The N00b T00b - A Quick, Easy, Scratch Built Tube Fin Rocket - Part 1: The Basic Build

I have a bunch of random model rocket parts lying around the Rocket Room. Some are things I intentionally stocked up on, and some are leftovers from kits I modified, or from other projects.

I have a bunch of short, BT-20 sized tubes (0.736 inch in diameter). They're most certainly supposed to be motor tubes, though they're a little short, so I'm not sure where they came from. Most Estes engine tubes are about the same length as an 18mm (A, B, or C) motor, while these are shorter. If you used them for a motor mount tube, you'd have to have the motor hang out the back by at least a half inch, whereas most Estes kits have the engine stick out about 1/4 to 3/8 inch.

I think they're leftover stuff from Rocket Camp which ended up in my pile of parts, and I think they might be from Pitsco, which a previous Rocket Camp teacher seems to have used.

I also had one 8.75 inch long BT-20 body tube which I know is a leftover from Rocket Camp. When you teach model rocketry to kids, there will always be parts left over. Not from the kits the kids build, but from the extra kits you have on hand.

Kids at camp will lose parts, glue parts in the wrong spot, shove parts up their noses or get them stuck firmly on their fingers and need them cut off by the nurse (yes, this all happened). Consequently, some of them won't have a rocket to complete if you don't have spare parts, and a kid at Rocket Camp with no rocket to build is likely to get bored and become disruptive. This is really a digression, but if you ever teach model rocket camp, make sure you have extra kits, and be prepared to end up with a bunch of random parts left over.

So, having given away launch lugs, engine blocks, fins, etc., I had one body tube left over from an Estes Viking.

I hadn't started building a rocket in a long time. The N00b family had recently moved, and for a while I was trying to just finish building and painting all the stuff I'd started in the previous two years. My build pile of kits is so big, I didn't know where to start.

Then I thought: maybe I should build a quick tube fin rocket, just to get back into it.

When it comes to model rockets, my tastes are pretty traditional. I like rockety-looking rockets - a nose cone, long body tube, and three or four fins. I'm not as interested in odd-rocs, saucers, boost gliders, or tube fin rockets. That's not a criticism - I enjoy seeing them fly at launches. It's just for my own fleet, I like mainly sport models and the occasional scale model.

But tube fin rockets can be fun. They have a lot of devotees. They can be simple to construct, and unlike rockets with flat fins, they apparently do not weathercock.

N00b Note: "Weathercocking" is when a rocket arcs into the wind. Almost all model rockets do this to some extent. It's a kind of side effect of fin stabilization. As a rocket's fins correct its trajectory in flight, lift on the fins rotates the rocket body around its Center of Gravity. As it oscillates, the rocket will tend to correct more in the direction the wind is coming from. Rockets with larger fins or rockets which lift off slowly tend to weathercock more severely than faster models, which may only weathercock slightly closer to apogee. See The Handbook of Model Rocketry by G. Harry Stine and Bill Stine for more on this phenomenon.

I had lots of parts, so building a tube fin model would be easy. Tube fin rockets can come in different designs, and I'm no expert on them, but it seems that the easiest to build quickly are rockets which use the same diameter tube for fins as it does for the main body tube. You can fit six tube fins perfectly around the center tube, so getting them glued on straight is easy.

As far as "designing" the tube fin rocket would go, there wouldn't be much design. I had parts, so I'd glue them together. I wasn't going to have to cut anything or shape anything. I'd just see how it turned out.

The rocket used a BT-20 body tube, the diameter used for 18mm A, B, and C motor mounts. So this would be what's called "minimum diameter." No centering rings, no engine hook, no motor mount - the body tube is the motor mount. Minimum diameter rockets tend to fly very high. Some examples beginners might know are the Estes Viking, Wizard, Hi-Flier, etc. The motor would be kept in the rocket though friction fit - a wrap of masking tape around the engine until it's tight enough that it won't fall out of the rocket, or be ejected out by the ejection charge.

Construction was simple. First, I glued in a spare engine block I found in my spare parts. I pushed it n place with an old motor casing so that the motor would hang out the back by about 1/4 inch.

Next, I glued on the fins. This is the part that makes a tube fin like this a snap. To get the fins on straight, you start with one fin. Run a thin bead of glue down one side of the tube fin and attach it to the main body tube. Then, lie both tubes on the work table, side by side.

A straightedge helped me make sure the ends of the tubes were even with one another, and the fact that both tubes were lying on a flat surface as the glue dried ensured that they were parallel - that the tube fin was straight.

As the first fin dried, I ran a bead of glue down a second tube fin and attached that to the body tube by laying it down next to the first tube fin.

A third tube fin was glued to the body tube laid on the table opposite the first fin.

