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Archive for the ‘RC Airplanes’ Category

Flying Videos are a Pain

Posted by Tom Benedict on 24/06/2014

A couple of weeks ago I took my helmet cam, my Zagi, a tripod, and a beach chair, and climbed the cindercone south of Kua Bay. The footage I got from the last time I flew there convinced me that the Gopro does better on a tripod than on my head, so that’s where I put it. I used a Nokia N8 and my Canon A2200 on the helmet to do the tracking footage. The A2200 never really focused all that well, so I was left with the static Gopro footage and the tracking N8 footage.

It worked ok, but the more I try to make flying videos the less I find I enjoy the process. Trying to keep my head level (which I couldn’t) and tracking the plane (which I’m getting better at) took away a lot of the joy of flying the plane in the first place. At one point I took the helmet off so I could just have fun flying it instead of filming it. As it turns out that was a good thing since I wound up using that footage in the video.

After going through all the raw footage I started the long nit-picky process of choosing just the bits I wanted to show. I found a piano piece by The Fat Rat, edited the snippets to fit the music, and made a first cut. jimbo320 on RCGroups gave me some much-needed feedback that I used to further refine it. It’s not stellar, but it’s a beginning. The question is whether I want to pursue this any further, or simply have fun flying the plane.

Unfortunately toward the end my poor Zagi had one too many collisions with the rocks and the trees, and the covering on one wingtip ripped loose. I took it home, pulled all the covering off, and found I had cracked its main spar as well. I built a new spar with a thickened center section, filled the tear in the wing tip with Gorilla Glue, and replaced all of the torn biax reinforcement. I’m re-covering it with the same laminate I used the first time, but the artwork on the plane will be different. The old scheme was far too symmetric top to bottom, which made it difficult to tell orientation from a distance.

So this video is the last time you’ll see this color scheme on my plane. It’s probably also the last slope video I’m going to make for a while. Too much focus on cameras and too little focus on flying makes my poor plane feel like an abused chunk of styrofoam.

– Tom

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Posted in Photography, RC Airplanes | Leave a Comment »

Testing the Helmet Cam

Posted by Tom Benedict on 27/05/2014

In my previous post I described the design(ish) and build of a helmet cam with a reflex sight. Over the last few days I had the chance to take it out and use it on two separate occasions for two very different purposes. Here’s how it went:

Outing #1: Documenting Kite Aerial Photography

One of the reasons I built the helmet cam is that I want to document how I do kite aerial photography. There seems to be a lot of confusion when it comes to things like attaching the camera to the kite line, how the kite goes up the line (hint: it doesn’t), and why KAPers insist on using single line kites instead of two-line or four-line kites. A good set of still photos or even a short video could answer most of these questions. I’ve tried photographing the process of doing KAP in the past, but without a second person to operate the camera it’s just not possible. Enter the hat cam.

To try this I took it with me on a recent outing to the anchialine ponds near the old village of Wainanalii. The ponds are out in the middle of a lava flow, so the only way to get there is on foot. I parked my car off the side of the Queen Kaahumanu Highway and walked in.

King's Trail

A short way in off the road you run into the King’s Highway. This is a trail system commissioned by King Kalakaua in the 1870s. Considering when it was built it’s a remarkable piece of engineering. It runs straight and flat for most of its length, and it spans much of the north Kona coast. I took it from where I parked my car to the turnoff for the anchialine ponds.

As I walked down the King’s Highway I became painfully aware that I had a kiawe thorn stuck straight through my shoe and into my foot. Every time I stepped on a rock my foot was stabbed. Right about the time I reached the turn-off to the ponds, I remembered I always pack pliers in my KAP bag. YAY! I pulled out the thorn and kept going.

Trail to Wainanalii Pond

The trail to the ponds is a little more rough and ready than the King’s Highway. It’s in reasonable shape, but there’s no doubt you’re walking on rocks. It only takes a couple of minutes of hiking the trail before you reach the ponds.

Wainanalii Pond (Golden Pools)

This set of anchialine ponds are sometimes called the Golden Pools for obvious reasons. The color comes from the plants growing on the rocks in the water. As pretty as it is from the ground, it’s even more striking from the air.

Hand Launch

The ponds are in the middle of a relatively fresh lava field so the rocks are sharp enough to cut kite line and shred kite cloth. Since the entire island is volcanic, the same can be said of a number of places I fly. I long ago learned to hand-launch my kites. Long-line launches are simply out of the question.

Clean Wind

Once the kite was up it flew beautifully. The wind has been squirrelly the past few years, but it seems that the end of the drought we’ve been having has brought back the steady winds I grew used to when I first started doing KAP here in Hawaii back in 2007. I let out about 150′ of line before hanging the rig on the line.

Hanging the Rig

The reason most KAPers hang their camera well below their kites is that the more line there is between the camera and the kite, the less the motion of the kite can influence it. Even a relatively stable kite will cause some camera wobble if the camera is suspended directly below the kite bridle. But with even 50′ of separation that motion can be reduced to a slight sway.

The rig is attached firmly to the kite line using snap hooks. The hooks don’t move on the line, so the camera is fixed to that point. All that’s required to raise the camera is to let out more kite line. To bring the camera back down it’s a simple matter of reeling the line back in.

