And remember... always better to over-engineer it initially than the alternative. I've posted this before, but the "Engineer" (we say sarcastically) over my back fence did something similar, and drastically fucked up his calculations on a number of fronts. The laundry line post ended up caving in with just a few wet towels. This was 5(?) years ago, and it's still sitting there, unused and fucked up.
Don't skimp on the concrete or hole depth. If it gets loose, you'll be pissed. If your husband is as big as you say, and if he might do muscle ups or even aggressive pull ups, it could loosen a light-duty design. Like, @Nettdata said, a lot of people have unusable stuff because they under-built it, there's a swing in our neighborhood that's useless.
@Nettdata , @Fiveslide exactly what I want to avoid. This is why I am hiring someone. I know I would spend a bunch of money on materials and have it end up leaning and I would cry myself to sleep for a month. Thanks for that calculation snapshot Nett. Very illustrative. The one guy wanted to do like 9bags per hole. He's probably right in his particular calculation, or at least closer than the other guy.
That's the online calculator that I linked to earlier. More than anything I think it just surprises you with how many bags it would take per hole.
Ok, so you know that. Why didn't either of these contractors know that? Well, at least now I can sketch this design out myself with exact measurements and quantities and just find someone legit to follow my plan. I'm glad I asked you idiots!
What's your plan look like? If you're doing something like the one below, the bars every whichaway would add stability, and might not require such deep holes.
Similar style but different, more linear design. We have a long rectangular pea gravel bed along a fence available to build this on. Here's my crappy sketch.
Also 6x6 posts are pretty fucking big. And as you can see in the calculator, material required for 6x6 is way more than a 4x4. 6x6 posts are shit you put a house or a heavy deck on... if you are building a jungle gym, 4x4 are probably plenty big enough, I'd think.
@Nettdata , ok, fair point about the post size. I'm not sure how I got 6" posts stuck in my brain. I think we measured from fists raised above his head to the ground was a little over 9'. I guess we could cut the height down by a foot and save on concrete. Ok, this is good. How else can I improve this design? Edit actually it wouldn't save any concrete. I'm tired. Goodnight.
I'd probably want 6x6 on the tall ones, that is a lot of post sticking out of the ground. Without perpendicular supports they could warp worse than you might imagine. You'll be lucky to find a straight 16' long 4x4 post. Make sure the contractor doesn't skimp on the 5' and just cut the top of the post off. That is a deep hole. The auger I have for fence posts, and all the ones we used on the farm, would dig 3'. Which is just right for a 6' fence post. I'd need some kind of extension or a longer bit to get to 5'. If they show up with a one man auger and an 8"x36" bit, the hole won't be big enough and the finished product won't be strong enough.
I was thinking that if you made it a cube rather than a plane you’d get more support that could reduce the depth of the hole. I also think that a little bit of flex or warping wouldn’t be a big deal for this kind of thing. My $0.02, with an eye to reducing costs.
She said she wanted them in a line to fit next to their fence. For a normal human, I'd say 4x4 is probably good. But, she's married to Shaq and he's going to be swinging on it, 10'+ off the ground on unsupported posts.