a.b.b. - amateur boat building

Rowing - part 2

GEAR TO INCREASE POWER

(Before we get too involved in this I should mention that I have never tried any of the following techniques myself. This is just a paper study for me. If you think I've really blown the analysis, let me know with details and I'll rewrite with corrections.)

Increasing power will improve speed. Remember the formula for power is an arrangement of force, time and distance.

One way to increase power is to work out at the gym a lot and increase your muscle size such that you can pull with more force. Then slide the oars out a bit such that the extra force you can develop is converted into extra hull speed.

Another way to increase power is to quicken your stroke, pulling with the same force through the same distance. The increased oar handle speed is instantly converted to increased blade speed. You'd be rowing with lots of short quick strokes. This method works well with short boats that don't carry well between strokes.

You could also lengthen the stroke, keeping the force and stroke frequency the same. With any boat, especially a fixed seat boat with short oars, there are limits on the stroke length. If the oars start sweeping through large angles, efficiency will be lost.

Figure 1 shows the usual sliding seat arrangement. Here the rower sits on a seat that slides on rails, his feet are strapped into shoes which are fastened to the hull. In position A, the start of the stroke, the oarsman has his arms extended and his knees drawn up such that his hands are near his ankles. By extending his legs on the power stroke at the same time as he pulls on the oars, the rower greatly increases the length of his stroke compared to a fixed seat. The seat looks to be sliding about 2' during the stroke. In the diagram he has about 4-1/2' of oar handle stroke, about a 50% increase over a fixed seat. If the cadence of the stroke is the same as for a fixed seat, a 50% increase in horsepower would result. (He might also pull with a lot more force on the handles, but remember all the force he generates will transfer through his arms and hands. So I wouldn't expect a large increase in handle force in a long run.)

All the forces produced on the rower's hands are reacted through his feet alone and the human body is well built for that. None of the force reacts through butt friction.

Here are some arguments against the sliding seat.

For one thing the sliding of the seat may require a long space. (But the boat should be long anyway to take advantage of the extra power.)

The sliding seat can be a hazard in rough conditions. That may be a double hazard because you must strap your feet to the boat for the system to work.

The length of the oars must usually be increased because if you double the length of the stroke you will double the sweep of the blade. The angles the oar will sweep through will become excessive and inefficient if the oar is not lengthened. The lengthening of the oars will usually mean the addition of outriggers to help place the oar handles conveniently.

All these things may be worth the bother if you are the right person in the right boat. But maybe not. As shown in the figure I dreamed up for Roar2, a 50% increase of the power will increase boat speed about 15% . Instead of going 4 knots at full stretch with a fixed seat you might make 4-1/2 or 5 knots with a sliding seat. Normally I advise against it for a shorter boat. A longer narrow boat will probably be needed to take advantage of the sliding seat.

And increasing the speed potential of the boat will do no good if you don't pack the extra horsepower needed to push it to the higher speed. The rowing rig is just a transmission to match your power output to the needs of the boat.

There is another set up - the sliding rigger. In this boat the rower is seated on a fixed seat. The riggers that hold the oarlocks are not secured to the hull but instead are fastened to a sliding car which also contains the foot brace. The rower's feet are tied to the brace as with the sliding seat. But now his feet push the rowlocks aft as he pulls the handles forward. The overall power effect is the same as for the standard sliding seat. But the details are a bit different. For one thing the rower's weight doesn't shift around causing trim changes and hobby horsing. And all the force on the rower's hands reacts through his butt again. I've never seen one of these rigs in action. I read somewhere that when first tried in racing shells decades ago the sliding rigger boats easily beat conventional sliding seat boats and were soon written out of the rule books. Maybe so.

Figure 3 shows the system Ron Rantilla developed. Ron started with a standard canoe in which you paddle facing forward, (an advantage of paddling as opposed to rowing). To avoid having to transfer the paddle from side to side for directional control (an advantage of rowing and double paddling over single paddling) he mounted two paddles on a pillar in the center of the boat. The paddles attached to the pillar with a springy thingy that carried a lot of the paddle weight while allowing flexibility to paddle. Thus he was able to work each paddle with each hand. Ron lengthened the paddles into oars and thus he was able to row facing forward, (his "oars" were pivoted in the center of the boat in this case, not at any oarlocks, and his hands were outside the pivot). Forward facing push rowing has been used for a long time in certain areas and seems to be an inefficient way of using the human anatomy. Even fancy articulated oars that allow you to pull row while facing forward have never begun to achieved the efficiency of regular pull rowing. But Ron's system does allow forward facing pull rowing without the mechanical losses of an articulated system. Then Ron found he could run lines from foot pedals though pulleys to the oar looms and get his leg power into the equation. Then he found, that by attaching the leg lines just right and adjusting the center pillar springy thingy just right, he could make the oars dip just the proper amount under power and feather the proper amount on retrieval. No hands required in the proper conditions!!

I haven't seen Ron's system in action but there are certainly several advantages. None of the stroke power need be transmitted through the arms and hands - they can just be used to guide the oars if needed. You face forward. You sit in one position. You're feet aren't strapped to the boat.

Clearly there is some complexity of gear involved, but it's all pretty reliable and understandable and efficient. I guess the reaction forces on your body go out through the butt again. I would think a conventional sliding seat boat could boast more "power" because the rowers arm and back movements can add to the length of the stroke.

Ron wrote about his invention and experiences in MESSING ABOUT IN BOATS several times. He's not a racer but has raced the system with some success against sliding seat ocean racers. Like the sliding rigger experience, some of the conventional sliding seat racing organizations won't let him compete.

Jim Michalak

Dec. 1, 1998

Part one

Contact info:

michalak@apci.net

Jim Michalak
118 E Randall,
Lebanon, IL 62254, USA