4X8 ridge max span?

DIY_louie

Hi, sorry to post a similar topic again but I want to hear more expert opinion first.

I have a 1 story open ceiling workshop. Right below the 4X8 roof ridge has a 5' opening. I want to expand it to 7' wide. The total ridge length is 16' but it constructed with two 8' long douglas fir supported by 2X4 interior wall, the height is about 12'. The opening is only beneath 1 of the ridges so my plan is placing a 4X6 right below the joint of 2 ridge then remove 2 pieces of 2X4. The other end of that 8' ridge is laid on top of the exterior wall so I don't need to do much about it.
Is my plan ok? can a 4X8 fir span 8'?

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