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Archive for May, 2013

RC Updates

Posted by Tom Benedict on 30/05/2013

Last weekend was a busy time. Here’s an update on a number of RC projects:

Landsailers – The wheels came in for my land sailers! Then I found out my stash of M8 bolts didn’t have what I needed to finish out the wheel hardware. So I’m close to starting the build on these, but not there yet. The idea is to build a pair of RC land yachts so the kids and I can bop around with them in a nearby parking lot any time the wind picks up too much to fly kites or planes. If I can find the bolts at the hardware store this week, I’ll start work on these this weekend.

Le Fish – My Le Fish came in from Leading Edge Gliders! This is a kit for a standard weight Fish, but I’m still planning to do some modest lightweight mods to it so I can fly it in a slightly wider wind range than it was intended for. There’s a lot of “set the glue and wait” on this plane, so I plan to work on this in parallel with the land yachts. Many pictures to come.

You Can Break a Zagi – These things really are practically indestructable. I put mine into a rocky slope at thirty or forty miles an hour, knocked both servos out, and generally made a mess of things. Getting it airborne again was a simple matter of shoving the servos back in and tossing it off the slope again. But this time was different. I found if you combine a chainlink fence, a lousy flying site, and an inexperienced pilot, you can break practically anything. I ripped both winglets off, and snapped the center spar in half. The winglets are repaired, the covering restored, and new spars are on order from Aloft Hobbies. I should have it flying again by Saturday.

I Finally Flew my Raptor 2000 Advance – Well… strictly speaking I flew it a couple of weeks ago. I did a series of unpowered flights to check center of gravity, balance, etc. It flew great, but cracked one tail fin off on landing. This time I powered it up. Holy CRAP! In an earlier post I wrote about testing the power train with a watt meter, only to find out it’ll draw half a kilowatt at full throttle. On a 1300mAh battery, that worked out to about two minutes of throttle time before the battery was kaput. During the power-on tests, I never got above half throttle. Even at that, it almost went ballistic. It also had a horrid tendency to torque steer, and roll off to the left. Violently. I did three flights, each with only one powered leg, followed by a glide and landing. On the third one the OTHER tail feather snapped off. I have some serious mixing to think about, and a tail to fix. (I already fixed it.)

I Didn’t Break my Bixler! – Granted, I never flew it last weekend. But hey, it’s the only plane I didn’t break! I’m taking this as a win.

Final update: I ran into Jerry the Glider Guy (no, that’s not really his last name) at a coffee shop over the weekend. If the weather is willing, he’s planning to go slope soaring over Pololu Valley this coming Sunday. If I can get my Zagi airworthy again by that time, I’m planning to go out and join in the fun. Yeah, this’ll cut into construction of the land yachts and the Fish. But having fun is what it’s all about.

– Tom

Posted in RC Airplanes | Leave a Comment »

I Void Warranties

Posted by Tom Benedict on 27/05/2013

Something occurred to me as I was writing that last post about the video ground station: I void warranties.

The monitor I used came with a little sticker across the two halves of the case. It’s a quality control sticker, but obviously it was put there so the manufacturer would know if someone returned a “broken” monitor that had been tampered with. For a split second, I toyed around with the idea of trying to remove it in one piece. But after practically no thought at all, I decided to let the sticker tear when I opened up the case.

Let’s face it: I voided my warranty. I pulled out their cables, plugged in my own, drilled three new holes in the case, covered up a fourth, and otherwise modified the bejeebers out of it. If it didn’t work at that point, I had no right to send it back under the guise of a warranty repair and say, “Fix this!” For better or worse, the deed was done. They’re off the hook.

And I’m on it. If I can’t handle the idea of having to fix my own electronics, I shouldn’t tamper with them in the first place. I can’t stand the idea of not tampering, so I’d better be ready to fix stuff when it breaks. There’s no shame in this.

But there’s also no hiding it. By all means, open your cases. Change out your wires. Improve the things you use the most. But own up that you did when things break. (And they will, from time to time!) For me, it’s worth it.

– Tom

Posted in Engineering | 4 Comments »

New KAP Ground Station

Posted by Tom Benedict on 27/05/2013

Earlier I mentioned I’d picked up a 7″ Feelworld LCD monitor to rebuild my KAP video downlink. I finally got around to building the ground station to go around it.

KAP Video Ground Station

The heart of it is that 7″ Feelworld LCD. These are meant for wireless video, so they don’t switch to blue screen when the signal glitches, or assume the signal format has changed, and try to automatically re-negotiate PAL vs. NTSC. Those settings are manually done, and if you get static in your signal, you get static on your screen.

