ScanEagle UAV Project [Archive]

lphan

Aug 04, 2006, 11:02 AM

Kip,

Wow !! Thanks for responding !! I think your guys UAV beats all of those UAVs on the market today. It's simple yet unique, especially the sky hook. Who would of thought of using a Tarzan method for stopping a plane? Very ingenious !! You guys should consider a name change to Ingenious-situ ;) Now enough flattery...

We just had our R/C group meeting last night. They were asking if I was going to add the sky hook or not. I would love to, but I think for this version, I'll just keep it out. Beside, we don't have a crane available at the flying field. I may be able to use a tree branch some day (but it's behind our flight line). The Mini-me ScanEagle will definitely have a camera/video in the nose though.

By the way, my design has 4 degrees of downwash on the wing tips. Someone at the meeting suggested I do 8 degrees of downwash. So I just got finshed uodating it to a 8 degree downwash. If I may, what is the dowanwash on the real ScanEagle?

It's hard to find reliable data on the Scaneagle from the web. Mine is 1/2 scale to yours.

Fuselage: 3.5" dia
Wing Span: 60"
Length : 27"
Wing Area: 300 sq in
Wing angle of sweep: 25 degrees
Airfoil: Semi-Semetrical 13.75% wing, 5" chord

I plan it to be using a brushless motor (Mega 16/15/5 with a 6x3 foldable prop) on 2 sets of 3 cell 1200 lipos.

The target flying weight is 25 oz giving a wing loading of 12 oz/sq ft

Looking forward to your response.

Cheers,

Le

P.S. the fuselage formers and stringers have been installed. Next step is to sheet the fuse with 1/32" balsa.

lphan

Aug 04, 2006, 04:45 PM

Gang,

This is my best construction design yet. I decided to use an aluminum 1" square tube as my construction crutch. There are several advantages.

1. It' s pretty straight crutch.
2. I can align the formers more accurately. I draw lines on the aluminum for the former locations with a square all around the perimeter of the tube using a fblack ine permanent marker. This helps me align the formers to be square in all three directions.
3. I can rotate my construction crutch about the fuselage axis to get to the bottom of the fuse.

Here's the progress so far.

Cheers,

Le

kd7ost

Aug 05, 2006, 01:18 AM

RCAV8R13

Aug 05, 2006, 01:47 AM

Iphan,
Incredible work! Outstanding.
PMed you.
Kip

RCAV8R13

Aug 05, 2006, 02:01 AM

Very nice progress Iphan. It always does me good to see builders work in wood. ;)

Kip,

There appears to be rudders on the vertical tail fins on your unit. Is that the case or is that just a line for looks? How are they employed if they are there and how does it make the flight direction change if any?

Thanks

Dan
Yes it does have rudders. It needs them, sort of. When I set it up and flew it as an R/C plane, I found that I needed lots of rudder with aileron because it had no differential aileron (you're not suposed to use it on flying wings). The adverse yaw was very strong and it would "Dutch roll" when comming out of turns. So, I put in some differential ailreon and it flew like a pattern plane, sweet. When we put the autopilot in I lost the differential (couldn't convince the boss to put it in). So, I programmed in aileron to rudder mixing on the "pilot's console" (TX linked to a box with a cord). That worked just fine. I couldn't use differential on the console because all the mixing is done in software on board the plane.
With that said, If you use a little differential in your ailerons you shouldn't need rudders but they do help a lot if your trying to put it on the hook in a crosswind.
Kip

lphan

Aug 05, 2006, 07:50 AM

Dan,

Thanks for the compliment. I love building with Balsa. I get a light and sturdy plane every time !

Kip,

Great info on the rudders on a flying wing. I didn't know about "but they do help a lot if your trying to put it on the hook in a crosswind." It looks like I have plenty of sweep and washout on the wings. I'll go ahead with what I have. I had to add some stiffeners to the wing mount location last night. I'll be sure to have some former location changes on the next version.

Cheers,

Le

P.S. I plan to be flying the Mini-SE next Saturday, August 12th at my club's fun fly. So, keep and eye or two out on this thread, there'll be lots of progress pics this week.

