Length of a spiral on a cone with 5 rotations

[Monachus]

Hi everyone, I need some help ASAP please!

I have forgotten how to calculate the length of a spiral in a cone. I am really only interested in part of the cone from where the diameter is 8m to the base where it will be 10m in diameter.

in this part of the cone there will be 5 rotations each traveling 3.6m vertically up each time.

Thanks for your help!

 

[HallsofIvy]

So your spiral is on the surface of the cone?