New old guy with a question

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BuckeyeGuy

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Hiya folks - like many I've read about here, I used to launch lots of rockets back "in the day" and now my kids are getting interested. I'm enjoying rediscovering how much fun this is. We're sticking with Estes kits currently, and I just finished building the STM-012. My question: Estes lists an E9 as the biggest engine that should be used. I've plugged the specs into OR, and if I use something with a bit more power-like an F24-7 from AeroTech-I should get an additional 150m of altitude. My concern is ripping the fins off the poor thing. What say you? Mods, if this needs moving please feel free.

Latest launch: [video=youtube;S8654jg_VGM]https://www.youtube.com/watch?v=S8654jg_VGM[/video]
 

TopRamen

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It has a lot to do with what construction methods and techniques you employ.
Estes "Recommendations" are merely that, recommendations, and they are based on the assumption that you will use "Back in the day" building techniques and adhesives.
Basically, if you employed things like glassing, epoxy, and ample nose weight to bring the CG where it needs to be for stability, you could push the model past Mach one with the right size motor, but it would not really be an "Estes Kit" anymore.
An E9 is not a very good motor for anything in my opinion, and you should simply disregard that bit of "Estes Wisdom".

It all depends on how you build it.
 

DavidMcCann

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F24 may take the fins off, but an E15 or E18 reload should do nicely.

The E9 is barely able to lift itself. Bleh.
 

BuckeyeGuy

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I'll obviously have to update my construction techniques lol! I'll run the E15/E18 through OR, see where it puts me. Thanks!
 

fyrwrxz

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I'll obviously have to update my construction techniques lol! I'll run the E15/E18 through OR, see where it puts me. Thanks!
Search about fin fillets and papering your fins. Also about thin CA reinforcement of the body tube. These should help it survive a lot longer. Straight smoke and good chutes!
 

Zeus-cat

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F24 may take the fins off, but an E15 or E18 reload should do nicely.

The E9 is barely able to lift itself. Bleh.
An E9 in the right rocket can go very high. I've had a rocket go to almost 1,600 feet on an E9-6. That is a bit more than barely lifting itself. The problem is that some people think that since it is an E it can lift more than a D. If you understand motor designations you know that it has less average thrust than a D12, but it is a great motor in the right rocket.
 

DavidMcCann

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An E9 in the right rocket can go very high. I've had a rocket go to almost 1,600 feet on an E9-6. That is a bit more than barely lifting itself. The problem is that some people think that since it is an E it can lift more than a D. If you understand motor designations you know that it has less average thrust than a D12, but it is a great motor in the right rocket.

True. However Estes seems to be in the class that believes the motor is more able than it is. They are a bit liberal with it's recommendation. I've got a pack left here I'll likely use at some point, but I'm just not a fan.
 

cbrarick

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If you glued them on with carpenter's glue, then the joint is stronger then the body tube. Fly it! If it likes it, fly it again, otherwise it's a learning experience on how well your current technique is. You don't need to reinforce the joint with all the stuff mentioned above - all that does is add weight and slow you down! Of course, it also messes up your cp/cg relationship.
 

BuckeyeGuy

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Thanks guys - I think I'll take it out and have a first flight/test flight with a D, just for the shakedown. OR says it should get to around 200m-ish.
 

adrian

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How much does an E9 weigh, and how much does an F24 weigh? If the F24 is heavier then you're moving the CG back, which could cause the rocket to become unstable. Check where OR puts the CP, then find the CG of the model with an F24-7 in place and make sure the CG is still sufficiently far ahead of the CP. Don't take OR's estimate of the CG, balance the rocket and find out where it really is. Construction technique (especially if strong enough for the rocket to survive flight on an F24) and paint could change the CG from where OR estimates it to be.
 

tmacklin

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An Estes E12 would be a good alternate to the E9 and has a peak thrust that is 50% higher than the E9 but about 0.6 seconds less thrust duration. Better have a BIG field on that Aerotech F24W!
 

BuckeyeGuy

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Great stuff! Now if I can just get a day of low wind speed!


