Why do I see different apogees for the Der Red Big Max in Apogee Components web site, Estes Web site, and Thrustcurve.org

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Underdog

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I enjoy slow dramatic launches of fat rockets. Apogee Components lists E-16W as an option for the 3" Der Red Big Max with an apogee of 787 ft. However, I see different apogees depending on where I look. Thrustcurve lists an apogee of 159 meters (521 feet) for the same E-16W motor.

I plan to build light (12 ounces). The other motors that I would like to try include Estes E12-4 (cheap black powder) and Aerotech's F12-3J Reload Kit 24/40. However, the different velocities off the rod and max altitude from these sources have me confused. (Apogee Components list the model weight at 9.7 ounces- Estes at 14 ounces, and Thurst Curve at 12 ounces). This Estes E-16 flight was 250 feet.

How can I do a better job of planning this slow launch/ cheap motor selection? Note: the launch rail is 8 ft.
 

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I believe the weight given on the Apogee webpage is in error.
Their Rocksim file gives the dry weight as just under 13 oz.
(Correction: I just noticed that 13 oz is the loaded weight with an E16W-4 motor. Dry weight listed at 9.3 oz., so I would view this file as suspect.)
I have the rocket built but unfinished. It's 10,8 oz.
After primer, paint and decals it will probably top 13 oz.
Anyway, ran three sims:
Estes E16-4: 741 ft. apogee
AT E16W-4: 830 ft. apogee
Estes F15-6: 1156 ft. apogee
Note that the last sim correlates with the Estes max altitude listed of 1100 ft.
The guy said in the video comment section that the rocket windcocked and he was estimating by eye so that could account for the variance. Also we don't know how heavy he built his Mustang version.
I would do the sims either with Rocksim or OR and pick my motors and have fun!
Laters.
2021-12-13.png
 
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OK, upon further inspection I found the mass of the nose cone in the Rocksim file is wrong. It says 75.46 g. I weighed mine and it's actually 134.4 g. with the supplied nose weight. Will mod the file and rerun the sims. Stay tuned.
 
Modded the file, new dry weight is 11.4 oz.
Haven't had the chance to scrutinize each component but ran new sims:
Estes E16-4: 629 ft apogee
AT E16W-4: 704 ft apogee
Estes F15-6: 1012 ft. apogee
I would get an actual finished weight and plug it into the file then run my sims.
2021-12-13 (1).png
 
I enjoy slow dramatic launches of fat rockets. Apogee Components lists E-16W as an option for the 3" Der Red Big Max with an apogee of 787 ft. However, I see different apogees depending on where I look. Thrustcurve lists an apogee of 159 meters (521 feet) for the same E-16W motor.

I plan to build light (12 ounces). The other motors that I would like to try include Estes E12-4 (cheap black powder) and Aerotech's F12-3J Reload Kit 24/40. However, the different velocities off the rod and max altitude from these sources have me confused. (Apogee Components list the model weight at 9.7 ounces- Estes at 14 ounces, and Thurst Curve at 12 ounces). This Estes E-16 flight was 250 feet.

How can I do a better job of planning this slow launch/ cheap motor selection? Note: the launch rail is 8 ft.
Given the disparity, just build it, weigh it, and pick the simulation that uses that weight or create your own simulation.
 
What he says!
You need to remember some people build light, some heavy, some modify what's there to fit their own tastes (I tend to throw away the supplied shock cord and that paper attachment and run thin kevlar that i tie and glue on the motor tube). Like Steve said, build it, weigh it and sim it (if you need) and fly it. I don't sim low power just look at thrust to weight as my low power doesn't include altimeters. For me, half the fun is the simplicity of low power. I can always over-science the high power and EX stuff......
But I also know others that roll carbon body tubes, make carbon fins and perfectly duplicate Estes stuff. That's their fun, and I'm glad they find it there.
In hiking, we say hike your own hike (cause it's not wrong if you like to take bypasses or road walk)
maybe rocketry should be fly your own flight....
 
