Calculating size of wooden members

[KV-1]

I need help calculating the size of the wood members I need in my truss. I understand the basics; I first need to calculate the load, then the stress on each member, then pick a wooden member which has that stress with a safety factor of let's say 2.0. The reason why I want to perform the calculation, is that the solar panels I plan to put on this shade structure at heavy. Each truss would carry a weight of 600 pounds in solar panels alone. Attached is my drawing:

 

[Dr.D]

For something like this, I think you want a safety factor higher than 2.0.

 

[KV-1]

I found out this is commonly done using several rules of thumb, feel free to ask about them in this thread