Closed cell foam

[fisherman]

Finally got the suppplier to admit that two pot foam is only water proof on the outside skin where it meets the air, so in an enclosed space may be subject to soaking between the cells, so to speak. So, new deck in the IP 12ft, and have 48 2lt water bottles from lidl to stuff in the space under it, after glueing the tops on and semi-squashing for some. Here's hoping.

 

[coopec]

Fisherman

I bought 5 inch foam sheets to insulate my fridge/freezer and I know I must be extremely careful to ensure moisture does not come into contact with the foam otherwise the insulating properties will be stuffed. But if kept dry its' insulating properties are excellent.

Clive

 

[Malish]

Polyethylene foam is what you need for wet environments - great for canoeing for instance. Sadly does not come in two pot form to my knowledge. Two pot foam can act like a sponge. I have always wondered about this issue with double skinned 'unsinkable' boats

 

[coopec]

Polyethylene foam is what you need for wet environments. Sadly does not come in two pot form to my knowledge. Two pot foam can act like a sponge. I have always wondered about this issue with double skinned 'unsinkable' boats

Polyethylene foam is what is used for packaging and of course doesn't soak up water. To my knowledge it is no good for fridge/freezer insulation.

Now you mention it I'm sure when I watched a guy making surfboards he was using polyurethane (I guess it doesn't matter if your surfboard springs a leak though)

Clive

 

[macd]

Polyethylene foam is what is used for packaging and of course doesn't soak up water. To my knowledge it is no good for fridge/freezer insulation.

Now you mention it I'm sure when I watched a guy making surfboards he was using polyurethane (I guess it doesn't matter if your surfboard springs a leak though)

I'm not sure there's any particular reason why polyethylene foam couldn't be used for fridge insulation, although there are better products. It's particularly tough and can be load-bearing...perhaps handy if you like to walk on your fridge.

Don't know the precise technical reasons, but polyurethane foam works particularly well bonded to GRP and is offered as a recommended core material by specialist GRP suppliers. I've used the stuff: it makes a strikingly tough, light yet rigid structure even with just a single laminate of epoxy cloth.

 

[coopec]

I'm not sure there's any particular reason why polyethylene foam couldn't be used for fridge insulation, although there are better products. It's particularly tough and can be load-bearing...perhaps handy if you like to walk on your fridge.

Don't know the precise technical reasons, but polyurethane foam works particularly well bonded to GRP and is offered as a recommended core material by specialist GRP suppliers. I've used the stuff: it makes a strikingly tough, light yet rigid structure even with just a single laminate of epoxy cloth.

It's a long time ago that I was researching it but I am sure polyester resin will dissolve polyethylene foam . And I'm sure I found Polyethylene foam is an in-efficient insulation material but I can't find a reference to back that up at this stage.



No suggestion of insulation?


"The ASHRAE handbook recommends the following insulation materials for refrigeration applications: cellular glass, closed-cell phenolic, flexible elastomeric, polyisocyurante, and polystyrene. All of these materials have one property in common: all are closed-cell foam materials, which means they will have good WVT and low water absorption characteristics".

Clive.

https://sanded.com.au/pages/core-basics

 

[fisherman]

PU foam is routinely used for formers in grp work, top hat frames etc. I could just see ending up with a very heavy boat forthe kids to lug about. 48 water bottles at 17p per 2lts.

 

[macd]

View attachment 71553

No suggestion of insulation?

I suggest you read that again, Clive, specifically under 'Building'.

I've no idea whether polyethelene is soluble in polyester resin (or styrene), but suspect you may be thinking of polystyrene, which dissolves before your eyes. Not at all clear why that's relevant either way to it's role in insulation, anyway, unless laminating directly to it.

 

[coopec]

I suggest you read that again, Clive, specifically under 'Building'.

I've no idea whether polyethelene is soluble in polyester resin (or styrene), but suspect you may be thinking of polystyrene, which dissolves before your eyes. Not at all clear why that's relevant either way to it's role in insulation, anyway, unless laminating directly to it.

When I referred to insulation I was thinking in terms of fridge/freezer insulation not in terms of sisalation etc for roof cavities, walls etc.


" Is there a rigid PE foam ? Can't imagine the soft variety would be any use.

"Yes, there is.

Here we have a plate 1200 x 2200 x 20 mm 35 density for hulls and 120 density for parts of greater resistance as deck and transom.
The cells are closed, has good resistance to compression, shear and do not get old, but the problem is still on the chemical compatibility of the resin with the PE ".

Thanks,
Valter.f


"Polyester Resin on Polystyrene Foam? Of course its a no because of the styrene. But what if you wan...."


Clive

 

[fisherman]

Going round and round this, if I seal the deck down and grp overall as originally planned there will inevitably be pinholes round bilge keels etc, and with temperature changes will blow and suck until full of water. So, either fit a bung to the underdeck, or simply fill with bottles and leave open to the bilge sump. The latter is a lot less work.

 

[Seajet]

Fisherman,

I'm definitely with you on this one !

After some dodgy experiences with foam ' buoyancy ' over the years, my tender tanks and my chum's Osprey sailing dinghy I'm helping him sort out are stuffed full of multiple plastic water bottles, I reckon an Exocet hit would be a mild inconvenience.

 

[rogerthebodger]

Fisherman,

I'm definitely with you on this one !

After some dodgy experiences with foam ' buoyancy ' over the years, my tender tanks and my chum's Osprey sailing dinghy I'm helping him sort out are stuffed full of multiple plastic water bottles, I reckon an Exocet hit would be a mild inconvenience.

What I used in my mobo is 2 lit HDPE milk bottles (free) and square filled with one part foam and stuffed into all cavities making it almost unsinkable.