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Custom Twin Motorized Lego City 2006 7899 Catamaran Airboat MOC (Twin-Screw)
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This is my custom Lego 7899 Police boat, which is actually built from 2 of the same kits. It is motorized and it was VERY, VERY hard to build; and every single part on this boat was taken exactly from each of the two boats.
About this creation

This is a special MOC compared to my other boats. It is built out of 2 of the same kits. It was an incredible challenge to build though; The lack of parts was like building a castle out of sticks and band-aids. I am pleased with the outcome though, I am proud of my first combination-model. Shown here is the bow view of the boat. As you can see, the boat's beam is very wide, with a 9 1/2 inch beam and it is 18" long, so that means this the largest model I have built yet. At the bow is where the most action is. On each of the two sponsons are seats which can hold one minifigure each. One crew member is already seated; His job will be mentioned later. In the middle of the front deck, there is some equipment and a very small and crude jet-ski. It can hold one minifigure and the minifigure has to stand. In front of the jet-ski launch are air intakes, grab-irons, small spotlights,
navigation lights and rotating marine radar. The jet-ski's nose is slanted to allow the radar to rotate. I have used a battery from an R/C car to prop up the bow. (This boat is very heavy as well!)

Here is the stern view of the boat. On the stern deck is a small equipment holding area, and on top of that is the storage mount for another small and crude remote-controlled PSA or UAV (Police Surveillance Aircraft, Unmanned Aerial Vehicle) which replaces the small helicopter included in the original kit. Underneath the PSA is a rack with a warning light and a transceiver. Below the equipment storage is a small area with a seat and some marine radar monitors. On both port and starboard are two very large gearboxes and mounting housings which drive the 2 4-bladed propellers. (The propellers are the main rotors off the original kit's helicopters) Behind the propellers are very large movable rudders with trim-tabs located at the top. The rudders move but they are very fragile. Somebody with orange fur and whiskers already knocked them off by accident) The air propellers obviously are non-functional and do not produce any thrust. This boat's main propulsion are two motors (water screws) located in the rear hull mounts. They produce a "boat" loat of thrust and ironically they are not counter-rotating and this boat does not have any torque problems. Rudders can be added if needed. This boat is also very fast due to the midship mounting of the decks.

Here is the very small and very crude jet-ski. It holds one minifigure which has to stand in order to reach the handlebars. The two jet nozzles have cooling water exits on them, and the entire jet pump's trim can be adjusted since it is built on a 1x2 hinge brick. A small engine is located at the stern.

Here is the PSA. As mentioned before, it is located at the stern. The propellers are the tail rotors off of the original helicopters. It has a camera and navigation lights located on the bottom. The pilot is ironically the original helicopter pilot.

Here is the small and cramped holding cell which can fit two prisoners. One criminal is already in a bunk. Not much to see here except for 1x1 studs and water stains. Above the holding cell is the flybridge, and it seats the captain who is at the controls with two monitors and two levers to control the rudders. Above the windshields are a small mast with an antenna at the rear and navigation lights and a small light.

Stern view with the PSA unmounted. You can see the equipment and cell windows.

Here are all of the leftover pieces, which includes windows, antennas, lights, crewmembers and the motor's rudders which are optional.

Photo of the original kit (This boat is built using two of those)



Comments

 I made it 
  August 2, 2017
Quoting Builder Allan Cool! Very nice catamaran. Especially considering the limitation in parts. I agree with Jeremy it would be interesting to see a video of this one to see how fast it goes :-)
Thanks Allan! This model was quite a challenge since the original kit didn't have many plates. It is very robust though! I have not uploaded a video yet since I have been having some equipment issues, but I can try to get a video of it soon. Some of my other models have videos though.
 I like it 
  August 2, 2017
Cool! Very nice catamaran. Especially considering the limitation in parts. I agree with Jeremy it would be interesting to see a video of this one to see how fast it goes :-)
 I made it 
  August 1, 2017
Quoting Jeremy McCreary Nice power catamaran, Angelo! These are fast hulls. Would love to see a video! If you're feeling a need for more speed in the water, try separating the hulls more. As a rule of thumb, hull separation (from the centerline of hull to the other) should be ~50% of waterline length to minimize interference resistance due to wavemaking between hulls. I know that increasing hull separation will pose some structural challenges, but in my experience with many a LEGO power cat, the speed gain is worth the hassle.
Thanks! It seems that the 7899 hulls are lighter than the 7906 hull. Not exactly sure if there is a difference, but this boat is definitely fast. I do not have much experience with catamarans though; but I do have a fast R/C model of one and it seems that the hulls are pretty close together. It goes at about 29 mph easy. I am still testing this design and I will upload a video soon. I might not be able to separate the hulls though since the bow deck is held on just by 2 studs across, and it may make the hull weaker. I could try it though. I do not use the motor's rudders since they have a tendency to move on their own due to torque and propeller thrust. I might be able to build a large rudder in the center though. Thanks for the help!
 I like it 
  August 1, 2017
Nice power catamaran, Angelo! These are fast hulls. Would love to see a video! If you're feeling a need for more speed in the water, try separating the hulls more. As a rule of thumb, hull separation (from the centerline of hull to the other) should be ~50% of waterline length to minimize interference resistance due to wavemaking between hulls. I know that increasing hull separation will pose some structural challenges, but in my experience with many a LEGO power cat, the speed gain is worth the hassle.
 
By Angelo Filipelli
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LEGO models my own creation MOCpages toys shop Custom Twin Motorized Lego City 2006 7899 Catamaran Airboat MOC (Twin-Screw)Boats


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