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Tumblehome, stability, and performance

bobmcgov

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Classic30

Tumble home does not result in a loss of buoyancy until the tumbled home section is immersed. Righting arm is reduced with increased immersion/increased heel. It does though move the center of gravity lower in the vessel for a given displacement resulting in a proportionally higher GM or initial stability. Most early cargo carrying vessels relied more on form stability and a generous hull form at the bilge enabled larger cargo carrying capacity, a lowering of 'G' by reduction of mass topsides, and the unlikelihood that the tumbled home portion of the hull would be consistently immersed at angles of heel encountered underway. Like every design question, it's a matter of trade-offs. I suspect that the more modern yacht has less imperative to reduce weight topsides due to the reduction of weight aloft made with modern materials for spar construction among other things. And I'm giving short shrift to the discussion of form stability versus ballast conditioned stability.  

sailingdog

I seem to recall that for a brief time certain rating rules measured beam on deck, and tumblehome was a way to add 'unmeasured/unpenalized' beam. That said, a nicely drawn tumblehome hull looks pretty good - the Ranger 28 being one good example.  

Boasun

Jeff_H said: In the case of the IOR era the rapid increase in stability as the tumblehome hit the water and the rising vertical center of gravity associated with rolling out, was seen as contributing to their notorious excitation roll characteristics and poor downwind controllability. Click to expand...

True but historically Tumblehome was used before they had gun decks. A properly designed vessel may have a slight to moderate tumblehome. This is used by the builders/designers to strengthen the hull. Reducing the racking of the seas on the hulls. But like a lot of good features in design work.... people carry it to the extreme and ruin a good thing.  

Funny thing...I was never attracted to those hull shapes... Now I look at them...they bring a certain "classic" look....I look at them now...some Swans from the late 70's and early 80's... Strange how things change in life....I have "negative" tumblehome eheheheheh starnge how design evolved, isn't it???  

JohnRPollard

JohnRPollard said: Whenever anyone mentions tumblehome, I invariably think of the S&S designed Catalina 38, from the late-70's/early-80's, as the archetype in fibreglass: Click to expand...

The Picture of the Sheerwater illustrates an eliptical transom. Ellyptical tansoms are generally thought to have come into being strictly for pragmatic reasons. In the days when mainsail booms and mainsheets hung over the transom, and fishermen hauled nets and traps over the side, the rounded corners of an ellyptical transom kept lines from getting hung up on the corners of the transom. Elliptical transoms had little or no impact on the hydrodynamocs of the boat, but they surely look beautiful to the eye. Jeff  

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Adirondack Architectural Heritage

Reuben Smith’s Tumblehome Boatshop

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High‐end restoration and new construction of classic wooden boats is the dual goal of Reuben Smith’s Tumblehome Boatshop. In 2015 Tumblehome received an AARCH Preservation Award for their conversion of a garage building into an industrial-chic center of concrete, steel, and wood. Smell the fresh wood shavings in an active boat shop, watching as vessels are brought to life or back to past elegance. Enjoy fresh muffins and coffee as you wander through the changing exhibit/storage space in the modern building attached to the shop called the “Boathouse”, seeing custom speedboats or historic race boats and runabouts.

Owners Reuben and Cynde Smith will be on hand to speak about the buildings and their work as craftsmen.

The tour begins at 10 a.m. and ends around 12 p.m.

TOUR REGISTRATION INFORMATION

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Here’s how the destroyer Zumwalt’s stealthy design handles stormy seas

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WASHINGTON — After years of stability questions about the hull design for the U.S. Navy’s new three-ship class of stealth destroyers , the commanding officer of the lead ship, USS Zumwalt, is satisfied: It handles the seas as well, if not better, than previous classes of surface combatants.

While underway last spring, Capt. Andrew Carlson and the crew of Zumwalt took the ship to Alaska, where they got to experience some heavy seas.

"We took advantage of a storm up near Alaska that presented us with Sea State Six conditions,” said Carlson, referring to sea’s waves between 13 and 20 feet high. “All told I’d rather be on that ship than any other ship I’ve been on.”

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The seas were so high at one point he called down to his executive officer to tell him the ship had hit Sea State Six, but his XO said that based on the rolls he was feeling in his cabin, it couldn’t be more than Sea State Three, a more tranquil 1- to 4-foot height measurement.

That’s due to the way the tumblehome hull design was built, righting itself much more quickly that previous classes of ship.

“You definitely have to get used to the roll, which is very short compared to other ships,” Carlson said. “For those of us who have been on cruisers, especially up top, you kind of lean over 15 degrees and you wonder if you are going to come back. We didn’t experience any of that. As long as you get used to the finer oscillation, it really handles very well."

Carlson, who discussed the ship’s design with Defense News at the annual Surface Navy Association meeting, said traversing through rough weather was part of ongoing stability testing, which he said is about 60-70 percent complete.

“The biggest known variable for these stability tests is the weather,” Carlson said. “So we’ve had days where we wanted to do calm water trials and there are white caps, so its not calm enough for us to get the right data.

“In this case we were looking for bad weather and we were able to [a] leverage storm system up near the Gulf of Alaska that had substantial wave action hundreds of miles away from that — still tenable without any risk to the ship. And this happened over several days, so every watch team got to drive circles, drive straight lines and measure out how the ship responded.”

