The New Russian Circular Ironclad ' Popoffka Novgorod ' The chief advantage of the circular form ( designed by Vice Admiral A. A. Popoff ) is that owing to the greater displacement in comparison with the weight of hull , it enables vessels thus built to carry heavier armour and weightier guns . The armour plates are 9 inches thick , and are ' backed ' with Channel iron to the amount of two inches . The guns , two in number , are 11 inch bore . 1875