Why have military UAV's not caught on in the hobby world?

[ninja21m]

I am a fan of the predator drone shown below, and was just curious from a hobby modelers’ point of view why this airframe style has not taken on as the choice airframe for personal UAV projects. You would think that it the military has found it to work best, hobbie’rs would to.

Any thoughts? PLEASE !!

[kd7ost]

Because there aren't decent sized scale models available. You have to make your own. It's not the easiest design to scratch build. Even the Landing gear would have to be custom made. That's probably the only reason. I like the predator style and can see the benefits of the design.

Dan

[Dan_Jones]

http://www.rcgroups.com/forums/showthread.php?t=552246

I got mine from www.raidentech.com. It is a nice model and I am also surprised that I don't see more of it around. It does need quite a bit more runway that all of my other models. That is why I don't fly it very often.

(edited to insert the correct link instead of a link to this forum... :)

[kd7ost]

I've seen that and thanks for posting the link here. I've never gone after that one due to size. It simply lacks the volume needed for very much UAV effort in my applications. It was designed as a small scale model.

Dan

[typicalaimster]

I know LittleBirdz (http://www.littlebirdz.com/products.php?cat=34&PHPSESSID=887eed9a96a03ec20a3915bed374e428) sells a balsa version of the plane.

[ninja21m]

My friend and I bought the raiden tech electric model and have been generally unimpressed with the plane. It seems somewhat underpowered even with a 450 brushless motor, and we haven’t even attempted to add any AP hardware or autopilot equipment. I am in the process of designing a 1/4 scale model of the Predator which will sport a 45CC gas motor. This should have the space needed to fulfill all the UAV dreams I might have.

[danstrider]

I agree with Dan.

I bought one of the Littlebirdz Predators when it first came out thinking a UAV as a camera ship would be the best thing since sliced cheese. The problem was, I couldn't put anything inside it, and it was cramped at best. The little Aiptek fits, but has since been superceeded by much nicer cameras that won't go back in the little Aiptek pocket. For half the amount of money, a Slow Stick can carry 5x the cargo and is upgradable. Also, the Predator is essentially a sailplane, and as such, it flies like one. No low slow turns or tight spirals to fit into small landing zones. And, the Littlebirdz version won't fly for hours on end without control input like a Saggita or Bird of Time, so it didn't even earn a good sailplane star in my book.

Now I do like the Pioneer style aircraft, a lot like what Dan was going after. It is robust and has the cargo space and is easy to fly like a trainer. FWIW though, something like the 12ft Telemaster or 8ft Telemaster widened 50% make a super awesome "truck" for carrying payloads and you don't have to fuss about the building. The UAV airframe is only 10% of the work anyhow; out of the rest, maybe 10% is hardware and a solid 80% is software. I like a vehicle only as complicated as the task. Aerosonde was built to fly long-endurance missions and needed a clean-ish airframe with a super engine. In that case, I think the vehicle warrented more effort than a usual UAV. However, Maynard Hill's *model* aircraft that flew across the Atlantic was amazingly not clean. It was pretty much a box with chunky wings, search for pics.

I dunno, I guess I'll get off my soap box. Something hit a nerve I guess ;-)

My whole point is, I really like the look of the Predator, but it doesn't make a fun model to fly around. The airframe is nothing more than a "truck" to carry around payload unless there is a very airframe dependent mission.

Dan

[ninja21m]

I agree with Dan.

I bought one of the Littlebirdz Predators when it first came out thinking a UAV as a camera ship would be the best thing since sliced cheese. The problem was, I couldn't put anything inside it, and it was cramped at best. The little Aiptek fits, but has since been superceeded by much nicer cameras that won't go back in the little Aiptek pocket. For half the amount of money, a Slow Stick can carry 5x the cargo and is upgradable. Also, the Predator is essentially a sailplane, and as such, it flies like one. No low slow turns or tight spirals to fit into small landing zones. And, the Littlebirdz version won't fly for hours on end without control input like a Saggita or Bird of Time, so it didn't even earn a good sailplane star in my book.

