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Starter boat assembly

The MARLIN Starter Kit builds one starter boat: a floating robot with two Underwater Thrusters for movement and a T Flipper for pushing Hex Links around. It will not win a Match on its own, but it gets your team on the water quickly and every part of it can be moved, replaced, or thrown away once you have your own ideas.

The finished starter boat from two angles. A sealed Robot Brain sits on an aluminium beam frame carried by four float blocks, with a T shaped flipper arm on the front beam, shown once raised and once lowered.

Build it in this order. Each stage finishes a piece that the next stage bolts together:

  1. Thruster floats — two of them
  2. T Flipper
  3. Robot Brain battery — fit it and close the box up
  4. Final assembly — the frame that joins everything

Tools

The kit includes one double ended spanner: 7 mm for M4 nuts, 5.5 mm for M3 nuts. You also need hex keys for the screw heads.

Wherever a step pairs a screw with a nut, hold the nut with the spanner while you turn the screw.

Know your parts

Float blocks

Four sealed 3D printed blocks keep the boat on the surface. Two are plain, and two are thruster blocks with a mounting recess for an Underwater Thruster.

Four float blocks arranged under a ghosted robot frame, with one smaller block shown separately as the thruster variant carrying a motor.

Beams

The frame is aluminium box tube drilled with 4 mm holes on a 15 mm pitch. Two profiles come in the kit, and the guide names them by profile:

Name Said as Section
"1x" beam "one by" Square, 15 × 15 mm
"2x" beam "two by" Rectangular, 30 × 15 mm

Two views of the same robot frame. The left highlights the narrow square 1x beams, the right highlights the wider rectangular 2x beams.

Robot Brain

The sealed box that runs your code. Its ports are the ones you name in Robot.configure(): Motor/Servo Ports M1 to M8 for Thrusters and Servos, Sensor Ports S1 to S6 for MARLIN sensor modules.

The Robot Brain mounted on the robot frame, with the connector face called out below. One block of ports is labelled Motor / Servo Port and the other Sensor Port.

Thrusters and Servos

Two kinds of actuator, and the difference matters when you write code. An Underwater Thruster spins continuously and has no idea where it is. A Servomotor turns to the angle you command.

An Underwater Thruster with its propeller alongside a black servomotor.

Screw codes

Screws are named M<diameter> x <length>, both in millimetres. Length is measured from under the head, so an M4 × 20 and an M4 × 30 fit the same hole but reach different depths.

Three screws drawn side by side, M3 x 12, M4 x 12 and M5 x 12, with the diameter measured across the shaft and the length measured from under the head to the tip.

Thruster floats

Build two of these. Per float:

Part Quantity
Float block, thruster version 1
Motor with propeller 1
Motor bracket 1
M5 × 8 screw 2

Exploded parts for one thruster float: the thruster version float block, a motor bracket, a motor with propeller, and two M5 x 8 screws, with a note that two floats are to be assembled.

  1. Take a thruster float block.
  2. Lay the motor into the recess with the propeller facing out and the cable running into the block.
  3. Put the bracket over the motor body and fix it with 2× M5 × 8.

Three panels: an empty float block, the motor seated in its recess, then the bracket clamped over the motor with two M5 x 8 screws, ending in a completed thruster float.

The two thrusters are not identical

One motor has a clockwise propeller and the other counterclockwise. Fit one of each, one per float. Two of the same rotation will make the boat yaw whenever you drive straight.

The two thrusters side by side, one labelled counterclockwise and one clockwise, each with an arrow showing the direction its propeller turns.

T Flipper

The T Flipper is the starter boat's arm. A servo tilts a crossbar up and down to break up scored Hex Links, flip them to your Alliance colour, or push them around.

Part Quantity
"1x" beam, 120 mm (crossbar) 1
"1x" beam, 120 mm (upright) 1
T mount 1
Servo arm connector 1
Servo arm 1
Servo 1
M4 × 30 screw 4
M4 × 20 screw 2
M4 nut 4
M3 × 12 screw 1
M3 × 6 screw 1

Parts laid out for the T Flipper: a 120mm 1x beam, a T mount, a servo arm connector, a servo arm, a servo, and the M4 and M3 screws and nuts.

Crossbar and mount

  1. Lay the 120 mm "1x" beam flat.
  2. Sit the T mount across it, over the centre holes.
  3. Fix it with 2× M4 × 30 and 2× M4 nuts.

Three panels: the bare beam, the T mount placed on top of it, then two M4 x 30 screws dropped through with two M4 nuts underneath, with a reminder to tighten with the provided wrench.

Upright and servo connector

  1. Stand the second 120 mm "1x" beam upright and slide its end into the T mount.
  2. Fix it with 1× M4 × 20 and 1× M4 nut.
  3. Push the servo arm connector onto the bottom end of the upright.

Three panels: the upright beam offered up to the underside of the T mount, then fixed with one M4 x 20 screw and nut, then the small servo arm connector fitted to the lower end of the upright.

