protecting the metal from varying in temp between the inner and outer hull causing radiant heat dissipation and trigger a change of state. and the only way i understand this from happening is to seal the hull off from the internal temperature??? thus it must be fitted tightly to the hull with no gaps...maybe im missing something here...its counter-intuitive to say there can be a gap..but this is why i ask...

 

Condensation occurs as Mike points out, at the dew point.

So, looking at this image here: http://en.wikipedia.org/wiki/File:Dewpoint-RH.svg

If the air temperature is say 25c, and the humidity i say 30%, the temperature at which water will condense is roughly 6c. If the humidity were say 90% the temperature would be about 23c. Thus if your boat inside temp is always above 6c, say 20c, on a sunny day of 30% humidity, there shall not be any condensation. But if the humidity suddenly rises to 90% and inside your boat if it is 20c, you shall.

Air can only hold a certain amount of water vapour at any given temperature. This is why ventilation is equally as important as the amount and type of insulation you have.

 

Steel hull isolation: alternatives to foam

I am totally against spray on PU foam since it makes a mess of the hull and cannot weld or cut on the hull when fitting out. Furthermore, should condensation forms behind the foam where adhesive to the hull was not complete, it is hid from view and a disaster in the making. Loose PU sheets fitted to hull and deck behind paneling makes more sense. Polystyrene has no place on a boat for a many obvious reasons.

However, my last steel boat built 2008/9 I used ceramic bead insulation paint (spinoff from NASA space program) on the inside of hull and deck. Thickly applied by brush and roller and having used white color, the hull is "neat" inside. Condensation does not bother this coating and should condensation formed inside the hull still it is able to drain to the bilge sump through its drain holes in stringers etc. Magic stuff and one can still cut and weld when doing fitting out if needed and just a matter of touching up the paintwork and applied fresh ceramic stuff over area.
Best part, it does not burn and cost less than spray-on PU foam.

 

Mike, could you explain this a bit more please.. I too have a steel hull which I will have to insulate soon..

For large quantities of condensation (a dripping tin roof) there has to be air circulation which continually brings humid air against the cold surface, but significant condensation can occur over time from air volume and temperature changes due to day/night variations. A good example of this is fogged up double glazing units which may only have a pin hole in the sealant. (I have seen them with several inches of water inside). Could this cause problems with voids behind Armaflex for example?

In any case, small gaps between insulation (or anything) adjacent to a steel hull surface seem to me to be a bad idea because if water does get in it will stay there for a long time.
I am working on a 20m steel yacht at the moment which has spray foam insulation, in places, rust has caused debonding in places and the gaps have become saturated. the wet areas all have extensive corrosion issues. True though, the boat is 30 years old and was not adequately painted inside when new. The water was comming from deck leaks from through bolted fittings.

Nick.

 

If you look at the thermal conductivity of:

Air = 0.024 W/m.K
Aluminium 250 W/m.K
Glass = 1.05 W/m.K
Steel = 43 W/m.K

So, what does this tell us? It says air is a poor conductor of heat, i.e. a good insulator. That’s why Double glazing works, the air gap provides the insulation. And some DG use different gases to improve further, like Argon 0.016, roughly twice as good as air.

So, if your double glazing is fogging up, the air gap is no longer sealed, in which case it cannot insulate correctly any more.

The same is true with insulation for fire. In engine rooms, heavy duty thermal insulation is in the order of 120kg/m^3. Compared to normal thermal of heat/cold which is nominally 30-40kg/m^3.

If you place these 120kg/m^3 firebatts over directly onto the steel or aluminium, it provides good insulation. If, however, you have an air gap, like double glazing, it significantly improves the thermal properties of the whole system. The temperature rise from the unexposed surface to the expose surface is altered sufficiently to improve the characteristics. Which is why almost all fire insulation systems are installed with an air gap between “it” and the material it is protecting. We use normally a 50-100mm gap.

So what does this mean for you?

Having adequate ventilation is very important, but so is extraction. No point pumping in new air if you do not scavenge the air, it must be fresh and hence recirculated to work properly.

If you find you are getting condensation, it means 1 of 2 things, you have insufficient insulation, i.e. the thermal barrier, or conductivity, of your insulation is poor, and/or you have poor ventilation and extraction.

Typical values of insulating materials, say Rockwool is in the order of 0.039 W/m.K, in other words, about twice that of air. If this barrier is broken or poor, then the exposed surface shall experience a high temperature gradient and thus, condense.

You are trying to protect the opposite face of the air immediately exposed to the metal, in your case the inside of the steel hull, from having a high temp gradient. If this surface air is prevented from experiencing a high temp gradient, the insulation is doing its job. (Whether that is Rockwool, air gap + Rockwool, or another) the rest is down to ventilation and extraction to maintain humidity levels.

 

The original poster asked if there was a alternative to foam to insulate a steel hull.

Why does it take so long to say ----NO!!!

 

Yes there is Frosty- see my previous post.

We painted a square meter of 3mm plate on the one side with this ceramic insulating paint and left the plate outside in the African summer sun (read ******* hot) with the ceramic facing down.
About midday you can cook your lunch on the plate and can barely touch it and the bottom with the magic ceramic stuff still cool to the touch with no trace of heat

 

The idea of foam is to insulate the inside of the boat. What you seem to be saying is it disperses the heat.

Ive not had your experience of many. I have however had a steel boat with foam that In lived aboard in the tropics, I could weld it to as I did many times to cut out unwanted problem dorado vents. You don't do long burns just short blast which you should to limit distortion anyway.