DIY FRONT ROWING RIG (click for VIDEO)

Much faster and longer range solo canoeing Watch where you’re going & avoid collisions. Row straight there or follow the scenery. Oars automatically feathered on return stroke. Canoe speeds can reach 8 mph burst.

- Legs-only rowing allows taking video : waving; holding charts, binoculars; jig fishing etc.

- Arms pull against legs pushing for whole body moving exercise. Dead weight of oars and legs supported -----Simpler and more compact than the FrontRower.com:

- 1 pair of major springs easy to make vs 2 pairs with difficult ends on the Front Rower

- 1 pair of pulleys vs 3 on the Front Rower

- ball bearings for twist also roll to sweep the oar

- Simplified lighter aluminum frame with wood seat snaps in and out of canoe without fasteners

- Simple one piece foot pedals

- Generally far fewer moving parts and lighter at 15 lbs total

- Simpler lighter handles allow most comfortable pulling position

DESCRIPTION and MOTION

The oar ends in a bearing in an alumimun disc with a stainless clip around the bottom edge. That encircles the T head of a long bolt with its opposite threaded end milled to have side flats. The bolt and bearing can rotate through a stainless bolt sandwiching the pedestal plate as well as slide up and down. A helical spring with one straight tail setscrewed into a block tapped for the stainless bolt and an angular positioning screw, and the other tail setscrewed into a block sliding up the flats of the bolt, spring loads the oar end down and facing forward. A setscrewed nut and washer above the block set the vertical travel and a nut below hold the block up.

About 3 inches outboard a pillow bearing rotates around the oarshaft and its radiused outside rolls on the semi-conical side face of the pedestal. It and the springloaded inner bearing support the weight of the oar whilst allowing it to sweep depressed or lifted, and they also allow it to feather on its own axis. Feather stops on top of the inner bearing housing limit the setscrew of the inner bearing collar. Between the bearing housing and the outer bearing setscrew and around the oar is a secondary spring (with bent ends) which biases the oar towards feathered. The feathered limit is say 5° of lift angle to ensure the lifted blade skips in any water contact and the tripped limit is the blade angled about 15° aft to drive it down in the water, so the net blade turn is about 70°.

At 20.5” outboard the rope wraps around the oar shaft, so the jerk from the seat pulley unfeathers as well as lowers the oars to catch. This jerk is natural at the end of the oar return as the slack comes out of the ropes . Once caught the blade inclination to vertical drives the blade down into the water to a few inches immersion as set by the limit on the mainspring compression. When the rope pull from the arms and legs stops at the end of the sweep, the oar springs out of the water to drain and then slowly feathers to clear the water on its return and reduce the wind resistance. The oar’s emergence is aided by tilting the pedestal forward about 5 deg relative to the waterline and by ramped endstops on the sweep. The endstops also prevent the strings being overloaded by too long a oar sweep.

The Oar blades have curved back ends so that they skip on any incidental water contact on the return, and their edges should be parallel to the water on entry and immersion to minimise the travel required.The prototype shafts were bent at the blade so the ply blades could be edge supported and to mimimise the drag of driving the shafts down into the water. For light rowing or at the finish of the stroke the top of the blades needn’t be immersed and there is no loss by flow over the top, but for the beginning of strong strokes the tops have to be immersed a few inches to prevent ventilation destroying any suction behind the blades. In any case it is practically very important that the blade ends do not leak any water into the oar shafts.

SPECIFICATIONS

Main springs: port left handed, starboard right handed approx pitch of .142” music wire wound on ¾” pipe mandrel 4 turns at about ½” pitch finished OD about 1.7” helix angle

“rolling” Bearings:RBI SB202-10 Insert only for 5/8” pillow block $8x2 end bearing NTN ASS 203-011 $10x2

Oar shafts: 1”x7/8” aluminum tube outer sliding into 1.125x1” inner with 1”, outside ends flattened and 3/32 flat extension welded on

Oar blades 1/8” ply soaked & bent over metal 5 gallon bucket heated with propane from inside. Average Depth 7.5” , Length 18 “, Tip 87 ‘

DESIGN HISTORY of ROWRIG for CANUDA PLY

A canoe hull is suitable for open water fast rowing because unlike a shell it can have static stability with a rowing rig and has sufficient freeboard for rowing against any waves that may spring up. Its fineness and stability put it in between a shell and a Whitehall dinghy. Since sliding seats are used in some Whitehalls and all shells, they are appropriate for the intermediate canoe.

