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

[jrap330]

OK OK I mis-spoke I know CG is above CP.. I got it. I've been busy with life but let me answer a few questions. I figured out the CP with the cardboard cut out I have not ventured into the rocksim but now I know I will have to. So if I have a proper CP and it is below the CG and I put in the engines Estes said should work and the sale of the rocket is based on it it will fly. I did not overweight mine I did not slop paint on it I did not attach heavy metal objects to it but it would not fly until I experimented with larger engines then Estes called for...That's my point..... I balanced the rocket to acquire the CG with everything loaded on the rocket like it was going to fly. I was not using heavier motors then suggested and yet it was underpowered.

I understand about the F24 Aerotech motor and you load it I got that and have one but not to that stage yet. I don't want to get into it but someone mentioned about cg being in front of cp by one body diameter tube size if you do that on a Saturn V you have to add a lot of weight into the nose to make it stable and now how is that to have been flown out of the box with the suggested engines. Kits other then Estes provide a cg if built as shown, Estes gives no advice or any info on cg or stability???? I'm on some other thread about my two versions of Saturn V and the amount of weight you need to make it stable by the information you have provided, rocksim or no rocksim now its so heavy trying to get off the pad and reaching 250 feet and this is on an Aerotech engine. Ok one area I need more understanding cause trying to read about the aerotech engines the different blue,white,black.. and all the numbers given and how one article talks about power to get a heavy rocket off the pad but it does not have p-ower to accelerate, or this color will accelerate or for heavy weight, so ok what numbers are you using to get a more powerful engine(one that will liftoff the rocket and accelerate to a safe altitude with ample room for the delay to happen and then the chute to come out and not make a hail Mary landing????? They have numbers in 8 different categories and weight of max liftoff??? so how do you look at all the numbers and say this has enough total power to launch this rocket. I used a E30-4T and it got the Saturn V to 250feet, but I wanted more room and so I tried a F44-4W and a F32-4T but these did not increase the altitude what so ever so I might as well use a E30 Aerotech so what did I read wrong and how do you pull out the real number of these engines other then by experimenting...I'll take any advice. Ok enough for now
Sterk03

Understand your concern...but you know 250 is not bad. Issue is will all 3 chutes deployed and I for one always consider changing out the 2 chutes on the body for just 1 chute.....either the 24 incher or a larger one. BobbyG23 did a built thread last year and after crashing on an E12 ..he tried a E30 and like the result. Check out his build thread.....search Saturn V build thread.

 

[Sterk03]

Just to update things yes I get if it is built light and little weight is added it might fly on a D12-3 but if you build it light and accordting to the plans it’s as light as you can make it but then when you measure cog and add nose weight to make it stable you have to add too much weight to get it in the stable range that there is no way to fly it with a D12-3 that is all I’m saying. SoI have had successful flights with the AeroTech E30-4T but these are barely 200 feet with using a lot more power then a D and I.m trying to get it higher then that just for a little more safety margin for chutes. So I did see theF24 rocket video very impressive I.m not sure I want it that high I. The limited launch area but I used a F44 thinking this will make it go higher plus fit I the old Saturn that can only take a (D) size motor and it maybe went not as high as the E30.
yes I am not used to theAerotech and I,m trying to learn how to read the numbers given with the engines and which numbers are most important in motor selection but felt a F should be more thena E or D motor and it was not, So engine letter is not enough soI need to find the out of all the numbers listed which ones I need to use for engine selection, I was taking notice of liftoff weight also and though this should be helpful but not sure it was. Also the AeroTech article about flame color which is not only about tracking the rocket but also liftoff power and acceleration etc.

I need a more accurate graph f the possible AeroTech motors and definitions on all the columns of numbers and use them and test fly some larger motors.
Again thanks for all the help.
At least I have accomplished several successful flights thanks to the E30-4T AeroTech.

Sterk 03

 

[bobbyg23]

Understand your concern...but you know 250 is not bad. Issue is will all 3 chutes deployed and I for one always consider changing out the 2 chutes on the body for just 1 chute.....either the 24 incher or a larger one. BobbyG23 did a built thread last year and after crashing on an E12 ..he tried a E30 and like the result. Check out his build thread.....search Saturn V build thread.

