I’m trying to figure out how to prevent my Blueboat from sinking if something catastrophic happened and say the hulls filled with water.
I’ve been using a rope to tether the Blueboat so I could pull it out if it was sinking, but the rope makes driving it around annoying so I wanted to attach a buoy or something to the boat.
Dumb question but would the Blueboat sink if it filled with water, assuming there’s no payload? If not, how much payload would cause it to sink if it filled with water?
If it could sink without a payload, how much weight would my buoy need to support to prevent it from sinking all the way down?
Do you have any recommendations for methods to prevent it from sinking? I was thinking of tying a boat fender between the frames.
The BlueBoat hulls are rather robust - it’s not particularly easy to break them, so I’m curious why this is a particular concern. For example, are you expecting to operate in conditions where large sharp things can hit your boat at high speed (like a ship, or its propellers)?
The hulls are LDPE, which is less dense than water (especially salt water), but I’m unsure how that buoyancy stacks up against the weight of the metal parts of the frame, and the electronics and batteries.
The mass of the payload would be unimportant in isolation (when submerged) - the average density (and corresponding buoyancy) is what matters.
From the technical details, the total mass of the boat (without batteries or payload) is 14.5kg, so that would be the maximum, though the payload capacity is another 15kg so if you assume that’s compressed into a single point of mass then the absolute maximum would be ~30kg. As mentioned though, the hulls would be helping slightly (rather than sinking), and likely make up the majority of that boat mass, so it should be substantially less than that. Everything else also has at least some volume, which further reduces the effective weight of the submerged setup.
Risk is a combination of severity and likelihood, and when reducing the severity is challenging as part of a risk mitigation plan, it’s often acceptable to reduce the likelihood of the problem occurring instead.
I would strongly recommend setting up a pre-mission checklist that involves checking for other vessels in the area before operating a BlueBoat, and making sure all the parts are sealed before you launch the boat. Beyond that there is failsafe behaviour you can configure if the boat goes out of communication range, for example, but you can also take steps to ensure you have good communication coverage and redundant methods (e.g. wifi radio + a cellular modem) if that is a concern.
Adding passive buoyancy elements (or other emergency floatation devices, like a compressed-air inflatable for example) could help slightly reduce the severity of a major water leak, but be aware that they’ll also reduce your boat performance all the time while it’s working well (at least by weighing it down, and possibly also by increasing drag depending on how they’re installed). There are trade-offs to every approach, and depending on your operating requirements many of them may not be practical given the level of risk involved.
The only way I’ve managed to (nearly) sink a BlueBoat was by leaving the cross-tubes completely off their barbs, after running a cable through them and between the hulls. It took about 30minutes before I noticed, as I was operating in flat-calm water, but the boat was retrieved with a quick swim.
I’m too am curious what sort of catastrophic things you’re worried about? I routinely throw my test BlueBoats off of cliffs, beach them on rocks, and ram them into things - all in an effort to see what breaks. Other than the occasional prop hitting a rock, I’ve not yet been able to pierce the hulls themselves - the roto-molding process they are made with is identical to kayaks, which are nigh indestructible!
Tying a couple life-jackets to the top is one option, and the bigger risk to normal operations is flipping… which is also preventable!