Back Bay Sit On Top Kayak

A Modular System Approach to SOT Kayak Sailing, Paddling and Mirage Drive Propulsion

BB Scorpion bow obl 8 w

Sit-On-Top (SOT) kayaks are easy boats on which to learn to paddle. They have none of the “get in the coffin and you are about to drown” psychological identity that one finds in the Sit-Inside boats and they’re amazingly adaptable to a wide range of paddling activities. It also doesn’t hurt that they are pretty straightforward boats to rotomold, which makes them very cheap to produce in large numbers.

I didn’t envision just one boat for this niche in the home-built kayak market. Instead, it came to me that there would need to be at least three models that could address the wide-ranging styles of boating interests in this area of the kayak world. The result was a couple of very clean, SOT models at 14’ and 16’ called the Corona and the Back Bay, respectively. The third model was going to be called the Wahoo, as it was specifically designed for the folks who spend a lot of time fishing with their SOT’s. I’ll get to the Wahoo in the next article.

As a canoe and kayak sailor and a guy who had just been out for a test drive on the Hobie Adventure Island, which is based on their 16’ SOT Adventure model, I wanted to offer my own take on what makes for a truly fun and stylish, sailing SOT kayak. The result was that a fully integrated system of component parts was designed for the basic Back Bay. This modular approach allows the Back Bay to go sailing by simply adding a system of light-weight, easily built elements that quickly convert the SOT to a single aka sailing boat called the Scorpion, OR, to a double aka sailing boat with slightly larger ama volume, called the Doubloon. Of the two configurations, the Doubloon is most like the well-known and highly respected, Hobie Adventure Island.

The Corona and the Back Bay are virtually identical models, save for their respective lengths. For the purposes of this article, I’ll focus on the Back Bay version and all the potential add-on systems I’ve incorporated in the design.

THE BACK BAY SOT KAYAK

BB16 above w

Specifications:
Length overall – 16′
Beam overall main hull – 28″
Depth of hull max – 12”
Weight – 48 lbs. or less
Displacement – 335 lbs.

This boat is built in the S&G style of construction in 4mm marine ply with 6 oz. plain weave fiberglass set in epoxy on the inside and outside of the hull for full laminate sandwich strength. The build process uses external cradles as building supports, ensuring that the hull goes together with minimum hassle when handling the rather slender and longish hull panels. The boat is bulkheaded internally at three key points. These bulkheads create not only integrated strength in the design, but they also cleanly separate the hull cavity into four unique volumes for gear storage and watertight flotation.

The Back Bay can be configured with a large, open tankwell set aft of the cockpit, or built with a watertight, aft hatch cover for internal storage in a conventional kayak style.

Scorpion bow low w

Specifications:
Beam overall – 10′
Weight (est.) – 90 lbs.
Sail Area – 56 sq. ft.
Displacement – 350 lbs.
Draft (board down) – 28″

The Scorpion variant is a Sit-On-Top design for fun sailing, paddling, or Mirage peddling… or all three, as the builder desires. There will be a design for a leeboard mount included in the plans for those who are going to build the boat for sailing. Having the aka gull wing form set well forward permits a full paddle swing arc.  The aka beam connectives to the amas is split into a pair of mounting elements. I did this to make for a stronger, single beam mounting struture. With a single beam design, there is a tendency for the am to want to rotate around the beam, making for a very stressed component that could lead to early failure. By splitting the beam and spreading the mounting points, I have given the structure more resistance to this rotational force, making for a more rigid boat in use. This setup will allow the owner to power sail in light air with both the paddle and the sail providing thrust. With the leeboard swung down for sailing, the owner can do some “power sailing” and utilize the Mirage drive, as well as the sail, in light conditions. The Mirage is capable of boosting boat speed enough that it creates apparent wind over the sail, adding power where there really isn’t enough for sailing alone.

The amas are positioned to optimize capsize resistance when sailing off the wind. The amas do not touch the surface of the water at rest in stable trim and provide only minimal wetted surface drag when underway by paddle or peddle. As soon as the sail is loaded by the breeze, though, the ama on the lee side begins to immerse, firming-up the boat and resisting the heeling moments being generated.

The aft deck can be configured as a watertight hatch with full access to the aft sections of the hull, OR a large, diving tank well with self-draining ports. The cockpit is fitted with self-drain ports under the seat as well as forward, in addition to the daggerboard slot. There is a watertight deck plate just forward of the seat, between the knees of the sailor/paddler to provide secure storage for critical items that may be needed on a routine basis. The foredeck has a watertight hatch cover for bow storage needs.

