Wil Tower
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The Wil Tower is a 37-m-high wooden observation tower which was built in 2006 in the forest of Wil in Switzerland. From the slender wooden construction only the uppermost observation deck is visible from a distance.
[edit] Construction
The plan of the tower is an isosceles triangle with a side length of 12 m at the base. This reduces its cross section up to a height of 17 m and increases than its cross section until a height of 34 m again to the same value as on the ground.
The traffic and wind loads are carryed by more than three X shaped props. A X consists of two upper and two lower round timbers, which are connected at the height of the middle platform with each other. The loads from the roof are carried by three-W-shaped frameworks in the outside props.
In the core of the tower there is a double spiral staircase, which spiral up the whole height. The stair case has two complete stair runs independent from each other with a width of 2.50-m. After 18 steps there is a inter podest. The steps consisting of massive wood in the format 18 x 36 cm were lined up concentric in a metal spindle and screwed together.
The observation deck 34 metres above ground is roofed. For the construction only wood from surrounding forests were used. The largest part of the wood, namely the round timbers consisting of Douglas firs and the stairway steps of silver fir were cut in spring, 2005 and naturally dried.