The larger size is also easy to see without wearing my glasses. I’m far-sighted, and old enough now that my near vision requires me to use glasses to read. Even using my phone without glasses can be troublesome. My older monitor was nice and compact, but difficult to see without putting on glasses. Unfortunately, once I put them on everything beyond about thirty feet goes blurry. This means I can’t see my kite with my glasses on, and couldn’t read that tiny monitor with them off. But the larger screen on this monitor is easy for me to see, with or without glasses. Problem solved.

I wanted the whole ground unit to be a single compact brick I could mount to my KAP transmitter, stick on a tripod, hand to someone, etc. It required some modifications, but they worked out well.

KAP Video Ground Station Rear

The monitor had a 75mm VESA mount on the back, to allow it to be used with VESA accessories. I made a backer plate for the monitor to house all the stuff I wanted to use with it, and popped four holes on 75mm centers so it could be bolted straight to the back of the monitor without modifying anything. The backer plate houses the 5.8GHz receiver – and doubles as a heat sink for it, and also contains the battery and the main power switch.

The battery is a 2.65mAh 3S LiPoly that was designed for use in an RC transmitter. It’s a 1C battery, so it can only source 2.65A. But the current draw on the monitor and video receiver are so low, I’m not even close to this value. It should provide plenty of juice for a full day of KAP, and charges in about 20 minutes.

I was on the fence about adding the power switch until I tried plugging in the battery and mounting it to my KAP transmitter. Bleah! Talk about awkward. The switch took less than half an hour to pop in, and makes it way more convenient to use.

KAP Video Ground Station Battery Compartment

The battery is held in place with nylon webbing stitched to industrial strength Velcro. The entire battery compartment is lined with fuzzy Velcro for cushioning, and the strap extends almost the entire length of the battery. Plenty of grip to keep things in place in the field. I added a finger tab at the end to make it easy to pull off to get the battery out for charging. (Never ever charge a LiPoly battery in the device!)

KAP Video Ground Station Bottom

In addition to the VESA mount, the monitor also included a 1/4″-20 threaded hole for mounting to a tripod, and a T-slot for mounting to some other rail system. The T-slot worked great on the mounting arm I’d already stuck on my KAP transmitter, so that’s the one I chose to use. But I left the 1/4″-20 socket exposed as well in case I want to mount it to a tripod for easy-chair KAP.

All in all the ground station has worked out great. The reception is far better than with the old system, and since the video doesn’t glitch every time there’s static in the signal, the usable range is huge – far larger than I really need for a KAP video downlink.

Which takes me to the other reason I wanted this to be a removable, stand-alone handheld system: It’s pretty trivial to get a second video transmitter and stick it in an RC airplane. Aaaaah! More fun!

– Tom

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

Lost in Shipping (Bummers!)

Posted by Tom Benedict on 21/05/2013

A couple of months back I ordered three gliders, two of which I’ve built and now flown. (Yes, the Raptor 2000 Advance has now flown! More on that later.) The third never got here.

I like to tell stories about excellent customer service, because all too often we only see stories about poor service. So here’s a shout-out to the folks at Leading Edge Gliders for providing what I consider excellent customer service: I emailed them this morning to ask if my Le Fish had made it into the mail. They replied, saying it had, and that they were boxing up another one to ship to me while they figured out what happened to the first one. All I can say is WOW! They didn’t even ask what happened. They just took care of it. Leading Edge Gliders rocks! (I am seriously looking forward to building this ship now!)

Another order that went missing in the last few months was one from Pololu Robotics. About the same time I placed the orders for the gliders, I placed an order for a new video downlink monitor for my KAP rig. The monitor came in safe and sound, and after I tested it to make sure all my hardware was happy, I opened it up to see what my options were for re-cabling it. As it turns out the cables are connectorized internally using JST XH connectors: a pair for power, and a trio for video/audio/ground. I ordered the three-conductor connectors off of Ebay, and picked up ten sets of power connectors from Pololu. The Ebay connectors came in a couple of weeks after ordering, but the ones from Pololu never made it. I’ve ordered from Pololu for years without incident, and they’ve consistently provided excellent customer service. I figure my number just came up on an un-tracked shipment. I ordered another ten power connector pigtails for $6.80, and called it good.

I placed one last order today. This one’s a bit of a story…

Years ago I picked up a set of plans for an RC land yacht from Performace RC Landsailers. The information on the web site is incredibly comprehensive, and a real resource for anyone wanting to design and build these things. The plans are well worth the price (about $20 US when I got them… not sure what they are now). They’re very complete, and explain the hows and whys of the design and construction of each assembly. I got the plans. But I never built the land sailer.