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Capt. Andrew Carlson, commanding officer of the USS Zumwalt (DDG-1000), speaks during a news conference aboard the ship at Joint Base Pearl Harbor-Hickam on Tuesday, April 2, 2019, in Honolulu. The ship's arrival marks the first time Zumwalt has visited Pearl Harbor. (Craig T. Kojima/Honolulu Star-Advertiser via AP)

‘Tokyo Drift’

The quick-righting hull is something a crew gets in every sea state, not just in stormy seas, he said.

“It’s just a much tighter periodicity in the roll, and a lot of that has to do with the rigidness and the stability of how the ship is built,” Carlson said. “But that’s something we’ve experienced in other sea states. You don’t have to have extravagant wave action to realize that the ship rights herself very quickly.”

“It was an odd feeling at first,” he added. “The first time I was on the bridge as a newly reported sailor, not yet assumed the job of executive office, we had some speed on and the officer of the deck ordered a large rudder.

“And I intuitively thought, ‘I’m going to need to lean into this turn’ — you almost fall the other way because the ship doesn’t heel in the same way. Some of that is the hull form, some of that is the relative location of the rudder stops, the size of the propellers.”

It also took Carlson some time to get used to how Zumwalt handles turns.

“She generally slides more than cuts into the water,” Carlson said. “It’s actually more fun. There’s a little bit of ‘Tokyo Drift’ going on where you can really get a faster turn on with harder rudder, but still very stable. It’s not like you are tumbling around," he said. “When we were up in those big waves, the bow was piercing through; you’re getting some of that water coming up. You still pitch, it’s just not nearly the same."

Another feature familiar to sailors on the surface combatants is also conspicuously absent: The shimmy and shake that comes when the nose goes into a wave and water rushes off the bow, through the bullnose and around the sonar dome.

“There’s none of that: You pitch up and you pitch down,” he said. “It’s a better ride.”

David B. Larter was the naval warfare reporter for Defense News.

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Anatomy of a Canoe: Essentials of Good Design (Canoecraft Excerpt)

Ted Moores leans on the ladder of a dock, with two examples of woodstrip canoes beside him (recognizable as similar to the cover of Canoecraft to fans of the book)

The following is an excerpt from   Canoecraft  by Ted Moores.   Click here to order the complete edition.

Table of contents, a canoe in perspective, the elements of performance, hull contour, compromises and conundrums.

It is doubtful whether any first-class canoe is the result of any one person’s study. The builder’s shop is the mill, he is the miller. The ideas of others are grists. – J.H. Rushton

One does not have to be a naval architect to understand the basic principles of canoe design. They are relatively simple, yet vitally important – especially to the builder.

The curves of a well-designed canoe are its calling card – a proclamation of the kind of paddling it does best. At one time, the lines of the slender, double-ended craft were directly traceable to a particular locale or people. The curious profile of a Newfoundland Beothuk canoe was a far cry aesthetically, functionally and geographically from the sturgeon-nosed craft of British Columbia’s Kootenay people. 

Within the limits of materials and technology, both native canoes and those built by the early whites were traditionally shaped to conform to the kind of water they plied and to the job they had to do. But with the advent of mass production, that connection was broken. In the post-World War II era, canoes were more often designed to conform to the demands of new materials than to function in a specific environment. Efficiency in the water took a backseat to efficiency in the factory.

Commercial designs have vastly improved in the past 15 years or so, as the emphasis has shifted back towards performance. Even so, by building your own canoe, you gain unique control; with the design and construction decisions you make, you can reestablish that perfect harmony among canoe, paddler, and water.

There is no point in expending energy to build a craft that is going to paddle like a barge. At the same time, every builder, designer, and paddler has his own version of the perfect canoe. The following section bares our personal biases; you can find others by referring to the books listed in Sources.

The key to sorting through the maze of designs is to determine what you expect of your canoe. Where will you most often paddle, for how and with what gear? Most paddlers face a range of circumstances. The challenge is to select a design that meets most needs most of the time.

If your experience in canoes is limited, go to the water to test these principles where they really count. Examine hull contours and paddle different canoes to discover what suits your style best. Your woodstrip canoe will be a thing of aesthetic beauty, but understanding design will assure that it is satisfyingly functional as well.

When a canoe is taken out of its watery element and projected onto a drawing board, it can be reduced to three views – profile, body plan and plan view.

The profile view (see illustration) shows a canoe from one side, as if it were cut in half lengthwise. This perspective describes the accurate length and depth of the boat, its sheer-line (curve of the gunwale, or top edge), its keel-line (curve of the hull, or bottom edge), the shape of its bow and stern and its waterline length (hull length that is wetted when the canoe is in the water).

The body plan (see illustration) shows a canoe from the end, as if it were sliced crosswise at regular intervals, or stations, the shape and dimensions of which are each represented by a single line. Each cross section shows the accurate width and depth of the canoe at that point, as well as the shape of the hull bottom and the shape of the sides. A centerline drawn perpendicular to the waterline splits the cross section in two, but since each half is identical, only one half is shown in the body plan.

