Build It Yourself - Rocket Cradle

Recently, on The Rocketry Show Podcast Facebook discussion group, someone asked about a photo. CG, one of the hosts of the show, was presenting at NARCON 2016, and needed pictures of me and of Gheem, the other host, recording the podcast. CG posted our pictures on the discussion group.

Someone in the group asked, "In your pic showing you in your rocketry den, there is an apparatus that holds rockets horizontally and looks like it is made with PVC tubing. Where can I buy one of those?"

That object is a rocket cradle, and you don't buy them. You make them.

A rocket cradle holds a rocket on its side while you work on it, and keeps the rocket from resting on its fins on your work table. It can be very useful for when you're making fin fillets or applying decals, or even in the field when you're prepping larger rockets for flight. It's one of the easiest and cheapest pieces of equipment to make.

Rocket cradles are even used in real rocketry, during construction, storage and transportation of rockets. Here are two images of the Iris sounding rocket in cradles.

I'm going to show you how to make three versions of the rocket cradle.

Version 1 - For Small Model Rockets

 

This simple rocket cradle is described in The Handbook of Model Rocketry. It's made from balsa wood, but can also be made from basswood, cardboard, foam board or whatever you have on hand that's flat and can be easily glued together. Balsa is probably the easiest material to use, and if you build your own rockets, you should have some on hand anyway.

I used two pieces of 1/8 inch thick balsa stock, 3 inches wide. It's important that the ends be square, so if you're using scrap pieces with unevenly-cut ends, you'll want to square them up. One piece will serve as the base of the cradle, and the other will be the upright supports on the ends.

I drew a dividing line down the center of the shorter piece I'd use as the upright supports. The upright support board is 7 inches long, which will give me two 3 1/2 inch tall uprights.

I found the center of that dividing line, then marked spots 1 inch from either side of that center. This would give me a cradle with a 2 inch wide span.

I then marked the board so I'd have lines stretching from the outer marks on the support center line to the center of the board, at a 45 degree angle. You can use a compass to do this, but I found it easiest to use the drafting triangle from a Crayola drafting toy I had as a kid. I always figured I'd have a use for that thing if I saved it, and it has come in handy since I started building rockets.

You will end up with a square in the center of the board.

With a hobby knife, carefully cut the centering line, so you have two even pieces. As with cutting all balsa, use a new, sharp hobby knife blade, and don't try to cut in one pass - use several, light strokes to cut the wood.

You can lightly sand the cut ends so they're square if you need to. This balsa was very soft, so I got a jagged cut.

The square has now become two triangles, hard to see in the above photo, but on the right side of the upright support pieces.

Carefully cut the two triangles out with a hobby knife and a metal ruler.

You can stack the two triangles together and sand the edges even, just as you would do with a set of fins when building a rocket. These will become support struts for the uprights.

You'll be gluing the uprights onto the ends of the base board, and gluing the support struts to both pieces. I found the easiest way to do this was to glue the support struts onto the upright pieces first.

You want to glue them flush with the bottom of the upright boards, and as straight as you can. Drawing a centering line from the bottom of the cut-out triangles on the uprights helps to align them.

A piece of aluminum angle will help you get the support struts glued on straight and even with the bottom of the upright boards.

When gluing on the struts, a double glue joint will make building easier. Apply a thin layer of wood glue to one edge of the support strut, attach it to the upright board where you want it, and then remove the support strut. Allow the glue to dry for a few minutes.

Once the glue has dried a little, apply a little more wood glue to the same edge of the support strut. Again, you want a thin layer. Then, using your guide line and aluminum angle, attach it to the upright board.

The double glue joint will grab much more quickly, and you won't have to stand there holding the piece in place as it dries. It will take only a moment of your holding it in place for it to stand up on its own.

Repeat this for the second upright and support strut.

Let the glue dry for a little while, and once it's relatively set, apply fillets to the joints, just as you would do with fins on a rocket. This will strengthen the joint, so the uprights don't fall apart when you glue them to the base.

After the glue has dried for a little while - 30 minutes to an hour - you can glue the uprights to the base. The glue doesn't have to be completely dry on the struts, as long as you're careful not to break them off.

Apply a thin layer of wood glue to the bottom edges of the uprights and the struts, and make another double glue joint. Again, a piece of aluminum angle or other square object will help you get the uprights on straight and even with the edges of the base board.

