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Posts Tagged ‘Kite’

Kite Repairs

Posted by Tom Benedict on 17/12/2010

So my Dopero is fixed.  I had this irrational fear it would take weeks to months to get my big red kite back in the air, but it only took a couple of days.

Part of the worry was that I would have to get some exotic parts or fabric things made of pure unobtanium or something from a store that only sold to people who made kites.  Part was that I know I procrastinate to insane degrees at time, and ran a very real risk of letting my kite fall into that category.  (Some might call this “patience” as in  “I have the patience to let my CNC mill sit idle for several years while I get up the gumption to admit I need a new controller!”  I call it procrastination, pure and simple.)  But part of the reason, at least, is that this thing is roughly the size of a small airplane, and my house is roughly not even in the same category as a hangar.

So I set it up at work instead.

I really did.  For some reason my office is the largest one in our building.  That would make me feel like I’m the CEO or Director or something, but no, I’m about as low on the pecking order as you can get.  It all started when half of the technical library was moved into the main library, and space was opened up for two offices.  I was moved in there along with one other technician.  After a couple of years of this the rest of the technical library was moved into the new technical library, so my available office space doubled.

Something strange happened about this time.  Some people in the company got concerned that giving us too much space would lead to inflated head syndrome.  So in a bold move to keep them from putting more people in my office, I arranged all my furniture into an 8’x8′ square like a little fort.  I put my chair in the middle and pretended I was up in a tree.  My office!  It worked, but I think people thought I was weird.  A couple of years later the other tech left the company, and then I found myself sitting in my little fort all alone in the corner of this great big ROOM!

Of course it didn’t last.  Someone else figured this out and moved in enough furniture to house at least three more people.  If you arranged it a little better it would handle four.  Four empty little forts ringing this big room.  Ever since then, whenever we get interns (which we seem to do a lot) they wind up sharing the tree fort office with me.  I like it.  It’s fun.   Those are the good times.  But when the interns all go their separate ways and return to their regularly schedule life, the tree fort starts to feel a little empty, like it is now.

But it’s still pretty handy when you actually need it.  My Dopero is 6′ high by 9′ wide.  This doesn’t seem like it’s too big until you try to set it up in a house and turn it around to get to the other side while trying to fix busted things.  In my office I could basically pick it up, carry it to the middle of the room, spin in place, and put it back down.  It worked like a charm!  I finally got to see the extent of the damage the Kite Killing Kiawe Tree did to it and start to plan my repairs.

Brooks Leffler and Jim Powers gave me some good advice on how to go about fixing the kite, so I took their advice and planned it out.  I had a bent ferrule, which I fixed using the small lathe at work.  This sounds extreme, but it’s a really easy way to fix bent round things:  Chuck up the bent round thing in the lathe chuck, disengage the gears, and spin it around.  The free end will wobble around since the thing is bent, so rotate the spindle until the bent part points up.  Push it down.  Keep doing this until there’s no wobble left.

This is a powerful trick.  At one point we had a disaster at work that bent some precision guide shafts.  I watched our machinist do this to the shafts until the run-out was less than 0.001″ across the entire 12″ length.  This impressed me.  A lot.  I would love to say I held my kite spar to this same tolerance, but I never even came close.  I figure I got it to better than 0.050″ over a 36″ length, but I didn’t measure it.  I just eyeballed it.  As far as I can tell it’s straighter than the other one that didn’t get bent.  Go figure.

The other damage was that the bow lines ripped out of the upper and lower sails.  Brooks told me to sew some #200 braided Dacron onto the pocket and run the bow line through the loop.  Keep in mind I’m an absolute ditz at sewing, and that my sewing machine can’t actually be set to the right bobbin and thread tensions to sew ripstop.  (Believe me, I tried.  Over and over and over.  I know I growled a lot and my cats hated me for a while.  But I never could make a kite on that machine.)  So even though this seemed simple in theory, in execution it was going to be something of a feat.

Some time in the middle of this whole process, when I was taking trash and recycling to the transfer station, I saw that someone had dumped a Singer Millenium Series sewing machine.  “GREAT!” I thought, “Now I can sew ripstop!”  I threw it in my car, drove to work, and rubbed my hands with glee!  I knew it might need adjustment or something, but hey, I do machining.  How hard can it be to service a sewing machine?  (Yes, I’m aware this is an incredibly naive statement on par with, “It’s just a nuclear reactor.  How hard could this be?”  Actually, I think sewing machines are more complicated than reactors…)  I figured I’d fire it up, run some cotton denim through it to find out what the deal was, and fix whatever needed fixing.  It wasn’t until that evening that I realized the flaw in my plan:  It had no pedal, no power cord, no nothing.  Unless I could get it to absorb AC power through mind power or some sort of osmosis, it wasn’t going to be any more useful than a doorstop.  Ah well…  Project for another day.  (See?  I really do procrastinate.)

In the end I finally did take Brooks’s advice, and sewed some #200 braided dacron across the pockets.  I couldnt’ do it with the Singer or with my older sewing machine, so I did it by hand.  Hey, don’t knock hand sewing.  It’s how clothes were made for thousands of years.  The whole lock stitch machine only came about very recently by historical standards.  And even I can hand sew!  (Well, sort of.  It looks more like a really crude kid’s drawing of sewing rather than the real deal.  But it holds!)  It took me a while, and I had to wear my headset magnifier to see well enough to get the job done, but the job finally did get done.

