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BABAR

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Okay, let’s see if we can make a rocket that is a stable platform on the way up AND the way down.

Centering rings, inside hole for 24 mm mount, used a 20mm hole saw, will sand to fit
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BABAR

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Cut tube to 9” (relying on some base drag)

Will put in a 24mm mount, although plan at least on initial flights to go with adapter for 18mm.

4 fins already papered
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BABAR

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Inner hole sander
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BABAR

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Marks need to be right

I tried Estes marker and door jam, still not consistently straight.

I used the same marks and true multiple lines, you can see how thick the result was because there was a little bit of waggle with both the door jam and the Estes guide. For a standard sport rocket, not significant (and we will see if it helps here).

Figured the Payload Bay markers will be better by far.

The red tape arrow marks the Payload Bay mark

Btw, the sliding piece on the Estes marking guide was NOT in the way when I used it, just including it in photo for illustration

Time will tell
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Thanks @jadebox
 

Sooner Boomer

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Somewhat like a stretched Fat Boy? (w/24mm) Are you using through-the-wall construction?
 

BABAR

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Kind of my own version. I found four 1/16 fins that looked like they would work, so I papered them.

These is a reason for the big diameter, it will have three attachment points that hopefully will reduce rocket sway.


Cheaters.

These are fin root length (6 cm) x 1/16” x 1/16” that are easy to place on the lines, and will proved attachment points and hopefully optimal alignment.

With the exception of my interceptor E i have yet to do through the wall fins. I am putting in a 24 mm motor mount, although I will likely adapt down to 18 mm. As so many have said, it’s always easier to start with a big mount and go small than the contrary

Nose cone in place just to support the inside.
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BABAR

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Shroud line supports on forward centering rings (recycled key cards)
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K'Tesh

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I wonder if you were to build a rocket that is large enough (and powerful enough) to have an onboard gyroscope, would that give a stable camera platform on the up and down?
 

BABAR

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Complicated stringing up.

Three shock cords off the front, hopefully will help to hang steady from chute.

One shock cord out the tail, nose cone will be independent of the chute shrouds.
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GlenP

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I guess you just want to get the rocket to come down smoothly and not spin like crazy so you get a good stable camera during the descent. This will be interesting to see how that works. Looks promising so far!

I have not tried, but thought that maybe a small streamer on a long external shock cord from the tip of one fin would help keep the rocket from spinning around under a single chute. Kind of like a tail on a kite. The main chute does all the heavy lifting but the streamer just keeps the rocket oriented.
 

BABAR

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I guess you just want to get the rocket to come down smoothly and not spin like crazy so you get a good stable camera during the descent. This will be interesting to see how that works. Looks promising so far!

I have not tried, but thought that maybe a small streamer on a long external shock cord from the tip of one fin would help keep the rocket from spinning around under a single chute. Kind of like a tail on a kite. The main chute does all the heavy lifting but the streamer just keeps the rocket oriented.
Interesting idea.

I will see how this one flies as is, but could easily add that.
 

BABAR

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Two wraps of dental floss around the outside or the tube, one forward and one after of where the external shock cord parts come out. I don’t think zipper is likely anyway, as internally the lines extend downward, through the edges of the forward centering ring (reinforced with pieces of plastic key card) , then through the rear centering ring to loop around the motor mount.
 

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Bruce

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I wonder if you were to build a rocket that is large enough (and powerful enough) to have an onboard gyroscope, would that give a stable camera platform on the up and down?

This sounds like a great project!

I remember the demonstration where the professor would sit in a swivel chair while holding a spinning bicycle wheel in front. When the prof tilted the wheel to one side the gyroscopic force from the spinning bicycle wheel would rotate him one way in the swivel chair. When he tilted the wheel to the other side, the force would reverse his rotation on the swivel chair.

Couldn't a similar idea be applied to a rocket? If the onboard gyro sensed the rocket starting to spin one direction, the flight computer would command a servo to tilt the onboard spinning flywheel to stop the spinning.

Would this work? Or are there other, easier ways to absolutely stop a rocket from spinning?
 

BABAR

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This sounds like a great project!

I remember the demonstration where the professor would sit in a swivel chair while holding a spinning bicycle wheel in front. When the prof tilted the wheel to one side the gyroscopic force from the spinning bicycle wheel would rotate him one way in the swivel chair. When he tilted the wheel to the other side, the force would reverse his rotation on the swivel chair.

Couldn't a similar idea be applied to a rocket? If the onboard gyro sensed the rocket starting to spin one direction, the flight computer would command a servo to tilt the onboard spinning flywheel to stop the spinning.

Would this work? Or are there other, easier ways to absolutely stop a rocket from spinning?
Great thought.

I believe gyros would work, but probably not practical for LPR (or my budget!)
 

K'Tesh

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How much would a fidget spinner cost?
Then figure out a way to rig it to a motor that can spin it up, and disengage to allow it to spin freely... It's the last part that defeats my knowledge base.
 

jqavins

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The motor needs to go fast with non-trivial torque, and that needs a fairly beefy battery. So motor and battery are large in both volume and weight. So, as BABAR says, not an LP project. Well, that's my guess, anyway.

