Turning distance between the truck and travel trailer

As the first responder said too may variables . Example my trailer slopes a lot I haul a canoe that because it sets up on a rack can hang off the tail gate of the truck towards the trailer by 3 1/2 feet and I got plenty of clearance. Yet I cannot put the tailgate itself down as I hit the trailers jack with it. Wish the tongue were 3 inches longer.

As was mentioned, you can turn tight enough, (usually backing up), to hit the trailer with the truck bed. You might be O.K. going down the road but you want to check when backing into a site. A rack would be a solution. I have a cap on the bed with racks and I put another bar on the cab. I can carry two canoes with this arrangement because I can move them far enough forward, over the cab so they don't extend out very far in the back. When I carry one canoe, it's centered so it's position doesn't change relative to the trailer when turning.
If you don't have a cap on the bed, you can get racks that mount on the bed rails.

I did a trial run. Due to the tongue jack I cant turn with the tailgate down (pickup with a 6 foot bed). I put 2 single Kayaks (love Costco!) in the bed with their nose down in the front of the bed. Their tail went out at an angle above the tailgate. They extend out over the jack and tanks, and they clear the trailer when turning.

Trial run is best - just have a spotter with you to let you know what's going on back there.

Pawpaw

no 2 models or makes of trailer.. has the same distance from the Ball socket on the "A" arm and body of trailer AND battery box.. AND propane tanks.. AND tongue jack... AND...

so a tape measure is needed... or a trial run...

It's entirely possible you can't leave your tailgate down without hitting the tongue jack.

Something centered in the truck, it is about the length of the trailer tongue, because what is in the center swings to the outside on a turn.

Off center, your long load moves closer to the inside, then across center to the outside. The further off center, the less room. Ultimately, it can be zero, because stinger plus tongue length might be short enough that you can hit the front ot the TT with the corner of your tow vehicle in a tight enough turn, particularly when backing. I know this from experience, and know I'm not the only one to do it, because I've watched other people hit their hooked up TTs when backing. I've also seen them hit the front of a fiver wit the cab of their truck.

Too many variables to guess.....tongue length, height of tongue jack, distance to propane cylinders/cover, axle position, etc.

YOU will need to make a 'trial' run to be sure based on your set up and what is hanging out.