Yes you need one

There is alot of tension on this beam in way of the mast step. Some beach cat have been built without a dolphn striker (mast support beam) like the Hobie14 but they had a major weakness there and were limited.

There was at least one F18ht catamaran that had a reinforced front beam. The beam was made of thick carbon fibre.

The dolphin striker is the simplest solution to this situation

A heavily reinforced front beam might be another solution but I do not know how long a heavy walled aluminium tube woud last before cracking