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Rocketry for the common R/Cer

FAI-F1D

Free Flight Indoorist
#1
So I've noticed lots of us here like rockets, and there's not really a subforum for rocketry here, so I'm just slapping this in one of the more active parts of the forum and we'll see where it goes.

What's the point? Well just post your rockets here and see where it goes.

I'll start. My son absolutely loves rockets (I have no idea why a kid in a family whose previous 3 generations have been utterly obsessed with rockets would like rockets. None whatsoever). So I designed a rocket for him and included some of the design principles for safe own-design rockets in the process. Have a look at the process and my moment of utter stupid:

And my parenting recovery:

Obviously I'm a long time rocketry advocate here. And for the uninitiated, here's an example:
 

JTarmstr

Well-known member
#2
So I've noticed lots of us here like rockets, and there's not really a subforum for rocketry here, so I'm just slapping this in one of the more active parts of the forum and we'll see where it goes.

What's the point? Well just post your rockets here and see where it goes.

I'll start. My son absolutely loves rockets (I have no idea why a kid in a family whose previous 3 generations have been utterly obsessed with rockets would like rockets. None whatsoever). So I designed a rocket for him and included some of the design principles for safe own-design rockets in the process. Have a look at the process and my moment of utter stupid:

And my parenting recovery:

Obviously I'm a long time rocketry advocate here. And for the uninitiated, here's an example:
Hey! A fellow OpenRocket user, I have been using that to design my rockets for over a year and a half now. I dont have any special photos on this computer but i will see when i can dig some of my photos out. My Favorite rocket is definitely my payload 1'Ceres' D class rocket, that thing is just impressive. Anyway, thanks for starting this and i will add some of my more memorable flights at some point. also in the second videos launch it freaked the cat out :)
 

FAI-F1D

Free Flight Indoorist
#3
Hey! A fellow OpenRocket user, I have been using that to design my rockets for over a year and a half now. I dont have any special photos on this computer but i will see when i can dig some of my photos out. My Favorite rocket is definitely my payload 1'Ceres' D class rocket, that thing is just impressive. Anyway, thanks for starting this and i will add some of my more memorable flights at some point. also in the second videos launch it freaked the cat out :)
Ok, let's get this going... Do you have any procedures for dealing with the drag coefficients in Openrocket? I'm somewhat alarmed that it underpredicted coasting time by at least a full second (predicted apogee at 5 seconds, rocket was still going up at ejection, 6 seconds after burnout, both flights). Also, the descent rate appears to be off by a considerable amount too (25-30 second flight time predicted, 50 seconds actual). So yeah, my Openrocketfu needs some serious help.
 

d8veh

Well-known member
#4
You need a bit more consideration for the poor pussy cat. Not only did you scare it to death, but you nearly burned him too.
 

JTarmstr

Well-known member
#5
Ok, let's get this going... Do you have any procedures for dealing with the drag coefficients in Openrocket? I'm somewhat alarmed that it underpredicted coasting time by at least a full second (predicted apogee at 5 seconds, rocket was still going up at ejection, 6 seconds after burnout, both flights). Also, the descent rate appears to be off by a considerable amount too (25-30 second flight time predicted, 50 seconds actual). So yeah, my Openrocketfu needs some serious help.
So what i am mainly concerned about is maintaining stability, i try to ensure that all my parts weigh similar to what the simulator thinks (you have to override it if it gets the weight wrong), the primary reason being i want a accurate CP and CG so nothing crazy happens. As for drag, do you set surface resistance, such as paint? i always put mine on Matte and it affects the coasting time dramatically. I would also recommend checking predicted weight and making sure nothing went crazy. As for descent time I find parachutes are hard to predict (they can get twisted, spill air, etc). I generally just pick the right parachute or streamer based on a chart i have, then i just match the weight up with descent speed to pick the right parachute. Then distance (predicted altitude) divided by descent speed = time.
 
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FAI-F1D

Free Flight Indoorist
#6
So what i am mainly concerned about is maintaining stability, i try to ensure that all my parts weigh similar to what the simulator thinks (you have to override it if it gets the weight wrong), the primary reason being i want a accurate CP and CG so nothing crazy happens. As for drag, do you set surface resistance, such as paint? i always put mine on Matte and it affects the coasting time dramatically. I would also recommend checking predicted weight and making sure nothing went crazy. As for descent time I find parachutes are hard to predict (they can get twisted, spill air, etc). I generally just pick the right parachute or streamer based on a chart i have, then i just match the weight up with descent speed to pick the right parachute. Then distance (predicted altitude) divided by descent speed = time.

Unfortunately I'm contemplating an L1 attempt at some point so I need a fairly accurate assessment of coasting time (trying to avoid extra gadgets, dual deploy, etc). I'll probably make an end run around it by flying an R/C glider as my L1, but that does nothing for my desire to occasionally use said L1 to fly "normal" rockets. I'll take a look at the surface finish factor again and see what it's looking like. I know the weight was pretty close to actual.