Up and Running

After letting out some line to give the camera some altitude, it was time to do some kite aerial photography. The rig I’m using has two axes of motion: pan and tilt. Some while back I added a video downlink, but it’s not necessary to use it. I did KAP for years aiming by eye and produced some good photos this way. When I added the video link to this rig I did it in such a way that I could bypass it any time I wanted to.

That being said, the viewfinder is handy for tricky subjects or for tricky situations like the one I encountered that day. The sky was blah overcast which caused nasty reflections in the water. I stuck a polarizer on the end of my lens to cut the reflections, but because of the overcast conditions it was very sensitive to orientation. The viewfinder helped me tune the filter’s orientation at each pointing before tripping the shutter. Here are the results:

Golden Pools 1

Golden Pools 2

Except for the two KAP photos at the end all of these were done using the helmet cam. I had both the Gopro and the A2200 on intervalometer mode. Unfortunately I’d left the A2200 set for videos rather than stills, so all I got from it was a series of three second videos made every five seconds. GAAH! All of the helmet cam still photos were from the Gopro. I’m not partial to the Gopro’s fisheye effect when making stills, so I used PTLens to de-fisheye the frames. They were then cropped to a 3:2 ratio in Photoshop. Note to self: double check the mode of the camera next time!

Outing #2: Slope Soaring Videography

The other reason I built the helmet cam was to make slope soaring videos. Slope soaring is one of my favorite ways to fly RC aircraft. It requires no motor, no aero-tow, no high-start, no nothing. You just toss your plane off of a high place and use the wind to create lift. It’s about as close to pure flying as you can get. It also doesn’t cost an arm and a leg to do, which is great for someone like me. All it takes is a plane, a slope, and some wind. Honestly, it’s about as close as an RC airplane can come to a kite. (Hmmmm! Now I know why I like it so much!)

The day after the KAP session at the anchialine ponds I took my Zagi 5C and my helmet cam out to the cinder cone near Kua Bay. This has been a popular slope soaring site on the Big Island for many many years. It’s a good place to fly, but folks who are more used to grassier slopes may find the landing zone a little harsh.

I wanted to test two things: First, I wanted to make videos with both the Gopro and the A2200. Second, I wanted to make a set of stills to see how the fields of view compared. For this test I had the A2200 zoomed all the way in.

I should probably preface the rest of this by saying that with the exception of one Bixler flight, I haven’t flown a plane in months. I certainly haven’t flown slope. The wind was coming from an oddball quarter, so the lift zone wasn’t where I was used to finding it. All of this combined to make for challenging flying. Throw the helmet cam into the mix and I had a hard time splitting my attention between flying the plane and aiming the camera. I eventually did get the hang of it, but in the beginning I made a lot of short flights that ended with abrupt landings.

The reflex sight made it very easy to keep the camera pointed at the plane. When making stills I found it helped to set the shutter sound as loud as I could. The camera was running a five second intervalometer, so every five seconds I heard a loud “kachunk” sound, letting me know it had taken a picture. After a while my flying fell into a cadence of one-two-three-four-click! one-two-three-four-click! At around four seconds I found myself rolling the plane so I could see the top or bottom of the wing. This was great for photography, but it exacerbated my tendency to fly off the lift. Still, the pictures were nice.

Zagi 5C In Flight

You don’t even want to see the corresponding Gopro shot from that point in time. The plane is just a dot out toward the water. The long reach of the A2200 really brought the plane in close, and the reflex sight made it easy to keep it in the frame.

Videos were a little tougher. As a test I ran the Gopro in wide mode, the A2200 zoomed all the way in, an 808 #16D keychain camera on the Zagi, and my T2i on the ground on a tripod. The T2i footage was rubbish, but the rest came out ok. I also recorded audio using a portable field recorder. My audio work isn’t all that hot, but the video came out better than I expected.

I ran into two big problems: The first was that even a tiny lapse in concentration was enough for the plane to move out toward the edge of the field in the A2200. When I really focused, it worked better. I tried putting the dot near the plane rather than directly on it so that I could shift it around in the frame. This didn’t work out too well. The field of view of the A2200 was so small, even tiny shifts were enough for it to slide out toward the edge of the frame. But with judicious editing most of those lapses could have been covered. I didn’t cover them because I wanted to see the faults with the method as well as its strengths.

The second problem I ran into was that keeping the horizon level was non-trivial. I never realized how much we roll our heads when we turn our necks. It’s astounding how much the horizon bobbled a round in the video! By the end, though, my rolly-polly horizon was getting better.

I think both of these problems would have been minimized if I hadn’t been the one flying the airplane. The helmet cam certainly lets you document your own flights. But I think its real strength may be in videoing the flights of others.

– Tom

Posted in Engineering, Kite Aerial Photography, Photography, RC Airplanes | 1 Comment »

Building the Helmet Cam

Posted by Tom Benedict on 19/05/2014

The biggest problem with most hat cams or helmet cams is that there’s no way to aim them accurately. A couple of posts back I mentioned a project to attach a reflex sight to a helmet camera to give me some way to keep the camera aimed at the subject. I ordered a reflex sight and a Picatinny / Weaver rail to mount it on along with a Gopro Frame mount. All the bits and pieces have arrived, so I started designing. Then I realized this is really a scrap box project: the design and build phases are really one and the same. So I started over with the bare bits I wanted to stick on the helmet: a Gopro, an A2200, and a reflex sight, and got busy.

