Complex sentence: Two were located on the forecastle, two on the after funnel deck, and the fifth in the quarterdeck: all five were hidden by the structure of the ship until they were raised clear on hydraulic platforms.
Split into simpler sentences: Two were located on the forecastle, two on the after funnel deck, and the fifth in the quarterdeck. All five were hidden by the structure of the ship until they were raised clear on hydraulic platforms.