The Biggest Rc Submarine Ever!

This is the largest remote control submarine in the world. A huge custom-made RC vehicle that works just like a real submarine, with working ballast tanks to control buoyancy, and even a functional FPV camera periscope so it can see underwater. In this video you'll see how we built this giant RC submarine, going from small prototype all the way up to the nerve-wracking maiden voyage of the 2.7 meter long vessel. The previous biggest RC submarine was 2.4 meters long, but I wanted to see if we could build something bigger. So I got some materials together and started building. And the first thing we needed to do was start right at the beginning by building a prototype to make sure our submarine would work. But really the very first thing to do was to understand the concept of buoyancy, and how submarines control buoyancy to dive and surface. Now you might think that light things float, whereas heavy things, like these weights, sink. But buoyancy is a bit more complicated than this, as it's all to do with how much water the object displaces. For example, if we use this syringe with a bit of clay on the end to hold a load of air in here, we can put this in the water and you can see that that just about floats. But if we take this out of the water and compress the air, like this, using all of my strength, I can hold that in place with a bit of wood and then put it back in the tank, and we should see it now sinks. The syringe now weighs more than the water it displaces. Now we are going to use this principle using motorized syringes inside acrylic tubes, which will be the hull of our submarine, to make the submarine go up and down. The first problem to solve was to figure out how to get the syringes motorized, so that they could pull water in and out of the submarine to change its buoyancy. First I got a strip of wood and glued two small syringes to it. Next I found a length of threaded rod and fitted a small plate with a threaded insert, so that it could be screwed onto the rod and attached to the syringe plungers. Meaning when the rod turned, the syringes would go in and out. Next I'll add an adapter to the other end, and this was so that I could bolt a small high torque motor to it. This motor turns very slowly, but with a lot of force thanks to its gearbox. With the motor in place, I hope that now we can make the syringes move in and out electronically, when adding a small voltage to the motor. Yeah, it works! So the syringe system was working pretty well, but to have really fine control over the submarine, we'd need to know exactly what the positions of the syringes were at all times, so that they could bring in just the right amount of water. So for this reason, we gave the syringes positioning control, using an electronic component called a potentiometer, which was wired up to a servo control board, to move the syringes just like a giant servo. So when this was all hooked up to RC control, moving a dial would tell the motor to keep turning, until the requested position was sensed by the potentiometer. Right, now we had that bit sorted, all I needed to do to make this a proper proof of concept model, was to chop up a bit of acrylic tube to make the hull of the submarine from, along with some 3D printed removable end caps. And now we had a really simple RC submarine, that was ready for our first experiment in a big tank of water. Would it go up and down? Okay, so that's positively buoyant, so now let's see if we can make it negatively buoyant. Right, come on. Oh yeah, it's sinking! It's sinking! Yeah! That's fantastic! So now let's push out the water, depressurize the hull, and see if it comes back up. And it is coming back up! Yes! At the bottom. Here it comes. That is so cool. I can't get over how well that works. We had proved that we could make a submarine, that could go up and down in a tank of water, so the next step in our submarine project, was to develop this mini submarine a bit further, adding a tail and a motor for steering and forward propulsion. So the fins go, that's good. After a quick tank test to see that the fins were working, and the motor turned, everything was looking good. So next we could head to our local testing lake, to put this mini submarine prototype through its paces, in a much larger body of water. If we could see this thing working well here, we would be confident in starting work on the giant submarine, applying any lessons we learned. Okay, good news is it's not sunk yet, because it's not supposed to be sinking yet. Hey, look at that. That's pretty good, isn't it? I'll pull the barrel up a bit. That's working, that's working. That's really working. It's a submarine. Look at that thing go. The submarine was working as expected on top of the water, but now for the real test, to see if it would dive under the surface, using that syringe buoyancy system. So yeah, we've got the radio antenna in here, so this will sit on top of the water, and that means that the radio will actually be able to speak to the submarine, which is underneath the water. Okay, taking on water, I can see it going under. There it goes, it's disappeared. That's so cool. Okay, I suppose we should try and get it back up again. I'm going to set the trims to ascend mode. Now we should see it come back up, hopefully. There it is, look at that, that is so cool. Perfect, our mini submarine was doing submarine things, and was even able to make really precisely controlled movements just under the surface of the water, with the syringes set to a specific intake of water, meaning that we would have just the right amount of buoyancy to hover at a certain depth. The