I took my kites into work this morning, and when lunch time rolled around I pulled out my Dopero (nicknamed “Porco Rosso” after a character’s airplane in a Miyazaki movie by the same name), hooked it onto my line, and gave it a test flight.  It flew great.  As good as new.  You can’t beat that.  And if I can get a Singer pedal I might just have a new sewing machine sitting out in the garage.

– Tom

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Don’t Divide Your Attention!

Posted by Tom Benedict on 14/12/2010

I had a mixed weekend for KAP.  Saturday I went up on Kohala to do some aerial photography of a property that’s set up to demonstrate sustainable agriculture and architecture.  I had an absolute BLAST!  The wind was perfect, which Kohala rarely is.  The light during the first half of the flight was fantastic.  And after the KAP work I got to use the new pole rig I’ve been building out to finish up the last of the required shots in the remaining light.  The owner of the property is a wonderful person, and we both had a great time.  It’s really tough to put a damper on that:  Great KAP, great kite flying, great light and landscape, and great company to boot.  I hope I have the opportunity to work with him in the future.

Sunday morning I spent re-working one of the images from the Saturday session so I could get it back out for distribution.  I charged batteries, cleaned out my memory cards, and got my gear ready to go again.  3:30pm rolled around and the whole family jumped in the car to go to the beach.  Hey, this is what I was getting my gear ready for!

The wind at the beach was minimal, but enough to fly a Dopero in.  I got my Dopero airborne and on a whim I pulled out my rokkaku as well.  Some weeks ago there was a great thread on the KAP Forum regarding kite tacking.  I did some experiments with the upper bridle Y on my rokkaku, and demonstrated that you could repeatably tack a rokkaku by upwards of +/- 20 degrees.

Offset Flying

This photo demonstrates a Flow Form 16 used as an unmodified “control” kite in conjunction with a 6′ rokkaku with a 2″ offset in the bridle, tested symmetrically on both sides to make sure the offset is real, repeatable, and symmetric.

The idea works.  But a fellow KAPer, Simon Harbord, cautioned against jumping into this whole-hog.  He reasoned that by adjusting the bridle to fly the kite out of the center of its wind zone, you are reducing its performance bye a measurable amount.  Until the kite flier has a considerable amount of experience flying under these conditions, they won’t really know what the flight characteristics of the kite are when used in an offset fashion like this.  He’s right, and the first real opportunity I had to make use of kite tacking, I opted to wait for more favorable conditions rather than risk the safety of the people around me with an unknown and untested setup.

So when I got my Dopero airborne, I put my rokkaku together and did a 1″ offset on the bridle before putting it into the air.  The rokkaku flew fine, though the wind was slowly declining throughout.  In the end the Dopero was coming down, so I opted to land both kites.  The rokkaku stayed offset to the left the entire time with no chance of collision, though I had to stop reeling it in from time to time to pump the Dopero back up into the air.

Just as I was about to land the rokkaku, my wife walked up and asked me to keep an eye on our kids while she was rinsing off.  Ack!  I did a quick eye-check on the kids, landed the rokkaku, and looked up just in time to see the Dopero settle into a kiawe tree and rotate 180 degrees into it, locking it into place.  There was to be no flying it back out of the tree.

Before going into the rescue operation, a quick aside about kiawe trees.  They’re local to the Hawaiian Islands, but they’re related to the mesquite trees of the southwest United States.  Think of the thorniest tree you can imagine, then add some more thorns for good measure.  Then make it thirty feet tall and put your kite at the top of it.  That’s where my kite was stuck.

Even before I started the rescue operation, I had made up my mind not to lose this kite.  It’s $250 worth of gear, and it’s my primary light wind kite.  I pulled out my 16′ carbon fiber pole from my kite bag and headed over to figure out how.

Another quick aside about climbing trees to get kites:  Mostly I advise that people don’t.  It’s easy to fall from a tree, and any fall from a height of more than six feet can cause permanent injury or death.  Take it seriously.  It’s a quick way to be maimed for life.  I did climb the tree high enough to get me into range of my kite, but not without considering the risks and realizing I could do it without putting myself in any real harm’s way.  I always had at least two fallback branches below me in case the one I was using snapped, and the trunk was strong enough to hold up my car.  (I weigh less than my car.)

I spent the next hour using a hook at the end of my CF pole to unwrap the kite’s bridle from the tree’s branches and thorns.  I then spent more time shoving it and jockeying it until the kite sail was clear of the tree and was within reach of the ground via the pole.  Then I climbed down and used the pole to pull the kite sail to the ground.  In the end I broke the tie points for both bow lines, I broke one sail line, and I ripped off several small branches that had become entangled in the kite bridle despite my best efforts to keep it clear.  The sail itself appeared to suffer no lasting harm, but there’s still a couple of hours of repair work on the kite before it will fly again, and then the whole thing needs to be re-tuned.

