I need help (patio roof)

I am building a gabled ended patio roof. The roof will attach to the house and extend 18' away from the home and be 18' wide. I am using 18', 6/12 pitch manufactured scissor trussess 24" oc. My question is concerning the headers that extend out 18' from the home to the roof end posts. The roof trusses will be rest on and be tied to the headers. Can I make the span of 18' without an additional post at the 9' mark? If so, what lumber do I need to utilize? I planned to use 2 2x10's sandwiched around the post. I know that I have seen patio roofs with this type of span and only end posts.

 

Take your specs to your local lumber dealer and have them spec out and price laminated beams. I do not think your idea will provide sufficient support for the roof.