Re: 12' gates
Don't have an answer for you but I would be interested in hearing how you are going to make the 12' gate because I am about to do the same thing when I move into a new home next month.
I was in the fencing business,commercial and residential for a long time! Suggest you go to a website and read the specifications for wood gate manufacturing which is not as simple as it sounds, and do it right. You can also call on a professional company which installs gates and see how they mfg and install them. Weight, material, sag, warping and bending, design, fasteners, stress, and torque are all issues. At the end of the day, I used KD douglas fir only for frames which is expensive. You can then use BC red or Atlantic white cedar finishing materials, or match your fence line pickets, boards, split, or stockade. Use mahogany only if it is going to be painted, varnished, poly'd or stained and therefore maintained. (More work but the best looking). The posts are all important. Forget 4 x 4's for gate posts. Even 5 x 5's and 6x8's have a tendency to twist, shrink or bend over time so I only use steel in two ways, either (s4s) square posts 3/16" or 1/4" wall X 5" or 6" pre-drilled so you can frame them with mahogany sides (from the grade up only), or a pre-drilled 6" I beam. Bury your posts 4' below the grade, in concrete;(do not pour concrete mix in the excavation and then add water some ready mixed compounds actually offer that as a mixing option in the instructions, but I say NEVER as it is a cheap and dirty way to install posts and very poor engineering resulting in no PSI rating at the end of the day) and at least as tall as the top of your gates, or taller for lamps, finials, or any other architectural ornamentation you wish to add. Don't forget the UF rated 12-3 wiring if you're going to attach lighting and an outside receptacle somewhere, or multi wire stock for openers if you decide one day to install electrically operated openers. There are always variations on any theme here, but this design always resulted in absolute customer satisfaction, especially if they were electrically operating gates with spans of 8' or more, which incidentally you could only do with wood along a livestock board fence. Sorry to rain on your parade, but there's a right way to do anything, and I've tried them all. That's how you learn. Good luck with your project. Bill