About a month ago I was poking around in my contacts’ photos on Flickr, and I ran across a set of land yacht photos by Andrew Newton. These are all home-built, and are nothing short of beautiful. That rekindled my interest in building one of these things. After going through all of Andrew’s photos, I pulled up a CAD window and started drawing.

The design from Performance RC Landsailers is tuned for performance. It’s got the weight and strength exactly where it needs it, and not where it doesn’t. This is great, but it makes the design a little daunting for a first time builder. One of the things I liked about Andrew’s designs was how utilitarian and functional they are. We have a saying at work: “Git r’ done!” Andrew’s designs do just that. And that’s what I wanted: a design that would git ‘r done. Everything was designed around what I have on hand: a sheet of 1/4″ Baltic birch plywood; green ripstop nylon from making my rokkaku; 6mm carbon fiber replacement spars for my Bixler’s wing; scrapbox aluminum and Delrin, spare servos, and spare RC radios.

The only thing I didn’t have was the wheels. Both Performance RC Landsailers and Andrew Newton use scooter wheels for their land yacht wheels. What could be simpler? I figured a trip to the local skate shop would set me up.

Nope. “Try one of the big stores in Kona.”

So I tried KMart. Nope. Target. Nope. Walmart. Nope! Sport’s Authority? NOPE! ANYONE?!   NOOOO!

Then I tried Ebay. Yesssss!

I have no idea why it’s so hard to find scooter and skate wheels on this island, but it is. In the end I picked up two white 68mm wheels for nose wheels and four green 100mm wheels for the rear axles. (Yes, I’m building two of these.) I have two yards of green Icarex kite cloth for sails, a whole stack of 6mm spars, and enough Delrin to make a slew of mast steps and goosenecks. With the wheels on order, I’m finally good to go. Like the Le Fish, I’m looking forward to building these things.

– Tom

P.S. The maiden flight of the Raptor! I forgot!

It was… not what I expected. Though in hindsight I should’ve. I only did power-off tests to make sure I had the CG right (I did) and that my control throws weren’t unrealistic (they weren’t). The tests consisted of throwing it from head height, and gliding it in to a soft landing. With 6′ of altitude, it consistently glided over 100′. This thing loves to soar!

What it doesn’t love to do is land. So until I can find a field big enough to learn on, it’s grounded. I think there are some open pastures on Mana Road that might fit the bill, but I need to check them out first. I can’t see flying this thing in town, though.

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

Some OCD Humor

Posted by Tom Benedict on 09/05/2013

It's not the OCD

I swear, doc, it’s not the OCD. I just don’t want to step on this crack!

The lull in my OCD that I’ve been enjoying for the past few years is coming to an end. I’ve seen the warning signs for weeks. I’m back to not letting my foot cross two different kinds of flooring. Back to having to “even out” – when one foot steps on something, the other one has to as well. Back to having to line stuff up and make sure things are symmetric. It’s baaaaack!

As exhausting and frustrating as the compulsions are, it’s the intrusive thoughts that are, to me, the worst side of OCD. I’ve tried to write about them in the past, but inevitably I erase whatever I write and put it off. “I’ll write about it next time.” The truth is I probably never will. It’s too easy for the reader to misunderstand the implications, and the thoughts themselves make even the best Wes Craven movie look dull. They’re not fun, and until they’ve run their course you can’t get away from them.

Which is why it’s important to take the serious parts of your life, hold them at arm’s length, and laugh at them. Call it whistling in the dark. Call it having a twisted sense of humor. Call it whatever you like. I’d rather laugh than cry.

Besides, that really was one big-ass crack in the ground. I had a camera. I had to play.

– Tom

Posted in Tourette Syndrome | Leave a Comment »

RAW from Above

Posted by Tom Benedict on 08/05/2013

There’s a debate that occasionally raises its head in kite aerial photography circles: to shoot RAW or not to shoot RAW. Like so many technical debates, this tends to split people into two distinct camps: those who have real reasons to shoot RAW, and those who have real reasons not to. Often this depends more on the kind of KAP the person does than on what is considered “right” in other photographic circles.

The most apparent deciding factor is whether the person is doing remote controlled KAP or autoKAP. With RC KAP, the KAPer makes a conscious decision to trip the shutter on the camera. With autoKAP, the rig or the camera typically runs an intervalometer that trips the shutter every X seconds. RC KAP sessions may result in anything from a handful of photos to a few hundred. AutoKAP can often result in thousands of photos from a single flight, depending on how fast the intervalometer is running and how long the camera is airborne.

