Prepare For Liftoff
Many people have asked me why we are taking the time to build a scale model. My answer is always the same. Like any engineer, we like to prove our theories in a controlled manner before moving along to the next, more expensive phase of the project. Today was a perfect example of why we do this.
If you have been following our progress since the beginning of this year, or earlier, you will already know that I spent some hard earned cash back in February employing an ex NASA aerodynamic engineer to have him verify the aerodynamic assumptions that I had made when I first created the dimensions of the Raptor. He ultimately found that the wider fuselage was creating a large pitching moment and therefore recommended that we move the wing back to compensate for that effect. He also suggested that we reduce the size of the canard and decrease the angle of attack as the fuselage pitching moment meant we needed less lift on the canard. I went along with what he suggested (the guy worked at NASA) but at that point decided that we were definitely going to build and fly the 1/4 scale model as I was not 100% convinced.
Fast forward to today when we were taxi testing the Raptor model. It was fairly obvious that we had a problem as the aircraft’s nose would not lift off. We made an adjustment to increase the elevator travel and we also moved the CG back a little but still within the acceptable range from the design specs. The nose would still not lift off. So now we have more engineering to do.
Our next step will be to use the CNC to mill a new canard that is slightly larger in total area. We are then going to set it up so we can adjust the angle of attack during testing. This way we can figure out exactly where the canard needs to be with area, and angle of attack.
Fortunately I had expected us to have to make some adjustments to the canard so this is not really a surprise. It will be all the more satisfying for us to dial it in. Ultimately we will have this all sorted out so we don’t have to do it with the full scale prototype. That’s engineering and that’s why we create a model.