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[Edward Pinniger]

I know you can get some kind of foam filler substance for model boats (I think it's in spray can form, not sure though) which can be used to fill up empty spaces in the hull
to give buoyancy in the event of the model taking on water. I think I remember seeing some for sale at the Leamington/Warwickshire show last November, of course I didn't buy any!
Does anyone know what I mean, and are there any mail order suppliers of this in the UK?

Alternatively, would standard DIY/plumbing aerosol foam be safe to use in a wood and/or a styrene plastic hull respectively? (I have 2 hulls I need to add flotation foam to, one wood (sealed with Cascamite glue) and one plastic)

[alan colson]

You must be careful with this foam as it expands, it has been known to split a boat apart if you put to much in.
Alan

[andrewh]

Edward,

several answers - and an agreement with Alan
the word "expanding" means just that - but there are ways round it.

first safety  - alll uncured Polyurethane is poisonous - very and through the skin.  Do not wear latex gloves - use PVC or Nitrile (or polythene) gloves.

One-part foam is sold in all DIY stores (fills big holes, and similar names), it cures by being catalysed by water, so you lightly mist the inside of the space and huff it in carefully to about 1/3 the volume.  Do give it somewhere to expand to if it gets toooooooooooooooooooooooooooooooooo big!
remember that it sticks permanently to everything - protect floor, boat, yourself with cloth or newspaper.
Surface hard in about an hour, hard right thru in 24 hours

2-part foam comes from good boat suppliers and alll fibreglass suppliers - see CFS, who have good instructions with it
http://www.cfsnet.co.uk/acatalog/CFS_Catalogue__2_Part_Polyurethane_Foam_Liquid_415.html
It is far more controllable and predictable than 1-part, and you can keep the rest of the tin for future use

Suggestion (if you are thinking of doing your cutty sark or similar)
insert plastic bag into the area you are aiming to fill;  blow into it so it expands into the space)
Put the ship with this area at the bottom (so the bag fills upwards)
Put in foam to fill about 1/4 of the bag - leave for an hour
never close the open end of the bag
repeat as necessary (if you use 1-part foam you will have to take off the nozzle and clean with acetone or cellulose thinners so that it works later)
when hard chop off the foam and bit of bag you don't need.

This stops the foam bonding to everything in the ship - if you want this for integrity reasons (this is what they do with nail-sick roofs) stick a temporary bulkhead where you want the foam to stop with say a 2 inch hole - tape a plastic bag round the hole - or a big paper funnel so it has sonewhere harmless to expand into.

If I can help more, just ask
BTW - for small volumes I fill with polyurethane woodglue - mixed 1:1 with water - it foams well but not with overwhelming violence and will fille, say a forepeak (and of course bonds everything together)

andrew

[andyn]

Pool noodles! £1.50 each at a good seaside near you...

[craftysod]

 good idea andy

[alan colson]

Having just seen the photo placed by andy it crossed my mind that foam pipe lagging may be a answer.
Alan

[andyn]

Yup, just as good, but it's got an 'ole in the middle innit

[Edward Pinniger]

Thanks to all for the advice!
It sounds like ordinary DIY one-part foam would NOT be a good idea for the wooden Cutty Sark hull. Even if it doesn't cause any visible damage when expanding, it's very likely to split the seams between the hull planks.

The reason I wanted to use foam for this model is that the areas I want to fill are small and awkwardly-shaped compartments (the hull is divided up by lateral bulkheads) and access to some of them is limited. Expanded polystyrene blocks (what I'd normally use) would be difficult to fit in so that they occupy all the space.  The only other possibility I could think of was to use packaging bubble wrap packed tightly into the compartments, but I'm not sure if this would give enough buoyancy.

Roughly how much buoyancy material (such as the foam tubing andyn posted) or air (from bubblewrap) would be needed to keep a model weighing about 2.5-3kg afloat? The CFS foam description says "1 cubic foot will support 27kg in water". I'd estimate theres about 1/3 of a cubic foot in the Cutty Sark hull excluding the compartments used for ballast and radio gear.

I may buy some of the CFS foam, as I have a couple of other future projects (such as the Billing Boats lake steamer "Bohuslan") which will need similar treatment due to insufficient space in the hull for polystyrene blocks. Alternatively, what brand of polyurethane wood glue would you recommend?

The other boat mentioned is my 1/48 USCG patrol boat - in this case, as the deck is completely removable and the hull has plenty of space, I'll just use polystyrene offcuts and/or packaging air bags for buoyancy.

[StarLocAdhesives/FiveStar]

You can get expanded polystyrene beads for use in making beanbags , just pour it in and add a bit of glue to the end layer to form a glue and polystyrene bead bulkhead, it pours like water to fill every gap inside, you can get the beads on ebay and most craft shops