I needed to figure out where to put the launch lug, since I'd never built one of these before. I tried to see if I could hide it in a gap on the body tube between two tube fins, but it turns out that BT-20 tube fins are a little too small to hold a 1/8 inch launch lug between them. So I glued a launch lug inside the fourth fin and glued that in place in the remaining gap on the body tube.

I made sure all the tube ends were even using my sanding block, and then I let the glue dry a little bit. The first four fins went on in about 10-15 minutes.

I flipped the rocket over when I felt the glue would hold without things moving, and quickly glued the remaining two fins in place in about 1 minute's time.

That was it. I popped on the nose cone, and had a look. With the exception of putting in a shock cord, the rocket was built.

Coming up: Stability? Payload? Paint? How about a name for this rocket??

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Built from Scratch - A Tale of Two Berthas - Part 3 (Nose Cone)

Click here for Part 1 of this series.
Click here for the most recent post in this series.

The Handbook of Model Rocketry by G. Harry Stine and Bill Stine briefly describes the process of turning a balsa wood nose cone from scratch, using a drill as a makeshift wood lathe. On page 47 of the Seventh Edition (the most recent), the authors write:

You can make your own special nose if you have an electric drill in your workshop. Drill a 1/4-inch hole in one end of a balsa block. Glue a 1/4-inch hardwood dowel into the block so that it protrudes about 1 inch. This gives you something to tighten into the chuck of the electric drill . . . When the glue dries so that the balsa block doesn't separate from the dowel as you start to spin it in the drill, insert the dowel into the chuck, turn on the drill motor, and carefully carve the balsa down to the desired nose shape using a file and very coarse sandpaper.

The Model Rocket News, Volume 7, Number 1, published by Estes Industries in December 1967, gives more explicit instructions on the process, including suggestions that you secure the drill to a work surface, draw a template to aid in shaping the nose cone the way you want it, cut away some of the excess balsa from the corners of the block, etc.

You can download a PDF that edition by clicking here.

You read these things, and if you're anything like me, you think That sounds pretty easy - but I bet it's not! Carving away just the right amount of balsa from a spinning piece with sandpaper sounds pretty simple, but I imagined it would be much harder than it sounded.

So, I went looking for a video tutorial. Surely, somebody, somewhere, had made a video on turning nose cones and uploaded it to YouTube. Probably several people, in fact.

But, try as I might, I was only able to find a short clip or two of a wooden nose cone in the middle of being turned, and on a wood lathe. The beginning of the process wasn't shown, neither was the end, and of course, the tools used were standard wood turning tools - chisels, and the like.

So, I'd have to try this just using the written instructions I had available. I thought of videotaping this process - to show how hard or easy it might be, depending on how it turned out - but I decided against it for a few reasons. First, I find when I try to videotape myself working on a rocket, even if it's something I'm pretty good at, I get a little distracted by the fact that I'm filming, and I tend to screw up. Also, since this would involve the use of a power tool, I didn't want that distraction to cause me to injure myself. Plus, it turned out that I'd have had a hard time finding a good place to put the camera and get a decent shot.

So here, in as much detail as I can give with photos and words, is how I turned this nose cone for the scratch-built Big Bertha.

A note on safety:

I am not an expert in using power tools. This post involves using a hand drill and a drill press for purposes they weren't intended for. While I never felt like I was at risk of hurting myself during this process, and I always felt like I had control over the tools I was using, I don't really know how safe or dangerous this is.

While this technique was first printed in a publication aimed mostly at children - remember, in the early days, this was largely a kids' hobby, marketed to and practiced by minors - it was also the 1960's! Things are certainly different than they once were - they used to sell chemistry sets with radioactive materials, for example, so it would seem certain standards have changed!

If you try this technique, you do so at your own risk. I cannot be responsible for you if you use a tool incorrectly or have an accident and hurt yourself. If you don't know how to use a drill or drill press safely, read the instructions, find a tutorial, or ask a friend who knows how. Consider joining a local makerspace if you need access to tools or help operating them safely. If you are a kid reading this, please don't do this without adult supervision!

Decide on the Shape and Create a Template

The first step is to decide what shape you want your nose cone to be, and to create a paper template you will use as a guide. Since I was building a Big Bertha, I didn't have to decide much, except for how long I wanted the nose cone to be. The Bertha cone is elliptical in shape, and I'd decided on 2.6 inches for the length (click here to see the previous post in this series, where I talk about questions of historical accuracy).

I don't have skills drawing or drafting, so I'd have to rely on rocket design software to do the work for me here. Luckily, when you create a design or simulation in OpenRocket, free model rocket design and simulation software, it will automatically generate a 2 dimensional template which you can print out in PDF form.