All of which has very little to do with RAW and JPG unless you think about the implication on file storage. For my T2i, a typical JPG is 6MB. A typical CR2 RAW file is 24MB. A hundred frames is only 600MB using JPG. That same session is 2.4GB using RAW. I typically do RAW+JPG, so every hundred frames, I’m looking at 3GB of storage. A lot, but not unmanageable. Not when doing RC KAP, in which a hundred frames is a pretty big haul.

However, if I put that same camera in my panoramic rig running at one frame every one and a half seconds (about how fast it goes) I run out of space on a 32GB card in just under half an hour shooting RAW+JPG. You can start to see the problem here. It gets compounded when you actually start processing the photos. A one hour autoKAP session may run upwards of 60+GB of disk space, and unless you do RAW+JPG there’s no way to proof the photos before committing to processing them. Most RAW workflows get unmanageable once you have that kind of volume going through them.

All of which makes the RAW format look pretty unattractive when doing autoKAP. But what about RC KAP, in which the photographer is intentionally tripping the shutter for each frame? Even then, not everyone sees the need to use RAW. In this case it has more to do with subject than anything else.

Years ago when I was doing large format film photography, I read Ansel Adams’s Technical Series and fell in love with his Zone System. I was attempting to do interior architectural photography at the time. Attempting, but failing most of the time. There were simply too many stops of dynamic range in the subject for me to be able to photograph it with any film I had available to me. Color transparency film only has about five stops of usable range. Color negative has about seven. Black and white negative film typically has ten stops of range, and was the film I used most of the time. But sometimes my subjects – rooms lit by sunlight streaming in through an open window, coupled with dark shadows – presented eleven, twelve, or more stops of dynamic range, all of which I wanted to represent on film.

The Zone System is a method of tuning your developing to expand or contract the tonal range of the film. With some care you can get twelve stops of tonal range out of a black and white negative, and capture detail in highlights and shadows that would’ve been lost with normal processing. Likewise you can compress the tonal range of the film so it would just cover a less contrasty scene, offering more choices when printing the picture.

A JPG file has, by definition, eight stops of range available to it. Each stop represents a doubling of the light being sensed by the film. With digital files, each bit also represents a doubling of the light. Eight bit file = eight stops of range. If your scene contains more than eight stops of tonal range, you’re up a creek. You can push or pull-process film, but you can’t pull or push-process a digital file. Or can you?

It turns out you can. This is what RAW is good for. My T2i makes 14-bit RAW files. 14 bits of data means 14 stops of range. During processing, I can choose what part of those 14 stops are represented by the 8 stops of range in the output JPG. If the scene isn’t very contrasty, I can stretch five or six stops of data to fill the 8 stops I have available. On a more contrasty scene I can do the opposite, and compress the data to fit into the 8 stops of the JPG format.

This is similar to what a photographer does in a positive darkroom. When the negative is made, they use pull or push processing so that the scene they photographed will fill all ten stops of range the film can handle. \When that negative is then printed, they select a paper that will give them precisely the range they need to represent all of the tonal information from the negative on the final print. In this analogy a RAW is like a negative, and a JPG is like a final print.

Not every subject requires this level of processing. If they did, the Polaroid camera never would’ve taken off the way it did. Likewise, for some subjects the in-camera JPG is fine. The benefits in terms of storage, transfer time, ease of processing, etc. means that for some KAPers the JPG is the file format of choice.

But some subjects really do benefit from the additional processing. Here in Hawaii, I routinely photograph a subject that pushes the JPG format past its limits: rocky shorelines. The basalt rock that makes up much of the coast on the Big Island is extremely dark. Foaming surf, by contrast, is extremely bright. In direct sunlight the two present a scene that is several stops wider in tonality than a JPG can handle. The rocks become a muddy blur of black, and the brightest parts of the surf become a washed out white. I’ve lost entire KAP sessions to this effect. For years I didn’t even bother flying at Laupahoehoe Point because the resulting JPG images looked so bad.

It was primarily for this reason that I started using a DSLR on my KAP rig. And it’s for this reason that I use RAW+JPG whenever that camera is flying. Below is a pair of photos from a recent KAP session. The upper one is the in-camera JPG. The lower one was processed from the RAW file of the same exposure.

Why I Like RAW

In the processed RAW image the rocks are slightly darker by my own choice. I could’ve “printed” them at the same tonality as the in-camera JPG, but working from a RAW file gave me the freedom to represent them the way I saw them with my eye .