All because I divided my attention at a critical moment.  Lesson learned.  Next time this happens I know how to respond:  “Can you give me just a sec to land these kites before I watch the kids?”  It really would’ve been that simple.  As I carried the rolled up wreckage of my Dopero back to my kite bag, my arms and legs scratched from the kiawe thorns, I couldn’t help thinking, “You IDIOT!”  I have a hard time calling something an accident when such a small dose of common sense would’ve avoided it.

It’s not just kid watching that causes this.  Phone calls, conversations, turning your attention to a battery change or to dig something else out of a KAP bag.  Any one of these could’ve caused what happened.  When your kite is in the air, pay attention to the kite first and foremost.  Don’t divide your attention.

– Tom

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No KAP, Just Kites

Posted by Tom Benedict on 09/12/2010

It’s been a rough couple of weeks at work.  We’ve had issues with a couple of our instruments, and we’ve been going at them pretty ruthlessly.  My days have more or less consisted of waking up, making coffee, going to work, cranking hard, coming home, eating dinner, doing the dishes, and going to bed.  Not much joy there.

Last night I came home just after the sun had set, but still about an hour and a half before dinner time.  There was a gentle kona breeze, it wasn’t too cool outside, and my kite bag was right there.  Forget cleaning up the living room!  I grabbed my bag and went outside.

The wind on the ground was pretty minimal, but I got my 6′ rokkaku airborne and climbing high without too much trouble.  As the sky darkened, I eventually lost sight of the kite.  I just had this line stretching up into the night sky.  Of course I had to play!  One of the kids went inside and came back out with one of our book lights.  We clipped it onto the line and sent it aloft like a little wobbly star of its own.  Things got pretty dim up there, but we could still see it even after the sky was pitch black and the kite was nothing more than a hint and a mystery.

We all had a blast.  No cameras, no KAP rig, nothing but kites and a sense of fun.  Night kiting is really cool!  The book light survived the flight with flying colors, but it left me wondering if I could get some small lights to tack onto my kite sail.  I did a Google search and found some nice magnetic blinking LED earrings that would attach to a kite sail with ease.  I was all set to order them when my wife showed me something even cooler on the Into the Wind site:  Glowire.  It’s electroluminescent “wire” that you plug into a high frequency source (9V battery plus a high frequency inverter) which then glows like neon.  The kit sold by Into the Wind comes with the inverter and two five foot lengths of EL wire.

I begged Santa to remember I really had been pretty good this year, and that coal was hard to come by in Hawaii.  Then I mentioned to Santa that my AKA membership got me a 10% discount at Into the Wind.  Santa let me place the order.  But I promise to act suitably surprised when I open it!

It looks like we’re going to have gentle kona winds again tonight.  Lights or no lights, I’m getting out with my kite.  It’s a great way to end the day, regardless of how the day itself went.

– Tom

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Stay Safe

Posted by Tom Benedict on 01/12/2010

I have the dubious honor of being the person at work who has filed the most injury and near-miss forms.  It’s reached the point where my boss doesn’t even want to see me approach the first aid kit, and my co-workers nicknamed me “Bubble Boy”.  But hey, the point of the paperwork is to bring any and all accidents or potential accidents to the attention of our safety committee so they can look at what happened and see if there’s a way to prevent that kind of injury in the future.

Sometimes the changes are small.  Here’s a good example:  At one point I injured myself while using our small mill because the right-hand crank for the table came a little too close to a toolbox.  My hand whacked the toolbox, and a good 2″x.5″ patch of skin was removed from my hand.  It hurt about as bad as that sounds.  The fix?  Move the #$%@ toolbox 8″ to the right!  Done.  No real cost, and no repeat of that injury in over seven years.

Other times the changes are more involved.  But not often.  Most of the changes really are small.  It really doesn’t take a lot to be safe.  Just a little common sense.

And with that introduction, let me introduce you to my latest injury:

Gloves are good, but...

It’s not work-related this time.  This was 100% me.  If you can believe it, it’s a kiting injury.  Consider this:  Even a modest kite can put upwards of ten pounds of force on the kite line.  Under that kind of force kite line starts to behave like an abrasive hacksaw.  Common sense says wear gloves when working with kite line.  I do this regularly, and keep a pair of leather gloves in my KAP bag for just this reason.  And you’ll notice in the photograph above, my hands are injury-free.  I was wearing my gloves!

But my arms weren’t.  I also tend to wear a beat-up old cotton work shirt when I’m out doing KAP.  But this time I was wearing short sleeves.  The wind picked up, the kite started to pull harder and harder, and I had to bring it down.  Two of us got on the line with our leather gloves, but it was still a struggle.  I wrapped the line around my elbow to get a little more purchase on it, and the line slipped.

Common sense, right?  Not so much.  I’ve seen people make the same move with rope, fishing line, all kinds of stuff.  I’ve even seen one kiter proclaim that using this maneuver means the line cannot slip, and that he therefore doesn’t need to wear gloves at all.  From first-hand experience I feel safe in saying:  BALONEY!

