[MOC] Lego ~Technic Camera boat | filming from the surface

[896gerard]

Once in a while, every Technic builder wants to build a Lego boat. I was no exception, but there's a lots of boats being built: how to make an original boat then? I decided to not design a good-looking boat, but to make it a tool for filming. This choice asks for a boat that can be quickly placed into its filming position, which means it should be fast and agile. It should also have enough remote control range to film on big water areas. The 1980's Power Functions remote is thus completely out of the question: responds very slow and outside, there's 2 metres of range. We all must thank S-brick for existing. S-brick (or alternatives) makes this boat possible: without sufficient range, there cannot be a camera boat. 

Many boats have a keel and a rotating propeller at the back. A submerged plane behind the propeller acts as a rudder. Sadly, a rudder becomes less efffective at lower boat speeds and the boat reacts slowly to it: turning the rudder does not mean turning the boat, it first needs speed (and thus space!) to turn. In Dutch ditches (where I wanted to test the boat), there is not a lot of space available for maneuvering. Having a a slow-responding boat with a rudder there means the boat being into the reed all the time. I therefore eliminated the rudder and mounted the propeller on a hinge. Any hinging of the propeller system at any propeller speed the boat causes immediate turning, which is a nice direct response on the steering input. 

Good theory, but when a single rotating propeller is mounted on the rear, the boat will rotate along its Z-axis. I'm not sure why this happens. It may happen due to the gyroscopic effect of the propeller or due to the Lego propellers not being made for water propulsion, but anyway I had to deal with it. A second propeller placed next to the first propeller that rotates in the opposite direction seems to to the trick. However, when you mount this system on a single hinge, the (larger) system swings out quite far and easiliy hits reed in the typical tight Dutch waters I tested it in. Also, in windy waters, having a single propeller at the rear means the steering is countersteering all the time just to sail straight on! 

To deal with the problem, I mounted  1 propeller at the front of the boat and one steered propeller at the rear. This means the boat always tracks straight (even when the wind comes in from any side) and that the propellers can be mounted close to the boat, reducing its draft. The boat is made from 2 boat hulls to create a stable camera platform. This concept worked, it gave a lot of control. I decided to use a race buggy motor as it provides a lot of RPM at low torque, excactly what a boat needs. As no additional parts (for looking nice etc) were added, the boat was light, controllable, fast and really fun to use. 

The steering is a quite unusual setup (for me). It contains a rack with a 24t gear, a PF Servo motor and a ball link system. This setup had the power and speed that was needed for the steering to be quick.

The video

The GoPro is mounted upside down under the boat. The high speed axle to the front propeller is also visible. 

For water level footage, the GoPro is mounted starboard-side of the boat. As the boat only weighs 831 grams, this effects the balance a bit.. 

Sometimes, I used a rearward-facing camera, mounted in a Lego frame and adjustable by a large linear actuator. 

The same camera, facing to the front. Due to the size of the boat, there are weight restrictions. The boat wouldn't sink with a mounted DSLR camera, but it would not be stable enough when the wind increases. 

The Sbrick and PF battery box are mounted on the left side to keep a low center of gravity and to restore the balance (the servo is not in the middle). 

The boat packs some power, which is visible from the wake in the water. Thanks to S-brick the boat never went out of range so it was also a really nice toy.

It might have been faster with BuWizz though, but that question might be answered later. I think this boat really makes a case for the race buggy motor. It has good RPM and power for its size and in the water it never runs out of torque (a problem that can occur on land.. ). Hopefully someday somehow it will be made compatible to Powered Up, otherwise this hero will disappear in the shady realms of the past.  

 

 

 

 

 

Edited August 5, 2019 by 896gerard
typos

[Phleep]

A W E S O M E. I had been thinking about how great it would be to use a remote operated model boat to take pictures of birds and other wildlife on the water, I hadn't thought about using LEGO though. This shows it can work sooo beautifully. Some amazing footage there at the end. Thank you for sharing