But the real difference lies in the surf and the driftwood. In the in-camera JPG, all detail is lost. The RAW file showed texture in those parts of the photo, so I tweaked the tonal range during processing so the highlights were better represented in the final JPG.

One criticism I’ve heard of RAW workflow is that it’s difficult to mass-process an entire KAP session worth of photos. But I haven’t seen this as a problem any more than I saw making individual black and white art prints as a problem back in my days of film. After choosing which negatives to work with, I loaded each one into the enlarger and made a test print. Then I went back and decided which paper I wanted to use for each, whether I needed contrast filters or not, whether I wanted to dodge any areas of the print or burn other areas in a little more. I had as much opportunity for artistic expression when printing my negatives as I did when I exposed them in the first place. A picture worth printing was a picture worth printing individually.

To me, working with RAW files is a similar process to printing a negative. I make RAW and JPG files when I’m out doing photography, and use the JPG files as a proof sheet to decide which photographs get further treatment. I’ll load the corresponding RAW files into my software, and then the fun begins. In the end I get a set of JPG files that are individually white balanced, individually adjusted to make the most of the JPG’s eight stops of tonal range, and individually processed to best represent what I saw when I was standing there.

It’s not for everyone. And it’s not for every form of KAP. But I appreciate what RAW workflow has given me when it comes to kite aerial photography. Despite the weight of the camera, despite the added storage requirements and complexity of processing, it’s worth it.

– Tom

Posted in Kite Aerial Photography, Photography | 3 Comments »

Kite Monopole

Posted by Tom Benedict on 06/05/2013

World Wide KAP Week 2013 is over, and despite having to work all week and a bad run of weather, I got out more than I thought I would. I’m not planning to write much about the individual sessions because by and large they were KAP sessions like any other. But I got to play with some stuff that’s worth mentioning, so over the next few weeks I’ll write about them.

The first is the kite monopole.

All this started when my 808 #16D camera arrived. I got it after seeing some stuff that John Wells had done with his, including converting one to do near-infrared photography. My initial thought was to fly it on an RC airplane, positioned so that the airplane played a major role in the video rather than just being the aerial platform the camera was attached to. By taping it to the tail, I was able to see all of the control surfaces on the wing, while watching the plane fly. Too cool!

Having seen that, I knew I had to try it with a kite. So on a whim I decided to put a tripod on top of a kite and tape the camera onto that. The resulting video was an instant recipe for motion sickness! But it proved the idea could work. I just had some stability issues to work out.

I knew that I wanted to try it again during World Wide KAP Week, this time doing stills instead of video. I wound up using a Gopro Hero3 rather than the 808 #16D (which really is a video camera, first and foremost). And this time instead of building a tripod, I made a guy-wired monopod using a replacement spar from Rydra’s and my Widow sport kite. The idea was that this would allow the kite to flex more than the tripod had, and would transmit less of the kite’s motion to the camera. I think it helped, but what really made the difference was that I switched from a Nighthawk (a pretty jumpy high-wind kite) to a large rokkaku (a much steadier flier that can’t handle as much wind).

Gopro Monopod - Setup

Setup was a pain. There’s no other way to put it. Tying and tensioning the three lines to hold the monopod at the right angle was a drag. I arranged most of it at home, including tying the two prusik sliders for the rear legs of the guys. Unfortunately by the time I got to the beach all the knots had slipped, making it a disaster of strings and knots, none of which wanted to slide. But eventually I got everything sorted and let fly.

Gopro Monopod - Let Fly

Then the second problem hit: Without multiple legs, there was nothing constraining the camera to point forward. The monopod rotated around its axis and flopped off to one side. I flew long enough to take about 30 pictures, saw what was happening, and landed it.

Gopro Monopod - Fixing Things

Making modifications to this setup in the field was complicated by my far-sightedness. There is no way to look suave while wearing reading glasses over your sun glasses. Not that I worry overmuch about that kind of thing, but people did get a kick out of watching me tweak this thing. I wound up re-tying the guy wires so they led to the camera rather than to the monopod. This put more of a righting moment on the whole rig, and kept it pointing forward. After that, it was time to fly.

Gopro Monopod - In Flight 1

In the end, it worked! It gave me exactly the view I was after: one that showed the kite in the air as a kite, similar to the video I made using the RC airplane. The idea behind the two was the same: show the aircraft doing its thing, rather than hiding it away. We sometimes get so wrapped up with the idea of using a kite and camera to make beautiful pictures that we forget the kite itself and the way it’s being used are beautiful as well.

– Tom

Posted in Kite, Kite Aerial Photography | 1 Comment »