\ said:
Thanks the tarps are peices of paper kithen roll cut out ,draped over wheels before painting then aply watered white wood glue painted on to paper with a brush till it goes soft and then you can shape it over wheels and add creases ,a few more coats and when dry carfuly remove .
I noted the tarps too. Often they are made too thick and don't drape with sharp creases. They are very realistic (although the shelter one looks relatively thick, more like an animal skin. Perhaps it was - I wonder what they used in WW1 for large tarps.)
Also, the sand you used: I recently experimented with attaching sprinkled Silver Sand (from a garden centre) on to fresh PVA glue. It stuck alright but when dry there were many white spots. After noting that Silver Sand probably comes from a beach and was contaminated with salt, I washed it and the problem disappeared. (Although salty sand is not the best thing for a garden!)
Here's what Google says:
"The Word Tarpaulin is a *compound* word made from
tar
and
palling
and refers to a tarred canvas pall. This refered to a tarred canvas (canvas that had been soaked in tar) pall (pall refers to a stiffened cloth or sheet) and was used on ships to cover loads or cargo. This was why the English sailor was known as a Jack Tar. The association of the tarpaulin with the ship resulted in sailors first being called tarpaulins, which over time was shortened to tars. This term was used to refer to sailors or the Merchant or Royal Navy."
So in WW! a tarp would have been made of canvas soaked in tar, so a large one would have been quite stiff (although it would have been sticky in the desert!). (It is amazing where scale modelling takes you!)