One thing to keep in mind, IC's work on thermal transfer, the more surface area the more transfer. There is an insulating property happening during the cooling. Tying the coils together tightly keeps the hot wort from utilizing the coils to their highest efficiency. I understand the need to feel like the unit is solid, however, it is best to leave a space between each coil.
I agree with the soldering suggestion above (just leave a space between coils) or if you don't want to solder, I would suggest taking some fairly heavy copper wire, wrap it around the bottom coil, then twist them (like a bread bag twisty tie) until you have a 1/4 to 1/2 inch space, then wrap around the next coil up and repeat the process until you are to the top. Do this three more times around the coil and you are good to go.