Two Cameras and a Reflex Sight

Reflex Sight:

The reflex sight has nearly zero magnification and projects a red dot into your field of vision as if you had a laser pointed out at the landscape. The idea is that once the sight is dialed in, the center of the frame of the camera will lie where the red dot points.

Reflex Sight Dot

The dot is projected out at infinity, which explains the reason why I couldn’t get the dot and the body of the sight in focus at the same time. (Dang limited depth of field!) Even though this one was made for a firearm, reflex sights like this have been used as wide field finder scopes on amateur telescopes for decades. Adapting one to this application seemed reasonable.

Camera Mounts:

I toyed with the idea of having the two cameras share a common mount, but wound up scrapping the idea. The field of view of the Gopro is wide enough that I can get the two reasonably aligned even if the Gopro is on a separate mount. Since my Gopro came with a bunch of helmet mounts I sacrificed one to the project and stuck it to my bicycle helmet. Done.

Gopro Helmet Mount

Since I’m planning to use the A2200 zoomed in to about 35-50mm equivalent, its pointing is more critical. The reflex sight has screws for adjusting azimuth and elevation, so the mount for the A2200 is fixed – no ballhead, no adjustments, just a hard stop at the back to keep it from rotating on its tripod screw. The reflex sight and its mount need to maintain registration with the A2200 mount, so I built them as a single unit that can be mounted to my bicycle helmet.

Reflex Sight Mount:

I’m left-eye dominant. Most of the time when building aiming devices you want to use your dominant eye. But since the idea here is to also have one unobstructed eye to… well… to keep an eye on things, I also wanted to leave my dominant eye free. In short, I really wasn’t sure which eye to put the sight in front of. So I made it ambidextrous. To do this I just needed to have another rail on the other side of the camera mount so the sight can be mounted on either one. In anticipation of this I bought two lengths of rail. As it turns out each one was just over twice as long as I needed, so I cut one in half and kept the other as a spare.

Reflex Sight on Rails

Since the camera will be mounted above my eye line rather than below, I decided to mount the sight upside-down. This is the opposite of how these are typically mounted, but in this case it made sense. This keeps everything nice and compact, minimizes parallax between the sight and the camera, and simplifies attaching the sight to the camera mount.

Helmet Mount:

A quick word about the fate of my bicycle helmet: It’s doomed never to be used on a bicycle again. In order to mount all this hardware to the helmet I wound up screwing and gluing a strip of aluminum to the front of the helmet. From a crash standpoint this basically means I’ve got lots of sharp metal points aiming at my head. A crash with this thing on would be an instant frontal lobotomy. So from this day forth it’s strictly a camera mount.

Reflex Helmet Mount

The helmet has a vent hole straight down its centerline so I had to use a wider strip of aluminum than I wanted to. I wound up using a strip 1.7″ wide with screws spaced 1″ apart down the sides. The strip was bent across a form (the corner of the bandsaw table) and glued using white Gorilla Glue. It’s not coming off.

The edge of the strip that protrudes down in front of my face has  double row of holes spaced 1″ apart. The holes are spaced 0.2″ apart vertically to give me some range of height adjustment for the camera mount. I put four corresponding threaded holes in the camera mount spaced 0.3″ apart. Depending on the combination of holes I use, I can change the height of the whole camera mount in 0.1″ increments. It turned out I didn’t need this kind of adjustability, but it’s there.

Putting It All Together:

A lot of the “where should things go” decisions on this were made by standing in front of a mirror with all the various parts in hand. I know now my eyes are slightly less than 3″ apart, they’re shifty, and I’m not to be trusted. No! Wait! Disregard that. (They really are less than 3″ apart, though. Gotta love calipers.) I now know my helmet stops several inches above my eye line. So much so that I had to change my original idea for the mount to add more “drop” to it. Once I got those issues sorted out, though, it was just a matter of bolting it all together.

Whole Shebang

Of course no design choice, no machining technique, could keep this from making me look like an utter dork once I strapped it to my head.

Dork in a Headdress

But hey, if it gets good photos and video footage, it’s worth it.

– Tom

Posted in Photography, RC Airplanes | 5 Comments »

New Experiments

Posted by Tom Benedict on 29/03/2014

Because of stuff going on outside of work and hobbies, both work and hobbies have taken something of a back seat in the last month. Typically when this happens I wind up with a backlog of work I need to do as well as a notebook full of hobby ideas I want to take on when the smoke clears and normal life resumes.

The backlog at work happened right on schedule. I’ll be surprised if I dig my way out any time in the next twelve months. And the hobby notebook? I went through the list of ideas and cleared it down to four:

Project 1 – Untaping the Gopro

Pretty simple, really. I’ve been flying my Gopro on my RC airplanes by taping it down with blue painter’s tape. I went this route for a couple of reasons: First, the waterproof case introduces a planar/planar optic in front of a wide-angle lens. This is guaranteed to degrade image quality. Second, the weight of the waterproof case almost doubles the weight of the camera. Unlike kites, airplanes are very touchy about how much weight they can carry. So I went with the “lightweight” mount: blue painter’s tape.

