Today, I finally had a chance to actually test the drone underwater. 

Because I was still unsure and concerned about a couple factors regarding the drone—including the buoyancy, strength of the electronics tubes, and true driving ability of the drone—I wanted to do the first test in a more controlled environment first. Luckily, in my backyard sits a small lifted up jacuzzi-pool type of thing—shallow enough that the drone wouldn’t sink too deep to implode, deep enough to let it drive completely underwater, and complete with a convenient table-like rim around the outside perfect as an impromptu workspace. 

I first started by making sure to charge each battery pack to full, so the drone wouldn’t brown out in the middle of my testing session. After plugging the batteries in, I only needed to put on the cap, shove the back end of the drone back on, and screw in 4 screws to get it up and running, making for quick and easy use. 

I brought the whole setup with my computer, controller, and tether outside into my backyard and got ready to try the drone for the first time. However, one problem immediately became obvious the moment I put the drone into the water: it floated. 

Even though I had calculated the total buoyancy force of the two tubes to equate to only 4.66 lbs, countering the drone’s total weight of around 7 lbs, and making up for the difference by adding close to 2.5 lbs of buoyancy foam force, something still wasn’t quite adding up. I noticed that it was typically the tip of the drone that tended to rise up, so I decided to remove some of the buoyancy foam from the front of the drone. Even after doing that, however, the drone still floated. 

Left with no other options, I decided the best way to figure it out would just be to strap on some extra weight and try to find a working balance point. Unable to find any dense enough small objects to put inside of the drone, I decided to strap a small iron plate onto the bottom of the drone with paracord. 

By the way, I don’t know if anyone else knows this but it turns out that pools don’t actually just stay clean after years of no use. A ton of dust and debris accumulated on the bottom of the pool and got kicked up the moment I turned the drone on. 

That ended up working a bit better, but the weight ended up falling off and was definitely too heavy anyway. 

I then tried a couple more times with different kinds of weights, including a 3 lb dumbbell, and the most successful run ended up looking like this. 

It actually held up pretty well for a bit, but after a couple mor

e tries, it was clear the weight wasn’t a great solution, and I would have to tune the balance of the weight a lot more in order to reach true neutral buoyancy. 

See you in the next update as I try to use 3 lbs of stainless steel beads to fix the buoyancy problems.