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SELF-RIGHTING BOAT DESIGN 47

Figure 3. Examples of Inherently self-righting boats.
Vital quality of this craft is heaving a watertight hull and mainly watertight superstructure.
Strategically located weight and buoyancy distribution is key to achieving inherent self-righting.
Ship’s main machinery system usually located at aft deck. Thus, in case of capsizing; trimming
due to the weight and buoyancy difference must avoid. An extra lift force is required to avoid
negative stability curve when the vessel immersed at the aft deck (Fig. 3).

Benefits of inherent self-righting include [6]:
 No working parts that could go wrong
 Self-righting capability is always available and at any angle of heel, so can prevent full
capsize of the vessel.
 Can, within reason, be applied to any size vessel, although weight limitations on very
small can limit effectiveness.

Disadvantages of the method include [6]:
 Superstructure volume must be adequate to provide the necessary inverted buoyancy,
which often results in the seemingly oversize deckhouse fitted to modern rescue boats.
 All hull and superstructure opening must self-close or remain above the waterline
during full 360 degrees roll.
 Structure of hull and superstructure, including any deck recesses, must be designed to
withstand hydrodynamic forces resulting from capsize.
 Window and doors must be capable of withstanding the same pressures as hull and
superstructure.
 A good effective mechanical ventilation system will be necessary as the vessel will
effectively be operating closed down with all doors and windows shut.

3.2 Inflatable Bag
Smaller crafts are generally more viable utilizing inflatable bag method. Rigid inflatable rescue
boats (RIBs) are usually featured this method (Fig. 3). It takes the form of an inflatable bag,
carried on and securely attached to, a substantial gantry frame located across the stern,
straddling the engines or propulsion units. The bags are commonly made from neoprene or

Sayı 6, 2016 GiDB|DERGi