One drop-in sliding seat rig attaches to a canoe’s gunnels but weighs 50 lbs, as much as the canoe. The shorter waterline and recurved ends of the canoe vs. the shell will exacerbate the oscillation of pitch and surge as the rower slides, which loses energy to radiative wave damping as well as increasing the average of the quartic drag near the ‘hump’. The rower’s feet push the boat back as he ends his recoil and begins a new forward slide, slowing the boat even more at its slowest point. Likewise at the end of the stroke his deceleration exacerbates the peaking of the hull speed against the wave drag hump.

I conceived of a sliding feet alternative where the seat and the rowers cg is fixed and his feet and the oarlocks slide instead. A web search found http://www.rowvirusboats.com/virus/sliding_rigger.html with this idea in a production shell. That site gives the history of the sliding wing rig back to the 19^th century, and its banning by FISA when it indeed proved more efficient in racing in the 1980’s.

The site animation shows the sliding feet driving the oarlocks back as the arms swing the oars about them. Thus in a final advantage Virus do not themselves recognise, the blade’s velocity relative to the boat is increased, so the oars can be shortened. For example with 8’ oars 6’ beyond the oarlock swung through 60 deg the stroke relative to the boat of normally 6’ is increased to 7.5’ with a scull’s 18” slide.

A review of the classic rowing motion shows that the main muscle duties are legs push open by 1.5’ and lock, arms lock and flex by 1.5’, and finally the back hold for these 3’ strokes and rotate for another 2.5’. The strain on the back is out of all proportion to its normal use in the body and explains why back injury is the overwhelmingly predominant injury amongst rowers. Muscle mass and comparative studies between leg and hand cranking on bicycles show the legs are capable of about twice the muscle power of the arms.

By raising the seat and lowering the feet and having the stretcher pivot, the (foot) slide can be easily raised to 24”. Then the hand grips of the oars needn’t move fore and aft (see the return stroke of the Virus animation) and can be tied to the bow, as well as elastically counterbalanced to the floor of the canoe. This saves arm and back static muscle energy consumption on long distances; the arms only have to twist and lower the oars during the leg stroke which reacts against the weight on the seat as in cycling. (The Ro-Cat http://www.rocat.co.uk/boat/rigger.htm exploits the lack of movement of the oar end in its slider geometry but still has the hand and back muscles statically restraining the end, consuming muscle power but doing no useful work.)

At the end of the leg stroke, the arms and back can still be used to unload the wire for extra sweep and especially to steer. (The angle of such one-sided arm strokes doesn’t reduce its yaw torque about amidships). Then the foot movement is 2’ multiplied by 4:1 to give 8’ of blade movement whereas the arm movement is 1.5’ max applied 3:1 for a blade movement of 4.5’, roughly ½ as required. In sprints, like on a bike, arm pull also serves to brace the body against the extra leg force beyond what the seat can restrain.

But with this evolution of the foot rowing concept to include cables restraining and counterbalancing the oars at the inboard end, it is just a reversal of the inboard end pivots and cables pulling the ‘rowlock’ in http://www.frontrower.com . Ron Rantilla has so outraced sliding seats with the same hull. His has the obvious advantages of seeing where one is going, and only pivoting not linear motions. The lack of overhanging riggers and the oars moving independently movable very high makes docking much easier. Not least it alone can be rowed hands-free or with armpower throughout the stroke. So it was decided to customise, lighten and if possible simplify this system for the Canuda Ply.

The frame was triangulated by a strut from the pedestal to the seat between the legs, and by side stays from the pedestal to snap over the gunnels of the canoe with a compression strut to the keel.

The feathering motion was made external and to use a bearing in common with the sweeping motion. The oar lift and return springs were combined by using easy to wind helical springs with straight ends clamped in the pedestal and in bottom spring blocks, eliminating the return lines, pulleys and springs.

Another pair of pulleys was eliminated from the leg drive, and a pair of moving parts and pivots from the leg levers.

My prototype had bigger 1" inserts as the rolling bearings. I cut a rectangular block of aluminum in half almost all the way through on a cutoff saw, turned a shallow cone (full angle 157 deg) on it then finished the cut and had welded an insert block between the two halves and drilled the two pivot holes on the weld lines. This gave the ideal conical running surface for the inserts. With CNC one could mill the whole top of the pedestal out of one piece

The ideal centers are actually depressed so that the rocking point above the vertical stems is at the same height as the contact points of the inserts. Then rocking and vertical motion at the stems to immerse or lift the oars is not trying to drag the inserts up or down the conical slope. This is particularly important for a soft pedestal material in which the inserts will form grooves.

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