Now I do like the Pioneer style aircraft, a lot like what Dan was going after. It is robust and has the cargo space and is easy to fly like a trainer. FWIW though, something like the 12ft Telemaster or 8ft Telemaster widened 50% make a super awesome "truck" for carrying payloads and you don't have to fuss about the building. The UAV airframe is only 10% of the work anyhow; out of the rest, maybe 10% is hardware and a solid 80% is software. I like a vehicle only as complicated as the task. Aerosonde was built to fly long-endurance missions and needed a clean-ish airframe with a super engine. In that case, I think the vehicle warrented more effort than a usual UAV. However, Maynard Hill's *model* aircraft that flew across the Atlantic was amazingly not clean. It was pretty much a box with chunky wings, search for pics.

I dunno, I guess I'll get off my soap box. Something hit a nerve I guess ;-)

My whole point is, I really like the look of the Predator, but it doesn't make a fun model to fly around. The airframe is nothing more than a "truck" to carry around payload unless there is a very airframe dependent mission.

Dan



Dan I enjoyed reading your comments on the predator. In my design I will probably make slight design mods to the wing to make it slightly more agile, but the sailplane type wing allows for a longer flight as it does not need constant high power to keep it's altitude. I guess I am just stuck on the way it looks, building a big stick or telemaster while the airframe has been proven over and over and over and over again, is still a big trainer airplane, I will stick with a big predator with mods and keep u guys posted of the details.

Ninja

[Tom Harper]

Ninja,

The Predator is a huge airplane with a composite laminar flow wing. It won't scale well. Consider that the smaller Israeli drones look a lot like Dan's twin boom. That's for lot of the reasons covered by Danstrider.

Let's say you scale it to twelve square feet:

................Predator.................Model

Area...........123 sq ft...............12 sq ft
Span........... 59 ft...................15.2 ft
Weight........1500 lbs................4.5 lbs
Power......... 101 HP.................1.7 HP.....1283 Watts
Wing Loading 30 lbs per sq ft......6 oz/sq ft
Cruise......... 147 FPS................102 FPS

The Predator's 30 pounds per sq ft scales to 6oz per sq ft on a 15 ft span model. The laminar wing at 147FPS has a good Reynolds number. It is a very HOT airplane. Tough to do with a model. But if you can make that weight and power, it would be awesome. You may need twice the power to compensate for the Reynolds number and non-laminar wing.

Keep us informed.

Tom

[kd7ost]

I think a Predator type design would typically need longer runways. I’m not suggesting that’s a problem. But I take off and land on rural roads quite a bit with my 20 pounder. To get into short area’s you need to pitch the nose up pretty high at times to bleed off the speed and get set down. A mid engine/motor design protects the prop because it’s just behind the mains. I’ve dragged my tail before and have wing tip skids on the rear underside of my tail booms for that. Of course I don’t have flaps so there are other issues not explored.

The predator design has to have pretty tall gear to compensate for rotation on take off and landing. Longer gear gives a longer leverage arm and can do internal damage to the former or bulkhead taking the stress of the landings. I couldn’t yet figure in my head what I wanted to do with home made landing gear for a 15 to 20 pound plane. Outside of that, I think the in flight efficiency would be great. Nice clean lines. In the AP arena though I find having some dirty draggy lines can be helpful at times. It depends on the mission and endurance requirements. My smaller 6 pound Dragonfly uses a set of glider wings and that thing just doesn’t slow down like I would prefer.

I like the handling of the mid engine designs. You can roll, pitch and yaw with small control surfaces that don’t deflect a lot. That saves servos and power because the servos don’t have to work very hard to get their task done. The prop is protected and behind your camera equipment too.

Tom's Creosote Cruiser takes advantage of the same concepts.

