Hello all,
Where to start... Well, My name is Justin, and aviation is my life. I grew up in a family with aviation in our heart and blood. Everyone in my family has been in some sort of aviation, whether it is Full scale helis, prop jobs, jets/airliners, hang gliders, or even home built aircraft. I solo'd at 18 yrs old with only 9 instructor hours, and continue to enjoy every aspect of aviation. I am currently serving in the USAF as an aircraft electrician, in order to finish my Aerospace engineering degree. (Which is not far from being complete!)
Onto the project!
The albatross UAV project came to me one night while laying in bed (so original isn't it?!). My goal was to provide a high grade, inexpensive UAV platform with unrivaled performance.
My goals?
A standard 4-6kg+ MTOW
Plenty of room for sensors, batteries, and equipment
Easy 1 hour flight times, and up to 4 hours (which is the goal... of course we can't be sure to initial flight tests)
Breakdown, and transportation ease!
Wide flight envelope
Sexy and appealing looks
Last but certainly not least, EFFICIENCY!
Airframe introduction.
The wing: The wing will have a wingspan of 3000mm, and wing area of 68.38dm^2 (in other words, 118" span, and 1060in^2). It consist of an optimized foil, and a forward swept planform. The foil is designed to ensure low stall speed, while maintaining a high max efficiency, and large cruise window. The wing planform Utilizes this foil nicely. It is a relatively high aspect wing with a ratio of 13.2. I have found that this moderate aspect ratio is preferred at RC Reynolds numbers for numerous reasons. an Aspect ratio of 12-15 allows for easier, and stronger wing structure, it allows for slightly higher Reynolds numbers, allowing airfoil's to work properly, over a wider speed range, and allows for easier built in retract, and or component bays. Obviously, we want to achieve all of the above, with minimal impact on performance. Of course a Higher AR wing would be more efficient, but at a significant cost (both in actual price, and giving up benefits.) The wing will be built with built in component bays, allowing for RC rx install in one wing, and Vtx install in the other. Not only does this allow for more room in the aircraft, but it allows for proper separation between Vtx and RC rx. The wing is forward swept, which helps minimize the chance of tip stalling while on approach with your UAV, which may as we all know, be overloaded. (there is nothing as horrible as losing your beloved UAV platform and equipment!). The downturned style tips aren't just for sex appeal, they actually reduce drag and tip vorticites, as well as decrease stall, while improving stability!
The Fuselage: The fuselage is designed around the user. It is designed to have plenty of usable storage space. Whats this mean? Well why would you have a tall narrow fuse? This not only makes is a huge PITA to work in, yet it limits how YOU want to lay out your components! The fuselage is approximately 740mm long, 150mm deep and 200mm wide. To avoid excessive fuselage/wing intersection drag and interference the fuselage is built in a slight trapezoidal shape, only to an extent that wouldn't hinder storage capacity to much. This translates into a fuselage with more usable space than the popular SkyHunter. I haven't mentioned efficiency yet. Lets not forget about that! The fuselage is actually a very efficient shape, minimizing the drag left behind. (even though it will only get chewed up by a prop...). It is also efficient in cooling. It will be designed with a NACA duct in the nose, which is a high pressure region. It will consist of an exhaust right above the motor, which is the lowest pressure region. think suck and blow. While creating a pressure differential it actually pulls air through the airframe keeping necessary components nice and cool.
Tail/s: The tail is an Inverted V design. Why? Simple really, an Inverted V improves efficiency while decreasing drag. It is also naturally more stable in a banked, and coordinated turn. The Inverted V allows for twin tail boom design, allowing for a large diameter prop. It also raises the ground clearance of the tail on landing and takeoff.
Breakdown and transportation: The number 1 reason for keeping airframes small is due to transportation and storage. The Albatross is designed to fit into a box no larger than .35m X .5m X 1m. In reality the case could be much smaller. How does it do this? The fuselage is 740mm X 200mm X 150mm, needless to say, it was designed within the required specifications. The wing is 3m long! However, it simply breaks into 3 1m long sections. The twin carbon-fiber tailbooms are 700mm each. The tail will be hinged at the center, and consist of two 440mm halves, allowing it to fold into one 440mm piece. Not only does this make it easy for the end user, but it reduce's shipping costs to your door. No more paying as much as 50% of your aircraft on shipping alone!
Goals:
My Short Term goal is to finish analysis and development. I am planning on starting a kickstarter to fund the initial molds and production costs. The current Design consists of a fiberglass fuselage, twin carbon fiber booms, and either a foam core/obeche covered wing, or an all built up wood wing. It will come with optional fuselage formers/inserts. These will be laser cut, allowing the builder the option of using them or not. These peices will consist of a retract mount (offset similar to an A-10c aircraft nose wheel, to allow for minimal effect on usable space) as well as numerous mounts and shalves for components and or batteries. Of course, as mentioned this will be up to the customer whether or not he/she will choose to install them. It also allows for some open source design in case anyone wants to improved upon, or create their own after market laser cut parts. This airframe would be available at a goal price of around $500 usd. This may or may not be achieved, but it is my GOAL. I consider this a reasonable goal considering similar aircraft such as Hobbykings UAV-3000 are capable of being produced around $300. I hope that my few added features are not enough to out-reach my goal.
