I saw in kmart a weighted caster float and I was wondering in what suitation would you use a weighted caster float? I bought one thinking the weight added to the float is calculated such that it would sit upright perfectly at the surface with just a little of the top of the float above the water. In other words I was expecting the weight almost, but not completely cancelled the bouyancy.

I went home to test it in a big cup of water. To my disappointment it is not sitting in the water vertical, but rather only a tiny fraction of the float is submerged and at an angle. I then tried to add weight to it to try and find how much weight I need to add to make it sit in the water with just a little bit showing above the water, and I had to add quite a bit of weight, which means in the real rig I'll need to use sinkers anyway.

So I'm not sure what is the purpose of the weighted caster float. Has anyone used it and can share how / when to use it?

As the name implies. It is for casting. Not buoyancy.

You use them any time you do not want added weight on the main line. But you want to be able to cast and use a float.

I use weighted glitter floats when squidding. Also for live bait when added weight to the line will impede the swimming of the live bait.

Use them when using a heavier line than usual. For example. Live baiting off rocks with say 30lb line. Or when casting into or side on to a breeze. They help keep the line straight in flight and reduce mid cast line twist and wind drift. You can use them when an UNweighted float can be used but not the other way round.

The weight should not be enough to hold the float upright. The float should lay on it's side. This way it can take the weight of even a larger live bait or stay afloat if swamped by a wave. It should have a coloured top. Usually green or red (fluro). If you cannot see the top, then your overall weight (bait with terminal tackle etc) is to heavy for the float.

In most cases the best way to rig is a running rig. A rubber (silicone) float stopper. The stopper can be moved by sliding it up or down the line so you can set the depth at any time. Then a plastic bead to stop the stopper getting caught in the float tube. Then the float. Then another bead to stop your terminal knot getting stuck in the float tube. Then your terminal...hook, swivel etc.