The rocket cradle is complete. Allow it to dry thoroughly.

Note: I probably made the base of this cradle a little too long. I built it just for this blog post. It's a 9-inch long board. This cradle is good for smaller rockets, and probably shouldn't be longer than 6 or 7 inches. See below photo.

The Estes Viking is too short to be supported by the body tube.

Version 2 - For Medium to Large Rockets

This is the cradle seen in the background of the Rocketry Show picture. It's made of PVC, and is pretty versatile. It can hold medium and larger rockets, and you can add to it or change its configuration to fit your needs.

You see a lot of PVC cradles in online forums and at club launches. PVC is relatively cheap, useful for a number of rocketry accessories, and is pretty easy to work with. The tricky part is cutting it. You will need either some kind of saw or PVC pipe cutter.

I have cut PVC with a hack saw before, but it's hard to cut it straight. When I realized I'd probably end up building a number of things from PVC, I went ahead and got myself a pipe cutter which can handle PVC pipe up to about an inch and a half in diameter. It's a large, ratcheting clipper which looks a bit like an angry parrot. Whereas a hand saw leaves the edges of the PVC jagged, requiring you to sand the cut ends, the pipe cutter makes a clean, straight cut.

It cost me about $12 at a local hardware store.

The cradle in the above picture is actually two parts, which can be moved relative to one another, and which don't take up much space when not in use. I'll show you how I made it, and some variations you may consider.

You will need the following PVC parts, available at a hardware store:

• A length of 1/2 inch diameter PVC - at least 20 inches (it's usually sold in 5-10 foot lengths)
• Two 1/2 inch PVC cross fixtures (non-threaded)
• Four 1/2 inch PVC t-fixtures (non-threaded)

You will also need one foam pool noodle, which you can usually buy for less than a dollar from spring through summer, and sometimes into the fall.

It is important that the PVC fixtures be non-threaded. Some fixtures have threads inside them, to enable you to screw parts together. We want to be able to simply slide the parts together.

The first step is to measure out eight 2 1/2 inch lengths of PVC pipe and cut them.

Assembly is simple. Start by making the cross pieces. Put one 2 1/2 inch length of PVC pipe into each opening in the PVC cross fixtures.

Attach T fixtures to the ends of two adjacent pipes on each cross piece, with the open ends of the T fixtures perpendicular to the cross piece.

The cross pieces should now be able to stand on their own.

With a hobby knife, cut four 2-inch lengths from the pool noodle.

The lengths of pool noodle should fit right over the ends of the PVC pipe on the cross pieces.

Now you're basically done. You can move the two cradle pieces closer together or farther apart depending on the size of your rocket.

You might think you need longer lengths of PVC for the tops of the cross pieces. So did I, when I first started building this. But, unless you have a really fat rocket, it's going to nestle right in the corners of the cross pieces, and anything more on the upper arms is really just extra length.

Now, these two parts will stand perfectly well on their own. But if you want to take this cradle out to a windy field, and need some more stability, you can add feet. Simply cut two lengths of PVC pipe for each T fixture foot, put them into the openings, and add a PVC end cap fixture. Now you have a sturdy pair of cradles which are still small and portable.

If you want something even sturdier, or you simply want something that's one piece, you can join the two cross pieces with lengths of PVC pipe. In that case, you can use the T fixtures, as seen above, or you can substitute elbow fixtures, as seen here below.

You could even add a third cross piece for really long or heavy rockets which need extra support. Simply use a T fixture to attach the middle cross piece to the longer pipe, and T's or elbows for the end cross pieces.

You'll find this cradle to be a very useful tool.

Version 3 - Fast, Cheap, and Easy

Serious rocketeers never throw anything away before considering whether they might be able to use it for rocketry first.

This box once held a 12-pack of ramen noodles.

Get yourself a small cardboard box. Find the mid point of two opposite sides of the box, and mark it with a pencil.. As with the balsa cradle, measure out an inch or so on either side of that mark. Then, as with the balsa cradle, draw two 45 degree lines inward from those outer marks until they connect.

Cut out the triangles you've created with scissors.

Finished!

Now you have not only a quick and easy rocket cradle, but a box to keep parts in while you're working on the rocket.

You can cut notches on the two far sides for longer rockets, and the two nearer sides for smaller ones. You can even cut multiple sets of notches, and have a cradle that can hold two or more rockets at a time.

