Bob is an australian "mate" who was a couple of months in China and with his genius and seawolf eyes he learnt from the locals. Also he began using a yuloh with the assistance of a chinese man, in there and to mowe the boat owned for that. Now, he still sharing with us what he learnt in practice. He can easily mowe his boat till 3knots, a one ton displacement hull.
I tell him my wave propulsion device is inspired in this kind of oars, so he send me by e-mail all this information. THANKS BOB.
"The total length of Yuloh is 3.000. This moves my boat quite well,
The blade is ,800 long and .130 wide. From the tip of the blade to the first angle is 2.000.
This angle is 160 degrees.
from the inside of angle No1 to the second angle is .720 and this angle is 160 degrees also. The small branch perpendicular to the shaft is .140 long, The tether rope which secures the Yuloh to the deck is attached to this. I have secured this small spur by means of a tenon joint through the shaft of the Yuloh, the end of the tether is secured to a ring bolt in the deck. The tether is adjusted so that the end of the Yuloh is approximately parallel to the water line
The pivot point will depend on the shape of your boat. This point can be a conventional rowlock, a pair of thole pins, or whatever takes your fancy.
I made my angle joints using epoxy secured with a couple of dowels and then lashed a 3mm nylon whipping over all which I painted with thinned epoxy. Nothing has moved in three years,
I have painted a white band exactly one metre from the tip of the blade which is useful as a depth sounder.
In China, I have seen quite sophisticated Yulohs clearly made by craftsmen...I have also seen rough, old bent tree branches with a lump of ply nailed on one end as a blade. They all seem to work just as well
The weather has turned bad and I am waiting for an improvement before I go out.
Best wishes, Bob."
Notes:In Australia they use to say 140mm to say 14 cm.
The most of the people says the yuloh don't work very well in the chop.
This oar can mowe bigger boats, really big, than normal oars.
Don't need a high physical effort, so can be used for hours.