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Anke and I are building our next boat, and writing about it at ABargeInTheMaking.blogspot.com. Access to the net comes and goes, so I'll be writing in fits and spurts.

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Fair winds!

Dave and Anke
triloboats swirl gmail daughter com

Sunday, December 29, 2013

A Short Review of Traditional Sailing Box Barges (Scows)



Easy to improve on these lines... or is it?

A Short Review of Traditional Sailing Box Barges

Box Barges (Scows) aren't new kids on the block. After the log, dugout and raft... barge.

For most of that span, they've been rigged for sail. And not just until folks knew better. Right up into the last of the Age of Sail, outlasting the clippers.

Take a look at the picture of the barge-ketch, above. It's likely a Great Lakes boat from near the late 1800s or early 1900s. She likely hauled freight in competition with any number of Curvy Dogs serving the same ports. Not only did she hold her own, but a whole fleet of her sisters were thriving in the same waters.

But look at those lines! Her steep, knuckled entry and exit are close to poor as can be. And this in a day when quality wood and skilled labor were in relative abundance. 

An abrupt entry means plowing water. An abrupt exit means a turbulent (draggy) release.

The economic advantages she gains through simple construction and maximum capacity on given footprint must have been enormous to outweigh making the slightest concession to speed! Hullwise, anyway... that rig looks speedy to me!

Still, if you ask me, those knuckled ends strike me as hard or harder to build than curves. And they wouldn't give up that much displacement. And with that bowsprit, lengthwise port costs couldn't have been a huge factor.

So it's a bit of a mystery that they built them so abrupt. Did they need to make the most of the deadflat for, say, stowing lumber?

ALMA, getting slipperier.

Here's ALMA, a San Fransisco Bay Hay Scow. Similar coasters carried Russian ice cut from Swan Lake, New Archangel (now Sitka, Alaska) to SF... no small feat, today... that's still one rugged coast!

 Lines are getting easier (longer and less abrupt)... more bottom curve and angle at both ends. 

We note that the exit is easier than the entry. Curious. Is this an evolved, hydrodynamically efficient arrangement? Or is it some holdover from the old (discredited) cod's head / mackerel's tail rule-of-thumb?

Let's establish a convention for talking about the proportions of aft curve : deadflat : fwd curve... looking at ALMA, I'm going to guess about 1/4 : 5/8  : 1/8 of LOD (Length On Deck).


Civil War era blockade runner
(replica built by Crystal River Boat Builders)
 
Here's one built to run wartime blockades... in other words, didn't want to be loitering around. I'll assume she wasn't slow, nor does she look it.

But she was also running supplies to ravenous armies, and likely slipping up sloughs and creeks to get out of sight. Of course she's a scow!

Proportions look to be about 1/3 : 1/3 : 1/3 (see also other pics of SPIRIT on related sites).

For the first time, we see an easy entry. Did this contribute to speed?


ANNA, looking sleek!
ANNA is another who's sisters were born in the Great Lakes. No plodder, she, though... This type had a reputation for speed among fast boats.


ANNA looks to be about 1/2 : 1/4 : 1/4... hard to tell... her aft curve is so long and easy that it could be anywhere from 1/3 to 1/2?

Here again, the entry is more abrupt than the exit, though it didn't seem to tarnish her reputation. 


*****

So the question remains... is the blunt-ish bow fast enough to make no never-mind? Is the easy exit and release the real key to increased speed? Or is it an artifact of having aft cockpit and quarters aft, rather than heavy cargo? Or both?

Fortunately, we see 'good enough' anywhere in the range. 

My guess is that a moderate curve forward gives good performance, rises well to waves and pounds less in most conditions, while an easy exit lets the hull pick up and go. Other considerations can push or pull the shape this way or that without undue penalty.


*****


An interesting aspect of traditional boats is that they were seldom designed, per se, but rather evolved.  Any more efficient variant, relative to the job at hand, tended to get copied.

Today, we tend to think in terms of speed or windward ability as the prime criteria for comparisons. But historically, at least among working craft, economy was paramount.

And economy is a gestalt of factors.

Even our first example was economical. We may no longer remember the reasons, but those who built and worked those pug-nosed vessels likely knew to the penny where profit lay and where not.

And that gestalt doesn't begin and end with the vessel itself, nor even its interactions with wind and sea. It perfectly reflects the state of supply and demand of its time; personnel, materials, cargoes, markets, competitors... even laws and the ability to enforce them. Of course speed and windward ability factor in, but they don't always have the only, or even the last say.

Our own lives have their own economic considerations. We want the best return on our investment, but 'best' is a fuzzy, nebulous, personal affair. And we're often led to look where our best interests are not, by those who would sell us a load.

We and the vessel we choose - if the relationship is to be a happy one - must also find economic balance.






13 comments:

  1. Hi Dave,

    Thanks so much for this discussion of entries and exits, with such nice examples. I think I'm finally starting to get my head around the subject. Things always look so simple AFTER you understand them!