The plan view (see illustration) shows a fish-eye perspective of the canoe from directly underneath the boat, as if it were sliced end to end at regular waterlines. Each lengthwise section shows the true length and width at that level, as well as the contour from its maximum width to the point at each end. This describes the path the water must take at various levels as it moves from the entry line at the bow to the exit line at the stern. When the slices are superimposed over a common centerline, the plan view also indicates whether the canoe is symmetrical (bow and stern halves are the same shape) or asymmetrical.

Hand-sketched diagram showing parts of a canoe

The parts of a canoe are common to most watercraft.

Each of the many physical elements illustrated by the three views has a profound effect on a canoe’s performance. Although they are discussed separately below, none of them acts in isolation. Each affects the others to some extend; in a well-designed canoe, they function in delicate balance.

Hand-sketched diagram showing a canoe in profile view

The  profile view shows a canoe from the side, sliced in half lengthwise, illustrating the top and bottom curves as well as the length and depth of the canoe.

On average, the center half of a well-designed hull provides 75 percent of its stability and carrying capacity, while the end quarters function primarily to part the waters at the bow and bring them back together at the stern. Obviously, a longer hull will carry more weight, but length also affects speed.

Generally, the greater the waterline length and the higher the ratio of length to width, the faster the canoe and the easier it is to paddle. This is partly due to the physics of waves and partly to the fact that, in comparison to a short, wide hull, a long, narrow hull rides higher, with less wetted surface, and thus generates less friction against the water. A long hull will also track (hold its course) better than a short one will, but it will not turn as easily.

Hand-sketched diagram showing the body plan view of a canoe

The body plan is an end view of the canoe, sliced crosswise at regular intervals, bow to stern, with the contours superimposed in sequence over a common centerline. It illustrates the canoe's depth and width.

Hand-sketched diagram of the plan view of a canoe

The plan view shows the hull from below, sliced lengthwise at regular waterlines. It illustrates the hull shape and the canoe's width and length.

This is the maximum width of a canoe. With a narrow beam, less effort is required to push the water aside, and less friction is created by the hull surface. But, although a wide canoe generally paddles slower than a narrow one does, it has greater carrying capacity and is more stable when loaded to its design capacity.

Beam may be the same throughout the depth of the hull, in which case, its sides are plumb (see hull contour , below). But if the maximum beam occurs at the gunwales, the hull is flared . Most often found on narrow hulls, flared sides afford good “final stability.” The hull becomes more stable when it is loaded down, because it becomes wider the lower it sits in the water. Flared sides also deflect waves.

When the gunwale beam is narrower than the maximum beam, the sides are tumblehome (they “tumble home”). Tumblehome is usually found on wider hulls: the reduced gunwale width allows the paddler to reach over the side easily without sacrificing good carrying capacity. The arcing sides also help stiffen the hull. Although tumblehome does not affect initial stability, it can result in very poor final stability when too extreme, especially in combination with a wide, flat bottom.

Hand-sketched diagram showing elements of canoe depth

Determining the depth of the canoe: Freeboard, the distance between the gunwale and the water, varies with the load the canoe is carrying.

The depth of a canoe is measured amidships from the gunwales to the bottom of the hull. This can range from 10 inches in a little solo canoe to more than 24 inches in a freighter. Depth is also measured at the bow and stern, from the top of the stem to the lowest point of the keel-line.

Freeboard , another measurement of depth, is the distance from the water to the gunwales. Freeboard affects the seaworthiness of a canoe: high sides will make it susceptible to wind, reducing speed and controllability, whereas low sides will render it susceptible to swamping in whitewater and waves.

Predicting the freeboard of a design when the canoe is fully loaded can be done several ways. When “capacity” is listed in canoe specifications, it usually refers to the weight that can be loaded into the canoe while retaining 6 inches of freeboard. “Design displacement” refers to the weight that will lower the canoe to its design waterline. As you study different plans, watch for figures that indicate pounds per inch of immersion. Ultimately, this is more meaningful than capacity is and will give you perspective on how a particular hull will handle loading.

Hand-sketched diagram showing various hull shapes

Top: Up to half the length of a well-designed canoe is devoted primarily to parting the water at the bow and returning it at the stern. The longer the canoe, the faster it is. Above: The placement of maximum beam on the side of the hull determines the shape of the sides and the canoe's stability, speed, and carrying capacity.

More important than depth, beam or length is the way these measurements are drawn together to form the hull contour. How this shape moves through the water is the key to canoe performance.

A canoe has a displacement hull. It is basically a moving trough, dividing water at the bow and replacing it at the stern. Its efficiency depends on the amount of friction created by the hull surface meeting the water and the smoothness with which the water is displaced around its form.

Hand-sketched diagram showing hull shapes and their stability in rough water

The contour of the hull below the waterline determines the efficiency of the canoe as well as its stability in rough water.

A semicircular, or round-bottom , hull produces the least wetted surface, but its tippiness makes it practical only for flatwater racing shells.

A flat-bottom hull has the greatest wetted surface and is capable of carrying large loads. It can also turn quickly in every direction, making it appropriate for whitewater, where high maneuverability is a priority. This skidding action, however, means tracking can be difficult in anything less than glassy waters, and even then, flat-bottom hulls are slowed by high friction.

Since it is buoyant over a large surface, a flat-bottom hull feels the most stable when first climb in but remains so only in calm water. In rough water, the flat, buoyant hull follows the profile of the waves and can turn turtle suddenly when tipped past the sharp turn of its bilge. A flat bottom may be justified in freight canoes but is unsafe in recreational craft on anything but flat water.