It's very satisfying to make a useful tool yourself, especially so inexpensively. And once you start using a rocket cradle, you'll wonder what you did without one.

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2016 Rocketry To-Do List

I walked into the Rocket Room today, and it hit me that I hadn't touched anything in there in maybe a week or more. The sun was streaming in through the windows, and it looks like my girlfriend tidied up in there a bit. It looks pretty in the sunlight.

This is much cleaner than it is when I'm working on something.

Time to put it to good use.

I've had a few things holding be back from being as productive a rocketeer as I was a year ago. My job sometimes has me starting at 4:30 in the morning, and sometimes has me quitting at 11:30 at night. This back and forth can be a bit draining. But things are about to get more regular for me, and I should have my Saturdays clear for launches.

So, here are some goals I have for the upcoming year.

1. Blog More Frequently

I was asked to be on The Rocketry Show because of what I had been doing on this blog - writing informative posts for rocket n00bs. But in the last few months, I really haven't written as much as I'd like to.

I have started about 8-10 good blog post topics, but haven't finished any of them. The kind of post I feel most proud of on this blog is a bit long (for a blog), but is clearly spelled out with lots of photos, so any rocket n00b who comes along can understand it. That takes time and energy, and if I'm too tired, I don't write. If there's not enough light, I have to wait on taking photos.

Yet, I'm still getting page views - usually between 25-50 per day. Some of these may be brand new people, but some may be previous readers checking back to see if I have anything new on the blog. I have no idea. Anyway, my first goal for the year is to create more content for rocket n00bs and rocket veterans to have something new to look at. A commitment to a little bit of writing each day might be called for, even if I don't finish a post in one sitting.

The new work schedule should help with that.

2. Figure Out the Painting Situation

Since my move to Boston, I haven't finished a single rocket. Not a single one - in six months. A major roadblock to completing a rocket for me is painting.

Back in Bloomington, I had plenty of outdoor space to paint rockets - and to do so privately.

Estes Big Bertha on a painting stand behind my old apartment

Here in Boston, I have to paint out front, and there's not much space between my apartment and the street. I don't want to get paint on the house. I need to figure out where to paint - especially larger rockets.

One option may be to join a makerspace - also called a hackerspace. These are a sort of co-op, where people get together to share tools and ideas.

I'm also considering building an indoor spray painting booth. But this must be done with care. A spray booth must keep paint inside, but must be properly ventilated. I've seen a few DIY spray booths online, but some of them are potentially dangerous. A box of sealed plastic sheeting is not enough if there's no ventilation. Spray paint fumes can cause brain damage in high concentrations!

A few weeks ago, I did manage to get a few small rockets primed, but that's it so far.

Estes Goblin

Estes Reflector

Imperius D - my own design. This was originally called "Donor's Rocket" on this blog. Mine will hold a D motor.

Astron Sprint XL Clone - this is a clone of an Estes kit. I'm building the kit, but wanted to
practice sanding the eliptical fins into airfoil shapes properly before trying it on the real thing.

3. Improve My Recovery Rate

The first several months I launched rockets, I had great success. Chad lost a ton of his rockets. I managed to keep all mine on the field and recover them with little to no damage.

Then, my first launch of 2015, I had my first loss to a tree.

3D Rocketry Nautilus II - my first tree loss.

The 3D Rocketry Nautilus II got badly tangled on a tiny tree branch very high on a tree on a steep incline. There was no retrieving it. It was still stuck there six months later, when I last launched on that field.

Most of my Bloomington launches went well. Some of them left the field, but I was able to retrieve them. Nonetheless, my record took a few hits.

Since moving to Massachusetts, I've had worse luck. Despite flying on a much bigger field, I have recovered far fewer rockets. Amesbury gets breezy. And I have been trying to fly higher. The higher you fly, the bigger the chance of losing a rocket. I've had several leave the field entirely and disappear in deep scrub, sticker bushes and swampy grassy areas. It has made me nervous to launch anything at all, and I only launch a few of the rockets I take out each time.

Since my first club launch, I'd say I've had recovery failures of over 50% of all my rockets. I look at the fleet in my rocket room, and it looks a lot smaller than I remember it. I need to fix this, and get back to launching with confidence.

