Building the Big Bertha - Part 8 (For N00bs)

[Click here for Part 1]

Now that your Skill Level 1 rocket is painted (and completely dry), it's time to finish building it - then you get to fly the thing!

If you've been following my posts here, you may get the impression that these things take forever to build. Actually, you can complete a Skill Level 1 rocket in a day or two - sometimes in as little as just a few hours (most of that is waiting for glue to dry). But I wanted to give you the details on how I build a rocket. I approach even easy rockets with care, so mine sometimes do take weeks, but that's only because I'm fussy and want a really nice end product. If you skip all the extras and just follow the instructions in the kit, you'll be done rather quickly, something you should probably do for your first rocket, so you don't get frustrated and quit before you see how awesome this hobby is.

OK, let's finish this baby up by adding the recovery system - this is how we get the rocket back safe and sound to fly again. All we have to do is attach the shock cord and parachute, and we're done!

First, we're going to attach the shock cord - that's often a long, flat, rubber band-looking thing (or sometimes a thick, yellow Kevlar thread). We'll assume you're probably doing an Estes kit, like the Big Bertha, because that's what most people do. So, the rubber bandy thing.

Your instruction sheet will have an elongated trapezoidal shape divided into three numbered sections. That is the shock cord mount - you'll have to cut that out with scissors. Fold the two sides inward along the fold lines, so they'll crease easily when you glue the shock cord in.

Put a dot of wood glue in the middle area, and place one end of the shock cord in it, with the other end running out through the fat end. Fold the skinny end of the shock cord mount over the center part and press it so the glue spreads throughout it. Hold that in place a moment until the glue starts to set.

Next, place some glue onto the fat end of the shock cord mount where the cord itself is trailing out, and fold the middle/skinny ends over that. Press until excess glue squishes out the sides, and hold that until the glue starts to set.

Now you'll have a long shock cord secured into a tiny trapezoid of paper. Allow this to dry a little bit (I've moved too quickly here and the whole thing came apart because the glue hadn't properly set), but you don't need it to dry completely to move on.

You now have what's sometimes called a "tea bag mount," because if you hold the shock cord with the mount hanging down, it kind of looks like a tea bag.

This finished mount is smaller - because it's from the Estes Star Trooper - a tiny rocket. Again, I got
engrossed in finishing the Big Bertha and neglected to photograph the finished shock cord mount.
But it looks the same, aside from the size.

The final step here is to place some glue into the body tube. Get a good dab of glue on the pad of your finger and spread it in one squarish spot on the inside of the body tube, about 1 1/2 to 2 inches from the top - no less. You need to make sure the shock cord mount is far enough into the rocket body to keep it from touching the nose cone when you insert it, or the cord might get in the way, and you won't get the nose cone on, because the fat shock cord won't leave enough space!

Wipe the excess glue off your fingers and place the shock cord mount down onto the glue, with the side the shock cord comes out facing the opening at the top of the rocket. Press this down and rub it around a little to make sure the glue spreads evenly and thinly under the paper shock cord mount. Hold it there a few moments until the glue begins to set, then let go.

Set the rocket on its side and allow the glue to dry for at least probably 20-30 minutes. Then, for good measure, use your finger to apply a thin layer of wood glue over the top of the shock cord mount to make sure you've got it good and sealed to the inside of the rocket.

Boom. Shock cord is now done. With the other end, you'll tie it to the loop of plastic in the base of the nose cone. Tie it well - a buntline hitch works, or just a simple double knot - and then you might put a dab of glue onto the knot to keep it in place.

Tying a buntline hitch

Let the shock cord mount and the nose cone glue (if you used it) dry completely, with the rocket lying on its side, and the nose cone lying separately - don't put the nose cone into the rocket at this point, or you might glue it on permanently, and you don't want that!

Once the glue is dry, it's time to attach the parachute. Probably the majority of basic kits use a parachute for recovery. Smaller rockets might use a simple streamer - a ribbon of plastic or paper which slows the rocket's descent enough that it won't be damaged. The streamer is pretty simple; you just tape one end of it to the shock cord. Other rockets might use some other form of recovery - tumble recovery, say, where the rocket comes apart and is so light it just falls to the ground in two pieces, and doesn't tend to get damaged.

But let's assume you have a parachute for now, like the Big Bertha has.

Skill Level 1 kits come with the parachute already assembled - you get a hexagonal chute with three shroud lines, each line attached to two corners of the chute.

