HYDRODYNAMIC PERFORMANCE OF NEIL PRYDE RS: X AND MISTRAL SAILBOARD

After Olympic Games in 2004, the once used board, MISTRAL (M), in Olympic Game has been substituted with NEIL PRYDE RS：X (NP). To meet the need of the national sailing team, the research group carried out the experiments on the hydrodynamic performance of the NP and M early or later. The resistances, transverse forces and wrest moments were measured by using the balance of the trisection force, the angle of the heel and pitch was measured by using the angle sensor. The sailboard could rise and sink freely, the pitch was free, the static angle could be adjusted by utilizing the weight and the balance was at the mast. The results showed that the resistance of NP sailboard was bigger as soon as the pitch angle was bigger and this was the same as that of M sailboard, the heel did not have any influence on the resistance of NP sailboard, the resistance became small continuously when the angle of the centerboard decreased and the resistance increased as the sailboard was heavier

The application of canting keel concept in racing windsurfing fins: does it lead to superior performance?

Windsurfing is a young, dynamically evolving sport. As the numbers of windsurfers increase around the world, equipment producers race against each other, using the latest materials and technologies in the never ending pursuit of better performance. The aim of this research is to investigate the latest development idea – the canting fin. The project is based on Formula Windsurfing, a racing discipline, where fins reach 70cm of length and have crucial influence on a competitor’s final result. Primary data was collected in two stages, in both qualitative and quantitative forms. The former involved 4 male, international-level windsurfing competitors who tested two provided sample fins – one of a classic design and the other, with the same geometry and material properties but altered into the canting concept. Subjects’ observations were recorded using a semi-structured questionnaire. The second stage of data gathering was based on GPS measurements of fins’ performance. Once again the two described sample foils were used to identify the advantages and disadvantages of the novel design. At this point, over 5000 of speed and course measurements were taken providing a significant data set. The presented results show numerous differences between the tested fins. Overall, combining all of the measured characteristics, the canting fin proved to be superior by 44% in a simulated competition situation. In a competitive situation, research participants would have chosen the new fin in 87% of the tested situations over the classic design. The project generated an interesting set of results without having to base on multiple assumptions. It was 100% practise-based and was designed as an alternative to laboratory-based modelling. Factors influencing data precision and the measurement error were discussed and several areas for further research were outlined

The Manufacture of Marine Propellers in Moulded Anisotropic Polymer Composites

This thesis examines the feasibility of manufacturing small marine propellers from continuous fibre reinforced polymer composite materials. An appraisal of some current applications of composite materials in the marine industry is given, together with the moves shown towards the use of composites in the area of propeller design. It has been shown that manufacturing propellers in composite materials is theoretically more cost effective than traditional materials. The manufacturing route investigated is Resin Transfer Moulding, where some detailed investigations have highlighted some of the critical processing parameters necessary for successful production of laminates suitable for propellers and other high performance marine structures. A thorough testing programme of 4 novel designs of composite propeller is reported. Trials at sea on university run vessels has enabled many hours use to be logged, which has shown the fitness for purpose of propellers made from glass reinforced, epoxy composite. Experimental tank testing has helped to shape the remainder of the research by identifying the possibility of using hydroelastic tailoring to improve the efficiency of the propeller when a variety of operating conditions are required from the propulsion system. Further experience is required with respect to the the tooling construction and the life assessment of the propeller. To facilitate appropriate modelling of the propeller, spreadsheet based load prediction models have been used. Finite element analysis (FEA) was used to model the elastic characteristics of one particular design of novel composite propeller. This indicated that traditional geometries may be too stiff to allow significant performance advantages from the anisotropy of the material. However the potential does exist for modified propeller geometries made from composite to give some performance benefit. For specific applications, small marine propellers made from continuous glass fibre reinforced epoxy composite are likely to yield cost savings over traditional propeller materials

The development of a reversible and finitely variable camber windsurf fin

An investigation was undertaken to identify and develop a practical method for improving the lift to drag ratio (LID) of the contemporary windsurf fin. It was established that the contemporary windsurf fin is at an advanced stage of evolution and that a fundamental reworking of the design is required to attain significant L/D gains. In particular the symmetrically foiled cross-section (required for equal performance on each sailing tack) limits the performance potential of the device. The benefits of using camber in the design of lifting sections for high lift and low drag are well known. Traditional variable camber lifting surfaces utilise leading and trailing edge flap technologies to vary the geometry (camber) of the cross-section. However, this method for generating variable camber is not considered to be suitable or practical for the windsurf fin, primarily due to the increases in drag associated with conventional flaps. An alternative approach for developing a variable camber windsurf fin is therefore considered. It is proposed to use hydroelastic tailoring techniques to realise a reversible and finitely variable camber cross section for the fins used in the sport of windsurfing. The camber in the cross-section is invoked by the pressure differential acting on the two surfaces of the fin when it is at an incidence angle to the freestream. The magnitude of the camber is adaptive and responds passively by design, material usage and sailor input. As part of the preliminary investigation a computer based analysis tool was developed to perform the two dimensional investigation into the coupling effect between the fluid flow and the hydroelastically tailored cross section. Based on the outcome of this work a prototype windsurf fin employing a hydroelastic cross section was fabricated and tested. Results from this preliminary investigation establish the potential for using a hydroelastically tailored cross-section to significantly increase the L/D performance of a windsurf fin of nominal surface area (when compared with contemporary designs)