This is a silly thing to do for a number of reasons. If the tape gets wet (which NEVER happens up in the air in the tropics! Gosh!) it starts to fail. A Gopro falling from a couple hundred feet is an injury waiting to happen. Also, it doesn’t offer a lot of options for aiming the camera. So I got a third-party “Frame” case. I’m probably going to stick a 1/4″-20 tripod mount on top of my Phoenix and attach it to that. Lightweight, solid, and I can finally aim the damn thing.

Along with the Frame case I also got a low-profile FPV cable for the Gopro. This lets you power the Gopro from your RC system using a BEC, so you can shave even more weight by leaving out the battery. And the video end of the cable will plug into the video transmitter for both my KAP rig and my planes, so it serves dual purpose.

I’m looking forward to flying the Gopro on my KAP rig with the video cable. As wide as the field of view of the Gopro is, I’ve blown a number of good opportunities to KAP some excellent boogie board action at Hapuna Beach because the subject was off-center in the frame.

Project 2 – OrangeRX Flight Stabilizer Hack

In a thread on the KAP forum, Bill Blake mentioned the OrangeRX RX3S Flight Stabilizer sold by Hobby King. He got one and tested it as a KAP camera stabilizer, but found it to be too slow and notchy in its movements. While poking around for information about the thing I ran across a web site that had a third-party firmware for the RX3S that might solve the notchy problem (improved interrupt handlers), along with some other improvements.

While I was cruising around on that page I saw that the RX3S is basically an Arduino with a 3-axis gyro, three potentiometers, a bank of switches, and headers for servos. Take the idea of it being a flight stabilizer out of the equation and just think of it as a pre-packaged microcontroller with a bunch of cool stuff tacked on, and all of a sudden all sorts of possibilities come to mind.

One I’ve been toying with for a while is an RCKAP / autoKAP switch: In one mode it lets you control pitch, yaw, and shutter. In the other mode the microcontroller acts like an autoKAP controller and moves the camera through a fixed pattern automatically. If the RC receiver it’s plugged into has a failsafe setting on the channel that controls the behavior of the micro, you could have it default to “turn me to autoKAP” when no transmitter signal is detected. Voila! If you leave your radio at home, you get an autoKAP rig. If you bring it you get both RCKAP and autoKAP at the flick of a switch.

So yeah, I got one of these, too. Shipping from Hong Kong being what it is, I expect to see it in a couple of months. Such is life.

Project 3 – KAP / Pole Rig Adapter

This actually ties into another long-term project: building a passively stabilized pendulum KAP rig with an actively stabilized gimbal on the bottom. To do the testing for this, I want to be able to swap rapidly between Picavet and pendulum suspensions on the same rig so I could compare them under similar conditions back-to-back.

As I was going through the sketches and CAD work for the quick-change suspension mount, I realized that a slightly beefier version would mean I could take my KAP rig, flip it upside-down, and attach it to a pole as well. Yay! No more separate rigs!

That’s when it occurred to me that if I was careful about it, I could make a whole set of mating adapters. That way I could carry around one Picavet, one pendulum, one pole, and multiple KAP rigs. Depending on the requirements of the photo I could use a pole or a kite to lift the camera, and put the camera in any of the rigs I have sitting around at the moment. Versatility at its best!

Design work for stuff like this is always something of an iterative process. It needs to be robust, light, and simple to build. Robust is easy: make it in large chunks. Light is easy, too (use small chunks!) but a little harder if you don’t want to jeopardize robustness. And simple to build? Yeah, that’s the kicker. I’m trying to get these down to three setups on no more than two tools. I’m almost there.

Project 4 – A Helmet Camera that Aims!

Years ago I knew a skydiver who later became a photographer and videographer. Even back then (back when film was king) I was fascinated by the hardware the skydiver videographers used. They wore specialized helmets that let them mount video cameras, 35mm cameras, medium format cameras, etc. on their heads, all of which could be triggered using a handheld remote.

That’s all well and good, you might think. No different from a headcam or hatcam mount for a Gopro. Aaaah, but there was one other thing the skydivers had that most head-mounted cameras don’t: a way to aim.

The skydivers all used reflex sights bolted to their helmets to help them aim. The reflex sight projects a dot or crosshair into your field of vision. No matter how you move your eye, the dot’s orientation is preserved. Once all the cameras are aimed to center their frames on that dot, the skydiver only needs to aim the dot at the subject and hit the button on their handheld remote. Bang! All their camera shutters trip, capturing the action.

So I looked up “reflex sight” on Ebay to see what these things cost these days. I was amazed to see they were less than $30US. WOW!

So the last project is to make either a hat or helmet camera mount with a reflex sight over one eye. By bolting a combination of a wide angle camera (Gopro, probably) and a narrow-angle camera (A2200?) on the mount, some neat possibilities open up for slope soaring videos or really any videos that require tracking a moving subject.

Unfortunately I don’t have the shop cash to spring for the reflex sight as well. Not this month, anyway. That project will have to wait.

– Tom

EDIT: I talked to my family’s CFO (aka “my wife”) and she gave me the go-ahead to pick up the reflex sight and rail. Yaaaay! But she cautioned me that if I tack a DSLR with a big bazooka of a lens on the top of my head, she will disown me.

