28 replies to this topic

[boltsniper]

So guns aren`t the only I`m into. R/C aircraft (and cars) are probably my biggest hobby. Lately I have been working on a micro sized R/C plane.



The plane has a wing span of 10 inches and is about 7 inches long. I designed and built it from scratch manufacturing the frame in with the rapid prototyper. One of my research topics is micro sized propulsion for production MAV's. I have been doing a lot of work on small scale ducted fans and jet engines. This plane uses 2 1" DIA ducted fans for thrust. The fans are driven by 36000 RPM 7mm motors and run off of 7 volts. The fans are of my design and use an airfoil I designed myself. They are produced i the rapid prototyper on the high resolution mode which reproduces the balde airfoil quite well. Each engine produces about 12 grams of thrust making total thrust about 24 grams. The gross weight of the aircraft is about 68 grams giving is a power to weight of about 1:3 which isn`t bad at all. The gross weight came out a little higher than I was hoping, so the wing loading is quite high. The gull wing configuration has a few advantage. By canting the bend line inward you obtain a downward angle of attack on the outer portion of the wing cancelling out the natural pitching moment of a flying wing. This means the pitching moment does not need to be trimmed out with the flight controls resulting in less trim drag. The drooped tips also provide directional stability when the aircraft experiences a sideslip.

There's a mess of crap nobody is probably interested in....

I finished the plane this afternoon and had the maiden flight soon after. It flies well but is ridiculously fast. A result of the high wing loading. It is very stable and comfortable to control but it takes a lot of space as it covers ground very quickly. It takes quite a bit of concentration to fly because it is so small and can get so far away from you that you really have to pay attention to its orientation. It didn`t even occur to me to get a vieo of it flying but the next time I take it out I`ll get my wife to shoot some video of it zipping around.

Here are just some pictures of the CAD model, frame and finished plane


















This probably won`t peak much interest except to those that are into R/C aircraft, but I figured I would share some non-nerf stuff as well

[GeneralPrimevil]

I...want...those...fans. Only maybe scaled up by 250% since a plane that small/light is not practical where I live. Damn, I want rapid prototyping technology now.

I'm not majorly into R/C airplanes, but I was tossing some stuff into the air a few years ago. One of my friends, however, is major into the larger stuff, as in, wingspans over 36". He aslo uses nitro stuff more than electric. Right now his fastest plane uses a 110cc engine with a 9" prop, capable of over 90mph. It's a bitch to fly, however. There has to be very little wind, which makes take-offs/landing difficult yet flying easy.

Overall nicely designed plane. It makes me want to dig out all of those dimensioned drawings I have someplace...

Edited by GeneralPrimevil, 05 April 2006 - 11:55 PM.

[Pineapple]

So....is that microfilm, Lexan™, Monokote, or Saran Wrap covering?

And the controls...I'm assuming elevon? (aileron + elevator control to execute turns)

And the whole thing, including the frame, on the rapid prototyper?

(we need a sobbing smiley). I can't stand it! You engineer types!

Seriously, beautiful work, Bolt. The size of the gear...the servos...enough dihedral to save the plane from all but the worst of flying attitudes. It's so reminiscient of some paper airplane designs I played with as a kid. But yours flies FAST!

The smallest thing I have that supposed to fly is a Kyosho 177 Cardinal. The motor pod is probably bigger than your whole plane.


-Piney-

[PissBacon]

I've got a couple questions. Is the entire ducted fan setup also part of the rapid prototyping product, or was that made/bought and added on? And less importantly, what does MAV mean in this context?

[boltsniper]

The covering is is Reynolds teal covered saran wrap. Good guess! The underside is actually jsut covered with crystal clear packing tape. Since the tape is self adhesive it si easy to pull off to adjust and what not.

Yes. Elevon mixing and throttle. The receiver is actually 4 channel but I don`t have a rudder so it's not used. Just standard 1:1 mixing on this one. On the last plane I built I ended up with an interesting unsymmetrical mixing between elevator, ailerons, and rudder. But since the plane wasn`t symmetrical then that wasn`t too surprising. You may have seen this one before:





The control surfaces on the oblique wing were offset on the wing to counter the roll-yaw coupling nature of the oblique wing. It works well. Plenty more pictures of that plane here

Yes, the whole thing was built with SLA. The engine shrouds are integral parts of the frame. The plane was built in 2 halves and bonded together. The only that is not plastic is the control surfaces which are just balsa stock. The geometry is so complex because of the gull shape, the engine ducts, and the varying airfoil across the span that it would be near impossible to build with conventional methods from balsa. At least impossible to build it as precise and light as RP can.

The only thing I bought was the radio and motors for the fans. Everything was designed and built in house. I have yet to see any ducted fans this size on the market even though they perform extremely well.

I have built quite a few ducted fans. The first one I built was 3/4" DIA and made about 7 grams of thrust. I have built them of various sizes up to about 1.7" and with multiple fan stages. Our latest versions are experimenting with convective heating to accelerate the outflow. Quite fun to play with.

MAV stands for Micro Aerial Vehicle

Edited by boltsniper, 06 April 2006 - 12:15 AM.

[NinjZ]

You should sell some mini r/c planes on ebay. You can probably get a decent amount of money for them.

How long can they stay in the air untill the batteries die?

[Black Wrath]

Looks fucking hot.

Good job on the design of the body, it's slick and even looks fast!

[boltsniper]

It will fly about 10 minutes on a charge. It uses a two-cell lithium polymer battery. The battery only weighs 7 grams.

[z80]

Maybe you could slap a SSPB on one off those suckers!
Nice job, looks pretty cool.Maybe on one of your planes you could attach a camera and use it for recon.