The easy way to attach it to the nose cone is to hold the three lines together, form a little loop at the end, and thread this through the same loop of plastic in the nose cone to which you attached the shock cord. Pull the loop through, open it up with the shroud lines halfway through. Then you're going to pull the chute tight and pass it through the big loop and pull that tight - the chute will be attached to the nose cone.

This parachute is tied directly to the nose cone - you can see how the shroud lines get tangled after a few flights.

However, you might want to be able to remove the parachute between flights, and if you tie the chute right to the nose, you won't really be able to do that. It will quickly become tangled, and you won't get it untied. Parachute lines become tangled in ways that almost seem impossible to me. The lines are attached to the chute at one end and the nose cone at another, and yet, sometimes, I look at a parachute after a flight and ask How did those lines get tangled?? They crossed over each other! What is this sorcery??


Also, it's good for the chute to be stored separately from a rocket, hanging upside down, like from a pin in a cork board. The chute will be less likely to become permanently folded, so you're less likely to have it fail to open. A good way to attach a parachute is with a snap swivel. You get these where you find fishing equipment.

I love this aspect of rocketry - you find useful tools and materials where you wouldn't expect them to be, and you hack or adapt them to your purposes.

Just attach the chute to the closed loop of the snap swivel like you would to the nose cone, and when you want to attach everything to the nose cone, you just open the snap swivel and attach that to the nose cone.

All you do now is fold up your parachute, stuff it and the shock cord into the body of the rocket, and put the nose cone on top.

There are a number of ways to fold the parachute - some better than others. The instructions for the Estes kits aren't great - when I fold a chute like that for flying, they fail to open about half the time.

Estes has you fold the top of the chute over and roll the sides in - not
ideal for launching, as they don't open half the time (in my experience).

We'll discuss parachute folding - with pictures - when we talk about launching. For now, you can roll the chute up like it says in the kit instructions.

Put the nose cone on, and look at your handiwork:

The completed Estes Big Bertha rocket - tall and beautiful!

YOU HAVE FINISHED YOUR ROCKET!

I hope any rocket n00bs out there have gotten some useful information from this Skill Level 1 tutorial series. This is just the beginning. There are a lot of cool tools and techniques, more advanced kits, higher skill levels, more powerful rocketry options and cool add-ons for rockets (payloads, multistage boosters, etc.). We'll get to all these on this blog, I hope. For now, build yourself a kit, fly it, and see if you like it. If you do, build a few more kits. When you get confident with your skills as a basic rocket builder, you're ready for something more challenging.

I've been doing this for only a little over three months now, and I've learned so much. There's a lot of fun stuff to do in rocketry, and things that seem way too complicated when you first start out are actually achievable. If you develop a passion for this, like I have, you can advance your skills and do things that will surprise you.

Take it slow. It's not a race. Have fun.

But here's a preview of something you might not yet think you can do - I certainly didn't when I started. This is a rocket I designed and built myself - and it's a two-stage rocket on top of that! I'll make a post soon about designing and building your own - something very satisfying, and not as complicated as you might think - it just takes a little time, the right tools, and some thought.

For now, though, here's a video of the first launch of my first "scratch-built" rocket, Janus I - named for the two-faced Roman god of beginnings and change. I hope you enjoy.

Building the Big Bertha - Part 6 (For N00bs)

[Click here for Part 1]

We're getting closer to finishing our Skill Level 1 rocket!

Once the fins are on, attach the launch lug. That's the short tube that looks like a piece of drinking straw.

First, I like to scuff it up a bit, so the glue holds better. I do this on one side with rougher grit sandpaper. Then I do a double glue joint, putting a bit of glue onto the roughened surface of the launch lug and attaching it to the rocket for just a moment, as perfectly straight as I can along the launch lug line we've already marked. I remove it, and allow the glue to dry a little, then apply more glue and attach it to the rocket.

Scuff one side of the launch lug

    

Apply a thin layer of glue the entire length of the launch lug

Place it on the rocket where you have marked the launch
lug line, getting some of the glue on the rocket

Allow the glue to dry for several minutes. These reverse-
action tweezers aren't necessary, but they are a nice little tool!

Add a bit more glue and attach the launch
lug to the rocket - make sure it's straight!

