I coil the length of my armspan like straightedge does. Except for the entire cord. Then I use a piece of THHN solid to wrap around the top to hold it together. This keeps the strain on the cord to an absolute minimum.

Edited to add, why would you want to run a jackhammer for 8 hours? That's for the laborers.

[This message has been edited by royta (edited 09-10-2004).]