Posted in Engineering, Kite Aerial Photography, Photography, RC Airplanes | 4 Comments »

A New Slope Site

Posted by Tom Benedict on 12/02/2014

I admit it, I’m chicken when it comes to throwing my gliders out over a cliff, especially if I can’t find a way to get to the bottom of the cliff to recover my plane after pulling a boneheaded maneuver. This has kept me from finding really stellar slope sites on the Big Island. So far the two I’ve flown the most are the pu`u at Kua Bay and a grassy slope out at the edge of an old quarry. Kua Bay is nice because there’s no fence hopping involved. But the landing zone is all rock, and it’s over a half hour drive to get there. The quarry is great because the slope is all grass, but you have to hop a fence to get there, so it’s just a matter of time before we get chased off. Clearly I need a new place to fly.

While going through some of my earlier photography to find stuff I might put up on 1x.com, I ran across a set I did at Kauhola Point at the north end of the Big Island. It’s the set this one came from:

Lighthouse from Up HighThe cliffs are heavily eroded right by the lighthouse, which makes them scary as far as climbing goes. But as I went through the other photos from the set, I ran across some showing the cliffs just to the east. Solid rock! And on one of them there was a path that led down to a rocky surfing beach. Perfect! And as it turns out I flew over a nearby farm that had a great view of the cliffs from a kite. Different day, drier season, but you can see how nice these cliffs would be for sloping. (The leaning trees give you a pretty good idea of the average wind direction here…)

Kauhola Point

The fine folks at Mauna Kea Soaring appear to have their wind models running again, so I was even able to check the conditions at Kauhola Point. (The guy who runs the wind models is a fellow slope soarer and a fellow Zagi 5C owner. He also happens to be the Director of Engineering at the place where I work. Small world!) The winds look good! If they hold through the weekend, I’m getting out with a couple of planes to go play.

I promised people at RCGroups that I’d take stills and video the next time I got out. Seems like Kauhola Point would be a great place to do this. So I’ll pack cameras, too. Report to come!

– Tom

P.S. WHAT A DWEEB! After posting this I madly rushed off to RCGroups to write a post for a thread on Big Island sloping sites. RIGHT THERE was a post I made back in October last year in which I posted this same picture. GAAAH! I already knew about this place! And I forgot! I have no one to blame but myself. >sigh<

Posted in Kite Aerial Photography, RC Airplanes | Leave a Comment »

First Aerial Photography of 2014

Posted by Tom Benedict on 03/01/2014

I’ve been on vacation for the last week and a half, and still have five more days to go. This is a GREAT way to start a new year. I’ve also been doing a ton of photography. Mostly long-duration sunsets, but I finally got airborne over the last two days for some aerial photography.

Yesterday I flew a plane with a Gopro on it, just to see what it would look like. Up until now I’ve only done videos from planes. Never stills. This time I wanted to see what stills looked like. Unfortunately my setup was far from ideal, and I wound up tip-stalling about a hundred feet off the deck. I couldn’t build up enough airspeed to recover, so the plane went in. The Gopro survived, but the plane needs a new nose. I’m taking this opportunity to replace it with one that’s a little more conducive to mounting cameras. Meanwhile, the latest photograph of Mala `ai garden was done from a plane:

Mala `ai from a Plane

Today I grabbed my KAP gear and headed down to Waialea Bay for my first KAP session of 2014. To be fair, I’ve been dragging my KAP gear all over for the last week, hoping to get some flying in. But the weather has been horrid for KAP: no wind, lots of rain, and terrible light. Today changed all that. Lots of wind, no rain, and stellar late-day light.

Two at Waialea Bay

The wind was pretty rocky for this location. I used a Flow Form 16, which is normally a reasonably stable kite. Today it was swooping all over the place. I hung my T2i from the line anyway, and flew. Only two of the pictures were truly blurry, but almost all of them were soft to some degree. This was one of the only survivors. It’s reasonably sharp, though the composition isn’t exactly what I was after. Still, after days of nothing it was great to have something coming off the camera.

So here’s to 2014. May it be a year of good weather, good flying, and good times.

– Tom

Posted in Kite Aerial Photography, Photography, RC Airplanes | 2 Comments »

Conservation of Plane

Posted by Tom Benedict on 24/12/2013

I’m convinced there’s a law of physics out there somewhere that dictates a conservation of plane.

A couple of weeks ago I took my Bixler 2 out to a local field to start teaching my son to fly. I launched and got him some stick time while the plane was three mistakes high, but the whole time he was asking me to let him land it. Rather than go through that I landed the plane and then did some toss-glide flights so he could get some stick time near the ground. After crashing it about ten times he admitted that landing was a lot harder than it looked! And after those ten crashes, my plane was shot. I had cracks in the fuselage, both wings were cracked through to the spar, and one of the control horns had ripped out of one of the ailerons.

So I had three operable planes and one dead one. A couple of weeks of occasional work in the evenings got it back up and running, though: Gorilla Glue to fix the cracked wings, some foam filler in a torn out section, some glue for the tail boom, a re-work of the control horn, etc. As of a couple of days ago the plane was back in shape and hanging on my wall.

Today I took my Zagi and Le Fish, and my daughter, to the local slope to fly. I’m still trying to get my Le Fish flying the way I want, but without a grassy slope to fly from it’s been a little traumatic to the plane. After several rough landings I wound up hitting a thorn bush. By the time I extracted it, I had some chunks taken out of the wings and the tail boom was cracked. One Le Fish down.

I switched back to the Zagi just to clear my head and make up for the fact I’d busted a plane I’ve been so careful with up ’till now. Out of the blue my daughter pipes up and asks, “Can I learn to fly?”

