Steering using an oar

[sarabande]

I have been given a pair of dusty carbon fibre oars (sweep) from one of the dark blue rowing clubs. They are as yet uncollected, and I gather that the blade is not one of the latest Vortex/Concept types but more like a Macon.

I am churning some ideas around for

1. engineless propulsion using a rowlock on the stern ("yuloh")
2. emergency steering in case one of those "whale killer" dolphins eats my rudder
3. integrating the oar into a self steering system instead of using the servo blade connected to the tiller.

The boat is 32ft long, with a skeg-hung rudder of about 6 square feet (very much an estimate) or 0.5 msq. The oar length is approx 4metres., and the blade area about 0.1 msq.

1. For yuloh-ing, will a shaped blade make use difficult, or does one compensate by a bit more effort on one push or pull ?

2. Thinking about the leverage of a rudder vs an oar: rudder 0.5msq at 0.3m from the bearings and the oar blade 0.1 msq at 3m from the rowlock. It looks as if the oar generates a lot more more steering effort, and right from th estern of the boat, not from the trailing edge of the skeg. What critical naval architect thinking am I missing ?

3. Modern self steerings use the water blade to provide power to the tiller. The blade being vertical and thin chord (high aspect ratio) looks very vulnerable ; does an oar system provide more power to the tiller, and is it less likely to be fragile ? Do I need to rethink an oar-based system for self steering, from the existing servo blade types ?



All contributions, suggestions, and developed ideas gratefully received.

 

[bluerm166]

I think you have the right concerns -yes such an oar will generate considerable forces and require a substantial braced mount.
Have used a hebridean wind vane on a transom hung rudder/highish freeboard 26 ft yacht ,which necessitates a very long pendulum 'oar' pivoted around 300mm beyond the transom ,with distance from pivot to centre of effort c. 1700 mm.The effective area in the water at rest is c. 0.1 s.m.
The pendulum generates massive force that cannot be resisted , plainly far in excess of the 80 kgs. offered by an ST2000. The length and the pivot position are key.
Sculling in a flat calm harbour or downwind might be a use for an oar (depending on profile ) but I suggest that carrying a spare pendulum blade ( and other key items for the system ) would be a better way to assuage concern about damage .I believe anyway that some blades kick up and would be behind the skeg ?

 

[neil_s]

It's an oar - I think you need to use it as such - so a strop on a sheet winch for some forward propulsion sounds like a plan. I think the yuloh idea won't work because the yuloh needs a certain flexibility to give the correct angle of attack that the oar doesn't have. Emergency steering? Well - it's a lot better than the spinny pole with a floor boad tied to the end!

 

[DownWest]

A Yoloh works best with a symetrical wing profile. i.e. flatish on one side and curved on the other(forward) and well angled down. Similar to sculling with a vertical oar when driving a boat sideways
If your blades are like what we used to call 'barrels' then would drive quite well.

One of the DCA guys was here with his Drascombe, no engine, but a nice set of carbon oars and outriggers. Moved it very well.