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#6 Third Edition:
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Inca's Balsa Log Raft

The family of Guaras:
Dagger-boards, centerboards and Lee-bords


The art of sailing is to beat close hauled to the wind


 

The curved yard is still seen on the photos 70 years later - so it is probably not occasional
Note that the Guaras are concentrated as groups in both ends of the vessel
- that we could interpret, as a Guara-raft don't need more keel in between
[ img - raft1841.gif ]
Drawing from Ecuador 1841

In South America the ship development was different.

They knew the dugouts and expanded canoes, as they used on the rainforest rivers, but not on their Pacific ocean, there they had other means. Their balsa wood is a wonderful material - the lightest wood in the world, and therefor instead of digging out the trunks, they tied more of them together and got a raft with a rather good carrying capacity and impossible to capsize.

A raft of trunks is a fine vessel and could have a long and fat central trunk as stem and keel, but equipped with sail they plunged in some keel-boards between the trunks to obtain a more stable course. Here they discovered the Guara-steering, but not the rudder. They could sail over all the ocean with their heavy loaded, but slow moving crafts, and they were beating so effectively against the wind, that they without greater problems could return to their starting point. There they were in their development when the Europeans came and took over the control. The Europeans recognized the men of the coast societies as efficient seamen and sailors, but they never understood how the Guaras worked.
For the Europeans the function of Guaras has been a mystery in hundreds of years: The outside world simply hasn't understood how to use these daggerboards, but nevertheless the South Americans have used them daily on their ocean sailing rafts.

The conditions for any sail-powered vessel were always:
LOW forward resistance together with a HIGH lateral

Leeboard - the family to Guara

The Guara /daggerboards wasn't totally unknown for the Europeans. The fun is that similar system - as cousin to the Guaras - has been used several hundred of years in the northern Europa in the form of leeboards.

The Dutch did not invent leeboards. They saw them being used in the Far East during their discovery voyages in the early 1500s. In China they have a documented experience of more than one thousand years.

The result of this learning we saw on the Dutch rivers, canals and inland waterways, the German, Frisian and Waddensea coast up to South in Denmark. All over, up and down the coast of East England, on the rivers Thames and Humber we had these 'daily work horses' in form of flat-bottomed and shallow drafted boats as Sloop, Barge, Keel, Ewer, Tjalk, Seascow, Botter, Kaag, Kahn, Evert, Curonian et cetera - all without a keel. Ewen far away, on all the shalow lagoons along the Baltic coast of Germany and Poland up to the Curonian lagoon between Lithuania and Kaliningrad, they sailed with their flat bottom and leeboards.

Even if they perhaps will do better with leeboard ALL the pictured flat-bottom vessels can beat against the wind.

Song is Contemporary with the South American rafts
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13 century junk drawn with two lee-boards

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Thames barge resting by low tide
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fore and aft rigged English Thames Barge
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Humber Keel recognizable by its square sail
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Curonian fishing boat
showing her shallow draft
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German flat-bottom resting on shore
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Dutchman landed at a sunset shore
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Danish Waddensea Evert
showing her flat-bottom
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Danish Evert landed in Waddensea
[ img - lemsteraakLiftingLuffLeeboard.jpg ]
Dutch Lemsteraak showing how a luff board will heel out of water

Unlike the Guaras, the leeboard is mounted outside the hull and normally one on each side - obvious for not to affect integrity of neither hull nor hold - and they are placed midship, very central on the side of the 'Center of Effort' of the sails, for not to disturb the effective trim of their crafts, as are steered by rudder.

LEEBOARDS were principally used to stabilize the course by reducing side-sliding of flat-bottomed sailboats, as couldn't have any natural keel - mainly because they needed to sail, land and beach in shallow waters or on riverbed by low tide. Up to one compass point = 6 degrees closer to the wind, than the same boat with leeboard up - is told us.

