|
|
Jet Driven Radio Controlled Boats 101
Jet boats are a growing area of radio controlled boats. They are appealing to many as the propellers on regular radio controlled boats get entangled in weeds and line and can also hit the ground. All of which will bring you to a shuddering halt. How do they work?
A jet boat is a boat propelled by a jet of water ejected from the back of the craft. A jetboat sucks in water from under the boat into a pump-jet inside the boat, then expels it through a nozzle at the stern. Steering is achieved by motors that move the jet nozzle to either side, or less common, by small gates each side that direct the water. However given the boat relies on the flow of water through the nozzle for control, you must have the throttle open to steer it. The jet expels the jet stream above the water line as it is significantly more efficient as it provides a "clean" hull bottom to avoid drag, allows operation in even shallower water and has no effect on the amount of thrust generated.
Jet powered boats are highly maneuverable, and many can be reversed and brought to a stop quickly. From their larger brethren there is the well known Hamilton turn or "jet spin". This is a tricky high speed maneuver. The boat is turned sharply, the throttle cut which causes the back end (stern) to lift and spin quickly around with a large spectacular spray of water.
One very important feature of the jetboat is that it has no external rotating parts; it is essentially safe for swimmers and marine life, (if you disregard the possibility of being hit by the hull). This in itself is reason enough for some to use this type of propulsion.
Reversing is a bit trickier than a prop. A water jet will continue to pump normally and a deflector aka scoop is lowered into the jetstream after it leaves the outlet nozzle. This deflector pushes the water forward to provide reverse thrust ideally though slightly away from the intake ducts to avoid aeration. Because steering is still available in reverse, you can turn the boat on the spot once you reach a "balance" point with forward and reverse thrust.
Jet boats use a hull shape designed to plane across the water ie the front of the boat lifts out of the water, this reduces drag, boosting speed and maneuverability. Jets have to be operated at speed because at lower speeds, less water pumps through the jet so you lose some steering control and maneuverability. They quickly slow down as the hull comes down and hull resistance is increased. However, loss of steering control at low speeds can be reduced by lowering the reverse deflector slightly and increasing throttle - so you increase thrust and thus control without increasing boat speed itself.
At this point unless you are pretty advanced I would recommend prop driven electric, nitro or gas boats.
|
 |
Please Rate: |
|
Rating: |
 Processing ... |
(Average: Not rated) |
| Views: | 26 | |
|
| More Articles from Hobbies | | |
| Top Articles in Hobbies | | |
|