Anyway, BABAR, what do you plan to do about spining, i.e. around the virticle axis? The three anchor points shoud reduce rocking, I would think, but what about spinning?
 

BABAR

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The motor needs to go fast with non-trivial torque, and that needs a fairly beefy battery. So motor and battery are large in both volume and weight. So, as BABAR says, not an LP project. Well, that's my guess, anyway.

Anyway, BABAR, what do you plan to do about spining, i.e. around the virticle axis? The three anchor points shoud reduce rocking, I would think, but what about spinning?
I certainly may be wrong, but I think on most descending rockets with a single shock cord MOST of the spinning is because there is minimal INITIAL resistance to asymmetric rotational forces, so it starts spinning faster and faster one way, winds up the single cord up to a point that it can’t rotate any more, gets asymmetric the other way and unspools the coiled cord, kind of a vicious cycle.

With a 6 sided chute it is unlikely I will have a perfectly symmetrical dome (I will start with a small central spill hole to reduce “dumping”, so I expect there will be SOME degree of rotation, but not the nauseating degree frequently seen through most of the descent videos of low power rockets. You also see the frequently with dual deployment high power rockets. With high power rockets, it seems much more “damped” once the main deploys, although frequently still present, I think this is because the greater inertia of the high powered rocket under full chute resists the rapid rotation from coiling and uncoiling the SINGLE attachment, and swivels my help on heavier rockets, I don’t think the mass of low power rockets is sufficient for swivels to prevent rotation. So I anticipate (hypothesize) a slow steady probable rotation that shouldn’t degrade the descent video, in fact if I angle the camera out a bit from straight down it may enhance it.

I think I may also steal @GlenP ‘s idea of a streamer on one fin. Hope it doesn’t tangle the nose cone cord, which will be hanging like a pendulum from the base attachment to the rocket. Yes, both the streamer and nose cone attachment segments will run externally to the nose cone shoulder on boost.
 

jqavins

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That sounds very pausible. I look forward to the results.
 

Pete.D

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I believe gyros would work, but probably not practical for LPR (or my budget!)
The original Sidewinder air-to-air missile had little PASSIVE gyroscopes mounted on the tips of its rear fins; movement through the air would spin them to control roll. Apparently the control system on the front fins didn't have active roll stabilization. That technique might work on a model if the gyros spun up fast enough at launch; their mass would be a trade-off between spin-up time and effectiveness.

The latest Estes Astrocam has a plastic fin can; this is bad because it came a little warped, but it's good because you can bend the plastic fins to correct it by trial and error. I haven't got mine perfect yet, but it's getting better with each attempt.
 

Pete.D

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Wikipedia has good pictures and descriptions of the Sidewinder's gyros, which are called "Rollerons". The latest AIM9X Sidewinder doesn't have them, but the early ones did.
 

Cape Byron

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There are examples of rollerons used in HPR. Not sure how far down you could scale the concept.

 

BABAR

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Pics above.
The forward end of the body tube is wrapped with Mylar tape instead of painted. There are a number of reasons for this. The main one is that this is the area where I am going to use electrical tape to hold on the outside mini cams. By using a Mylar tape I can put tape on and pull tape off pretty much with impunity without worrying about stripping off or otherwise dulling that paint. The other thing is that while the thing is brightly colored, I like the mylar for Recovery purposes as if it lands in the grass any bit of shininess can always help make it easier to find. It also makes a contrasting color. I like this paint. I am not an excellent finisher and this is a relatively forgiving paint when you don't have a perfect underlying finish.

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well off of the three shock cord. We will have to see how it does in Flight. Getting it to deploy without tangling up will be a challenge.
 
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BABAR

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The rocket hangs well off the three shock cords. But the three outside attachments and nose cone cord attachment and the streamer cord have to run between nose cone shoulder body . I am sanding down the nose cone to get this a bit looser. Right now it's a bit tight
 

BABAR

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98 grams without motor. Of course, that doesn’t include camera or cameras.
built it with 24mm mount, but figured would adapt down to C5-3 for first flight.

the ring on one fin is to attach the streamer @GlenP suggested above,

so I will have 5 cords running from external to internal.

I wrapped some tape around the nose cone shoulder and crammed it in the forward body tube. That expands the tube (tape will come off before launch.) That plus sanding makes it loose enough that it should not jam with the cords.
 

BABAR

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Kinda looks like a 4 fin Fat Boy. Thought about a feminine version given the color scheme, but probably not politically correct.
 

jqavins

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I like the mylar for Recovery purposes as if it lands in the grass any bit of shininess can always help make it easier to find. It also makes a contrasting color.
And it makes spotting the rocket in the sky easier if there's any sun to glint off the tape.

Nice work, as usual.
 

rklapp

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You made it. That’s awesome. I’ve been looking for a camera that does 1080p and 60fps to avoid the slide show at 1/2 speed. Apparently the Astrocam does 720p/60 but have to buy the starter kit with it.

Will you upload individual videos or edit them together? If the camera records variable speed, then the audio won’t sync when editing but there’s a way around it (can’t remember the name of it now). Godspeed...
 

neil_w

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Looks good, I really look forward to seeing how well it works.

Not sure I understand the streamer, though... won't it just hang there right in the camera field of view? (descent rate under parachute should be slow enough that the streamer will not blow upwards).
 
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