fins even allowed me to adjust the depth more dynamically through pitching the submarine up and down like an aeroplane, and this is actually how real submarines adjust their depth while travelling forwards a lot of the time. That's full steam ahead, full ahead on the sticks there. We'd learned a lot from this prototype, and were confident to move on to the next phase of the project, where things were going to get a lot bigger. After about a week of research and design, we finally had a design for the giant submarine we were happy with, based on the prototype. However, there was one big design change that was quite different to that small scale model. Now one of the big things that we found with the small submarine was that it took a lot of weight to actually make the thing neutrally buoyant, because there was so much buoyancy in that single acrylic tube. So if we were to scale that design up one for one, and use a much bigger tube, we would also scale up the amount of air inside that tube. So because the whole goal for this project is to just build the biggest submarine possible, we're going to build it with lots of smaller tubes, which are arranged around in a sort of configuration like this. The only tube that's going to be filled with air is going to be the top one, and the rest of them are going to be filled with water. So they're just going to be left open to allow the water to come in, and yeah, effectively we're going to have a mostly wet submarine design, with the only bit of buoyancy being this upper tube here. So that's the real bit of the submarine that's really doing the work. We ran all the 3D printers we had in the Project Air workshop for about a week, printing out parts so that we could get started on assembling the giant submarine. This took around 10 kilograms of filament, so thanks to Polymaker for sending over this ultra smooth filament to use on this build. I had to do that. Right, now for the fun part. I started assembling the hull using two big spacer bulkhead parts, and these were fixed in place with super glue. Now to assemble the keel of the submarine, which was an important part as it would hold the counterweights to get the submarine to balance at a near neutral buoyancy point. This was made to be nice and open so that we could pop in extra weights if it needed a few here and there. This part, like many others, was made in sections, and reinforced with aluminium brackets, epoxied securely in place. A lot of the other parts were printed in one go, the nose and the tail being bolted to the bulkheads at either end of the tubes, which made up the main section of the hull. The final part to print was the submarine's propeller, which was printed completely solid, this time in a bronzy colour because it looked quite nice. This is the final 3D printed part. Yeah, it's not like an absolute perfect propeller. It's just been designed by eye really, but I think it'll do the job. So now that we've got all of the 3D printed parts done, finally, after about a week of printing, we can actually start assembling all of the electronics and get this thing RCA-able for its first voyage. The first job to do on the electronic system was to build some large-scale buoyancy systems. These needed to be larger and more powerful than the prototype as we were going to have more air inside this giant submarine. We could fit much larger syringes to the main submarine tube, so this wouldn't be a problem, but they would have to be configured differently. First, I cut some acrylic spacers on our laser cutter, and these would be used as a sort of chassis to bolt everything on. I bolted on a motor and then added a threaded rod adapter for a short length of threaded rod. Brass standoffs could be used to separate the acrylic spacers, and now we needed to fit the larger syringe to the end. Thankfully, this was easy as all I had to do was pop off the rubber seal from the plunger itself and fit it to a custom-designed 3D printed part. Next, I could add a hollow tube and then attach another 3D printed part, and this one would hold the threaded insert. Now I could screw the plunger onto the threaded rod, and the syringe outer body was fixed in place to the acrylic spacers, and now we could fit electronics like those potentiometers we used before on the prototype. Now we had a really solid modular system that could be fitted inside the main pressurized tube. We just needed to assemble two of these and then it was time to fit them in place. Now it's time to make some 3D printed end caps for the bulkhead, and for this I used some very large o-rings on the 3D printed parts. To keep these in place, I bolted them to the bulkheads with lots of M3 bolts. The rest of the electronics would go on the outside of the pressurized tube, but this meant that they had to survive being submerged in water. This was fine though as most of these RC electronics could be waterproofed with a product called Corrosion X. This stuff is great as you can simply paint it over circuit boards, and it leaves behind a thin film of waterproof coating, protecting all of the highly water sensitive components. Hopefully this would be enough protection even while diving quite deep. The servos were a bit more tricky to waterproof as they had moving parts of course, but I had a solution for this too. First I added an o-ring to the top of the servo with plenty of grease to allow it to still turn, and then tightened on the control arm. Next I covered the body of the servo with epoxy so that the only part not epoxied were the bolts at the bottom. And now for the weird bit. I next filled the servo up completely with olive oil, which is