Aboard ships, the design of propulsion systems is developed commonly matching propeller with engine. However, some aspects not considered in design appear when the system is in service, these are vibration and bearing overloading because misalignment. The same occurs on ship structures where the initial design considers only static loads and no periodic forces because of vibrations. If these problems were considered in the design stage, would avoid difficulties in ship operations. But the detection of those problems often requires complex calculations that avoid their development. This paper establishes methodologies of design for structures and performance analysis on machinery subjected to vibrations due excessive excitation forces and resonance situations. The steps for carry out free and forced vibration analysis are shown for structural components and propulsion systems for torsional and lateral vibrations. Also, the influence of waves in ship structural resonance is commented and the way to carry out related analysis modelling whole structure and later local structure. And a rational alignment is described to solve trouble in lateral vibration on propulsion systems. The evaluation criteria for different components on board affected by this problem are indicated for machineries and structures. Finally, this document show some methods to evaluate the human reaction exposed to whole body vibration where proficiency is required for operational and maintenance tasks based on displacement, velocities and accelerations values due to vibrations.

Request the full document to: info@romv-sdci.ec

The weight estimation in small boat design and construction has strong relationship with the boat displacement and the final position of its centre of gravity. In composite materials boats where the final manufacturing specification are closely linked to the worker`s skill and expertise, there must exist a weight control process in all design stages, during construction and until the sea trial test. The implementation of this process imply to all shipyard departments involved in the boat production once there are contractual agreements, and when initially it is established a goal weight based on production capacity and design requirements, later on generate weight control strategies based on production metrics as percentages by weight of resin and fiber, laminating methods and piece permutation, and finally carry out strategies for weight correction based on boat performance as speed, stability, dynamic behavior, etc. Additionally, there are uncertainties attributed to other materials and equipment specifications where the weight control needs to be managed as limited design space with a rational acquisition process targeting to the best boat performance. The construction of three fast riverine patrol boats (LPR) is the case study presented here and this work describe the different activities which can be carry out for the weight control implementation.

Request the full document to: info@romv-sdci.ec

---

Request the full document to: info@romv-sdci.ec

Given the continuous development of high performance riverine patrol vessels in COTECMAR for fulfilling the Colombian Navy needs, several research projects supporting the design process in order to improve the performance of the ships have been implemented. For the Light Riverine Patrol Vessel – PAFL, the major requirement was a draught of 0.75 m, clearly less than the specified one for the previous series of patrol vessels with 1.3 m. Consequently, an exploration for the correct hull form and scantlings combination gave an initial solution to satisfy the requirements. Since this initial design was carried out following classification society rules with higher safety factors, the structural optimization showed in this work allowed to reduce the steel weight between 4.51 and 18.24 %. Dual level optimization algorithms with weight and cost as objective functions were employed. A full ship model for loads definition of and boundary conditions, and a single module model of the ship, both of them developed in the MAESTRO software, were used in the optimization process. Strength, operational and shipyard's construction standards constraints were considered in the optimization problem.

 Request the full document to: info@romv-sdci.ec

 

---

Request the full document to: info@romv-sdci.ec

 

Since the last decade the continuous use of cruising catamarans around the Galapagos Islands has grown considerably in harmony with the boatbuilding in Ecuador, which led to the development of a prototype catamaran fulfillment at all the requirements of cruise inside the islands. A cost-effective analysis of the existing local catamarans was carried out resulting in that such prototype could be improved regarding the hull forms, seaworthiness, speed, construction and cost. Although the outfitting capabilities and the state of the art of cruising catamarans in Ecuador were not the best, nowadays the catamaran´s operational experience itself allowed introduce a design with performance and productivity-oriented concepts benefiting the owner with shorter construction time, lower construction costs and lower operational costs. A data collection of the fleet itself, past boatbuilding experience, survey of existing designs, rational analysis of the boat breakdown structure and a little review of the catamaran´s state of the art led to the development of a cost-effectiveness model (OMOE-OMOC) and solved it giving a improved solution as the basis for the GRP CATAMARAN OCEAN SPRAY design and construction. The results were the employ of just 84% of man-hours used in previous projects equivalent to a final cost saving above 11% including materials and equipments, 1.5knots higher even when the main dimensions were increased by 5% compared to others catamarans and the endurance/autonomy was increased by 65% giving to this boat an added cruising autonomy of 15 days as well the common 7 days around the islands. Finally, this paper include comparisons of representative catamarans including the OCEAN SPRAY as a result of the feasibility models and the conclusions for improved future catamarans construction for the Galapagos Islands.

Request the full document to: info@romv-sdci.ec

 

---

Request the full document to: info@romv-sdci.ec