A Simplified and Sculling Oar

by Hans van der Zijpp - Netherlands

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For my little trimaran I use a very clever sculling method, invented by Atsushi Doi. You can see all his information by googling/youtubing AD sculling.

This year I participated in the Dorestad Raid, a sail and oar event in the Netherlands. I noticed I could keep up with most of the rowers, and that the other participants were surprised how well the AD oar could drive my boat (also backwards – very practical for docking).

I already made several versions of the oar, and I think now I have found a handy method for making such an oar.




The “real” version is beatifully carved from wood, with a curved handle (this bend produces automatic rotation of the blade).

My version is made from an old windsurf mast, with a blade made of a sheet of 2mm HDPE bent around the mast and a “cranck handle” on top instead of the bent loom.

This produces a strong, light, easy to make, cheap and maintainance free oar which seems to work good.

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I hope the attached  pictures speak for themselves, especially if you combine them with the original information/video’s from Doi.

A few notes :

  • The measurements shown are from my oar, and are all guestimated. They can be used as starting point.
  • Plastic sheet was difficult to find (and expensive!) untill I found the right supplier. HDPE 2mm thick is good, use the black version for UV resistance
  • I plastic welded the trailing edge (you need welding rod and a special piece for your heat gun). I folded the sheet, clamped the ends flat together with the underlying sheet sticking out a few mm, welded and used a planer to smooth the edge. HDPE is easy to plane.
  • If you cannot weld you can probably sew the trailing edge together with a lot of small holes and strong thin wire (like kite line)
  • Another option might be to use ABS plastic, there was an article in Duckworksmagzine about welding ABS. Or use something else that’s bendable in a fair curve.
  • My oarlock uses a PVC pipe slit lenghtwise, and a rope to prevent the oar sliding down too much. This is smooth without noticable friction.
  • My cranck handle is a plastic cleat tied with bycicle inner tire, but you can use all kinds of handles. A bit more elagant wouldn’t hurt 😉
  • The “strong rope” is the secret why this oar works so good. It takes the forward force of the oar, so you only have to work the oar back and forth sideways. The rest goes kind of automaticaly.
  • Normally, you would have the spar (mast) at about one third of the depth of the chord of the foil. For this oar it should be more forward, or else the oar is overbalanced and starts to behave unpredictable.

Greetings from Amsterdam, and if you experiment with the oar Atsushi Doi is interested to hear what you have found out.

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6 Comments

  1. Very nice! In the US, thin plastic sheet can often be purchased as wall paneling. It isn’t HDPE, but it could work. A roll up plastic snow sled might also work. Might need to coax it flat first. I’d try unrolling it, weighing it down, then dumping a pot of boiling water on it. Allow to cool and maybe it’d stay flat?

    • I used to find usable plastic sheet in the dumpster behind a sign shop. They made plastic signs and the scrap was great. Price was right, too.

  2. Parallel evolution at work.
    The version I’m working with has a straight shaft of 1-3/8″ O.D. aluminum tubing and a blade carved from a piece of LVL beam and glassed. Next blade will be hotwired foam w/composite skin. Rather than an oarlock and restraining line I’ve got a “universal joint” based on a wiffle ball (~3″ dia hollow polyethylene ball) that fits in a fiberglass socket.

    Not much time on my version, house building trumps all right now, but it worked amazingly well the first time out, which is amazing in it’s own right. I found it instructive to watch the flex in the shaft and blade as Nomad was driven forward, the little whip back at the end of the stroke helps the drive forward as you switch direction. Mr. Doi’s invention really is a marvel.

    BTW I believe you are the kind soul that pointed out on another forum that I originally had my crank on backwards.

    Cheers,
    Skip

  3. I guess the title of this article should have read “a simplified AD sculling oar”, correct? Anyway thanks a lot Hans – amazing work, need to try it. Just briefly checked out Atsushi Doi’s website for his geometry recommendations. I wonder how many geometries did you try out (blade width/length) before settling on this one?

    • Hello Mario,
      The title was indeed meant as “simplified AD sculling oar”. My surfmast/plastic oar is the 5th version. I first made wooden oars from fir. The blades were a bit longer and 18mm wide and about 120mm chord length. These blades were quite flexible, and I broke all the oars (difficult to get it strong enough with this thickness). Then I made quick a plastic-cobbled together-version around a wooden spar (old broken oar from a rowing skiff). That worked good and I used it for a year. My newest version (with surfmast) is lighter and unbreakable. The profile of the blade is quite thick, but it seems to work for my boat. This oar performs a bit better then my earlier/thinner versions – I measured it with gps. For me it’s important that it doesn’t break, and I don’t expect that another oar will perform a lot better, so I’m satisfied.

      If you’re going to try one, I’d suggest to make an oar with at least the same surface area as my oar. I use the whole blade when I’m sculling. You can always move the oar a bit up out of the water if the surface area is too big for your purpose.
      Good luck,
      Cheers,
      Hans

  4. yep – confirm that blade area should be much greater than an oar blade.

    I have used one of these (blade is a strong plank shoved into a 2″ light metal pipe from a swing set)for a couple of years.

    i like that it works better in waves than the “falling leaf” type of yuloh

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