Want to know another reason why Northern Marine is a cut above? See how they marry the hull and deck structures.

By. Bill Parlatore

I have been following the construction of Northern Marine 5706 for some months now. I wrote about some of the systems design and installation to showcase what makes this trawler yacht unique among the yachts coming out of the pleasure boat industry. And I plan to continue this systems discussion as the build progresses. With a heritage of commercial fishing and large working trawlers, every element of the Northern Marine line is a study in big boat construction, adherence to ABS standards, and a rugged, no-nonsense approach to all aspect of the boat.

I asked Stuart Archer, Northern Marine’s general manager, to review with me photographs taken of the critical hull/deck joining procedure, as Covid-19 keeps us at a distance. The process was well documented, however, and I believe speaks for itself that there really is no comparison to other trawler yachts of this size.

Stuart said the hull/deck bonding process involves a couple of dedicated teams, who began work in late July and continue today. It is a very time-consuming effort that can only really be justified by a custom builder. The two-man teams may spend a couple of days on each step along the way, sometimes longer, as they grind, clean, wipe down, fill with structural filler & adhesive, apply mat and several layer of fiberglass material depended on the task.

Once the hull and deck are fully attached, the teams move onto glassing bulkheads to decks, decks to stairways and other structures, and a host of other tie-in jobs besides the crucial hull to deck joint. The laminators continue working around the boat, glassing every joint where components meet, bonding on both sides of all surfaces.

Here we see the finished foredeck of another 57-footer, in this case finished with synthetic teak decking and brightly painted caprail.

Stuart said the boats have become less commercial in profile and detail, and the move towards a more yacht treatment and finish is easily accomplished. That is evidenced by not just the synthetic teak deck, but also by the single vertical windlass with single anchor. That is quite a departure from past Northern Marine yachts with big hydraulic cable drums on the foredeck to handle anchoring gear. About 70 percent of today’s yachts have a single large anchor, yet anchoring gear remains hydraulically driven.

Stuart also mentioned the current interest in stern capstans for managing a stern anchor.

The complete deck structure, ready to go into the hull. Notice that the crew has started the fairing process to finish the exterior surfaces to show the lovely lines of the profile. This fairing material will be coated with a high build, high density primer. This primer acts as a barrier coat to seal the surface and make it ready for painting.

Note the I-beams through the window frames used to lift the deck structure. I was impressed with the strength of these window frames, capable of handling the weight of the deck structure, which can weigh up to 15,000 lbs. And the total rigidity of the deck, with none of the sagging seen on many other decks once lifted off their frame cradles.

The deck structure lifted onto the hull and resting on ledgers on the hull ready for the glassing process to begin. You can see the bow thruster, the location of the port stabilizer, and the solid, full-length keel on the bottom of the hull.

The non-opening portlight, a new addition with 5706, will bring plenty of light into the master stateroom, and is installed as per ABS standards, with a hinged deadlight cover that can be closed for watertight security.

The exterior stairway up to the flybridge and boat deck adds volume to the interior and is one of many ways to customize a yacht to meet the needs of its owners.

The deck sitting on the hull ledgers, ready to be glassed in. The 1.5-inch thick, eight-inch wide structural foam fill the gaps between the hull and deck. It will be permanently glued in with structural adhesive and then glassed over with 2408 biaxial E-glass cloth with ¾-oz mat backing to form a solid structure between the deck, foam, and hull. This 2408 glass cloth is ideal for high strength fiberglass reinforcement. Its dense flat weave provides a superior resin-to-glass ratio and is also the perfect material when the builder wants to eliminate print-thru.

Every joint is glassed over on all sides, top and bottom. As a result, the deck, hull, and other components become essentially one big part.

You will also see there is no inside flange for the cap rail at this point, and the hull side is not fair and does not yet have a yacht finish.

The deck structure at transom is shorter to accommodate the tumblehome of the hull so that it will fit into the hull. The structural foam, which might be Core-Cell or Divinycell, will be glassed in from both sides. Note the aft lazarette opening into a space where the hot water system, batteries, and other major pieces of equipment will reside.

The aft cockpit is now structurally one rigid piece. It is ready for installation of cockpit cabinets and other finishing treatments, which will include a form of non-skid or synthetic teak.

Notice there is now an inside caprail wood frame which they will use as a temporary mold to lay up the caprail flange where the laminator’s hand is. It will later be recreated in foam and fiberglass for a permanent caprail. Two layers of 2408 biaxial E-glass go over the side deck, structural filler, and hull side to complete the topside bond of the deck and hull.

This new flange serves as the landing place for the new fiberglass caprail. The area will be thoroughly glassed in with a ratio of 30% resin to 70% laminate for ultimate strength.

You can see the fiberglass work done to tie the deck and hull together from underneath. A flange off the hull extending out about a foot to ensure the deck resting on it will have maximum overlap. Structural adhesive on the flange bonds the deck and hull pieces together, then the team puts a 45-degree angle on the inside edges of the flange and deck which is then glassed over to permanently secure the hull flange and deck together, as well as bulkheads and other tabbed structures. This results in the absolute best in bonding hull and deck together from both sides.

