After the successful completion of my Mid-Sized Observation Class OpenROV, it's time to move on to other projects. The AUV project is still a ways as we work on some of the sensors required, namely an altimeter and a better Inertial Navigation System, but it is still on my to-do list and I'll probably get to it in about 4-6 months.
In the mean time, I thought I would get a handle on how ArduPilot works and build something that can do meaningful work on the surface of the water. A few people has approached me about building a low cost ASV that can take sonar recordings for later processing in the Reefmaster software.
I really liked @AntimatterCrusader 's hull, comprised of a Sun Dolphin Bali 6. It is cheaper than a fiberglass model boat hull and pretty rugged. Instead of a trolling motor, I'll be using 2x BlueRobotics T-200's with integrated Blue ESC's. I know it won't be as efficient as a vehicle with a rudder, but I needed something portable enough to fit in the back of my truck, so about 6ft was my limit. I'll also be using skid steering on my AUV, so it will be good practice for handling.
I intend to put all the electronics in removable Pelican cases and have three oriented in the boat. One in the back for navigation and power distribution to the thrusters, one in the middle for a large battery (still deciding on the chemistry), and one up forward for the Garmin chartplotter/sonar.
I design and order parts as I go, so updates will be a little on the slow side. First few steps will be getting the thrusters mounted and things situated in the navigation case. The cases I have right now are not final, they were just what I had laying around for the concept. I have quite a bit of room to work with.
This has been on my "to-do" list as well. I'll be following your progress, good luck!
Great project, subscribed also. It is also in my list of Robotic Mapping Tools.
Kevin - Awesome project! Looking forward to following along.
The T 200's should work out well for you. My boat has two 100's and will tow me in an Ocean Kayak just shy of 2 Knots at 40% throttle.
@David - That's pretty impressive. What voltage are you running the T200's at?
I like the look of that 6 foot kayak. With a maximum carrying ability of 150 lbs you should be able to carry a good sized battery bank.
So with no rudder and two thrusters, will you mount the thrusters in a fixed position and turn "tank style" or rotate the thrusters to turn? I've attached a photo that may give you an idea or two.
I've considered using a plastic kayak but will more likely go with a catamaran hull. Gives the platform just a bit more stability and less drag.
I have 2 T-100's not 200's. 3 cell LiPo on the 100's
David R. Boulanger
Thanks for the support and encouragement!
@David - Thanks for the info and sea trials. I'm not building this one for speed, more for torque, so good to know about the thrusters. I've had good experiences with my T-100's in my ROV so far. I'll have to see how the T-200's do with their rated voltage.
@bigkahuna - I did some reviews on a few other small kayaks and large model boat hulls, but they didn't really meet my requirements. For the other small kayaks, the seating area had a wavy seat, this one is flat - much better for mounting equipment. Looking at the large boat hulls, they were very nice hulls but they would have been too expensive for what I was trying to do (>$500).
I have searched for about a year now trying to find a location where I can buy the hull you have pictured, but no dice. I think Teledyne Oceanscience is the only manufacturer for those and they don't offer just the hull.
IF I decide to go bigger , I was looking at the Point 65 Martini Single. It breaks down into two pieces and has a rudder. You can run any combo of thusters on that and put a whole bunch of payload on it. The price kept me away from turning one into a science experiment.
Yes, you are correct, it will be "tank style" skid steering, the disadvantage being I will have to slow thrusters down respectively to turn. My advantage is that I have only two moving parts on the whole vehicle - the propellers. I looked into steering the thrusters themselves as you have illustrated, but I'm not sure how I would do it and keep the system reliable. It would certainly have increased speed, but more things to break.
A catamaran design certainly has it's advantages, which hulls were you looking at? If I went that direction, I was looking at the "kick boats" with pontoon tubes. There are a few plastic models, but they are more expensive. Float Tube Store
That hull is going to have a lot of windage. The thrusters will need to be spaced away from one another a good deal to turn in a good wind. I'm not being critical of your idea, but that is one possible problem I see with skid steering and a hull shape that really doesn't bite into the water very much. Look forward to your progress
David R. Boulanger
Kevin, if you do decide to steer the thrusters, there's a great thread about 3d printed parts to do so on our forums: https://www.bluerobotics.com/forums/topic/azimuth-mount-for-the-t10...
I think you'll have plenty of power and control authority with two T200s. On the SolarSurfer, the T100s were spaced about 1 ft apart and it could do a 360 in about 10 seconds.
@David - Yes, completely valid concern. I was planning on mounting the thrusters about 2/3rds of the way back from the bow and as far apart as possible. What would be your thoughts on the below picture? It won't need to be super maneuverable because it will be making long runs and wide turns anyway.
@Rusty - Yes, I would love a pair of those thruster mounts, and I would totally hack into the hull to make a through-mount, but I don't think @Jason Spall ever made the files available...and I have no 3D printer. I think for now, I'll make up some hard mounts out of HDPE and just keep the thrusters straight. I was also going to have the thrusters removable on hex bolts so I can take them off for transport and quickly re-attach them in the field. I can always to a retro-fit later on if better parts come out.
Looks good. The bottom of the hull is much wider than it looked like in the first picture.
David R. Boulanger