Gum blanket 2.0

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kard133

Full Member
Mar 20, 2010
657
47
Bristol
After seeing CoalCracker Bushcraft on YouTube using an American Civil War item called a Gum Blanket, which is a simple canvas sheet with a vulcanised rubber coating on one side, I thought to myself, that would make the idea groundsheet. It would be spark resistant, more abrasion resistant and quiter than plastic or a space blanket and not in the slightest bit slippy.

The only problem? Getting one from the US at a reasonable cost, they are available from various UK based Cutlers ( suppliers of historical war equipment for reenactors and collectors ) but only with a slit cut in the middle for use as a poncho.

So I researched a DIY route, and various sources cited Flexseal as an altenative to a factory applied rubber coating, however the only sources for this and similar compounds are also quite expensive, usually in the region of £40 and up for enough to coat a decent sized piece of canvas. Then it hit me, I have been using a product called Puraflex 40 to do everything from bonding door panels on the Defender to sealing guttering. According to the manufacturer, "Puraflex 40 is a high modulus, one component, polyurethane hybrid based sealant and adhesive that remains permanently elastic and has good adhesion to most substrates." Polyurethane is commonly used as a synthetic substitute for rubber, and this stuf can be had for approx £5 a tube. It took two tubes to coat the base of the GB 2.0.
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I tried it on a small piece of scrap canvas, and when it had dried it had the consistancy of, well, rubber. With the waterproof base sorted out, I thought about extra features. So I got a bigger piece of canvas, sewed it into a bag, so it could function as a browse bed, sleeping mat holder or even bivvy bag, and smeared the Puraflex over one side with a spreader knife from poundland, and left it to dry. If I do this again I will cover the uncoated side with paper and masking tape to prevent the smearing you can see in the picture.
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Finished weight for this is 1.7Kg (not for ultra lighters) 2m long and 80cm wide. It is completely waterproof on the base, I have had it sitting in the bathtub with tissue paper on the canvas side and a weight for three hours without leakage. It does not slip on the ground, makes no noise and is a tough as nails.

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The thought occurs to me that the Puraflex could be used to re-waterproof the base of 58 Pattern sleeping bags, tents, maybe even old ponchos, however I have not tested it on synthetic fibres. However I do know that it does not bond to polyethylene, like the grabber emergency space blanket, cheap poly tarps or realy cheap tent floors.

Here it is with a roll mat tucked inside, ala cheapskate Savotta FDF sleeping mat.
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Nice65

Full Member
Apr 16, 2009
5,390
1,868
W.Sussex
I reckon you ought to be making a few of those. I’d definitely have one.

My ex army microfibre towel cut down, hemmed, and pop studs fitted to fix to a sheet of waxed cotton canvas was an expensive labour of love. Great as sit mats or to dry the dogs and I’m happy I made a couple, but your invention is brilliant.
 
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