Under NC contract law can I cancel retail purchase of golf clubs 30 minutes after signing for them

This will depend on several things. First, the language of the contract. If the contract is valid, and provides that the agreement is final between the parties, and represents the full understanding of the parties, then you will be stuck with it.

One way you might have had out would depend on how the items were sold. Under the Home Solicitation Sales Act, certain transactions can be undone if a three-day notice of right to cancel is not provided at the time of purchase. This is typically limited, however, to sales that were solicited at your home. If you went to the seller's place of business, this protection would not apply.

If your reason for wanting to cancel had to do with the clubs being defective, or not being the clubs you ordered, then you would have additional protections available to you.