A First Look at Vertical Sculling Oars

The downward edge is the leading edge.
Note upward bend at the inboard end.
Source

Atsushi Doi''s I-Scull from his US Patent
The downward edge is the leading edge.
Note upward bend at the inboard end.
In recent versions, the handle pin has been moved to the upper side.

In a fishtail gleam
 She leans to kiss me as she goes...
-- From The King of Britain's Daughter(?) byGillian Clarke

A First Look at Vertical Sculling Oars

The Chinese Yuloh and similar Japanese Ryo are horizontal blade sculling systems. The blade follows a 'falling leaf' pattern, angling across the sweep and switching leading edges at the end of each stroke, and kicking up a little turbulent 'fuss' at each switch.

Atsushi Doi, Douglas Martin and others have been taking a good look at vertical blade sculling systems.

The blade is still swept to and fro, but the forward edge always leads, with less fuss at the switch (especially once moving forward). This otherwise wasted energy is, in theory, availlable to generate thrust.

A second refinement is that the relatively high aspect ratio blade (long for its height) is not only allowed, but encouraged to twist, much as might a propeller blade. This has positive, hydrodynamic effects (laminar effects discussed here). In part, water is turned and tossed aftward... increasing its equal and opposite thrust forward.

In Douglas Martin's oar, shown above, the slender tip is hooked aft of the blade's Center of Lateral Resistance (CLR). As the blade is pushed sideways (albeit at an angle) through the water, it resists and twists the flexible end of the blade, causing it to lag behind the plane of the main blade.

Atsushi Doi gets a similar effect via a small fin attached low on the blade. Not nearly as pretty, in my opinion, but is powerful, removable and allows easy experimentation.

Atsushi Doi's Ve-Scull Fin

In a yuloh/ryo, the inboard end of the loom bends downward (or the mechanical equivalent). A lanyard led from this end to deck torques the loom outboard over the top, helping its horizontal blade to reverse.

 In a Atsushi/Martin oar, the inboard end of the loom bends upward. A lanyard led from this end to deck torques the loom inboard over the top, helping the leading edge reverse.

If all goes according to theory, the same thrust should be developed with less effort than horizontal blades, or more thrust with the same effort.

As a bonus, the vertical blade system appears much easier to use than yuloh/ryos (which can be challenging for  beginners). The video beow shows a monkey flinging down the gauntlet by using one of Atsuhi Doi's oars on the first go! 

So I'm jazzed!

*****




There is considerable interest in these (including my own), and information is beginning to fill in. Most of it is for small craft, but there is now at least one video available for larger craft (relevant section comes after a bit).

Be aware that Atsushi Doi has patented several of his approaches to vertical blade sculling oars. While DIY is allowed, commercially interested persons should be aware of his intellectual rights.

Sources:

Atsushi Doi's Pages (translated and hosted in English)
Reprint from Small Boat Journal... note 'sculling aid' toward bottom.
YouTube, image and web searches using such phrases as "atsushi doi scull" and "vertical blade scull"

Fussin', Fightin' and Working It Out

Calvin and Susie
by Bill Watterson

Now we may fuss and we may fight,
But it ain't like that all the time.
I love her and she loves me...
  Oh my goodness!
    Oh my Gawd!
      Oh my Ruby Pearl!

-- From Ruby Pearl by the Hackensaw Boys


Fussin', Fightin' and Working It Out

Anke and I are quickly approaching that age where folks ask, what's your secret? Old couples most always answer, never go to sleep mad.

In fact, folks have asked us all along the way. Why? Because we live together pretty much round the clock (a very young friend thought both of our names was Davanke),  in itty bitty spaces and build / work on / sail boats. Any one of these can spell deep trouble for a relationship.

We do fuss and we do fight, but it ain't like that all the time.

It doesn't feel like a secret. We just like each other. Okay, we like each other a lot! The rest is easy. But we do have a toolkit.

When we fight, we don't fight hurtful; no blame or tearing down.
We work from good to gooder, and avoid right/wrong, too much/little, good/bad; no disappointment.
We work to get back to talking, rather than fighting;
We work to please both of us; Win-win rather than winner-loser, even for a single round.
We always try to remember we're loved; it never comes in question.

'I' statements help; 'When this happens I feel this or that', rather than 'you make me feel this or that'. 'I feel' this or that rather than 'you are or do this or that'. More accurate and feels better. Takes bite and blame out of expressing or hearing about strong emotions.

Okay, bear with me on this one. We call them false if-thens. They are of the form:

If you do, say, believe, think A, then you must believe, think B.

Sounds logical, right? Logical and outrageous! B is totally offensive and unacceptable! A fight ensues.

Most always wrong. The if-then connection is false - A does not imply B. Once that's sorted out, turns out there is no outrage, no offense. Almost always a perfectly acceptable something else that had nothing to do with that connection. No foul, no problem.

