Introduction to the Hydro Hull Setup:
Hydro style Radio Controlled boats are for high speed realistic looking racing. These high performing Hydro hulls are quite fun, while looking nearly scale, However, it takes some degree of work to tune the hydro hull setup in order to run at their full potential.
Hydro style Racing Hulls in general are designed in such a way that they perform their best only at Wide Open Throttle. Slightly off throttle and they will not perform as well. This style hull is capable of cornering at a typical Oval Race Course turn radius at full throttle. The attached turn fin described later is the main source for this amazing characteristic. At slow speeds the Out Rigger Hull will not be able to turn well. It must be fully on plane. From a dead stop, a hydro style hull sits in the the water quite deep. At initial throttle the front sponsons may slightly plough through the water.
When purchasing the strut for a Hydro Hull, it is important to keep in mind the depth the strut must reach. Commonly, with a strut for a Hydro Hull, the section that holds the prop shaft tends to sit further ahead of the mounting surface. This is different from a strut that would be used with a Mono Hull for example.
When mounting the strut on a Hydro hull it is important to determine the final position the strut will be setup in, for the first initial run. This is due to adjustments that can be performed to the strut for fine tuning. The reference position for the strut and this will also be the first run position, is where the center prop line of the strut is even with the furthest bottom surface or edge of the sponsons. This only holds true in a Hydro style hull that has rear sponsons or an equivalent. If not the strut center line should be placed about 3/8 of an inch below the bottom surface for a 33 inch hull. For a hull around 26 inches in length the strut should be around 1/4 inches in depth. If your hull is different in length, the position should be proportional to the ones provided. This will be the reference position and first initial run position. When mounting the strut is is important to allow adjustment room for raising or possibly lowering the unit. Allow 60% of total adjustment for raising the strut. Keep in mind when raising the strut the screws will reach the bottom of the adjusting slot as the screw remains stationary and the slot slides up. Allow the remaining 40% of the total adjustment for lowering the strut. For example if the strut allowed exactly 1” of height adjustment, 0.6” would be for raising the strut and 0.4” would be for lowering the strut. Prop shaft angle should be set to 0 degrees or neutral for the first initial run. Refer to the drawing below for a better visual of the Hydro Hull Setup.
The turn fin is the fundamental piece that allows the hydro to turn well as if it is on rails. It is critical to the hydro hull setup that the turn fin is properly selected for the hull and properly located. The turn fin is shaped with a round or sharp bent curve near the bottom. This is to allow the hull to hold the corners very well. The bent section of the turn fin points towards the inner hull or interior.
The turn fin is typically mounted at the very rear of the right hand sponson to only allow for right hand turns. Do not attempt placing a turn fin on each sponson as they will fight each other and cause the hull to flip.
Rudder with Water Pickup
A rudder is essential for steering any RC Hydro Hull boat. Select one that is best suited for your hull length. Around 15% of the hull length is a good approximation or starting point. It is recommended but not required to select or choose a rudder with a water pickup. If there is no water pickup in the rudder it is recommended to use an external pickup.
Center of Gravity
Center of Gravity on a Hydro Hull is typically where the turn fin is Mounted. This may be at the rear of the main sponsons or just a few inches behind.