I need to fibreglass a new vertical fin and rudder, I have read the plans it talks about epoxy. I have looked on the spruce web site and it lists Aeropoxy, Ecopoxy and E-Z Poxy which one should I be using for the task.
Pretty much any of those you list will work. More important is the surface prep of the surface you are applying them to. Please read that carefully in the composite education portion of the plans. I use E-Z poxy, but other Q builders have used that and others you have listed with success.