It is interesting to compare this approach to traditional pleasure boat building. While this is time-consuming, it provides the most rigid structural bond possible, essentially making the hull and deck one structure.

Such a labor-intensive approach is simply not practical for production boat builders, who typically use a combined adhesive/mechanical methodology.

There may be a couple of inches of overlap between the hull and overlapping deck, which provides a narrow surface for applying a bedding compound (either a flexible product, such as Sikaflex, or permanent adhesive like 3M 5200), and the hull and deck are then mechanically through-bolted together every six to eight inches. This has been successfully used in pleasure boat building for decades and is standard practice for many popular trawler yachts.

There are numerous YouTube videos that show this adhesive and mechanical process. Even though this may be standard practice, it does not offer the same ultimate rigidity and structural bond as glassing over a foot of overlap of deck and hull. And when the bolts and nuts are tightened during construction, this introduces the possibility of squeezing out much of the bedding compound from the mating surfaces, creating a dry spot.

Additionally, after years of use, and perhaps thousands of miles in different climates, many sealants and adhesives lose their elasticity and adhesive qualities, or the chemical bond weakens.

Ask any owner of a top-quality yacht who has noticed, after some number of years, the saloon portlights, for example, begin to leak as the bedding compound fails. This is the nature of boats, and the same can happen on the hull to deck joint, allowing water to find its way into the boat. While 3M 5200 is the industry standard for permanent adhesive, can it be expected to uniformly hold up after decades of structural movement?

Glassing both sides of all joints and mating surfaces ensures the ultimate in structural integrity and water tightness. There won’t be any twisting of the hull and deck in heavy weather, possibly stressing bulkheads and other tabbed attachment points, and potentially creating leaks and joint failures over time.

If you have sailed offshore in heavy weather in a production boat, you no doubt experienced the hull and deck working in a seaway, often making it difficult to close or open interior doors as they flex at sea.

Note the thickness and consistency of each layer that comes from the resin infusion process. The laminate schedule is a combination of fiberglass mat, Kevlar, and multiple layers of fiberglass cloth. The hull is solid fiberglass up to one inch above the waterline, near the keel will be double this thickness.

The caprails are built in sections from high-density structural foam, shaped to the required pattern. Then they are overlaid top and bottom with two layers of 2408 glass. These sections will be glassed together as one piece, sanded smooth, and painted to the owners’ desired color.

As finishing touches such as the caprail go on, the laminators move into the boat and begin on overhead liners, building the boat’s hard top, mast, and the fiberglass cabinetry that goes onto the flybridge and in the aft cockpit.

All the fiberglass components will be glassed together top and bottom to make a single, supremely strong structure that will wear the Northern Marine nameplate. It does not get any better than this when it comes to securing the deck and hull structures together.

As Stuart Archer pointed out, only a custom builder like Northern Marine can justify such time-intensive attention to detail.

Which is why, in the world of bluewater passagemakers and expedition trawler yachts, Northern Marine is second to none.

Northern Marine Knows Its Priorities

By: Bill Parlatore

As I continue to follow the construction of Northern Marine’s newest 57-foot yacht, I had the opportunity to discuss some of the engine room details with Stuart Archer, Northern Marine’s general manager, and production manager, Randy Stoneman. The Northern Marine crew plan to put the deck superstructure on the hull (5706) next week and are busy with the many details necessary before that can happen. Furniture modules and other large components need to go into the boat before the deck goes on.

I was particularly interested in learning about the new yacht’s fuel system, especially given both Stuart’s and Randy’s experience with commercial boats and big yachts. Stuart once told me the problem they face is fitting big-boat mentality and systems into smaller expedition yachts. It is the opposite from most pleasure boat building, and that fascinates me.

As I asked a few questions about fuel systems, Randy began with the basic issue of transferring fuel into a big boat, which is handled differently from what we experience in typical pleasure boating.

On large yachts and commercial boats, with fuel tank capacities of 6,000 to 10,000 gallons, it is simply not an option to come alongside a fuel dock and have the dock attendant hand you a fuel hose nozzle. These big boats take on fuel at commercial facilities or where tanker trucks can reach them. They use Cam-Lock fittings to lock onto the boat’s fuel fill and fuel is pumped under pressure at transfer rates of many hundreds of gallons per minute. To move this amount of fuel safely yet quickly, operators must use extreme care to coordinate and control the process at the boat’s transfer manifold, and fuel tank venting is daisy chained to keep the high-speed transfer going smoothly. No pressurized geyser of a “burp” out a vent from overflow is acceptable.

As Stuart was quick to point out, refueling big yachts with large fuel capacities obviously does not happen very often, especially expedition trawlers that carry enough fuel to go halfway around the world.

There are three tanks on 5706. Two saddle tanks in the engine room each hold 950 gallons, and there is a third tank located forward under the guest stateroom that holds 560 gallons. Stuart said they are not setting up this boat to use Cam-Lock fittings, as it is not necessary for a smaller expedition yacht that will go cruising, not fishing for months in the Bering Sea.