I did. I learned a lot from that build. that rocket is my avatar pic

 

[bobbyg23]

For motors, you really need to look at its thrust curve. The E30 has an initial thrust of 11lbs. That gives it its pop off the pad to get enough airspeed so the fins can take over the stability. You can't just go by the letter. That is the total impulse range. To over simplify it, if I have an E motor, a 12 would have lower initial thrust but a longer burn time. A 30 would have higher initial thrust with a shorter burn time. Don't be concerned with the propellent color, look at the thrust curve to figure out what you need. A thrust to weight ratio of 5:1 or higher is preferable in my opinion.

 

[Antares JS]

The limited launch area but I used a F44 thinking this will make it go higher plus fit I the old Saturn that can only take a (D) size motor and it maybe went not as high as the E30.

The F44 is a baby F that doesn't have much more total impulse than an E. It has higher thrust (44 N average vs. 30 N in the E30) but that's not always a good thing, especially on a draggy rocket like a Saturn V. More thrust gets the rocket going faster, but drag also increases with speed. These two reasons, that the F44 does not have much more impulse than the E30 and the higher speed causing higher drag, are probably the reasons why the Saturn V didn't go higher on the F44 than the E30.

 

[bobbyg23]

For instance, here is the thrustcurve chart for my saturn v. Everything else was too slow off the rod resulting in a less than desirable flight.

 

[Blast it Tom!]

You know, this one has me wondering... obviously the peak thrust and total implulse are key; you have to get the rocket moving fast enough to get off the rail and then keep burning until you get far enough from the ground. @bobbyg23 shows this nicely.

But as to the title... when I look at the Barrowman method for CP and other stability parameters, and think of how it would be applied to this rocket, I see a "nose cone" element, two transition elements 'way up front, and itsy-bitsy fairings/fins back at the back end. Now I am just learning the original method, so maybe there are updates/changes/improvements, but as I understand it, straight cylindrical sections of body tube aren't counted. Yet for this beauty, they make up a HUGE part of the area. So how does that work?

And isn't it amazing that in real life they can balance 6.2 million pounds of mass 363ft tall, on a pillar of flaming gas, like balancing a broomstick on the palm of your hand? I dorn't know if I'll ever loose my sense of marvel over that. Actually, I hope I don't.

 

[Antares JS]

they make up a HUGE part of the area. So how does that work?

My understanding is that the reason body tubes are left out of barrowman equations is because the surface of the body tube is parallel to the airflow, and so theoretically isn't bending/affecting it like your forward surfaces (nose/transitions) and fins are.

 

[smstachwick]

You know, this one has me wondering... obviously the peak thrust and total implulse are key; you have to get the rocket moving fast enough to get off the rail and then keep burning until you get far enough from the ground. @bobbyg23 shows this nicely.

But as to the title... when I look at the Barrowman method for CP and other stability parameters, and think of how it would be applied to this rocket, I see a "nose cone" element, two transition elements 'way up front, and itsy-bitsy fairings/fins back at the back end. Now I am just learning the original method, so maybe there are updates/changes/improvements, but as I understand it, straight cylindrical sections of body tube aren't counted. Yet for this beauty, they make up a HUGE part of the area. So how does that work?

And isn't it amazing that in real life they can balance 6.2 million pounds of mass 363ft tall, on a pillar of flaming gas, like balancing a broomstick on the palm of your hand? I dorn't know if I'll ever loose my sense of marvel over that. Actually, I hope I don't.

I’ve been looking at some of the principles behind the simplified Barrowman equation everyone’s familiar with, and there are some idiosyncrasies to watch out for. If you have a wide BT on the aft end and a teeny tiny nose, it’s entirely possible for the calculations to think that the fins are going to be more effective than they actually are because they stick so far out into the airstream and give you a CP much further to the rear than in reality. Apogee had a great article on this regarding RockSim’s stability calculations and its incorporation of elements of the full Barrowman calculations (i.e. accounting for a specific nose shape, unusual fin configurations, etc., all of which were taken into account in Barrowman’s original work) into the program.

But considering that this is a kit build that has already demonstrated successful flight, I don’t think this will be an issue. As long as the components aren’t damaged and @Sterk03 didn’t go crazy with adhesives and packs the parachute as close to the nose as possible, the CG and CP should be pretty close to the rocket’s design.

As far as flight safety, I can say that I’ve had some successful sub-100ft flights with underpowered rockets on a 2-second delay. In my case it was an Estes Firestreak deploying a streamer on a 1/4A3-2T, which is a smaller motor than is recommended. I’ve also flown an Estes Phantom (basically an Alpha III with transparent plastic components) to about 65 ft on an 18mm 1/2A6-2 and got it back without damage despite the parachute not opening completely.

