My wave scull has a 3in hole for the oar and I just have a piece of pvc pipe glued in i can send pics of it when I get off work. Where are you located, if you have questions here's my number 541-294-0065
This is the second oar I built, it ten feet long. 6ft handle and 4ft blade, the blade has one coat of fabric and 2 of cloth fiberglass, it is flexible with no effort to start sculling