The slope isn’t the ideal starting point for learning to fly a plane. You have to care about the wind and the terrain and the plane. A better scenario is the one I introduced my son to: hand-tossed gliding landings. But hey, she was interested. Why not?

I launched, talked her through the controls, and handed over. First thing she did was turn downwind toward the slope, ride the lift high over the ridge, and get lost in the rotor. The plane came down hard in the caldera of the cinder cone we were standing on. >sigh< We hiked down to where the plane was, only to find the battery pack blown all over the place. Second plane down.

I try to see the positive in things whenever I can. The only positive I can come up with for today is that we flew every second we could. We’d literally flown the bejeebers out of both planes. By the end of the day they were utterly bejeeberless. And they looked it!

I got the Zagi fixed pretty quickly. It just needed a new battery pack, after all. But the Le Fish will take some time to repair, especially the tail boom. Back to three operable planes and one dead one.

Damn physics…

– Tom

Posted in RC Airplanes | Leave a Comment »

Video Downlink for KAP

Posted by Tom Benedict on 04/12/2013

This is the third and final installment of KAP articles. In Then and Now I described the evolution of my KAP rig from my first flight to the rig I use regularly today. In A Progression of Kites I described the additions I made to my kite bag over the years, and what those kites provided for in terms of KAP. This article describes my video downlink system.

The previous two articles were written almost as a history: “First this happened, then this happened.” But over the years as I solved the various problems I ran into with my video downlink system, I wrote articles describing what I did. So the history version of this has already been written. Rather than repeat what I wrote, this article is more of a how-to for adding a video downlink system to a KAP rig.

In its very simplest design a video link is a wire that connects the video output of a camera with the video input of a display device. It’s possible to set up a KAP rig this way, but the wire would have to be long, heavy, and would be a nasty thing to have in your hand when lightning strikes. For obvious reasons, it’s preferable to send the video signal to the ground some other way: radio.

It bears mentioning at this stage that unlike a wire, leaping into the world of radio places the operator in a new situation. At this point you’re transmitting your signal in such a way that it can potentially interfere with other wireless devices. In most countries radio transmitters are regulated, and typically fall into two categories: Either the device has been declared fit for use by an untrained person or it has not. In the US this declaration comes in the form of FCC Part 15 approval. If the device has an FCC Part 15 sticker on it, you can use it without a license. If it doesn’t, you can’t. The laws in other countries will vary, but that’s how it is here.

FCC Sticker

As was pointed out to me when I started down this road a couple of years ago, if you wind up using equipment that doesn’t carry your country’s seal of approval, it’s up to you to get whatever licenses are necessary for you to stay on the right side of the law. Unfortunately most video transmitter gear requires a license. (In case you’re wondering, that’s a picture of a 2.4GHz transmitter module from an RC radio. Most RC gear is approved for unlicensed use. The manufacturers are well motivated to make sure their stuff is certified. Video manufacturers? Not so much.)

There’s another benefit to studying for and getting your radio license. The whole point of the exercise is to give you the information you need to successfully and safely experiment in the world of radio. And that’s precisely what you’re doing! You’re exploring the world of radio by setting up an amateur TV station and a receiver. Questions that you’ll need to answer will include how much power to use, what kind of antenna to use, how much radiation exposure you’ll get, etc. By virtue of studying for and receiving your amateur radio operator’s license, you’ll find the answers to these and other questions. It’s well worth it.

Back to the video link!

The next question you’re probably asking is, “But what do I have to get to make it work?” Unfortunately there’s no right answer because there’s more than one way to do it. Here are some things to consider:

Most video hardware is built to handle either NTSC, PAL, or both of these formats. When looking at your gear – camera, video transmitter, video receiver, and monitor – keep in mind which system you’re using and make sure all your hardware will handle it. I got hardware that will handle both, so I can switch the entire setup from NTSC to PAL and back without penalty.

All of this hardware will have to be powered. In the world of FPV RC aircraft, there’s an advantage to running your video system on a completely different power supply than your radio system. That way when your video system drains your batteries dry, your aircraft doesn’t suddenly fall out of the sky in an uncontrolled heap. This isn’t as big a consideration in the world of KAP since the kite will fly regardless of the state of the batteries. (A single line kite with a dead battery flies exactly the same as a single line kite with a fully charged battery. The kite really doesn’t care.) So there’s an advantage to choosing gear that can all be powered off of a single source.

Between the transmitter and the receiver you will need a pair of antennas. At their simplest an antenna is a piece of wire trimmed to a particular length (1/4 the wavelength of the transmitted signal). At their most complex they can be fairly complicated pieces of equipment that preferentially transmit and receive in a particular direction, polarize the signal in a particular way, etc. Keep in mind that the size of the antenna is always dependent on the wavelength of the transmitted signal.

And while keeping that in mind, consider that radio gear for sending and receiving video signals can be built to operate on a wide range of wavelengths. At the longer end of the spectrum (literally) you can get 900MHz hardware. At the shorter end you can get 5.8GHz hardware. In between you can find hardware built to 1.2MHz, 1.3MHz, 2.4MHz, etc. The longer your wavelength, the better the signal will penetrate solid objects and bend around corners, and the less power it will take to get a particular range. This favors longer wavelengths. Conversely, the shorter your wavelength, the smaller your antenna. This favors shorter wavelengths. And no matter what, you don’t want your video system to interfere with your RC transmitter, either at the primary frequency or at a harmonic (n * freq). So if you’re using 2.4GHz RC gear, don’t use 2.4GHz or 1.2GHz video gear.