Shapes are rather limited when you use OpenRocket to create a nose cone template. If, for example, you were designing a rocket with an ogive nose cone, the template would end in a sharp point. This is partly because the mathematics used by rocket simulators to find the Center of Pressure (CP) in a model rocket make the simplifying assumption that nose cones come to a sharp point, even though in reality, most ogive nose cones are spherically blunted, meaning that the tip is rounded. That doesn't mean that you could't have a simulator which would enable you to create templates of different shapes, but which would make the same mathematical assumptions. OpenRocket could allow for spherically blunted shapes, I'm sure. And perhaps the developers will one day incorporate that feature into its design, but as of now that hasn't happened.

Still, with an elliptical cone, you don't encounter this problem. You still have a small range of shapes, but you can get a good looking Bertha cone just using OpenRocket's built-in template feature.

Next, cut out your template, as carefully as you can. You'll use this as a physical guide to check your work while turning the nose cone.

You can see that my cuts aren't perfect, as that's pretty tricky to do with either scissors or a hobby knife. But it's close enough for me to use.

Next, I traced the positive cutout from the template onto the balsa block.

This showed me what roughly what the finished 3-dimensional nose cone would look like. It didn't help that much, as the pencil marks would quickly be removed once I began turning. But it does help you visualize the cone and see how much excess you can cut off with a knife before you begin working.

Find the Center of the Balsa Block

You're going to drill down the center of the end of the balsa block and glue in a wooden dowel, to act as a spindle for the piece you're turning. It's best to find the center. I simply connected the corners with a pencil line drawn with a ruler, and that was good enough.

Even if you're slightly off, you'll be OK. Once you cut away the excess and start turning the nose cone, the dowel will end up becoming the exact center of the piece, because that's where the block will be rotating from. Still, try to get as close to the center as you can, or the block may wobble badly as you begin turning.

Choose dowel and drill bit to use. I picked a nice, thick dowel piece I found in my pile of odds and ends. It's probably best to pick the thickest dowel you can, as it will be sturdier when you turn the nose cone. At least a 1/4 inch thick is recommended.

I forget how thick this dowel was, but it was one of the thickest ones I had on hand which would fit into my drill chuck. I picked a drill bit the same diameter.

Drill into the center of the end of the balsa block. For this, I used my drill press. Drill to a good depth. On larger nose cones, you should drill deeper. I drilled till my press could go no further, and wished I could have drilled a little deeper into the balsa.

Try to drill straight down from the top. If you don't have a drill press, again, it will still be OK if you are slightly off. Once you begin turning, the dowel will become the exact center of the piece. But it's best not to start off with a wobbly, off-center block.

Glue In the Dowel Spindle

Glue the dowel into place, as deep as it will go. I would definitely use a carpenter's yellow wood glue for this. Pour some into the hole, press the dowel firmly into place, and let it dry a full 24 hours before proceeding to the next step.

Cut Away the Excess Balsa

If the block is too long, trim it down to just a bit beyond the tracing. Then, with a knife, trim away the corners a bit, so you have less to remove while turning the piece.

Put the block in the drill you're planning on using, tighten the chuck firmly, and give it a test spin.

Now, you're ready to shape the nose cone!

Turning and Shaping

I don't have any photos from the beginning of the process here, when I was starting to take material off the corners of the block. Since I started right in without making a video, I just forged ahead without stopping to take pictures every few minutes. But I can tell you that it was slow going at first.

I didn't have my hand drill secured to a base. I just held it in my left hand, and held the sanding block in my right. My sanding block was my only a shaping tool, and the coarsest sand paper I had on there was 150 grit - not terribly coarse. The beginning of the process was a lot of shaking as the sanding block bounced off of rough-hewn corners without taking much material off with each pass. I would have done better to have a much coarser sandpaper on the block - or better, to have started out with a rasp file or something similar, to shave away lots of material at the beginning, until I got a cylindrical block of wood.

And I soon realized that my hand drill was not up to the task. The chuck kept coming loose, making the piece wobble as it turned, and nearly fall out.

It seemed dangerous, and not very effective, so I switched to my drill press, which I could tighten down nice and hard. The balsa block stayed nice and steady.

Eventually, I got a nice cylinder, and then began to round the end.

After more narrowing and shaping, the block got closer to the diameter I wanted, and the tip got more rounded.

Once the block got close to the diameter of a BT-60, about 1.637 inches, I started forming the shoulder that would fit inside the rocket body tube. Since I was really into this project, I neglected to take a photo, but I started by measuring where I wanted the shoulder to start and touched a pencil to that spot as I turned the block. This left a nice black line as a reference point.

Then, I did as the old Estes instructions suggested, and used an emery board to form the shoulder. It's got a coarse side and straight edges, but its flexibility help ensure you don't sand too much off too quickly.

