The
Joffre-class carriers were
long between perpendiculars and long overall. They had a
beam of at the
waterline and at the
flight deck. The ships displaced at
standard load and at
full load, which gave them a
draft of . The based the propulsion machinery of the
Joffres on that used in the
light cruiser , albeit with eight Indret
water-tube boilers rather than four. The ships were fitted with two
Parsons geared
steam turbines, each driving one
propeller shaft using steam provided by the boilers at a working pressure of and a temperature of . The turbines were rated at a total of and were designed to give a speed of . The carriers retained the
unit system of machinery with each
boiler room supplying steam to the
engine room aft of it so that one hit could not completely immobilize the ships. The boiler uptakes were trunked into a single
funnel integrated into the
island on the
starboard side of the
flight deck. The ships were designed to carry enough
fuel oil to give them a range of at .
Aviation facilities The ships' flight deck was offset to the left from the
centerline. This helped to compensate for the weight of the very large island and allowed it to have a continuous width of . The deck itself was in thickness. The carriers were intended to be fitted with an aircraft-handling
crane near the
stern, below the flight deck that were strong enough to lift a
seaplane aboard. They had a fuel capacity of approximately of
aviation gasoline. The optimized the design of the
Joffre class for "double-ended" operations, where aircraft could land and take off over both the
bow and stern, so that battle damage to the flight deck would not necessarily end flight operations. Like
Béarn, the
Joffres had their
arresting gear amidships, abreast the island, although the number of wires was increased to nine. While the amidships position minimized the ships'
pitching in high seas, the air turbulence generated by the island was at its worst amidships. Based on trials aboard
Béarn in 1935, collapsible landing signals were positioned on the centerline of the flight deck amid the arresting wires, facing in both directions. The flight deck was not provided with any
crash barriers, so the American practice of keeping aircraft on the deck during landing operations was not possible. The two hydraulically powered
elevators that transferred aircraft between the flight deck and the upper
hangar were positioned at the ends of the flight deck, allowing aircraft landing amidships to taxi forward to the elevators and rapidly clear the flight deck. Both elevators were configured to be used by aircraft with their wings still spread, eliminating the requirement to fold the wings before using the elevators that slowed down
Béarns flight operations. The forward elevator was roughly T-shaped and measured long and wide; the large elevator well so close to the bow weakened the ships' structure so the designers minimized the size of the well in the hangar deck by only seating the central section in the deck while the outer areas of the elevator rested on top of the deck, requiring a small ramp to move on or off the elevator. The rear elevator was outside the hangar and only its forward end reached the flight deck. Although it only measured , its position allowed it to strike down aircraft regardless of size. The carriers were designed with two hangar decks, the upper of which measured with a height of . A space long below the flight deck and between the upper hangar and the rear elevator allowed aircraft to warm up their engines before moving to the flight deck. A single
fire curtain amidships could be used to divide the hangar. It was the only one that could be used for aircraft operations as the lower hangars were dedicated to workshops and aircraft assembly and storage facilities. The rear lower hangar was in size and had a height of . A elevator at the forward end of this hangar allowed aircraft to be transferred between the hangars. This elevator was offset to
starboard to allow for a passageway to the lower hangar annex that measured . This annex, presumably dedicated to spare parts, was offset to port to make room for the boiler uptakes and ventilation ducting of the forward engine and fire rooms. Based on their decade of experience with
Béarn and frequent exercises with the British
Fleet Air Arm during the 1930s, the (French Naval Aviation) believed that air operations would be continuous, with small numbers of aircraft taking off or landing. This required multi-role aircraft, able to switch between missions as the tactical situation dictated. The
Joffre-class carriers were designed with an air group of 40 aircraft, 15 single-engined
fighters and 25 twin-engined aircraft capable of long-range reconnaissance, bombing and
torpedo attacks. In 1939 the Navy ordered 120 Dewoitine D.790 fighters, a navalized variant of the
Dewoitine D.520, although no aircraft was completed before the Armistice cancelled further work. It issued the A47 specification in 1937 for attack aircraft to equip the carriers and ordered two prototypes each of the
SNCAO CAO.600 and the
Dewoitine D.750 in 1939. The issued the updated A80 specification that same year for a faster aircraft and selected the Bréguet Bre.810, a navalized version of the
Bréguet Bre.693, but the prototype was not completed before the Armistice.
Armament, fire control and armor The carriers' primary armament consisted of eight 45-
caliber Canon de Mle 1932 dual-purpose guns in four twin-
gun turrets positioned fore and aft of the island in
superfiring pairs. The guns fired a
armor-piercing shell at a
muzzle velocity of . This gave them a range of at an
elevation of +45°. Their mounts had a maximum elevation of +75° and the guns had a
rate of fire of about 10
rounds per minute. Light anti-aircraft defense was provided by eight 48-caliber
Canon de Mle 1935 guns in four twin-gun ACAD mounts on the island, and twenty-eight
Hotchkiss Mitrailleuse de Mle 1929 machine guns in seven quadruple mounts. There were two mounts on the
forecastle, two on the stern and a pair on the island. The remaining mount was on the port side underneath the flight deck overhang. The 37 mm guns were fully
automatic and had a theoretical rate of fire of 165 rounds per minute. They had a range of with their shells which were fired at a muzzle velocity of . Their mounts had an elevation range of -10° to +85°. The 13.2 mm machine guns had an effective range of . The 130 mm guns were controlled by a pair of superimposed
directors on the top of a short tower on the roof of the island. The upper director was equipped with a
rangefinder for anti-aircraft defense and the lower with a one for surface engagements. Each of the upper 130 mm turrets was fitted with a rotating 5-meter rangefinder as a backup to the directors. A director equipped with a rangefinder remotely controlled each ACAD mount. The two forward directors were superimposed on the roof of the island while the two after directors were side-by-side aft of the director tower. The
waterline armor belt of the
Joffre-class ships covered the middle of the hull, from the forward
magazines to the aft aviation gasoline tank. It was thick and had a height of about from the main deck to below the waterline. It formed an
armored citadel with transverse
bulkheads at its ends. The armored deck was 70 mm thick over the magazines and gasoline tanks, but reduced to amidships over the machinery compartments. The
torpedo belt ranged in thickness from abreast the propulsion machinery spaces, but thinned to abreast the magazines. The steering compartment was fitted with 26-millimeter armor plates. The 130 mm directors, turrets, their hoists, and their upper handling rooms were protected by of armor, as were the command spaces in the island. For protection against fire, the aviation gasoline tanks were surrounded by either empty compartments with fire-resistant insulation or inert gases on all sides. == Ships ==