Landing performance and lower extremity injuries in competitive surfing

Competitive surfing involves highXrisk manoeuvres that may impose injury risk, especially in the lower extremity. Although the dynamic environment of surfing is a major factor of unpredictable determinants for injury risk, there may be athlete qualities with importance for prevention. Previous studies suggest that dynamic loading and landing tasks represent major risk factors, and should therefore be included in athlete assessments and risk analysis. The purpose of this thesis was to investigate landing tasks that may be related to surfing performance and injury risk. It involved studying manoeuvres and landing tasks to establish its relevance for surfing athletes, develop multifactorial assessment protocols, as well as observe mechanisms and factors influencing lower extremity injury risk in high performance surfing. Study 1 examined manoeuvres of the competitive season of the World Championship Tour, reporting on frequency and scores. Although reXentries were the most common manoeuvres, waves including aerial manoeuvres and tube rides scored higher on average; 7.40 ± 1.53 and ± 6.82 ± 2.13 respectively, compared to 5.03 ± 2.21 for turning manoeuvre waves. Therefore, aerial manoeuvres and barrel rides are necessary for high performance surfing Study 2 evaluated impact forces, accelerations and dorsiflexion range of motion in five different landing tasks. A drop and stick landing, two surf stance landings and two gymnastic type landings were performed by eleven competitive athletes. The peak acceleration was about 50% higher whilst landing on a board in a miniXtrampoline gymnastic exercise compared to a surf stance landing from a 50 cm box (p≤0.05). Furthermore, the dorsiflexion ranges of motion in the gymnastic type landings were lower than the other landing types (p≤0.05). The greater load observed in the more complex tasks indicate that the risk involved may be higher in these, compared to general landing tasks. Study 3 provided information of the circumstances of surfing injuries, by video analysis (N=13). Factors that were found to distinguish between injury situations and non-injury situations were deep knee flexion at water contact, upper body lateral displacement, knee valgus, perturbations in the landing and direction of board relative riding direction. For safety, athletes should practice landing competency and increase adaptability to sudden environmental changes. Study 4 describes the development of a model based on the five measures ankle dorsiflexion range of motion, lower body strength, and time to stabilisation, peak force and a frontal plane video analysis during a drop and stick landing. The model was based on normative data from 71 surfing athletes and developed into a score based on exponential functions for four groups of athletes (male, female, junior and senior). It was concluded easy to implement, and may be useful in the assessment of landing competency of surfing athletes. Study 5 was a prospective study of competitive surfing athletes, observing injuries during six months. Furthermore, the athletes (N=48) were tested on baseline assessments to reveal whether any of the variables could be useful as indicator of injury risk from closed kinetic chain movements. There were 22 injuries reported during the period, whereof 8 were categorised closed kinetic chain injuries. Two baseline measures were found to be potential risk factors; the model of landing qualities and bilateral squat asymmetry (p≤0.05). Athletes with excessively poor assessment results on landings and bilateral squat may be alerted of potential injury risk. Landing competency and other bilateral movements can be tested and trained in the land-based preparation of surfing athletes, and seem to be relevant for competitive surfing athletes. If excessively poor scores on these assessments expose the athlete to injury risk, then athletes should aim for satisfactory scores before successively training high-risk manoeuvres in the surfing context

Commercial application of aluminum honeycomb and foam in load bearing tubular structures

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references.Small dimension engineering tubular structures subjected to a complex load system are designed like hollow circular shells. For minimum weight design, the ratio between the shell radius and the thickness has to be as large as possible, but its maximum value is limited by the onset of local buckling. Tubular natural structures subjected to a complex load system have often an outer shell of solid material supported by a low density, compliant core, which makes them more resistant to local buckling. Biomimicking of natural constructions offer the potential to improve the design of small diameter tubular engineering structures. Here, the fabrication technology of biomimicked engineering tubular structures integrating aluminum foam or honeycomb as core material is discussed. A viability analysis is presented including technical performance, cost, utility, and risk assessments. Aluminum compliant core shells have potential for substituting CFRP and aluminum tubular structures in aerospace and high-level sport applications. The case of sailboat masts was considered in detail. Results of our analysis proved that use of honeycomb as core material can lead to a significant reduction of the mast weight. Business opportunities based on this application are discussed.by Stefano Bartolucci.M.Eng

NASA Tech Briefs, December 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

State of the River Report for the Lower St. Johns River Basin, Florida: Water Quality, Fisheries, Aquatic Life, and Contaminants 2014

https://digitalcommons.unf.edu/sotr/1006/thumbnail.jp

Remote monitoring and control of autonomous underwater vehicles

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1997.Includes bibliographical references (leaves 111-113).by John H.I. Kim.M.S