3Deranged

Aug 06, 2006, 05:18 PM

Outstanding work on your UAV! I was noticing the launcher in the photo's. How are you launching your UAV, handlaunch or bungee? I tore my rotator cuff and had to come up with a launch system for my T-33, so I whipped this up out of garage scraps. I'm sure it could be adapted for different vehicles and it's simple and compact. My 2 cents. Someone else had adapted the launcher for use with bungee hooks too. When it's dialed in for your model it will produce consistent launches time after time.

lphan

Aug 07, 2006, 10:47 PM

Edfrules,

Wow, what a cool catapult ! I planning to hand launch this one. I enjoyed looking at the video!

Gang,

Well I sheeted it enough so that I can get it off the construction tube.

Cheers,

Le

lphan

Aug 09, 2006, 08:00 AM

Now for the wings and fins.

CenTexFlyer

Aug 09, 2006, 08:54 AM

Hey Edfrules...

Is that a PALS? Looks pretty good shortened up. How do you charge the cylinder in the field?

Gene

RCAV8R13

Aug 10, 2006, 11:45 PM

Hey Edfrules...

Is that a PALS? Looks pretty good shortened up. How do you charge the cylinder in the field?

Gene
PALS...hummm, I'll guess:
Pressurized Air Launch System?
Pneumatic Assist Launch System?
Pneumatic Air Launch System?
Am I close?
RCA

lphan

Aug 11, 2006, 07:40 AM

Had some things get in the way of my build schedule. Here's the left wing and fuse.

Chers,

Le

lvspark

Aug 11, 2006, 12:30 PM

Your doing a super job on that. Do you have a dome picked out for the nose??

Unterhausen

Aug 11, 2006, 04:15 PM

That's a really nice job you've done.

the only reservation I have about this thing is the size of the hole on the inside of the fuselage. Not enough room in there, is the plan to cut bigger holes in formers later?

did you get someone to cut the parts for you?

typicalaimster

Aug 11, 2006, 10:02 PM

That's pretty cool

lphan

Aug 11, 2006, 10:31 PM

Thanks for all the compliments gang !!

lvspark

Not yet. I 'm lneed to look for a 3 inch diameter clear plastic bal that I can use.

Unterhausen,

I plan to fit all the equipment between the formers. The 1x1 inch hole served for two purposes, cinstruction, and wire trough. I may need to widen some formers, but we'll see. The formers for the fuse I cut myself. But the 30 Ribs, I had a friend of mine Dan Schwartz cut them ot on his CNC machine. That's why I got the wings done so fast, but not fast enough for tomorrow's fun fly.

Cheers,

Le

LukeZ

Aug 12, 2006, 02:50 AM

Le, do you mind me asking what CAD program you did this in? You've done a really great job designing the plane.

Luke

libelulamodelos

Aug 12, 2006, 11:15 AM

hey great job, i wanto to build a scan eagle too, do you have digital plans??

RCAV8R13

Aug 12, 2006, 02:10 PM

Looking goood!
I thought I would share some ScanEagle pix with you guys. These are from a press release. The thugs in the pictures claim they shot it down from 2,200+ feet. Truth is, it is invisible at that altitude. We lost all coms with it and it crashed on its own, no help from the thugs, they had nothing to do with it.
Kip

3Deranged

Aug 13, 2006, 03:13 AM

You sure they're not Iraqi AMA members discussing range checks? :rolleyes:

lphan

Aug 13, 2006, 08:14 AM

Luke,

I used CATIA V5.

Colombia,

None available yet. I need to write a construction article for a magazine first.

Kip,

Thanks for the pics ! I'd like to see Iraqi ski mask club try to rebuild their newly found ScanEagle and fly it. I'd really like to see that ;)

edfrules,

I second your vote. Range check are important.

Cheers,

Le

sodman12

Aug 13, 2006, 06:21 PM

is this thing gonna fly or is it just for looks? to me it looks a little thick.

RCAV8R13

Aug 13, 2006, 07:17 PM

You sure they're not Iraqi AMA members discussing range checks? :rolleyes:
Who knows what part of "heck" they came from, but it happened in Iraq. They claimed to represent "al queda".
Kip

lphan

Aug 15, 2006, 07:53 AM

Gang,

Just cut the ailerons. Next step is to add the electronics.

Cheers,

Le

lphan

Aug 16, 2006, 08:21 AM

Motor mounts and wing alignment pins.

elossam

Aug 16, 2006, 04:34 PM

Do you think there is enough ventilation for the engine?

lphan

Aug 17, 2006, 08:32 AM

Elossam,

Good question.

I plan to put an air intake on the left side, like the real one in this pictures.

