If the question is to use forced induction on a uav...

The answer is probably, "Hell Yeah!". I have been learning everything there is to know about practical, turbocharged-systems. So over the next few posts, I will hopefully generate a reasonable technical approach to safely turbocharge a 4-stroke Briggs and Stratton Animal engine or a Raptor. It depends on which one I can find and afford here in Central Europe.

We have found a few 1.5# turbos good for 3-4psi of boost. The mad scientist in me says that I think we can find some light super chargers and run them on a small electric motor for less weight. I know that the whole point of a turbocharger is more about recovering wasted energy in the exhaust system. However, I wonder if the weight/power generated ratio would be better served with a high efficiency electric motor. Since they are pretty amazing these days.

As I come up with some numbers for weights, and possible concepts, I will keep everyone in the loop.

Fuselage Design Schemes - Vertical Tails do not Make Your Ass End Look Better

Lots of things cross my mind when I start putting pen to paper on a new fuselage. Mostly, it is about needs to go inside, and then how to build it. Over the last few generations of this design, it has become clear that slow-speed, heavy lift (payload/fuselage <0.7) We start to see several key principles begin to precipitate. Today we will focus on the differences in aircraft balance schemes.

Aesthetically, I am not a vertical tail man. They are functional and in many designs they are necessary. My career began in the low-observability sphere. So a large perpendicular plate nailed to the end of your vehicle who is trying to hide invites bigger radar returns. In most of my training and experience, we get away from this with large sweep angle wings and oblique surfaces. Sometimes, these choices do impact performance. If you are working against sines of the angle, you will always have more surface area to get the same net effect.

Balancing the vertical surface weight and the total surface area is always a game. If you look through Jane's for modern high performance, low-observable aircraft, you will see a common theme of split tails. Two tails, let a designer get a net effect and still not have a large single vertical surface. Ok, yeah it weighs more sometimes this is necessary and even suggested.

These principles are not necessarily limited to high-performance  aircraft. Just trying to keep the sail-area down on the aircraft is important. Otherwise it is blown all over the sky like a potato chip in a hurricane. If you are trying to make a vehicle that can stay on station it is easy to fly a slow  constant angular speed turn with a bit of roll angle, rather than balancing a lot of rudder input and trying to fight the wind the whole time and flying search patterns. Sweep angle also lets designers move the center of pressure around for the wing alowing for different internal position management of work payloads.

Many designs on which I have worked use low angle wing tips instead of a vertical tail. Highy-swept low speed wings get most of their roll control from the wing sweep and large ailerons or spoilerons are goos at helping with pitch contro. One interesting solution is coined a "duckeron". I cannot vouch for the scientific nature of the name. A "duckeron" or even a "quackeron" is a surface that consists of a pair of  tip-mounted surfaces at the far end of each aieron. These surfaces open and increase the drag on the wing tip. This is a bit counter intuitive, unike spoilers which run along the span of the wing these are actuay on the trailing edge of the wing and allow for effective yaw control. Sweep helps increase the distance between the wing tip and the aircraft center of gravity. This is the moment arm distance used to calculate the force applied to yaw the aircraft.

It is a pretty clever idea and allows for reduced cross-section yaw control. On rc models and small UAVs the duckeron is a simple single-servo-per-side solution. Rather than only connecting a single surface to the servo arm, you use a pair of rods. As the arm swings pushing the rods away from the hing line opening the surfaces equally. However if there is a clearance issue, the ratio of the opening rates can be changed via a cam or simply varying the lengths of the rods. A shorter rod needs more arm sweep to move the surface through a given range. The air disruption over the wing would make the use of a spoiler less effective. There could be several reasons to use spoilers and ducks at the same time for different flight control cases.

You do have to take into account that the drag at the tip may be an unplanned load on your wing spar. One other kind of side-benefit of using ducks is that they act as airbrakes during landing, even as a counter-balancing yaw force during approach. As a counter-balance on approach you would pay a much steeper drag penalty than a rudder, but they woud be able to apply a much larger yaw force.

Special Thanks to Willy from Nutech-racing.com

A special thanks to Willy from www.Nutech-Racing.com. He is knowledgeable, friendly, freaky fast. I mean he is faster than Jimmy John's sammiches at lunch time. Check out Willy's site for fast, courteous service and great prices on rc stuff and UGV cross-over information.

Thanks again Willy!

The "Fat Man" Is Still Grounded, He Is At the Pub So We Won't Worry Just Yet

Yeah, this kind of sucks. After a year of construction and planning, we find out that there is an international weapons treaty that says that you cannot sell certain weight vehicles internationally that have autonomous guidance systems capable of free flight beyond a certain range. Ok, I get it. Who wants Tom, Dick or Harry building a 150lb (70kg) pop rocket and flying it half way across the planet to make a real mess.

When you think about it, they are just setting rules to make it hard for the forces of evil. I have no interest in being one of the "dark side." My master tells me so. Ok, no more Star Wars references, but I make no promises. If anyone knows more about the "". Or what the real rules are about any of this, please let me know. There is no interest in using this device for any government purpose. I want to pull banners at the beach or to do small scale spraying of crops.

Another question that would be great to hear some explanation of and/or some reasonable listing of what can be discussed between international unmanned vehicle (UAV/UAS/UGV) colleagues. I would hate to blip someone's radar because I was talking about a simple guidance system idea at the pub. Yeah, yeah this is a real problem, I am more likely to be drinking a pint than trying to sink a 40' put on the back nine of Pebble Beach.

I am pretty sure that this is a messy topic and probably best left well-enough alone. However, if there is a chance to get this sorted and get the Fat Man to fly as more than a giant-scale RC plane that would be freaking awesome. Any qualified help is appreciated, I know that the FAA has been pretty draconian in their official guidelines.