My family unit has decided to have a model rocket competition for Mother’s Day. Dad, BirdMan, the boy and I will all make rockets and Mom will judge which one goes the highest. Problem is, the only one of us who have ever made a rocket is BirdMan, and that was in shop class in middle school.
So, I’d like to know if any of you hobby around with model rockets and can give us a few pointers on what is necessary in the construction. I know you need an engine, but there are about a million kinds and I’m not sure what to get. I also know you need a tube to jam the engine in, a nose cone, and little fletchings around the bottom of the tube.
Anything else? Is there a good chance one of us will take an eye out if we try this? Is there a book we should purchase that has good information? Will glitter and racing stripes help with the aerodynamics?
I’ve only made the kinds from the kits, and last year when I made them for the first time there were many dopers who had lots of advice. It’s pretty easy when you follow the instructions.
Do kits at first. You can try custom ones after you learn their construction. You don’t have to worry then, that you’ll come up with a failure for a design. Don’t go for super long fancy ones, get a simple design. The tall fancy ones don’t stay together in a rough landing. The plastic paracuettes can get melted if your not careful packing in the wading and chute. Pick a model that isn’t going for a height record. They can drift a long way and it’s a frustration when it drifts half a mile away. Don’t trust the rocket if it failed to launch. Give it some time to be sure it isn’t doing a slow burn, and never get in front of the rocket after a failed launch. I did rockets for about 3 years. The last ones just went into the trash this year, because somebody roughed. I had some really neat ones, before they got busted. errggg!
Yep. Did rockets for years. late 70’s early 80’s I’m hoping you can still buy a beginners kit that will have your Launch pad, igniter setup, 12V battery (or are they 9? long time ago.) and a simple starter rocket kit, with engines. I always liked Estes’ stuff better than Centauri.
Or, what Projammer and the rest said. You’ll get better results starting that way than trying to build your own outta the paper towel core, and stuffing the bottom with match heads.
It seems there’s been some trouble, especially with some of the more enthusiastic hobbyists, those who go beyond cardboard and balsa for construction materials. Even then, it’s the manufacturers of rocket fuel who take the heat.
Currently, it seems, in the US, you’re fine as long as your pre loaded engine cartridge contains less than 62.5 grams of propellant. Can even have them shipped.
I have to agree with using an Estes kit. Once you have a bunch of different kit rockets laying around you can customize them by switching parts around between them, since most of them use the same diameter tubes.
To start, get ones with the smaller engines. The bigger engines go incredibly high - almost out of sight. And if you use a parachute, they can float for incredible distances.
If you get similar models, you will be able to mix and match any parts should rockets break or get lost.
Building the rockets the only tough thing to get the hang of is gluing the fins on such that they are relatively even and stay attached. But you can paint them and add decals as you like.
Don’t be at all surprised to lose them. We had a couple that we never recovered after their maiden voyage. And many many others that disappeared after being shot 2-3 times. That is why I recommend the cheap ones. Especially if you do not have a monstrously huge area to shoot them off in. It really may surprise you how far a little breeze blows them on the way down. We left more than one rocket dangling out of reach up a tree.
Big tip - bring extra batteries. Really stinks to be out in the middle of a field and have your launcher not work.
Be really careful with the safety instructions - especially if kids are involved. Say, “Everyone back! I’m putting the key in! Fire in the hole!” and such. Fun in a hokey way, while keeping everything safe.
I agree to start with kits to get a feel for it. And it’s more than a tube with fins. There needs to be an engine mount, which is at least an engine block, and more likely an engine block, engine tube, engine hook, and centering rings. Every bit as important is that the rocket must be stable, or what you’ll end up with is a pinwheel or landshark. Those can be dangerous. You also want to make sure that the rocket is light enough to build up some initial speed. If it’s not going at least 40mph by the time it reaches the end of the launch rod, it will not be stable.
Kits, by their nature, have these problems pre-solved.
If you insist on building your own, at least use the evaluation software here. And don’t use household items for parts. You can get boxes of parts assortments from Estes.
On the drifting thing – A poster from a hobby board was in the habit of putting his phone number on all of his rockets. One drifted out of his sight, and he thought it was lost forever. The next day, he got a call from the person who found it.
I don’t think anyone has addressed this, but the million different kinds of engines can get a little confusing, but basically a C engine is twice the power of a B engine and a 1/4A is 25% of an A. Wiki isn’t really as helpful as it could be, I seem to recall a much simpler explanation from Estes back in the day.
Each letter increase is twice as powerful as the preceding, so a C is twice a B and a 1/4 A is just that. If you really want to lose your rocket fast, go straight to D’s (or if you build a huge heavy ol’ thing).
Fun, cheap, easy, and the type I have my cub scouts build are the 1/4A size. Little things that aren’t a huge loss if you lose or damage them and usually don’t achieve the frightening height of the bigger guys. If you’re doing a contest, you might want to look at the little ones to keep things reasonable. Still, we lose a good 50% in just 4 launches (partially because the gluing techniques of 7 year olds leaves something to be desired)
The letter ratings indicate the newtons of thrust.
A = 1.25-2.5
B = 2.50-5
C = 5-10
D = 10-20
and so on. The actual amounts tend to be on the high side.
The number after the letter is how many newtons per second. So a C6 burns about 6/10 of its charge in the first second, and 4/10 in the next 0.8 seconds. A C5 will burn for a full 2 seconds, but won’t have quite the initial kick. An A8 obviously burns very quickly, but there’s a good initial lift.* The second number is time, in seconds, of the tracking charge, which is where the rocket get’s most of its altitude, but with no thrust. So a C5-7 engine have a flight of 9 seconds before ejection. And A8-3, about 3.2 seconds. A performance rocket can reach maybe 400 feet with an A8-3, and can top 1000 feet with a C6-5. I designed a small performance rocket that could top 600 feet on an A10-3T.
*My math is not entirely accurate, as the thrust profile is not linear.
The engines can be used in stages also. The sizes increase in diameter. The D’s are meant for large diameter rockets, and ones with a payload like a camera.
Yep, although my camera rocket uses B and C engines.
Engines can be clustered as well. That and staging are a lot trickier than single stage. Chance of failure goes up dramatically. I haven’t done that since I was a kid.
Thats the basic idea, but your units are wrong. The letter indicates impulse in Newton seconds (in the ranges you have given) and the number is the peak thrust in Newtons.
(1 Newton = Force required to accelerate 1 kg at 1m/s^2)
In a fit of boredom some years (20 or so) back I did the math and determined that the solid fuel boosters on the shuttle come out somewhere in the X neighborhood.
Bit late, but yesterday I saw someone who built his own rocket (with no chute) and fueled it himself. I don’t remember exactly what all he used, but I know that conc. H2SO4, gun cotton, and ammonium perchlorate were all involved. That thing took off like a shot, went pretty high before starting to yaw like crazy, and I’m not sure he ever found it. I think it went a good 1000 feet laterally easy.
