3/24 update Flite Report Post 10 Archer-- Geometric Build Contest

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BABAR

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Here are the upright pics.
About 3 feet high
Will fly on a D12-3 engine
Sides/Air Brakes are 1/4" balsa
Fins are 3/32" balsa
MiniRail Buttons from RailButtons.com https://rail-buttons.com/

IMG_5230.jpgIMG_5232.jpgIMG_5234.jpgIMG_5238.jpg
 
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BABAR

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BABAR

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IMG_5220.jpgIMG_5228.jpgIMG_5227.jpgIMG_5226.jpgIMG_5223.jpgIMG_5225.jpgIMG_5224.jpgIMG_5222.jpgIMG_5221.jpg

This is essentially a modified Helicopter model with blades set to Zero Angle of attack. So in theory at least, it shouldn't rotate (much)\
With the blades (for purposes of this model I will call them Sides/Brakes---- they are the SIDES of the rocket body on ascent, and they function as air BRAKES on the way down) open, the rocket should descend in a stable fashion. The Dihedral angle is set so the nose will be up on descent.

The above pics show how the blades are held in place during launch and ascent. There are holes in the fins at the tail end of the Sides/Brakes. A crochet hook is passed in through one fin and out through the opposite fin. It pulls a rubber band back, with a loop of the band held on each side. The bands are pulled down around the engine. The toothpick stubs are put there to keep the bands from slipping out between the Brakes. Once one rubber band is passed through and fixes two opposite Brakes, the rocket is rotated 90 degrees and another band is passed through the remaining Brakes.

The "front" ends of the rubber bands are directly in front of the engine. When the ejection charge fires, it melts the rubber bands right in front of the engine, the tension pulls the bands out, the engine is released (equivalent of engine eject) and the Brakes are pulled into position.
 

BABAR

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IMG_5244.jpgIMG_5243.jpgIMG_5242.jpgIMG_5241.jpg

Combined Brake Stops (heli -equivalent would be rotor stops) and Pull Band Displacement.
Hard to get pics to show this well.
Anyway, the things sticking out the side serve both purposes.
The Pull Band Displacement moves the fishing line monofilament outward. This gives a better angle of pull (I think the correct term is "moment") to pull the Brakes AWAY from centerline initially. Once they get away from centerline far enough, they pull into upward deployed position pretty easily.

The monofilament runs through plastic "buttons" (cut out of old hotel key cards) in holes in the Brakes. The pull bands for the Brakes are internal.
 

BABAR

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IMG_5246.jpgIMG_5245.jpg

Just started using these. The Helicopter versions of this tend to be a bit "floppy" on a rod, so I think these should really help.
 

BABAR

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will fly when weather permits
 

neil_w

Brain and brain, what is brain!?!
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I like it! Extra points for having no cylindrical components at all, not even a motor mount!
 

rstaff3

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Very creative. Hope there is a video of the flight!
 

BABAR

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[video=youtube;YUivPB1Hwlk]https://www.youtube.com/watch?v=YUivPB1Hwlk[/video]

[video=youtube;H3cc8P61Rx8]https://www.youtube.com/watch?v=H3cc8P61Rx8[/video]

Also had a broken rotor stop

IMG_5253.jpgIMG_5256.jpg

Proof of flight videos.
I am a bit disappointed.
One hinge failed (haven't had that happen on a NEW rocket before, does happen after several flights.)
Also, while arrow straight boosts (almost no rotation) this bird is a bit heavy, and on the D12-3 the deployment was late on both flights.

Fortunately, the solution is pretty easy. I am comfortable with the stability on this bird (a bit overstable probably, with little bit of wind still had some weathercocking.) So basically I cut off the front 6 inches, re-do the hinges, maybe an extra layer of duct tape on the outside and try to sew them in better.

I was happy with my country launch pad, I do need to move the rail buttons on the rocket a bit, as the rotor stop catches on the top of the rail, so wasn't able to use all the length of the rail. Easy fix.
 

BABAR

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Rebuilt it (shortened it, lighter weight, redid the rotor stops.)
Flew last Saturday, almost perfect flight

Few photos

Archer Short Open.jpg


IMG_5259.jpg

Video with phone camera. You CAN see the rocket descent although it is small in the distance, you can see that it does come down smooth and upright with minimal rotation.

at 36 seconds you will see a flash about 1/4 down from top of screen, that is the rocket on descent.

[video=youtube;2i4pBREa4WM]https://www.youtube.com/watch?v=2i4pBREa4WM[/video]

shows up better on the YouTube site on HD

https://www.youtube.com/watch?v=2i4pBREa4WM
 
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BABAR

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I actually like the lines of the shortened version, and I guess the front rotor stops (which are easier to make and more reliable) look like canards.
 
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