Mancunian airman Posted February 27, 2017 Share Posted February 27, 2017 (edited) Hi I am in the process of building some air-raid blast shelters and need some suitable material to represent 'earth' banked up against the wall(s). I have tried wood shaped dowelling but its to uniform, not the same width front and sides, even tried polystrene but it makes such a mess. Years a go I remember a friend user expanding foam to support/strengthen vac form models but I cant recall if it was pliable to work with or even to shape when dry. cant remember if it comes in a tube or spray can which would make it difficult to apply as I only need to be at a height of 12mm I have quite a few to cover/surround so really need something to work with that's not to expensive or involved . . . any help/guidance appreciated Ian Edited February 27, 2017 by Mancunian airman Changed the photo Link to comment Share on other sites More sharing options...
Black Knight Posted February 27, 2017 Share Posted February 27, 2017 Polyurethane Foam usually comes in spray cans. Its available as two-part liquids in really big buckets for professional use. Spray cans cost from £3.99 upwards It needs dampness to expand. It'll expand from 10x to 100x, depending on make and level of humidity. When set the outside is smooth. You can cut it with any craft knife. Its a bit like ploystyrene but more solid, it doesn't break up as easily. The interior has a lot of small air bubble holes; not a problem, it adds to the look of ground work Because of its unpredictability in the size and shape of the expansion i would tack down a sheet of plastic, spray with water, spray a length of the foam and immediately spray a fine mist of water over the foam. In just a few minutes you'd have long tube shaped lengths which you can attack with a craft knife, shaping bits to fit your walls. I find UHU glue best for sticking it down 2 Link to comment Share on other sites More sharing options...
bhouse Posted February 27, 2017 Share Posted February 27, 2017 On the subject of expanding foam, I was sent this educational tale many years ago. Apologies if you've seen it before. A friend of mine once built a canoe. He spent a long time on it and it was a work of art. Almost the final phase was to fill both ends with polyurethane expanding foam. He duly ordered the bits from Mr Glasplies (an excellent purveyor of all things fibreglass) and it arrived in two packs covered with appropriately dire warnings about expansion ratios and some very good notes on how to use it. Unfortunately he had a degree, worse still two of them. One was in Chemistry, so the instructions got thrown away and the other in something mathematical because in a few minutes he was merrily calculating the volume of his craft to many decimal places and the guidelines got binned as well. He propped the canoe up on one end, got a huge tin, carefully measured the calculated amounts of glop, mixed them and quickly poured the mixture in the end of the canoe (The two pack expands very rapidly). I arrived as he was completing this and I looked in to see the end chamber over half full of something Cawdors Witches would have been proud of. Two thing occurred to me, one was the label which said in big letters: "Caution - expansion ration 50:1" (or something similar) and the other that the now empty tins said "approximately enough for 20 small craft" Any comment was drowned out by a sea of yellow brown foam suddenly pouring out of the middle of the canoe and the end of the canoe bursting open. My friend screamed and leapt at his pride and joy which was knocked to the ground as he started trying to bale handfuls of this stuff out with his hands. Knocking the craft over allowed the still liquid and not yet fully expanded foam to flow to the other end of the canoe where it expanded and shattered that end as well. A few seconds later and we had a canoe with two exploded ends, a mountain of solid foam about 4ft high growing out of the middle, and a chemist firmly embedded up to his armpits in it. At this stage he discovered the reaction was exothermic and his hands and arms were getting very hot indeed. Running about in small circles in a confined space while glued to the remains of a fairly large canoe proved ineffective so he resorted to screaming a bit instead. Fortunately a Kukri was to hand so I attacked the foam around his hands with some enthusiasm. The process was hindered by the noise he was making and the fact he was trying to escape while still attached to the canoe. Eventually I managed to hack out a lump of foam still including most of his arms and hands. Unfortunately my tears of laughter were not helping as they accelerated the foam setting. Seeking medical help was obviously out of the question, the embarrassment of having to explain his occupation (Chief Research Chemist at a major petrochemical organisation) would simply never have been lived down. Several hours and much acrimony later we had removed sufficient foam (and much hair) to allow him to move again. However he still looked something like a failed audition for Quasimodo with red burns on his arms and expanded blobs of foam sticking everywhere. My comment that the scalding simple made the hairs the foam was sticking to come out easier was not met with the enthusiasm I felt it deserved. I forgot to add that in retrospect rather unwisely he had set out to do this deed in the hallway of his house (the only place he later explained with sufficient headroom for the canoe - achieved by poking it up the stairwell. Having extricated him we now were faced with the problem of a canoe construction kit embedded in a still gurgling block of foam which was now irrevocably bonded to the hall and stairs carpet as well as several banister rails and quite a lot of wallpaper. At this point his wife and her mother came back from shopping...... Oh yes - and he had been wearing the pullover Mum in law had knitted him for his birthday the week before. 13 Link to comment Share on other sites More sharing options...