The rig is a fully battened Dacron sail with two reef points and a multi-section, self-supporting mast which steps into a sealed mast socket in the hull. The mast and boom sections can be aluminum or carbon, as budget permits. The sail choice is open for the customer as long as it can be balanced with the fixed positions for the mast and dagger board. The Cunningham is run to the deck of the gull wing aka to keep the rig on the boat in the event of a capsize.

With 56-sq. ft. of sail on a 90-pound boat, this will be a decently speedy boat without being in over its head all the time in a stiff breeze. I suggest two reef points in the sail to allow for sailing in a wide variety of conditions.

This will be a wet boat at speed, yet there are no worries at all for flooding and sinking, save for a truly nasty trip over a reef that shreds the entire underside of the craft. The bow, cockpit and aft hull volumes are all independent, sealed compartments, as are the ama volumes.

Reentry from a swimming session will be easy with a simple, sling, or rope ladder much like those used by rock climbers, called etriers.

BB Scorpion aft obl 8 wSliding foot pedals in the cockpit control the rudder. The rudder flips-up when it encounters an underwater obstacle, or when beaching, returning, due to bungee tension to the deployed position once past the obstruction.

The boat is constructed in a multichine, marine plywood style with epoxy glass laminates inside and out in a stitch and glue style. Stainless T-Nuts are embedded in the hull deck surface from below to provide a secure set of mounting points for the aka wing. The amas are held in place on the aka tips by large bungees and a notched lock system. This system provides for quick setups on the beach.

You just fit the aka to the foredeck, insert four, 1/4″ threaded stainless screws with comfortable, knobbed grips and screw down the aka wing. The amas slip onto the ends of the aka and you lift the pair of 3/8″ bungees up and over two raised hooks on the aka ends to secure the ama in place. Simple, easily maintained and near foolproof in operation.

DOUBLOON SAILING SOT

Doubloon bow obl 8 w

The Doubloon is the second variation on the central SOT theme of this group of boats. In this design, I am looking to provide a more expansive utility application for the base, Back Bay SOT version. The Doubloon is essentially a solo craft and it carries the same, 56 sq. ft. sail, but the overall potential of the boat is expanded through the use of dual akas and full trampolines on both sides of the Back Bay hull. The rendering of the Doubloon shows a daggerboard inserted down through the Mirage Drive trunk, but in use, I would prefer to have the board mounted outside the Back Bay hull as a leeboard. Plans will be supplied with the leeboard solution.

The akas on the Doubloon are spaced to allow for a full paddle stroke with the boat setup as a trimaran. There are two sections of tubing that span the opening fore and aft between the akas from which the tramp is mounted. The trampolines are designed to roll-up on the outer tube section, much like a window shade and they are deployed by an endless loop of light halyard line. With the tramps fully deployed, the inner tube section lifts up and over a holding pin in the aka and the sailor applies as much tension to the tramp as he feels he needs by hauling-in the endless loop line and cleating it off. If a paddling session is desired, he simply pops the jam cleat and pulls the line to roll-up the tramp on the outer tube section. This procedure applies for both port and starboard tramps.

Like the Scorpion, the Doubloon can be built to utilize a Mirage drive in the center well and the need to roll-up the tramps for paddling is essentially negated, (though it is nice to have the option once in awhile as Mirage drives can be difficult to maneuver in tight places)

The aka beams are held to the deck of the Back Bay hull with the same, threaded knob strategy for quick setup and takedown times. Similarly, the amas are held to the aka ends with hefty bungee cords for the simplicity of use. There’s another, rather invisible, benefit to using the bungee cords for ama mounting. Because they are being held in place through a fairly dynamic hold-down system, the amas can move about, ever so slightly, while underway. This allows the amas to have some structural “give” and the result is that the banging and thrashing that is typically experienced by the ama, is somewhat dissipated through the flex of the joining system.

Doubloon aft obl wThe design similarities to the Hobie Adventure Island are obvious. This boat, however, should be just a bit faster in the water, mostly because it will be much lighter than the rotomolded Hobie. For that same reason, it will also be easier to put it up on a roof rack for transport to the water and a lot easier on the back when you have to take it off the car to store it at home. The Doubloon configuration allows the sailor/paddler/peddler to bring along extra gear, which can be lashed to the tramps in waterproof bags. They can also take along kids, or perhaps someone special, who could lounge out on the tramp surface while lazily sailing along for a sunset cruise on a warm summer evening.

All in all, I think the Back Bay SOT should be a really fun boat to own for warm water/warm weather boating adventures. It has the capacity to carry enough gear for several days out on the water. When rigged with a sailing system of your choice, it can also cover some pretty good distances if the winds are favorable. Plans for this boat and all its variations will be available from this site and Duckworks Magazine.