A 100ft flight on a D12-3 in this bird (per the Estes specifications) should be plenty safe.

Even if it’s too long of a delay, you’re not likely to suffer major structural damage or create an unreasonable hazard from a late deployment or ground impact when you’re dealing with an apogee that low. Seeing performance figures for this thing and comparing it to my own experience with similar flights (albeit at a smaller scale) leads me to conclude that perhaps our friend Sterk is overthinking things here. A build to specification and with the recommended motors should get this thing in the air and back on the ground in flyable condition or needing only minor repairs.

 

[Blast it Tom!]

Well, I'll admit that my thoughts were toward an eventual Saturn V of my own someday, perhaps not a kit, but a "build of a lifetime" model. I'd agree with you and Sterk that a retail kit should fly as advertised if built according to their instructions - as an engineer I'd be embarrased if a product of mine was found to underperform, you'd think I'd have tested it quite exhaustively.

 

[Sterk03]

Thanks for all the response and info. I think I'm going with the thrust curve. I did not go crazy with the building material and glue and to me the chutes can only go in one area as per the instructions and room for the chutes which would be the top of the first stage body at 31/2 inches wide. My first original flight was with the 12-3 and with the original fins. I did not do a cg or cp test on that flight, at that point in my career I just built them as per instructions and flew them ...no problem, but the Saturn V was a different animal. Since retiring and trying to get more serious about the rockets I took out my Saturn V and said time to get her flying correctly. My first change was with the fins...I made them bigger cause that is the only thing at that time prior to CG/CP I could think of. The original flight just went horizontal and I did not walk off how far it flew but it was not up! So I put the bigger fins on and yes was clueless (still am) about I added weight to the bottom and did not do any calculations. So after the second flight I added some weight in the nose, and it flew more vertical but still hit earth before the charge for the chutes could let them deploy. After post s in this forum I then took the CP cardboard cutout and cg balance tests with the fully loaded ready to fly rocket and I got the same layover after liftoff. It just struggled on the 12-3 so I finally went to the Aerotech after your posts and put in the E30-4T and this was my first successful complete flight. Yippie!
So yes ok I guess I should be happy for it but I felt it should be able to go higher with that size motor. Hence I tried the F44 but again not understanding the thrust info but it did say a higher liftoff weight and to me that was what I was missing. I know you cannot go by the color but in Aerotech web sight it lists the colors and does say lift off more weight and accelerate faster in the description of its colors. I got it that is not the main factor but it did catch my eye. I do have a reloadable aerotech but would like someone to help with the loading of it but also looking for reports on what larger engines were successful in their Saturn V. I did see one on youtube but it seemed to go very high and I do not really want that at this point, I'd like to work up that that point. I now will not be flying the original Saturn V for a while as the upper stages and command module are stuck in a high tree with the cows guarding it in a farmers back yard!
I have the 30th anniversary rocket ready to go sort of but now I'm back to the original fins not enlarged but built with the fins that the model came with,and to me again they should fly with these fins but I don't know that yet. I eel if I get the CP and Cg in the zone and use an aerotech although the box says an Estes motor will fly it( I don't believe it) I want to launch it with the stock fins. My last post I mention about stability. I get it the first one I flew without looking at it but now I feel the weight in the nose is way to much so now I have a even heavier rocket to launch then the original one but it's built to spec. I'm not sure I need Cg above CP by 31/2 inches or so which the Rocket manual says it should be...that makes it way to heavy. That's why I was going to continue to experiment with the original one and slowly decrease the weight in the nose to see if it was stability or engine power for the failed flights. I had posted the pictures earlier and many comments said it looks underpowered not unstable and I agree. To be continued, but again thanks for all the input. Yes I am overthinking it put the E30-4T in it and go fly it.

