## 2 Methodology
### Design and Construction of Small-Scale OCT  
Designing a small-scale propeller in SolidWorks (2024) involves a systematic process:  
* Importing the coordinates of 25 distinct hydrofoils into SolidWorks, which define their shapes;
* Defining the blade planes;
* Sketching each blade within its respective plane;
* Repeating the sketching process for all 25 hydrofoils;
* Applying the chord length, twist, and sweep angles to each hydrofoil;
* Creating the 3D model;
* Adding the hub and shaft. In our propeller design, we twisted each blade along its length to enhance performance by evenly distributing lift and increasing efficiency. This customized twist and sweep for each blade section created the desired propeller shape. A 3D model of the propeller was built as seen in Figure 1a, after sketching and adjusting the blade sections for twist and sweep, as seen comprehensively in Figure 1b. Various tools were employed to loft or sweep the sketched sections, ensuring a seamless transition and continuous blade shape. Additionally, the central hub and shaft were separately sketched and integrated with the blades to form the final propeller, following scale-down calculations and dimensions. To manufacture the small-scale propeller, we utilized a 3D printer at the University of New Orleans and opted for carbon fiber filament due to its specific advantages. Carbon fiber offers exceptional stiffness, strength, and fatigue resistance, aligning well with the requirements of our experiment. Its outstanding strength-to-weight ratio significantly reduces the overall weight of the propulsion system, thereby enhancing performance  
Figure 1: (**a**) Design of three-bladed rotor. (**b**) Hydrofoil sketch using Solidworks. and efficiency. Compared to traditional materials like metal, carbon fiber is much lighter while maintaining impressive structural integrity. This enables the construction of thin, lightweight blades capable of withstanding the hydrodynamic forces experienced during the experiment. The high tensile strength of carbon fiber contributes to the durability of the propeller, reducing wear and tear and resulting in cost savings and improved reliability. Additionally, carbon fiber's resistance to corrosion and superior fatigue resistance ensure a longer operational life, crucial for withstanding the harsh conditions of the towing tank environment and dynamic loads experienced during the experiment. Overall, carbon fiber filament offers a combination of light weight, strength, and durability that makes it an ideal choice for propeller construction, leading to improved performance and longevity. The hydrokinetic turbine nacelle was designed following the ITTC guidelines and created using SolidWorks, a piece of CAD software known for precise modeling. To ensure the safety of the electronic components and sensors during testing, the nacelle was divided into two parts. This separation protected delicate parts from potential damage or interference during testing. The first segment of the model or \"insert\" serves as a protective enclosure for the instruments. It consists of two parts: a base piece and a cap. The base piece provides a stable platform for the motor and sensors, ensuring their secure positioning during testing. Figure 2a provides a visual representation of the base piece of the insert and its function. The cap is the upper piece of the insert shown in Figure 2b. The main purpose of the cap of the insert is to shield and safeguard the instruments housed within from external factors that could impact their performance. This includes protecting the components from potential leaks from the submerged nacelle in the towing tank, which could compromise the accuracy and safety of the experimental setup. The insert, consisting of a base piece and cap, provides a robust and protective environment for the PMDC motor and sensors during hydrokinetic turbine testing. This setup ensures reliability and security, enhancing the precision and accuracy of collected data.