Finally, you’ll need some form of display on which to see the image from your camera. Options for this range from fully enclosed headsets like the ones from FatShark to standalone monitors. The display you choose will depend greatly on what you’re doing.

Regardless of whether you’re planning to build a video downlink for KAP or an FPV setup for RC aircraft, it’s really not safe to use a self-enclosed headset if you plan on operating your gear by yourself. The AMA’s safety guide for FPV specifically says you should use a spotter when flying FPV, and that they should maintain line-of-sight on the aircraft at all times. It’s really no different for KAP. If you’ve spent any amount of time flying single line kites, chances are you’ve seen them do something unexpected. If you’re watching the kite you can typically do something to recover. If you’re staring into a self-enclosed headset, you won’t notice until it’s way way too late. If you plan to use a headset for KAP, also plan to bring someone along to operate the kite. I’m a solo KAPer, so I built my system to use a monitor.

Something to look for when getting a monitor is what it does when it loses signal or encounters a glitch. Many of them switch to a blue screen. Because radio signals are almost always glitchy, this means that the monitor will spend most of its time being blue. Look for a monitor that will show static when it loses signal or encounters a glitch. Most of the ones that do will proudly tell you of this on the packaging or in the advertisement, and may even say, “Made for FPV use!” My first two monitors did the blue screen thing. Skip the pain and get a good monitor from the get-go.

Now for the real question: How do you wire all this stuff together? Fortunately the world of FPV has made these systems a lot more turnkey than they used to be. Unfortunately they’re not as turnkey as, say, plugging servos into a receiver and moving them with joysticks. Some soldering is typically required. Here’s the diagram for the system I built using Boscam 5.8GHz hardware:

FPV Wiring Diagram

I used a 3-cell LiPoly battery to power the video system, so the video transmitter is getting between 12.6V and 11.6V. The UBEC steps that down to 5V for the RC receiver and servos. I don’t use the Vcamera output on the transmitter to power the camera, and rely on the camera’s own internal battery for its power.

Keep in mind this is for a KAP system. I built out a similar system for FPV. In that case I omitted the UBEC and didn’t provide any connection between the video system and the RC system. This was in order to avoid RF interference from the airplane’s ESC, motor, and servos, and to keep the video system from draining the flight battery, as I said earlier.

When setting up your radio gear, carefully check the channels the gear can operate on to make sure the frequencies are legal in your country. Not all countries allow amateur use on all bands, and not all countries define the bands the same way. You should be able to find the frequencies used for each channel in the manual for your hardware.

When setting up the channels on mine I ran into another problem: The Boscam 5.8GHz Rx and Tx use banks of DIP switches to set the channel. Unfortunately on one of them 1 is up and 0 is down, and on the other 1 is down and 0 is up. Even worse, the setting for channel 1 on the transmitter and the setting for channel 1 on the receiver are completely different! So for those using the Boscam 5.8GHz system, this diagram appears to be correct if you are looking at the numbers on the DIP switch banks (original source):

Boscam VTx VRx Channels

Because I knew I wanted to be able to swap cameras on my KAP rig, I wired the three video/audio/ground wires to a male servo connector and built individual camera cables that ended in female servo connectors. To swap cameras, all I have to do is swap cables.

Quick aside: If you plan to do anything with any sort of servo gear – KAP, RC airplanes, robotics, whatever – get a bag of male connectors, a bag of female connectors, a spool of servo wire, and a crimp tool. Places like Servo City carry these as stock items. I have never regretted getting mine. The only regret I’ve had is that I didn’t get bigger bags of connectors! You’ll find these come in handy for more than just servos.

Ground stations vary from person to person. I built mine for KAP, so it’s small, self-contained, and can be attached to my RC transmitter.

KAP Video Ground Station Rear

I use the same ground station for FPV. It consists of the video receiver and antenna, a monitor, and a battery. The wiring is typically a little more straightforward than on the transmitter gear. Both video receiver and monitor usually come with RCA connectors, so it’s just a matter of plugging everything in. In my case, though, the RCA cables were all male! Rather than use a bunch of female/female gender changers to connect the cables together, I made all new cables. But it’s not necessary to go this far with your gear.

Once you have all your bits and have wired them together, test it thoroughly on the ground. Having a KAP video downlink fail in the field is a bummer, but it’s not the end of the world. Most of us start off either using autoKAP or aiming by looking up at the camera, so not having a video downlink isn’t a show-stopper. It’s just not fun. If you’re building out an FPV link for an RC aircraft, losing your video feed mid-flight can be a lot more disorienting and may lead to a crash. So test first. Then test again. Then, just for grins, test it again. I spent way too many KAP sessions chasing video problems to chance it these days.

Whatever route you go, remember to fly safely whether you’re flying a kite, a plane, a helicopter, or a multi-rotor. Using a video downlink of any sort means you’re taking your eyes off of your aerial platform. In the case of a kite, finding it again is just a matter of looking up the line. In the case of an airplane or helicopter, it may take you a while to pick it out of the sky. Use a spotter. And expect things to go wrong. They always do.