The shallow-arch , or semi-elliptical, hull contour is a good compromise between the round and flat bottoms. Its domed shape helps stiffen the hull, which is especially important with lightweight construction techniques, and reduces instability in the bilge area. In addition, waves tend to slide under the boat.

This hull feels “canoey,” with good initial and final stability. Because such hulls take less abuse from heavy waters, naval architects often characterize them as “sea kindly.” A shallow-arch hull will also track better than will a flat hull. Because of its seaworthiness and average tracking and turning ability, this contour is the starting point for most general-purpose touring or cruising canoes.

A shallow-vee contour takes the hull deeper and sharper into the water and produces slightly more wetted surface. Like the shallow-arch hull, the shallow vee affords a high degree of final stability. But it tracks better, since the vee shape functions like a keel, keeping the canoe on course. It is less responsive in turning, however. Because the shallow vee cuts cleanly through waves, with little pounding or skidding, it is especially appropriate for sailing and lake canoes.

Most hulls employ a combination of these forms. For instance, a cruiser might have a deep-vee bow to part the waters efficiently, opening gradually to a shallow vee, then a shallow arch to pass the waves cleanly along the hull, then narrowing back into a deep vee at the stern. Such a design would combine seaworthiness and directional stability with good maneuverability. It would also offer reserve buoyancy – extra width at the vee sections when the canoe sits deeper in the water.

Separate keels are the subject of some controversy in canoe design. They do add a measure of stiffness and protection to the hull bottom and will be much appreciated when paddling through a crosswind on a lake, but that same keel will be roundly cursed when you try to maneuver through rock-strewn rapids.

As a general rule, a shoe keel (a keel generally 3/8 inch deep by 2 to 3 inches wide) is a good idea for protection on a river boat, while a deeper keel is appropriate on a lake canoe, where maneuverability is less important than tracking ability. Keels should be avoided on whitewater canoes, since they get hung up on obstructions and inhibit the sideways movement critical to dodging through rapids.

The keel-line of a canoe also affects maneuverability and directional stability. A straight keel-line from stem to stem produces a fast, easy-paddling canoe that tracks exceedingly well but turns poorly.

Hand-sketched diagram showing various types of canoe rocker

Even without a keel, the profile of a hull bottom strongly affects performance and the way the canoe rides out rough waters. Keel-lines range from the razor's edge of a racing cruiser to the extreme rocker of a slalom canoe. Recreational canoes fall somewhere between.

A keel-line that curves upward from the middle towards each end of the canoe is said to have rocker . Essentially, rocker allows the canoe to pivot on its midpoint. The more rocker on the keel-line, the shorter the canoe’s waterline length and the easier it turns and rises over waves. Too much rocker forces the center of the canoe to support most of its weight, driving it deeper into the water, increasing displacement and friction and decreasing speed.

Rockers can range from moderate lift in a cruiser to the banana-like profile of a competition slalom canoe. Poorly made or old canoes sometimes develop reverse rocker, or hogged keel-lines, which inhibits performance.

Rather than a fully rockered keel-line, a canoe can have a slight uplift just at the stems. In a loaded boat, this allows enough of the hull to ride in the water for good tracking, but with the bow and stern riding slightly above the waterline, maneuverability and reserve buoyancy are improved. 

The profile of the bow affects performance as well as the line of the hull body. Some bows rise vertically or on a slight incline, yielding a fairly straight sheer-line and maximum waterline length. This inclined, or plumb , bow forces the sides of the canoe to flare. The greater the incline, the more the sides must flare.

Most traditional canoe bows, however, rise up out of the water and curve back slightly towards the paddler. This recurve , a logical extension of the rockered keel-line, reduces the area exposed to the wind for a given waterline length. But as the bow curves, it puts tumblehome into the sides, reducing reserve buoyancy.

To compensate for this, extra height is often added at the stems. Extreme recurve, with a sharply rising sheer-line, makes the canoe more susceptible to wind and adds some unnecessary weight, but the trade-off may be worth the beautiful sweeping lines.

The entry line of a canoe – the shape of the forward point of the bow that cuts the water – plays a large part in its efficiency. The smoothness with which water is displaced around the hull affects both speed and the amount of effort required to attain it.

A canoe that carries its fullness well into the ends must quickly push aside a large volume of water, which tends to slow down as it moves along the hull. Thus the canoe tends to plow through the water.

On the other hand, a hull with a fine entry line moves the water aside more slowly. Because the displaced fluid has more time to get out of the way, the paddler exerts less of his own force to move it. The fine lines part the water neatly, producing little spray and a small set of waves that accelerate naturally along the hull.

Fine entry lines are desirable under all conditions, albeit in varying degrees. A flatwater cruiser should have the finest entry, whereas a whitewater canoe must have its fullness carried as far forward as possible, without disturbing the fine entry.

Although traditional canoes are generally symmetrical in shape, some modern designers have abandoned that principle. In an asymmetrical design, the beam is placed slightly aft of center, creating a longer bow. Paddling and tracking becomes easier because of the fine entry of the long bow and the extra buoyancy in the stern quarter.

