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Determining oar length.

Posted: Sun Feb 15, 2004 3:44 pm
by RonW
http://www.shawandtenney.com/sandtfaq.htm

The link is to shaw and tenney a oar and paddle company that is and has been in business since the mid 1800's, showing a formula for determining oar length. I have owned many of their ash beaver tail canoe paddles and they are a joy to use and just to look at.
The formula shows 7/25 with 7/25th of the oar length being inboard, and 18/25th of the oar length being outboard.It also shows crossing of the hands when rowing.
I will add that 2/7th. is also basically the same formula, - divide beam in half, then divide that number by 2 and mutiple the answer by 7 to get the total oar length in inches.When you divide the beam in half, you can add 2 in. if you want to cross your hands when rowing, which is a lot easier with a little practice then you would think, it also gives better stability.
Most people use way too short of oars, and consequently work way to hard with a lot less forward motion derived. Most people have their hands up at their shoulder heigth and to the outside edge of their shoulders, because of too short of a oar. You will derive more speed, power and a lot less fatigue if when you row with your hands approximately at the level of your belly button and located in the center of your body instead of to the side or worse yet at shoulder heigth. But you will find that usually you have to add about 2 feet to the length of the oar to arrive at this position.Very few people have rowed a fine line rowing boat with proper oars set up properly, when they do they are amazed at how easy,smooth and fast it actually is. Pleasurable instead of burdensome. There are exceptions to this, such as a river dory, they are not rowed, but the oars are just used to hold it back in the current and manipulate it around structure, here the river may dictate the longest oar length that is practical. I have 10 footers on a drifter. Also would suspect that the oar length might be a little long for a true barnegat bay sneakbox that has a 6 or 7 foot beam, but is only 10 inches tall. I also use the carlise aluminum tube oars (heavy rafting) that are take aparts, they sell 1 foot extensions so you can adjust as needed. About $200. a pair, I also have the counterbalance weights, and the oars balance perfectly on the oarlocks. If you look at quality wooden oars, you will see that the oar inside in the boat is square and large, while from the oarlock to the blade it is round and tapered, this is a way to balance the oars. The old timers also drilled the center of the oar handle and inserted lead as a form of additional balance. It works.Don't forget bronze oarlocks. No clamp on or plastics.
And that is my contribution to the (-non industrialized-) form of human powered boats. Next month Paddle length.

Posted: Tue Feb 17, 2004 2:59 pm
by Barry
That information is also on the Glen-L site:
http://www.glen-l.com/supplies/oars.html

I got the 7/25's formula comes from "Sail and Oar" by John Leather (out of print). Don't really know if he invented it.