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The MOC is a floating and remotely controlled catamaran, built with Technic, Mindstorms and typical Lego City bricks.

It features:

* NXT 2.0 brick as a central processing unit,
* two servomotors (one for each of the propellers),
* bluetooth connection with the NXT brick (giving over 10m of the wireless control range),
* easy and intuitive control,
* a lot of free space onboard (so you can build a deck that suits your needs).

Bluetooth signals can be sent to NXT brick in two ways:

1) either by "NXT mobile application" (developed for Lego by NearCell and written in Java),
2) or by "NXTPad" application (developed by Billy Yuen and running under Android OS).

I controlled the catamaran from "NXT mobile application" running on my Nokia E51 but this useful application is supported by other mobile devices as well.

The application should be started in a "Program Control" mode. It can send one of nine different signals to the brick upon pressing keys from 1 to 9. The signals are interpreted by my NXC program running on the brick (and I've also adjusted the program recently to support signals being sent from the "NXTPad").

I attach the following:

* a photo gallery:
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran.html

* render of the digital model of the vessel:
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran_render.jpg

* short movies:
https://youtu.be/4OPX7zKIiyI
(floating in a "stormy" weather conditions)

https://youtu.be/o90Sf0w7dzY
(floating on a calm waters)

In the movies mentioned earlier the catamaran is floating with lego-based propellers, each of which is made from two crossed "2 Blade 9 Diameter" propellers:
https://alpha.bricklink.com/pages/clone/catalogitem.page?P=2952

https://youtu.be/tQMm9HMMEJk
(turning demonstration: the sequences 0:18-0:35 and from 0:57 until the end show gentle turning at different speeds of the propellers)

https://youtu.be/4k5CEHoqIls
(turning demonstration: the sequences 0:16-0:17, 0:25-0:27, 0:38-0:58, and 1:24-1:46 show gentle turning at different speeds of propellers)

In the above movies, in turn, the catamaran is floating with two Dog-Drive 2-blade propellers (55mm in diameter and fitting 4.75mm shaft).
They have been mounted this way:
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran_msp_joiner.jpg

I know also about something called Efferman's propeller:
http://www.shapeways.com/product/5FGQ2E6CX/boat-propellor-5-studs?optionId=40186099

I did not test it but I've read that they behave well.

* building instructions in a PDF:

I'd like to give here my warm thanks to Philippe "Philo" Hurbain for creating for me a digital model of the middle hull - bfloat2c01:
https://alpha.bricklink.com/pages/clone/catalogitem.page?P=bfloat2c01

The PDF has been divided into two parts:

- Part I (main): the catamaran's base
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran_base.pdf
list of parts for the base:
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran_BOM_for_A.pdf

- Part II (optional): the catamaran's deck
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran_base_and_deck.pdf
list of parts for the deck:
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran_BOM_for_B.pdf

* ldr/mpd model:
http://mkpk.knot.kudzia.eu/LegoCatamaran/catamaran_base_and_deck.mpd

* NXC program to run on the brick

Source code:
http://mkpk.knot.kudzia.eu/LegoCatamaran/nxtmaran.nxc

Its compiled version:
http://mkpk.knot.kudzia.eu/LegoCatamaran/nxtmaran.rxe

I've tried to write the program according to the best programming practices. It is commented extensively. Many aspects of the program's functioning can be adjusted to your own MOCs by changing values of the appropriate control variables (defined at the beginning of the code). The aspects include, for instance, propellers' orientation (left-hand vs. right-hand, and responsible variables are named factor_left and factor_right).

After changing the source, the program should be recompiled in the splendid BricxCC environment.
The program should run flawlessly under the standard NXC firmware (though I am using firmware 1.32 enhanced).

* short manuals to the NXC program

The NXTmaran program provides you with three modes of controlling the vessel. The need for switching between the modes has been avoided as the program handles double clicks and other combinations of keystrokes.

I've described control in each of the modes on a numeric keypad of a mobile phone:

1. Basic steering:
http://mkpk.knot.kudzia.eu/LegoCatamaran/basic_steering.pdf

2. Basing steering with a speed regulation (between 0% and 100%, with 10% steps):
http://mkpk.knot.kudzia.eu/LegoCatamaran/basic_steering_speed_regulation.pdf

3. Precise steering (speeds of servomotors can be regulated independently):
http://mkpk.knot.kudzia.eu/LegoCatamaran/precise_steering.pdf

Final remarks:

- the vessel is light and stable enough to not sink easily, nevertheless it is sinkable so I highly recommend you to put styrofoam (or similar material) into side hulls and below plates supporting the auxiliary middle hull (that's what I did),

- protecting servomotor ports from water is worth consideration also (I covered them with a thin paper surrounded by an electrical tape)

I hope you'll enjoy the MOC. And I also hope you can take some inspiration out of it and find it helpful to build your own bluetooth-controlled MOCs. Have a good fun!

At the end I'd like to thank my Wife and my Father for supporting and helping me with this project.
Thank you very much, I love You :-)

MOC-4117

Name NXT RC catamaran (Part I + II: base + deck)
Designer marek.kaminski
Designed 2015
Parts 902
Theme Mindstorms
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This MOC also has a LEGO Digital Designer file available: 3D Model