Hand-sketched diagram showing the effect of a canoe bow's shape on water displacement

Top: A plumb bow forces the canoe's sides to flare, while traditional recurved bows result in tumblehome sides. High recurve is traditionally attractive but can make the canoe susceptible to wind. Above: Fine entry lines part the waves more smoothly than a blunt-nosed bow that plows the water. The result is greater speed with less paddling effort.

Between the extremes of the blunt-nose, flat-bottom freighter and the stiletto racer, infinite variations in canoe design are available. At the same time, however, there is no ideal form. Each of the principles discussed above can be manipulated for specific results, but the gain of one advantage inevitably entails the loss of another. If you opt for tracking, you will sacrifice maneuverability, while the extreme rocker that offers optimal maneuverability will rob your canoe of tracking ability.

Even within each design variable, there are no absolutes. Final stability is a prime concern if you are out for a paddle with the kids, but it is a low priority if you delight in the solo canoe “ballet” of Bill Mason. And finally, no matter how function a well-designed canoe may be, it must also be visually pleasing, balancing practicality with beauty of lines.

The flexibility of canoe design, however, is its own reward. All these disparate elements can be orchestrated in several different ways to produce a variety of canoe prototypes well suited to different requirements. If there is no such thing as the perfect all-purpose canoe, there are individual types that do specific jobs very well.

A cruising , light-tripping or general-purpose, canoe should have a keel or vee end sections, a fairly straight keel-line and a fine entry line for good tracking and efficient paddling. It should have a shallow-arch or shallow-vee hull with low stem profiles. Asymmetrical designs are appropriate. Overall length can range between 14 and 18.5 feet, with at least a 12-inch depth and a beam between 30 and 34 inches.

A wilderness , or tripping, canoe must meet all the challenges of extended bush travel – large lakes, shallow streams, whitewater and portages – and still be able to carry sufficient gear. The hull should be as full as possible towards the bow and stern without disturbing the fine entry, with a slight uplift or rockered keel-line for maneuverability in rough water and a shallow-arch contour. A bit of tumblehome in the sides is ideal. The hull should be keelless or shoe-keeled, and weight is a definite consideration. Competent wilderness canoes are at least 16 feet and as much as 18.5 feet long, with a 12-to-14-inch depth and 34-to-36-inch beam.

A whitewater , or downriver, canoe should have a shallow-arch to flat-bottom hull, well rockered for easy turning and with a good lift at the ends so that it can ride through heavy rapids without taking water. Moving the bow seat back somewhat will improve this ability. Keels are undesirable, unless a shoe keel is considered necessary for protection. In any case, a whitewater canoe has to be strong enough to withstand inevitable encounters with rocks. Decks should be long and gunwales wide enough to shed water, with tumblehome sides to accommodate the beam. The consideration of weight has to be balanced against durability. Dimensions are similar to those for a wilderness canoe, although depth should be about 14 inches.

The design of a solo canoe depends on the individual canoeist’s paddling technique. A traditional Canadian-style solo canoe, paddled heeled over, is 14 to 15 feet, with a symmetrical shallow-arch hull. Widths range between 25 and 34 inches, with a slight tumblehome to the sides.

The traditional American Rushton-style solo canoe, on the other hand, is paddled flat with a double blade. It is typically narrower (24 to 30 inches) and shorter (10 to 14 feet), with a shallow arch/shallow-vee hull. The paddler sits on the hull bottom, supported by a backrest.

The contemporary Gault-style solo canoe, a new design now fashionable in the United States, is paddled well heeled over. It is also narrow (24 to 30 inches), with shallow, flared sides and an asymmetrical hull 13 to 16 feet long, with a rounded-vee bottom and soft bilges. 

After digesting this chapter, you may not be ready for the world of custom design, but you should be able to set your own personal performance priorities. As one builder exclaimed after mastering the mysteries of canoe design: “I’m not trained, but now I certainly can tell an ugly canoe when I see one, and I have a pretty good idea about how poorly it must handle.” In the next chapter, you will find plans for a range of canoes that are as sweet in the water as they are on the shelf.

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Reuben Smith's Tumblehome Boatshop

About Reuben Smith

Reuben Smith is boatbuilder and owner of Tumblehome Boatshop, which he has reestablished in the Southern Adirondacks to focus on the high‐end restoration and new construction of historic and classic wooden boats.

Reuben Smith grew up in a boatbuilding family. Through his high school and college years, he worked in his uncle’s shop, the Everett Boatworks, in Canton, New York, and his father’s shop, Adirondack Goodboat, In Long Lake, New York. Working with his father and uncle, Reuben was surrounded with a crew of highly skilled and committed craftsman who showed him what a fine boatbuilding job really could be. Those shops worked on canoes, skiffs, and guideboats, as well as runabouts and launches.  The work was primarily restoration of historic boats, but included new, and modern wooden boatbuilding, as well.

In 1997, Reuben started Tumblehome Boatshop in a corner of the Everett Boatworks, but then had the opportunity to leave Northern New York, and head to the Boston area, where he was Boatshop Director for the Hull Lifesaving Museum in Hull, Massachusetts. Reuben Smith worked with a crew of adjudicated kids in Boston building and maintaining a fleet of rowing gigs, from 24 to 38’ feet long. At the museum, Reuben learned how to teach boatbuilding skills.