 

[smstachwick]

Thanks for all the response and info. I think I'm going with the thrust curve. I did not go crazy with the building material and glue and to me the chutes can only go in one area as per the instructions and room for the chutes which would be the top of the first stage body at 31/2 inches wide. My first original flight was with the 12-3 and with the original fins. I did not do a cg or cp test on that flight, at that point in my career I just built them as per instructions and flew them ...no problem, but the Saturn V was a different animal. Since retiring and trying to get more serious about the rockets I took out my Saturn V and said time to get her flying correctly. My first change was with the fins...I made them bigger cause that is the only thing at that time prior to CG/CP I could think of. The original flight just went horizontal and I did not walk off how far it flew but it was not up! So I put the bigger fins on and yes was clueless (still am) about I added weight to the bottom and did not do any calculations. So after the second flight I added some weight in the nose, and it flew more vertical but still hit earth before the charge for the chutes could let them deploy. After post s in this forum I then took the CP cardboard cutout and cg balance tests with the fully loaded ready to fly rocket and I got the same layover after liftoff. It just struggled on the 12-3 so I finally went to the Aerotech after your posts and put in the E30-4T and this was my first successful complete flight. Yippie!
So yes ok I guess I should be happy for it but I felt it should be able to go higher with that size motor. Hence I tried the F44 but again not understanding the thrust info but it did say a higher liftoff weight and to me that was what I was missing. I know you cannot go by the color but in Aerotech web sight it lists the colors and does say lift off more weight and accelerate faster in the description of its colors. I got it that is not the main factor but it did catch my eye. I do have a reloadable aerotech but would like someone to help with the loading of it but also looking for reports on what larger engines were successful in their Saturn V. I did see one on youtube but it seemed to go very high and I do not really want that at this point, I'd like to work up that that point. I now will not be flying the original Saturn V for a while as the upper stages and command module are stuck in a high tree with the cows guarding it in a farmers back yard!
I have the 30th anniversary rocket ready to go sort of but now I'm back to the original fins not enlarged but built with the fins that the model came with,and to me again they should fly with these fins but I don't know that yet. I eel if I get the CP and Cg in the zone and use an aerotech although the box says an Estes motor will fly it( I don't believe it) I want to launch it with the stock fins. My last post I mention about stability. I get it the first one I flew without looking at it but now I feel the weight in the nose is way to much so now I have a even heavier rocket to launch then the original one but it's built to spec. I'm not sure I need Cg above CP by 31/2 inches or so which the Rocket manual says it should be...that makes it way to heavy. That's why I was going to continue to experiment with the original one and slowly decrease the weight in the nose to see if it was stability or engine power for the failed flights. I had posted the pictures earlier and many comments said it looks underpowered not unstable and I agree. To be continued, but again thanks for all the input. Yes I am overthinking it put the E30-4T in it and go fly it.

Here’s my input on the reloadables: They’re not as complicated or difficult as you might think they are. Assembly can be completed in about 10 minutes or so with a bit of practice. I’m sure you’ve built and flown airframes more challenging than that. I think the big hurdle is more mental, and it comes from not having seen many of the parts and equipment before. Once you get your casing, closures, reload kit, and whatever else may be required for your specific motor, take some time to familiarize yourself with them and try to understand their functions.

There are also tutorials for assembly on YouTube, if the manufacturer’s instructions aren’t doing it for you. A few things I wish I knew before getting started:

1. Use only the casing suggested by the reload kit’s manufacturer. Get it directly from the manufacturer (AeroTech, Cesaroni, whatever it may be) instead of getting one manufactured under license. One manufactured by a third party might not have the same quality control and manufacturing tolerances, even if advertised as being identical.
2. Identify and understand the purpose of the forward and aft closures. The casing is a tube that’s open at both ends. It looks a bit like a guitar slide (do a Google Image search if you don’t know that that is). If the case isn’t fully open at both ends, you may have gotten the case with the forward closure screwed on already. Not knowing this will make it difficult to understand and follow the assembly instructions.
3. Use a FRESH reload kit. Don’t use one that’s been sitting in a garage for 10 years, that’ll make it hard to put together and difficult to ignite.
4. Reloads have one or more liner tubes, small paper tubes that surround the propellant and delay grains and act as insulation, preventing the case from getting too hot. If the grains and liner tube don’t fit easily in the casing for one reason or another, don’t try to muscle it in there. You’ll damage the grains and your efforts to remove them may damage the casing. Instead, peel away an exterior layer from the liner tube to produce a looser fit.
5. Be ready to ruin a reload kit and possibly a casing before you get the thing assembled correctly. It might take you a couple tries.
6. Static fire an assembled motor before you fly it. If something goes wrong or if you’ve done something incorrectly, it’s better to learn by having that motor ruin whatever static setup you have than for it to destroy or damage an airframe.