Whenever you put your hand on a rope, string, line, cable, chain, etc. you must assume that it will at some point move.  The line could fail and the suspended weight could pull it through your hand.  The wind can change and the kite will pull the line through your hand.  The thing your rope is attached to might unexpectedly move, and will pull it through your hand.  Insert scenario X, Y, or Z, and they all come back to this:  No matter what you do it can move.  Do it enough times and eventually it will.  If you’re not protected, you get hurt.

Such was the case here.  The line slipped, I got a nasty rope burn from #200 Dacron line, and from now on I won’t pull that maneuver unless I’m wearing long sleeves.  Lesson learned.

Stay safe, folks.  Even when you’re just flying a kite.

– Tom

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Nokia N8 PUSH

Posted by Tom Benedict on 24/11/2010

Some months ago Nokia put out a call for proposals for how to use a KAP rig based around a pair of N8 phones.  At the time I’d been doing some KAP with a photographer in Kona with the goal of photographing whales in the ocean.  So I had whales at the front of my mind.  It wasn’t too much of a stretch to come up with an idea that involved doing KAP of whales.  I sent the idea in, but didn’t really expect to move forward with it.

Turns out I was wrong.  My idea was selected, and not long ago I was contacted by the N8 PUSH team to let me know.

??!  !!!  COOL!

There were some questions to answer and some details to be worked out, but everything came out ok and in the end I was given the timeline and was told to expect a package in the mail.  There’s no curbside delivery where I live, so I’ve been swinging by the post office to check out my PO box ever since.  Nothing yet, but it’s getting clooose!

The package should contain two Nokia N8 cameras, each sporting a 12MP camera with a fixed focal length Carl Zeiss lens, along with a KAP rig designed specifically for the N8, and a kite.  The two phones come loaded with the N8 KAP application, which allows the KAP rig to be controlled from the phone on the ground, and for the aerial phone to stream its video signal to the ground phone.  All in all a seriously cool setup!  I was a little skeptical of the camera at first, but hearing the Zeiss name and seeing a video clip of the camera focusing (yes, it actually focuses) went a long way toward laying those concerns to rest.  What finally did my concerns in was seeing a set of KAP images made by Ricardo Ferreira with the N8 phone.  The image quality was better than most point and shoot cameras, and worlds better than any phone camera I’d ever seen.  (For anyone who’s not familiar with KAP and with the KAP-Nokia connection in particular, Ricardo is an excellent KAPer, and developed the first Nokia KAP rig, based around the N900 phones.)

Operationally, this will be a significant change from the way I’m used to working in the field.  I don’t have a video downlink on my current rig.  The N8 rig does.  I can do movies with my current rig, but I tend not to.  In any case 640×480 is as good as I can get with my current camera.  The N8 does 720p HD video. Right now I don’t have any way to get GPS information for where my camera is in space.  Yeah, I can add a GPS photo tracker to my rig, and probably will in the not so distant future.  But the N8 phone has GPS built in, of course.  I just hope the EXIF headers on the files include the GPS information.  Even the rig itself is different.  I’m used to plugging in cables, screwing down cameras, attaching safety lanyards, and the like.  To use the N8 rig, you snap the phone into the rig and you’re done.  From what I’ve gathered, the aerial phone controls the rig via a Bluetooth connection.  No wires, no screws, no nothing.  And no legs!  The rig has no legs.  But the way it’s shaped, it really doesn’t need them.

So in addition to the PUSH project itself, I’m interested in seeing how the N8 rig behaves in the field.  I’m planning to give it a thorough shake-down and post a review here and on the KAP forums.  Luckily, there’s still some time before the whales come through the Hawaiian Islands.  So I’ve been picking out some likely flying spots where I can put it through its paces and see what it’s got under the hood.  High on the list are Kiholo Bay and Puako.  I’d love to give it a try at the summit of Mauna Kea, but cell phone signals really do mess with the radio telescopes up there.  So it’s a no-no.  Waipio Valley and Pololu Valley are also high on the list since they offer some of the more challenging wind conditions for doing KAP on the Big Island.  (Besides, on the drive back from Pololu there’s a fantastic deli in Hawi called Lighthouse Delicatessen.  Can’t beat a KAP session that ends with a great lunch!)

By the end of the land-based sessions, I should have a better feel for how the rig handles, I’ll have some seat time with it on a couple of different kites, and I’ll be ready to trust myself to launch it off the back of a boat.

Now all we need is whales!

– Tom

Posted in Hawaii, Kite Aerial Photography, N8 Push, Photography | Tagged: , , , , , , , , , | Leave a Comment »

Challenging but Rewarding

Posted by Tom Benedict on 17/11/2010

I recently had a pair of flights that yielded really nice results.  The first was done just on a whim.  In the past I’ve flown at Mala`ai, the culinary garden at Waimea Middle School in Kamuela, Hawaii.  I like flying there for a number of reasons.  It’s a pleasant place to fly with no ground hazards or obstructions, it’s a great place to try out new ideas for orthoimaging, it’s an interesting subject, and the school uses the images to help plan future work in the garden.  One of the coolest things about the garden is that it’s largely the students who do the planning and the work.  And boy do they ever move FAST!  I’ve never photographed it twice and seen the same thing.  It’s constantly changing.