He left the Lifesaving Museum in 2000, and started up Tumblehome Boatworks, the Rolling Boatshop. He built a shop in the back of a box truck, and toured up and down the Massachusetts coast subcontracting in boat yards.

There, Reuben met Cynde, and they were married in 2002 and settled down in Plympton, Massachusetts. With Cynde’s help he grew his reputation and his business, and the two became a strong business team as well as a great couple. Reuben taught an annual special topics course in boatbuilding for several years at the Massachusetts Institute of Technology (MIT). In 2004 Tumblehome Boatworks moved to the Jones River Landing in Kingston, Massachusetts, into the famous old Shiverick Boatshop. There, Reuben founded Mass Bay Maritime Artisans, and conducted a workshop and a boatbuilding lecture series.

But the North Country was calling him back, and when, in 2008, Hall’s Boat Corporation on Lake George was looking for a manager for their newly expanded Boatshop, it was an opportunity not to be missed. Reuben joined Hall’s in 2008 and with Hall’s had a terrific run of boatwork, with several fine restorations completed there, as well as a whole lot of boat repair and maintenance on the wooden boats on Lake George. The Boatshop expanded with three new boatbuilders, as well, and became a restoration powerhouse. Cynde also joined the team, helping with marketing and PR, and the word got out about what was going on at Hall’s Boat Corp.

In 2012, it was time to reestablish Tumblehome Boatshop in a new, dream scenario. In a 6,000 square foot building, Reuben built a new boatshop grounded in a heritage of solid craftsmanship, and a commitment to service and excellence.

The move to start up Tumblehome was propitious. Reuben was fortunate to have a few loyal customers bring their boats to the shop, and right away, Tumblehome was busy, with a backlog of enviable projects.

Probably most importantly, however, the shop quickly gained a reputation among people who work in the trade. As the hardware piled up from boat shows, and the reputation of the shop as a healthy and collegial place to be grew, Reuben began to put together a stellar crew of gifted craftspeople. Far from being a one-man show any longer, Tumblehome Boatshop is now a team of craftspeople driven to excel.

tumblehome sailboat

tumblehome sailboat

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What Is a Tumblehome?

A tumblehome is a design feature in ships wherein the sides show a convex curvature on the bottom portion and continue up in a slightly concave line on the upper portion of the ship. If the ship were to be cut in a cross section, its shape would resemble that of a pear, with its lower half larger than the upper half. In design terms, the tumblehome is the direct opposite of the flare, which features a more concave curvature that makes for a V-shaped water vessel.

The origin of the tumblehome is somewhat uncertain, but its usage can probably be traced as far back in the 1700s, when many European countries were at war in an attempt to conquer as many foreign lands as possible, along with the notoriety of many pirates. Many warships contained much artillery often located at the upper deck for easy accessibility, thus making the ship top-heavy. Creating a broader and heavier bottom slightly shifts the center of gravity in a lower position, thus making the ship more stable and well-balanced. In the event a ship is hit by cannonballs, the tumblehome design helps deflect the said cannonballs and prevents the vessel from tipping over by the force of the collision.

Another advantage of a tumblehome is that enemy warships are kept as far away as possible, due to the broad distance covered by the ship’s convex sides. Even if the ships stood side by side, there would still be a huge distance between two decks, making it difficult for enemy soldiers and pirates to climb aboard. The convex shape of the ship would also pose some difficulties for invaders to climb up from the waters.

In suitable proportions, the tumblehome proved to be an advantage for stability, but unfortunately, in the 1800s, designs were greatly exaggerated, making the curves too round and too big. This resulted in less stability for the ship, very much like a ball bobbing in and out of the water. Combating strategies and effectiveness were affected as crews were experiencing seasickness, the ship was going off course, and the cannons could not be aimed accurately at enemy ships

In more modern times, the tumblehome feature is applied to small boats and canoes, although it is often combined with other features, such as a V-shaped bottom, to make the canoes slice through the water more easily while still maintaining buoyancy . The design is also applied to US Navy destroyers, as the shape helps decrease radar return and makes the warcraft stealthier. The tumblehome design has even been incorporated in automobiles, as a rounded shape decreases air drag and helps increase speed.

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  • Zumwalt class destroyers, which are the U.S. Navy's most advanced surface combatants, feature pronounced tumblehomes.
  • By: Juulijs Many ancient warships, such as Greek triremes, had hulls that featured tumblehomes.

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Motor Yacht

Tumblehome is a custom motor yacht launched in 1997 by Lyman Morse Boat Co. in the USA, United States and most recently refitted in 2013.

Tumblehome measures 27.43 metres in length, with a max draft of 2 feet and a beam of 6.7 feet. She has a deck material of teak.

Her interior design is by Lisa Pirofsky Designs Inc..

Tumblehome also features naval architecture by C. Raymond Hunt Associates.

Performance and Capabilities

Tumblehome has a fuel capacity of 3,000 litres, and a water capacity of 1,400 litres.

She also has a range of 500 nautical miles.

Accommodation

Tumblehome accommodates up to 6 guests in 3 cabins.

Other Specifications

Tumblehome flies the flag of Marshall Islands.

  • Yacht Builder Lyman Morse Boat Co. No profile available
  • Naval Architect C. Raymond Hunt Associates No profile available
  • Exterior Designer C. Raymond Hunt Associates No profile available
  • Interior Designer Lisa Pirofsky Designs Inc. No profile available

Yacht Specs

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Discussion in ' Boat Design ' started by SuperPiper , Jan 10, 2003 .