I’m sure you’ll make some mistakes of your own that I haven’t warned you about here. That’s just part of the learning process.

 

[Sterk03]

Here’s my input on the reloadables: They’re not as complicated or difficult as you might think they are. Assembly can be completed in about 10 minutes or so with a bit of practice. I’m sure you’ve built and flown airframes are more challenging than that. I think the big hurdle is more mental, and it comes from not having seen many of the parts and equipment before. Once you get your casing, closures, reload kit, and whatever else may be required for your specific motor, take some time to familiarize yourself with them and try to understand their functions.

There are also tutorials for assembly on YouTube, if the manufacturer’s instructions aren’t doing it for you. A few things I wish I knew before getting started:

1. Use only the casing suggested by the reload kit’s manufacturer. Get it directly from the manufacturer (AeroTech, Cesaroni, whatever it may be) instead of getting one manufactured under license. One manufactured by a third party might not have the same quality control and manufacturing tolerances, even if advertised as being identical.
2. Identify and understand the purpose of the forward and aft closures. The casing is a tube that’s open at both ends. It looks a bit like a guitar slide (do a Google Image search if you don’t know that that is). If the case isn’t fully open at both ends, you may have gotten the case with the forward closure screwed on already. Not knowing this will make it difficult to understand and follow the assembly instructions.
3. Use a FRESH reload kit. Don’t use one that’s been sitting in a garage for 10 years, that’ll make it hard to put together and difficult to ignite.
4. Reloads have one or more liner tubes, small paper tubes that surround the propellant and delay grains and act as insulation, preventing the case from getting too hot. If the grains and liner tube don’t fit easily in the casing for one reason or another, don’t try to muscle it in there. You’ll damage the grains and your efforts to remove them may damage the casing. Instead, peel away an exterior layer from the liner tube to produce a looser fit.
5. Be ready to ruin a reload kit and possibly a casing before you get the thing assembled correctly. It might take you a couple tries.
6. Static fire an assembled motor before you fly it. If something goes wrong or if you’ve done something incorrectly, it’s better to learn by having that motor ruin whatever static setup you have than for it to destroy or damage an airframe.

I’m sure you’ll make some mistakes of your own that I haven’t warned you about here. That’s just part of the learning process.

Yes thanks for the tips, I’m not concerned about it just need the time to review it all and your thoughts and take my time but it hasn’t been a priority and I want to do it when I’m nit rushed. I will do a test fire and go to you tube if I need more reference. Thanks for your time and goid explanation on doing it right. It’s a big help. Sterk03

 

[Sterk03]

I am wondering if anyone has the time or wants something to do I am trying to compare my weight of the 3rd stage of my Saturn V 1/100 scale model. My complete 3rd stage with lem and service module and capsule and tower and parachute is (9.91 ounces). I think this is very heavy for this rocket just to get the CG/CP to where it is said to be. I have seen what weight others have added but what is the total weight of the body and chute for me to compare. To me this weight is not what Estes made this build for but it's right from the kit and instructions. Thanks
Sterk03

 

[smstachwick]

I am wondering if anyone has the time or wants something to do I am trying to compare my weight of the 3rd stage of my Saturn V 1/100 scale model. My complete 3rd stage with lem and service module and capsule and tower and parachute is (9.91 ounces). I think this is very heavy for this rocket just to get the CG/CP to where it is said to be. I have seen what weight others have added but what is the total weight of the body and chute for me to compare. To me this weight is not what Estes made this build for but it's right from the kit and instructions. Thanks
Sterk03

Good question. I’ll look into it and see if there are any specifications floating around on the kit, or perhaps a way to calculate it based on dimensions and materials. Maybe there’s a RockSim file around somewhere with this data already plugged in.

They produced a few different Saturn Vs in this scale over the years, do you happen to have a product number?

 

[smstachwick]

Apologies for posting back-to-back, just wanted to send you a push notification, just in case.

After doing some digging on rocketreviews.com , I've found that the Estes Saturn V kits and custom builds in this scale usually come in at 11 ounces, although the build by Tim Doll with a 29mm tipped the scales at 19. Assuming the 11 oz weight is closer to what Estes intended, I doubt very much that the whole forward section was 9.

I don't recall if you said anything about this, and I'm just quickly writing some notes so I haven't checked, but one thing that many builders did was to recess the motor mount a few inches into the body tube, moving the CG forward without having to put a lot of dead weight in the nose. That makes for a pretty tight parachute fit but it should be workable.

