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Sea Force IX’s Monolithic Construction Explained

This is a layman’s explanation of Sea Force IX’s “Monolithic” fiberglass construction and why it is the best choice for large performance sport fishing vessels.

Sea Force IX’s management, engineering and key lamination supervisory staff has been together for almost two decades. We believe this is a vital element to our unblemished record of large, cored fiberglass sport fishing vessels running the oceans of the world.

Our “Monolithic” construction methodology is unique to the industry and is founded on three pillars. First is the human element already noted. The other two are premium materials and a specific method of construction based on sound engineering, industry support and a rigid quality control system.

Our fiberglass parts are made from 5axis-milled molds that are extremely accurate. We start the hull with high-temp gel coat specially formulated for us. This is backed up with a fully engineered laminate of blended Vinylester resin, non-woven glass fabrics and closed cell structural foam core. The Vinylester resin has amazing physical characteristics, high temperature tolerance and inhibits the molecular intrusion of water. The non-woven glass is all US manufactured by the leader of glass technology and is hand laid for a consistent glass to resin ratio. The closed cell structural foam core is wet-bagged under vacuum with each piece sounded after cure to assure total adhesion. Any spot of core that the QC system suspects is removed with new core applied and re-checked. Critical areas like thru hulls, struts, etc. are not cored but are solid glass built up with additional glass layers. The keel is also solid glass with all layers being overlapped and then filled with layers of solid timber encapsulated with resin and glassed over.

After the primary hull lamination is complete and signed off, the full length fore and aft stringer system is installed and glassed over stem to stern. These stringers vary in height and thickness (8” in the engine area) and are engineered to handle the speeds and stresses of the high horsepower propulsion systems we install. The athwartship stringer system installation follows and is completely glassed, followed by the four main structural composite bulkheads and the marine ply crash bulkhead. Three hull side beams on each side complete the hull lamination and the hull is ready to be pulled from the mold.

Once out, the hull structure is weighed and baked. The baking process is another of our “unique to the industry” procedures with the hull wrapped and baked for a period of time and then allowed to cool naturally. This process assures the laminate is completely cured and ready for production and the painting process. All the above procedures apply to all the large fiberglass parts (ie: superstructure, bridge, etc.) and is why we confidently let our customers choose any color they want for their Sea Force IX. It must be noted here that after the parts are baked, ALL secondary structural glassing is done with West System epoxy resin.

The ‘Monolithic” structural plan continues with the composite floors and soles bonded to the stringer grid and glassed to the hull. The forward accommodation bulkheads are glassed to the hull sides, composite floor and the deck. The hull to deck perimeter, cabin to bridge connection, leisure deck and any other assembled components are completely glassed together. The interior cabinetry that contacts the hull is glassed as well. All to this point describes the most comprehensive structural envelope available. This “Monolithic” methodology allow us to save weight without sacrificing structure, increases performance and provides the industry’s best gallons/mile economy for a comparable vessel.

Our quest to be the best does not stop there. The exterior surfaces of our sport yachts receive the complete “Awlgrip” system. This starts with spray able fairing primers that are long board and sanded after cure. This is followed up with the 545 epoxy primer and two coats of topcoat. We have excellent support from the Awlgrip representatives through this process and the resultant fit and finish is second to none. The bottom paint area is sanded and two coats of epoxy primer are sprayed on with a sanding in between. Two coats of sprayed anti-fouling pain complete the impervious moisture barrier. Our 81’ hull #1 was surveyed five years after launching and was found to have no moisture in the hull laminate and the dark blue hull was still Bristol.

Some would argue that fiberglass construction of a vessel of this size was not as advantageous as an aluminum hull. We think just the opposite and our position is not only supported by this explanation but by many successful vessels 100’ and above the world over. That is not to say that any material improperly used will not experience failure as evidenced by the recent sport fish photos that have been circulating the web. The same case can be made for aluminum.

Aluminum plate as it comes from the mill has all the strength it will ever have (Fiberglass' strength is cast IN shape). The process of bending the plate to the shape of the hull affects the molecular structure depending on the severity of the bend. Aesthetically, the designer on an aluminum hull has to design shapes that work within the ability of the plate to be formed whereas the fiberglass hulls can have much more pleasing shapes and detailing The welding that follows not only anneals (softens) the metal but also distorts the plates. A completed bare aluminum hull is not a pretty sight. To bring an aluminum hull to a yacht finish the metal has to be ground (oxidation starts as soon as the surface is broken), washed, etched and a bonding primer applied. Then fairing putty is troweled onto the hull and multiple long board sanding – filling cycles begin. Due to the distortion of the aluminum plate surface, this fairing putty can be as much as ¾” thick (Our fairing primers will not finish over 1/16” thick). Provided the fairing process is done properly, the topcoat is applied. Another undesirable attribute of an aluminum hull is the electrical properties of aluminum in salt water. Electrically speaking, an aluminum hull is a floating anode and is less “noble” than the other metals onboard. Any inconsistencies with the electrical bonding of the vessel will allow electrolysis to eat away at the hull. Many aluminum yachts actually induce an electrical potential to the hull to prevent electrolysis. Fiberglass is electrically inert.

Although this explanation has gone long, it is just one element of the Sea Force IX saga as all of our departments have similar stories to tell. Key people, top shelf equipment with vendor support, Sea Force IX proven techniques, all backed with success over the years.

We encourage a factory visit to see a Sea Force IX Sport Yacht under construction. If you have any other technical issues please let us know.

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