This can largely be improved with careful parachute selection. It seems that Estes kits often come with parachutes that are a little larger than they need to be. The Cosmic Explorer has a large, 18 inch parachute which brings the rocket down very slowly. It's beautiful to watch, but it does mean the rocket has more time to drift in the breeze. Replacing the chute with something smaller would bring the rocket down a little faster, and it would still likely land intact.

Some rockets may need to recover on a streamer. I admit I have only done this with rockets which come with a streamer as a kit. Streamers make me nervous otherwise. But my first scratch build, the Janus I two-stage rocket, which flew very, very high, was pretty lightweight.

A nice, big streamer would probably have brought it down closer to the launch site and it would have survived intact despite a faster descent. Instead, I lost it - the first rocket I flew at my very first club launch. Streamer recovery is something I need to experiment with.

Another tactic to improve odds of recovery is to angle the rocket into the wind. For safety's sake, the NAR Model Rocket Safety Code states that you shall not launch at more than 30 degrees from the vertical. But that does give you some leeway. How much angle to tilt the launch rod will require some practice on my part.

Of course, selecting the right motor for the day's wind conditions is also important. But I've seen plenty of rockets at CMASS launches which went much higher than mine, yet which recovered just fine while mine did not.

4. Launch an Electronic Payload

I've had a Jolly Logic altimeter for nearly a year now, but I have never launched it! Consequently, I really have no idea how high any of my flights have been.

Until I can more reliably recover my rockets, however, I'm reluctant to use a $70 altimeter. In the mean time, I'll probably pick up the much less expensive FireFly altimeter and try that out.

The FireFly altimeter, from PerfectFlite

The FireFly, from PerfectFlite Direct, is not as fancy as the Jolly Logic, but it's tiny, and at about $22, it's a good choice.

I also need to successfully launch a camera. I've had a few tries. I've had a few failed cameras, and lost one on a payload section which drifted far from the launch site on the wind. The closest I've gotten to success were a couple of bad flights.

5. Finish Building My Estes Pro Series II Kits

 Earlier, I wrote about beginning to build two of the Estes Pro Series II kits - large mid power rockets with 29mm motor mounts. I began with the Nike Smoke, a scale model of a NASA sounding rocket, and the Ventris, a cool-looking rocket with a fat payload section.

Nike Smoke

Ventris

These are great kits, and Estes has been selling many of its Pro Series II kits dirt cheap (there has been much speculation that Estes is getting out of the mid power market. I have a feeling they'll hold on to their E2X kits and maybe the Mega Der Red Max and Nike Smoke, but Ventris, Leviathan, Partizon and Argent will probably all be gone soon.). These are meant to fly mostly on F and G motors, but many people use them to get into high power rocketry, as they will also hold a small H motor. They're big and impressive in person, especially if you've only built small low power model rockets.

I've been chipping away on both the Nike Smoke and Ventris for months. They're nearly ready for primer and paint. I've also quietly been working on the Estes Leviathan, a nice fat model (now discontinued by Estes), and a pretty good choice for a Level 1 high power certification flight, if you choose to use a 29mm rocket for that purpose.

I need to finish these guys. I want to have them ready by April, when CMASS, my NAR section, begins flying again.

6. Find a Nearby Launch Site

Because I live in Boston, I go out of town to launch rockets with CMASS. In the summer, they fly at a smaller field in Acton, MA, which is not terribly far from where I live. In the fall and spring, I have to drive all the way up to Amesbury, which usually takes me much longer than it should - at least an hour and a half, sometimes two hours.

But, unlike when I lived in Bloomington, IN, there's no place for me to go and casually launch a few small rockets. This is a sad state of affairs. If I want to go try out a new design, or if I want to show someone a quick launch (I have a coworker who is also a nanny as a second job, and I told her those kids would love rockets), or if I just need a little inspiration... When I haven't launched in a while, my building slows down, because I forget that feeling of why I'm doing this. Launching a few gets me hyped about building again... Anyway, if I just want to do a casual, non-club launch, by myself or with a few friends, I have nowhere to do it.

It's not that Boston doesn't have parks. It's that I don't want trouble.

Model rocketry is an overwhelmingly safe activity, despite the recent accident in California you may have read about. And model rocketry is legal in all but a few areas which have unfortunately banned it. I don't know for sure, but I'd bet there's nothing on the books banning model rocketry in Boston.