You must make sure it is straight - the launch lug will slide down over a metal rod called the launch rod (when we actually take the rocket out and launch it). The rod keeps the rocket flying straight for the three feet or so it takes to gain enough speed for the fins to keep it stable in flight. If the launch lug is askew at all, the rocket can grab hold of the rod, and either not take off, or fly in a weird direction, or even try to take the rod with it! Site down the length of the body tube to make sure the launch lug is straight and true. You can even (carefully) slide a launch rod into the lug and verify that it follows the line you marked on the tube - then you'll know it's straight. Just (carefully) remove the rod so it doesn't weigh down on the glue and push the lug out of alignment as it dries.

Site down the length of the rocket to verify the launch lug alignment. Be sure to adjust it
while the glue is still pliable if it's crooked. Work fast - a double glue joint sets quickly!

Let the glue on the launch lug dry before moving on.

The fins are on, so let's reinforce the joints. We're going to make fillets. A fillet is a rounded joint in a corner, often found when two pieces are welded together at a right angle. In model rocketry, this makes the joint where the fin connects to the rocket stronger, and it also reduces interference drag, making the rocket more aerodynamic.

For our rocket, we'll use more wood glue.

The simplest way to do this is to apply a bead of glue at the base of the fin at the leading edge, then take your finger and run it along the base of the fin, dragging the glue with it. You should get smooth, even line of glue connecting the fin to the body all the way down the root of the fin.

Instead of your finger, you could also use a craft stick (popsicle stick) or coffee stir stick, or even a narrow dowel rod.

I always get extra glue on the fins if I do it the simple way, which either I can't sand off, or don't have the patience to. So I mask off my fins with a little low-tack masking tape. I've been told by some real rocket craftsmen that this isn't necessary with glue fillets, but I find it makes mine a lot neater, so I always do it.

I start by masking two fillets - two joints between the fins and the body - at a time. You'll do two fillets in one go on each side of the rocket, and by side, here I mean the space between the fins. So, if you have a four-fin rocket, like the Big Bertha, you'll have four sides. Three fins, three sides. Etc. Each side will have two fillets each, one for each fin.

Here, let me just show you...

This is what I'm talking about. I've got a tiny bit of tape on the body tube at the leading edge of the fin, then one piece of tape running the length of each fin, and tape on the tube itself, with a little gap between the tape lines where the glue fillet will go. If you're building a rocket where the fins are not flush with the base of the body tube, I'd put a piece of tape there as well.

You'll want to lay the rocket on its side with the joints you're working on facing upwards, so you can work on the fillets, and so they'll dry evenly. Here's one of the many little things I love about rocketry - coming up with a creative solution to problems. There are big problems and little problems in building rockets, and they all require creative solutions.

Here's a few ways you can do this.

You could lay the rocket on its side, with the tube supported by a thick book.

Could be just fine. But you might not want to put any lateral stress on those fins before you reinforce the glue joint. And if you're building a three-finned rocket, this won't work.

The joints aren't facing upwards!

 You could lay a dowel rod on a table, place something heavy on it, and slide the rocket body over it.

You could place the rocket down on a table (or in this picture, a thick book) with the fins hanging over it, and lay a heavy blanket over the body of the rocket. This will hold the rocket down, but won't squash the body.

In my case, the problem is solved by the Guillotine Fin Jig. The long metal arms are for holding the fins when you attach them to the rocket. But once you're done, you can slide the rocket through the jig the other way to hold it gently but firmly in the horizontal position for working on it.

Whatever solution you come up with for this little problem, just make sure the rocket is secure, that it won't fall or get crushed, and that it can remain undisturbed in a horizontal position while you work and while the glue dries.

OK, enough of that digression - back to fillets!


Drop a healthy bit of glue in the gap between the tape lines. If you're building a small rocket, a bead may be enough. The Big Bertha is pretty big, and I find if I don't put enough glue, I can't get the fillet to run the whole length of the fins, so I put a bigger blob. Don't put too much, though. You are going to pull most of it off, and the more glue you use, the more of a chance you'll get a mess.

First, notice that I don't put the bead right at the fore of the fin.  With a craft stick or coffee stir stick (depends on the size of the rocket, and therefore, the radius of the fillet I'm making - bigger rocket, fatter stick), I push a little of the glue forward to the leading edge, then run the glue back down the length of the fin, smoothing it as I go. Do this quickly, so it spreads evenly, and if there are any bubbles when you're done, smooth them over with the stick.

 

Once the fillet is smooth and covers the entire seam between the fin and body tube, remove the tape. Don't wait long to do this - fresh glue will smooth out and make a nice smooth seam, but once the glue has started to set, it will leave a sharp ridge.