Similar but Different

Randy explained that since each Northern Marine yacht is unique, built to accommodate the desires and needs of its owners, the builder doesn’t work off carefully drafted schematics for systems as one expects to find in a production boat building operation. Even so, the experienced team knows all the required components, and what needs to connect with what. So, all systems, such as the fuel system, are developed and installed as the boat comes together. There are obviously many similarities from boat to boat, but everyone looks to see where it can be done better or use newer materials.

An owner might want his new yacht to include a superb Alpha Laval fuel polishing system from Sweden, for example, which costs an additional $30,000. This premier centrifuge fuel polishing system is the best of the best, but somewhat overkill for the kind of cruising most Northern Marine owners plan to do. However, bad fuel is not always assured no matter where one travels, so a quality fuel polishing system is standard on all Northern Marine yachts. The company has had great results with well-engineered systems from companies such as Parker Hannifin.

The fuel tanks are tested to 2psi and in addition to sight gauges, the builder installs Maretron transducers on the bottom of each tank to measure pressure of the fuel column accurately and convert it to fuel levels electronically.

When a new boat is complete, and ready to take on fuel for the first time, a fuel truck comes to the Anacortes yard, and fueling begins. The trucker is instructed to pump out precisely one hundred gallons, then stop. Crew in the engine room carefully mark the sight gauges and calibrates the electronics, as necessary. Then another hundred gallons goes into the boat, and the process is repeated until each tank is full. This only needs to be done once for a new boat and is the most accurate way to know without question what the fuel capacities are and specific fuel levels regardless of the shape of the tanks.

Craftsmen Quality
The fuel lines on all Northern Marine trawlers are custom made by the builder using 316 stainless steel tubing. With a fully equipped shop in-house, the stainless tubing is precisely shaped to fit perfectly and connect manifolds, valves, filter assemblies, and other connections in the engine room.

This brings up an important point about fuel line connections. I have been on too many boats where the boat builder used plumbing pipe fittings to make fuel line connections, especially on fuel manifolds where all the fittings are lined up neatly. It is an illusion of quality.

Pipe fittings are tapered and seal by thread deformation. They are not reusable, but much more importantly, they are not positionable. That means when the pipe fitting is properly tight it is not likely pointing in the right direction. So, the builder unscrews the fitting enough to face the right way and relies on thread sealant to prevent leaks. Look at any manifold where all the pipe fittings are facing the same direction, and I guarantee you none of them are tight.

Northern Marine uses the vastly superior connections offered by metal-to-metal JIC flare fittings on any short hose whips placed on the ends of stainless steel tubing when connecting to some other component in the system that requires flexibility.

Installing stainless steel fuel lines and using industry-standard flare fittings are more expensive and labor-intensive, but they are absolutely the best way to eliminate leaks, reduce the number of fittings, and the connections are permanent. It does not get any better than this.

Built Tough for a Reason

The forward fuel tank is for storage, and fuel is transferred to the saddle tanks as necessary, and there is a crossover between saddle tanks, each with a “manhole”-sized inspection port.

Randy explained his philosophy when it comes to the engine room. “Assume everything is going to break in the worst of conditions.”

A great example of that philosophy, and one of particular interest to me, is that the builder does not use pickup tubes in the fuel delivery system, but rather valves and fittings located at the bottom of each tank. This ensures all fuel is available, always.

(I offer a personal experience. The owner of a sistership told me that his port engine would quit if he was in rough seas and the fuel gauge indicated less than half in his port fuel tank. A combination of insufficient or poorly located baffles in the tank and a short pickup tube caused this issue. It always stayed in my mind and I never let my fuel level go down to that level, which is not really the solution.)

When I shared this experience with these professional boat builders, Randy finished my sentence, saying that the pickup tube was too short. Wisdom from experience.

He added that fuel coming out of the bottom of the tank also make for a happy fuel pump. Pumps love to push fluid, but they are terrible at sucking fluid, such as a tall pickup tube. (That is another experience I can relate to. My vacuum gauge for the port engine registered alarming vacuum readings, far beyond spec. Eventually the engine distributor added a booster pump to the fuel delivery system, to push fuel to the engine. The engine fuel pump was working way too hard to draw fuel out of the tank and was headed for an expensive failure.)

Both saddle tanks on 5706 supply fuel to the John Deere main engine and generators. And there are switchable fuel filters readily accessible in the engine room. In fact, everything is very accessible in this engine room, and that is no accident.

Stuart said he builds boats around the engine room and access to its systems, another nod to his commercial and big boat background. Every Northern Marine yacht has full standing headroom, and no owner will ever have to kneel to change the oil in a generator.

“If the new owners want certain changes in the galley or accommodations, I can always make the boat bigger, but there will be no compromises in the engine room.”

That pretty much sums up the level of detail and expertise that goes into the fuel system of a Northern Marine trawler.

There is never a doubt where the builder’s priorities are.