So you have a chart for streamers and chutes? Can you post that? I'd really like to have a look!
 

JTarmstr

Well-known member
#8
Unfortunately I'm contemplating an L1 attempt at some point so I need a fairly accurate assessment of coasting time (trying to avoid extra gadgets, dual deploy, etc). I'll probably make an end run around it by flying an R/C glider as my L1, but that does nothing for my desire to occasionally use said L1 to fly "normal" rockets. I'll take a look at the surface finish factor again and see what it's looking like. I know the weight was pretty close to actual.

So you have a chart for streamers and chutes? Can you post that? I'd really like to have a look!
Yeah i dont know much about hauling a glider into the sky. Unfortunately the chart is from the book MAKE: Rockets so i dont know if i can post it because its illegal to reproduce books, i would have to look a bit more. But i might be able to make my own or search one up on the internet if you want.
 

FAI-F1D

Free Flight Indoorist
#9
Yeah i dont know much about hauling a glider into the sky. Unfortunately the chart is from the book MAKE: Rockets so i dont know if i can post it because its illegal to reproduce books, i would have to look a bit more. But i might be able to make my own or search one up on the internet if you want.
Huh...I can pick it up used for a decent price. I'll buy it. Thanks!
 

SlingShot

Maneuvering With Purpose
#11
So I've noticed lots of us here like rockets, and there's not really a subforum for rocketry here, so I'm just slapping this in one of the more active parts of the forum and we'll see where it goes.

What's the point? Well just post your rockets here and see where it goes.

I'll start. My son absolutely loves rockets (I have no idea why a kid in a family whose previous 3 generations have been utterly obsessed with rockets would like rockets. None whatsoever). So I designed a rocket for him and included some of the design principles for safe own-design rockets in the process. Have a look at the process and my moment of utter stupid:

And my parenting recovery:

Obviously I'm a long time rocketry advocate here. And for the uninitiated, here's an example:
He loves his Daddy and I love the cats too! Protect them please! Great work. You've been busy lately! :cool:
 

FAI-F1D

Free Flight Indoorist
#12
He loves his Daddy and I love the cats too! Protect them please! Great work. You've been busy lately! :cool:
Yeah we try to keep them away from the pad. If they get too close we do run them off. Fortunately the motors in most of these videos are very reliable. I do think I need to work on some high-visibility designs if I build any more conventional rockets. They have a much higher terminal velocity than the rocket gliders and there have been some incidents with such models when the ejection charges fail (and they occasionally do). You need a good high-vis color scheme or even some lights when flying such models in low light conditions. I've gotten a bit too comfortable with the comparative safety of boost gliders.
 

JTarmstr

Well-known member
#15
Thought i would share this. Its my 4 motor cluster build. Still needs some paint and i am open to suggestions for a paint scheme, i will be testing it next time i go to my large launch site (somewhere in the next 6 months).
Rocket Thing.jpeg


My Estes Bullpup is below for scale.
 
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FAI-F1D

Free Flight Indoorist
#16
That cluster bird looks cool!

Wow. Which company is that? i have only built estes and quest but that looks like an interesting one.
It's from a new outfit in Alabama called Mach I Rocketry. They specialize in fiberglass airframes. For what you're getting, the prices are very, very low.

There are quite a few model/sport rocket companies out there selling really cool stuff. Spend some time digging through eRockets, Aerospace Specialty Products, LOC Precision, etc, and get ready for an eye opener on what's available. I also see that under their new leadership, Estes has got some really good stuff coming out now.

Bear in mind that Mach I and several similar outfits are marketing within the sport rocketry community and so include very little in terms of instructions. Not really surprising though when you're selling something that requires qualify epoxy for the entire assembly process.
 

FAI-F1D

Free Flight Indoorist
#17
Oh, forgot one: rocketcraftmaster.com is an outfit in Russia which sells some of the finest model rockets ever created. All oriented toward FAI contest flying, but they make nice sport model too.
 

JTarmstr

Well-known member
#19
Bear in mind that Mach I and several similar outfits are marketing within the sport rocketry community and so include very little in terms of instructions. Not really surprising though when you're selling something that requires qualify epoxy for the entire assembly process.
Ok, been wanting to try sport rocketry for a while. Thanks!

I have actually had a bit of an idea for a rocket that i wanted to build, basically its my own spin on the Estes Comanche-3. What i want to do is make it so the recovery goes a bit faster that way the rocket cant go as far. After the first and second stages are expended, i want to blow the third stage in two right above the fins/motor. So stage three will tumble and the front portion of stage three will have either a really small streamer or parachute deploy on the top half. This is pretty complicated for a Estes rocket but i think it will work, will edit with drawings at a later point.