actually completely non-conductive. This is weird but it actually keeps the water out and allows the gears inside the servo to still turn, and this is a technique that I've seen other RC submarine builders use. Once fitted everything seemed to be working really quite nicely. Brushless motors are already waterproof, so all I needed to do was just bolt this component on unmodified, but for a big propeller for a very big submarine, I'd need a very torquey motor with lots of grunt. But thankfully this one spanned the prop no problem. I can feel the like thrust coming off it from the air, never mind from the water, so... Whether it would actually spin in the water was another matter, but I had an idea of how we would test this and also all of the other sensitive systems and get the submarine balanced at the same time before heading to the lake for the submarine's first actual test in the open water. I thought it might be a good idea to make the investment in getting a large pop-up swimming pool, just like real nautical engineers use. Well this could take quite a while, so cut to several hours later when this pool is completely full of water. So now to launch the submarine for the first time, and hope all of our expensive electronics we thought were waterproof wouldn't get destroyed straight away. So we've got the submarine nice and low in the water. This is its un-ballasted state, so I think we've done a pretty good job with the calculations. Now what we need to do is just add a bit of steel in the bottom of the keel that we've designed to be hollow so that we can weigh it down so that we can find its neutral buoyancy point. If we could get the balance just right with the syringes at their outward position, we could decrease the buoyancy of the submarine with the syringes, and it should slip beneath the surface with a high degree of precision. You ready Emma? Yes. Going for our first giant submarine dive test in three, two, one. The water's climbing. It's definitely hovering in the water just like that. Maybe add a bit more weight. Right, well the submarine is well and truly under the water now. Let's see if it can come back up from there. Oh, there we go. It's working. I mean, it's got a very fine range as we thought it would have, but yeah, look at that. It's gone down and it's come back up. Let's get it to go back down again. Okay, diving. We should see both bits just disappear under the water. Ready, three, two, one, ascending. Oh, that's cool. Everything seemed to be going quite well. The buoyancy systems were doing their job and we had the thing balanced. Hey Emma, the other thing, the other thing is that nothing's broken yet. It's been in here for about 15 minutes now, probably. Telemetry lost. Are you joking? Why do you say that? Oh my gosh, something's just broken. What timing! Unfortunately, our waterproofing of the electronics hadn't been good enough as the electronic speed controller had broken after around 15 minutes in the water. Clearly, the corrosion X and a small amount of epoxy at either end of the heat shrink hadn't been enough to protect it fully from the water. This wasn't too much of a problem though, as we had a spare and could quickly solve this problem once and for all by completely encasing this speed controller in epoxy resin to seal it off from the water. There was no way that this one was going to get wet. With that small electronics issue solved, we could finally complete the very last job of the giant submarine build by fitting an FPV camera to the conning tower so that we could see a live view from under the water. One final test in the water tank showed that we had the thing working really well and we were well balanced for diving and ascending. So now we were ready for the most exciting bit so far, the test. It's done. Yeah, I'm quite nervous, but if it just sinks and never is seen again, then, well, at least we will have learned something. But that is part of the challenge of this channel. We've got to risk it to see if it will work in the real world. Let's go, let's get this thing on the water. After packing the giant submarine into the Project Air van in its modular parts, all of our gear was strapped down and ready for a quick journey over to see our friends again at Rudyard Lake, who had kindly offered to host the maiden voyage of this potentially record-breaking RC vehicle. 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It's applicable for PCB assembly and CNC and 3D printing and stuff like that. It's available for three months and expires six months after individual redemption, and it's one-time use, but there are only 200 available for use down below. Check out the link in the description, and yeah, now let's get to the lake. All assembled once again, we could get the submarine prepared for its first taste of the open water, where it would hopefully prove itself to be capable of manoeuvring and diving on top and beneath the surface, essentially doing everything a submarine should do to prove that it is a fully functional submarine. There was one important final job still to do though, before this thing was launched. I'm christening it. The submarine was powered on and all of the systems checked. Now for the nerve-wracking bit, actually putting it in the deep water off the side of the dock. Okay, see the air bubbles, just wait for a sec. Yeah. Okay, and then let go. I'm just waiting to see whether it seems to sink or not. Okay, that looks pretty good. I think we should just go for a run. The balance looks spot on and nothing seemed to be leaking, yet. All right, cast off. Okay, we've still got FPV feed. We still have FPV feed. Okay, let's go for