Servo arm and servo

  1. Fix the servo arm connector with 1× M4 × 20 and 1× M4 nut.
  2. Attach the servo arm to the connector with 1× M3 × 12.
  3. Attach the servo to the arm with 1× M3 × 6.

Three panels: the connector fastened with an M4 x 20 and nut, the servo arm added with an M3 x 12, then the servo itself fixed with an M3 x 6, ending in a completed T Flipper.

Before you bolt it to the boat, turn the servo by hand through its travel. The crossbar should sweep from pointing up, through horizontal, to pointing down, without fouling the upright.

Four views of the assembled T Flipper at different servo angles, from crossbar up through horizontal to crossbar down.

Robot Brain battery

The Robot Brain ships sealed. Open it once to fit the battery, then close it properly. Everything inside is electronics, and the seal is the only thing keeping the water out.

Open it upright, never upside down

Hold the Robot Brain the right way up before you loosen anything. Water sitting on the lid will run straight into the electronics if you open it inverted.

  1. Set the Robot Brain upright on the bench.
  2. Loosen the lid screws and lift the top off the baseplate.
  3. Drop the battery into the tray and connect the battery connector. The Brain powers up, so pair it with a controller now while the box is open.

Three panels: the Robot Brain held upright, the top lifted off to show the sealing gasket around the baseplate, then the battery lowered into the tray.

  1. Latch the battery down so it cannot slide around.
  2. Refit the top and tighten the screws evenly.

Two panels: the battery latched into the baseplate, then the top refitted over the gasket and screwed down, giving a closed Robot Brain.

Check the gasket before you tighten

The gasket must sit in its groove all the way round. If it has fallen out, lay it back into the baseplate groove, then fit the retaining ring over it before closing the lid.

The baseplate shown alone, then exploded into baseplate, gasket and retaining ring, then reassembled with the gasket seated in its groove.

Final assembly

Everything below assumes you have 2 thruster floats, 1 T Flipper, and 1 closed Robot Brain ready.

Part Quantity
"1x" beam, 240 mm 3
"2x" beam, 240 mm 3
Float block, plain 2
Flipper servo mount 1
M4 × 50 screw 2
M4 × 40 screw 4
M4 × 35 screw 8
M4 × 30 screw 2
M4 nut 8
M3 × 12 screw 4

Parts for the final assembly: three 1x beams and three 2x beams at 240mm, two plain float blocks, the flipper servo mount, and the M4 and M3 screws and nuts.

Two of the 240 mm "1x" beams are used here: the back beam and the centre beam.

1. Back beam

Set a 240 mm "1x" beam aside as the back beam. It carries the rear end of the Robot Brain in the next step.

2. Centre beam and Robot Brain

  1. Lay the centre beam along the boat and the back beam across it.
  2. Sit the Robot Brain on top, mounting feet over the beam holes.
  3. Fix it with 2× M4 × 50 and 2× M4 × 30, and 4× M4 nuts underneath.

The Robot Brain lowered onto a cross of two beams, with two M4 x 50 and two M4 x 30 screws passing down through it into four M4 nuts, and the result standing on the beams.

3. Front beam

  1. Lay a 240 mm "2x" beam across the front of the frame.
  2. Place the flipper servo mount on it, facing forward.
  3. Fix both with 4× M4 × 40 and 4× M4 nuts.

A 2x beam laid across the front of the frame with the flipper servo mount on it, fixed by four M4 x 40 screws into four M4 nuts.

4. Side beams and plain floats

  1. Lay the two remaining 240 mm "2x" beams along the sides, bridging the front and back beams.
  2. Bring the two plain float blocks up under the outer ends.
  3. Fix each float with 2× M4 × 35 down through the side beam, 4× in total.

Two side beams added along the frame with plain float blocks below them, fixed by four M4 x 35 screws, and the resulting frame standing on its floats.

5. Thruster floats

Fit the two thruster floats to the remaining positions with 4× M4 × 35, two per float. Point both propellers the same way, and keep the clockwise and counterclockwise floats on opposite sides.

The two thruster floats brought up to the frame and fixed with four M4 x 35 screws, giving a boat standing on four float blocks.

6. T Flipper

Bolt the T Flipper's servo to the flipper servo mount on the front beam with 4× M3 × 12.

The assembled T Flipper offered up to the mount on the front beam of the floating frame, fixed with four M3 x 12 screws.

The starter boat with the T Flipper mounted on the front beam, crossbar raised above the frame.

With the flipper mounted, tilt it by hand through its full travel once more. The crossbar must clear the front beam and the floats at both ends.

Next steps

Plug the thrusters and the flipper servo into the Motor/Servo Ports, note which port each one uses, then declare them in code:

robot.configure(
    effectors={"M1": Thruster, "M2": Thruster, "M3": Servo},
)

The port names have to match what you physically plugged in. See Hardware configuration for the rules, and Your first program to make the boat move.