As the shoulder gets closer and closer to the final diameter, it's important to constantly measure and check your progress. If you make it too narrow, it might be too loose in the rocket. If it ends up a little bit loose, you can always wrap a bit of masking tape around it, but don't go too far!

Cut a ring of scrap body tube to check for the final shoulder diameter. Take the nose cone out of the chuck and try to put the body tube scrap on it, and when it just fits, slip it onto the shoulder of the nose cone and leave it there. This scrap will be your reference for the base diameter of the nose cone itself. You'll sand until the body tube and the base of the nose cone are the same.

After much work, the nose cone got closer and closer to the final shape. Here, it started looking pretty good. The base diameter was just where I wanted it, and I started working on shaping and shortening the rest of the cone.

I damaged the template and ended up cutting it in just over half. This might be easier to use anyway, rather than the full elliptical template.

Here, it's just a bit too long for the shape I wanted. It might, actually, be pretty close to the original Bertha nose cone, which, as we've mentioned before, was about 3.1 inches long. I could have stopped here, but I decided I wanted to finish this process.

Finally, I decided I was done. The cone was nicely shaped and the right length of 2.6 inches long.

I compared my work against the positive cutout from the template. Since the template is flat against the cutting mat in this photo, it looks smaller, but the nose cone and template are in fact, the same size. I couldn't believe it, but my first hand-turned nose cone came out nearly perfect.

Here's the balsa cone next to a re-claimed plastic Bertha kit nose cone, which will come up in this series in a later post.

The handmade cone is slightly longer - 2.6 inches vs. the 2.5 inch plastic cone. Still, they look... well, almost identical. I was really pleased how this turned out.

So, it turns out this is doable, even if you've never done it before. It makes a lot of dust. Some shapes might be harder to get just right than others. The key is to go slowly and don't try to work too fast.

Oh, and be careful.

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Built from Scratch - A Tale of Two Berthas - Part 2 (The Plan)

Click here for Part 1

Scanned, downloadable PDF files of The Model Rocket News can be found in a few places around the Internet. There are probably a few missing, and I don't know that any one site has the whole collection, but a lot of these have fortunately been preserved.

A note to the long-timers and the historical detail-oriented: I'm not going to do much fact-checking on this post. I'd like to get to the build. Feel free to add any historical facts, details, or corrections in the comments (but be nice!).

These can be downloaded for free, and you can read them online or print them out. It's interesting to go through and see where or when some of the ideas we now find common practice in model rocketry originated.

If you print these PDFs out, they should print in the original size. This is particularly helpful if you want to try and build one of the many rocket designs published by Estes in the 1960's and 1970's. Some plans use parts and tube sizes which are no longer produced by Estes (though you may find something similar through Semroc at eRockets.biz - you can always email Randy Boadway and ask. Sometimes he has made custom parts for people), but a lot of plans use still-common parts or tubes.

Instructions are pretty simple, and if you've put together a few kits, you should be able to follow the plans.

The Big Bertha was originally published in a 1963 edition of the MRN - Volume 3, Number 2 (click here for the PDF). A printout of the page would make a nice, framed wall hanging, I think. But if you're building a rocket, you need the printout for the fin templates, which you will cut out and trace onto some balsa sheet.

While I planned to make the rocket look as close as I could to the original Bertha plans, I'd make a few minor changes.

I would follow the fin templates exactly. These were of a slightly different shape than the current kits. Things change over time, due to plans being re-drawn, or tools used to cut parts wearing out over time and changing shape (this is particularly true of balsa nose cones), or what have you.

The motor mount from the original Big Bertha plans

Early instructions called for motor mounts being assembled with the centering rings attached to either end of a coupler. I guess they wanted more strength back then, or felt this would give better alignment. From what I've read, they'd sometimes get stuck halfway in when the glue would seize up. But I almost considered giving this a try. In the end, I decided against it. I would do a standard, modern motor mount - two centering rings and a motor tube, without the coupler.

You'll also notice there is no motor hook mentioned in the original plan. Presumably, you would keep a motor installed in the rocket with a wrap of tape, either friction fitting the motor into the tube, or wrapping tape around the base of the motor and motor tube.

That's fine to do, but I prefer the convenience of a hook, so I decided to include one.

These plans also predate the trifold paper shock cord mount common in today's Estes kits {sometimes referred to as a "teabag mount" because of its resemblance to a tea bag). Instead, two slits were made in the rocket body, and a shock cord was passed through from the back to the front and secured in place.

I really have no idea how they did this. That looks like some tricky weaving to me, threading that shock cord from back to front from the inside of the body tube. I would find that terribly frustrating. In any case, I didn't want to mar the rocket by cutting slits into it, so I'd use an internal shock cord mount on my Bertha.