Chris Ostlind

Lunada Design
Chris@Wedgesail.com

NAGARE 21′ AND 17′ MIRAGE DRIVE SPEEDSTERS

Making use of Mirage Drive propulsion with more efficient hulls designs

 

Nagare 21 Bow Obl w

Nagare  (nah-ga-ray) is a Japanese word meaning Flow.

The two boats in this group are 17 and 21 feet in length and are known simply as the Nagare 17 and the Nagare 21. Both designs make use of the popular Hobie Mirage drive for principal propulsion with the 21 footer Nagare 17 bow obl wbeing a double Mirage setup and the 17relying on a single Mirage.

Both of them are configured as trimarans with fairly small and unobtrusive amas designed to give the boats remarkable stability in a wide range of conditions while allowing the vaka, (main) hull to be decidely slender for more effective drive through the water.

The Nagare sisters also have incredibly narrow waterline beam numbers that, when coupled with their fairly long hulls provide for very easily driven hull forms for high efficiency per unit of energy applied.

I expect both boats to operate at the very high end of commercially available paddled boats of the same length, beam and weight. So, yes, they can go pretty quickly, but that’s not the real purpose.

The real benefit of the design genre is through the ease with which they are propelled at any given speed, compared to other boats of their size. This efficiency translates directly to those using the boats as less tiring for miles covered, or greater speed with the same effort as other, wider designs.

Because the propulsion is derived from the largest muscles in your body, the leg muscles, rather than the arms and shoulders, there will be less fatigue for each mile traveled. Because leg muscles are so much bigger than arms, they will be able to do more work in a given period of time, making for longer possible trips, as well as the mentioned lower fatigue issue. With a less fatiguing effort, more people will be able to enjoy the experience of being out on the water for daylong adventures.

NAGARE 21 DOUBLE
SPEED AND STABILITY FOR DOUBLE RECREATIONAL BOATERS

Nagare 21 Aft Obl w

The Nagare 21 uses a set of amas, mounted on a pair of simple, anodized aluminum tubes with quick release snap buttons holding the sections together for easy disassembly for car-topping. If a trailer is used to transport the boat, the beam of the Nagare 21 falls well below trailer maximums, so nothing special needs to be done to take the boat to and from the water. Two Nagare 21’s can be trailered, or car-topped, by removing one of the amas and placing the main hulls close to one another on the racks, or trailer. The removed amas easily fit inside the hulls and they are ready to go. The whole affair on the rooftop is very much like a pair of sea kayak doubles. Because of the length, I would not mount a boat this big on any compact cars. You would be very likely to rip the rack right off the roof in strong side winds.

Steering is by means of a simple, flip-up style kayak rudder with control lines run through the hull to a convenient steering lever in the cockpit. I suggest the SeaLine SmartTrak rudder system (do a search for supplier), the P-41 Multi-purpose rudder from Onno Paddles http://www.onnopaddles.com/onnocomponents.htmland the Feathercraft rudder system for hardshell boats. http://www.feathercraft.com/accessories/rudders-hardshell.php  These are really great rudder units and will give excellent steering control with minimum drag.

NAGARE 21 SOT OPTION

This boat can be built with a full cockpit tub so that it functions as a Sit-On-Top kayak with full drainage through the Mirage drive openings. Auxiliary drain ports are located in the tub for rapid removal of any water that comes in over the side of the hull. I suggest the SOT option for warm water users, with the more traditional kayak style, Sit-Inside hull form for those who will be using the boat in colder water, or more frequent inclement weather.

The SOT version has internal bulkheads for support of the SOT tub, along with the capability of adding a small circular deck plate for an additional watertight compartment in the cockpit that is perfect for small items, such as cameras, wallets, car keys, etc.

The SOT variation is an optional element to the base plans. If you wish to built it as an SOT, drop me an email at my regular email address and I’ll get back to you.

ROUGH WATER USE

This is not really a boat that is meant to go out in rougher conditions, such as those where a full-blown sea kayak might be right at home. It’s meant for quieter waters, such as lakes, bays, harbors and bigger rivers. It can take a session in 1 or 2 foot breaking surf, but I would not expose the boat to bigger waves, especially in a shore break scenario. You may find yourself out from the shore a bit when the wind comes up, producing steep, choppy waves. The basic Nagare 21 will handle this easily because only the cockpit will be exposed to swamping. The amas will keep the boat stable while you pedal to shore, or a quieter place on the water, where you can bail-out the boat and continue.

It is a perfect boat for sightseeing, bird watching, fishing, photography, and just simple, energy efficient cruising with near bomb-proof stability (you can stand up in the boat while out on the water without your partner coming completely unglued, for instance).