Looking at thrustcurve.org, there are a number of 24x70mm motors (Estes C11 and D12 standard) that go up to the low end of the F range, the most powerful of which is the Aerotech F39T delivering 49.7 N-s of total impulse. I can't imagine it would be too hard to get it up to a safe altitude on one of those. I should note, however, that all of the flight logs I found roughly matched yours, never breaking the 300ft range on an E and only hitting 400 on an F.

The 29mm motors are a different animal entirely, and the sky is very much the limit. Tim Doll ended up putting an F40W in his, and I know that the Aerotech G80T (137N-s) comes in a case of that same size. I'm not sure what kind of performance you'd get out of that, but I think that’d be the upper limit of what I’d want to put in there.

 

[SecondRow]

I am wondering if anyone has the time or wants something to do I am trying to compare my weight of the 3rd stage of my Saturn V 1/100 scale model. My complete 3rd stage with lem and service module and capsule and tower and parachute is (9.91 ounces). I think this is very heavy for this rocket just to get the CG/CP to where it is said to be. I have seen what weight others have added but what is the total weight of the body and chute for me to compare. To me this weight is not what Estes made this build for but it's right from the kit and instructions. Thanks
Sterk03

I have a stock built Estes 1/100 Saturn V that I fly regularly on Aerotech E30-4 motors. The 3rd stage weighs 6 oz and the total weight is 15.6 oz. Hope that helps.

 

[Sterk03]

Thanks to both of you for your info it's very helpful. I was basically asking about the third stage.
With the trying to get cg the body diameter3.5 inches above CP as per the standard rule I'm at 9.91 OZ and this puts the rocket close to 1LB 8OZ which seems awful heavy to me. That's why I'm questioning the diameter size in difference of CG/CP. I'm thinking if I reduce the weight a little at a time it will still be stable where I can drop some weight out of the nose. Now my original Saturn V had the engine recessed per instructions but I had to add larger fins and some weight into the nose to get that to fly stable. It weighs in at 1.1LB and does 250 feet on a Aerotech E30-4T which it's a nice flight
but I'm thinking it should be able to reach a higher altitude and I will just increase the engine size in the new one since the original Saturn V will only take a 24/70mm engine size. The new one is the 50th Anny edition.

 

[SecondRow]

When you build the new one, I suggest that you not make any modifications such as larger fins or extra weight in the nose cones (other than what you’re supplied in the kit). Follow the instructions and you will get very nice flights on 24mm Aerotech E motors.

Personally, I see no reason to fly this kit on an F or higher impulse. I want to watch the whole flight. i don’t enjoy seeing a Saturn zip off the pad and become a speck in the sky. 500-1000 feet is perfect for me. That’s what I get with an E30 and E20. Good luck on your build.

 

[smstachwick]

Thanks to both of you for your info it's very helpful. I was basically asking about the third stage.
With the trying to get cg the body diameter3.5 inches above CP as per the standard rule I'm at 9.91 OZ and this puts the rocket close to 1LB 8OZ which seems awful heavy to me. That's why I'm questioning the diameter size in difference of CG/CP. I'm thinking if I reduce the weight a little at a time it will still be stable where I can drop some weight out of the nose. Now my original Saturn V had the engine recessed per instructions but I had to add larger fins and some weight into the nose to get that to fly stable. It weighs in at 1.1LB and does 250 feet on a Aerotech E30-4T which it's a nice flight
but I'm thinking it should be able to reach a higher altitude and I will just increase the engine size in the new one since the original Saturn V will only take a 24/70mm engine size. The new one is the 50th Anny edition.

4 inches is typical for L1 high-power rockets or mid-power flying on something like a G. They commonly come with a 38mm or 54mm mount and only rarely come with a stock 29mm mount. Usually if they fly on that, it’s on a temporary adapter.

Trying to fly a 3.5” kit (albeit not constant-diameter) on a 24x70mm D seems to be pushing it.

24 oz does indeed seem on the heavy side for a kit of this size. I’d strongly recommend removing some weight and seeing if it still flies safely in that configuration.

 

[Sterk03]

Ok I do agree with the font need 1000 feet but up until I tried a E30-4T it never went high enough to get the chutes out and land safely because of underpowered. But at the same time unknown in the stability side. That’s where the added weight came in but now I’m going back to it was mostly underpowered not do much weight of stability. I enjoyed the E30 flight but thought I would be able to get a tad more altitude.

