Craig. Measure the distance from the inside of the top of the tank to the bottom.
Each lengh of pipe will need to measure the same. Turn the tank on it's side with the filler hole in front of you. feed the pipes into the tank as you would put cigs into a packet. It will depend on where your filer hole is located, but when the pipes have reached the filler hole you will have to make space by pushing pipe lenghs
upwards in order to push the next lengh in. When you have filled the tank with pipe lenghs, you look into the filler hole and the inside of the tank will look like a honeycomb.
When you fill the tank with water, it's movement is resticted. It can only travel forwards, backwords or sideways within the confines of each individual pipe and the spaces in between.
when you go into a sharp lefthand bend your van wants to carry streight on. It has to follow the front wheels though and this pushes the vans weight to the right.
Without baffling the additional weight of water moving to the right would make the van unstable, and could cause it to overturn. The same would apply to stopping in an emergancy. The additional movement of water to the front would seriously impair breaking.
The difference baffling makes, is the same as the difference between a push and a punch. I can't think of any simpler way of putting it. The amount of pipe you would need depends on the size of tank and diametre of pipe.
Hope this helps. DAi