Data published in 2011 on unconventional interceptors (the Double Interceptors System and the Split Interceptors) obtained in the towing tank of the Dipartimento di Ingegneria Navale of Naples, point out the high potentiality of these devices.

This paper shows data of new tests, performed on D.I.S. and S.I. fitted on three different hull forms. The tests have confirmed the high resistance reductions and the extension of the high efficiency speed range of the hulls.

A 20 deg deadrise prismatic and two warped hulls have been tested to evaluate the effects of three different amount of twist of the bottom on the interceptor's efficiency.

The warped models are characterized also by different L/B ratios to detect the border effects on the high pressure zone due to the forward device of the D.I.S. .

Tests have been performed in the speed range 1.3 < Fn_Ñ < 3.0. In all test conditions it has been realized Rn > 5×10⁶.

On models fitted with the D.I.S. , longitudinal instability phenomena have been observed at lower speed than the typical ones expected on bare hulls due to purposing. This instability has been related to the ventilation's level downstream the forward device.

The experimental procedure has been improved to study in dept these dynamic instability phenomena.