But almost every time I’ve flown there, I’ve underestimated the size of the place!  The field of view on my camera’s lens is such that the field of view on the ground in the horizontal direction is almost exactly the same as its altitude.  This helps me compose shots when doing orthoimaging.  But vertically the field of view is smaller, and in the past I’ve clipped.  This time was going to be different!  I’d fly high enough to get the whole thing in one shot!

And in the end I did:

Mala`ai - The Culinary Garden at Waimea Middle School - 11 November, 2010

This is still a composite image because I wanted to be able to rotate it to line it up better with the edges of the frame.  But there are no stitch errors inside the garden that needed attention.  The garden itself came from a single image.  As soon as I’d processed the image I let the folks at the garden know there was a new image to download.

About a week and a half ago I got a call to ask if I could photograph the Anuenue Playground in Kamuela, as well.  I’ve wanted to photograph the playground for years, but there are a number of ground hazards and obstructions that have made it less than ideal.  Even though the adjoining football/baseball field doesn’t have lights any more, the poles that used to support them are still there.  There are large trees near the park.  It’s bordered on two sides by busy roadways.  And worst of all the park is full of kids!  I have never had a rig fall off my kite line, but that doesn’t mean I don’t believe it can.  So a great deal of additional paranoia was called for.

I surveyed the place a couple of times that week, trying to find a good angle to launch and approach the park.  But depending on the direction of the wind I could add above ground high voltage power lines to the list of ground hazards.  No thank you!  It looked like the only reasonably safe approach was for the wind to blow out of the west-northwest, and for it to be super-steady.  I didn’t even bother to call back to let them know.  I felt like a failure.

Two days after I made the garden picture, I checked the wind models.  Lo and behold, the afternoon called for soft and steady winds out of the west-northwest!  Sure ’nuff, by 2:00pm the winds had shifted and the conditions were ideal.  I waited out an event that was happening in the football field, my chosen launch spot, but by 3:30pm the coast was clear.  I put up my Fled, put my camera in my ortho rig, and got it in position.

There’s one other piece of KAP gear that figures prominently into this session: my son.  I knew I’d never spot it on my own, so I asked him to grab his walkie talkies and come with me to the park.  He got on the radio and guided me in, and I checked my apparent altitude against the footprint of the park on the ground to make sure I had the field of view to get everything.

I came close.  There’s one apparatus in the park that didn’t make it into the photo set, but the rest of the park did:

Anuenue Park, Waimea

I didn’t get enough overlap for a clean crop, but it covered the bulk of the park with reasonably sharp detail.  A quick pass through PTLens to take out barrel distortion and a small amount of tilt, and then a pass through ICE to make the composite, and the image was done.

All in all the camera was in the air for only 14 minutes, taking pictures every five seconds.  The resulting set of images offered a rich selection to work from.  I feel confident that as the restoration work on the park progresses, I’ll be able to return and make additional documentation photos for them.

Can’t beat a good day.

– Tom

Posted in Hawaii, Kite, Kite Aerial Photography, Photography, Weather | Tagged: , , , , , , , , | Leave a Comment »

Catching Up

Posted by Tom Benedict on 15/10/2010

I missed most of Worldwide KAP Week 2010.  A few weeks previous I’d come down sick with a cold, and just never quite shook off the cough.  It didn’t help that my job took me to the cold dry air at 14,000′ elevation over and over (and over!) during and after the cold.  In the end I came down with walking pneumonia.  This left me with no energy and a wracking cough through most of WWKW 2010.  I did get out, I did send pictures in to the book, but it wasn’t the happy time I’d planned.  C’est la vie.  Until next year.

In the end I was sick for well over two months.  I finally got my clean bill of health today, and should return to duty at the summit tomorrow morning.  Meanwhile I’ve been working on a cryostat at headquarters, and finally started flying kites again about a week ago.  Unfortunately all this came together in a not so comfy way today.  It all ended well, but getting to the end of the day was a trial.

At lunch I broke a spar on my Premier Kites Widow.  Plain and simple.  Dumb crash, dumber re-launch, and now I have to cut a new P-200 spar once I get home.  Thank goodness for spares!

The real fun has been this cryovessel.  I was testing the idea that you could boost the performance of a closed-cycle cooler by using thermoelectric coolers, or Peltier junctions, between the closed-cycle cold head and the cold surface.  It worked, after a fashion, and I think it bears re-examining with a properly sized cascaded Peltier junction.  But for our application I just couldn’t get enough cooling power out of the thing to get the delta-temperature I was after.

During this testing I wound up putting something like 30W of power through a two-stage cascaded cooler, but the cold head simply couldn’t remove the heat fast enough.  Within a few minutes I had a cold head at -150C, a cold surface at -100C, and a Peltier junction at a soaring 38C.  I killed power, brought everything back down, and let things hit steady-state before killing the power to the cooler.

What that told me, though, was that the biggest delta-temperature in the system was across the link between the cold head and the cold surface.  I also realized if I minimized the dT, I could switch the gas in my cooler and possibly hit my target temperature that way.  Time to make new parts!

