MY FIRST ROCKET

The.MiniTard

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I am starting this build with an Estes Dark Energy kit. I acquired this kit during a purchase and I simply don’t like the way it looks(plus, the balsa parts were broken when I opened the packaging.)No big deal here. I will use the Body Tube and Motor Mount to design my very own Rocket!
IMG_1008.jpeg

We begin this build with an Estes BT-55 Body Tube

Length- 18”(45.7cm).
I.D.- 1.283”(32.6mm)
O.D.- 1.33”(34mm)
*Weight- 20g(0.7oz) The weight of this tube is not given to me on the Estes website, so I used the weight of an identical BT from the Apogee website part no. 10131.
IMG_1009.jpeg
 

The.MiniTard

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Next on the list is a Nose Cone. The cone provided with the kit is just atrocious, I mean….just look at it, YUCK!
IMG_1010.jpeg

I have learned through a little research that, the BT-55 body tube doesn’t have as many options in the nose cone section that I’d like, but I will use the Estes 4 pack nose cone part no. 003163.


003163 - NC-55 Nose Cone (4 pk)


I chose these nose cones because of the variety. I can play with the different types and see how it will affect rocket performance. Initially I rejected the idea of using these cones, but I now believe these are the best cones for what I want to do.
 

The.MiniTard

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Now, fin design! I have learned, from a post HERE on this forum, that the fin should be 2 diameters of the airframe n ROOT LENGTH and SPAN, and have a CHORD LENGTH of the diameter of the rocket(airframe). This is a general rule of thumb by which I will begin building my Rockets.

Time to go "download" some info on fin design and decide what type of fin I want to use. Until next time, my friends!!
 

neil_w

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Now, fin design! I have learned, from a post HERE on this forum, that the fin should be 2 diameters of the airframe n ROOT LENGTH and SPAN, and have a CHORD LENGTH of the diameter of the rocket(airframe). This is a general rule of thumb by which I will begin building my Rockets.

Time to go "download" some info on fin design and decide what type of fin I want to use. Until next time, my friends!!
Download OpenRocket and play: https://openrocket.info/downloads.html?vers=22.02.beta.05. Don't rely on silly rules of thumb, experiment and see what looks good and provides needed stability.
 

smstachwick

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neil_w

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Yezzir!! I have that program and have began to use it.
Excellent. Then you will note that it will calculate the component weights for you so you don’t have to guess at that sort of thing.

Also a cheap digital mini scale is a mighty useful thing to have around, only about $10 on Amazon.
 

The.MiniTard

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Okay, went and got some balsa and basswood. Figured out what fins I want to use and I will be attempting to make them today!!

IMG_1031.jpeg
This is the style of fin I will be using. A swept clipped delta. Notice the lines under the leading edge. I wanted to make these fins a more complex shape but I will keep it simple for now.

IMG_1032.jpeg
 
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smstachwick

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Okay, went and got some balsa and basswood. Figured out what fins I want to use and I will be attempting to make them today!!

View attachment 547372
This is the style of fin I will be using. A swept clipped delta. Notice the lines under the leading edge. I wanted to make these fins a more complex shape but I will keep it simple for now.

View attachment 547373
Nice!

You’ll have an easier time with quadrilateral fins anyway. It’s easier to figure out which way the grain should run.
 

smstachwick

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If you were to try that shape, you wouldn't choose the same grain orientation?
Honestly I’m not sure what I’d do. The way I see it, you’d have three options:
  1. Run it the same way you did, just with the extra cut
  2. Run it parallel to the section with the heavy sweep
  3. Run it parallel to the section with more modest sweep.
I might look at kits with similar platforms and see what they do, or I might experiment a bit and try it more than one way. Three fins oriented differently, or matching sets installed on three different tickets, would be an interesting way to test them out.
 

ThirstyBarbarian

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Next on the list is a Nose Cone. The cone provided with the kit is just atrocious, I mean….just look at it, YUCK!
View attachment 547096

I have learned through a little research that, the BT-55 body tube doesn’t have as many options in the nose cone section that I’d like, but I will use the Estes 4 pack nose cone part no. 003163.


003163 - NC-55 Nose Cone (4 pk)


I chose these nose cones because of the variety. I can play with the different types and see how it will affect rocket performance. Initially I rejected the idea of using these cones, but I now believe these are the best cones for what I want to do.

That kind of nosecone is for science fiction type designs, which some people really enjoy. It’s not for everyone obviously, but I bet you can find someone who would be happy to give it a home if you don’t like it.
 

ThirstyBarbarian

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you want it? lol

Thanks! But no. A few years ago, I would have definitely said yes, because I love sci-fi rockets, but I don’t make many low power rockets anymore.

According to the rocket designer, who is a member on this forum, the concept behind that rocket and it’s unusual fin style was that it would be a high-drag design. Slower flights and lower altitudes. Maybe the fin style lent itself to a sci-fi design, and that led to the choice of nosecone. That part I don’t know.
 

The.MiniTard

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Any opinions on the build so far?
waiting on nosecones in the mail. December 1st they say. I will attempt to fly it then, hopefully its stable. Im not too sure it is though because of this stability caliber number.
 

