39' Offshore Power Boat - Steel Trawler Yacht for economy.
Designed by
Yves-Marie Tanton, Tanton Yachts, Inc.
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      The growing popularity of the powerboat segment has touched the sailboat population. With advancing age approaching, the classic sailor will be drawn to this kind of boat. It is my intention to fulfill this continuing desire to be on the water, by introducing this Trawler. I call it a Trawler until I can find a better name to describe this practical approach to power  boating.
     It is built in steel for brute strength, simple lines for construction purposes, heavy displacement, and low power because that's all that's needed.
     Quite a few years ago, I designed several sailboats with twin keels and this approach is also adopted here. Motor boats should be able to sit on their bottoms. I do not understand why manufacturers and marketers are not more actively pursuing this feature. Resistance to rolling will be an additional benefit.
     I am partial to steel construction, and for this type of boats which is very likely to be built in many different parts of the world, the material makes sense. The overall size of the model is related to standard lengths for steel plates. Building Artica ideally requires only 2 sheets per sides above the chine line. The scantlings have little to do with saving weight and are very substantial by any account.
     Minimum thickness is 3/16" (5mm) for the topsides. A gap of 3/16" is maintained between the hull shell and the frames to keep the fairing and welding of the stringers in one direction, to minimize welding distortion. The bottom is " (6 mm) thick. The framing system in the deadrise, has no longitudinals to collect water and rust with the exception of the fore and aft tanks and engine beds. The frame spacing is halved in appropriate locations such as in the way of the keels for instance. About the appendages; the schedule 80 pipe leading edges and the " bottom  will not flatten if one hit a reef. The boat is heavily insulated.
     The lines plan is indicative of the transition from sailboat to the relatively sedate motor boat represented by Artica. Not much difference, except for the width on deck of the transom.
     I have adopted the same philosophy already developed to the simple sailboat shapes for metal construction. Therefore a single constant angle is drawn for bottom and topsides. There is nothing simpler. Of course it gets to be explained that I do not believe in deep sections in the bow steering the boat for you. I prefer to create lift and a small angle of incidence. If a bow thruster is installed, the placement of the hole will be less obstructive and will give the least resistance.
     The stern lines are double ended on the waterline, only to become a wide transom some ways above. By exaggerating the fineness of the load line, I expect to improve and better control  backing down the boat. Furthermore, the large outboard rudder will make sure of it.
     The keels, being an inherent part of the package, I want to explain their functions above and beyond the obvious ability to rest level on a flat bottom. They are twin keels and not just bilge keels. They are streamlined with the flat surface on the outside and curved on the inside. On a sailboat, I would introduce some toe-in. In this case, I kept them parallel. Maybe there will be a constriction of the water flow strong enough to lift the stern. The jet flow will improve propeller efficiency and therefore direction. Effective when the boat is moving, the keels reduce roll when it is induced. Counteracting leeway with the fin on the lee side, the flow lines are forced to follow the upper and lower surfaces of the weather fin, whose lift acts downwards; producing a righting moment that increases stability at the same time. I believe directional stability and maneuverability are enhanced.
     Hull efficiency has to be complemented by machinery and top notch mechanical installation. The promise of economical speed is based on a diesel power plant of less than 100 H-P. Many engines are available in that range, including new and rebuilt engines. I am not too specific at this stage, because I am sure that besides changes to the interior arrangement, the engine finally chosen will vary with preferences, pocket book and availability.
     Also a consideration is the added power necessary for ancillary systems. You can expect a speed from 6 to 8.5 knots within the speed length ratio the boat is designed for.
     Tankage is up to 600 gallons of fuel; and 250 gallons of fresh water, the distribution of which is centralized to keep the weight even on each side for proper trim.
     The 8' long engine room is below the salon cabin sole and has access from the top as well as through a watertight bulkhead located in the aft cabin shower room.
     Many things can be said about the accommodation plan. I expect, and designed-in a lot of possible permutations. The interior as drawn features an aft cabin with toilet and separate shower. A roomy stateroom aft permits different combinations of joinerwork. This is presumably the owner's cabin. The way I see it, the deck salon with galley will be popular to the cruising man or woman.  What makes it work are the two doors to the outside at opposite ends of the salon.  So within sight, one can steer cook and watch TV. Even navigate.
     Going forward down below, I designed a second cabin to port with upper and lower bunks for guests. To starboard, I have located first the electric panel, to service lighting and the electronics, with the steering system behind, then a refrigerator followed by a washer dryer. A bulkhead is projected across the width of the boat for a second head, also with separate shower. There is room for a work bench. You find the anchor-chain inside the forepeak, behind a watertight door. 
     The elevation view on the outside has the advantage of a real ship-like pilothouse with fore and aft side decks with high bulwarks. Aft, the flush deck will permit stowage of a proper dinghy. It is expected that there could be the addition of a mast and sails. In this case the
main boom  will double as a crane. A platform can is welded aft to protect the rudder and to provide access to the stern deck. The bow is straightforward with room for windlass and anchors.
     The design of this little ship blends an economical approach with aspects of a traditional  work boat and the seriousness of a tug. I hope to have conveyed by this design what I am looking for, so that I can pursue in the same vein the larger models I have in mind.


Length. 41'-6" includes platform and rudder.  12m65
Length overall 39'-5"  12m01
Length on deck 38'-7"  11m76
L.W.L 36'-6 1/2"
Beam. 14'-6"  4m42
Draft. 4'-7"  1m40
Displacement. 31,856 lbs. 14T.
DSPL/L: 300