    Happy new year!
    Shemaya

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    Replies
    1. Hi Shemaya,

      Glad it's helping... it certainly helps me to 'think out loud', as it were.

      Dave Z

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  2. What mainstream sailor doesn't secretly lust after a simple shoal draft spacious home that can be tucked way way way way way way way back where others cannot follow? That's not going to require years of labor to acquire. Dried out on a sand flat with the wind hitting a low moan occasionally outside, a half moon in a cloudless sky, a nice fire in the stove, a great book, some soft tune-age setting a pleasant tone, the dog and cat slumbering by the aft door, a nice 6-pak of custom brewski dangling off the stern cooling in the water, 9 months of food tucked away in the huge holds, no constabulary around for miles, the wind gen ticking over like a charm, the love of a good mate spicing the air, and a good following wind forecast for the next day. Hmmmm, hmmmmmmm, hmmmmmmmmmmm. Scows do it to it. Happy new year!!!

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  3. I think having a bit of rocker throughout is good, not necessarily for shape underwater but for structural rigidity. It doesn't take a lot of curvature to get a flat sheet to act like an arch. Even something like a 2" deflection over a 4' span would be sufficient to keep it from flexing when pounding up and down big ocean waves. If the plywood doesn't have a bit of transverse curvature, it will flex longitudinally. Also, I would want to have chine runners, so that the centerboards/leeboards can stay up when sailing free or when taking out over shallows. I have found the motion to be much more seakindly with the board up and, when heeled over even slightly, the hard chine acts like a v-hull an allows the hull to track nicely anyway.

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    1. Hi Dimitry,

      Good points all!

      RE Rocker: It's true that arch adds rigidity. I'm of two minds about how beneficial it is.

      In brief, SLACKTIDE's bottom is designed to flex (trampoline bottom, I call it), and we've had no flex related problem in 6 years, with many challenging groundings.

      My theory is that a flexy bottom acts like an elephant's foot to delocalize stress. A rigid bottom, on the other hand, must absorb stress in a small radius. Not sure if there's a net gain in strength, as it seems it must stand up to more in a given situation.

      In practice, we haven't had structural problems with either type. We tend to build thicker-than-usual bottoms which are copper plated in addition, so it's hard to say if our safety margin is high, or if the two approaches are functionally equivalent.

      So hard to say which would give first in a destruction test (which we hope fervently to avoid!).

      Our next boat will have internal, girder furnishings which will divide flexy areas into much smaller ones than on SLACKTIDE, so we should have more data in a few years.

      Historically speaking, both rockered and flat bottoms seem to have survived, though if one looks in an industrial barge, the reenforcements can be massive! Unfortunately, I don't have a construction plan for any of the reviewed scows, above... sure would be interesting.

      RE Construction: In TriloBoats, I've stuck with a (large) deadflat partially to minimize draft, but primarily to dramatically reduce construction time and effort.

      Construction over the deadflat means no lofting, layout, spiling or cutting of (vertical) structures such as sides, chines and faces of furnishings. Bulkheads are uniform, don't require fairing and have no bevels. In some cases, standard house furnishings can be bolted in place with no trimming to fit. The deadflat itself is a large worksurface for constructing components, and forms its own, simple jig for fully upright construction (no turning of the hull).

      Having built LUNA (fully rockered, AS hull) and three TriloBoats, the difference is striking. LUNA is already much easier to build than most, but large deadflats can't be beat, in this respect.

      Being lazy and cheap, this consideration continues to win the day for us.

      RE Chine Runners: I generally agree, though I'm a little afraid of them on larger craft in rocky areas. We often set down or lift off with side slop, and they seem vulnerable. If they were to go, it would likely be fail dangerous since they'd have to be strongly attached to the chine.

      Generally, we've found that, as you say, the hard chine acts like a long, shallow keel, and we're able to hang on in shallow water with the boards up. We always lift them clear of the water from a beam reach on down.

      Still, if I trusted them, chine runners would certainly be nice.

      We've toyed with the idea of skegs, and (inverted) T runners as fail-safer. If not bolted, they could be screwed from inboard, so if they did fail, they'ed pull away without (seriously) holing the hull.

      Still, we're 'draft misers', and have never made that leap.

      ****

      Another point you didn't mention was how easily the hull drives... a bit of rocker may well ease our way down the road. But if so, it seems to low benefit at high (construction) cost.

      All this being said, though, each builder makes their own choices based on how value stacks up for them. Rocker can do no harm, and may well pay its way.

      Certainly, the vast majority of flat-bottomed dories and sharpies, as well as a good many scows do employ full rocker.

      Dave Z

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  4. I believe the blunt full forward bow acts somewhat similar to a bulb-bow on larger ships. It will increase prismatic coefficient and it will create a high pressure zone in front of the bow effectively lengthening the hull seen from wave-making drag and theoretical hull-speed. My barge-proa behaves in some ways like it was much longer then it really is. For a given total weight it could be more efficient to "trick" the wave-resistants then making a longer and easier shape. A shorter barge or scow is easier to handle then a longer one, and taxes are often based on LOA.

