Crossing the board
The idea for this puzzle came from Peter Hendriks. Puzzle 103 on his site is the same problem but uses pentominoes exclusively. Helmut Postl’s spectacular solution of path length 49 is also shown on the site, below puzzle 104.
We wanted that our competition puzzle had something to do with the number 81.
So, you get one set of pentominoes and one set of tetrominoes.

Place these on a 9x9 board, such that the central square remains empty.

The configuration above shows a path of 45 steps.
The path leads from one side of the board to the opposite side, along the edges of the pentominoes and tetrominoes. The sides of the board cannot be used in the path. Furthermore, if you cut the board along the path, it will fall apart into exactly two pieces.
Find the longest possible path.
This Excel file will make searching for a solution a bit easier.
To download it click with the right mouse button and choose ‘Save target as ...’ to save this Excel file on your hard disk or diskette.

An help in searching for solutions is the program “FlatPoly2”. You can download it from the homepage of Aad van de Wetering, Driebruggen.