The Case For Aluminum

Why should you select a heavy duty Welded Aluminum Vessel?
Simply put, a welded aluminum hull is the most durable, lightest, longest lived and cost competitive product available today for vessels. As a basis for this, look into any trade magazine and note used vessels for sale. You will find tens, if not hundreds of vessels that were built over 25 years ago for severe services such as the Gulf of Mexico oilfield, that are still in service. Many of these 25+ year old vessels are displaying the versatility of aluminum by being converted to different uses, getting repowered and providing their owners even more service life. These vessels are simply and quickly repaired, when required, and easily retrofitted to meet changing operating requirements.

Durability and Reparability
Take note of any vessel that has operated in a fishery or the Gulf of Mexico oilfield for twenty plus years. What you will see is a vessel that probably has dents across its stern, a few gashes in its sides and some holes poked in it. But that vessel is still in service. Also take note of any fiberglass boats that has operated in the Gulf of Mexico for over 20 years. You won't find one. They can't hold up to the abuse. Aluminum will bend and have a ductile failure, while fiberglass will crack, splinter and break up. When you look at these 20 year old vessels, take note of what has been repaired and what hasn't. The holes poked through the skin probably have a patch welded over them and that's about it. The reason, the boat has stayed on the job, working day in and day out, earning its paycheck.

Flammability
Because aluminum is a metal, it will not burn. Fiberglass vessels will burn. There is a current trend to construct fiberglass vessels with fire retardent resins, but they will still burn once started. With fire retardant resins, QA/QC must be strictly adhered to since blistering and delamination are a greater possibility with the use of these resins. Aluminum can be used in vessels that require structural fire protection, such as SubChapter K vessels. In this case, spaces are evaluated and insulated accordingly to provide the appropriate fire boundaries.

Ease of Customization
Aluminum vessels lend themselves to tremendous amounts of customization. We can start with a basic hull and easily change the beam, cabin layout, decks, horsepower, etc. Bulkheads are easily shifted, cabins enlarged much more easily than other materials. Since we utilizie CAD/CAM, we can quickly modify existing hulls to suit particular needs while minimizing cost.

• Corrosion Resistance
  The salt water corrosion resistance of 5000 series Aluminum has been well documented beginning with tests by ALCOA in the 1930's and continued by other companies and regulatory authorities to date. The test that is most commonly referenced was conducted by ALCOA whereby they submerged test coupons of 5000 series aluminum in salt water. After 30 years, the samples had no appreciable weight loss and the test was discontinued. When corrosion problems are associated with aluminum, it is generally associated with electrolysis. Electrolysis occurs when an electrical current is applied to two dissimilar metals. When a current is applied, the less noble metal will sacrifice electrons and therefore corrode. Attempts to eliminate electrolysis are therefore concentrated on preventing electrical currents from flowing through the hull and providing a more noble element to sacrifice itself before the hull (sacrificial anodes). Therefore, any builder of aluminum vessels should be concerned with the following:

• Proper grounding of electrical components: In an aluminum hull, all grounds should be terminated back to their source. All 12VDC grounds should be terminated to a common/isolated bus bar and run back to the battery. Of particular importance, high amperage devices such as radars should be isolated from the hull. All AC loads should be isolated and run back to their motive source.
• Proper aluminum alloys must be used for construction. This includes plating of 5086 or 5083 grades for hull material. The 5000 series signifies aluminum alloys with high magnesium content and therefore high corrosion resistance. Wire to weld these alloys should be 5356.
• Proper placement of Sacrificial Anodes. Adequate sacrificial anodes should be attached to the vessel. These anodes provide a metal that is "more noble" than the aluminum hull and will give up its electrons before the aluminum hull.