SuperPiper

SuperPiper Men With Little Boats . .

I have read the Volvo Ocean 60 rule. It is very specific that the widest part of the hull must be at the hull-deck joint. Therefore, tumblehome is not permitted. I assumed that this was for safety concerns and would aid in self-fighting a capsized boat, etc. However, the boats in the current Around-Alone race feature very significant tumblehome. Their hulls resemble kayaks more than canoes. So the question is: What is tumblehome? What does it do? Why would it not be allowed on a fully-crewed ocean racer but allowed in a solo race? Does it have a hydrodynamic advantage? Does it merely reduce windage? What do you know?  

gonzo

gonzo Senior Member

Tumblehome alone is not enough to define the characteristics of a design. It has to be taken within context. Usually, the handicapp or class rules affect the shape of the hull more than common sense. Boat designers, in their effort to beat the rules, often come up with bizarre solutions. Stability is affected by many factors and how they are related. For example a narrow deep boat can have adequate stability, but so can a wide shallow one. However, narrow and shallow or wide and deep are bad combinations. Do you have a problem or question with a particular design?  
If the Volvo Ocean 60 rule had allowed tumblehome, do you think that Bruce Farr would have incorporated tumblehome into his designs? Not allowing tumblehome must have been for 1 of 2 reasons: 1 - safety; or, 2 - to ensure that no yacht could achieve an unfair advantage. What is the advantage of tumblehome? The radical designs of the open 60's, 50's and 40's in the current Around-Alone race seem to have embraced the concept of curling the hull back inboard at the topsides. For why? What is the technical explanation for such a feature?  
One of the advantages of tumblehome is that the center of gravity is lower than in a design where the maximum beam is at the deck. This, of course, is assuming the depths are similar. Tumblehome also has a more even stability curve. The early radical "dish boats" of the IOR formula had the problem of floating upside down. The flotation reserve of a deck and hull above the maximum beam helps a boat right itself after a complete capsize. On the other hand, a lot of flare with the maximum beam at the deck can allow the boat to carry more sail because of the higher initial stability. The argument of safety versus sail carrying ability is what makes some rules forbid such extreme beams at the deck. I hope this help you.  

Guest

Guest Guest

There are several advantages to tumblehome: as already mentioned, it reduces inverse stability; it allows outboard shrouds to be moved in relative to overall beam and thereby reduces sheeting angles; since a curved panel is stronger than a flat one for a given scantling, one can achieve greater strength with less displacement. The disadvantages are reduction in side deck area and a slight increase in tooling costs. Since offshore racing boats do not utilize outboard shrouds, one can only assume that the reduction in side deck area was a safety factor considered more important by the developers of a rule intended for crewed vessels. Brad  
The common theme of the last 2 responses is that a boat with tumblehome is more likely to remain upright and/or return to upright. I think that I will need to draw a cartoon to prove this to myself. Thanks for the help, guys.  
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Try this experiment to see how tumblehome works as opposed to a beamy boat with extreme flare. Take a ball and tape a weigh on one spot. Now float the ball and try to make the ballast stay on top. Next take a piece of board, foam or anything flat and put the same wieght on one side. It will float with either side up. These reperesent both extremes.  

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Boat Design Net

IMAGES

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  2. TUMBLEHOME

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  5. TUMBLEHOME yacht for sale

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  1. Tumblehome Trailer 2

  2. Special day.. #remodel #refit #sailboat #boatrenovation #sailingboat #renovation #travel #boating

  3. Sold up. Bought a narrowboat. #dreamhome #boatlife #tinyhouse #downsize #shorts

  4. 2023 Tumblehome Lodge Smallmouth & Largemouth

  5. Lost Paddle Forth Drop: Tumblehome (Class V)

  6. Massive progress #refit #sailboat #sailingboat #renovation #remodel #sailing #diy #boat #yacht

COMMENTS

  1. Front Page

    "Tumblehome" is an old boatbuilding term, referring to boat shape. The opposite of flare, tumblehome is where the upper part of the sides of a boat curve back inward. You can see tumblehome most distinctly at the stern of a boat. 518-623-5050 Tumblehome Boatshop • 684 State Route 28 • Warrensburg NY 12885. Facebook; Instagram;

  2. Tumblehome

    Tumblehome is a term describing a hull which grows narrower above the waterline than its beam. The opposite of tumblehome is flare. ... such as the Type 022 missile boat. In narrowboat design. Pronounced tumblehome only on the superstructure of this narrowboat. The inward slope of a narrowboat's superstructure (from gunwales to roof) is ...

  3. Tumblehome, stability, and performance

    3070 posts · Joined 2007. #6 · Sep 18, 2008 (Edited) Actually tumblehome was a means to strengthen the hull. That curvature made the hull stronger than what a slab side would. So some tumblehome would be a good thing. As long as you don't go overboard with it and end up looking like a beer can floating on its side.

  4. Sound Inter Club Sailboat

    Tumblehome Boatshop specializes in the restoration and new replica construction of the 1926 Sound Inter Club. This racing class sailboat was designed by the prolific and ground-breaking boat designer, Charles D. Mower. Only 28 of these impressive sailing boats were built - most all of them in 1926 by the craftsmen at the Nevins Boatyard on ...