– Tom

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Slope: Kua Bay

Posted by Tom Benedict on 04/11/2013

The most consistent slope I have within decent driving distance of my house is the pu`u (cindercone) just south of Kua Bay on the Big Island of Hawaii. It’s about a forty minute  drive by car, and is on the way to Costco. So once every two weeks when we do our big Costco buy, I essentially get a free trip to the slope. So long as I can pack some planes in the car along with the coolers we normally take, I’m good to go.

Walking In

There’s no fence to climb, no gate to go through, no nothing. The trail starts just off the access road to Kua Bay and takes you either to the north peak or the south peak, depending on which branch you follow. The north peak is considerably higher, and is the preferred slope, but it’s only good when the wind is coming out of the north. Most of the time the southern peak – or rather the southern ridge – is where you wind up, as I did in that photo.

Launch

Launching is dead nuts easy off this slope. There are no obstructions to steer around. Just toss and fly.

Flight

And the flying is nice. The lift zone is a little flat, so once you drop below the horizon you really have to work to get back up into it. With a light enough plane and good conditions you can get way up in the lift, almost twice the height of the pu`u. But at that altitude the lift is pretty minimal. Because of the shape of the ridge, the lift falls off rapidly to either side as well. When you’re facing directly into the wind, there’s almost no lift zone on the left side. The wind rolls around the shoulder of the cindercone. On the right, however, because of the other peak, you can still get lift even 45 degrees to the wind. So the flying tends to be a little asymmetric. But it’s all good.

It didn’t happen the last time I was out there, but on occasion tropic birds will fly the lift off this slope as well. It’s pretty neat to be there, flying your plane, and have a bird or two drop in to check you out. It’s humbling, too, when they eventually get bored, twist a wing, and shoot up effortlessly into the sky.

Walk of Shame

The only real problem with this site is the landing zone and the slope itself. It’s all rock. There are some trees, but they all have thorns that like to tear wing covering. All of my ridge-top landings were hand-caught the day these pictures were made, simply to spare the plane from the wear and tear. But because the wind was weak, I had a ton of landings down-slope. The only thing for it is to hike down, grab your plane, and hike back up. On days like this one I find myself wishing for a little grass.

If you decide to go flying from this slope, be sure to wear sunscreen and a hat (both of which I forgot this day), and bring plenty of water (which I also forgot). The sun can be punishing, and there’s the hike at the beginning and end to contend with.

I brought two planes this day, but only really wound up flying the Zagi 5C wing. I launched my Le Fish a couple of times, but I’m still not 100% happy with the balance on it, and this just wasn’t the slope to test on. That’ll have to wait for another day and a different slope.

– Tom

P.S. All the photos in this set were done by Rydra. She has way more patience with me than I deserve.

Posted in RC Airplanes | 2 Comments »

Trials and Tribulations of a Hobby

Posted by Tom Benedict on 19/09/2013

One question I’m often asked when I’m out doing KAP is, “How many cameras have you destroyed?” So far the answer is none. A lot of what goes into KAP is making sure you’re safe. Not just to your gear, but to the people and the things around you. I have had some impacts at higher speeds than I’m comfortable with, but so far my cameras have always come away intact.

Kites can take damage, too. I’ve replaced my fair share of spars, and have patched more than one sail. This is par for the course. And while it’s possible to lose entire kites to trees or to broken kite line, so far I’ve escaped that particular tragedy.

Put it all together and it’s possible for me to lose well over a thousand dollars on a single flight if something goes horribly wrong. Between the kite ($100-250) the camera ($850 new) and the rig (about $300 rolled into it right now), it’s substantial.

All of which puts some perspective on this:

Raptor Gone

It’s my first complete loss catastrophe with RC airplanes. The unfortunate bird is my Raptor 2000 Advance from R2Hobbies. Earlier in the day I had a hard(ish) landing. Afterward I checked all my control surfaces, but forgot to check the notoriously fragile tail for fractures. It turns out the left surface had broken loose. When I re-launched, the tail feather wobbled enough for me to see something was wrong. I did everything I could to bring it around for a landing, but before I’d completed the turn the feather snapped off entirely, and the airplane went into a building.

No damage to the building, but my ego took some damage and the plane was almost a complete loss. The left wing is still intact, provided I can glue the wing tip back on. The rest is gone.

I pulled all the electronics out last night, and to my surprise I found everything survived intact: 6 servos, 40A ESC, receiver, motor, and even the prop all came through unscathed. (The battery dead-shorted on landing, unfortunately. No fire, but no battery either.)

So as bad as it looks, it’s not as bad as it could’ve been. And certainly not as bad as a KAP accident. The plane was $120. That’s half the price of my Dopero, and only slightly more expensive than my Fled – two of my low-wind KAP kites.

While I’m still disappointed, it’s not the end of the world. It’s par for the course with this hobby. The same is true of most hobbies. This one just seems to be a little more spectacular when things go wrong.

I had a good month of Getty sales, which helped put me back in a good mood. After a couple of days of asking around on the RCGroups forums, I’ve got a Phoenix 2000 glider on its way along with a Thermal Scout from Winged Shadow Systems and a 5.8GHz radio link to get audio vario information on the ground. But that’s a post for another day.

– Tom

Posted in RC Airplanes | 5 Comments »