How we built Brinkvaken
We have a wooden frame that we mounted on the ice. On it we have a lid consisting of a frame that encloses two Styrofoam plates (each 120x60x10cm). One problem we have is that the water level varies - can be from about -50 to +50 or more, so it does not work with a fixed ladder. Therefore, we have a loose ladder, which we store under the ice to avoid ice formation on it.
At one point, water ran over our frame (120x21mm + 45x45mm), so we had to build on with an additional frame (45x120mm).
One problem we have seen is that some people who use the watch do not scrape the edges from ice, which means that the lid does not close tightly against the frame. Then the cold comes in and thick ice can grow on the wake. Therefore, we have now put up a sign with instructions and also made an instructional film. The film also gives a clue about the construction.
More will come...