Modded the file, new dry weight is 11.4 oz.
Haven't had the chance to scrutinize each component but ran new sims:
Estes E16-4: 629 ft apogee
AT E16W-4: 704 ft apogee
Estes F15-6: 1012 ft. apogee
I would get an actual finished weight and plug it into the file then run my sims.

Any chance you could run Rocket Sim with the Estes E12-4 (cheap black powder) and Aerotech's F12-3J Reload Kit 24/40?
I was building Der Red Big Max with those specific motors in mind. I have collection of E12-4 motors and I was hoping Der Big Red Max would have a good velocity at 6 or 7 feet up the launch rod.
 
How can I do a better job of planning this slow launch/ cheap motor selection? Note: the launch rail is 8 ft.
Any chance you could run Rocket Sim with the Estes E12-4 (cheap black powder) and Aerotech's F12-3J Reload Kit 24/40?
Speed off an 8 ft. rail for both is 34 mph.
E12-4 tops off at 480 ft.
F12J-5 at 937 ft.
F12 motor only has a 2 or 5 second delay in the database, but 5 seconds is the optimal delay anyway.
But, like I said before, get your finished weight then mod the file and run the sims.
It will likely be different than the file weight, so your sims will be different as well.
I strongly suggest you download Open Rocket and run your own sims.
It's free and it can run Rocksim (.rkt) files also.
 
Any chance you could run Rocket Sim with the Estes E12-4 (cheap black powder) and Aerotech's F12-3J Reload Kit 24/40?
I was building Der Red Big Max with those specific motors in mind. I have collection of E12-4 motors and I was hoping Der Big Red Max would have a good velocity at 6 or 7 feet up the launch rod.
You can run your own sims online at Thrustcurve:

https://www.thrustcurve.org/motors/guide.html
Create an account before you start so you can save your rockets. Once you have an account, you can also set site preferences to the units you prefer. Then choose the 'My Rockets' link to add the data for your rocket and save it. Or you can choose a one-time entry for a quick result. Then you can set up your motor criteria and run a sim. It will only show motors that 'work' with your rocket, in terms of speed off the rail. Below are the results for a 3" rocket that weighs 11.4 oz. A great way to find motors that will work, even if it's not as accurate as a program like OpenRocket or Rocksim.


Tony

I set the speed off the rail to only 35 ft/sec to show more motors, left the CD at the default of .6, which tends to be low for most rockets (note that is shows the T:W is only 3:1 for an E12):
motor-table.png

Here's the detailed results you get when you click on the red circled i at the end of the column:

motor-details.png
 
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Speed off an 8 ft. rail for both is 34 mph.
E12-4 tops off at 480 ft.
F12J-5 at 937 ft.
F12 motor only has a 2 or 5 second delay in the database, but 5 seconds is the optimal delay anyway.
But, like I said before, get your finished weight then mod the file and run the sims.
It will likely be different than the file weight, so your sims will be different as well.
I strongly suggest you download Open Rocket and run your own sims.
It's free and it can run Rocksim (.rkt) files also.
This is very encouraging, both for myself and for Der Red Big Max.
 
You can run your own sims online at Thrustcurve:

https://www.thrustcurve.org/motors/guide.html
Create an account before you start so you can save your rockets. Once you have an account, you can also set site preferences to the units you prefer. Then choose the 'My Rockets' link to add the data for your rocket and save it. Or you can choose a one-time entry for a quick result. Then you can set up your motor criteria and run a sim. It will only show motors that 'work' with your rocket, in terms of speed off the rail. Below are the results for a 3" rocket that weighs 11.4 oz. A great way to find motors that will work, even if it's not as accurate as a program like OpenRocket or Rocksim.


