Bubbles Suck!

There are several blog references to the importance of creating bubble free paddle strokes related to kayaks. The Outrigger community does not seem to have the same written information. There is no doubt that paddles generating bubbles in the water are inefficient.

When looking at the water behind very skilled paddlers, there are almost no bubbles. Often with more powerful but novice paddlers there are lots of bubbles and in the beginning I thought, “My, they are so strong they are cavitating the water.“  That is not the case.

Its more a matter of sucking air into the water because of poor technique.

The other day while steering a 6 man outrigger I kept on hearing this burble popping to the surface on my right side and looked to see a large cluster of bubbles coming up from the #4 seat in the boat.  They were surfacing just behind the six seat making a quite loud popping sound. The paddler was putting his blade in with no forward angle and pulling hard before there was a solid catch.

What’s wrong with bubbles?  Bubbles suck.  While I am not a hydraulic engineer and cannot specifically  quote hydrodynamic theory, I can use an example from aviation theory with some knowledge. Any turbulence behind an airfoil creates drag and requires more thrust to move it through the air. Using similar logic, I believe bubbles are indicative of drag and wasted effort.  Bubbles are compressible so if they are in front of a blade they will allow the blade to move without reaction and lessened thrust. Furthermore, air bubbles in water are expandable and if they are behind a paddle, then the decreased pressure behind the paddle will cause the bubbles to resist the blades moving forward, again wasting effort and lessened thrust. Bubbles suck!

While this is not cavitation such as occurs at a propeller. Cavitation happens for different reasons, but the loss of thrust is similar. With drag comes resistance, so I believe that the drag produced by the turbulence from bubbles gives the paddler a sense of working hard. The power input is high without a correspondingly high output.

What causes bubbles? Several things can cause bubbles, but the most common is the paddle inserted in the water and power applied prior to achieving ‘catch' . This leaves the back side of the blade open to the surface air and the air being sucked down into the water behind the moving blade preventing the blade from 'anchoring' in the water. If the blade cannot anchor, there can not be as much reactive thrust to our effort.

A good catch will see the blade slice forward into the water with little of no gap air gap on the back of the blade prior to pulling.  The most efficient is to put it in perfectly to start with, and next is making sure that there is no gap back there by a solid catch PRIOR to the pull. With excellence the whole operation is effortless, efficient and powerful.

Bubbles Suck, Part 2

If you are generating a pocket of bubbles in seat 3, guess what seat 5 gets?  Depending on boat speed through the water, the pocket of bubbles you planted into the water is exactly where seat 5 gets to put their blade. The mess you leave in the water directly affects other parts of the crew and the boat run. In my humble opinion from the back of the boat, its really worth getting rid of bubbles. One of our coaches usually hollers out "more catch time" which means a microscopic part of a second extra to ensure the paddles catch happens BEFORE pulling.

There are endless concepts of "perfect" paddle strokes. There are also many paddlers with poor technique that can go like hell, so as far as bubbles go, “I am just saying, is all.”