Cheers,

Le

elossam

Aug 17, 2006, 05:34 PM

Good solution, we burnt our first engine placed also in a push configuration due to a poor refreshment. Glad to see you have it in mind. Good luck.

lphan

Aug 18, 2006, 09:06 AM

Next is to recheck the C.G. and determine the battery location.

Cheers,

Le

lphan

Aug 20, 2006, 08:13 AM

Started covering. I found a whoffle ball that matched exactly what I was looking for as the camera housing.

kd7ost

Aug 20, 2006, 12:41 PM

Thats cool. It will sound erie coming at you through the air too. :D

Dan

lphan

Aug 22, 2006, 05:50 AM

I used car trim dark gray for the stickers. It holds well to MonoKote.

Cheers,

Le

sodman12

Aug 22, 2006, 09:45 PM

damn that thing is sweet!
i like the name.
you need to video the test flight

Terry S

Aug 23, 2006, 01:03 PM

How dose it balance ? Looks like it will be nose heavy.

Terry

RCAV8R13

Aug 23, 2006, 11:32 PM

Le,
She's looking great! Have you calculated where the CG should be? If you send me the dimensions (root cord, tip cord, span, sweep (25deg., right?)) I can do the calculations and we can compare. Lets' get it right the first time!
Kip

lphan

Aug 24, 2006, 02:45 PM

Kip,

Thanks for helping me with the CG. Can you verify the calculations for me?

The Red dot is the C.G. location (25% chord). It's a 25 degree wing sweep, constant chord, with 8 degrees washout. Should I be at less than 25 % chord?

If the weather holds up, I should fly her this Saturday. I'll have a video of it too.

Le

RCAV8R13

Aug 24, 2006, 03:49 PM

Le,
Nice drawing, plenty of info. I'll play with it when I get home tonight, but it looks like you got it right. It's funny, the c.g. on the full size is 60mm aft of the root trailing edge at the centerline (3.038/ 77.165mm in your drawing). The difference between the two is the full size has a sweep angle of 23 deg.. That means your c.g. should be farther aft (from the same root trailing edge datum point) than the full size. At 25% of MAC you should be quite stabile.
Kip

vespa

Aug 25, 2006, 04:05 AM

Whoa! You are correct in your calculations of the 1/4 chord at 8.3" but that is NOT the correct c.g. location! What you calculated is the AC and the fundamental rule of aircraft stability is that the c.g. must be forward of the AC, typically by a distance of 10%-20% MAC. For your MAC of 5.25 that would be about 3/4" ahead of the AC (7.5" from root LE).

The reason many planes (with TAILS!) balance at 25% has is because it just happens that a pleasant tail size/location results in a MAC for the entire aircraft at about 40% wing MAC. Add a typical static margin of 15% and the c.g. ends up at the 1/4 chord - for planes with tails! The simple rule is this: The AC of most any shape object is around 25%, the c.g. must be ahead of that, and you must consider the entire aircraft.

Though you don't have a tail, you still must set the c.g. relative to the MAC of the entire aircraft. This means that you also must consider the effects of the fuselage. You could calculate the MAC of the complete planform but since the fuselage is such an inefficient "wing" (low AR and round cross section), you can simply "eyeball" your c.g. forward by another 5% or so. So I'd suggest starting at 7.3".

Cool project b.t.w.! I can't wait for the video of a cable-catch! :)

lphan

Aug 25, 2006, 09:34 AM

Kip,

Remember that the ScanEaglet is 1/2 scale to the Scan Eagle. That would mean that my CG should be half that of 60 mm meaning 30 mm. Now I'm getting nervous.

Vespa,

Thank for your help also !

Here are some progress pics.

I decided to simplify the air intake to having only one at the top of the fuse. I used a night light cover for it :).

I won't be able to fly tomorrow. I forgot about a wedding I needed to go to this evening. I'll have to shoot for Sunday.

Cheers,

Le

vespa

Aug 25, 2006, 02:07 PM

RCAV8R13

Aug 25, 2006, 03:52 PM

Le,
I totally concur with Vespa, 7.3" (7.238") back from the root leading edge intersection will result in a margin of 5%. That should fly well.
Good luck, I look forward to hearing about the flight.
Kip

RCAV8R13

Aug 25, 2006, 04:04 PM

Yes, well scaling the cg location gives you 5.25" + 30mm = 6.4" but you must consider that the full scale version has tapered wings and a large root fairing, both of which move the AC forward significantly.