One thing I was unsure of was the nose cone. I wasn't exactly going for 100% historical accuracy with this rocket, but if I had been, I'd have had some questions about the nose cone.

The current Big Bertha kit comes with a plastic, elliptical nose cone which is about 2.5 inches long (not counting the shoulder), and notably, it isn't pointy.

In the old days, of course, all nose cones were made of balsa, not plastic. The part, as listed, is called BNC-60L. BNC for "balsa nose cone," 60 for the fact that it fit a BT-60 body tube, and I suppose L... because it was long.

A couple of rocketry suppliers sell a BNC-60L today - eRockets.biz with their Semroc line, and Balsa Machining Service.

The plan drawing shows a nose cone which is nearly elliptical, except that it's got a slight point on the end. Is it an ogive? Is it a pointy ellipsis (if that's a thing)? I don't know, except that it's a different shape than on the Berthas I'm used to seeing. Does the drawing in the plan accurately represent the shape of the part Estes was selling at the time, or did it differ?

One thing that's sure is that nose cones changed shape over time, as parts used to machine them either changed through wear, or were replaced, or the parts themselves were redesigned either for aesthetic reasons or maybe even to save a little bit of balsa.

The current Estes Big Bertha kit uses a 2.5 inch elliptical (non-pointy) plastic nose cone. Estes stopped selling that cone as a retail part a couple years ago, when they started selling a new 3-pack of BT-60 cones.

A few vendors sell Bertha-style balsa cones. eRockets.biz sells a BNC60-L, the part listed in the plan, and it's 3.1 inches long. The image shows it as a non-pointy elliptical cone. They also sell a BNC60-MS. It's about 2.6 inches long. Balsa Machining Service and Aerospace Specialty Products also sell the BNC60-MS, though they're slightly different lengths. Balsa Machining describes it as the Bertha cone. This may represent another era of Bertha cones.

Now Vern Estes' original Big Bertha definitely looks like it has a longer nose cone than the current one. In pictures I've seen online, it really doesn't appear to have a pointed tip, though things sometimes look deceptive in photographs.

Detail of an image of Vern's Bertha
from NARAMlive.com

So, I'm going to guess, at this point, that the prototypical Big Bertha, the one you'd have built from the plan in the Model Rocket News, using parts purchased from Estes available in 1963, would have been about 3.1 inches long, maybe pointy/maybe not. And if I'd have intended to build a historically accurate 1963 Big Bertha, and had done all of this research beforehand, a 3.1 inch nose cone is what I'd have settled on.

But it was a lot of information to digest, and not being sure about any of it, I went with a guess. I decided on a 2.6 inch nose cone, which I would attempt to make myself. If that failed, I'd go online and buy one.

I figured I'd have a well-made, scratch built model rocket which most people would look at and simply say "That's a Big Bertha" without nitpicking nose cone length or historical this or that.

Which is what I did. In the next post: making the nose cone - from scratch!

Click here for the next scratch Bertha post!

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Built from Scratch - A Tale of Two Berthas - Part 1

I recently finished building two Big Bertha rockets - from scratch, rather than from kits. As a guide, I used the original plans, published by Estes in Model Rocket News in 1963, when Bertha was a free plan, before it was sold as a kit (the Big Bertha is now the longest continually produced model rocket kit in history).

I meant to build just one scratch Bertha, but ended up building two of them, almost by accident. I do this a lot.

I started this project for a few reasons. My original Big Bertha kit was one of my earliest builds, detailed a few years ago on this blog. I mention the Bertha a lot here, not because it's always been my favorite model rocket (it hasn't), but because it's so iconic, and simple, and with its large parts, it makes a good demo rocket.

But last season, I flew my now beat up Bertha for my final flight of the fall on a C6-3 motor. Our Launch Control Officer, Kenn, commented "There's no better combination of rocket and motor, folks!" and I thought, you know what, he's right. That is a great rocket!

The Bertha is such a pleasure to see fly. I always brought it to a launch as a kind of afterthought, thinking I should take something that doesn't fly too high, just in case. But each time I flew it, it was just... fun! It goes up relatively high, but you can still keep your eye on it, and it floats gently back down on its 18 inch parachute, and... Well, I guess I just have a soft spot for the Bertha. So, I wanted another one.

That was reason 1. Reason 2 is that, while it does fly really well on C motors, I've always wanted to put a D12 in it, but I built the Bertha kit before I knew you could upgrade these things. The Berthas I've seen fly on D12-5 black powder motors are really fun. With its large fins, the Bertha is plenty stable, and can handle extra weight at the back. So, I decided to build a Bertha with a 24mm diameter motor mount, for those Estes D12 motors.