spruecutter96 Posted March 1, 2017 Share Posted March 1, 2017 As a suggestion.... DAS clay? I think I've got the name right - it's either DAS or DAZ. If memory serves me right, a half-kilo block can be had on E-Bay for around £6.00 (ex-delivery). I would have thought it would be a much more practical solution than expanding-foam. Good Luck, my friend. Chris. Link to comment Share on other sites More sharing options...
sinnerboy Posted March 1, 2017 Share Posted March 1, 2017 bhouse I wouldn't use expanding foam, just used some to fill some gaps between wall & floorboards before replacing skirting, very unpredictable & very messy if it goes in the wrong place. As Spruecutter suggests DAS or I'd probably use Plaster of Paris or household filler. Link to comment Share on other sites More sharing options...
Circloy Posted March 1, 2017 Share Posted March 1, 2017 Any building sites in the area? If so why not see if you can blag some off cuts of the polystyrene insulation blocks most new builds are using. http://hobby.uk.com/materials/polystyrene-foam/styrofoam-blue-1.html Link to comment Share on other sites More sharing options...
Bangor Lad Posted March 1, 2017 Share Posted March 1, 2017 Have you come across florists foam? Sold under the name Oasis it can be cut with a bread knife and pressed into shape. Seal the surface with dilute pva and you're good to go. 1 Link to comment Share on other sites More sharing options...
Mancunian airman Posted March 1, 2017 Author Share Posted March 1, 2017 32 minutes ago, Bangor Lad said: Have you come across florists foam? Sold under the name Oasis it can be cut with a bread knife and pressed into shape. Seal the surface with dilute pva and you're good to go. Thanks for that Bangor Lad just ordered 2 bricks from that well known auction site, but at a fixed price Thats the benefit of asking on this site, so many people come up with solutions and answers to the many issues that are raised. Thanks gentlemen for your input, the outcome is far from over until it done . . . Ian 1 Link to comment Share on other sites More sharing options...
Mancunian airman Posted March 1, 2017 Author Share Posted March 1, 2017 48 minutes ago, Circloy said: Any building sites in the area? If so why not see if you can blag some off cuts of the polystyrene insulation blocks most new builds are using. http://hobby.uk.com/materials/polystyrene-foam/styrofoam-blue-1.html Just looked at the Link and it is rather expensive NEW so as you say, go and blag some from a building site if all else fails Ian Link to comment Share on other sites More sharing options...
Dave Fleming Posted March 2, 2017 Share Posted March 2, 2017 You can pick up cheap Oasis in Poundland or similar Link to comment Share on other sites More sharing options...
Dave Fleming Posted March 2, 2017 Share Posted March 2, 2017 On 27/02/2017 at 11:06 PM, bhouse said: On the subject of expanding foam, I was sent this educational tale many years ago. Apologies if you've seen it before. A friend of mine once built a canoe. He spent a long time on it and it was a work of art. Almost the final phase was to fill both ends with polyurethane expanding foam. I knew what was coming from about there! I remember a friend using an aerosol it to fill the fusleage of a large vacform to give it rigidity before adding the wings. He assemble dthe fuselage, then squirted foam in from a hole in the wing root. You can guess what hapened next. He got a wonderful foamy 3D exploded diagram of an aeroplane! 1 Link to comment Share on other sites More sharing options...
Circloy Posted March 2, 2017 Share Posted March 2, 2017 22 hours ago, Circloy said: Any building sites in the area? If so why not see if you can blag some off cuts of the polystyrene insulation blocks most new builds are using. http://hobby.uk.com/materials/polystyrene-foam/styrofoam-blue-1.html 21 hours ago, Mancunian airman said: Just looked at the Link and it is rather expensive NEW so as you say, go and blag some from a building site if all else fails Ian Bad example (especially as it doesn't indicate the sheet size) chosen quickly just to illustrate the product. Can get a full 2.4m x 1.2 m sheet (8ft x 4 ft approx) for similar price at DIY outlets. Link to comment Share on other sites More sharing options...
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