Sealion was impossible, even with the Royal Airforce defeated.
A frontal attack against a defence line, on too narrow a front, with no good prospect of suprise, with insfficient forces reinforced only in dribblets'
Field Marshal von Brauchitsch, commenting on 'Operation Sealion' in September 1940.
I think that sums it up really. Even German Army high command considered the plans for Operation Sealion the highest folly.
The German Navy wanted landings on a narrow front. It couldn't guarentee control of the chanel for more than a few days. The Army demanded a broad front landing, but didn't have the necessary sealift capacity to support it, without converting half the Kriegsmarine into troopships.
Halder (one of the German Army Chiefs of Staff) put it nicely in a August 14 memo to the Navy, referring to their desire for narrow front landings; "I might as well put the troops through a sausage machine"
Schniewind, the other Army Chief of Staff, noted that "the airborne troops can influence neither the weather or the sea; they cannot prevent the destruction and incapacitation of the few harours, nor hold off the enemy fleet, or even a small part of it' In the words of the German high command, Airborne troops could be used but they would not be of much influence to the main landings.
Initial German calculations for Sealion showed that they would need between 2 to 3 days to put ashore just the first wave of 13 divisions. The final August draft plan for Sealion reduced this to 9 divisions, with 2 airborne divisions supporting, but stretched the length of the landings to 9 days for just the first wave. To land the frontline elements of the 40 divisions that the Army requireded, at a minimum, to conquer England, it would take an estimated total of 40 days, without taking into account allowances for heavy or specalist equipment or logistic formations! There is little doubt that the Royal Navy would of done everything in its power to disrupt this further.
To support the landings the Germany Navy had made no commitments for artillery support, its primary role was to keep open a clear sea-lane between Calais and the Dover area. Two old 15 inch monitors were considered but dropped as it would take too long to refit them with sufficient anti-aircraft armament and anti-submarine capability. Artillery support, for the planned 50 mile wide landing in the inital phase, would be supported by just 27 costal patrol craft, fitted with 3 inch howitlers and 37mm cannon. Compare that to the support for the Allied landings in Italy, Sicily, North Africa and France and you can see just how deficient it was.
The German High Command planned to capture the ports of Folkstone on D+1 and Dover slightly later. Both were expected to have been damaged by British forces once landings started. The estimates of supply requirements of an infantry division were around 300-350 tons a day. Inital calculations were tah Folkstone could handle 150 tons a day, building to a maximum of 600 per day by D+8. Dover would have slightly higher capacity of 800 tons per day.
Considering that the initial wave was 9 infantry divisons and 2 airborne divisions then they would need a minimum of 3,300 tons of stroes, rations, ammunitionand other necessities every day. But Dover and Folkstone together could only supply 1400 tons per day, or less than one third of the suplies necessary to supply just the initial wave of troops. Siply put, even with the capture of two ports intact, Germany could support a mere 4 divisions.
At best Germany could of put across 3-4 divisons in early July and kept them supported and supplied with air and sea-lift capacity. Reinforcements of men could of been brought in IF airfields in the south had been captured IF the RAF had been completely defeated. Supplies and heavy equipment could of crossed the channel in sufficient amounts only IF the RN was defeated and IF the major ports had been captured undamaged.
So to launch Sealion sucessfully Germany needs to more than triple its sea-lift and supply capacity, capture several ports and airfields intact, defeat the numerically superior Royal Navy or prevent its interference, have the weather and seas behave appropriately, create a dedicated landing support artillery group, defeat both Fighter and Bomber Commands, make a wide landing without suprise against an entrenched enemy on a mined coastline and then carry out extended logistics operations with a minimum of supplies. Simple really
