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Old Mar 26, 2013, 10:44 AM
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Twinstar/Parkjet drop test

The trusty and very beat up Twinstar will serve as the dropship for this experiment:
Take a Hobbyking Parkjet up to altitude, release it and let it glide down. (powered flight will come later).

The tricky part was coming up with a reliable release mechanism that would hold the Parkjet in place while climbing but release it without any hang-ups.

Came up with a pretty simple system where the Parkjet has a thin wood "blade" attached to the its lower surface the fits into thin space between two wood strips attached to the top of the Twinstar center wing section. Then drilled a hole thru all three pieces of wood so a small dowel can slide thru and hold "blade" of the Parkjet in place. The dowel is epoxied to a push rod which is connected to a metal geared servo which is connected to the gear channel.

Flip the gear switch and the dowel is pulled out and the Parkjet is released.
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Old Mar 26, 2013, 10:46 AM
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Here is the video of the release test:

Twinstar Parkjet drop mechanism test (0 min 54 sec)
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Old Mar 26, 2013, 01:15 PM
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Whoa! this is gonna be a Great youtube video!
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Old Mar 26, 2013, 03:13 PM
KFC
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FWIW, I've been flying my piggyback planes for a few years now, and I ended up using these: http://www.hobbyking.com/hobbyking/s...ug_n_Drop.html

It's pretty much bulletproof, and it is easy to make your own release plates from a little bit of plywood if you don't want to use the included release plate.

8 foot flying aircraft carrier (2 min 41 sec)


Big-Ass Flying Aircraft Carrier: The Sequel (1 min 46 sec)


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Old Mar 26, 2013, 03:39 PM
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That was simply AMAZING!

How he kept it stable is beyond me!
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Old Mar 30, 2013, 08:45 PM
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Twinstar Drop of Parkjet

Well we completed "Operation Dumbo Drop" and it was a mixed success.
The Twinstar took off ok but struggled to stay stable with the Parkjet mounted on the top of the wing. It was pretty windy also.

Came over the soccer field at about 150' and hit the gear switch and the release mechanism worked. Released the Parkjet but it flew back, hit the rudder of the Twinstar and then fluttered around until it got it's nose down then spiraled in like a lawn dart. Didn't respond very well to controls. Lipo caught fire on impact. (video of that to follow).

Here is the clip of the release using a Keyschain #16 cam on the left wing of the Twinstar:

Twinstar airborne release of Parkjet (3 min 56 sec)
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Old Mar 31, 2013, 12:45 AM
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Ground view:

Operation dumbo drop ground view (2 min 53 sec)
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Old Mar 31, 2013, 01:52 AM
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Now that was One Great RC Youtube Vid! Looked like your cargo plane fired a air to ground missile Lol

what happened to the drop plane?
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Old Mar 31, 2013, 10:36 AM
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Quote:
Originally Posted by demondriver View Post
Now that was One Great RC Youtube Vid! Looked like your cargo plane fired a air to ground missile Lol

what happened to the drop plane?
Twinstar lands at end of ground view vid
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Old Mar 31, 2013, 10:56 AM
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Quote:
Originally Posted by ecworks View Post
Twinstar lands at end of ground view vid
My Bad, I meant the smaller plane that was dropped.
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Old Mar 31, 2013, 11:57 AM
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Quote:
Originally Posted by demondriver View Post
My Bad, I meant the smaller plane that was dropped.
Nose snapped off, left wing came off at joint, lipo burned. But should glue back together no problem. Can't figure out why it spiraled in like that. Had a FY-30a installed.
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Old Mar 31, 2013, 12:00 PM
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Quote:
Originally Posted by ecworks View Post
Nose snapped off, left wing came off at joint, lipo burned. But should glue back together no problem. Can't figure out why it spiraled in like that. Had a FY-30a installed.
Perhaps part of it hung up on the cargo plane which caused it to spin on release.
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Old Apr 01, 2013, 03:32 PM
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After viewing the release video, I can see that the Parkjet hit the Twinstar twice after being released, amplifying the loss of control. In my opinion, two things would be required to greatly improve the odds of success: (1) better coordination between the two pilots, and (2) different flight management for the Parkjet. The Parkjet needs up elevator and matched (thrust matching the Twinstar) thrust at release.

Without matched thrust, it would be similar to holding the plane out of the window of your car while driving and letting go. With a complete lack of control, it will just spiral around until it crashes.

Without lift, the Parkjet's biggest obstacle is that the Twinstar is in the way. This test was done with down-elevator programed into the Parkjet while it was attached to the Twinstar to improve Twinstar control. The exact opposite elevator needs to be activated at the moment of release to improve clean separation.

Time to repair and try it again? We'll see if I can get a small EDF on the Parkjet.

PS: This was a 3 cell Lipo, two cells burned in sequence (with a pause between burns), the third is intact or unburned.
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