I scored about 60 meters of 40mm PVC pipe for Free from my brother who is a plumber, also found that 40mm copper pipe fits neatly inside so I can make short dowels with that which will fit snug. (Copper pipe was free too but you don't need much, the connector dowels I cut were 150mm long).
Also, I went to the hardware and bought 30meters of flexible drainage pipe for about $30. It's 50mm diameter which allows you to make the long radius bends for the fast sweepers. The copper pipe dowels fit inside perfect to connect it. As it has ridges you can cut the flex pipe in the low spot for a more flush connection that won't rip apart your bodies when you impact it.
Now just gotta make some plugs to fill the pipes with sand.
Rok Rc Tuning Parts for large scale off-road racing. Rok Solid parts for Rok Hard racers.