 

[Sterk03]

Not harping but I agree with the E30 but what E20 engine gets it high enough for chutes like I said mine is struggling to get to the mid 200’s. And yes too much was mentioned about CP that’s what made the new model so heavy so it’s light weight or bust I will find out.
Thanks

 

[smstachwick]

Well, let's have a look at the stats for those motors, shall we?

Aerotech 24mm single-use E motor comparison	Aerotech E20W	Aerotech E30T
Total Impulse	35 N-s (advertised as being part of the E range, 20.01 N-s to 40 N-s)	33.6 N-s (advertised as being part of the E range, 20.01 N-s to 40 N-s)
Average Thrust	21.8 N (advertised as 20N)	32.4 N-s (advertised as 30N)
Delay	4 s or 7 s	4 s or 7 s

Data from thrustcurve.org

The total impulse for these motors is very similar, less than a 2 N-s difference. So you'd probably get the rocket to a similar altitude at motor burnout and probably a similar airspeed too. But the E30 has higher average thrust, meaning that you could fly it safely with a shorter launch rod or with more windy conditions. In calm conditions, however, you could fly the E20 and get a slower, more impressive liftoff and a longer burn on the way up. The delays are identical.

Being a more conservative, safety conscious flyer myself, I'd probably go with the E30 for a first flight and only do an E20 in good conditions and upgraded launch equipment. That's just me, though.

 

[Sterk03]

Ok Secondrow I miss read your text I went back and read it again snd you were saying you were getting 509 to 1000 on. An E 20 and more with a 30?????? And that’s Estes 1/100 Saturn V interesting my original Saturn V around 16Oz o my mid 200’s and that’s in a Aerotech E30-4T I don’t have a clue how you could be getting those altitudes????
What’s the real secret???
Sterk03

 

[Sterk03]

With a 6 fr rod and a lesser engine then a E30 it just leans over and goes horizontal hence the E30 . I agree with the more realistic look of liftoff will smaller engine but I’m tired of repairs after they hit tera fins prior to chutes.

Sterk03

 

[SecondRow]

The 500-1000 number is a rough estimate because I’m terrible with judging altitude and I don’t use an altimeter for this rocket. it’s somewhere in between those values. But I know it’s going higher than 250 ft. The E20 probably gets higher than the E30.

I admit I haven’t been following this thread carefully, but I thought you said you got 200 ft on an E30 with your overbuilt (larger fins and extra nose weight) Saturn, not the stock build. Can you clarify? At what point did you decide to go with larger fins?

 

[Blast it Tom!]

My understanding is that the reason body tubes are left out of barrowman equations is because the surface of the body tube is parallel to the airflow, and so theoretically isn't bending/affecting it like your forward surfaces (nose/transitions) and fins are.

Wow, I missed that long ago reply, thanks! I WILL be looking into it further, makes sense...

 

[Sterk03]

The overbuild of the fins came after the first flight when the SatV went only 15 feet vertical and then downrange paralel to mother earth before entering the dirt prior to chute discharge. We are talking back in the (90's. The rocket had been in dormant stage for many years. So last year I tried my first launch with the new fins and it went maybe 25 feet and then leaned over and did the horizontal thing again, and tera firma. So the rocket club were thinking that it was underpowered yet I'm using what Estes said it would fly on....So this is where I first posted on the forum and the term CP and Cg which I was aware of but not the two together. So I did the cardboard model and the balance of the fully loaded rocket for CG and came up with the added weight in the nose which to me was too much. I finally got a E30-4T in it and it was the first successful flight but now I don't know if the engine alone would have been enough where maybe I can take some weight out of the nose and test again on using the correct motor or was it both stability and power????. Nest week I will be launching the new Sat V 1/100 50th anny version and I will have the original fins and I am going to take out the CP w added weight and just use what Estes put in the kit and see what happens. I might chicken out and keep the weight in the nose but the weight of (.9 OZ for stage 3 or the upper portion of the rocket seems very heavy to me but that is what the formula came up with. I will have an altimeter in the nose so I will get an exact altitude and we shall see.

