CG and CP which where how to figure on a Saturn V estes Rocket

[Sterk03]

Saturn V estes CG and CP so what is an acurate way to find both? and the cg has to be higher then the CP?

 

[heada]

CG (Center of gravity) is easily found by balancing it. The balance point is the CG. The CP is best found in a simulator program (Rocsim, OpenRocket, etc.) but there are some "low-tech" ways as well. Cardboard cutout, swing test, Barrowman equations by hand, etc.

 

[neil_w]

Remember to measure CG in fully ready-to-fly configuration, with motor and everything.

 

[Sterk03]

Thanks I have done the balance test with the cardboard but was told its not that accurate and you mention the swing test could you explain. Ok I don't really want to join a club just to get the formula to figure it out but maybe down the road. Thanks

Sterk03

 

[neil_w]

OpenRocket is your easiest path to success here, not that creating a decent model of a Saturn V is trivial. It's possible someone out there might already have one...

 

[kuririn]

If you need to find Open Rocket or Rocksim files check the libraries at EMRR first.
And by the way Open Rocket can read Rocksim files.
https://www.rocketreviews.com/unknown-estes-saturn-v-1100-scale.htmlI assume you mean the 1/100 and not the plastic 1/200 Saturn V.
It's for an earlier model than the current but the external dimensions are the same, so the CP should also be the same. Assuming whoever drew it up did so accurately of course.
Later as you learn to use OR you can draw up your own files.

 

[GlenP]

Swing test or string test requires a string to be securely fastened to the model at the balance point, the c.g. Then you slowly start to swing it around you going faster and if you have sufficient stability the rocket should point nose into direction of travel, not tail first. The model should be loaded with as large and heavy motor and chute and wadding like ready for flight. Feel free to yell Yippie Kai Yay! If you can swing it up high over your head.

 

[neil_w]

If you need to find Open Rocket or Rocksim files check the libraries at EMRR first.
And by the way Open Rocket can read Rocksim files.
https://www.rocketreviews.com/unknown-estes-saturn-v-1100-scale.htmlI assume you mean the 1/100 and not the plastic 1/200 Saturn V.
It's for an earlier model than the current but the external dimensions are the same, so the CP should also be the same. Assuming whoever drew it up did so accurately of course.
Later as you learn to use OR you can draw up your own files.

Note that OR can read many Rocksim files. I can definitely read that one, and it yields CP 24.6" from the front, *not including* the tower. The location seems to match the CP marking in the image at the right side of the page Kuririn linked to.

That is pretty far forward for CP, not surprising with the small fins.

 

[jrap330]

Thanks I have done the balance test with the cardboard but was told its not that accurate and you mention the swing test could you explain. Ok I don't really want to join a club just to get the formula to figure it out but maybe down the road. Thanks

Sterk03

If this is the real kit...do not risk swinging it? It is delicate. If you are wondering about motors and which will give you a stable flight..ask this forum......by now hundreds of people have built it......flown it and they can tell you what motors they used and if they needed to add any weight. Just because everyone states..."hey do a SIM, does not mean you have to..." If people can supply their actual historical, personal knowledge.... then use it for recommended motors and added weight. And , YES if you want to...check out EMMR/rocketreviews.com for sim file. And looks like Neil gavev you the data.


AGAIN- Do not swing, if this is the KIT!

 

[cerving]

The Estes Saturn V (the 1/100 kit) really needs a bit of nose weight to be stable, especially with the original fins. This is not a high flying rocket, so adding an ounce or two of nose weight isn't going to affect the apogee all that much, and does wonders for the stability.

 

[jrap330]

Can anyone recommend the motors they have used and any added nose cone for those motors. I hate to think this poor guy thinks he needs to do a swing test or even a SIM.

 

[GlenP]

Here's some info on the cardboard cut out method to determine CP location. You can make a smaller scale version of the cardboard cutout, it does not need to be full size of the actual rocket.
https://www.apogeerockets.com/education/downloads/Newsletter18.pdf

and a demo of a swing test for a small model rocket. Nothing wrong with swing testing a larger rocket if you can manage not damaging it, just take extra care with the tower of course. You can decide for yourself if you want to risk it.