The Nagare 21 is a fast, comfortable and unique boat for a couple who like to get out on the water, but do not want to hassle with the business of capsize that is present in other types of boats, such as kayaks and even canoes.

NAGARE 17 SINGLE
A NEW STYLE OF SOLO BOAT FOR TROLLING FISHERMEN

The solo version of the Nagare series has some very different twists, compared to its bigger sister. It has the same, highly efficient and easily driven, slender hull technology, the same set of trimaran style amas well aft for big time stability, the same generous cockpit opening and the same convenient utility for car-topping or lightweight trailering.

The design elements that set this particular boat apart from its sister craft is that the Nagare 17 has a very special capability when it comes to fishing.

AFT FACING TROLLING

Anybody who builds the Nagare 17 and intends to use it for fishing will probably be knocked-out by the potential for facing aft while trolling. Imagine using your legs to quietly drive the boat forward while you casually set trolling rigs, eat a sandwich and keep an eye on the fish finder… all while keeping an eye on the rigs you have set, with them easily at hand?

Nagare 17 bow obl trolling mode w

This is the signature utility development with the Nagare 17, designed specifically, for fishermen. It works like this…

The fisherman loads his boat, drops into the forward facing seat, hits the iPod for his favorite tunes and jams out across the lake at a remarkable speed for a human powered boat. He zips across the lake in virtual silence because he’s driving a very skinny and efficient hull with no engine sounds. Once he arrives, he’s going to make a few sneaky trolling passes with his Mirage drive pushing him along over that monster crew of Pike that are hanging around on their favorite piece of structure. Wham! Fish On! and the day starts with smile on his face.

If you’ve ever fished from a typical Sit-On-Top, you know that you have to face forward while trying to look over your shoulder while trolling. Hook-up and then you have to swivel around, grab the rod and go after the fish. All the time you are doing this, you have to balance the boat carefully, because the whole tamale could go over and end your day right then and there.

Well, that’s how you used to do it, anyway.

With the Nagare 17, you can take it to a whole new level of fishing pleasure. The Nagare 17 is equipped with twin Mirage drive trunks. When driving the boat forward and facing forward, the Mirage drive is dropped into the forward trunk and a tractor-style seat is dropped into the aft trunk with the seat bottom resting on the top of the trunk.

To convert the boat to aft facing trolling and fishing, you simply stand up in the boat and swap the Mirage drive for the aft mounted seat plug and the seat then goes to the front trunk… facing aft. With the Mirage drive still set to drive the boat forward, you simply sit down and start pedaling, slowly, up to your desired trolling speed.

Now, you can watch your fish finder, GPS and your trolling rigs while you continue to tool along at your favorite speed for nabbing the fish. Get one on and simply work that rod while continuing to face aft. No twisting around in your seat, no ”just about dumped it” scenarios, just simple, fun fishing in a very stable boat. What could be cooler than that?

With the fore/aft balance point of the boat set right between the two drive trunks, there is but a very minimal change to boat pitch when you change the direction you face.

The Nagare 17 is further designed to accept an insulated and watertight tank between the two aka tubes where they run through the aft deck. You can use this for all kinds of stuff like: your catch, fresh bait storage, cold beverages if you catch and release… whatever suits your needs. There is plenty of room between the two drive trunks for a pretty good sized tackle box and lots of room up forward of the trunks for any of that “other stuff” that fishermen seem to sneak aboard their boats.

Nagare 17 aft low obl w

A moveable electronics unit can be fastened at the forward end of the cockpit, or unhooked and moved around aft if you’d rather have it facing that way.

Maybe you want to cast lures or flies instead of troll. The boat is so stable with the two, wide set amas, that you can stand up and cast all day without ever feeling like you are getting the least bit tippy. All in all, the Nagare 17 is quite a boat for fishing, as well as just plain fun, recreational pursuits.

The Nagare sisters represent a unique design family for human powered vessels. They are quick, stable and with their unique styling, represent a distinct departure from the looks of traditional boats one typically sees on any given shore or launch ramp. Both boats are designed to be built in marine ply Stitch and Glue methods for the hull sections, with cedar stripped decks to take advantage of the really beautiful, smooth curves capable from that style of building. You can paint the lower sections of the hull and leave the cedar decks natural with a deep varnished finshed, for a real knock-out boat that will really gather a crowd.If you really want to have a plywood deck build instead of the cedar strip build, write and twist my arm gently. I can design that change for those who really like to build that way

Plans are not yet complete, so if you would like to build one of these two boats, please send me an email and I’ll put your name on the mailing list for information, or watch the plans section of Duckworks for the notice.

CHRIS OSTLIND
LUNADA DESIGN
CHRIS@WEDGESAIL.COM