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The 60' Aluminum Motor-Sailing Yacht

Swallowtail 60

60' Swallow's Nest - Motor Sailing Yacht

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Larger Exterior Profile | Deck Plan | Interior Layout
Aft Perspective | Forward Perspective

 See 70' Swallows Nest Below

Copyright 2015 Michael Kasten

Concept

The Swallowtail 60 design shown here is a direct descendant of the Swallow's Nest 60, both designs having an identical hull form, a hull shape also shared in common with the Greatheart 60.  All three have a hull type inherited from other designs in our Gulliver and Greatheart design series, all derived from the ultra-seaworthy Pacific Northwest fishing vessel types, refined in this case for service as yachts.

The inspiration for these vessels has been to create truly pelagic water craft that can spend long periods of time between ports of call, optimized as a habitat for ocean travel and living aboard.  In the case of the Swallowtail 60, the layout is optimized for a couple, with occasional guests accommodated on a convertible couch in the saloon or during nice weather on the aft deck settees.  As such, it is a private yacht for two, with the ability to accommodate guests when needed. 
 

Particulars

Hull construction on the Swallowtail 60 is all aluminum, chosen for lightness, ruggedness, low maintenance, and efficiency of propulsion. The Swallowtail 60 particulars are:

If the design were to be converted for construction in steel, the beam and hull body depth would necessarily be increased in order to carry the added weight of structure. In steel, a larger engine and more fuel will be required; more sail area would be indicated; beam will be on the order of 17 feet; and average displacement will approach 80k lb depending on equipment choices.  On that basis, we can readily observe the advantages offered by an all aluminum structure.
 

Power

The Swallowtail 60 was created to take maximum advantage of the John Deere 6068 TFM having an M-2 rating of 175 hp at 2400 rpm.  This may seem like a modest amount of power for a 60' vessel, however 175 hp is able to drive the vessel at 11.5 knots, well beyond its theoretical maximum hull speed. 

If fixed pitch were preferred a standard Twin Disc gear and FPP propeller would be specified. 

However for maximum efficiency we have instead specified a controllable pitch system.   The gear specified is a Nogva HC-168-C which operates a pitch control servo internally, providing both gear reduction and pitch control. The wheel specified is a three blade Controllable Pitch Propeller driven through a concentric shaft within a self contained shaft log, all by Nogva of Norway.   With a CP propeller, boat speed can be dead slow or just a bit more when trolling for salmon, or can be faster for tuna... The propeller always turns the same direction, so maneuvers are made simpler because there is no requirement to stop the propeller. One can leave the engine at idle or just above, and feather the blades around between forward and reverse for maneuvering.  Or one can also hold station using a shallow pitch against a slight breeze or current without having to engage / disengage the gear.

As a motor sailing vessel, the CP propeller will not only provide maximum efficiency under power, but will also allow one to choose a suitable engine power, rpm and pitch while motor sailing.  The propeller pitch can be increased as needed in order to provide just the right boost to boat speed, while keeping the engine at the sweet spot with regard to noise, vibration, and fuel economy. 
 

The Rig

The sailing rig is also intended to provide primary power, but also functions as emergency get-home power, as a very effective means of roll dampening, and allows one to take advantage of the synergy of motor-sailing during passages.  To understand why the rig itself is effective at Roll Attenuation, it is instructive to know more about a vessel's Roll Moment of Inertia.

Motor sailing provides a synergy that has to be experienced to be appreciated...  Studies have shown that 3 knots' worth of engine power can produce more than 12 knots of boat speed, given the right wind conditions.  The primary reason for this is that under power, the vessel is in part creating its own wind, of which the sails can take full advantage.  With this combination, the range of the vessel is vastly increased, and when the wind favors there is the very welcome potential to spend long periods without the engine running at all.

The Swallowtail 60 has been designed with a junk rig, as shown above.  The Chinese junk rig is described in greater detail on our Junk Rig web page.  The spars are all aluminum pipe for lightness, strength, and ease of maintenance.  The masts are free-standing, eliminating rig chafe and providing the sails much more freedom of motion. 

Bilge keels have been specified in order to provide superior roll attenuation and the best sailing performance without having to resort to deep draft.  Bilge keels also allow the vessel to take the ground upright.