Sterk03

 

[Sterk03]

Something is rotten in Denmark????? Ok Saturdays launch was canceled so its another month till maybe the Sat V goes airborne.
But something is not adding up. In the Bible of model rocketry it states to have a stable rocket the Cp is to be below the Cg (starting at the nose) by the distance of the diameter of the body tube?????? Ok so lets go by comments from Second row about building the stock rocket and using the clay they included to enter into the back of the nose cone capsule and nothing else. No Cp/CG was listed to test for so as someone stated then Estes must have the numbers set. Ok so I am launching the rocket as per Second Row and removed the excess weight and I am at 17.67 Oz main body and 5.22Oz on the third stage on up to the tower. So I think I am around the Second Row weight of his rocket, yet someone stated the average weight of a Sat V is 11 OZ to me this is not possible with it fully loaded. So my point is if it flies like I have it loaded then the Cp/CG in the Bible of Rocketry is not accurate or out dated or most of the times but there should not be just a large difference. TO get to the CP/CG split of the Bible I had my rocket at 1LB 8OZ and it was a reach to make the CG that far above the CP. Second Row has proven that it does not have to be very far apart at all to be stable or OR OR by using the larger then Estes recommends Rocket Motor it negates the CP/CG spread. Estes has never suggested anything above the D until 2 years ago and now it has the E and F but I doubt they are any more powerful then the E30-4T Aerotech Motor so is excess trust negating the lack of most stabile in the weight of the rocket? The only reason I questioned the calculation is because I reach such a high weight on getting the needed spread of CP?CG. So we shall see if my new Sat V flies right out of the box without doing anything extra from the instructions other then using a real Engine for launch. Rockets I have built from Boyce it does always mention a CG but nothing is said where the CP is located it just says make sure you have the weight that will balance at the CG and both of these rockets to me are way overweight and nose heavy, but that is all you have to go by unless you do a CP on your own and see where that falls but for some reason they must know if they are publishing a CG. The Rocksim info someone entered is for the 30th Anny and I'm not sure that is the same build as the 50th as the CP?CG numbers don't seem to align with the 50th build.

Ok just trying to put this subject to rest that how mush stable or over stable is needed for a rocket to fly stable???? The amount of weight that is being added to match the equation in the Bible are just not realistic.

Sterk03

 

[smstachwick]

Stine's Handbook is great but it's not end-all rulebook that must be obeyed at all times, nor is it presented as such. In fact, I'd be wary of flying with any RSO that insists that every single one of his recommendations must be followed at all times. While the relevant safety codes should be followed if you're flying at a NAR/Tripoli/international event or if you're launching near a populated area, some of Stine's home-grown design and flight recommendations can be fudged or ignored if the specific situation permits it with an acceptable degree of safety.

For example, he goes out of his way to mention that he opposes airstarts but many, many knowledgeable rocketeers here have the know-how to make it work. It's also necessary for staging composite motors.

He also warns against having more than three stages due to the added complexity, reliability challenges, and reduced efficiency, but again, many rocketeers enjoy the challenge and can get it to work (or fail) safely.

Others relish the challenge of creating experimental motors, which is another thing he practically disowns entirely, yet some do so without creating excessive hazards at research rocketry events like the ones hosted by FAR in the Mojave Desert. (Please don't try to make motors in your basement though, he is correct to oppose new rocketeers attempting to create motors without a safe open area and extensive education on how to handle potentially dangerous chemicals).

In a similar vein, sometimes you can get away with less than 1-caliber stability if you're flying in calm conditions, if you have good launch guidance, if you don't expect to get a lot of altitude, and if you send the rocket vertical.

I feel like Stine intended for his 1-caliber rule to apply mainly to high-performance sport models that can either become overstable and weathercock into a lawn dart or become negatively stable and chase you around. Considering that you're working with birds that are REALLY heavy and underpowered, either by design or through your own modifications in the pursuit of stability, I don't really think you need to worry a great deal about getting less than 1 caliber. I feel like 0.75 or 0.5 calibers should do the trick. It won't go very far or very fast. If you can get a successful flight profile at ANY altitude, even a really low one, I'd call that a win.

At that point you can either try to get that Saturn flyable on a different motor or just call it a day and look for a new challenge. I don't think there's much to be gained by spending a ton of effort trying to get a single model exactly to specification, especially when it can be challenging just to keep all these specifications on different kits from getting mixed up in your head.

With an entire world of rocketry available to explore, getting hung up on a single design, especially one that many would argue is underpowered, seems a bit silly from my point of view.