SEDAM (Société d'Etude et de Développement des Aéroglisseurs Marins / Society for
Design and Development of Marine Hovercraft) was a subsidiary of Société BERTIN, as
was the Société de l'Aérotrain. Established July 9, 1965, it was based at Marignane,
near Étang de Berre.
Here is its story…
Its first important project was the design and construction of two thirty tonnes hovercraft, the Naviplanes N.300.
Launched in December 1967 and March 1968, these vehicles were designed as cargo carrier (11 tonnes payload) with fore
and aft cargo ramps. In 1969 they were used as passenger ferries between Nice airport and the cities of Cannes,
Saint-Tropez, Monaco and San-Remo. For this service they were fitted with an enclosed cabin sitting 90 passengers and
named appropriately Baie des Anges and
La Croisette. Both craft were identical save that
Baie des Anges had retractable landing wheels while
La Croisette had air filled landing pads.
In 1971, SEDAM delivered a new hovercraft, the N.102. Smaller than the N.300, this craft could carry 12 passengers
in addition to two crew members. About half a dozen were sold. One was used for a time as a ferry between the sea
side resorts of Languedoc-Roussillon. Loire departmental authorities also tried one as a mean to bring tourists to
the Chateaux de la Loire. On the inaugural service, Murphy's law struck : the craft suffered an engine failure in
midstream with the Loire Prefect aboard !
In May 1971, the Gironde departmental authority buys the N.300 Baie des Anges.
This craft is used in the summer of 1972 as a ferry across the Gironde estuary between the communes of Pauillac,
Blaye and Lamarque. The craft cabin was modified carry 38 passengers and 4 cars. During this time N.300
La Croisette was evaluated by the French Navy in Toulon. No missions were
identified within that service that could be filled by the N.300.
These hovercraft were powered with helicopter gas turbines, as were most of the hovercraft of that period. Operating
costs were fairly high in relation to car and passenger ferries. This aspect, as well as prudence (reticence ?) with
regard to a means of transportation that was neither ship nor aeroplane, led to termination of the Naviplane services
and very few sales of the N.102.
In 1973, SEDAM, in reduced circumstances, obtains support from the State for its latest project, the 260 tonnes
N.500. This large ferry, to carry 56 cars, 5 buses and 400 passengers, has sufficient transport capacity
(payload vs speed) to compete economically with ferry boats. Two craft are ordered, one by the Gironde department,
the other by SNCF for Channel service.
In December 1975, SEDAM moves to Pauillac, in Gironde. Development of the N.500 takes place at a high pace,
directed by Paul GUIENNE, who had previously led the studies on the Aérotrain. A number of scale models are built
and tested and the N.300 La Croisette is used to evaluate the N.500 new
Two N.500 are thus built nearly simultaneously. The first one, the Côte d'Argent
has its first trial on the Gironde on April 19, 1977. The craft is out for two hours, running at 40-45 knot (74-83 km/h).
On May 3, 1977, as the craft is lifted on jacks and mechanics are working on the skirts, an exploding light bulb
set fire to a glue bucket. Fire takes hold underneath and the craft is completely destroyed.
The second N.500, the Ingénieur Jean Bertin is completed some time later.
It arrives in Boulogne after a trip of 850 miles (1570 km) carried out in 25 hours. At this time SEDAM has been
taken over by DUBIGEON-NORMANDIE shipyard.
The N.500 Ingénieur Jean Bertin began operation on July 5, 1978 on the
Boulogne-Dover and Calais-Dover services. Operated by SEASPEED, owned jointly by SNCF and BRITISH RAILWAYS, it was
then the largest hovercraft in the world, with its capacity of 400 passengers, 56 cars and 5 busses (two of the
SRN-4 already in service were stretched in 1976-77 so as to provide similar capacity. Their final weight went up to
300 tonnes giving them the title of «largest and heaviest» if not most efficient). At the time the N.500 was the fastest
ferry craft, with 74 knot (137 km/h) recorded between Boulogne and Dover.
Operation of the N.500 is not without its teething troubles. SNCF, arguing of low return on investment,
sells the N.500 to the British at the end of 1981. Some modifications are requested, which are carried out in
Boulogne in 1982 (modification to the skirts, increasing cushion area, and provision of lateral jets to increase
low speed manoeuvrability…).
N.500 is back in service March 18, 1983 operating as a SEASPEED craft, but operation are stopped definitely on
July 27. HOVERSPEED claims that it does not meet specifications and returns it to SNCF (one can surmise
that the N.500 was an embarrassment to SEASPEED as its operation and maintenance were different from that
of the SRN-4's).
Left on the Boulogne beach, the N.500 Ingénieur Jean Bertin was scrapped
in October 1985…
SEDAM disappeared in 1982, leaving at Pauillac the two N.300, four N.102 and various material…
An auction took place May 25, 1983. A scrap dealer from Bordeaux buys the four N.102, while the N.300
Baie des Anges is sold to a restaurant owner, and the N.300
La Croisette goes to a Paulliac scrap dealer. Plans to use the N.300
as a floating restaurant did not work out so the machine ended up as scrap, no other buyer being found.
Today, the Paulliac hangar (in perfect condition) is used by Baron Philippe de ROTHSCHILD as a wine distribution
centre. The concrete slip leading to the Gironde is still there, overrun with grass...