So I replaced that link with a new one.  The old one consisted of ten strips of 6.5″ x 1.0″ x 0.010″ copper in a nice neat stack, or 6.5″ of 0.100″ sq in copper.  I replaced it with 2.8″ of 1.5″ diameter copper.  At 60W of load the first one got me about 52C dT.  With this new one I should be able to keep that under 2C of dT.  If the cold head reaches its ultimate temperature of -158C, this should give me a cold surface temp of -156C.  If that happens, I can change gases and potentially hit the 77K, or -196C temperature I’m after.  Time will tell.

For the record, I hate machining copper.  Oxygen free high conductivity copper is even worse.  It’s like machining stale bubblegum.  Tools dig instead of cutting, the copper oozes out of the way instead of making nice chips, and it takes all manner of tricks to pull off clean cuts.  I got the parts made, but the final steps of tapping the M3 holes in the thing gave me the willies.  After a thorough cleaning, I opened up the cryostat, installed the new parts, and closed it back up.  It’s on the pump now, and I should have a chance to start cooling it over the weekend so I can work with it on Monday.

But what I’m really looking forward to right now is a new spar for the Widow, a weekend of good weather, and a chance to get out and make up for what I missed during Worldwide KAP Week 2010.

– Tom

Posted in Engineering, Kite, Kite Aerial Photography, Machining | Tagged: , , | Leave a Comment »

Worldwide KAP Week 2010 Begins!

Posted by Tom Benedict on 10/09/2010

If you’re active in the world of kite aerial photography, chances are you already know Worldwide KAP Week 2010 starts tomorrow.  It runs from Saturday, September 11th, through Sunday, September 19th.  (Yes, that’s also “Talk Like a Pirate Day”.)  If you already have KAP gear, get out.  Wherever you are, get out over the next nine days and fly a camera.  Take pictures.  Have a good time.

As for me, I’m taking the entire week off from work.  Some people think that’s silly, but it’s one of my only opportunities during the year to really get out and dedicate a big chunk of time to doing KAP.  Looking back at the pictures I made during Worldwide KAP Week last year, and everything that’s happened since, I have a pretty positive feeling about WWKW 2010.  These are the big changes in my gear and technique:

  • I picked up a Dopero early this year, so I can fly a heavier rig in lighter wind.  From 3.5kt to 25kt, I’ve got my kites covered.
  • I’ve worked a lot on my panorama technique, added a Ho/Ver axis to my rig, and hope to make a number of good, printable panoramas.
  • I’ve also worked on my sunrise/sunset/golden-hour photography, and hope to work in better light during WWKW 2010 than I did during WWKW 2009.
  • Finally, I’ve been experimenting with graduated ND filters in the air.  I think this is the last tool I use for landscape photography on the ground that hasn’t been available in the air.  Now it’s all there.

I’ve got spots picked out all over the island, and a list of subjects longer than I can handle.  So no matter what, I doubt I’ll come away from WWKW 2010 disappointed.  It should be good.  I checked the weather and wind for tomorrow morning (my first sunrise outing ever!) and it looks like there should be nice wind on Mana Road.  Some years back I did an early morning session on Mana Road, and came away with some nice pictures.  But the foreground was too dark, and the clouds over Mauna Kea were blown out.  This time I have tools for dealing with challenging lighting, so I hope the pictures will be better.

I can’t wait!

– Tom

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Panorama Workflow

Posted by Tom Benedict on 23/07/2010

I’ve had some opportunities to play with my camera on the ground as well as in the air, and to test a number of image sets on the software I’ve been using.  Two days ago my wife and I took our kids to Pololu Valley to go hiking.  On the off-chance the weather would be nice, I brought my KAP gear.  The weather was fantastic, with solid winds for kite flying, and beautiful partly-cloudy skies.  Time to play!

I ran about 5GB of images through the camera from various vantage points.  In creating the base images I tried to incorporate everything I had learned from the earlier experiments.  The resulting photographs turned out quite well, so I’m considering the new workflow to be a win.  I’m sharing it here in the hopes that someone else doing kite aerial photography will give it a try and take it even further.  Here are the details:

  • If you can shoot RAW, shoot RAW.  I can’t, but in the near future I’ll be able to.
  • Use Manual Exposure mode on your camera.  Set it on the ground, check it, and double-check the histograms to make sure you’re getting bullseye exposures.
  • Use at least 1/1000 second exposure speed.  I’m using 1/1250.
  • Use the slowest ISO setting you can to control noise.  This is of less concern with a DSLR, but every bit helps.  I made this set at ISO 80.
  • Use the sweet-spot aperture on your lens if possible.  My lens is sharpest around f/4 to f/5.  I couldn’t use this aperture and hold the other numbers, so my lens is wider than ideal.  But the benefits in noise at ISO 80 make this a reasonable choice.  I give up some sharpness for lower noise, and keep the fast exposure speed to avoid blur.

Once the camera is in the air, all my panoramas were made with the camera vertical.  With a KAP rig this either means building the rig around a vertical camera (Brooxes BEAK rig), or using an L-bracket on a conventional rig, or having a dedicated Horizontal/Vertical axis on the rig.  I recently modified my rig to add the HoVer axis, so this is the route I went.