throttle. There we go, we're away. We've got the throttle pushing the thing away and the tether is about to get hooked on, but look at that. That's fantastic. It's going. Let's see if I can bring it around a little bit. Oh, that's so cool. Okay, so I've not got that much authority. Let's give it a bit more throttle. Oh, it's doing it. There goes the world's biggest RC submarine. Surface trials are going well. Let's go. Right, we'll bring it around in a nice big circle. I got the giant submarine turning back to base using the large fins at the rear. Oh, nice. I think that, yeah, we've got throttle. We've got throttle. It's really hard to see because it's under the water. I'm going to intercept. Here we go, back to base. Yes, fantastic. After a quick check, we will all go for our second test, where we would see whether the submarine could actually dive in the open water. This would be different to our pool tests at the workshop as we would be going far deeper than before, which might show up a few issues as the water would be putting more strain on the hull and electronics. Okay, my hand's going in. Just translate it slightly sideways. Feels like it's going a bit tail heavy there. Right, let's use the buoyancy controls. Dive, dive, dive. There goes the water level. Ready, and it's gone. Well, it's going. There we go. The submarine is diving. The submarine was diving faster than I'd expected, so it was time to reverse the buoyancy controls to empty the syringes and come back up. This was critical. If it refused to reappear, something must have gone wrong. Okay, I'm emptying the tanks of water and we should hopefully see it come back again. I see a bubble coming up, that's not good. That's some of our buoyancy and there's a bigger bubble. Oh gosh, oh gosh. Come on, come on, please come back. I've seen no radio signal loss on the controller. Right, it has actually gone and it's not coming back. I'm just going to give it a bit of a tug and it might start coming back. Thankfully, I realised that although the submarine weighed a lot on land, as long as we hadn't had a major leak in the main tube, it should still only be a bit heavier than neutrally buoyant in the water due to its displacement. I really hope there's a submarine at the end of this course. Here it comes, here it comes. Oh, James, James, look at all the bubbles. Oh no. Right, let's get it out quick. Oh no, there's something happening. Right, I've got it. Have we still got control? We've still got control. So something has leaked, I think. And yeah, unfortunately, the submarine did not come back up again. I'm seeing bubbles escaping from here. I think it might be the 3D prints, actually. After a frantic rescue operation, we could assess what had actually happened. But not before I accidentally almost pushed Emma into the water. Ow, whoa. It turned out it was the not completely solid tail pieces that had been printed with a hollow infill. As the submarine dived, the increasing pressure had forced water inside these parts, filling them up, decreasing the total buoyancy of the submarine. This meant that the submarine hadn't had enough range on its buoyancy systems to become positively buoyant again, meaning it stayed at the bottom. So we discovered that the submarine had a limited depth it could dive to, but this wouldn't theoretically stop us from operating at shallower depths. We would repeat the dive test at a limited depth to prove the submarine could operate under the surface. All right, I'm going to turn it around a little bit so it can see kind of like underneath the dock. All right, let's see if we can see those fish. Dive, dive, dive. So there we go again. Okay, I'm going to make the tail come up a bit more. I'm going to trim it because it looks like the tails. Yep, I wonder if we can see those fish. I can't see them around here. Maybe I'll go a bit further. I'll try and scoot underneath the deck with the throttle. Oh, I can really precisely control it with these dials. All right, let's come back up again. All right, come on. Come on. It's very slow. Here we go. And we've breached. All right, let's bring it back in with the motor on the rear. Mission complete. Yeah, it works. That is a proper submarine in my books. So we'd done it. The vehicle was working as intended and now we could really call this thing the world's largest RC submarine. Now we were ready to take it back to the workshop for assessment. Right, we've got everything back to the workshop and I'm very pleased with how this submarine performed on its first mission and yeah, we achieved all mission objectives in the end. There are so many things that we could improve on this design with basically every single part. We did have a bit of a problem with, of course, that tail with the not completely solid fins taking on water and we didn't see any fish so I'll have to probably take this thing out again in the future with some modifications. Let me know in the comments if you want to see this submarine again. I'm not sure if this will be in a main channel video again but make sure to check out Project Air 2 and of course the Project Air website where if you sign up to the newsletter you'll be sure to hear about what we do with this if I take it out again. Right, thanks very much for watching this video. If you got to this point of the video then make sure to check out another video over here and also let me know in the comments what sort of vehicle I should build next. Also make sure to check out the Project Air website. There's loads of cool stuff on there that will help you to build your own projects and with that I will see you on the next project. Bye for now.