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How to Find the Center of Pressure on a Rocket
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- Опубліковано 7 сер 2024
- www.ApogeeRockets.com -
Do you want to figure out where the Center-of-Pressure is on your rocket? What are the various methods you can use to find that location? What is the Center-of-Pressure, and why is it important?
This video covers a brief description of the Center of Gravity (CG), explains what Center of Pressure (CP) is, how you can determine where it is, and why that is important. It also explains various methods that have been used to find the CP, and why they may or may not be good options.
If you've ever been confused by exactly what the Center of Pressure is and why it is so hard to determine, this video is a good resource.
Note: If you want to see how to build the inexpensive wind tunnel shown in the video, check out the Peak-of-Flight Newsletter #252: www.apogeerockets.com/educati....
The Barrowman file referenced in the video is available at: www.apogeerockets.com/downloa...
Probably the best explanation of CP that I've come across.
Thank you.
Thanks for this explanation! I could never comprehend Center of Pressure, but your demonstration made the concept clear. Good job as always!
Great video! Thank you, Tim, for sharing your rocketry expertise.
Nice wind tunnel Tim, a low-tech solution works great thanks for the video
Tim, thank you for sharing this.
I love these videos keep them coming I've been building model rockets since 1984 and these are insightful and helpful!
Very good, the best really is found it full of practical advice. Thank you very much.
Thank you for the excellent presentation and explanation.
A lot of educational information Thanks for the video
Thank you. You sir are a fantastic communicator
Thank you kindly
This is very helpful. I have been designing some 3d printed rockets and I have just been hoping my designs would be stable by making extra large fins
Be careful. If you make your fins too large, they will become more likely to shear off and you can risk overcorrecting into the wind(your rocket can go sideways into the direction of the wind).
That Navy rocket is pretty sweet!🚀 Thanks for the explanation.
Great video
50 years ago we had a great time creating our own rockets. I'm learning so much from these videos that I'm getting serious about the hobby again.
We'll be lucky to have you back in the hobby again. We still need experienced people to set the next generation on the right path.
Thanks for sharing the wonderful video clip Tim. I am a teacher and teach model Rocketry to Indian school students at India. This will help me a lot. Thanks again.
Are you a member of the rockteer?
@@ratneshsoni9045 yes and what about you?
@@jodigant I'm a amateur rockteer enthusiast... From Uttar Pradesh... And yes I'm also a part of the rockteer
Nice to know that.
Not boring lol! Great video
I love the primer
super cool information! thank you very much! I had a rocket that was unstable, the Estes mini honest john, did about 2ft corkescrews on its first launch and flew in an arc instead of straight up. will be building a wind tunnel this weekend. Planning to build the Aspire as well, want to get that absoloutely perfect so this will help too.
Thank you
so these gravity and pressure points will move or not with time i mean if rocket is fired and it using its fuel so it will be shifting or not
Two questions... You stated the forces in play that impact both CP and CG, but then, when you found the CG, you used an empty rocket with no motor, and when you found the CP, you didn't include thrust when doing the wind tunnel test. The motor wasn't firing. So, how do you account for the motor weight and the thrust of the motor?
Thank you Sir
All the best
Hello i had the guy at my local science store said u can take the diameter measurement x it by 2 and take that from the front side of the base of the fin and measure basically from the fin measure forward double the diameter does this sound right also your vids are not boring i cant tell u how much u have tought me thank u
I'm sorry. I don't know what you are referring to.
Thanks for another great video. What is the name of the Navy rocket in this video. Its really nice!
The rocket is called Sea Sting.
I found my new hobby,sir,can my rocket fly if rocket has sugar as engine and i think KNO3 to be flamable.
And where i centar of mass?is centar of mass still affect rocket?
Great video! Could you tell me the name of this fixture you use for finding the CP? Also, where can I buy it?
Click on the description of the video and download the newsletter article.
So when they refer to the center of drag is this what they are talking about? Or is the center of pressure between the center of drag and center of gravity?
Center of "Drag" is not usually talked about. It is typically called Center of Pressure. Another one is Center of Gravity. But not drag. Not in model rocketry at least.
@Apogee Components >>> *Everyone's a critic!*
😝😝😝😝
I’ve had excellent results with the string method. The string has to be at least six feet (2m) in length .
Glad that worked for you. It doesn't always.
Interesting idea for a wind tunnel! Since you made that rather complex rig to hold the rocket, why not make a pair of 3D printed feet that both distribute the pressure from the pivot points on that rig, and make a stable pivot point for the rig. Secure the feet with two rubber bands so the feet won't slide along the body tube.
Good idea. But I don't know what your idea looks like. you'd have to send me a picture.
