I just found it !!!

type NE Serpentine
dictionary NE_Serpentine ; Serpentine
category siege
class missile
voice_type Light
banner faction main_missile
banner holy crusade
soldier NE_Serpentine_Crew, 16, 2, 1
engine serpentine
attributes sea_faring, hardy, can_withdraw, gunpowder_unit, cannon, artillery
formation 1.5, 1.5, 3, 3, 3, square
stat_health 1, 0
stat_pri 7, 3, no, 0, 0, melee, artillery_gunpowder, piercing, knife, 25, 1.8
;stat_pri_ex 0, 0, 0
stat_pri_attr no
stat_sec 65, 3, serpentine_shot, 450, 36, siege_missile, artillery_gunpowder, blunt, none, 25, 1
;stat_sec_ex 0, 0, 0
stat_sec_attr ap, bp, launching
stat_pri_armour 2, 5, 0, leather
;stat_armour_ex 2, 0, 0, 0, 5, 0, 0, leather
stat_sec_armour 0, 0, flesh
stat_heat 1
stat_ground 0, 0, 0, 0
stat_mental 9, disciplined, highly_trained
stat_charge_dist 30
stat_fire_delay 0
stat_food 60, 300
stat_cost 1, 870, 150, 60, 140, 870, 1, 260
armour_ug_levels 1
armour_ug_models NE_Serpentine_Crew
ownership spain, france, hre, denmark
era 1 spain ............................> add this line
era 2 spain, france
;unit_info 7, 0, 7