Boat Mechanical Design

Boat Structure

We decided to go with a pontoon-shaped hull constructed from closed cell foam.  This design was simple to build and very stable. It also allowed for us to hover over the crab pots to read the RFID cards.  The platform has an array of bolt holes allowing for the pieces of glass to be fixed in different locations if we needed to rearrange.  Two plastic tupperware containers are used to hold the electronics; wires run between them through 1'' plastic tubing.  The containers are fixed to the platform with velcro so they could be rearrangeable.  The water-logged funnel is mounted approximately 1 foot high through a PVC pipe.  The water drains into the water through the PVC.   The water-logged light is a collection of 15 white LEDs mounted on top of the plastic container.  The crab capacity indicator is a servo dial mounted on top of the other plastic container.

Propulsion System

We use two motor units and steer by differing motor speeds.  The motors are housed in 1" PVC.  The drive shaft is attached to the motor shaft with a universal joint.  The drive shaft sits in a brass bushing which exits the PVC container through the end.  The brass bushing is filled with grease so that water does not enter the PVC casing.  The casing is sealed with silicone to prevent water leakage.  The motor unit is placed in a cavity under the foam hull and sealed with silicone.  Having the motor units under the hulls kept them away from possible encounters with objects, other boats, and crab pots.  

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Water Cannon System

The water cannon system consists of a Rule 1100 Gallon Per Hour bilge pump, two 3/4'' delivery tubes, and 1/4'' nozzles mounted to a servo.   The pump is mounted below the platform in the rear of the boat. The tubes were annealed with a heat gun to alleviate the pre-stress which allows the tubes to conform to the configuration needed.  The tubes were run through a slot so that slack could be taken in and out when the servo rotates.  45 degree brackets attach the nozzles to the servo body.  The pedals of the controller are used to control the position of the servos.  The nozzles have the ability to rotate through 180 degrees.  This was probably the coolest function of our boat.  The guns can be aimed independently and it shoots over 10 feet!