RCU Forums - View Single Post - Airboat gets unstabel when getting over a certen speed
Old 05-02-2008, 09:34 AM
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Mr Cajun Gator
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Default RE: Airboat gets unstabel when getting over a certen speed

I have not had good luck with any cat style set up on the airboats. They all seem to have control troubles. Many things can cause hopping or skipping. With out having the boat in my hands it is very hard to say what is causing it. Weight, shape, direction of force, water friction, direction of airflow. What makes a boat skip or hop, is that it is trying to fly, but can not. You are getting a force that is causing too much lift on the front but not enough to hold the lift, so it falls back down, in a cycle. The shape of the rake can cause this, on how much angle it has. A defect on the bottom can cause this as the water passes, it will try to follow the shape of the hull. If there is a place that as the water passes and is trying to cause the boat to lift it may not be enough to hold on and again causing hopping. This stuff is very hard for me to explain.
Best I can say is that on the bottom, you want the water to be able to release easy. Cause the best way to give a better idea, run your boat and try to spin it around so that the boat actually slides in reverse, you will see that the back of the boat will raise as the water holds on the the bottom as it follows the rake.
Having the prop airflow pointed towards the water will help to keep the bow down, too much will cause your boat to hook and spin out while trying to make a turn.
CoG can have some effect, but this does not effect the air prop boats as much as the water prop boat. Main reason is that the force point to make the boat move on the air prop is on the top side of the boat vs the bottom side of the boat on the water props.
No 2 home made boats will run the same, so you will need to study your boat and try to picture what happens as the air and water passes across your boat. Check anything that will not allow release, study every thing that changes the flow of the air and water. Some things have more effect than others, but as you study it, you will get a better understanding of just what is happening, making it easer to find the problem.