    Cheers,
    Johannes

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    1. Hi Johannes,

      I'm way over my head, here, but wade in fearlessly! 8)

      There is, in fact, an odd wave phenomenon which can be seen out ahead of SLACKTIDE on very light wind days. As we ghost along, an arc of about a dozen, tiny wavelets precedes us at about 1/3rd our waterline length, with flat water between them and our bow. They arc from one side, across the bow to the other, angling out and away at about 45deg on either side.

      I surmise that we are pushing a small soliton (solitary wave, similar to a tsunami) out ahead of us, creating a 'hard spot' in the water (salmon do this with their tail fins, 'kicking off' the hard spot). It seems possible that this could fool the water into thinking there's a longer waterline length. There may, indeed be ways to enhance this effect (or create it if this is NOT such an effect), though such experimentation is beyond my present means.

      By F1, the wavelets are no longer observable (by us), perhaps lost in noise? Also, we don't see this in every still-water, ghosting situation, so something else might be involved.

      John Scott Russel first observed the soliton (which he called the 'wave of translation') in the 1800s, and developed the associated mathematics while working on the general problem of barge efficiency. [http://en.wikipedia.org/wiki/John_Scott_Russell]

      He also developed the wave line theory of ship construction, which finds the most efficient shape for moving through water to be the 'versed sine' entry, such as seen in Bolger and Roberts barges.

      I mean, this guy was COOL!

      And true that small is beautiful and cheap... if you can find a way to make it faster, too, the world will beat a path to your door!

      Dave Z

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    2. "
      There is, in fact, an odd wave phenomenon which can be seen out ahead of SLACKTIDE on very light wind days. As we ghost along, an arc of about a dozen, tiny wavelets precedes us at about 1/3rd our waterline length, with flat water between them and our bow. They arc from one side, across the bow to the other, angling out and away at about 45deg on either side."

      Interesting observation!
      The very steep knuckle on the first barge-ketch above will probably magnify that effect many times when it is loaded down with cargo. This will not make her win any trans-at races, but she will probably be faster then traditional calculations based on sail-area, waterline-length, righting moment and form-drag dictates. The people sailing and building working sailing barges probably saw this effect and used it to their advantage. With the amount of cargo they were carrying and the amount of power they had available they "should" be very slow, but were obviously fast enough to make a living with, many ears after the great clipper-ships were put out of their business by the age of steam and steel.

      Cheers,
      Johannes

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  5. Is this a scow do you think? http://2.bp.blogspot.com/-LdXwgLPmB-k/UYvo6SBrqEI/AAAAAAAAF0k/cztnANIqBEk/s1600/Swans+and+Sailboats+007.JPG

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    1. Hi Tom,

      Definitely! That's ALMA, the SF Bay Scow Schooner whose lines appear in this post. She's now a Nat'l Monument, and goes out for sails on the bay with loads of admirers.

      If you search images for "alma scow schooner" you'll find lots of great shots of her sailing.

      Dave Z

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  6. That first ship was narrow enough that she might have sailed to weather with enough heel to be meeting the seas with just a corner, rather than the full bluff bow. I sail a little pram myself (Michalak "Jewelbox Jr") and she does indeed sail best respectably heeled. (Tacking in chop is a problem, though, since waves stop her as she comes through the wind level, presenting her whole bow transom to the chop.)

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  7. Hi Jeffrey,

    Puttin' down the V definitely is a key to fast and happy sailing.

    But that first model will drive its hard-knuckled transition from deadflat to bow 'curve' deep... like pushing (at least a partial) plow. Its bow transom may keep clear, but I'm guessing at least half that forefoot stays immersed.

    Planview curvature, as in your JBJR, combines with bottom rocker to lift the ends as it heels. A 'jowly' deadflat, even moreso. Box barges, though, stay full width toward the ends... as the V immerses, the outboard edges at the ends lower with it. To compensate, a box barge must carry its ends higher to clear the water, and keep its bow transom from plowing. (Post coming soon, with drawings).

    I'm a little surprised to hear that you are getting stopped by chop hitting the bow transom, which I would expect to stay relatively clear, even upright. Any chance it's just the low mass/high windage (from the 'BIRDWATCHER cabin') that doesn't let you carry way through the tack?

    SLACKTIDE takes a little water on her low bow transom when it gets choppy, though surprisingly little. At first, we missed tacks (used a backing, 'barge maneuver' for the first year). Then we found we were pinching in higher winds... sailing a skosh more free for better speed carries us through all tacks up to a gale, chop or no. But we've got full, cruising mass, and then some. 8) Larger TBoats carry their bow curves up to ST's deck level (top of her transom), and I anticipate even better progress in a chop.

    Dave Z

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