 

[Sterk03]

thanks for all the great info sorry it took me a while to get back to you on this matter. I have added size to the original fins and thought that would help and the cp was about 1 inch in front of the CG, and yes I flew it again on a E engine but it still tipped over to the horizontal flight. So I'm guessing until I add more weight up front it will continue to tip, as I'm hesitant to make it heavier then it is now! But the other more experienced rocket people at the launch said it needed a bigger engine and they have yet to see this rocket go straight up yet It is built to the Estes's plans and it says it can fly on a D engine????I would like to see that? SO yes as the posts have said has anyone found the answer for this Estes Saturn V and I have the original which then was augmented with the E engine mod kit Estes put out later. I think most feel its so underpowered that a larger engine would do the trick but I do feel like more weight will also do the trick but lower the total altitude. Its going to need some room to level off and charge for the parachutes to deploy or its just going to crash into the earth again. I have bought 2 of the newer anniversary kit models from estes so I can experiment with it but I will keep trying until I get it right. I also probably will try and get the sim test and see what it comes up to, I just don't understand how Estes can slae a rocket out of the box that will not fly???

Thanks again for all the info.

 

[neil_w]

What you're showing there is usually the result of insufficient thrust rather than instability. I would recommend an Aerotech E motor, either the E15/E20-4 or even better the E30-4 to get it moving faster off the rod.

Sometimes Estes recommends minimum motors that are really a bit marginal, particularly when they don't have any higher-thrust motors of their own manufacture to recommend. The Aerotech single-use E motors are a great solution for 24mm rockets; just make sure your launch controller has sufficient juice to start them.

 

[kuririn]

The latest re-issue of the Sat. V (#1969) no longer recommends the D motor.
E12 and E30 are the only recommended motors.
This is for a stock build.
If you add even more nose weight you may need engines with more oomph.

 

[jrap330]

Send a Message for BobbyG23...he successfully using an Aerotech E30 engine and 6 foot rod>when the Estes E12 was not enough. He Went from Boyce Fins back to Estes Fins which are bigger . CP is behind CG, you got it backwards. This was back on Jun 20. The Kit needs to be light because it flies on an Estes D engine provided you did not built it heavy and no winds. Thread is Titled. "Estes Saturn V #2157 Build thread"-

 

[mo2872]

Hmmm, recently acquired some F39's........

 

[Sterk03]

Thanks for all the reply’s. Yes I built it stock originally and when it failed on the D engine then I got the E engine mod from Estes and installed larger fins as in the pictures but still a leaner yes I agree no way it can work on a D or E from Estes that’s why I ask how can they sell it that way. Yes I missed typed I know the CP and CG position which is what I originally thought was the cause but I also heard about more engine power and I will do that and add nose weight to correct the CP I’m just experimenting so when I build the new Saturn V this winter I want to have everything correct do I don’t go through it again. Thanks for the info and that’s what I was looking for who has one and if it flys well what did they do and what engine I will check that thread.

till the next launch after rebuilding it for the third time but no launch tower this time.

sterk03

 

[Antares JS]

The Saturn V Skylab release coming out in a few months apparently has the E16 and F15 for recommended motors, meaning it's going to have what it should have had all along: a 29mm motor mount.

Looking forward to that one.

 

[cerving]

The Estes Saturn V begs for an AT/CTI 29mm motor, or at least a 24mm F. I wouldn't fly it on anything with under 24n of average thrust (i.e. AT 24-40 F24), more is better. A longer rod (at least 6') is a necessity, too. You're on the right track by enlarging the fins... I ended up with 4 oz of nose weight in mine, but again I hacked it up and used a 29mm motor mount, wood centering rings, heavier body tubing (from BMS), and about 50% larger all-wood fins. Flew it with a CTI 29/1G F59, it flew great.

 

[PieroAcme]

Hi Sterk, I agree with the above Cerving statements.
For a good fly with Estes Saturn V 1/100 you need at least an AT F24-4.
I use 35g weight in the nose cone and enlarged fins.

Here the video for having an idea how it goes with F24-4

 

[bobbyg23]

I ended up having great success with an aerotech E30-4.