But the sailing people learned that leeboards could be a great help as pivot-point turning through the windeye under a tack. And with a leeboard hanging several feet below the ship-bottom, they had too a good sound-warning against banks and ground, when sailing in shallow waters.
The Humber Keel with her long and deep slap side was equipped with leeboard, but not because of need for keel - the slab side did it and specially when loaded down - it did it too well that she was difficult to turn in narrow waters. Therefor her main reason for leeboard was the get a turnpoint in the tack - and of course a sonic warning for low water, hanging one yard under the bottom.

We have never heard of more leeboards mounted on same side; and therefor the Europeans never discovered the Guara steering qualities: to balance the side-sliding between for and aft - but in China they did.

A leeboard explication
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CE=Center of effort versus CLR=Center of Lateral Resistance

Somewhere we found an old thumb-rule for dimensioning of leeboards, saying that the underwater size of this board should hold 3-5% of sail area
- but saying nothing around shape, nor length nor breadth -

From leeboard to centerboard

The outside leeboards were used in centuries until our evolution in ship-technology was able to construct safe and reliable wells inside a hull, what happend around 150 years ago. Then leeboards in some yacht-designs entered from both sides and joined in one single board in center - called centerboard of course - more as ONE adjustable keel and easier to handle than TWO leeboards on same boat. Later on the centerboard too was equipped with a counterweight.
Leeboards are hinged and centerboards too, whereas a daggerboard is a board pushed down in a sheath like a dagger, and has therefore to be of manageable size and weight - why only used in smaller sailvessels. Guara is mostly to compaire with a daggerboard.
Inside her well for living eels this eel-drifter has mounted a centerboard.

Neither here, we have never seen a boat with more than one centerboard - other than the trial-dinghy named.


The steer-oar tricks as the vikingship sailors have forgot

The steer-oar of the Vikings

The rudder of a Viking-ship is mounted in starboard side. Therefor the name starboard is a viking contribuition to the English language.
The Viking helmsman knows perfectly, that his ship with wind from port will heel and dip deeper its side-mounted steering oar as therefor react better - in contrast to a Starboard wind, as will lift the steer-oar more out of water.

The steer-oar on viking-ships is considered as a rudder, but due to its design and place, it too has some qualities as a leeboard - just as the Guara.

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a Viking steer-oar,
as we can tilt
Beaching:

Viking ships too can tilt their steer-oar around the withy, and that they normally do in shallow water and when beaching. Laying the tiller down to lift the oar from the bottom - and then land on the beach.

Tacking, change windward side

When changing leg every ship can either tack up through the wind-eye - or wear the other way around - turning her 'behind' against the wind - and which one of the two turns you should use, depend of your rigging and sails.
Mono-masted square-sailors have no difficulties to wear, they turn as a cup on its saucer, but tacking through the wind-eye can give difficulties, if the vessel haven't sufficient headway in her run-up to reach the wind-eye. With no foresail and without streaming water around the steering oar the boat will be driven backwards again, and the manoeuver have to be repeated.

There are some small tricks:
1): On smaller boats, you can use an oar in the lee-side to row the boat through the eye.
2): You too can let some crew-members to go forward to weight down the bow of the craft. In this way they move forward the CLR = Center of Lateral Resistance as play together with the CE (center of effort) of sail as then may blow downwind, and bring the boat up in the wind eye.
3): Theoretically there is this third trick, as I still never have seen carried out. Let the helmsman tilt the steer-oar out of water so the aft-end slides easier away downwind for the mast - and then swing over the yard, dip down your steer-oar again and sail-on on the other bow.

[ img - dreje-bi2.jpg ]
single masted square sailor 'heaved to'
Note: The same trick of moving the 'live ballast' of men forward, in some cases too can get the boat to beat higher to the wind - moving ahead the CLR.
Too yacht-skippers practising rudderless sailing use the trick to move around their living weight.

