[Canberrauav] flying tomorrow and update on recent events
Andrew Tridgell tridge at samba.org 
Sat Feb 4 20:56:04 EST 2012 

I'm a bit behind on updates for the mailing lists .... time to catch up!

We flew the Mugin with an APM1 last weekend, and used the flight to tune
the stabilisation parameters in FBWA mode, plus we did a few minutes of
loiter mode to test basic navigation. The flight went fine, apart from
one scary moment when the plane came too close to the flight line during
a loiter, and Jack put in manual but forgot to push up the throttle at
the same time. The Mugin stalled and Jack only just managed to pull it
out of a dive in time to save it. Phew! 

We didn't do a AUTO navigation test because the grey color scheme of the
plane makes the attitude at a long distance very hard to see and we were
concerned about successfully recovering the plane in manual mode if the
auto circuit went wrong (the circuit is a long way from the field
because of the wide turning circle of the Mugin).

To fix this problem Jack and I painted the top of the Mugin wings white
today (using automotive spray paint). That will make the attitude of the
plane much clearer. We plan on testing the new paint scheme tomorrow
morning at CMAC, and if it looks good we will try an AUTO circuit and
start tuning the navigation parameters. We also hope to improve the
loiter to be a bit more circular.

While I was doing some painting Jack was working on fixing the nose
wheel of the Mugin again. As some of you know, the nose wheel again
failed on landing last weekend. The sacrificial nylon bolts snapped on a
hander then usual landing (which is what was supposed to happen), and
those easy to replace, but the nosw wheel strut was also bent from
multiple landings and the fork which holds the wheel cracked and split
open. Jack decided to replace it with a much stronger design, which he
has been working on this afternoon and is now ready to flight test.

In other news, Jack and I did some bottle drop and parachute work
today. We used Jacks top balcony to test dropping bottles onto his
concrete driveway, a height of about 25 feet, which we calculate gave us
an impact speed of around 40 feet/s.

We first tested the aluminium bottle from the first floor, dropping it
from about 15 feet wrapped in bubble wrap. It landed with the lid down,
and broke open on the first drop! Not so good.

We then tested with a plastic 500ml 'Iced Tea' bottle, and used a stick
attached to the side of the bottle to drop it from various heights. We
found it was very resilient, and eventually dropped it from the full
height (25 feet) with no problem, with only bubble wrap to protect it.

After that we started looking at small cross shaped parachutes, aiming
to find a parachute that would keep the terminal velocitty to 40 f/s and
keep the bottle upright. A few internet formulas later gave us a design
made of two crossed strips of parachute material, each strip being 66cm
by 22cm. We made this up using material Jack bought this week, and we
then tested dropping the Iced Tea bottle with the parachute from Jacks
balcony and it performed well.

Our test parachute was held together with staples and a few knots, so I
then visited my sister in law and used her sewing machine to sew it up a
bit more securely. The result is we now have a cross shaped parachute
and associated bottle that is ready for testing at CMAC.

Tomorrow (Sunday) morning we plan on testing the new paint job, doing
some navigation tuning and enjoying the CMAC sausage sizzle. See you all
at CMAC!

Cheers, Tridge

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