Specs:
Albatross:
Wingspan; 3000mm
Wing Area; 68.38 dm^2
Root Chord; 300mm
Tip Chord; 160mm
Fuse Length; 740mm
Fuse (max) Width; 190mm
My Long Term Goal is a Albatross Pro version. The Albatross Pro will have a slightly enlarged fuselage, more wing area, higher MTOW, change in airfoil, fully molded wings and tail, and more precise construction. These changes would increase MTOW, and cruise speed/efficiency to a more specified range. It would also consist of a few ease of operation features such as built in Cannon-plug style connections for easy quick-disconnect assembly. This means that when you take off the wing, there is no servo connection to fumble with. It would also consist of some ease of assembly mods such as quick disconnect wings, booms, and tail, requiring no tools to use. (Think, Crutch/cane style push button. This would be located under the flaps.)
Specs:
Albatross Pro:
Wingspan; 3000mm
Wing Area; 75.216 dm^2
Root Chord; 330mm
Tip Chord; 185mm
Fuse Length; 890mm
Fuse (max) Width; 230mm
Here is a more in-depth design log on my RCG account. The wing planform, and laminar foil research was originally from a previous project, before I realized its potential in FPV/UAV. Although the introduction of my UAV/FPV platform is fairly new, a lot (many years worth) of prior personally research has been incorporated.
I am currently in communication with a few different OEM manufacturers for an initial Hobby version, and a long term Pro Version. If you know of, or you are another OEM manufacturer feel free to contact me! It would be much appreciated!
Please, feel free to comment, discuss, and provide constructive criticism! After all, this is my first post on DIY Drones, so please be nice!
Comments
A fuel cell would be a nice alternative to LiPos or LiIons. The AEROPAK delivers 200W for many hours, which would be just fine for the Albatross. It has the dimensions of ca. 320x130x120mm. Will an AEROPAK fit in the fuselage having the variable weight (fuel) underneath the wing?
In the WanderB that concept works just fine. Note that the WanderB has a split v-tail. The UMARS changed to that design as well. The reason is to avoid conflicts with the landing parachute. With no parachute a standard inverted v-tail like the Albatross has is still preferred.
However, I do not think the empty weight will be over 4kg... The OEM estimates in the 3400g range or less...
Keep in mind, the UAV 3000 has an AUW of 3400 with a (theoretically) heavier build style.
FWIW, if I shell the whole airframe model at 1.5mm thickness, this puts the airframe CoG at 100mm rearward of the proposed rearmost CoG position. At an average density of 2500g/L, this makes 7.5kg of airframe already
Of course there are a lot of influencing factors between that quick'n'dirty calc and a completed airframe...
The prop moving rearward would of course benefit, however it is already much further rearward than some airframes. Without drastically increasing the fuselage size, it won't go too much further rearward. Keep in mind that this also makes it heavier as it requires more weight to reach CG. Meaning at a point the space under CG won't be utilized anyways. (of course depending on payload.)
This is the profile with Justin's proposed/analysed most rearward CoG point. It's certainly possible to move the fuselage rearward, from a CAD perspective. I might try this over the weekend if I get a chance and see what it looks like. Moving the propeller away from the trailing edge would be a good additional benefit.
Andrew
Directly under the CG there is 180mm tapering to 140mm width of usable space. This is approximately 120-110mm in depth.
This is enough for 14A of 4s. This weight doesn't counter motor, or any other tail weight yet. With the additional weight of autopilot, reciever, transmitter, etc in the wing or under CG, this leaves nothing but camera and more batteries forward of the CG in the fuse.
Wonderful CAD models!
I must mention again, that for an UAV it is important to have as much payload volume as possible near the CG. That is where you place all variable and heavy equipment. To me your model still looks like having a lot more volume in front instead of underneath the wing. I warmly recommend to sacrifice some aerodynamics (and maybe also elegance) and let the fuselage be wider underneath the wing.
As you may know the kickstarter will be in two parts. First I will start a kickstarter for the prototype. This will provide the means of testing a prototype as accurately as possible. Then I will start the campaign for the actual airframe. This method, although unconventional, is actually less expensive. This is because it will be a prototype from the manufacturer, and they can reuse some of the molds for production. It essentially takes about $4k off the total start up price.
Stay tuned, the prototype KS was scheduled to start today, and if it doesn't then it will start this week for sure.
hi Justin I'm loving the updates of this bird its looking very very nice. do you know when your kick starter is going to be live or is it already live and I've missed the link