Despite this, I have heard of people having trouble. This guy in particular had the Boston police break up a scout launch, and it sounds like it was kind of a frightening experience!

Part of the problem is that model rocketry has a low public profile. Public familiarity with the hobby of model rocketry was probably much higher in the 1960s and 1970s, even the '80s.

From retroland.com

These days, however, despite the fact that the hobby seems to be growing, it's not as well-known a hobby outside the community of those who pursue it.

And despite the fact that rocketry is very safe, it looks really dangerous to an outsider. I've heard people say "that can't be legal!" People have mistaken model rockets for fireworks, for tiny missiles, etc. And if you're launching in a park and someone sees you and complains to the authorities, they have to respond. Not every officer can be expected to know every statute by heart, I suppose, and if something looks illegal or dangerous, they can shut you down. This is not an experience I want to have.

There is one giant park in a part of Boston I'm unfamiliar with. It's called Millennium Park, and apparently people do occasionally launch there. One local cub scout troop reportedly launches there each year. It's supposedly really big. I'll have to go check that out. Maybe I'll try to make some contacts at MIT - they do a model rocketry camp for kids in the summer. Perhaps they know of a good launch site.

7. High Power Rocketry Level 1 Certification

High power rocketry (HPR) is the big brother to model rocketry. Unlike low and mid power model rocketry, you must obtain a certification to fly, and launches must be conducted using a waiver from the Federal Aviation Administration. There are several criteria which define a rocket as "high power," but a really basic definition is a rocket which uses an H motor or higher.

A "Stretch Leviathan" by Jim Seibyl - Gheem of The Rocketry Show - lifts off

High power rocketry has three certification levels. Level 1 allows you to purchase and launch H and I motors. Level 2 will allow you to purchase and use J, K, and L motors, and a Level 3 certification will allow you to fly M motors and above, and to spend all of your money.

To obtain a high power certification, you must be a member of either the National Association of Rocketry or the Tripoli Rocketry Association. A Level 1 certification can be pretty simple if you do not try to make it complicated.

You have to build and fly a rocket on an H motor (which you may purchase if it is for the certification flight). You have to have one or more witnesses who are NAR or Tripoli certified. The flight must be successful and the rocket must be recovered. The recovered rocket must be judged to be able to fly again without major repair. In other words, minor damage, such as a chip in the paint job, will not disqualify your flight, but a broken fin will.

You can make a Level 1 certification flight more complicated by adding electronic parachute deployment, but you may keep it as simple as a very large model rocket launch.

The idea is that you must prove you are capable of building, launching and recovering a high power rocket safely, because these things are larger and heavier, so the risks are greater. Once you pass your certification flight, you may purchase and use H and I motors.

At one point, I thought I might have obtained my Level 1 by now. Then I realized I was in no hurry. Mid power rockets are quite impressive, and have a lot of the thrill of HPR with less of the cost and no certification requirements. And I haven't launched many MPR rockets yet, so I have that to look forward to still. HPR is costly, so I probably won't launch much. And yet...

And yet, there's a certain pride to be had from having a high power certification. Besides, I have the rockets and casing.

At a CMASS launch this fall, I went to our club vendor, Animal Motor Works - which sells kits and Cesaroni motors. Gloria of AMW had made turkey soup for the occasion. I'd arrived late, so I missed the famous CMASS hot dogs. I went to have some soup and introduce myself to Gloria.

Gloria's a charming lady. We chatted for a bit, and I said I might want to get some F or G motors. After a bit, she said "Why don't you have your Level 1 yet?"

I left with a belly full of soup and a Cesaroni Pro 29 Starter kit, which includes 29mm 3-grain reloadable motor casing, which can hold F, G or H motors. It would be perfect for a Level 1 cert flight. I promised Gloria I'd work on it and do my flight some time up at the large field in Berwick, Maine. What can I say? She talked me into it.

What rocket will I use for the cert flight? I haven't decided yet. Perhaps the Nike Smoke. Perhaps something else. I quite like the LOC Precision Iris, a scale model of another sounding rocket.

The Iris has a 38mm motor mount, which is more versatile than the 29mm, as there is a wide variety of 38mm diameter motors in various impulse classes. And with a motor adapter, you can use a 29mm motor in the 38mm mount.

These are my main goals for the year. I'll keep you all posted on how they're coming along - by sticking with Goal #1.

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