Sent from my iPad using Tapatalk
 

75Grandville

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Just an opinion (and we all know what those are worth!). With TTW fin construction, I would probably be willing to try flying this on an F, if it were my rocket. Assuming that I had had successful D and E flights first.

Thinwall cardboard, plastic, and balsa models are capable of breaking mach, if properly constructed. I'm thinking of the Apogee Aspire, which is a minimum diameter with a 0.018" wall thickness, that will fly on a G80 (they strongly suggest papering the fins and adding good fillets).


Aerotech makes an F12 reload. Average thrust the same as the D and E, you should get a lot higher. F24 - I'd fly it. Bigger than that, I'd want to see how it did on "smaller" F motors.

F240 - probably not! Insane amounts of fun with a fiberglass kit - 0 to 1300' in about 0.5 seconds.


Just some other random thoughts:

  • I use my car battery when launching composite motors, even D's - the ignitors require a bit more oomph to fire
  • You may want to use a streamer or 12" chute if you are going that high
 
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BuckeyeGuy

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Obviously a lot to learn - is there a primer for understanding total impulse and average thrust as it pertains to performance?
 

samb

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Obviously a lot to learn - is there a primer for understanding total impulse and average thrust as it pertains to performance?
One place where I found extremely helpful information when I returned to the hobby in '06 was info-central. Sadly now an orphaned site, it can still be accessed through the magic of the Wayback Machine.

https://web.archive.org/web/20120519163039/https://www.info-central.org/?article=230

Another great resource are the outstanding series of how-to videos created by Jon Coker. Here is his 'Choosing Motors' offering: https://www.jcrocket.com/choosing-motors.shtml

Tim Van Milligan's Apogee Rockets is a great vendor and source of many educational videos and the Peak of Flight newsletter: https://apogeerockets.com/education/downloads/Newsletter132.pdf

Hope this helps.
 

BuckeyeGuy

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One place where I found extremely helpful information when I returned to the hobby in '06 was info-central. Sadly now an orphaned site, it can still be accessed through the magic of the Wayback Machine.

https://web.archive.org/web/20120519163039/https://www.info-central.org/?article=230

Another great resource are the outstanding series of how-to videos created by Jon Coker. Here is his 'Choosing Motors' offering: https://www.jcrocket.com/choosing-motors.shtml

Tim Van Milligan's Apogee Rockets is a great vendor and source of many educational videos and the Peak of Flight newsletter: https://apogeerockets.com/education/downloads/Newsletter132.pdf

Hope this helps.

That Info Central site is exactly what I was looking for, thanks (and thanks for the Wayback Machine)! I discovered Mr Coker a couple of days ago, subscribed immediately, and I've been watching the Apogee vids, very cool stuff.
 

c0c0m0ke

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Aren't E and F motors different sizes? Actually, doesn't the F come in two sizes? One is the same size as the E, but there are longer and fatter Fs. I have never flown or purchased an F, but I recall seeing a display in a hobby shop and some of the F motors looked thicker and about an inch longer than the E motors. Depending on the F motor a different engine mount would be required.
 

Steve Shannon

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Put a thrust ring on the aft end of the motor if it's not there already and leave out the engine block and spring clip when you build the motor mount and it will take different length motors.
 

samb

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Aren't E and F motors different sizes? Actually, doesn't the F come in two sizes? One is the same size as the E, but there are longer and fatter Fs. I have never flown or purchased an F, but I recall seeing a display in a hobby shop and some of the F motors looked thicker and about an inch longer than the E motors. Depending on the F motor a different engine mount would be required.
Well in the Estes black powder motor world you have E motors in 24mm diameter (E9, E12) and 29mm diameter (E16) sizes. The F15 comes in the 29mm flavor only.

Estes_motor_sizes.jpg

In the ammonium perchlorate composite propellant (APCP) world, Aerotech offers E and F impulse in both 24mm and 29mm sizes and in single use or reloadable flavors. Choices !

AT single use.jpg AT reload.jpg

As Steve mentioned, leaving out the internal, motor tube attached thrust ring allows maximum flexibility to choose motors of differing length for a given diameter.
 
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