[J cobbers]

Both your planes look pretty cool. I'm sure I've seen MAV's on the discovery or learning channel before. My real questions are 1) how well does the oblique wing fly? 2) Is there any special reason for using an oblique wing other than testing the idea?
and 3) Would a full scale oblique be a practical aircraft?

[GeneralPrimevil]

Hey bolt, I hope you don't mind if I try number three...

Northrop-Grumman made one awhile ago. Pretty much, there's had a wing which swept into the oblique position during high-speed flight. The advantages of this are (if I'm not mistaken) lower drag which results in less fuel usage or more speed with the same fuel usage. There are some others as well, but that's the only one I can remember.

I guess I inadvertently did number two as well. Na ja. I think that you (bolt) should either completely discredit my answer or tell me if I'm right...that would be nice...

[boltsniper]

You're not too far off. The plane you are talking about was developed at Ames Dryden to test the oblique wing concept. The oblique was looked at in the first place because it was indicated that an oblique wing would have lower drag and better overall aerodynamic performace at supersonic speeds than a conventional wing. This is mainly due to the drag caused by shock over the wing and the cross shock along a swept wing. The AD-1 had a variable speed oblique wing. It took off and landed with the wing at 0 sweep then could pivot the wing in flight. This has the exact same effect as variable sweep wing planes like the F-14. Having the fuselage there posed some interesting flight characteristics as the wing was swept. The lift from each side of the aircraft became unsymmetrical and caused some interesting yaw-roll coupling. there is the same issue with the flying wing but it is not as predominant because there is no fuselage.

People had invinsioned a large supersonic oblique flying wing civil transport to replace the concord. The efficiency would give it great fuel economy and the flying wing would allow for a large passenger capacity inside the wing.

The model flies quite well. The controls are setup so that you fly it just like a conventional aircraft. Takeoffs and landings are a bit tricky but that is jsut because it is really easy to drag the aft swept tip.

Edited by boltsniper, 06 April 2006 - 09:59 PM.

[GeneralPrimevil]

I read about a Northrop one on a website a long time ago (a year?), so I coulda sworn it was them...there way a Dryden one in the early 80s which was designed by a German-American team, was it not?

So what else do you have planned for aircraft?

[boltsniper]

For some reason I thought you were talking about the AD-1. Yeah, you're right N/G is developing a supersonic OFW. Not slated to flight for another 5 years or so. I don`t remember what the mission was gonna be...

No real plans right now. Kind of hooked on his whole micro thing right now.

[taita cakes]

Great work again mate, you're still my idol. These have always been an expensive fantasy to me. My brother built RC Hovercraft in his spare time.

How much can the batteries be had for? On eBay?

Also, I'm going to have to harass you for help with my next electronics project

[boltsniper]

A hovercraft? Kickass! I had a POS store bought RC hovercraft when I was like 8 or so. It sucked something awful. Not enough power to get it hovering and still not enough to move it around.

The batteries are lithium polymer. They are 3.6V per cell same as lithium ion. They are extremly light and quite small for the current capacity. I picked em up from Powerstream.com. They run between $10 and $30 a cell. You can get them on enay as well. They can be bought in premade packs.

I`d be glad to help you out the best I can.

[CaptainSlug]

I haven't been into aviation in quite a while but this is extremely impressive. Small aircraft are so difficult to get "right".
I never really got into R/C flying (because I'm cheap) but I did spend several years making aircraft for flight sims. Because of that I'm familiar with the math and the mechanics of flight, but I never made anything that flies outside of a computer.

Edited by CaptainSlug, 09 April 2006 - 10:59 AM.

[Pineapple]

A-ha! That is you...the Captain Slug!

I still have some of your FS aircraft designs from FS2k, I think.

A quick check of my zipped files shows my most recent download (last year) was an OV-10 Bronco in California Forestry livery for FS98 (adapted for FS2k).

We're already running FS9, and plan on keeping with it even with the new version FS10 being released either this year or next.

I'm involved in Transload Virtual Airlines...well, I was until my FS comp blew it's power supply. So, I'm inactive right now.

Good to see you here, now.


-Piney-

[SofaKing]

A hovercraft?  Kickass!  I had a POS store bought RC hovercraft when I was like 8 or so.  It sucked something awful.  Not enough power to get it hovering and still not enough to move it around.

I just got my X-UFO Saturday ,It's a pain to set up the trim pots,so it's not quite stable enough to fly for long indoors,and outside its mostly been raining or too windy too get any real success,but it looks to be all they claim.I'll give you an update when I get some more air time.

[CaptainSlug]

A-ha!  That is you...the Captain Slug!

Yeah, I'm all over the place. It's hard to believe I've been using this pseudonym for more than 10 years and that I started making Flight Sim Aircraft when I was 12. I haven't kept up with flight simulation since FS2k4 went to Alpha.

Edited by CaptainSlug, 09 April 2006 - 11:10 PM.

[boltsniper]

I remember designing aircraft for FS4. That's version 4 from around 1990. Then I remeber designing aircraft from scratch with BAO Flight Shop for FS5/95 around 1994 or so. Since then I have maintained the current version of FS but haven`t done much designing of custom aircraft.

[Dan Wask]

anyone wanna direct me to a good rc car forum ? I need some help setting up the suspention on my team associated t3 that I just lowered

[Scavenger]

How well did the hovercraft work? I'm building one now, all I need to do is finish up the propulsion, the lift works. I still need to get it balanced, though, the front creates some drag. And boltsniper, how much did the battery cost? The plane looks sweet.

[boltsniper]

I paid about $8/cell for 6 cells a while back.

Waskie, what kind of surface are you planning on running on? I have a fair amount of experience setting up my HPI's for asphalt tracks and some carpet tracks.

[Dan Wask]

Mostly asphalt, some really smooth concrete.