i need a helix should i build or buy
That depends a lot on your skills. This is not a beginner project. Check out How to build Model Railroad Benchwork by Linn Wescott. You will see if you have the skills plus you will have a plan of how to proceed.
If not you can buy one. Either way, it is money well spent.
Since you are asking - I’m assuming that your woodworking skills are just budding. In that case I’d recomend that you buy one.
Have a good day
Bob
tramptrac, check out this thread over in the Layout Forum. http://www.trains.com/community/forum/topic.asp?TOPIC_ID=34791