Dan

[MGBGTRacer]

Just don't bother with the Draganfly Predator- worst plane, ever.

[RaptorAP]

"Truck"- I like that description, most know my designs look like dump trucks!:D:D

[workshop]

DanS. Wrote: "FWIW though, something like the 12ft Telemaster or 8ft Telemaster widened 50% make a super awesome "truck" for carrying payloads and you don't have to fuss about the building."

Although it took awhile to trim the thrust angle, this Telemaster flies great an carries a few pounds of TTL junk:

http://www.rcgroups.com/forums/showthread.php?t=631757

My last 20 minute flight averaged 15mph which is 5mph BELOW the calculated stall speed. The airframe(s) is so cheap it's a throwaway. The interior space is huge and there is room to undersling gear (TXs, Camerals, etc.).

If I had it to do over, I'd pick the Senior TM because Hobby Lobby's "electric conversion" of the TM Electro simply consists of an ill place lite-ply battery box and a motor mount that ends up getting removed anyway. Plus, and get this, the "Hobby Lobby" decals DON'T come off! That's a reason right there not to buy the Electro (too mcuh work to recover although I am very pleased with the new look).

Jeff

[ninja21m]

Ninja,

The Predator is a huge airplane with a composite laminar flow wing. It won't scale well. Consider that the smaller Israeli drones look a lot like Dan's twin boom. That's for lot of the reasons covered by Danstrider.

Let's say you scale it to twelve square feet:

................Predator.................Model

Area...........123 sq ft...............12 sq ft
Span........... 59 ft...................15.2 ft
Weight........1500 lbs................4.5 lbs
Power......... 101 HP.................1.7 HP.....1283 Watts
Wing Loading 30 lbs per sq ft......6 oz/sq ft
Cruise......... 147 FPS................102 FPS

The Predator's 30 pounds per sq ft scales to 6oz per sq ft on a 15 ft span model. The laminar wing at 147FPS has a good Reynolds number. It is a very HOT airplane. Tough to do with a model. But if you can make that weight and power, it would be awesome. You may need twice the power to compensate for the Reynolds number and non-laminar wing.

Keep us informed.

Tom


Tom

Thank you for the eye opening information as per the downfalls of the scalling down of the odel. I am making adjust the desing to take come of the negitives away. What program did you use to get the the info that you displaed? Namely the Renynolds nuber and such. and how do I run this same test, as it would be awesome to find a program that can do this sort of thing for you.

James

[Tom Harper]

James,

I just use a spread sheet. Many years ago NACA published the scaling ratios they used for testing scale models. I have found them to be extremely useful.

I'll post the ratios here when I get time. If you give me your email address on a PM I will set up an Excel file that you can use.

Tom

[thomasscherrer]

deleted

[Capt. Crunch]

BTW, the Preditor and Global Hawk are designed with the big nose bubble to house the Satallite Antenna, otherwise they'd be a normal front end.

Their glider like wings are to reduce fuel consumption/enable longer range or loiter, at the expense of handling and high cost of fabrication.

You're right about the Telemaster being an appropriate "Truck" for hauling our camera & navigation gear around. In our application short take off & landing, excellent stability, and easy/forgiving handling are of the highest priority. If you're trying to take pictures, you don't want to be having to fly the plane with full concentration.

I'm currently using a GWS Foamie Beaver for a platform to test alll my systems. The goal is to get a fully atonomus system that will take a 4 Meter glider over some mountains. While things are being sorted out a nice stable, hands off platform is very helpfull. Eventually I plan on building a plane similar to the Beaver at about 130% size and Fiber Glass construction and use it for a general purpose camera plane. The Telemasters are very similar and like noted above, almost disposable thery're so cheap compared to the rest of the equipment. they also hae excellent handling and easy to repair in the field.

I love the Predator look too, and may do one as a scale project some day. About a 2.5 to 3.5 meter span should carry enought gear to make it work out. Just one more project to forward too.

Chrunchy