Remove all the tape, from the fins and also the little bits from the body tube.

When you remove the tape, you should have smooth, even fillets.

Let these set and dry a bit before moving on. I can't tell you how long - 20-30 minutes, maybe? I dunno. Go have a snack or something. When the glue looks dryish on the surface and the color has changed from off white to more yellowish, you're fine to move on. Turn the rocket to the next side and do those fillets. Repeat until you're all done.

Oh, and don't forget to put a fillet on each side of the launch lug! The launch lug takes some stress from the launch rod, so you want it to be secure!

We're nearly done building our first Skill Level 1 rocket! Next up, we'll prime and paint this sucker, then we're almost ready to fly!

Click here for Part 7

Building the Big Bertha - Part 5 (For N00bs)

[Click here for Part 1]

In Part 4, the first thing we did was to reinforce the ends of the body tube with a bit of thin CA - cyanoacrylate, or super glue. Turns out, this is a really good idea.

A couple days ago, I took a few rockets out to try out my new homemade launch controller.

I took my newly-completed Big Bertha with me. Since it was a little windy, and I didn't want to lose my beautiful, new rocket to a big gust of wind, I put in the weakest motor I had - an A8-3 (We'll talk about motors later, but I'll just say, the A is the least powerful of the standard sized motors). This was a mistake, because it turns out this motor is far too weak for a rocket this heavy (always read the instructions!).

The controller works great. But the rocket lifted off the launch rod, went about 50 feet maximum into the air, then the motor ceased its burn and the rocket took a nose dive straight at the Earth. The ejection charge blew the nose cone off about 6 feet from the ground. The parachute didn't even open, and the rocket body embedded itself into the ground.

The parachute is still folded...

This could have been the end of the Big Bertha. But I pulled it out of the ground. Smoke still oozed out of the top of the tube. Apart from a bit of mud, grass and clover leaves, there was no damage!

So that Rocket Pro Tip was well worth it!

OK, back to our build. Now it's time to add the fins to the rocket body.

The first thing we need to do is determine where the fins will go, and mark the tube, so that we get them on straight. Kits come with a fin marking guide for this purpose.

You'll cut this out and wrap it around the body tube, somewhere near the base. Make sure the lines on the ends line up perfectly - that's how you know you have the fin marking guide on straight.

You can see here that my fin marking guide has a bit
of a gap in it. Some Estes kits are a bit sloppy on a few
details. But the fin lines did line up perfectly.

The lines marked FL are fin lines - put a pencil (NEVER a marker or pen) mark on the body tube where they indicate. The LL line is for the launch lug - mark this as well. In the above photo, I had it off-center a bit while manipulating the camera. Often, the launch lug and the engine hook are lined up.

Next, what you'll need to do is draw a perfectly straight line up the body tube to show exactly where to place the fins. Well, how do you do that?

The traditional way is to place the body tube in a door jamb and use that as a straight rule to mark a line up the tube. People have been doing that since the birth of model rocketry in the 1960's, and it works. Many kits will explicitly include that in the instructions. If that's all you've got, it's fine. But it has drawbacks.

Some door jambs are not as straight as they should be - especially in an older house that has settled, or been repainted many times. And they may have chips in them. And you'll get pencil lines on your door jambs.

Using a door jamb to mark a fin line -
notice the nick in the jamb?

 There's a better option.

You can make yourself a really cool, cheap tool, with aluminum angle. This is a piece of aluminum, sold at hardware stores, and it's used for... I dunno. Construction or something. Doors or windows. I have no idea. I only know it's used for rockets.

It comes in 3-foot lengths, and it costs less than two bucks. Get yourself a piece of 1/2 inch aluminum angle, the kind with equal-length sides, and cut off an 8- to 12-inch piece with a hack saw. Here's mine:

I even put 1-inch marks on the side with a Sharpie so I could use it as a crude measuring tool. I wasn't sure that would come in handy, but it has. Not as precise as a ruler, but it's nice to have some times.

See how the angle sits exactly along the tube?

Line the angle (or the door jamb, or the Estes Tube Marking Guide) up with the fin marks you made, and draw a line up the body tube, for several inches. Then do the launch lug line. I like to mark the launch lug line with an LL so I don't accidentally glue a fin to the wrong place.

The yellow thing is an Estes Tube Marking Guide part.

See? Perfect lines!

