The Hornet journey for most of us, up to this point at least, has been an eventful one. Even though it has barely been 2 weeks since finals have ended, we as a team have faced many trials and setbacks. All the way back in early September, starting off as fresh-faced, newly accepted Hornet freshmen, we were eager to dive in and begin. But the difficulty of the expectations we felt we had to live up to, as well as the challenges accompanying building an Autonomous Underwater Vehicle (AUV) begin to set in. Having been split into various teams (mechanical, electrical and software), we were quickly split further into our specific subteams (for mechanical, this was Frame, Hull and Actuation) within our teams. Thus began the slow, arduous journey up to this point, in the present day.

From the mechanical side of the house, things seemed fairly simple at the start. Having faced procurement and time constraints the preceding year, the seniors bequeathed upon us their main hull from when they were Hornet freshmen. This meant that we had one big obstacle moved out of our way, and we thought things were going to be smooth sailing from there on. Our blissful naivete was short-lived. As finals drew closer and with only a semblance of the main frame, we were hard-pressed for time, and with finals looming, this meant that more and more time was taken out of the already dwindling pool of time we spent on bumblebee. As finals began and concluded at the usual blistering pace, the various subteams peeled away from our books and began what would be the longest, toughest 2 weeks in our Hornet journey yet. With a growing to-do list, we scrambled to start leak testing and rostering down pool test dates. However, things did not go according to plan (something which we would come to realise in the coming days). Plagued by leak after inexplicable leak, we were frustrated by the seemingly endless propensity for the ingress of water into the main hull. Thus, began a tiring 2 weeks of literal daily leak-testing followed by up-to-midnight sessions in the lab to rectify the identified problems of the day.

Fig 1: Midweek and fatigue setting in as we went for yet another in a seemingly endless string of pool tests.

There were a few problems identified, some of which plague us even to this day. Primarily, was the leakiness of the cable glands. Due to the irregular shape of the battery wires, despite the rubber sleeved-fitted cable with the cable gland clamping down on it, water still managed to enter the main hull. This caused us particular heartache as the cable gland and wire would seemingly hold up in our initial dunk-for-10-seconds-and-resurface-to-check test. Yet, it was only under moderate testing (<10 mins) that the water began to enter the main hull. This has, on many occasions, lifted our spirits and then crashed it, all in the span of 10 minutes.

Additionally, we faced the issue of not wanting too permanent a solution, and yet having our more modular solutions fail us, particularly at the leak test. We began with simple things – tightening the cable glands just that little bit more, attempting to fit another rubber sleeve to help the wires better fill the hole in the cable gland – but they all succumbed to the water in the end. Not to be lazy nor outdone, we persisted. However, we struggled with deciding on whether or not to implement more permanent solutions for our leaky hull, namely hot glue, or even epoxy. A good middle ground which we settled on for a while was blutack, but that began to fail us when we realized that, due to the movement of the wire, the bluetack would deform, allowing water to enter. We thus finally settled on hot glue and blutack, finally solving our issue.

Lastly, we faced the issue of experimentation. Call it conservatism, but we as a batch were very averse to buying and trying untested things. Perhaps it was our meekness and our small appetite for risk; Perhaps it was the environment which we were developed. This resulted in particular inertia in deciding to abandon current ideas and to move on to come up with newer, (hopefully) better ones. This was a particularly tacky issue, as no amount of money nor time could solve this for us. Yet, as our hand was forced by difficult-to-handle battery connectors and possibly unsalvageable cable glands, we slowly, painfully began to learn this lesson, as time and time again our “tried and true” methods failed us, forcing us further and further out into uncharted waters.


Fig 2: Go Team Hornet!!!!

Finally, after much back and forth, we finally did it. With bated breath, after 3 cycles of submersion and resurfacing and a prolonged submersion of 1 hour, we resurfaced the AUV. Initial underwater testing gave us hope, but upon opening the end cap, we were greeted with the sweet dryness we so craved. After 8 whole days of non-stop work, that was indeed a sight for sore eyes. Better late than never. Hastily mounting the electronics, we managed to get it moving, if only a little.

This is Hornet team thus far. Very much like the AUV we are working on, we are a hodge-podge of different parts, a motley crew from all over. Yet, as pressure builds and water threatens to seep in, we just might have needed this push, the impetus to draw closer to each other, to work that little bit harder for ourselves and for each other, to not let all the late nights and flooded hulls go to waste. As we aim to calibrate the balance and achieve slight positive buoyancy, the only way is up.