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<HTML> <BODY BGCOLOR="FFFFFF" TEXT="000000" LINK="000099" ALINK="ff0000" VLINK="000099"> <HEAD><TITLE> Hovercraft Control Methods </TITLE></HEAD> <br><br><br> <h1> Hovercraft Control Methods</h1> Hovercraft control methods can be grouped into three general categories: <br><br> 1) Thrust Air Manipulation <br> 2) Cushion Air Manipulation <br> 3) Directed Propulsion. <br><br>This page shows examples of each category.<br> <hr><hr> <h2> Thrust Air Manipulation</h2> <hr> <br> <img src="gunson-rudders.jpg" height=175><br> <img src="twin-rudders-TWOVAN.jpg" height=175> <img src="triple-rudders-SUR6.jpg" height=175> <img src="five-rudders.jpg" height=175> <br> <b> Vertical air rudders<br> </b> Rudders moving back and forth behind the propeller can point the craft to the left or right. Multiple rudders are often used to turn as much of the thrust airflow as possible. <br><br> <hr> <br> <img src="trim-wing-and-three-rudders12R at troy.jpg" height=175><br> <b> Horizontal Air Rudders <br> </b> Look carefully behind the propeller in the above photo, and you'll see horizontal as well as vertical services. Often called "elevators" or "trim wings", horizontal rudders can divert the thrust airflow upwards or downwards, causing the hovercraft to tip forward or back. If the hovercraft's payload is causing the tail to drag, an elevator can level out the craft by causing the craft to tip forward. <br> In the racing situation shown above, the elevator might set to help the nose tip upward when coming onto land, but then would be used to tip the craft back downward so that it doesn't flip over. <br> <hr> <br> <img src="Elevons-others_riverrover_mkIII.jpg" height=225><br> <b> Elevons - Differential Use Of Horizontal Rudders<br> </b> Elevators placed side by side are called elevons. Elevons can be pointed in opposite directions to roll the craft into a turn.<br> <hr> <br> <img src="donar-MVC-077S.jpg" height=175> <img src="donar-MVC-084S.jpg" height=175><br> <b> V-Tail<br> </b> An innovative hybrid system -- diagonal surfaces can work like rudders and elevons at the same time. <hr> <br> <img src="Pivot-BH7.jpg" height=175> <img src="lbh72.jpg" height=175><br> <b> Fins<br> </b> Stationary rudders can be used to stabilize a craft's orientation. <hr> <br> <img src="reverse-bucket-backingup-talviranta.jpg" height=175> <img src="reverse-bucket-closed-part3501_3_large.jpg" height=175> <img src="reverse-bucket-open-thrust-big.jpg" height=175> <img src="reverse-bucket-cruise-model1874_6.jpg" height=175> <br> <b> Reverse Buckets<br> </b> Twin buckets can do triple duty as brakes, reverse gear, and rudders. Each bucket can wing into the thrust duct's airflow and turns the air 180 degrees so that it blows toward the front of the craft instead of the rear. The two buckets can be used together or separately. When the buckets are used together to swing into the thrust duct's airflow, they turn the air 180 degrees, and cause the craft to slow. After the craft slows to a stop, if thrust is continued, the buckets will cause the craft to go backwards. If, instead, only one of the buckets is used, the craft will turn to the left or right. When neither bucket is used, the buckets are kept out of the airflow to allow the craft to go forward.<br> <hr> <br> <b> Thrust Blockers<br> </b> Instead of buckets, simple flat surfaces can block the thrust airflow. This is useful for single motor hovercraft operators who want to keep the motor running to provide lift, but don't want to keep accelerating forward. <hr> <br> <br> <hr><hr> <h2> <b> Cushion Air Manipulation</b> </h2> <hr> <img src="main.jpeg" height=175> <img src="main-4.jpeg" height=175> <!-- <img src="main-6.jpeg" height=175> --> <img src="main-5.jpeg" height=175> <img src="main-7.jpeg" height=175> <br> <b> Weight shift<br> </b> In small racing crafts, drivers use their bodies to steer the craft (much like a bicycle) to lean into a turn. . It works very well - sometimes even a little too well if the driver is thrown from the craft! For very large craft, fuel is pumped from one side of the craft to the other to help steer the craft. Although your model hovercraft is unmanned and does not use liquid fuel, the weight shift steering method <b>can</b> be used if you can find some other weight to shift back and forth. <hr> <br> <img src="skirt-lift-gunson.jpg" height=175><br> <b> Skirt shift & skirt lift<br> </b> Instead of shifting a weight, a hovercraft can also be controlled by extending the skirt outward, which changes the center of mass. <br><br> Alternatively, the skirt can be lifted up on one side using cables, which causes the craft to lean into a turn, as shown above. <hr> <br> <img src="skirt-valve-sevtec.jpg" height=175><br> <b> Cushion valves<br> </b> Some hovercraft have multiple sections of skirt. The hovercraft shown above has a separate skirt in front. Slots seen in the front of the skirt can be opened, which vents the skirt in front. This causes the skirt to collapse in the front, causing the hovercraft to slow down as the front of the hovercraft makes contact with the suface. <hr> <br> <hr><hr> <br> <h2> <b> Directed Propulsion</b> </h2> <hr> <img src="swivel-gunson.jpg" height-175> <img src="lsrn24.jpg" height=175> <!-- <img src="Pivot-BH7.jpg" height=175> --> <img src="lbh72.jpg" height=175><br> <b> Swiveling thrusters <br> </b> One or more propellers or fans can be placed on a swivel to control the hovercraft. <hr> <br> <img src="gimbal-single-kids_ride1_small350.JPG" height=175> <img src="gimbal-twin-amphib_winter1_small.JPG" height=175> <br> <b> Gimbaled thrusters <br> </b> One or more fans can even be placed on a gimbal. A gimbal allows the thruster to swivel up and down as well as to the left and right. This allows the hovercraft to control how much lift versus thrust a motor provides, as well as allowing the hovercraft to turn to the left and right. <hr> <br> <img src="gunson-differential-thrust.jpg" height=175> <img src="twin-thrusters.jpg" height=175> <br> <b> Differential Thrust From Multiple Thrusters <br> </b> Twin thrusters which blow different amounts of air in the same direction will turn a hovercraft. The hovercraft will turn even faster if one of the thrusters blows air in the opposite direction. <hr> <br> <img src="puffports-gunson.jpg" height=175><br> <b> Puff Ports <br> </b> For low speed turning, the craft's cushion air can be vented to one side to push the craft the other way. <hr><hr> <br> That's not the end - there are many other ways to control a hovercraft! Some experimenters have experimented with devices which can be raised and lowered to provide intermittent contact with the land or water. Some experimenters have used wheels (and paddle wheels, for water) which also sometimes can be raised and lowered. Other experimenters have tried using sails and kites and parachutes. Still other enthusiasts have tried using wings, and even rockets. <!-- Comments below this line A nice summary from the 1970: <img src="gunson.jpg" height=250> <br> lsrn24.jpg lbh72.jpg gimbal-twin-amphib_winter1_small.JPG gimbal-single-kids_ride1_small350.JPG Pivot-BH7.jpg donar-MVC-084S.jpg AP188hov09.gif jean bertin new skirt donar-MVC-077S.jpg twin-rudders-TWOVAN.jpg triple-rudders-SUR6.jpg triple-rudders-and-skirt-valve-kisselvan.jpg trim-wing-and-three-rudders12R at troy.jpg lsrn29.jpg two-ducts-three-rudders-dscf0579.jpg five-rudders06.jpg twin-rudders-54sevredtop.jpg control-methods.html -->