Post by bearcat on Nov 23, 2009 17:43:42 GMT -5
I've been chewing on an idea for some time now. It's another way to launch an old-school sailplane that only has the hook for the high start near the center of gravity.
Being an old free-flight builder, I'm fairly comfortable with flying free-flight planes. That comes with a risk though. The mortality rate tends to be kind of high, because of the rough landings, hitting fences and buildings, etc. But you build a FF plane to turn in a slow circle, so that you don't lose it.
My idea is to build a FF-self-powered booster plane, which simply slides onto the high-start hook at the CG and centers itself onto the plane's fuselage. As long as it's under power and pulling the entire assembly, it will stay attached to the tow hook of the sailplane. As soon as its batteries run out, aerodynamic drag will pull it back, until it falls off of the tow hook, and it'll simply glide in a circular pattern back to earth. With a method like this, you can get really high altitude, higher than a high start.
Problem is, chances are, any prevailing wind at all is going to carry this plane a long way off. It either needs a good spotter, or it needs an electronic locator. But if I'm going to go through THAT much trouble, might as well put a whole different radio system in it and have a second pilot bring it down for a controlled landing.
Originally, I was going to use an 0.049 engine for this. I have a couple of those sitting around, because I used to also do a lot of control line. But prop clearance underneath the sailplane is a problem. So I think a better idea is to use a strong ducted fan motor. On its own, this plane might look a bit peculiar because of how it needs to be designed for a sailplane to ride piggy-back, but it would have the exact same CG as the sailplane, so that it could fly very well without a sailplane on its back.
The design I'm contemplating would have a twin-tail, to nestle between the fuselage of the glider it's towing, and probably needs adjustable bumpers that can be raised to support the wing of the glider. That way you don't get any weird roll tendancies. And it'll probably be about half the size of a 2-meter sailplane. Basically, going up, you'd have a biplane, and they separate into two different aircraft at altitude.
If it's radio controlled, it could also just separate manually, or idle the motor and it'll slide off.
Cool idea?
Being an old free-flight builder, I'm fairly comfortable with flying free-flight planes. That comes with a risk though. The mortality rate tends to be kind of high, because of the rough landings, hitting fences and buildings, etc. But you build a FF plane to turn in a slow circle, so that you don't lose it.
My idea is to build a FF-self-powered booster plane, which simply slides onto the high-start hook at the CG and centers itself onto the plane's fuselage. As long as it's under power and pulling the entire assembly, it will stay attached to the tow hook of the sailplane. As soon as its batteries run out, aerodynamic drag will pull it back, until it falls off of the tow hook, and it'll simply glide in a circular pattern back to earth. With a method like this, you can get really high altitude, higher than a high start.
Problem is, chances are, any prevailing wind at all is going to carry this plane a long way off. It either needs a good spotter, or it needs an electronic locator. But if I'm going to go through THAT much trouble, might as well put a whole different radio system in it and have a second pilot bring it down for a controlled landing.
Originally, I was going to use an 0.049 engine for this. I have a couple of those sitting around, because I used to also do a lot of control line. But prop clearance underneath the sailplane is a problem. So I think a better idea is to use a strong ducted fan motor. On its own, this plane might look a bit peculiar because of how it needs to be designed for a sailplane to ride piggy-back, but it would have the exact same CG as the sailplane, so that it could fly very well without a sailplane on its back.
The design I'm contemplating would have a twin-tail, to nestle between the fuselage of the glider it's towing, and probably needs adjustable bumpers that can be raised to support the wing of the glider. That way you don't get any weird roll tendancies. And it'll probably be about half the size of a 2-meter sailplane. Basically, going up, you'd have a biplane, and they separate into two different aircraft at altitude.
If it's radio controlled, it could also just separate manually, or idle the motor and it'll slide off.
Cool idea?
