Grimace
Well-Known Member
Some material testing may be required here, but follow along with me on the basics.
Primary gliders just have a truss with two dimensional "spar caps" and some reinforcing at the joints. These tails tend to be rather short, which I assume reduces twisting forces. They may also use some wire bracing, I've seen.
So why not an I-beam for the tail? Specifically, a composite I-beam with preformed carbon fiber rods, where the flanges of the I-beam get wider at they approach the cg in order to provide more lateral stiffness. I think you could even increase the radius of the fillet on the inside of the flanges (as you go towards the cg of the plane) to increase resistance to rotational forces and also stiffness to resist vertical tail / rudder forces. From the back of my napkin, it looks like something like a 3 inch wide flange top and bottom which widens out to about 6 inches (3 inches per side) at the base of the tail ought to be capable of doing what a tail needs to do.
I know someone will ask why, so here's the reasoning: the idea is to build a simple part 103 glider with nothing but 2 dimensional molds. Basically, nothing more complex than aluminum or steel sheet, either bent or curved, serving as a mold (with some obvious exceptions for things like wingtips, nose bowl, etc).
And I think that on a low-speed glider, with a Vne of something around 85mph, such a simple way of extending the tail rearward ought to be possible without too much of a weight penalty over, say, the Carbon Dragons split mold (Formica/Plexi) design which is elegant, but more time consuming.
The big issue is that I haven't seen this done before, so I wonder what I'm missing.
Primary gliders just have a truss with two dimensional "spar caps" and some reinforcing at the joints. These tails tend to be rather short, which I assume reduces twisting forces. They may also use some wire bracing, I've seen.
So why not an I-beam for the tail? Specifically, a composite I-beam with preformed carbon fiber rods, where the flanges of the I-beam get wider at they approach the cg in order to provide more lateral stiffness. I think you could even increase the radius of the fillet on the inside of the flanges (as you go towards the cg of the plane) to increase resistance to rotational forces and also stiffness to resist vertical tail / rudder forces. From the back of my napkin, it looks like something like a 3 inch wide flange top and bottom which widens out to about 6 inches (3 inches per side) at the base of the tail ought to be capable of doing what a tail needs to do.
I know someone will ask why, so here's the reasoning: the idea is to build a simple part 103 glider with nothing but 2 dimensional molds. Basically, nothing more complex than aluminum or steel sheet, either bent or curved, serving as a mold (with some obvious exceptions for things like wingtips, nose bowl, etc).
And I think that on a low-speed glider, with a Vne of something around 85mph, such a simple way of extending the tail rearward ought to be possible without too much of a weight penalty over, say, the Carbon Dragons split mold (Formica/Plexi) design which is elegant, but more time consuming.
The big issue is that I haven't seen this done before, so I wonder what I'm missing.