I plan on having summer beams between the bents of my home, as suggested by Steve Chappell, since the bays are 13' wide. I was wondering if I have summer beams running between each bent, will I have to offset my housed dovetail joints from eachother or can they be shallow enough in their joinery that they can be placed butt to butt.

someone please help! timber needs to be milled soon.

I take it you don't have an engineer working on this project with you? Look into omitting the dovetails and look up tusk tenons. Is there a post under the tie beam the summers connect to? The tie will need to be sized correctly. We are missing a lot of information, to give such answers out and then you follow the suggestions,the answer to your question may not be the right one.