3 Foot Sugar Rocket

[DontevenKNO3]

Hey guys. I was just curious on how one would go about making a 3 foot rocket. What should the body be made of and how should it be reinforced? What ratio should I use for a rocket of this size? What kind of wood/plastic should I use for the fins? I am really just looking for some basic advice when it comes to building rockets of this proportion because I know its very different from tiny ones. Thank you guys!

[ChrisNZ]

I honestly never had much luck with KNSU rockets, but I would suggest reading through this thread lots of information in there.

 

I think you'll need to work out a few main points though.

 

Have you made many KNSU rockets before. If so, how large?

What fuel mixes have you made, what one will you use?

Do you want a three foot rocket, or three foot rocket engine?

How long will the rocket be overall?

What design will you use? (bottle rocket or like a real rocket)

 

And I'm sure's there more to consider.

 

Personally I'd probley go for a long cardboard tube, fabricate card nose cone and fins.

I'd also look at using an engine slightly smaller diameter than the body of the rocket and using stand-offs, etc.

The engine would probley be made out out several grains, think like cored grains 6" each in length.

 

You could start making 6" grains of whatever diameter and I guess keep adding them to a longer and longer engine as you figure out how they'll run, or if they'll work.

 

Something else to look at.

[DontevenKNO3]

I was probably going to make it 4 feet tall overall, with nozzle. Im not quite sure how big i want the fuel compartment to be and honestly i may not even use a sugar mix. I was thinking a 1/2 inch think pvc pipe and anywhere from 5-7 inches in diameter. Im leaning towards a BP fuel setup 75/15/10 ? And the design will look very much like a real rocket. Im going to make some pretty heavy duty fins and i may even make some thrusters just for that extra bang.

[ChrisNZ]

I was thinking a 1/2 inch think pvc pipe and anywhere from 5-7 inches in diameter.

 

I would suggest you don't use PVC pipe, it's not really that safe is something goes wrong.

 

You should never use PVC as a mortar tube. If for whatever reason you have a shell go off in the tube and god forbid it be a salute, you have a giant grenade. HDPE will basically be destroyed but will more or less stay in one piece rather than sending hundreds of pieces of shrapnel all over the place.

I know it says for motor tube, but same goes for rockets that can suffer CATO.

 

As for BP, I've just started down this track myself. The 75:15:10 is kind of cookie cutter BP ratio. But I have been reading a lot about people using a 6:3:1 ratio for rockets too, not sure if this mix has issues when scaling up past bottle rockets or not though.

 

My best advice is to read the rocket threads on here, jump into chat if you see people in there, ask questions, start small and work your way up.

Edited November 26, 2010 by ChrisNZ

[dagabu]

Hey guys. I was just curious on how one would go about making a 3 foot rocket. What should the body be made of and how should it be reinforced? What ratio should I use for a rocket of this size? What kind of wood/plastic should I use for the fins? I am really just looking for some basic advice when it comes to building rockets of this proportion because I know its very different from tiny ones. Thank you guys!

 

The tube is pretty critical, you can buy one already made and then match the motor or you can do the whole thing from scratch. If making one from scratch, start with 5-10 turns of paper, glued well and dried on a greased mandrel. The actual rocket can be much shorter, like the picture and video.

 

VIDEO

[DontevenKNO3]

What kind of tube should i use. and i was thinking of using about 10inch fins. Would i need a guide rod if the rocket was on completly level ground and just balanced on the fins themselves?

[ChrisNZ]

What kind of tube should i use. and i was thinking of using about 10inch fins. Would i need a guide rod if the rocket was on completly level ground and just balanced on the fins themselves?

 

I would go do a quick YouTube search for model rocket launches and note down what seems to be popular. No point re-inventing the wheel aye.

 

I seriously can only suggest lots of research, lots of reading, and trying things out on a smaller scale.

[DontevenKNO3]

I have done alot of research but it seems homeade rockets of the size i have in mind are not that common and i have only seen few articles/videos corrosponding to them. Thats the only reason i'm asking these questions. but im going to start working on it tonight i will post with video/pics of the launch once its been built.

[nater]

I built a few rockets in that size range from my own designs in middle school. I used readily available Estes style tubes and nosecones, then made my own fins from cardboard and thin plywood. These flew with commercial engines, I wasn't aware you could make your own propellants when I was 13, but the principles in the rocket design are the same. I used a standard launch rod from any hobby shop, I wouldn't recommend launching it with just the fins to stabilize it.

[dagabu]

What kind of tube should i use. and i was thinking of using about 10inch fins. Would i need a guide rod if the rocket was on completly level ground and just balanced on the fins themselves?

 

Like I had said in a previous post, a rolled paper tube will work fine but if you are not comfortable making your own then you have to buy one. My suggestion would be to buy a kit HERE, they have lots of kits that should fit any budget.

 

If you are bent on making the rocket all by yourself and are willing to roll some tubes, you will need to focus on that aspect by itself for a while. Also, the fins on the attached picture are good enough for a 48" rocket if five are used, 36" rocket only needs four and anything 2 feet and under only needs three like shown. These fins are CNC cut to order, 1.5mm thick PVC.

 

The hardest thing about building a rocket is the motor, the parachute deployment is second and building is third. My kids first rockets were made from Christmas paper tubes over wrapped with kraft packaging tape and a formed newspaper nosecone. The ejection mechanism was 1/4 teaspoon 4FA on top of the motor pushing another paper tube with a paper piston on each end that pushed the parachute out, the only wading was under the piston on top of the motor.

 

Its an ugly beasty but it has flown 20 or more times with no mishaps though it only flies to 600 feet on a R-candy motor. This one is 21 years old and had to go dig it out of the rocket box for you all.

Edited November 26, 2010 by dagabu

[DontevenKNO3]

I am gonna make it myself and i decided im just gonna make some sorbitol engines. Ill prolly put 5 fins on it and possibly two thrusters. It will look closer to the first pic you posted. Thank you, you have been a great help

[dagabu]

Dont,

 

Its tricky to ignite two sugar rockets at the same time, use e-matches inside some quick match that has been bared 2" and tape then into the nozzle so that you get even ignition. Make sure you static test your motors first, some tubes cant handle the pressure.