Hey RCAV8R13: Why were the ap guys reluctant to use aileron differential? Seems to me the differential would give the plane a much more pure aerodynamic behavior, making tuning easier.
Vespa,
It wasn't "guys" buy one guy, the founder of the company. There are two camps on the "differential aileron on a flying wing" issue. The boss felt that differential was a bad idea with the auto pilot because he was going to rely on co-ordinated turns with rudder and with elevons and differential, he was afraid the plane would pitch up with aileron inputs. I'm from the other camp. I was given free rain on how I could set up the R/C prototypes and I used differential with great results. Without differentail I manually co-ordinated my turns with rudder with good results as well, but I felt that I was fighting the problem rather than eliminating it. Differential worked better.
Kip

lphan

Aug 27, 2006, 08:10 PM

Kip and Vespa,

No flying today. Rain in Ann Arbor, and I had no photographer or videographers available.

Thanks for the advice. Please check my claculations, but, wouldn't 7.3" from the root leading edge, make it fly at 4.8% chord?

Please let me know, thanks.

I plan to fly it at 20% chord (8.03" from the root leading edge).

Here are some pic before I fly it. My photographer and videograper won't be free until this Wednesday afternoon !

Here are the numbers:

Wing Span: 60"
Length: 27.5"
Wing Area: 300 sq in.
Flying weight: 27 oz.
Wing loading: 13 oz/sq ft
Motor: Mega Brushless 16/15/5
Batteries: 3 cell 1200 Lipos, two packs in parallel
Prop: Kavan 6x4
Servos: 2 Pico Servos for elevon controls.

Cheers, Wednesday it is.

Le

vespa

Aug 27, 2006, 09:05 PM

Well the AC is at 25% so a cg at 20% leaves a 5% margin. Most planes have a fuselage AC very near the aircraft AC but this design has the fuselage significantly ahead of the AC so this is going to take a few percent from your margin.

At around 3% calculated margin, most designs will start to show divergent behavior. 5% is a typical limit for a well tested and tuned aircraft, 20% is a reasonable starting point for a new design. I might start at 10% if I was quite confident in my Cm calculations, power/weight ratio, and piloting skills, but I assume you are simply guessing the neutral elevon position and have somewhat modest power. It's much better to have a nose-heavy unplanned high-speed landing than a nasty spin right on launch - wings like this tend to have very violent stall behavior so you really want to avoid that!

RCAV8R13

Aug 28, 2006, 09:08 PM

I agree with Vespa, again.
I think you should move the C.G. forward.
Good luck.
Kip

lphan

Aug 29, 2006, 11:23 PM

Kip,

Why is the US Insignia different from the UAV to say the F-18 Hornet?
The one on the ScanEagle looks like one from WWII.

Well, it looks like the weather will be okay for our ScaEaglet maiden flight tomorrow. Ann Arbor will be cloudy 75 degrees. I'll be flying her at 7.75" aft of the root leading edge.

Cheers,

Le

sodman12

Aug 30, 2006, 10:27 AM

Whats different? I cant tell.
Hope that flights going well, cant wait to see video from it.

lphan

Aug 30, 2006, 02:51 PM

sodman12

Here's a WWII plane, F4U Corsair insignia vs modern F-18 Hornet and A-10 Warthog.

There's a stripe missing from both sides of the star. I figure since the ScanEagle is a modern day plane, it should have the same insignia as the F-18 etc...

I plane to fly the ScanEaglet at 5:30 pm today, God willing. It's a little windy today in Ann Arbor.

Le

sodman12

Aug 30, 2006, 04:51 PM

Ahhhh she can handle it. go for it!

sodman12

Aug 30, 2006, 08:28 PM

Wonder how it went?

lphan

Aug 31, 2006, 12:10 AM

Gang,

Vespa was right, I needed more nose weight !!! The weather was choppy 10-12 pmh gusts straight into the field. The first launch showed that it was tail heavy with the CG at 20%. I almost landed it on it's tail, but it settled on the fuse perfectly, thank God ! I ended up adding about 1 ounce of weight on the nose and it flew fine. I still have to measure where the CG ended up. It looks like the fuse nose gave it some lift as well.

I noticed that when I applied full power, it would climb like crazy... But when I backed off to about 25 % it flew slow, but level,and even glide fine.
I noticed it porpoised up and down at certain speeds though, still need to figure that one out. It maybe beacause of my loose servo links. I had plenty of pitch authority though. I need to add more aileron throws for the next flight.

