So you can see more or less that the threads are really important in ice...especially dense ice like on a lake.. more or less though the weakest part of an ice screw is in the hanger ESPECIALLY for what kiter's are doing.....which tends to push the ice screws hanger beyond its range of motion.
The next few pictures show a solution to the hanger issues but also let you keep the ice screw for the emergency needs that may come up on the lake while riding. This is a REALLY OLD common sense ice climbing trick (every ice climbing knows about this) More over it has been shown through countless studies that in good ice a ice screw can be very strong...enough that a carabiner will break when the screw and hanger are properly aligned. Yet in bad ice or with loads that are not with the axis that the screw and or hanger is in line with, they can be very and surprisingly weak and dangerous. Ice screws used in the manner that the photos below show can really save your butt (especially if you land on a ice screw....or save your skis/snowboard base if you ride over one))
realize this as well. The "thread" has been for years called the "V"thread in ice climbing, a few years ago it was with good data to support...found that lining the thread to be perpendicular (NOT PARALLEL) to the load was significantly stronger. This means that the thread should ideally be looking like an "A" not a "V". in the perspective that the kite will be pulling from.
Also, consider that the ice screw IS NOT EVEN necessary to make a thread, For example, one day while teaching a snowkite lesson, on a frozen lake., I used a ice axe "adze" (think chopping axe) to carve out a trough or trench like groove about 12 inches long and 3 inches deep.....here I used water, snow, and slush to fill in the space, but before totally filling in the trench, I put a piece of 11/16 inch webbing into the base of the trench and with the cold temps, about 10 minutes later it was DEAD FROZEN and help with NO issue, three fully powered kites looping simultaneously.
Another consideration is that for lakes and thermal heat or "conductive" heat transfer from the sun INTO the hanger and tube of the ice screw is a major factor in why some days an ice screw will simply melt out of the original hole made say early in the morning only to return early afternoon to the screw that a mouse could lift out as th metal heated up and made the hole bigger.
Mind you all, this is the tip of the ice berg. (no pun intended) in regards to the complexity to ice and ice screws. But it is lay information where I am from as I teach snowkiting as much as Ice clmbing and this info needs to make it out there.
thanks for the patience