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How To Determine Oar Length for a Rowboat

How To Determine Oar Length for a Rowboat
What length oars do I need for my rowboat?  While there is no one size fits all for oar length, there are formulas that are a big help.  Read on to learn how to get the correct measurement and for some insight into oars for today’s boater.
Difference between sweep rowing and sculling

This article focuses on oars for sculling.  Sculling means that rowers have two oars, one in each hand.
 
Sweep rowers have only one oar. Sweep oars are utilized to turn the boat from side to side as the athletes travel downstream on a river.  Competition rowing often utilizes sweep rowers.
 
                                   Sweep Rowing uses both hands to power one oar.

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                                 Here is a traditional rower utilizes two oars for sculling
 
Type of Rowboat Matters

A great deal of confusion exists as to the correct length of oars for a rowboat. There are many different methods of determining oar length.  A boat builder will most likely have his own method for determining the proper length of boat oars.
It is important to remember that the type of boat being rowed will determine how long the oars should be.
For example, a small rowing skiff would require shorter oars than a larger sculling skiff or even a racing scull. The reason is that when rowing in these types of boats you are sitting above your oars.  Your knees are bent at 90 degrees and not straight out in front of you. 

Formula
Hang on, because this will sound like one of those crazy number tricks that always comes out to the number 9 or your birthday.  It’s called the Shawn & Tenney method.
First, measure the distance between the oar sockets which hold the oar locks.  You are measuring from the center of the port oar socket to the center of the starboard socket.  In other words, you are measuring horizontally across from the center of 1 oar socket to the center of the other oar socket. 
Divide this number by 2 and then add 2 to the number.  This results in what is called the inboard length of the oar or the loom.  Multiply the loom length by 25 and then divide that number by 7.  
This gives you the length in inches.  Lastly, round up or down to the closest 6” increment.
Now the simple way to measure oar length.  Multiply the width of the beam by 2.  You will find that once you round off in the formula above you pretty much come out with the same answer.   
Although the wider your rowboat the less this method matches the Shawn and Tenney formula. Do the math.  It will amaze you.
 
Hand Distance
 
When you row, your hands will be 1 to 3 inches apart on your return stroke. 

This is for a non-overlapping grip which is what most rowers use.  (If you happen to use an overlapping grip add 6” to the length.) 

Overlapping the oar handles improves efficiency plus it is more comfortable.  It also enables you to hold both oars out of the water at the same time with just one hand.  This allows you to grab a snack out of your cooler or some fishing gear.
Longer Vs Shorter Oars
For beginners, it is generally recommended that you use longer oars as they will provide more leverage and be easier to maneuver.

If you have more experience on the water, then shorter oars may be more suitable as they are more responsive and can provide a better connection between the boat and the water.
Two Different Types of Oars

Macon Oars:

Macon oars are the most common type of oar on the market today.  These types of oars are short and wide, making them ideal for open waters where you need to go faster or row longer distances.
They have an oval blade, thick shaft and a flared handle that is used by people of all ages. 

Macon oars are less likely to catch the water on the return stroke making them more effective and easier for the novice rower.  They are generally made of ash or hickory wood and have a blunt end rather than a sharpened tip like hatchets do.
 

Hatchet Oars:

Hatchet oars are long, narrow oars designed for use in small boats and narrow rivers. They are also usually wooden oars made from ash or hickory and have a sharpened edge at the tip. 
They are used for racing, recreation, and exercise. The blade is wide and flat, with a rounded tip. They work best for the more advanced rower.
Checking Your Oar Length
To measure the length of your rowing oars, measure the from the end of the grip to the end of the blade. 
For hatchet, oars measure straight through the center. The longer the oar the heavier the boat will feel.  
If the boat feels heavier, it will require more effort to move, which leads to rowers getting tired faster. 

Go with a shorter oar if you are in a heavier, slower boat.  If you have a long reach, go a little shorter as well. 
Weight of Oars
If your aim is to row quickly then light oars will suit you best. They are also easier to handle in choppy water or when rowing against a strong current.
The downside of using lightweight oars is that they can bend easily if not made from strong material such as carbon fiber or aluminum. 
The second thing to consider is how much weight you have to move. Rowing shells are narrow and long accommodating multiple rowers.   If you're rowing with two people or more, you'll need longer oars.  Multiple people in a longer boat will have to move through more water than a solo rower would.
If you're rowing a single scull, then heavy isn't always better. When it comes down to it, though, many people prefer heavier oars for their boat because they are more stable and easier to use than lighter ones.
Material
 
 
Traditionally, oars have been made of wood.  Many people prefer wooden oars for that authentic feeling when rowing. 
Fiberglass and Carbon Fiber oars deliver the highest performance.  A wood shaft reinforced with fiberglass or carbon fiber oars are strong, durable and the choice of many rowers.
Budget oars are generally made of plastic or aluminum. 
In Closing
You’ll want to take the length of your oars into consideration if you have friends and family who will be using your rowboat.  It’s frustrating for rowers to be fatigued within ten minutes because the oar length doesn’t fit them.  You can always have a pair or two of extra oars so everyone can enjoy rowing the boat. 

If you’re trying to decide whether to buy a rowboat click here to read our article on Canoes vs Rowboats Which Is Best For You?
Learn more about Light As Air Boats here.  You can also contact me directly at dave @lightasairboats.com or give me a call at 864.367.6161.  I’d love to hear about your rowing adventures.
See you on the water!
Dave