Listen. Even if you don’t row or coach with Concept II oars you need to go to their web site <http://www.concept2.com/>.
Once you’re there, dig around. Especially follow the links concerning oars. There is a wealth of information there.
Yes, yes, yes. I know much of it is about their products. However, the information on grips, looms, shafts, etc. can be applicable to most types of oars.
One section that I’ve found very helpful is their PDF section
<http://www.concept2.com/resources/pdfindex.asp>. There they have posted over 50 PDFs you can download. There is some excellent information there.
“C2,” as they are sometimes called, has put a lot of time, money, and energy into revamping their site. Check it out.
It will be worth your time.