The idea with this technique is to start the rig on a slow spin, and to trigger the shutter continuously.  This technique was developed by a French KAPer who goes by the name of Vertigo on the KAP forums.  With a sufficiently fast shutter speed, this works perfectly.  My A650IS does one frame every 1.1 seconds.  With a 10-second-per-rev rotation rate, this works out about perfectly.  I’m upgrading to a Canon EOS T2i DSLR in the near future, which has a much faster frame rate.  I’m planning to build an electronic release cable for this camera that will give me the same 1-frame-per-second rate my A650IS has so I can continue to use this technique.

  • Start the rig rotating at a rate that gives you adequate overlap between images, and minimizes motion blur from the rotation, given the camera’s shutter speed.
  • Once the camera is rotating cleanly (no see-sawing on rotation, no jerkiness in the pan axis, no swinging around, etc.) trip the shutter.
  • Make at least two complete orbits of the camera, tripping the shutter non-stop the entire time.  This is for a couple of reasons:  First, it gives you plenty of frames to choose from in case one is blurry.  Next, it gives you a range of random tilt angles that you can use to fill in gaps later on.  Finally, if the rig starts to move, the second orbit will still produce a clean panorama.
  • If you want to make a larger panorama, change the tilt after two orbits and make two more orbits at the new tilt value.
  • While all of this is going on, do everything you can to minimize camera motion.

This should produce a nice set of images from which to work.  You may well end up using them all, so don’t toss any of them!

I use Autopano Pro for stitching.  Some of the tricks I’ve picked up will apply to other packages.  But if you find yourself scratching your head and thinking, “No, I’ve never seen that,” don’t sweat it.  Your software is different.  Skip that part.

One of the first problems I ran into is that Autopano Pro deals really well with point features, but not very well at all with linear features.  For example, it’ll match up individual stones on a beach like a champ, but it will produce lousy horizons if the horizon is just water and sky.  It makes no effort whatsoever to correct for lens distortions if the bulk of the picture is water and sky.

The fix I found was to use PTLens to correct lens distortions before using Autopano Pro.  PTLens is a $25 plug-in for Photoshop.  Even better, it’ll run as a stand-alone program and will batch process hundreds or even thousands of images at once.  If you’ve got a block of images you photographed as fodder for panorama stitching software, it’s no problem at all to batch process them all to remove lens distortions.  Water horizons should now be ramrod-straight lines across the frame.

So back to the process:

  • Run the entire image set through PTLens to remove barrel distortion, vignetting, and chromatic aberrations, but nothing else.
  • Process the images with Autopano Pro, or the panorama software of your choice.
  • Do everything you can to get completely horizontal, completely straight horizons for water.  Nothing kills a pano faster than a grossly errant horizon.
  • Save as 16-bit TIFF images.  16-bit workflow can be a real PITA, especially on a smaller machine, but it hides a lot of ills when it comes to large-scale processing like Levels and Curves.

At this point I open up the images in Photoshop.  I’m still using Photoshop 7.  I’ll upgrade to CS5 as soon as I can afford it.  But for now it still does everything I need.  Want is a whole ‘nuther story, but as far as my needs go, it’s fine.

  • View 100% and check for stitching errors.  Repair all of these with the rubber stamp or heal tools.
  • If your kite line shows up in the image, remove it using the same tools.
  • If you cropped your panorama wide enough to have gaps in ground or sky, open up all the images that went into the panorama, as well as the second orbit you made from that same location.  Use the rubber stamp tool to pull patches from any and all of the input images to repair problems on the panorama.  (This is one of the best reasons to make a second orbit!)  Since you used a fixed exposure, you should be able to rubber-stamp these into the panorama with no changes necessary.
  • Once the panorama is defect-free, look at your levels.  If you did your job setting the manual exposure on the ground, the exposure should be dead-nuts on, or need very little tweaking.
  • Do all your dodging and burning at this point to get the exposure just the way you want.  This can involve lots and lots of time, depending on how meticulous you are with your exposures.  If you’re the kind of person who got into photography in the days of film, and spent your afternoons in the positive darkroom dodging and burning the same negative over and over and over, you may be on this step for a while…

At this point the bulk of the workflow is complete.  But I would advise you not to stop here.  In Photoshop under the File menu is a command called File Info.  Click it.  It lets you edit the header information associated with your image.  At the very least I would fill out:

  • Title – What is the name of the original file on your computer?  Leave out the extension since that can change without changing the image.
  • Author – Your name.  You’re the author of your image.
  • Caption – Describe the photograph clearly and concisely, and include enough information so that you could read it and know where on the planet you were when you made the photograph.
  • Copyright Status – Change this to “Copyrighted Work”.  The moment you tripped the shutter, your photograph was a copyrighted work.  Not marking this just sets you up for someone to use your photograph without your knowledge.  If you choose to license your photographs under the Creative Commons license, of course, you should set this appropriately.
  • Copyright Notice – Mine reads: Copyright © Tom Benedict
  • Date Created – The date you tripped the shutter on your camera to make the photographs that went into this image.
  • City / State / Province / Country – Fill them in.
  • Source – Give yourself some hints here.  Is it a straight shot?  Digital?  Film?  Stitched?  My digital panoramas are all marked “Digital-Stitched”.

