An Introduction to Rigging: Oar length, inboard, and blade profile

Previously: Intro to rigging, spread, and span

Continuing on with the discussion on rigging, this post will go over the other components of leverage. Last time I talked about spread and span, what they are, how they’re measured, etc. and today we’ll go over oar length and inboard, as well as briefly touch on blade size.

Oar length

Oar length is exactly what it says it is – the total length of the oar. It’s measured down the center line of the oar from the tip of the handle, including the rounded edge on most Concept 2s, all the way to the end of the blade. Concept 2 lists the average length of their adjustable oars as being between 362 and 378cm, depending on what oars you get. Oars used with sculling are shorter and fall between 274 and 292cm.

The longer the oar, the heavier the boat is going to feel and vice versa – the shorter it is, the lighter the boat will feel.

Concept 2 recommends shortening the oars if you have more efficient blades (such as their Fat2), are in a slower or heavier boat, have a long reach or a narrow spread, or when sculling, if the handles overlap too much.

To adjust the oar length on Concept 2s, you’ll need a T20 screwdriver and a Phillips flat head screwdriver. There are two screws – the clamping screw and the adjusting screw. Start by loosening the clamping screw with the flat head screwdriver (don’t take it out though) and once you’ve loosened it, use the T20 to turn the adjusting screw that’s on the end of the handle. Four turns = 1cm. To shorten the oar, turn the screw clockwise and turn it counterclockwise to lengthen it. When you’ve got it to the length you want, re-tighten the clamping screw.


The inboard is the part of the oar that goes from the oarlock to the end of the handle. (Outboard is from the oarlock to the end of the blade.) A fairly accepted method of measuring it with sweep boats is to take the spread of your boat and just add 30cm. With sculling, you would calculate the spread, divide by two, and add 6-8cm. Whatever measurement you come up with (usually 112-116cm for sweep and 87-89cm for sculling), measure that amount from the tip of the handle down the shaft. That position is where you’ll place the collars (or “buttons”, as they’re sometimes called), which are what keep the oar positioned against the oarlock and prevent the blade from sliding through.

Moving the collar closer to the end of the handle (shortening the inboard) increases the efficiency of your boat’s rigging but the caveat is that it makes the boat feel heavier. The issue with the boat feeling heavier is that it requires more effort to move, which leads to the rowers getting fatigued faster because they’re exerting more overall energy to power the boat.

One alternative to adjusting the collars, especially if you share oars with other crews, is to use a clam. Clams (or C.L.A.M., Clip-on Load Adjustment Mechanism) clip onto the sleeve in between the collar and the oarlock and are super easy to put on and remove. They’re used to adjust the load without actually making an adjustment to the oar itself. One clam is equal to one centimeter of inboard so the extra length you get from adding one (or several) increases the lightness of the boat.

If oars are shared between crews and the rigging is such that it’s too heavy for the next crew, they can pop on some clams and lighten the load without doing much damage in regards to the efficiency of the rigging. When you’re rowing into a headwind they can also be helpful in moving the boat. As a secondary benefit, they also protect the collars from wear and tear from being up against the oarlocks. row2k also has some good hacks for storing clams too, which you can read about here and here.

If you go here, you can check out a video from Concept 2 where they show how to measure the inboard and if you go here, you can see how collars are installed and adjusted.

Blade profile

Blade size is the last thing that helps create leverage. The larger the surface area of the blade, the more leverage you’ll create and the more efficient the rigging will be but it also results in a heavier boat feel felt by the rowers. As the rower moves the blade through the water, the trajectory of the blade generates the load that they feel. Different blades have different “loading profiles” so where the load is felt can differ depending on what you have (some blades have more resistance at the beginning of the drive, others have more at the end).

As technology has evolved, so too have the designs of the blades. If you look at old pictures of rowers you’ll see the “spoon” blade but as you progress to modern times you’ll see the more commonly used “hatchet” blades, of which Concept 2 has several varieties. (You can read about Concept 2’s innovation with blade designs here.) In the grand scheme of things, blade size has a minimal effect on one’s rigging when compared to other variables and shouldn’t be used to adjust the load felt by the rowers – that should be done by making adjustments to the oar length, spread, span, and inboard.

Next week: Pitch

Image via // @rowingcelebration

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Comments (6)

  1. This is good stuff. Just needed to brush up on my knowledges after buying a new set of crokers. Trying to get the sizing matched to the concept2 I was using.