NexDog, If you have any specific questions that you are unsure of about the racks, feel free to ask. We'll see if we can break that language barrier.
Here is the foam that is applied to the PVC:
Then a coating of epoxy resin is applied over this. I don't know exactly what he used, maybe someone else can find a picture of some for you.
Then stick some sand or small rubble to the epoxy resin and you are all done.