## 3 Experimental Methods
### Gc Measurements
#### 4.2.3 Archimedes' Measurement  
The relative densities of the hull plate specimens were measured in accordance with ASTM D792-13 [20] using a water immersion hydrometer with a precision of 0.01 g/cm\({}^{3}\) (Figure 8). For precise verification, the densities of the CSM cloth and cured polyester resin were also measured (Table 6); the average values were 2.56 and 1.22 g/cm\({}^{3}\), respectively, which are similar to the values suggested in the classification rules. The Gc of each hull plate specimen was calculated by using the measured density values (Tables 6 and 7) in Equation (2), and the results are listed in Table 8. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Length (mm)** & **Width (mm)** & **Thickness (mm)** & **Weight (g)** \\ \hline \#1 & 25.81 & 20.15 & 9.00 & 8.43 \\ \#2 & 29.18 & 20.01 & 9.07 & 9.56 \\ \#3 & 28.11 & 20.03 & 9.13 & 9.37 \\ \#4 & 27.15 & 19.90 & 9.22 & 8.59 \\ Mean & & & 9.11 & 8.99 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Dimensions of specimens taken from design hull plate with Gc of 64 wt.%. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Glass Fiber Content (Gc) (wt.%)**} \\ \cline{2-3}  & **Design Gc: 40 wt.\%** & **Design Gc: 64 wt.\%** \\ \hline \#1 & 41.30 & 66.67 \\ \#2 & 39.53 & 65.79 \\ \#3 & 39.83 & 65.00 \\ \#4 & 42.01 & 68.10 \\ Mean & 40.67 & 66.39 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Gc calculation result for specimens based on simple direct measurements. Figure 7: Weight measurement of specimens using an electronic scale. For the specimens with design Gc of 40 and 64 wt.%, the measurement results showed differences of \(-0.07\) and \(+2.55\) wt.%, respectively, relative to the design Gc, and differences of \(-0.74\) and \(-0.17\) wt.%, respectively, relative to the average value of the Gc determined using the simple direct measurement. Overall, the results tend to be similar to those of the simple direct measurement; the slight difference is the result of volumetric error for the specimen. Therefore, the results measured using a hydrometer were more accurate. The volume measurement using the hydrometer indicates that there is no apparent defect, but it can be imagined that a higher vacuum was applied with a larger amount of E-glass fibers during the fabrication of the higher Gc laminate and that the thickness was slightly reduced. Overall, the direct measurement method indicates that the laminate structures were generally \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Density (g/cm\({}^{3}\))**} \\ \cline{2-3}  & **E-Glass Fiber** & **Polyester Resin (Cured)** \\ \hline \#1 & 2.53 & 1.22 \\ \#2 & 2.57 & 1.22 \\ \#3 & 2.55 & 1.22 \\ \#4 & 2.60 & 1.22 \\ Mean & 2.56 & 1.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Densities of raw materials derived from hydrometer measurements. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Density (g/cm\({}^{3}\))**} \\ \cline{2-3}  & **Design Gc: 40 wt.\%** & **Design Gc: 64 wt.\%** \\ \hline \#1 & 1.53 & 1.78 \\ \#2 & 1.48 & 1.79 \\ \#3 & 1.52 & 1.78 \\ \#4 & 1.52 & 1.78 \\ Mean & 1.51 & 1.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Measurement of specimen densities using a hydrometer. Figure 8: Measurement of the relative densities of CSM cloth, polyester, and hull plate using hydrometer. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Density (g/cm\({}^{3}\))**} \\ \cline{2-3}  & **Design Gc: 40 wt.\%** & **Design Gc: 64 wt.\%** \\ \hline \#1 & 1.53 & 1.78 \\ \#2 & 1.48 & 1.79 \\ \#3 & 1.52 & 1.78 \\ \#4 & 1.52 & 1.78 \\ Mean & 1.51 & 1.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Calculated Gc values of specimens measured using a hydrometer. fabricated well and without significant quality defects resulting from incorrect scantling dimensions and non-uniformity of the external shape.