Now it's time to glue on the fins. This gave me a real panic the first time I did it. I knew I would have to do this freehand, and I was pretty sure I would screw it up.

There are options for assuring that you get perfectly straight fins. But if this is your first rocket, try it freehand. It's not as hard as you think - you'll just have to hold the fins in place until the glue sets.

For low power rockets, most people use either wood glue - sometimes called "yellow glue," because it's yellowish - or "white glue" like Elmer's Glue All, so called because it's white. Some people use epoxy, but that's more for higher powered rockets, so for your first Skill Level 1 kit, just get some yellow or white glue. Do not use "school glue" or anything washable - it just won't hold as well.

Wood glue, white glue. I started with the Elmer's wood glue,
but I've really taken a liking to this Titebond stuff.

You can make the glue set better and in less time by creating a double glue joint. This works really well with wood glue, which is about all I use, because it creates a stronger bond - stronger than the material it's gluing, so the rocket itself will break before the glue does.

First thing to do is to put a small bit of glue on the root edge of the fin. Just dab a bit on the root edge, then spread it up the edge with a finger, so there's a thin layer of glue all along the edge. Then locate the place on the rocket where the base of the fin will sit - it's often, but not always, lined up with the base of the body tube (your kit's instructions will tell you where to put the fins - you may need to mark a spot on the body tube where they'll go). Put the fin exactly where you'll glue it down, pressing the glue to the body tube. Then remove the fin.

Yep. Remove it. We're going to let the glue on the fin edge and the body tube dry a bit. Then we'll re-glue it, and the "double glue joint" will set a lot faster, and be a lot stronger. Set the fin somewhere where the glued edge won't touch anything, and let the glue dry for a few minutes.

When I built my first rocket, the idea of getting the fins on straight was the part that made me hesitate. But I did pretty well with it. I did have to keep my hands on the rocket, and keep checking that I wasn't moving the fins, but I'm happy with the rocket.

But there are tools you can use. If you read Harry Stine's Handbook of Model Rocketry, you will find instructions for making a very simple fin jig, called a Kuhn fin jig. This is just a piece of wooden angle - used for doors or something - with a slot cut right in the center.

Works great - if you have the power tools to make it, and know how to get the slot cut exactly perpendicular to the angle, and get it the right thickness for your fins - none of which do I have or know how to do.

The Estes Tube Marking Guide has a Kuhn-style fin jig at the end, which is helpful - sometimes. I've used mine on a few rockets, but I discovered quickly that if the fins are too thick, they'll barely fit, and if you're building a smaller rocket with more than three fins, it won't work at all...

Building the Estes Mini Honest John. With the Estes Tube Marking Guide
fin jig, I can get opposite fins on, but not the
two side fins. Those, I had to do by hand.

Still, it has helped me get my fins on straight on some of my favorite rockets.

I recently invested in the coolest tool in my toolbox - the Guillotine Fin Jig, created by a guy named Ted Macklin, and sold by Apogee Components. Now, if you're just getting into rockets, and not sure how involved you're going to be, you might want to hold off on a lot of special tools. The Guillotine Fin Jig is not cheap - it's about $90. But it is so ingenious. It holds your rocket in place and holds your fins perfectly straight. So, if you're building your first rocket or so, do it by hand. But if you've decided that you really want to make more, better rockets, getting a fin jig like the Guillotine is a really nice investment.

It's also great for carrying stuff from one room to the other, if you tighten down all the nuts, because the body of it is basically a wooden box.

Back to gluing on fins! Once your glue has set for a few minutes, apply another thin layer of glue to the fin root edge, and carefully line the fin up with the fin line you marked on the body tube, and hold it - or jig it - in place. Let it set for a few minutes at least before you do anything. I leave mine in the fin jig for at least 20 minutes or so and get a snack or work on some other rocketry project.

 

There may be small gaps due to imperfections in the tube, or imperfect
sanding - this is fine. Press the fin to the tube tightly for a moment and
let the double glue joint do its work. We'll fill in any minor gaps later.

Perfectly aligned fin. This is why I love good tools. You need skill to make a nice
rocket, but a good tool can help you make a better rocket, with less of a struggle.

Repeat the process for all your fins.
























Now the fins are on, and your rocket is starting to actually look like a friggin' rocket!

Next time, we'll apply glue fillets to the fins to reinforce them (and make them more aerodynamic), attach the launch lug, and maybe even prime this sucker and start painting! Stay tuned...

[Click here for Part 6]