Gas Tunnel Hulls - Ready to Race

What is a Tunnel Hull?

GasTunnelHulls and Nitro Tunnel Hulls - In structure and design a tunnel hull has two pontoons running parallel to each other with a canopy (underside of deck) separating them, enabling the air to be channeled between them.

The essence of the gastunnelhull design is to limit the drag coefficient of the actual pontoons coming into contact with the water by creating a lifting effect (flight). This is accomplished as the air is channeled through the tunnel at speed; it is compressed due to the tapered slope of the canopy aft, thus causing a lifting action.

The canopy on section is in the shape of a wing, therefore producing negative pressure on top, enhancing (aiding) the desired lift. This lift is what makes Tunnel hull racing the attraction and challenge to so many, as the third dimension of flight is introduced, to an otherwise two dimensional form of racing as in V bottoms and even Catamarans, that do not use the lift to advance speed, but still enjoy relative low drag due to less hull surface area as they to have pontoons Although more power is required to achieve matching results.

In the actual full size racing tunnel hulls a power trim unit is introduced to the outboard motor, enabling the prop drive line to be varied between negative and positive trim, to play the roll that the aileron does on a plane, to set the angle of attack in the direction of motion (flight).

The trim on the boat is also used to enhance the turning speed in the turns by introducing negative trim, putting more pontoon in the water, lengthening the water line, enabling a sharper turn as it bights on the inside rail of the pontoon. These boats are renowned for there heart stopping G force 90 degree high speed turns that are a true test of a well designed tunnel hull.

In the case of model tunnel hulls, power trim units can be manufactured and run with real effect, creating the third dimension control of flight giving the competitor a big advantage over the competition Should the laid out course have a number of variable left and right turns to it as well as apposing wind direction runs which would allow for the operating pilot to be able to trim the nose up with the wind enhancing the lift and down into the wind limiting the lift to prevent “Blow over” An alternative is to set the boat up with a relational balance between motor trim angle and weight in the nose. Dependent on the conditions of the day however, there will be a particular race line that will be at a disadvantage due a positive motor trim into the wind, that will require less throttle(less speed) or the center of gravity to far forward as in with the wind that will result in more drag (less speed).

The latter has been the norm through out the tunnel model boating world although I have and always will look to and enjoy running power trim when ever possible, adding to the exhilaration of pushing the envelope to maximize the speed of these awesome hulls. Go To - www.gastunnelhulls.com