Other than that, it's a very stable platform.

Here's a collage. I have to load up the video on the Video gallery. Hold on...

Cheers,

Le

lphan

Aug 31, 2006, 12:16 AM

The video has been loaded to:

http://www.rcgroups.com/forums/showthread.php?t=563672

typicalaimster

Aug 31, 2006, 01:19 AM

Congratz on the test flight. I'm going to go off on a story here so I do apologize.

I'm not sure if this is your first wing design or not so I'll share some experience. For about 6 months I struggled building a very simple 'F-106 Delta Dart'. In the begining I crashed 2 planes and lost 1 LiPo pack in the process. During the development somehow I accidently designed one that worked. The wing flew like it was on rails. Excited I yanked the equipment out of the blue core test plane and built another one. This process litterly involved cutting things out thus distroying the test plane...

Once again I suffered through 4 months of nothing but crashes. The planes were doing EXACTLY like you describe here. It would porpoise up and down during certain speeds. I trolled through various web pages and forums trying to find the answer. Eventually I gave up. That was until my dad finished his F-106 and drove it into the ground with the exact same symptoms.

With some motivation I decided to google a little deeper into Flying Wing designs. Somehow I ran across this web page (http://adamone.rchomepage.com/index5.htm) and almost blew it off as one of those 101 aerodynamic courses. That was until I scrolled down and read "For a delta wing the CG should be located 10% ahead of the geometrically calculated AC point as shown above". With that information that would move my CG from the 25-30% mark to the 15-20% mark. In my design this was about 3" forward from my original calculated CG. I cut out a quick delta and flew it the next day... Once again the plane flew like it was on rails...

I believe the porpoising you're seeing is from a CG issue. You may want to move some weight forward a bit more to see how it works out. I've found the rule is about 15% on the CG to start with and go from there. This was a big change for me coming from tailed aircraft. I'm sure someone here can explain in depth where your CG should be and why if you wanted to. I'm not a major in aerodynamics so I'm speaking more from field experience.

I've since made about 4 flying wing prototypes over the course of the summer. They're not as elaborate as your Scan Eagle since I was just playing around with a $25 bundle of blue core. In fact I'm still in ahhh with your design... Two of my designs are a swept wing like the Scan Eagle. My avitar is actually one that flew.. Of those two, one of them I moved the rudder from it's 'standard' position to the wing tips just to see what it would do. In that configuration you'll notice the plane will fly just like any other once you have things figured out. If you do a few aerobatics you'll notice some strange things come out of it. It's not really bad things... It's more like I didn't expect it to do that things..

Overall going from Tail to Tailless wing I have a MUCH better understanding of what that tail is doing back there. It's great to hear that you had excellent success with your design. I hope that luck continues and you enjoy many hours of flight with it.

RCAV8R13

Aug 31, 2006, 01:38 AM

Outstanding, congarats!
That was erie watching it fly, it looks so real in the air.
Great job.
Kip
P.S. Where do you work? What do you do for a living?

sodman12

Aug 31, 2006, 01:39 AM

Do you know what the top speed is? it looks like it could really move if given the right engine.

Really nice job on it though.

lphan

Aug 31, 2006, 08:37 AM

Typicalaimster,

Thanks for sharing your experiences. I amdire people who have the charateristics of "Stick-to-it-tiveness" My only experiences with flying wings was with the ZAGIs years ago when they came out with their first glider kits.

Sodman12,

Thanks for the compiments.

Kip,

Thanks, but what's the answer on the U.S. Insignia question I had earlier.

I work at MSC Software, Ann Arbor branch. I'm a Mechanical Engineer working in our marketing group. My job is to create geometry from scratch so we can use for testing our simulation software. We sell the software to engineers so they can use it to simulate say: When a wing on an airplane will fatigue, car crahes in the computer, drop tests, motion studies, etc... Our tag line is: "Simulating Reality." I've attached an image of some of my work.

Cheers,

Le

lphan

Aug 31, 2006, 09:01 AM

Sodman 12,

The video shows it flying at about 25 % throttle. I flew it slow so my camera man (Ken Bates) could take pics of it, as well as my videographer (Dan Schwartz). I need to fix my elevon throws and slop before I try a speed test.

