Monday, May 28, 2012

The All-Round Picavet

Last Saturday I took the chance to do some kite aerial photography, but time was short and I could not build a picavet to steady my camera before I left my house.

So I built one on site.

After 40 minutes of snipping, cutting and taping on the side of a footpath close to the water in between the Canada Goose droppings I ended up with this:
A picavet constructed from plumber's strap.

The pivacet I constructed out of All-Round,bottom rear view
The camera is a Canon PowerShot 410 I previously bought for 20$ Canadian in a pawn shop, so I was not two worried about losing it into the drink or dropping it from a height or both. I have a 4GB SD card in it so it can take thousands of 3.2 megapixel images before running out of space.  I did not have timed photos working (I plan to use CHDK) so I simply launched with the camera in video mode.

All-Round is usually used for suspending plumbing or reinforcing electrical wire in construction. It cuts easily with aviation snips and forms easily with the hands. It acts a lot like Meccano beams but comes in cheap long rolls, one variation is covered with nylon!  I estimate that I used 1.25m of strapping and that cost me all of a Canadian dollar.

I made a bender out of  the same material to make angled bends easier, but most of the forming was done by eye with my hands. The frame is deliberately squashed to one side to balance out the camera below the suspension point.

The cross was more all round with a spacer made from strapping to allow the frame to twist on a 2 inch long number 8 nylon bolt with two nuts on top jammed together to prevent them twisting off.  The camera was bolted on with a shortened 1/4"-20 nylon bolt and stabilized with some electrical tape (I ran out of duck tape early this month).

Next was a cradle of dark fishing line, some carabiners on the flight line and a trial launch for balancing. I had another camera with me (a better one that I was not trusting to my first picavet) and here is what the result looks like in the air:
Kite, Picavet, Camera, and Moon.
If you look closely just below the line between the kite and camera the crescent moon just stands out from the high cloud cover. Whoever identifies the kite can has bragging rights for as long as they want them. :) Also, the safety line attached to the camera strap is visible swinging downwind.  I wanted to be able to try again if my construction was not up to snuff!

The wind was strong -- Beaufort 4 according to the video evidence -- and the kite was on the edge of being overpowered despite flying high and stable.  The only disturbances to the camera I saw were how puffs would pull the line tighter and pitch the camera along the axis of the line as it straightened and bowed.

I now think that I should have added some split rings or other low friction loops to run the cradle line through to counter this , but I'm still very happy with the results of a first try.

Look for stills from the 640x480 video later, the video itself is too bouncy in pitch  to compress nicely.

Oh, I used my KAPstan to pull in the line, and it made what would have been a chore a simple workout.  I would not have sent the kite up ~100m more in that wind if I didn't have a good way to pull it down and hand winding onto a halo at high tension (I had no way to measure it but there was no problem lifting that 150g camera with 2 alkaline AA's and a steel picavet!

This effort is not as clean and tidy as one of the refined units from Brooxes shop, but I sure had fun with it!