Aerodynamics of lifting fuselages for models (strange project) 1

[bricology]

I'm looking for some information / advice / sources to help with a rather strange project I'm working on; the closest I can come to describing it is to call it a "lifting fuselage/wingless glider model". Here's the brief: to design and build objects that will be launched with an over-the-shoulder throw, rather like throwing a football or launching a model glider, will produce maximum lift, have stable flight characteristics and a long flight. It will be somewhere between 6 - 9 feet long, and will have an aspect ratio of no more than 10:1, which precludes much in the way of wings, but could allow fins for stabilization and a good degree of flexibility in the shape. The weight should be under about 2 kg / 4 lbs. It can't be powered and it won't be radio-controlled. Yes, I realize it can't be made to "fly", any more than a javelin or football actually "flies".

I've done a certain amount of research into the aerodynamics of somewhat related objects such as American footballs and javelins, although they have a couple of significant differences from my project in that they're spin-stabilized and the javelin is thrown from a run. I've looked into airship aerodynamics, but since they're aerostatic, there's not much about them potentially generating lift that I've been able to find. Lifting bodies are somewhat related, although their aspect ratios are far greater (2:1 seems to be typical). In other aircraft, the Shorts Skyvan, some of the troop-carrying gliders of WWII and the old Burnelli airfoil-fuselage planes come to mind.

I'm making a number of full-sized study models at the moment to explore what might work (or doesn't). These include a paper-over-balsa geodesic-frame, a split bamboo pole with the split ribs bent and glued into a long airfoil shape and covered with paper, and an elongated airfoil teardrop made of light-gauge sheet aluminum. I'd rather avoid getting into synthetic or exotic materials or processes, so no vacuum-formed plastics, no aramids, no mylar or the like. Presuming any of this makes sense, and given the admittedly strange parameters of this project, can anyone give any advice as to how I might achieve my aims, or where I might find relevant information? Thanks!

 

[IRstuff]

You should look for "lifting bodies."

TTFN

FAQ731-376

 

[bricology]

Yes, thanks -- I believe that I mentioned them in my second paragraph. They relate, although their aspect ratio is a lot smaller than the a/r of my project. Just the same, I might try just stretching out the profile about 5x as long and see what kind of flight characteristics I can get.

 

[rb1957]

i'd imagine that the launch geometry has a lot to do with the outcome ...launch flight path inclined to horizontal (maybe 30 degs), plane inclined to flight path (2 or 3 degrees up) ... maximum early lift (to gain altitude), gentle stall to control nose down pitch in stall

 

[tmoritz]

Look at blended wing body designs. I suspect you will end up with a flying wing design with a thickened center section to provide volume necessary for payload. Swept wing with twist for pitch stability. You may not need vertical stab since it's a free flight glider, dihedral may be enough. Designing something that is stable during launch is going to be difficult. You will have to comprimise between good glide and pitch stability during launch like rb1957 stated. I would consider a bungee launch like for R/C gliders or at least lever arm like the spear throwers used by early hunters. Lower peak velocity and acceleration.

Good luck,

Tom Moritz