Hula hoops can “go wrong” a couple of ways when you first start out making them. How you correct the shape of a hula hoop depends on what’s wrong with it.
The easiest problem to fix is when the hula hoop is “crooked,” that is, not all in the same plane. This usually happens if the tubing is twisted on the roll. Let the hoop lay out in hot sun, flat on the ground, for a few hours. This will flatten any hoop.
(Joining the ends when the irrigation tubing first comes off the roll, and then letting the hula hoop flatten itself out in the sun, is easier than letting all of the irrigation tubing straighten out and flatten before you join it up into hoops.)
Flat spot on the hoop, at the connector
The first and last foot of tubing that comes off a roll is usually much straighter than the rest of the tubing. When I make hula hoops, I cut this straight part off and discard it (or give it to someone who makes rain barrels). If your hoop is reasonably big, you probably won’t notice the flat area much anyway.
If you’re making very small hula hoops, you need to bend or shorten the connector before inserting it, or you’ll create a permanent flat spot on the hoop that may interfere with how it works.
Cutting one ridge off each end of a 1/2″ connector will also work, but chipped my tubing cutters. I prefer to bend the connectors using simmering water. Let the connector heat up, then lift it out of the water using one very large nail, or skewer, or pencil, in each end. Gently bend the connector (just a bit off straight) and drop it into cold water to cool. Now you can make up baby hoops that will be more perfectly round.
Storing hoops on their own weight, or leaving them squished in a hot car trunk, will sometimes make them more oval than round. Leave them flat on the ground in the hot sun for a few hours, then pull them gently back into round, and your hula hoop should come back into the right circular shape.
Oops. Generally, a crease is death. (It’s always death in a hula hoop bought from a big-box store.) One of my larger hoops got creased when it got stuck in the truck and I pulled, when I should have pushed back. I worked the crease out by rubbing on the damaged area, and then left the hoop flat on the ground in the sun to recover. The hoop is OK enough, but it will never join me in a parade or performance again, and it will always be weaker at that place.
I make and sell hoops for people in Eastern NC, most of whom buy them at events. If you don’t live nearby and are looking for a custom hoop by mail, try Diana Lopez’ hoops from Body Hoops.