Reason number 3 is that I always wanted to build one of the plans from the old Estes Model Rocket News. Back in the 1960s, many of these early newsletters featured rockets either designed by Vern Estes himself, or by readers of the Model Rocket News, who'd send in their own designs, which used Estes stock parts. In those days, it was pretty common for model rocketeers to have a fleet which was at least in part built from scratch, rather than from kits.

I figured the Bertha would be a good place to start. No odd, out-of-production tube sizes or nose cones to buy. Just a BT-60 tube, some 1/8 inch fin stock, and a stubby elliptical nose cone. Speaking of which...

Reason 4: I had always wanted to try turning my own nose cone from a block of balsa.

 The plan was to see how hard this could be, using a hand drill as a kind of lathe. From what I'd read in both the Model Rocket News and the Handbook of Model Rocketry, this was supposedly not only doable, but not all that difficult. I wasn't sure that was true, but I wanted to try my hand at it.

It's been a while since I've done this kind of Rocket N00b stuff where I try to figure out how something is supposed to be done and then publish it here. I thought this would be a good place to start, and it would save me having to buy a cone. I wanted to keep this Bertha cheap, if I could.

Spoiler alert - it turned out pretty nice!

So, despite my promise to myself to finish building everything I'd been working on for a year and a half before starting any new rocket builds, I began working on the Bertha. Then I ended up making a second one. More on that when we get to it.

The next few posts will detail my scratch build of the two Berthas.

Click here for Part 2 - The Plans

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Rocket Camp - Kit Selection

Click here for the previous post.

Click here for the first post of this series. 

One of the first and most important decisions you'll make when teaching a rocketry camp or unit, be it at a middle school, high school, scout troop or public library will be: What rockets will we build? There are a lot of choices available, and the answer you come up with will depend on the parameters of the class. You'll want to consider the age group of the kids you're teaching, the likely experience level they'll have, and the length of time you'll have with them.

The obvious choice for leading a group of kids in a rocketry class is an Educator's Bulk Pack. Most major model rocket manufacturers carry these. Estes and Quest Aerospace, the two biggest, have a pretty good selection of bulk packs, but there are others to consider. Apogee Components has bulk packs of different skill levels, as does FlisKits, and even Balsa Machining Services, which mainly specializes in rocket parts, has a  "School Rocket."

The School Rocket from Balsa Machining Services.

You'll need to decide on the skill level of kits, the type, and whether you want a variety pack with several different designs, or a bulk pack of the same kit. You should also consider the size of the field you will launch from, as well as the surface - whether it be grass, gravel, asphalt, etc.

What "Skill Level" means varies from company to company, and even rocket to rocket. There are some Skill Level 2 rockets which are very simple, and some Skill Level 1 rockets which have more parts or require cutting plastic. There's not much rhyme or reason to it, other than that once you get to Skill Level 3 and beyond, it's going to be too difficult and frustrating for first-time builders.

The Estes Goblin - a Skill Level 2 rocket which is simple to build.It does fly very high on
D motors, though, and does not come in a bulk pack. I just mention it as an example.

If you're working with younger kids or have a limited amount of time - say, a single afternoon - or if you are looking for something simple, for example, to demonstrate some principles of basic physics, then Ready-To-Fly (what Estes calls "RTF," and requires no assembly), or Easy-To-Assemble ("E2X," which requires some very simple assembly) kits will probably be best.

But if you have more time, older kids, kids with more experience, or if you are trying to teach the kids the craft of rocketry, so that they will feel comfortable continuing on their own when they leave your camp or class, you'll probably want to choose something that takes a little longer and a bit more attention to build.

When I mention students' experience, I'm not necessarily talking about experience with model rockets. You may be working with a scout troop who have built pinewood derby cars. Maybe you're doing something with 4-H, with a group who have experience with various crafts. Perhaps you'll be going into a shop class or even incorporating rocket building into an art class, with students who are used to using paints and glues. These are all valuable, transferable skills to rocket building. Especially working with glue - your first-time builders are going to need some guidance with glue, believe me!

As for type, you'll consider whether to use simple 3-fins-and-a-nose-cone rockets, or something with a payload section, or an "odd-roc" - a rocket which doesn't look like a typical rocket. A saucer is a common kind of odd-roc.

Estes Blenders - a type of saucer "odd-roc." These are interesting and don't fly too high.
The Blender is a more advanced build. Image from eRockets.biz.

 Before you choose, try to find the instructions. For most Estes kits, you can download the instructions and read them ahead of time. Same is true for other companies as well. That way, you can see if you'll need any special tools. You might find a so-called "Skill Level 2" rocket which you like, and which in fact is pretty simple to build. You might also find Skill Level 1 rockets you'd rather avoid.

