Imagine yourself on a Marlow Yacht....

TECHNICAL INFO  Fuel Efficiency  

Our efforts in reacting to the probability of increased cost of fuel has been a relentless pursuit of technology resulting in yachts that are roughly twenty percent lighter than a single skin solid laminate of materials normally seen in “heavy” displacement yachts.

We embrace Kevlar and other highly engineered fabrics specifically designed to absorb the loading seen on board a yacht on any sea. We further refine that technology by infusing a SAN foam sandwich, resulting in an I-Beam like cross section of the hull laminate. To maximize the enhanced strength characteristics of this virtually bullet proof technology, we utilize modified epoxies that are matched to the strength of the individual fibers selected. It would be of little or no value to laminate these exotic high strength fabrics with a common polyester resin whose ultimate yield strength is only a fraction of the surrounding fabrics. In other words, the resin would fracture and fail long before the enormous strength of the fibers was utilized.

By embracing this advanced technology, we are able to reduce the weight per square foot of laminated area significantly, while producing a laminate far more rigid than a common single skin of roving, chopped strand mat and polyester resin. Were one to design a single skin laminate equal in strength to sandwich construction, the weight of the total laminated component would be several times that of cored construction utilizing today’s materials and technology. In lieu of attempting to build such an outrageously thick laminate with its attendant liabilities, most manufacturers reduce the unsupported panel size by elaborate stringers and framing to reinforce the physically weaker panel. This leads further into the rapidly escalating domino effect of more weight, less usable volume for a given size and a much more restrictive layout choice due to the need for additional framing, bulkheads and gussets, to say nothing of the loss of valuable sound and vibration dampening the sandwich construction brings.

Since fuel usage is directly tied to the mass that must be moved, all things being equal, it behooves us to reduce unnecessary weight wherever possible. In so doing, the canoe body draft can be and is reduced by simple immersion data; e.g. for each 64 lbs of additional weight on board, one cubic foot of immersed surface must be added to carry it.

Other benefits that are part and parcel of the quest for lighter structures are the automatic lowering of the center of gravity of the yacht. Weight above the center of gravity of a yacht could never be described as a benefit under any condition. Since the center of gravity on a well designed yacht fifty or so feet in length is typically only 3-5 feet above the design water line, a bit of simple mathematics shows us the detrimental effect of raising the center of gravity. In comparing a heavy solid laminate that has been unequivocally shown to be weaker for a given laminate schedule compared to a cored one, the superstructure with its large amount of framing can weigh up to 50% more than a modern cored structure. This additional weight must be carried by the propulsion system at higher horsepower and therefore additional fuel cost. To further evaluate the effect of older technology still in use, if the center of gravity is raised by only one foot, a very serious reduction in form stability results. Our own data suggests that much or all of the original economy achieved by the rounded sections can be lost if additional active stabilization is required for comfort, since active stabilizer fins work by throwing a large fin in counter to the water flow past the yacht. This motion adds significant drag to the displacement trawler, with the figure increasing significantly as the sea conditions increase.

Since the righting moment created by the combination of heavy superstructure and round sections is compromised, the normal tactic is to load the bilge with iron or lead to act as a counter to the heavier superstructure and topsides. Once again the domino effect rears its head, requiring more draft to support the ballast and more horsepower to keep it underway.

 The subject of ballasting a yacht is one that can provoke a lively point-counterpoint by those fully versed in the dynamics of roll moment and the pendulum effect. An example of that argument can be found in the disastrous Fastnet race where more than one dozen fine sailors as crews on ocean racing yachts were lost due to the complete rollover of their vessels. It is interesting to read the findings of the investigative committee regarding the frequency and severity of the capsizes. The conclusions reached were that even though the yachts were fully ballasted, the loss of the mast by violent winds or wild gybes virtually guaranteed capsizes. The obvious inference being that despite the enormous ballast far below the center of gravity, without the stabilizing effect of the mast to act as the pendulum so to speak, the yachts were not as stable as if they were constructed without ballast. That evidence certainly gives one cause to carefully consider a heavy topside opposed by thousands of pounds of ballast. If one can simply reduce the weight of the topside while increasing its strength dramatically by more advanced engineering and materials, it would be difficult to make a plausible argument against doing so, other than economy.