Publish Time: 2021-08-02 Origin: Site
The material of the hull defines the characteristics of the ship. However, when buying a ship for the first time, many people pay little attention to the choice of hull materials. The appearance of glass fiber (FRP or FRP) ships in 1960s completely changed the industry and made it a normal state. However, GRP is not alone in the market, and it is worth looking for other alternatives before deciding what your first or next ship will be.
Some advantages and disadvantages of FRP materials must be known to everyone. In this article, I will introduce another interesting alternative material, aluminum alloy. As you will see, the aluminum ship has its own characteristics and can be an excellent substitute for GRP. Therefore, let's take a look at every characteristic of aluminum ship, which must be considered before deciding whether it is suitable for you.
Weight
As we all know, the aluminum shell is light, the density of aluminum is 2.8, and the density of steel is 7.8. Specifically, they are much lighter than steel, but they are also lighter than GRP. Light hull provides better performance (speed), especially in light wind. Speed is not only applicable to boat racers. Light sailing also means that you are unlikely to need to use the engine, because you can do it under the sail even when the wind is light. Generally, light hull can also be designed with shallow draft, so as to improve the accessibility of shallow rivers and bays. Finally, light hull translates into lower fuel consumption (simply imagine less volume dragging through water).
Intensity
The strength of aluminum is probably the most attractive aspect of aluminum boats. To put it simply, for aluminum, the possibility of hitting the perforation on the hull is much less than that of glass fiber. This is one of the reasons why aluminum alloy is widely used in large aircraft with the highest requirements on material strength. When you cruise between icebergs, you must increase the safety of the aluminum hull. Obviously, this applies not only to icebergs, but also to anything that can or may hit you, from underwater rocks to floating logs or containers. We often hear stories of aluminum boats trapped in rocks for several days, but they resist vibration and sag without breaking. These boats can be repaired relatively easily. Unfortunately, similar stories of fiberglass boats stranded on rocks never have a happy ending.
Longevity
As the saying goes, "fiberglass blisters, wood rot, steel rust". But what about aluminum? One of the most important problems about aluminum raised by many people is corrosion. However, aluminum is actually one of the least corrosive metals. This is especially true of the low corrosivity of aluminum for alloys used in marine applications. Aluminum alloy does not contain steel or iron, so it will not rust. Aluminum can and will certainly undergo oxidation. However, this oxidation produces a hard alumina surface layer, which can actually prevent further corrosion of the underlying materials. If the proper alloy and welding wire are used for proper construction-and remain unchanged, the aluminum ship will last for several generations.
Fire protecting performance
Fire is the most dangerous of all dangers at sea. Although some materials used to build the hull (such as fiberglass or wood) will burn quickly and spread the flame, aluminum will not burn. Moreover, aluminum needs a temperature higher than 500℃ to melt.
Maintenance
Because aluminum boats are not easy to corrode, they don't need to be maintained as often as steel or wood (especially painted). Right? Well, this is where opinions begin to diverge. Keeping paint attached to aluminum is one of the main problems of aluminum ship owners. If there is an opportunity, please pay close attention to the waterline of the aluminum boat, and you may see some paint falling off. Indeed, you can minimize this problem by proper preparation (usually involving grinding and using alumina primer).
As a matter of fact, aluminum boats do not need to be painted except below the waterline and other metals that need to be in contact with aluminum. However, below the waterline, they really need some attention, otherwise, they will corrode. In ships, keeping salt away from aluminum surface is the key to prevent corrosion. Aluminum paint can be very expensive. Even if you paint by yourself, the materials themselves are expensive.
When in "electrical" contact with most other metals (e.g., through a conductive liquid such as brine), aluminum will undergo bimetallic corrosion. Therefore, special attention should be paid when choosing antifouling coatings, because many coatings are copper-based and usually lead to corrosion of aluminum shell.
Repair
Although unlikely, there may be a small leak in the aluminum ship, which sometimes needs to be repaired. These repairs are mainly related to corrosion or collision. When corrosion occurs, it is usually visible and limited to a small area. If the damage is small, you can usually repair it with epoxy resin or welding. For major repairs, you should take a boat to the shipyard to repair the aluminum boat. Repairing large areas can be as simple as cutting corroded parts with a saw and welding them in a new plate. It is always necessary to pay attention to using correct aluminum alloy and welding wire. As long as this is done by qualified professionals, this should not be a problem.
Through hull fittings
Another advantage of aluminum ships is that the pipes running through the hull can be simply welded to the hull. Welding pipes eliminate most of the risks of leakage through hull holes, which is usually the cause of concern for GRP owners. In addition, when these pipes are above the waterline, they can be repaired in water on board. Although this seems to be a trivial matter, it does add extra safety and convenience to the ship.
Cost
The price of a ship depends on many factors, so the difference of hull materials will eventually be blurred by other costs. However, it can be said that aluminum ships are usually more expensive than steel and fiberglass ships. However, you pay for what you get. In this case, it means a stronger, lighter and safer ship. If the low maintenance of aluminum ship is considered, the total cost of purchase and maintenance can be compared with or even lower than other hull materials in the long run.
Because aluminum sailboats are less common than GRP, they are also more difficult to sell. However, they usually keep the resale price high.
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