60' Motor Sailer Swallowtail - Kasten Marine Design, Inc.
60' Swallowtail - Click for Larger Image

Interior & Exterior Layout

Right forward is a generously sized owner's cabin, with "island" berth forward and plenty of storage in twin wardrobe cabinets and bureaus to each side. Aft of the owner's cabin are twin compartments, one for the head and another for a bathtub and shower.

Aft of the head / shower compartments is a full size galley to starb'd with a dinette to port.  On the starb'd side of the companionway is the entry door to the engine room.  The engine room is of ample size, and has a wrap-around seat / bench for tending to all the machinery while comfortably seated.

Every boat needs a "garage" or "cargo hold" where the inevitable accumulation of interesting stuff can be stowed, so aft of the engine room below the saloon is a large store room / laundry / workshop. And... just aft of the store room is the lazarette, also quite large for storing lightweight items.

Up on deck, within the Pilot House are two swivel pilot chairs, which allow them to be used as lounge chairs when facing aft, or as piloting chairs when facing forward. A large 'saloon' is aft of the piloting area which contains standard furniture, not built-in joinery.  This is to create a more comfortable and informal lounge on deck, where the view is best. The piloting area is part of the living area, and vice versa. In the saloon / galley, a day-head is located to starb'd.

This design has made use of a "widebody" deck house in way of the saloon in order to maximize the interior space. In other words, the house sides have been moved out to within around 8 inches of the bulwark top, providing a "catwalk" just inboard of the bulwark for access to the house sides when needed. 

On each side of the pilot house, a door leads out to a side deck, allowing easy access to each side for docking; to the PH roof via a ladder on each side; and to the fore deck via a few steps. A sliding door is located on center right aft in the saloon and provides easy access to the aft deck. Due to there being no side-decks, the aft deck accommodations can extend right up to the aft face of the house, where we have placed a service counter, with sink to port and grille to starb'd.

On center aft... another nice surprise... a flip-down swim deck to provide easy access to the water; to the shore boat; or to a quay or side dock via a passerelle plank that will be arranged to swivel to either side or aft, and will also be able to articulate up and down.
 

Summary

The Swallowtail 60 is very much a motor yacht in terms of having a generous on deck saloon / pilot house and the general hull form of a trawler yacht, but is also very much a sailing vessel having ample sail area. The emphasis has been to make this a 100% capable motor yacht, and also a highly capable sailing vessel.  Altogether a fine nomadic watercraft for family and friends.
 

Design Genesis

As with our other designs in this series, the hull form for the Swallowtail 60 has been adapted from real trawlers.  These US West Coast fishing vessels have to operate in all weathers - including in the Gulf of Alaska, a place where the ocean is... well, not so nice. Our aim has been to retain the excellent sea keeping qualities of those working craft, and to refine their lines into 'yacht' form to achieve a more easily driven hull with relatively light displacement. See the following links for vessels in the Gulliver / Greatheart series...

Greatheart 36 | Vagabond 36 | Gulliver 46 | Greatheart 48 | Greatheart 54
Greatheart 60 | Swallow's Nest 60 | Swallowtail 60 | Braveheart 53 | Braveheart 63 | Swallows Nest 70

In order to achieve a proportionately longer waterline and more interior space without increasing boat length, we developed another series of designs based on the same hull form, but with a more upright stem and transom. Combined, this reduces the overhangs and increases the WL length to gain more interior space with less overall hull length. Check out the following links for boats in the Vagabond series...

Vagrant 49 | Vagrant 70 | Vagabond 50 | Voyager 52 | Valdemar 53 | Valdemar 70
 

Swallows Nest 70 Trawler Yacht - Kasten Marine Design
Larger Swallows Nest 70 - Click for Larger Image

SN-70 Side Aft  |  SN-70 Above Aft  |  SN-70 Side Fwd  |  SN-70 Above Side

Having the same hull shape, the Swallowtail 60 can also be made longer as shown in the 70' model of the Swallow's Nest above.  In so doing the Swallowtail design would easily be able to accommodate a pair of guest staterooms, or one guest cabin and a large office / studio...