Whether you get a variety pack or a bulk pack of all the same rocket will also depend on the factors I've mentioned above. Younger kids and inexperienced builders will need some guidance. If you simply hand them the instructions and let them have at it, they will very likely build too quickly. Some kids don't have the patience to let glue dry on certain parts, and you might end up with a class full of rockets with iffy construction. When in doubt, I'd recommend everyone have the same kit, so that you can build with them, step by step, and you can guide when it's time to set the parts down to let the glue dry while you do something else with them.

Finally, consider the size and type of field you will launch from. If you're flying on a small field, you'll either want a rocket that doesn't go too high (which is largely due to the motors you use, but will also depend on the rocket - a lightweight, thin rocket will fly much higher than a fatter or heavier rocket), or you may want to select a rocket that uses streamer recovery instead of a parachute. If you're likely to land on a hard surface, such as rocky ground or asphalt, you'll probably want to go with parachute recovery*.

Whatever kits you decide on, I highly recommend building one yourself a few days before class begins. A lot of experienced builders will modify their rockets slightly, changing out the shock cord for another material, for example. But I would suggest you build according to the instructions, as the kids will build. This will alert you if there's anything you need to be on the lookout for. Are there parts which don't fit together just right? Does it come with a two-piece nose cone which requires plastic cement? Do you have to make your own parachute, and if so, how tricky might it be for little fingers? These are the things you'll want to figure out before you get into the classroom. It's also nice to have a well-built demonstration model to show the kids on the first day. It can be hard to visualize what a pack of parts can really look like when it's assembled, and most bulk packs do not come with a face card with a nice photo of the rocket.

I went with Skill Level 1 kits, preferring balsa fins over plastic or card stock.

*In my case, I had both a small launch area and asphalt, as we launched from a parking lot. The lot would be coned off, but there were still cars parked in the vicinity, and there was the community college roof to be concerned about, not to mention a busy road not too far away. My biggest concern was that road, and though we could launch pretty far back from it, I decided I'd need to keep our altitudes to about 300-350 feet with parachute recovery.

Launch site in the upper left corner lot. We could be nearly 1000 feet from the busy road at bottom, but the width of the site was only about 450 feet. Sometimes there were cars parked next to the building, so we had to pay attention to the wind.

 * * *

I had suspected last year that I'd need all the kids to have the same kit. My suspicions were confirmed after the Estes Alphas I had requested did not arrive, and the first week kids each ended up with different rockets. It was great that they got to build whatever they wanted, but it meant I couldn't guide them through it. There was the issue of kids using too much glue, or trying to stuff a motor mount into the back of a rocket before the glue was dry, or the one kid who glued on his launch lug directly in line with one of his fins, so that the rocket wouldn't be able to go onto the launch rod. (We pulled that one off before the glue had totally dried and got it in the right place, but I might have missed it).

For the second week, we got a pack of the Estes Viking, because it was available at a local hobby shop.

This is a nice little rocket with card stock fins, with a wide variety of fin configurations. Kids could build with three, four, or five fins, and they could be attached in a variety of directions, so that each kid could make a slightly different rocket. (Balsa fins must be attached with the wood grain parallel to the fin leading edge, so there is only one right way to attach a balsa fin).

The Viking is what's called "minimum diameter." It's very narrow - only as wide in diameter as it needs to be to accommodate the rocket motor. Narrow rockets have less aerodynamic drag than larger-diameter rockets. That means they can fly very high - which kids love, but which cost me some money (I'll explain when we get to altitude tracking)! Fortunately, they weren't likely to drift too far. The Viking uses streamer recovery, which isn't ideal for asphalt, but with such a lightweight rocket, hopefully we'd get them all back with minimal damage to the fins and body tubes.

One drawback to the Viking is that the rocket has no motor hook on the back. The motor hook is really convenient for kids, because it snaps into place and keeps the motor from falling out the back of the rocket. The Viking requires a "friction fit," which means you must wrap masking tape around the motor until it's nice and tight - just tight enough that it won't fall out when the ejection charge fires, but not so tight you can't get the motor out and put a new one in when you're done. It's a very fine line, and one I still have a bit of trouble judging. Kids will sometimes have a motor fall out at apogee, or never be able to get the used motor out without damaging the rocket.

Also, because the rocket is minimum diameter, it has no motor mount - the body tube is the motor mount. I really wanted to show the kids as typical a model rocket as possible, with all the parts they're likely to encounter on most builds.

My solution was to put together a quick scratch build, a rocket I called Sounder II.

It had all the basic parts, but I didn't glue the motor mount into place until after the first day. When I was showing the parts of a rocket on day one, before launching, I pulled the motor mount out of Sounder II, showing the centering rings, thrust ring/engine block, motor hook, etc. I then glued it in, showing how this was done.

