Renegadenemo wrote: ↑
Wed Sep 05, 2018 9:24 am
There's two effects from the spinning engine. One is the precession of the rotatives such that a right hand input will cause the nose to rise and vice-versa. The other is the torque reaction - the compressor spins one way so it wants to rotate the boat around it in the other direction.
Hi Bill, Joerg, one of "the Germans" (and RC model boat guy) from the Isle of Bute here.
[/smart ass mode ON]
Actually there a 3 effects:
1. "dynamic torque" - when the rotating mass of the turbine changes its roation speed, when it accelerates or decelerates, then you see a force on the hull in the opposite direction of the rotation during acceleration and in the same direction during deceleration. If the rotation speed stays constant, then there is no such kind of dynamic force. Because a turbine changes its rotation speed rather slowly (compared to an IC or electric motor) such forces are rather small, so not sure of you see them.
2. "static torque" - when the rotating mass of the turbine rotates at constant speed and if the axis of the rotations does not change its direction, this is when the vehicle stands still or drives straight(!) in one direction, and the turbine - as a motor - produces thrust, then you might see forces due this thrust. In case of a water prop drive boat you see significant torque due to the rotating prop transfering forces to the water. In case of a turbine or a jet, be it an air or water jet, the amount of torque you notive on the hull depends on how much the spin of the air/water flow created within the thrust disc of the propulsion system gets removed behind it. Typically for such system designs is that they try to remove such spin completely - using fins behind the thrust disc - so in the end the complete drive system is more or less free of torque transfer onto the hull - good examples are jet powered boats. Looking at the stream behind K7 turbine, I didn't notice much spin in the air flow - if at all. Thus at power there should be very little torque reaction on the K7 hull. This might have been different for the older Beryl design - did this thrust cone show more spin?
3. "gyroscopic forces" - these are the typical forces everyone might remember from school when you spin a bicycle wheel and try to tilt the rotation axis -> the real movement is always vertical to both the axis and the direction you push it to - known as the right hand rule. K7 sees such forces when either turning - depending on direction it will either lift or push the bow - or when running over waves - when the bow tries to bounce up and down - but instead the boat turns left and right. So some effects which Ted described as side wind effects from tail fin might come from running in rought water.
[/smart ass mode OFF]
Ted, we talked on Bute about applying the water brake and how tricky this is - through the steering wheel. You might want to explain this again as this might be of interrest to understand why K7 was found with the brake down, but still flipping without any sign it beeing applied. Then, how does it feel when you apply it? Bill wrote somewhere you almost bit into the steering wheel, but at the same time it didn't slow the boat down much - how did that feel? Second, looking at old footage and also the videos of the first week on Bute it seams as if K7, once one plane and when more power was applied, pushes at first the bow down into the water again, creating a lot of spray. Is my oberservation correct? If so, did you ever find a way to avoid this, by either acceleration slower once on plane - or giving more power to get on plane and then directly accelerate from there?