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smstachwick

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Any opinions on the build so far?
waiting on nosecones in the mail. December 1st they say. I will attempt to fly it then, hopefully its stable. Im not too sure it is though because of this stability caliber number.
The rule of thumb is at least one caliber. Generally that’s enough stability margin for safe flight if you have 30mph off the launcher.
 

The.MiniTard

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so I've got my nosecones in!! Ive went with the cone shaped nose cone that's 6.5" long. Ive added two fins to the upper section of the body tube and that has brought the stability caliber down to 1.5. IMG_1070.jpeg
 

jqavins

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Download OpenRocket and play: https://openrocket.info/downloads.html?vers=22.02.beta.05. Don't rely on silly rules of thumb, experiment and see what looks good and provides needed stability.
99% agreed. "Silly" rules of thumb can be helpful for giving a reasonable place to start, especially if one is relatively inexperienced.

The dimensions you gave yield a fin area of the body tube diameter squared times three. If you're length in in the ballpark of ten times the diameter, and you've got three or four fins, that should be a decent place to start, though the exact shape almost doesn't matter as far as stability is concerned. Once you've done this a few times you'll be able to judge when it "looks about right" so you don't waste time on crazy dimensions before OpenRocket helps you zero in; until then, rules of thumb are handy.
1669761878046.png

(That last one is likely to break on landing; not recommended.)

When I was new, I would get into a trap of seeing the rocket is unstable, so adding more fin area, and seeing it get worse. WTH? My fins were so big that a bit more wasn't making any appreciable difference to the center of pressure (CP or CP) but was moving the center of gravity in the wrong direction. If I'd started with 3D2 or somewhere thereabouts, I would never have had that problem.

(Incidentally, I didn't know "3d2 until today. I'd read the 2D by 2D by D rule before, but never before worked out the result.)

If you were to try that shape, you wouldn't choose the same grain orientation?
Without the obtuse cutouts, the grain direction is correct. With it, as Neil stated, it would normally be made in two pieces. BUT, with the angles being so slight, and the grain direction splitting the difference between the two leading edge segments, I wouldn't worry too much. I would run some thin CA into those segments to strengthen them.

The rule of thumb is at least one caliber. Generally that’s enough stability margin for safe flight if you have 30mph off the launcher.
And that's with the engine loaded. That engine mass is very important, as the stability margin is a bunch greater when it's not there.
 
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techrat

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Thanks! But no. A few years ago, I would have definitely said yes, because I love sci-fi rockets, but I don’t make many low power rockets anymore.
Well, I do have a Dark Energy Kit on the build pile -- and I'm going to build it as-is, with one minor mod -- a 24mm Motor Mount. It may be high drag, but that won't stop me from trying an E30-4T in that, just need to use epoxy all over.
 

The.MiniTard

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This build is gonna be scrapped. I don't know enough yet to safely launch this rocket. I don't want it to go horizontal and become a missile hahaha, ive got to learn a bit more about stability. Sorry, guys.
 

smstachwick

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I don’t see an issue with sufficient nose weight. Have you considered doing a swing test? That’d be the easiest way of determining stability.

506A216D-5C4F-4501-A800-6A3DD54D3361.jpeg

With that BT-55 body tube you can upgrade the motor mount if you need more thrust.
 

lakeroadster

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I don’t see an issue with sufficient nose weight. Have you considered doing a swing test? That’d be the easiest way of determining stability.

View attachment 549433

With that BT-55 body tube you can upgrade the motor mount if you need more thrust.
1670296552423.png
The "Police" may have an issue with this... but then again "Sting" being tied up may be just what they had hoped for.
 

BABAR

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This build is gonna be scrapped. I don't know enough yet to safely launch this rocket. I don't want it to go horizontal and become a missile hahaha, ive got to learn a bit more about stability. Sorry, guys.
Time out! No need to throw the baby out with the bath-water. It's much easier to make an overstable rocket stable than an unstable rocket stable.

I'm not a big Open Rocket fan, partly because most of my rockets have square cross sections and don't lend themselves to sims, and partly because I am lazy.

I am pretty decent with Mind Sim, although only a Padawan to @Daddyisabar full Jedi powers.

Your bird without the canards has tail feathers that are much bigger than needed. It is OVER-stable, which isn't always a bad thing, just means don't launch it in winds over, say 5 mph. If you live in Amarillo or some other place that's usually windy, that's a problem, but maybe you have some good low wind days.

You added the canards, those will definitely reduce your overstability, maybe too much, here's where a swing test or Open Rocket can help you out. Remember in either case to account for the motor (or MOTORS) you plan to fly, and the chute and the wadding.

Options for optimizing. Ditch or trim back the canards (they only add drag, not a big deal, you aren't going for the Karman line on your first (or 100th) flight.

Trim back the tail feathers a bit (here is where a sim program helps you get there faster.) Take a look at rockets like the Black Brandt or WAC Corporal, they can give you a good idea of approximate fin proportional size, YOU get to pick the shape.

MOST people build a few kits before getting creative, but your first scratcher is still in the ballpark.

as long as you are safe and having fun, you are doing it right.

Straight trails (unless you go down the asymmetric fin road, in which case, I wish you straight trajectories!)
 
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