The neat thing is that most of the photo sharing sites on the Internet will automagically read your header information and fill in their own forms for you.  You may still want to provide more information than this, but the base information will be there.

The even neater thing is that in the event someone downloads your photograph and puts it on their own site without your knowledge, your header information is indexed by most search engines.  Even better, when you challenge them and they claim the photograph as an “orphaned work”, you can demonstrate that they did not make an honest effort to find the photographer in order to ask for permission since your info is all right there with the image.

So that’s it in a nutshell.  How well does it work?  See for yourself:

Pololu Valley Wetlands 2

– Tom

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The Good and The Bad

Posted by Tom Benedict on 09/07/2010

The 2010 SPIE Astronomical Instrumentation conference was a blast.  We worked some seriously late hours, and all of us were dragging our tails by the end of it.  But the amount of information I came home with was…  for want of a better term, it was astronomical.  But that’s a post for another day.  This one is about the KAP I managed to do while I was there.

“Managed” is the right word to use in this case.  Sunset was at 8pm, and the only full day I had to do KAP was the Saturday before the conference.  I had some problems with my flight, so most of that day was lost.  Even so, it was the most productive day I had, from a KAP standpoint.  I wound up staying at the Porto Vista Hotel in Little Italy.  I highly recommend it for a couple of reasons:  1 – It’s a nice hotel.  That’s tough to beat.  2 – Close proximity to a lot of good KAPing.  3 – It’s in Little Italy!  As it turns out it’s also close to a camera store, which I didn’t visit, and a Blick Art Supply, which I did.  Twice.  It’s about a two minute walk to the nearest trolley station, and it’s only a few blocks from the Maritime Museum, which boasts some outstanding KAP subjects.  Unfortunately none of the KAP I did there really worked out.  This is the best of my efforts:

Maritime Museum

Further down, there were a number of other good subjects.  Some I wound up photographing with a pole, others with a kite.  By far the best KAP I had in San Diego was at the marina at Seaport Village:

Seaport Village Marina

The wind was steady enough to let me do some panoramas as well, one of which turned out nicely:

Seaport Village Marina Panorama

Heading back toward the hotel is the USS Midway and the statue, “Welcome Home”, which I photographed using a carbon pole:

Welcome Home

If you’re already taking framed kites with you, I highly recommend bringing a lightweight pole as well.  The carbon pole I use is a collapsible fishing pole intended for breem fishing.  It’s far from ideal, and the performance isn’t up to that of the higher end carbon fiber carp poles.  But it’s light, it’s portable, and it only cost me $20 at K-Mart.  I had no problems transporting mine, but even if it did take damage, it was cheap insurance against poor wind or restrictions on flying.  It also let me do some night photography in and around Little Italy:

Fountain in Little Italy, San Diego

Little Italy at Night

The only time I flew once the conference began was on a day when there weren’t any afternoon sessions I really wanted to attend.  Instead I grabbed my gear, got on the trolley, and headed over to the SDSU campus.  The wind was plenty strong, the weather was clear, and it should’ve been a fantastic KAP session.

It wasn’t.  The wind was strong but turbulent, and before I even got a camera up, my Dopero inverted.  I was in the middle of setting up my rig, so everything was clipped off.  I frantically tried to unclip my winder and line in time to let line out and try to save the kite, but I was too late.  The line came down across the Malcom A Love Library.  My heart sank!  I had no way of telling if the kite had hit the roof, or the glass dome just beyond.  I felt like an idiot.  Overwhelmed with dejection, I packed up my gear, reeled in the line, and walked over to see what the damage was.

Lo and behold, there was my kite dangling about halfway down the side of the building.  It was out of reach of my pole, but to my immense surprise it had inverted again just before landing, so it was sitting nose up!  In case you’ve never seen a Dopero, one attribute of this beautiful kite is that it is extremely stable.  Once it’s pointed in a given direction, it really likes to go in that direction.  It’s a little sluggish on reacting to changes in wind direction, which is one of the things that makes it an excellent kite for KAP.  I knew if I put some tension on the line, it would try to fly.  More to the point, it would try to fly straight up and off the library.

I went back out to where I’d been standing, took up all the slack I could, and heaved.  The tension in the line built as it stretched, then I felt two distinct yanks as the kite cleared the far side, and then the near side of the building.  A little shaken, a little wiser (I hope) I brought my Dopero down, packed it away, and sweated for a little while.

In the end I changed winders and switched to a 6′ rokkaku.  It wasn’t enough to lift the camera reliably, but I got some decent low-altitude KAP:

Flower Bed Outside Hepner Hall - SDSU

Love Library Plaza - SDSU

Love Library - SDSU

Shortly after I packed everything up, jumped back on the trolley, and got back to the conference for the evening session and poster presentations.  By the time I got back to the hotel, I was beat.  But a KAP session isn’t complete until the gear is checked, so I examined my line for fraying (surprisingly none!) and checked my Dopero for dings.  It got a small tear in the sail, which I opted to fix once I got home.  Other than that, I got away unscathed.

More to the point, I got away lucky.  The lesson was still learned:  If the conditions aren’t right, it’s better to walk away than to risk hurting someone, damaging property, or damaging your own gear.

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