Heave to

That is a maneuver to stop the boat with sail still hoisted - to wait for somebody or to pick something up. With the sail hoisted the boat behave more calm and under control - laying waiting without forward movement but drifting slowly sideways under press of the wind.
The manoeuver for mono-masted is in general: tacking up in the wind eye, go through and get back-wind, and then - without to turn the yard but only rudder - let the boat go astern until she stops with full back-wind in the sail - yard still along and wind directly abeam. If the boat is well trimmed she will stay there, drifting sidewards.
If not trimmed, the boats with steering oar have the option to tilt her steering oar to change the underwater body and keep a balance.
This option the square-rigged Nordlandsboats can't use, because they are equipped with stern rudder (pintle and gudgeon) and not a steering oar - but of course here too a simple rowing oar could help to keep the balance.


It looks like a viking steer-oar, but the sailing pacific double canoes employ the same principle as the Guara rafts (same ocean). We are using a handheld paddle for steering, but NOT twisting it; we keep the paddle on leeward side of any of the hulls, lowering or lifting it - or tilting it - to CONTROL THE SIDE-SLIDING. The paddle itself keeps to the boat pressed by wind and water.

Another photo of Dirch with his 'astern leeboard'   >>>

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The inevitable Leeway

Rule for calculation:
The real course is the result of steered course with leeway added
(whatever leeway is due to wind or current)

Wind abeam on a vessel give leeway, that know every seaman, and that phenomenon is applied for every craft - perhaps with exception of submarines, wheeled land sailers and iceboats.
The captain on the cruise liner know it, and that is why his ship is supplied with trusters for and aft to compensate. Too the freight skipper know it. He has only one propeller and one rudder, and therefor he is very careful, when he is entering in a narrow harbor entrance with the wind across. He probably will not do that without a tug-boat for assistance.

[ img - afdrift+styret-Kurs-A.png ]
Sail-ships generally are trimmed for wind abeam, but they can't escape leeway. In some special situations we directly make use of this broadside drift - as for example the eel-drifter as the name indicates work drifting, or when a square sailor 'heave to' - with sail hoisted wait drifting.

When we are navigating a sail boat, we have to calculate with leeway, and the side-drift depends alone of the strength of wind and the area of sail and hull against the lateral Hydraulic Resistance. The stronger the wind, the more leeway - and of course: more sail more leeway. Leeway simply is a result of the wind's broadside forces against the Lateral Hydraulic Resistance of the hull.

Where is a square-off-raft "pointing" ?
Along the diagonal where she sail - or
along the classic centerline ?
[ img - afdrift+styret-Kurs-B.png ]

On a square-off raft the common expresions are a bit confused. On such a raft as use the one corner as stem we could have doubt around where the vessel is "pointing" - along centerline or along the diagonal?
Nevertheless if the sail is adjusted for diagonal sailing a skipper with a "square-off"-raft can sail along a diagonal - but he still have to calculate and add some leeway. That "diagonal sailing" was the main problem on lost raft raid 2015.


We can calculate the side drift as something constant
- something as we always will have.

If we check up the side-drift, it is rather constant per hour or minute and it is rather independent if we are sailing along or not. The wind-generated leeway we can't change much, unless we have a centerboard, leeboard or something similar, as can increase the lateral (broadside) water resistence.

What is now our task, is to sail as far ahead in relation to this permanent drift - that means to make the leeway to something relative smaller.

afdrift+styret-kurs.gif
Fig-1

afdrift+styret-kurs2.gif
Fig-2

afdrift+styret-kurs3.gif
Fig-3
Fig-1): When sailing with wind abeam we will get leeway - this leeway we can compensate beforehand by steering more against wind - if the sail permit.
What we normally do - nearly independent which vessel we are navigating - is, to adjust the steered course closer to wind, so at least it seems as the real course goes more directly against our wanted destination.
For a raft, as not generate speedy streaming water, we adjust our Guaras, so the raft point up more against the wind - what means that the drift of for-end go in balance with the drift of aft-end. Then subsequently we adjust our sails for this course.

Fig-2): Accepting that the drift is near the same all the time, then it is only the headway as can improve (or reduce) the total performance - what will relatively reduce the leeway.
That we do by adjusting the sails. But as said, sails have some limits, as among other things depend of what type of rigging. 'For & aft' rigging for example is known to go higher to the wind than a square-sail, but that only have importance, when we are beating against wind. With wind abeam both types of sails more or less do alike.