 

[Sterk03]

Thanks again for the great video's I hope to get mine repaired and in the air soon. So I'm assuming the F24-4 is an aerotech engine and how will that mate with my Estes E engine motor mount? Much higher flight and longer then the E 30-4 but I would be happy with either. So i'm guessing both were balance as far as CP or the amount of thrust overrode any short comings in CP balance? CP above CG...
Thanks again for the info Nice Flights !

sterk

 

[Nytrunner]

The F24 is an Aerotech reloadable motor. It requires the 24/40 case and closures, and will fit in an estes D-sized motor mount. If you use it in the E mount, you'll need to use the little cardboard spacer in front if it in the tube.

As far as balance and CP CG goes, you should really use a simulation program to determine the CP, then you can make usre that your flight-loaded rocket will have its CG in front of the CP by ~1 lage body diameter.

CP above CG..

THis is the opposite of how it's supposed to go

 

[Sterk03]

Thanks for your answers, I'm not saying what I'm visualizing the CG in front of the CP I keep saying it wrong but got it. Thanks

Sterk03

 

[Sterk03]

I could not find a aerotect F24-4 or and Estes E30-4. The estes site had a picture of them but no info on buying it the E30-4 and the Aerotech google did not show an engine that was labeled 24-4 so I will need further info where to find them? I saw a 24-40 so is this a 24-4? I'm not familiar with aerotect numbers yet.

Thanks again. I did a CP on the estes Mean Machine and it seems like cp is higher on this also so I put my camera on almost the nose or add weight to the nose, this does not make sense to me if its a deisigned rocket it should be stable out of the box not have to do measurements on it to then correct the stability? I guess that is part of the hobby?

Sterk03

 

[PieroAcme]

Hi Sterk, here a link for the F24-4 . These are the reload.

https://www.buyrocketmotors.com/aerotech-f24-white-lightning-rms-24-40-3-pack/

 

[heada]

E30-4 can be found as well.

https://www.csrocketry.com/rocket-m...erotech-e30-4t-blue-thunder-rocket-motor.html

 

[Nytrunner]

I could not find a aerotect F24-4 or and Estes E30-4. The estes site had a picture of them but no info on buying it the E30-4 and the Aerotech google did not show an engine that was labeled 24-4 so I will need further info where to find them? I saw a 24-40 so is this a 24-4? I'm not familiar with aerotect numbers yet.

Aerotech F24-4, it comes in a 3-pack of the propellant kits:
https://www.csrocketry.com/rocket-m...tech-f24-4w-white-lightning-rocket-motor.html
Note, it is a propellant kit and requires the 24/40 reloadable motor case:
https://www.csrocketry.com/rocket-m...e/aerotech-24/40-complete-motor-hardware.html
The E30 is actually an Aerotech motor*. It is a single use complete motor (no reload case) and comes in a 2-pack:
https://www.csrocketry.com/rocket-m...erotech-e30-4t-blue-thunder-rocket-motor.html*There used to be Estes branded E30s, but they were still AT motors

Thanks again. I did a CP on the estes Mean Machine and it seems like cp is higher on this also so I put my camera on almost the nose or add weight to the nose, this does not make sense to me if its a designed rocket it should be stable out of the box not have to do measurements on it to then correct the stability? I guess that is part of the hobby?

What method do you use to determine CP? The Estes Mean Machine should be stable if built according to the instructions and with proper use of adhesives (No massive amounts of glue or extra weight in the back, no massive drippy heavy coats of paint) and flown on the recommended motors.
That being said:
-The CP of a rocket is a result of the design of the rocket (body/fins/nose). It is not alterable by the flier without changing the external design of the rocket (like adding a draggy camera somewhere).
-BUT the CG is subject to change based on a) how much adhesive/paint you use (and where), b) modifications you make to the structure, c) additions like camera's or other objects, d) motor choice: each different motor will change the loaded weight and CG of the rocket. Heavier motors may pull the CG too far back and require noseweight to return to a stable configuration.

Looking at those aspects of your build and flight are what goes into being a skilled hobby rocketeer.

 

[PieroAcme]

This is the case

https://www.siriusrocketry.biz/ishop/aerotech-rms-24-40-motor-complete-165.html
In this case 24 is the diameter in mm and 40 the lenght