In food processor, chop up salmon into a paste. Add cream cheese, salt and pepper, and heavy cream to make a mixture loose enough to pipe out into cucumber boats. Peel cucumbers and halve lengthwise. Slice cucumbers into 2-inch lengths. Use melon baller to scoop out the cucumber to make into small boat-shapes. Spoon salmon mixture into pastry bag fitted with a star tip, and pipe mixture into each cucumber "boat." Garnish with fresh dill.