Cheers,

Le

dalbert02

Aug 31, 2006, 12:03 PM

Not sure if this helps you this late in the game, but I picked this up at the unmanned conference in Orlando yesterday, maybe you find it interesting. More pics in the umanned thread here:
http://www.rcgroups.com/forums/showthread.php?t=538447&page=2

-dave

lphan

Aug 31, 2006, 12:35 PM

dalbert02,

I could have used this 30 days ago !!!!
BUT thanks, I can definitely use it !!

Cheers,

Le

lphan

Aug 31, 2006, 12:37 PM

This is really wierd, I have NEVER had a plane where the C.G. is -2% chord.

Take a look below.

Is this normal for flying wings?

Le

Kevin Cox

Aug 31, 2006, 09:14 PM

Awesome work Le!

vespa

Sep 01, 2006, 01:55 AM

Glad to hear the flights were successful! Sorry I was wrong about the c.g. - I never would have guessed a 27% margin but note that this is a valid location even if it does seem physically impossible at first glance.

6 deg is a tremendous amount of twist, but your conventional (Cm<<0) airfoil should balance things out pretty well. The real Scan Eagle uses a highly undercambered airfoil with a very negative pitching moment and a tremendous amount of twist as well so you should be on the right track!

Tighten up those control surfaces and keep us posted!

century_series

Sep 01, 2006, 10:27 AM

This is really wierd, I have NEVER had a plane where the C.G. is -2% chord.

Take a look below.

Is this normal for flying wings?

Le

Hi Le
As Vespa noted, 6 degr twist (washout) is a lot. It effectively reduces your wingtips to a stabilizer with a 6 degr decalage! Where the wing ends and the stabilizer begins is a grey area depending on twist, sweep and taper ratio. If you use the graphical method to find the AC (drawing lines from root coord to tip coord etc) you have to consider excluding some wingtip area. Think of it as chopping of the wingtips.

Regards
Patrik

Oh, btw. Outstanding work!!! Following this with great interest

lphan

Sep 01, 2006, 04:01 PM

Patrik,

Thank you for the compliments.

You are right. I didn't think about that. It makes sense now why the CG is so far forward. The washout is actually 8 degrees !!

Gang,

The servo horn slop had been fixed. I also modified the elevons so that I have more down travel. The plane weighs 28 oz now. The nose which is carrying ballast weight is 2.8 oz. I think the weight of the video camear is about 2-3 oz. I'll have to chack.

Have a great weekend !!

Cheers,

Le

typicalaimster

Sep 01, 2006, 04:25 PM

This is really wierd, I have NEVER had a plane where the C.G. is -2% chord.

Take a look below.

Yeah the spreadsheet I have states your CG would be about 7.5 to 8.5 from the tip of the root cord.

Magician

Sep 02, 2006, 10:31 AM

Why is the US Insignia different from the UAV to say the F-18 Hornet?
The one on the ScanEagle looks like one from WWII.

Le,

First congrats on your new model, looks great. As for the reason in the differences in markings, the ScanEagle has what they call low visibility markings. You can see that the actual markings are just a slightly darker grey than the aircraft. They are used when you want to show affiliation but not draw too much attention :-)

Chris

century_series

Sep 02, 2006, 03:25 PM

Le

Forgot to mention: local flow around a cylinder (in this case your fuselage) has roughly twice the AoA as the freestream flow. At least in moderate AoA.
This of course puts your wing root at a higher lift coefficient than the rest of the wing and since that lift is produced up front (swept wing) you´ll probably get a pitch up needed to be compensated by a more forward CoG.

Anyone deep into flying wings please correct me if I'm wrong. Would be interesting to see a graph of the pitching moment as a function of AoA for the whole configuration. My guess is it's not linear. Kip, have you any info?

Regards
Patrik

elossam

Sep 03, 2006, 10:52 AM

Le, as soon as you have an option could you write about inflight datas?: flight time, current consumption, engine temperature, used batteries, engine and propeller...