Does the weight of the rocket motor need to be considered?
Not for Center-of-Pressure.
Se puede atar a un vehículo con una cuerda y hacer la prueba a alta velocidad.
Q.....when your doing your wind tunnel or swing test does that include the engine?
Swing test? I never recommended doing a swing test. But in a wind tunnel, we are measuring aerodynamic forces, not gravitational ones. So does a rocket motor affect the aerodynamic forces, or not?
@@apogeerockets got it, but shouldn't the weight of the engine be taken into consideration when trying to determine center of gravity? Now don't get me wrong, I'm just trying to get as much info about this subject as I can. Besides, I'm too lazy to do the mathematical equations
@@uncled6403 Yes. The motors should be included for center of gravity
I like testing my rockets with Kerbal Space Program
But there is a limit for pushing the centre of pressure backward ..... If it's positioned far back it may comprehensively reduce the controllability of the rocket.....therefore the last version of fins that u suggested are not efficient
As long as the CG is ahead of the CP, the rocket will be stable.
how dose this translate to my rocket flying from the motor out the back not swinging from a string?how dose knowing this make my rocket fly ? do i put my fins there ?
The fins have to be attached at the rear of the rocket. That is where they go for a stable rocket that flies straight. I'm not a fan of the swing test because it often fails - the rocket will fly backwards when swung on the string. If you don't have a wind-tunnel, then use a software program like RockSim - Available at www.Apogeerockets.com
Wouldn't adding length to the front also change the Center of pressure?
Yes. That is my best advice for moving the CP: Make the rocket longer.
@@epicezra123 This stuff is easy to see in a software like RockSim. you can move parts around and change lengths and see the CP and CG move around. I recommend you give it a try.
Shukriya...
How can we get the center of pressure behind the center of mass???
Try one of these: Bigger fins, More Fins, Put them further back on the rocket, Make the rocket longer, Sweep the fins rearward.
Adding weight to the nose works too.
Do you ship electronics in India?
You can check our website for shipping details.
Unfortunately no
So by really paying attention to what you are saying, the center of pressure is in reality just more drag on the tail of the rocket then the front of the rocket.
not boring
3 year old video but I am going to say years ago I would throw away the steel washer that was in the kit. Later in life I found out what the steel washer was for. Ha.
Leaf blower
If the center of gravity is too far behind the center of pressure, then the rocket will first go downwind, and then tend to turn towards the ground. Unless, of course, the rocket has front rudders.
@4:04 "if i turn on the wind tunnel, if the rocket points into the air stream...ummm this tells me...nothing, uh.. but I will show you that works"
What!! In the late 60s we used the string, on a fishing pole, out the car window. Wind tunnel my butt.
Contstuction!? LOL.
Why would you need to know that?
You need to know the location of the CP, because it will determine if your rocket is stable or not. For the rocket to be stable and fly straight, the CP location needs to be behind the center-of-gravity (where it balances on your finger). That's it. I'm sure you can tell that this isn't very important information at all.
@@apogeerockets is that sarcasm? If you can rotate it on a string and it travels around without issue, isn't it stable? Or would it mean that if a side wind hit it in flight it would become unstable? I always had worried about balance, never had stability issues on the kits, maybe on custom builds where you're making an unproven design. I'm not a rocket scientist. Just a hobbyist. I do like your videos.
@@capnhardway Yes. It was sarcasm. It is very important to know where the CP is. But I'm not a fan of swing tests. You can read why at: www.apogeerockets.com/education/downloads/Newsletter53.pdf
@@apogeerockets admittedly was a stupid question. Would you normally encounter difficulties in say an Apogee or Estes kit If they were built to specs?
@@capnhardway No problems. Manufacturers will do the proof of stability before making the kit available to customers. Who wants to buy a kit and see it smashed to bits on the first launch.
Thats not CP ... thats C of Drag !! The drag is equal on both sides ... but again thats not the whole story ... there is lift and drag at different Angles of Incidence ..etc. I mean its not as simple ... I have seen people spinning it around and stuff ! IDK its lot more !
Isn't there a way to find this with math?
Yes.But who wants to use the Barrowman Equations. Use software...
I do!
You didn't tell viewers why you want to know the center of pressure
Why so long? Bring some new material please
This is excellent content, and it is new material to many of us.
IMHO the video length is just right.
Just saying..
This guy is a complete idiot.
Explains center of gravity of a rocket on the shear plane.
Just so wrong
What a dumb ass.
You could be right
This is why rockets can not work in space. Because there is no lift , drag, resistance or pressure in the vacuum of space.
U mean an aircraft* ?
There are other ways to control a vehicle once it's left the atmosphere.