I'm making a frame or arch or whatever you want to call it for a hoist that I'll be putting outside. It's a fairly basic design that consists of two 6x6x12 wood posts, 2 feet in the ground in concrete. The problem is that I need to know what to lay horizontally across the posts that will span out about 8 feet and will be able to support a lot of weight.
First off I'd sink the posts further than 2 feet or stabilize it some other way. I think it would be in danger of tipping over. If you can't sink the posts further at least dig the footings deeper and reinforce with a few lengths of rebar, then 'float' the posts while you pour the concrete. As for the cross beam I'd use 4 2x12s glued and bolted together. Its overkill but not that expensive. I've never seen an online calculator that would work for this sort of application. Joist span calculators care more about flex than total failure. btw, if you use wood glue to laminate the beam you WILL hear crackling when you load it. That's just the glue cracking, not the wood.