Go through enough rounds of offense taken/offense defused, and it becomes clear that those if-thens are suspect in the extreme.

The most untrue if-then of 'em all? If we fuss 'n fight, then we must not love each other. BS. Obviously.

Fussin' and fightin' don't seem inevitable. It feels like something we're growing out of. We learn that the other is never disappointed, that we have their esteem. We learn to give enough slack that connection is easy. We learn that the other always, always, always has our satisfaction and well being at heart. Always.

Oh, yeah. Never go to sleep mad. That old standby is good advice.But if for some reason you have to, table it and make a date to talk it out at the next opportunity.

So kiss and make up!




HAPPY VALENTINE'S DAY!

WaterLines

WaterLines for a Box Barge / Scow

WaterLines

Mostly, in boats, we hear about THE waterline. Where the water is, right? It's a clear picture, held in common by most everyone.

But there are all kinds:

• A waterline -- A closed line formed along the intersection of a hull and the surface of water.
• The waterline -- Mostly what you'd think... where the water surface actually touches the hull. Or sometimes the painted stripe that's supposed to mark where it usually is.
  
• Design WaterLine (DWL) -- Waterline where the designer thinks it should be. That implies the boat loaded with all its outfit and crew should float right to there. Any more weight sinks it lower (raises the waterline), while any less floats it higher (lowers the waterline). For any given hull, the DWL determines its designed draft, displacement and freeboard.
• Upright WaterLine (WL) -- The waterline while the boat is sitting upright. A designer draws this in end and profile views as the DWL. In either view, it looks like a straight, horizontal line.
• Heeled WaterLine -- The waterline when the boat is heeled. A designer might draw this in end view as the maximum allowable heel. It looks like a straight, canted line.

There's more, but that's plenty for our purposes.

Designers of 'Curvy Dogs have it rough. They need calculus or planimeters and other advanced figgerin'. Poor saps! Designers of Square Boats have it easy.

Once you've decided your draft, the Rule-of-Thumb method - shown in the lead illustration - works well enough to answer important questions.

Simply draw the end view, split as shown or one for each end. Draw the upright WaterLine and the vertical midline. Now draw angled lines running through one chine and the intersection of water- and mid-line, and carry out beyond hull.

Now check your transoms, paying attention to their lower, outboard corners.We're trying to avoid plowing the bow and dragging the stern. All four corners should clear the heeled waterlines. By a fair margin at the bow and as low as you can stand aft. Dragging a small V aft probably won't hurt much, and the lower the better for an easy release.

If you have an outboard motor considered its placement for depth when heeled. If leeboard guards, see that they clear on the high side. It's convenient to place their undersides at the top of the heeled WL, so you have a visual check for maximum heel.

Okay, pin a medal on yourself. You passed this course!

*****

IMPORTANT NOTE:

Looking at the immersed triangles when heeled, we can see right off that the hull is quite stable at this angle, and still has some margin of safety.

But once the windward chine leaves the water (starts to 'fly'), the situation changes rapidly!

Do NOT sail with the chine clear of the water!!! Turn up and reef down, instead.

Hear that? We do not sail them chine a-flying or lee rail under. Not unless you're racing in a drysuit!

Square boats get an undeserved bad reputation as unstable. Let's compare to a dory of the same overall beam, which has an undeserved reputation for stability*.

What happens is that the dory goes over soon, but with slowly increasing resistance. By the time it's on its ear, the crew is feeling tippy and works to correct before knock-down.

The square boat goes over late, and feels rock solid till past our maximum. Once that chine comes out of the water, though - shortly after that chine goes flying - there is a rapid reduction of resistance to knock-down. The crew has little time to correct from that point.

Another folly; often the dory will have high sides (it needs them), while a square punt will not (doesn't need them). Bubba wants to show off by standing on the rail. Might make it in the dory. Puts the punt rail under. Apples to oranges.

At all points, the square hull has more stability than an otherwise equivalent hull with cutaway shape. It is the speed of the transition which catches the unwary. Knowing this, we act early to stay on the safe side of the flying chine. Meanwhile, we harvest all the advantages of that extra stability.

In cruiser size, you've got to work to put them over!




For solid analysis by a real naval architect on a nearly square boat, see Spray: The Ultimate Cruising Boat by Bruce Roberts. See especially his discussion of stability.


*Not to say the dory is a bad hull. On the contrary, designed to fit its purpose and well handled, it is versatile and able... a whopping great hull form. It's reputation for stability confuses less, late acting reserve buoyancy with stability. In fact, dories knock down easier than most. This is why their sail rigs, if any, are prudently kept low and small, OR they are built with an extra large dose of ballast stability (e.g., Benford Dories).