Sounder II also turned out to be very useful later in the week when talking about stability and rocket design. And it flew very well. It's always good to show kids a few scratch builds - scratch building was pretty standard in the early days of model rocketry, and it's a good confidence builder. A kid who understands stability and how a rocket goes together should eventually be able to learn to design and build his or her own.

Sounder II, with markings for the center of gravity (CG) with an A8-3 motor and a C6-5 motor.
Also marked is the center of pressure (CP). Though the difference is small, the
rocket is stable with the A, and marginal with the C. This will come back later.

On week 3, I went in a different direction - the Quest Astra.

It's a great rocket, but different than a standard Estes Skill Level 1 kit. It has through-the-wall balsa fins, so the kids won't get the fins in the wrong spot. Instead of a rubber shock cord with a paper trifold "tea bag" mount, as is used in Estes rockets, it uses Kevlar thread, tied around the motor mount and passing under the forward centering ring. Some of the kids had a little difficulty with this method. On my own Astra, I was so busy helping the kids with their rockets, I never put the launch lug on mine. I painted it without one. (This wasn't a mistake - I decided it was more important for me to show the kids how to paint than to have one more rocket I could launch with them. You can launch a rocket without a launch lug, but you need a tower or piston launcher. These are advanced launch pads more used for competition rocketry.)

* * *

This year, I went in a different direction. Hoping to avoid any purchasing mistakes, and wanting to make sure I selected a rocket which any of the more experienced kids were unlikely to have built before, I turned to Apogee Components. We built the Apogee Avion.

Apogee has a number of great bulk packs. They're not the cheapest you'll find, but they have a variety of great kits, both of their own and from Quest Aerospace. They carry simple rockets, like the Avion, which has balsa fins, and the Apprentice, with a single-piece plastic "fin can." They also have payload-carrying rockets and even a two-stage bulk pack for the truly ambitious.

Another nice thing about buying bulk packs from Apogee is that you can download a free RockSim file for each rocket they sell. This will allow you to show the design file on rocket simulation/design software, such as RockSim, which is sold by Apogee Components, or OpenRocket, which is free. With simulation software, you can get a rough estimate of how high the rocket will go with different motors, and you can also use it to demonstrate principles of model rocket stability, aerodynamics, and design.

I had thought the Avion looked like a cool little rocket for some time, so I ordered those. As I built the demo model, I discovered a few things. The nose cone came in two parts, so we'd need plastic cement. The shock cord is Kevlar, and is supposed to be anchored to the motor mount. The Kevlar shock cord is also pretty short.

The full length of the Avion shock cord,
when built according to the kit insructions

 A short Kevlar shock cord can be a problem. Because it's not elastic, Kevlar can actually damage the rocket. If the parachute ejects when the rocket is moving too fast - either due to a motor delay which is too long or too short - the force of the parachute opening can pull the shock cord back against the opening at the top of the body tube. Because it is so stiff, this can cause the shock cord to rip through the body tube, causing a long, jagged tear known as a zipper.

A zipper - a jagged tear down the body tube of a rocket, caused by the shock cord.
Image from an Apogee Components YouTube video.

Because I had already known about the Kevlar cord, and I knew some of my students really had trouble with the Quest Astra shock cord last year, I decided we would use some sewing elastic and make an Estes-style paper trifold "tea bag" mount.

An Estes paper trifold shock cord mount, sometimes called a "tea bag mount"

Some experience rocket builders don't like the trifold mount, because they sometimes "fail." In fact, it isn't usually the mount itself that fails - it's that the shock cord breaks. A properly-glued paper mount should be quite secure, because wood glue and white glue are said to form a bond that is stronger than the paper tube itself. In reality, I'm sure a well-glued shock cord mount may occasionally come out, but more often than not it's a failure of the shock cord itself.

But first rockets are usually lost or damaged long before that happens. They end up stuck in a tree, breaking because of a poorly-packed parachute, or simply flying so high on a C6-5 motor that they simply "vanish," that an elastic trifold mounted shock cord is probably sufficient. Some elastic cords last decades.

Unfortunately, when I stopped in to check everything the Friday before class began, I discovered that the sewing elastic I'd requested had been forgotten. We'd still use a paper shock cord mount, but just with the Kevlar. Mounting the shock cord near the top of the tube would at least give us a little more length on the shock cord, and if there were a zipper, it wouldn't go more than an inch or two down the tube, stopping at the paper mount.

These Apogee Avions are nice! They are really great fliers - straight up every time. I don't know what it is about them, but I really enjoyed seeing these things launch. Since they're larger than a rocket like the Viking, they don't go as high, and you can keep your eye on them the entire flight (unless you fly on a C motor - then they're capable of reaching 1300 feet - if you've got a large enough field, go for it! Even on A motors, these are exciting rockets to watch. After building a demo version and one each week with the kids, I now have four of them!

In an upcoming post, we'll talk about the building process.

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