RCAV8R13

Sep 03, 2006, 12:37 PM

Le,

First congrats on your new model, looks great. As for the reason in the differences in markings, the ScanEagle has what they call low visibility markings. You can see that the actual markings are just a slightly darker grey than the aircraft. They are used when you want to show affiliation but not draw too much attention :-)

Chris
Thanks, Chris.
I was getting frustrated reasearching it. No one at work had any idea.
Kip

vespa

Sep 03, 2006, 11:05 PM

Thought I'd post a few pics from AUVSI for you:

typicalaimster

Sep 03, 2006, 11:58 PM

Huh. So is that tape they are using on the control surfaces?

vespa

Sep 04, 2006, 01:36 AM

No, it's skin hinged at the top and "sealed" with a plastic strip on the bottom

elossam

Sep 04, 2006, 10:22 AM

And the device at the end of each wing? an auto-lock device to catch the model when landing through a hanging wires line?

lphan

Sep 04, 2006, 04:16 PM

vespa,

Cool pictures !!!! I wished I had these earlier too !!

The ScanEaglet has had 4 flights on it so far. It's a joy to fly, and she's pretty fast; as fast as my A-7s ! The 4th flight lasted 20 minutes. I was able to do loop to loops, and aileron rolls without the wings separating ;) The only bummer part is everytime I belly land it, the wingtips catch the grass and whips the plane a bit to an abrupt stop. No damage seen so far.

When I turn off the motor, she has a good glide path, but porpoiseing up and down still. When I fly at full throttle, it seems to go away, but then comes back at times. At full throttle, I have to use full down elevator to keep the nose down. The wings are a closed D-box construction, with entirely sheeted wing, except for the bottom end behind the D-box for wiring access. It seems pretty rigid in twist, or maybe it's not rigid enough. I'm sure I will notice the porpoising when I put in the video camera.

Kip,

Did the real ScanEagle have any of these problems I mentoined?

P.S. Once again, I still have not gotten a real answer to the missing stripes in the insignia. I guess the Marines painted them on and not Insitu?

Cheers,

Le

vespa

Sep 04, 2006, 10:28 PM

Le, I'd suggest moving the c.g. rearward and adding downthrust. The porpoising sounds like it may be from excess stability.

RCAV8R13

Sep 05, 2006, 03:37 PM

Le, I'd suggest moving the c.g. rearward and adding downthrust. The porpoising sounds like it may be from excess stability.
Vespa,
I think you are right with the down thrust, but I would keep the CG where it is untill it is flown with the down thrust. Change one thing at a time. The CG may still need to come back, but I would make changes in steps.
Did you like the servo mounts in the wings of the ScanEagle? Those are my invention, we have a patent on them. The servos snap into place. Easy for production and replacement out in the field. How did our booth look? I heard Boeing had a "ScanEagle CC" (actually it's their Dominator UAV).
Le,
The ScanEagle does not porpoise. But it has 2 deg less twist than yours'.
Kip

lphan

Sep 05, 2006, 07:01 PM

Vespa and Kip,

I just flew the ScanEaglet today, it's 5th flight. I made the nose lighter. It glides fine, but still porpoises. The guys at the field thought it wasn't much. I was able to land it better this time. It flares very well at the end.

I'll try one thing at a time, I'll keep on taking the nose weight out little by little. It's easier to take nose weight out than to mess with the down thrust at this time.

Kip I do like the servo mounts you designed. The pics that Vespa posted. It looks like you have two elevons per wing. Is that for redundancy incase one servo fails?

Cheers,

Le

MIT KID

Sep 05, 2006, 10:37 PM

And the device at the end of each wing? an auto-lock device to catch the model when landing through a hanging wires line?

Here's a series of photos that shows the scan eagle's "skyhook" landing system. Pretty interesting idea.

http://www.defense-update.com/products/s/scaneagle.htm

btw, great work Le

RCAV8R13

Sep 06, 2006, 11:50 AM

RCAV8R13

Sep 06, 2006, 11:52 AM

Here's a series of photos that shows the scan eagle's "skyhook" landing system. Pretty interesting idea.

http://www.defense-update.com/products/s/scaneagle.htm

btw, great work Le
You ain't seen nothin' yet. Just you wait. I'll post more info when we have a press release.
Kip

lphan

Sep 10, 2006, 07:50 AM

Gang,

Here's a new camera pod. I decided to give the "Whiffle Ball" a rest. I went to Krogers and spent $1.00 at the gum ball machines to get a clear plastic ball. I then used a dremel tool to cut out the holes for the camera, pivots, and wire access out the back. I also made a .03" thick aluminum bracket.

Here are some pics.

Cheers,

Le

Joe2003

Sep 10, 2006, 08:33 AM

Its coming on really well, very cool.

Is it a replica UAV or do you plan on putting any major electronics in?

lphan

Sep 10, 2006, 09:26 AM

Joe2003,

I plan to put a video camera on the nose pod and video tape my flights. That's about all I'll probably do for it. Next is to write a magazine construction article on it.

