Following the original CDR, the whole project design was centered around a few critical concepts that had yet to be proven, so the team and advisor made a plan to develop and test these concepts before beginning the build. A multi-week testing period ensued where the team was able to prove many of the critical concepts for the design. This section outlines the completed testing and results from that period.
6.1.1 Hull Shape/Stability
Between February 27th and March 5th, qualitative tests were run to determine if the proposed hull shape would
be stable. There are multiple kinds of stability to be tested, including orientational stability and turning stability. A model of the hull was 3D-printed, waterproofed with sealer, weighted appropriately with steel bolts, and then filled with a sprayable foam which was carved into the desired shape. To test orientation stability, the model was repeated dropped into a bucket of water at several different orientations (including being balanced upside-down) to ensure that the shape was self-righting, which it is.
Turning stability is more difficult to test – this depends on several factors including the shape and placement of the thruster and rudder – but essentially amounts to the vehicle appropriately “leaning into” turns. To attempt some preliminary testing, the model was pushed around in the water to ensure that it had this “leaning in” effect, which it did. However, since turning stability depends on so many factors, more testing should need to be performed once the final design is fully assembled.
As this project was aimed at developing a proof-of-concept, the team did not end up carrying out planing drag testing. It is difficult to carry out detailed analysis on the hull shape because most planing hull shapes are proprietary and CFD models are not always accurate. Based on discussion with the sponsor, the relative proportions and features are qualitatively right to allow the hull to plane (at least well enough for a prototype). It may be possible for a future team to do further research and/or drag testing in order to refine the hull shape.
Figure 37. 3D-Printed Hull Figure 38. Bottom of 3D-Printed Hull
6.1.2 GPS Testing
The SAVER team performed some preliminary GPS testing on January 23rd, 2020, but the early GPS testing
was qualitative rather than quantitative. The SAVER team took the GPS outside and ran the system to see how accurate it was. After a short amount of testing by walking the transmitter in a circle around the receiver, the SAVER team determined that the direction calculated by the GPS looked promising for the SAVER device. Additionally, the SAVER team took the transmitter and walked towards and away from the receiver at ranges from approximately 10- 100 meters and observed the distance measurement of the GPS system. The GPS system appeared to be accurate to within 5-10 meters or so, which is adequate for the SAVER device prototype.
On February 27th, more detailed tests were run to determine the exact accuracy of the GPS system. The GPS
system was taken to the Cal Poly football field, and several datapoints were taken for angle and distance at each 10- yard line on each side of the field over three trials. As is seen in the following Figures 40 and 42, both the distance and angle measurements are sufficiently accurate for the purposes of SAVER. With 95% confidence, distance is estimated to be accurate to within 2 meters, and angle to within 3.3 degrees.
It should be noted, however, that these results are for stationary transmitter and receiver over land, and this accuracy may not hold for a moving transmitter and/or receiver over water (water tends to negatively affect radio signals). In the future, further testing should need to be carried out for the latter case to determine the true accuracy that can be expected from the device when in-use.
Figure 40. Distance Data from GPS Testing Figure 41. Distance Error from GPS Testing
6.1.3 Waterproofing Testing
On March 5th, a test was run to determine if the proposed method of waterproofing electronics would be
viable. A length of 2 in diameter ABS pipe was attached to one permanent end cap and one threaded end cap using pipe cement. Two holes were drilled in the side, and two different sizes and configurations of wires were run through. The holes were sealed using Loctite PL-Marine, and the threads were coated with a nondrying thread sealant. A paper towel was packed into the enclosure before it was closed and fully submerged in water for one hour. Afterwards, the enclosure was removed, dried, opened, and the inside was inspected for any signs of moisture. The inside remained completely dry, and so the team decided to move ahead with this method of waterproofing for the final design.
Figure 44. Sealing for Waterproof Enclosure Figure 45. Finished Waterproof Enclosure
Figure 46. Test Setup for Waterproofing Test Figure 47. Waterproofing Test in Progress