You need either a big payloader, or a telescoping boom forklift to reach over 13'. Perhaps a standard type fork lift with a tall boom might work, but not as well. We had a 3 yard loader here, and it would not unload a triaxle log truck by itself. I had to use the Lull forklift. The loader on the truck would not pick up the 30' WO logs.
I have a 710 John Deere backhoe that I can get over the standards with, barely. I do not let anybody else use it, the headache rack lays back too far to hold the log on the forks safely. You have tilt down a little at full elevation. I would second the payloader or zoom boom. If that is not practical, is there someplace you can build a small wall, say 2 feet high and back fill. Pull the truck on the lower side and use the loader from the wall. I unloaded trucks for years like this with a farm tractor.
Guess I should add, this will be an ag tractor with a front end loader. I need the ag tractor for other farm duties, If the loader would work to unload log trucks, that would be nice, but if is actually 13' to get over the uprights, I don't think the tractors with loaders in the size range I am looking at are going to be able to do it. Still in the planing stages at this point, looks like I might have to build a berm to get high enough.
Since most trucks are built to haul loads at or near max legal height of 13'-6" the stakes are usually 13' tall. That being said the only way to unload one with a "normal size" farm tractor is to have a loading ramp built up that puts the bottom of the tractor tires near the same height as the bed of the truck.A ramp is actually very easy to build by sticking a few posts in the ground and building a wall and then filling it with dirt. This also comes in handy if you ever need to load/unload something off the back of a box van or flatbed.
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