Leakage of Trintella 3 and 3a windows

How can I prevent leakage at the portholes of my Trintella 3 and 3a? Answer: Especially the sliding windows are a cause of leakage. These windows slide on a canvas cloth. Given time this canvas starts to desintegrate causing the leakage. Usually there is no leakage between the GRP superstructure and aluminium window frames. It's a quite difficult repair as the windowframes have to be taken apart. usually the rubbers are hard to remove, which can cause the frames to be bent during the operation. Worst case scenario is damage to the anodic protection. If that's the case the best solution is replacement of the windows.