  5. Reuben Smith's Tumblehome Boatshop

    Reuben Smith's Tumblehome Boatshop, Warrensburg, New York. 5,268 likes · 778 talking about this · 102 were here. Restoring and constructing historic and classic wooden boats.

  6. Reuben Smith's Tumblehome Boatshop

    High‐end restoration and new construction of classic wooden boats is the dual goal of Reuben Smith's Tumblehome Boatshop. In 2015 Tumblehome received an AARCH Preservation Award for their conversion of a garage building into an industrial-chic center of concrete, steel, and wood. Smell the fresh wood shavings in an active boat shop, watching as vessels...

  7. purpose of tumblehome in runabouts

    On a sailboat without tumblehome, max righting moment usually comes when the hull is rail down. With tumblehome, as in the Ranger 28 with max beam being about halfway up the topsides, righting moment gets a boost earlier at lower angles of heel. Better or worse overall, I don't know.

  8. Lovely on the Lake

    Kelly wanted the boats to return to their original purpose, match racing, and to ensure that the design wouldn't die. (Since then, Tumblehome has also restored a third boat, Aileen, and also builds the boats new, using lines taken from Caprice.) More than anything, Kelly says, restoring a boat with Tumblehome is a relationship with the boat ...

  9. What is the function of tumblehome in a ship?

    Tumblehome is an important design feature on boats and ships that serves a diverse range of functions, from improving efficiency and stability to enhancing the vessel's appearance. Whether you are a boating enthusiast, a shipbuilder or simply curious about the inner workings of these complex machines, understanding the role of tumblehome is ...

  10. Boathouse

    Boathouse. Our public space next to the boatshop, the Boathouse at Tumblehome, is open to the public with regular business hours, and includes a showroom with any number of boats on exhibit. When it opened in 2015, the Boathouse featured a museum-style exhibit of "El Lagarto," the famed Gold Cup raceboat, which had left its prominent ...

  11. Here's how the destroyer Zumwalt's stealthy design handles stormy seas

    Now its captain is speaking out about how it handles high seas. (Robert F. Bukaty/AP) WASHINGTON — After years of stability questions about the hull design for the U.S. Navy's new three-ship ...

  12. Mirage 21

    With generous flair, classic tumblehome and plenty of unimpeded deck space, the Mirage 21 carries a "big boat" attitude that stands out from the crowd. Good looks aside, it is a rugged, practical do-anything launch that can be customized in a variety of ways to suit an owner's needs and preferences. This boat was first developed to explore ...

  13. Home

    Tumblehome Yachts are built for kids up to 48″ tall. They are land based wagons, sleighs and rockers and are not intended to float on the water. Our package includes the handcrafted hull with fully varnished deck, trim and interior, customized with your choice of topside colors and name/hail port graphics on the transom, laminated tiller ...

  14. Why are ships built with tumblehome? What does it do?

    Some sailboats designed to a racing rule have tumblehome to take advantage of the rule. With beam measured at the deckline for the rule, but not on the hull, tumblehome gives more stability for a given rating. Various reasons for tumblehome. Among other reasons, it reduced the topside weight of a ship.

  15. Anatomy of a Canoe: Essentials of Good Design ...

    Top: A plumb bow forces the canoe's sides to flare, while traditional recurved bows result in tumblehome sides. High recurve is traditionally attractive but can make the canoe susceptible to wind. Above: Fine entry lines part the waves more smoothly than a blunt-nosed bow that plows the water. The result is greater speed with less paddling effort.

  16. About Reuben Smith

    Reuben Smith worked with a crew of adjudicated kids in Boston building and maintaining a fleet of rowing gigs, from 24 to 38' feet long. At the museum, Reuben learned how to teach boatbuilding skills. He left the Lifesaving Museum in 2000, and started up Tumblehome Boatworks, the Rolling Boatshop. He built a shop in the back of a box truck ...

  17. What Is a Tumblehome? (with pictures)

    In more modern times, the tumblehome feature is applied to small boats and canoes, although it is often combined with other features, such as a V-shaped bottom, to make the canoes slice through the water more easily while still maintaining buoyancy.The design is also applied to US Navy destroyers, as the shape helps decrease radar return and makes the warcraft stealthier.

  18. 27.4m Tumblehome Superyacht

    Tumblehome is a custom motor yacht launched in 1997 by Lyman Morse Boat Co. in the USA, United States and most recently refitted in 2013. Design. Tumblehome measures 27.43 metres in length, with a max draft of 2 feet and a beam of 6.7 feet. She has a deck material of teak. Her exterior design is by C. Raymond Hunt Associates.

  19. tumblehome

    The tumblehome will affect rolling if you think the boat will roll lots or wish to use tumblehome to reduce rolling. But the effect will be minimal if the tumblehome you're look at, for styling, is around 5~10degrees. Look at some of the old classic Riva's... A successful design - is greater than the sum of its individual parts....

  20. Tumblehome

    One of the advantages of tumblehome is that the center of gravity is lower than in a design where the maximum beam is at the deck. This, of course, is assuming the depths are similar. Tumblehome also has a more even stability curve. The early radical "dish boats" of the IOR formula had the problem of floating upside down.