The spiral plow is very simple and does exactly what is says in the name, it is a plow which makes a spiral in the sand. it prints in three parts two which assemble to make the whole spike and the other being the plow.(update) after testing the plow i found that the diameter of the rod was too small, so here is two more moddels. the "rod 2" which will slide over the first rod if you have already printed it, and the "rod 2 without rod 1" which will fit on the spike if you have not yet printed the first rod.

simply grab a piece of string tie a loop in both ends and place one on each piece, then stick the spike in the sand and drag the plow around it, you will slowly see a spiral emerge which will leave a smile anybodys face.

Now although the concept is simple there is some maths behind it which is anything but simple.

Because the models don't need to be very strong it is possible to print them with the following settings:
Infill: 5-8%
shells: 2-3
Layer height: 0.3 or higher if possible
no support or rafts are needed.