Cheers,

Le

lphan

Sep 19, 2006, 08:43 AM

Gang,

I just installed a 2.4 Ghz Mini Wireless Camera in the pod. I'm hoping to fly it today.

Cheers,
Le

lphan

Sep 19, 2006, 03:55 PM

Flight Video.

Cheers,

Le

http://www.rcgroups.com/forums/showthread.php?t=563672#post6091654

typicalaimster

Sep 19, 2006, 04:58 PM

Hey Le,
Looks good on the video. Check into getting a FMA CoPilot on the sucker next!

lphan

Sep 21, 2006, 10:17 PM

Gang,

Here are the pics maiden flight taken by my photographer Ken Bates !! Thanks Ken !!

Le

kd7ost

Sep 21, 2006, 11:36 PM

Very nice Le,

From the test Pilots perspective, how did it respond in flight?

Dan

Tom Harper

Sep 22, 2006, 07:11 AM

Beautiful in the air. What's the AUW?

RCAV8R13

Sep 22, 2006, 10:36 AM

Congradulations Le,
You are the only other person, in the world, who has ever flown a ScanEagle by R/C control.
Kip

lphan

Sep 22, 2006, 11:40 AM

Gang,

Thanks for the compliments
AUW: 28 oz

From a Pilot's perspective, it's like a fighter ! I can do lllops all day and aileron rolls fine. The trows for the elevon mixing are as follows:

Ailerons: Full
Elevator: 50-25% of Full.

It's just sometimes it porpoises. I can't seem to get it out. I guess I'll keep adding weight to the nose until it stops or before it noses into the ground ;)

Kip,

Now be careful at what you say. I flew the ScanEaglet, not the ScanEagle. I just submitted the article and plans to Model Aviation Magazine :) The article title is: ScanEaglet, Camera Plane.

Cheers,

Le

LukeZ

Sep 23, 2006, 02:43 AM

I'm quite curious, as I've begun to do some reading on wing design for a project of my own - but can someone tell me, what is the advantage of a swept-back wing? And particularly, of a wing with such an extreme degree of it, such as the ScanEagle (and Eaglet ;) )? Obviously it must serve some purpose or it would not have been chosen. I'm wondering what benefit it serves, that was deemed to be especially useful for the ScanEagle's intended application.

I can understand that such a swept-back wing would facilitate the unique arresting system the ScanEagle uses to "land." But surely there were other factors as well?

Luke

lphan

Sep 23, 2006, 08:02 AM

Luke,

I've noticed as I was building the "Eaglet" that it was easy to store. It looks like the real ScanEagle has removable rudders, and wings. You can pack it up in a box easily. As for the swept back wing, it's needed for pitch stability, although a "Scimitar" wing works too. But I think the main reason that Insitu chose the swept wing design was for the "Skyhook" landing system. You need to have a good sweep for the rope to guide the rop down the LE to catch the hook. I noticed that the location of their skyhook is behing the CG of the plane. So after the rope is caught, the plane's engines turn off and the plane swings like "Tarzan" with the nose pointed slightly down.

Well, those are my thoughts on it. I'm curious to hear what Kip has to say.

Cheers,

Le

vespa

Sep 23, 2006, 02:13 PM

Aerodynamically, sweep mostly just causes drag, but it can offer some advantages.
Sweep allows a flying wing to use washout instead of reflex for pitch stability, thus allowing the use of efficient conventional airfoils with the nice side-effect of near-elliptical lift distribution due to the washout.
Sweep offers tremendous drag reduction at/near supersonic speeds.

From a stability standpoint, sweep causes lots of problems with tip stalling and erratic aileron/flap behavior but provides c.g. range tolerance by widening the longitudinal distribution of wing area. It also provides some roll stability without the need for inefficient dihedral.

Of course deltas use extreme amounts of sweep along with extreme amounts of taper and extreme chord lengths and aspect ratios to take advantage of the draggy vortices created by the sweep for unusual lift/stability advantages at low-speeds.

Mechanically is where sweep really shines, not only does it provide flutter resistance, but also great crash/sky-hook geometry, a convenient mounting location for vertical fins (with winglet efficiency side-effects), and favorable weight distribution that allows Zagis to have durable rear-mounted motors, or gliders to balance with only a small battery in the nose.