Fig-3): On the other hand, when we reef a sail, we get relative more leeway, and that we always have known.
What happens is, that when we reduce the sail, then we reduce the headway together with the drift coming from sail, but we don't reduce the drift coming from wind press on hut, hull and rigging - so therefor the drift altogether gain more relative to the headway, with the result, that we can't go so high to the wind.

Some play with numbers:
If the wind on our vessel (boat or raft) gives a broadside drift of 200 meters an hour, (and that we can measure nearly statically), then the task is to advance most possible in this hour. If we move our craft with 1 knot ahead (as a Kontiki-raft), that will bring us about 2000 meters ahead, while sailing the same ship with 6 knots, we will reach 10 kilometers. When we are calculating our drift in degrees, we will get 6 degrees respectively 1 degree leeway.
- with a raft you only can expect 1-2 knots -


Geometrically it is so, that if a skipper need a mean course directly against the wind or into his no-go zone, he has to tack in zigzag. But if he or his craft not even can point less than 90 degrees, then he can't advance, and he should wait for better wind - or he could take the trade winds around the Globe

Why it is important to beat high to the wind:
If skipper is able to beat 80 degrees to wind, his sailed distance will be six times the direct distance
and 80° should every square-sailer be able to do
[ img - ztack80.png ]
If 70 degrees - then 3 times, as is far better,
and many square-sailers are able to that
[ img - ztack70.png ]
If he can make 60 degrees - then only double distance, but that we only can expect done by the best square-sailers
[ img - ztack60.png ]

Behold - more boards - leeboards, daggerboards, centerboards or luff-boards
If we want to go even higher to the wind we of course can mount more boards on a steer-neutral place in the mid of the ship, in the same way as we mount leeboards on the many other flat-bottomed crafts
- and doing this we perhaps can expect to reduce the side-sliding with some degrees, as they on monohulls say they can mounting leeboards.

The art of sailing is to beat against the wind.
Opposite monohulls; on a raft we don't need to hang any board on outside. Our raft is wide and build of more trunks, and we can make use of this and plunge in Guaras in the cleft between any trunks - where we like - and not only along the main trunk.
Well, the reason why we in all cases will propose the outermost cleft is the same on all ships: The central area will be difficult to access because of hut and cargo - whereas the outer rim should be more accessible.
So if we apply a board plunged down in the outermost extreme trunk-cleft in lee-side in the neutral zone near mast, it should be OK and work as a leeboard.

But if we consider the weathercock principle and combine the wind-vane with our side-board, we of course still can expect our raft beat better - but too obtain a certain directional stability. That means that we should change out the leeboard with a Luff-board - in the windward side. That is possible, because our board plunged in between trunks will not flap out nor break its suspension, as it would do on a Dutch Lemsteraaken, a Humber Keel or a Thames Barge (a reason why those types of crafts didn't use Luff-bord). A raft neither will heel and lift a Luff-board out of water.
Therefor we recommend to mount more Guaras between the two outermost trunks in wind-side and in this way activate the weathervane principle as will help to stabilize your course.
For a catamaran that could be a classic lee-bord on luff hull.

That Luff-board trick is expected to give more stable course and together with less leeway.

We know a few things with some certainty:
   1): Larger distance from hydraulic centre - the turn point - to wind centre of sail+rig bring less yaw = shear off - what means less swing-out of our weathercock.
   2): More Guaras plunged in give more keel and therefor less lee­way together with more stability in sail direction - but otherwise: more Guaras reduce the sensibility of each steer-Guara.
   3): A weathercock is a self correcting instrument - a Guara raft too.
Both compensation by balancing the press on fore- and aft-sails (on boats) and compensation by Guaras on rafts give a stable correction as will keep a mean pointed course in relation to the wind - just as a weathercock - a windvane.
Of course we on the ocean will get rolling and yawing sailing up and surfing down the waves, supporting gusts from the wind etc. but the raft just like our weathercock will go back and stabilize its pointing, dependant alone of the wind direction and the hold in water defined by the Pivot-point of the Guaras.

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Lima - November 2017