Expanding foam

[Rich Griff 2Participant @richgriff2]

Expanding foam

[Rich Griff 2Participant @richgriff2]

I have been told that the common cheapo aerosol expanding foam can cause issues with weaker joints/ glue lines once the foam has gone off, an subject to very sunny days and temperatures, forcing joints/glue lines apart.

Is there a relatively cheap expanding foam aerosol that is temperature stable, or an alternative please.

I need to add bouancy ( seal out/displace water ) from sealed air bouancy chambers in a polystyrene double skinned boat.

Micro bubbles ?

A cheapo spray foam type material would be preferable…

Any suggestions …?

[Chris EParticipant @chrise]

The examples that I am aware of are not fully closed cell. If they get wet they absorb water & get heavier .

They also really do want to keep expanding and can break your model doing so.

I believe that you need something like this:

https://www.ecfibreglasssupplies.co.uk/product/polyurethane-foam-liquid

Edited By Chris E on 10/07/2021 21:34:20

[Colin BishopModerator @colinbishop34627]

Stay away from expanding foam for models. It rarely ends well. There are plenty of more stable options. But if you have built the boat properly then it won't sink anyway.

Colin

[Richard SimpsonParticipant @richardsimpson88330]

The challenge with expanding foam is that it can cure at the open point of the space first, effectively sealing it, then the further expansion of the foam puts pressure on the internal surfaces of the space. Potentially leading to cracks or even failure.

Any form of closed cell sponge is as good as anything, which can be packed into a space and should never absorb moisture. It can also be removed easily for checking behind it and possible future repairs.

Just put "Closed cell foam" into Amazon, you can buy it in sheets or as a roll with an adhesive backing for such applications as door sealing.

[ashley needhamParticipant @ashleyneedham69188]

If you have a sealed buoyancy chamber it surely needs nothing else it it?? Putting anything in a sealed chamber only makes it heavier.

If you think water might get into your sealed chamber then perhaps it is not really a sealed chamber??

Ordinary expanded polystyrene is the way to go if you have doubts on the efficacy of your sealed chambers. Only sufficient is needed to stop the boat from sinking.

Ashley

[Rich Griff 2Participant @richgriff2]

Thanks for the replies, I will check out the firms and places mentioned.

 

The boat was not made by me, but when I cleaned it yesterday water was seen "appearing" inside the hull, a double skinned affair.

 

Some of the seams between the inner and outer skins appear not to be sealed well enough which is why water made its way into the "void".

 

I will have to research liquid glues and sealers for polystyrene and flow some into the joints. Cyno is not fully waterproof I have read somewhere.

 

If it takes in water during a carefully cleaning with water, it will take in water when it's scooting about on the water. The "deck cover" needs some attention also as I recon water could/will end up inside the open space where the motor/batteries/radio gear lives.

 

All available space inside the hull open space will be filled with white expanded polystyrene "packaging waste" which is normal practise for me.

 

The Titanic sank.

Edited By Rich Griff 1 on 11/07/2021 09:34:56

[Malcolm FraryParticipant @malcolmfrary95515]

Apart from its knack of absorbing water, either from contact with liquid or just getting it from damp air (and boats operate in damp conditions), most users use far too much, not really allowing for it expending as much as it can.

Expanded polystyrene packing or similar, hacked to shape works well. Or similar packing noodles. Or, if you can forego the joy of popping them, bubble wrap sheets.

I imagine that the last thing wanted in a buoyancy chamber is soggy ballast that cannot be extracted and/or dried.

[Richard SimpsonParticipant @richardsimpson88330]

Check out Captain Tolley's Creeping Crack Cure:

Captain Tolley's

I recently used it to seal a clinker built hull and was very pleased with the results.

Followed by a couple of coats of Eze Kote:

Eze-Kote

Thanks to recommendations on here!

[ashley needhamParticipant @ashleyneedham69188]

The only time I have used expanding foam was when I had a water issue in the carpet carrier (as the deck just fitted over the hull and water was coming in the bow).

SO I squirted foam in the front compartment….BUT this didn’t matter as the top was of course open, so I left it a few days and then trimmed it flush. Water still gets under the fore deck but runs off a bit further on off t( foam.

Absolutely would use it for anything enclosed.

Ashley

[Former MemberParticipant @formermember67585]

[This posting has been removed]

[Richard SimpsonParticipant @richardsimpson88330]

Pool noodles are simply tubes of "Closed Cell Foam" as I mentioned above.

[Former MemberParticipant @formermember67585]

[This posting has been removed]

[Rich Griff 2Participant @richgriff2]

Thanks again for the replies…

So the foam builders use to "hold window frames" in place is not water proof and acts like a sponge if the skin is broken ?

That would explain a lot !

This double skinned boat, if water gets into the void it's not a bouancy tank but a liability.

Will get getting the captain Tolley stuff and sealing all the edges. I will drill some holes on the inner skin so the seams can be sealed from the inside as well.

That way, no water will get in, but just in case, I will have some drain holes as well.

Next stage will be a better seal/coaming for the "lid" bit. Maybe a further lid for the open access area, with the manufacturers lid over that.

The lake is choppy, this boat will be relatively fast, and as is will take in water, so mods need to be done before it goes on the water.

[Trevor HollowayParticipant @trevorholloway99134]

Camping bed rolls are also closed cell and easy to cut to shape to fit in tight spaces.

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