Tony

I set the speed off the rail to only 35 ft/sec to show more motors, left the CD at the default of .6, which tends to be low for most rockets (note that is shows the T:W is only 3:1 for an E12):
View attachment 494229

Here's the detailed results you get when you click on the red circled i at the end of the column:

View attachment 494230
I did try Thrustcurve, I just thought that the calculations were very different from the info I was seeing elsewhere. https://www.thrustcurve.org/motors/guide/61b6a05f44e6d40004189eb2/complete.html
 
FWIW, my Der Big Red Max build came in at 12.2oz, built almost stock (Only mod was a 9' kevlar shock cord attached to the MMT). I haven't launched it yet, but the minimum motor I'd want to would be the Estes E16-4. While the E12-4 has roughly the same speed off the rod (40fps on a 60" rod), the altitude is only ~320', with a coast time of only 3s. If there's any weather-cocking, it could eject quite low. With the E16-4, speed off rod is close, but altitude is 430' and coast time is about 4s, so a safer flight. Perfect delay if it goes straight up, but more margin if it doesn't.

For first flight, I'll want more safety margin, so will likely go with an F27-4 EconoJet, about 45 fps, and 750' altitude, 4.3s coast time. Hmm, I have an F63 reload too, same altitude, 70fps!
 
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At what altitude will the chute open on the E12-4? Wouldn’t 320 feet be high enough?
 
At what altitude will the chute open on the E12-4? Wouldn’t 320 feet be high enough?
Even if the flight is perfectly straight up (which they often are not), since the coast time is 3s, and the delay time is 4s the rocket will be headed down when ejection occurs. The altitude it opens depends on how much off vertical it flies, and how long it takes for the chute to open after ejection. The ejection charge of an E12 is almost certainly less than that of the E16, so it may eject slower, especially with the 3" BT it needs to pressurize. So if this sim is accurate, it might be OK, if flown on a 6' rail, if there's no wind, and if the ejection charge is sufficient to push the chute out. That's 4 "if's", only one of which can be eliminated with certainty.

A thin-mil chute would be recommended, it may open faster than the stiff plastic Red Max chute. My first flight is today, I'm interested to see the how the chute performs at 30F.
 
The maiden flight on an F27-4 was nearly perfect, *plenty* of thrust off the rod. The chute opened great, even in 25F air, though it was quite stiff. Should've put in an altimeter, sim said 753, my calbrated eyeball said 800-900 feet. Now I'm game to try lower thrust motors.
 
The maiden flight on an F27-4 was nearly perfect, *plenty* of thrust off the rod. The chute opened great, even in 25F air, though it was quite stiff. Should've put in an altimeter, sim said 753, my calbrated eyeball said 800-900 feet. Now I'm game to try lower thrust motors.
We will look forward to hearing more about the lower thrust motors.
 
We will look forward to hearing more about the lower thrust motors.
Flew the 3" Der Big Red Max today on an E16-4, from a 5' rod, in light winds. It was a nice straight liftoff, until about 100' in the air when the propellant let go and sent up a roman candle. It landed in the snow, with no structural damage, just a bit of charring on the chute - probably a good thing it had a kevlar cord & nomex chute protector. Eyeballing, it seemed to have sufficient speed off the rod, but I wouldn't go any lower thrust. I'll be getting a new pack of E16's for the next flight, the remaining motors from 04-15-13 (2 packs) will be relegated to saucers.
 
I enjoy slow dramatic launches of fat rockets. Apogee Components lists E-16W as an option for the 3" Der Red Big Max with an apogee of 787 ft. However, I see different apogees depending on where I look. Thrustcurve lists an apogee of 159 meters (521 feet) for the same E-16W motor.

I plan to build light (12 ounces). The other motors that I would like to try include Estes E12-4 (cheap black powder) and Aerotech's F12-3J Reload Kit 24/40. However, the different velocities off the rod and max altitude from these sources have me confused. (Apogee Components list the model weight at 9.7 ounces- Estes at 14 ounces, and Thurst Curve at 12 ounces). This Estes E-16 flight was 250 feet.

How can I do a better job of planning this slow launch/ cheap motor selection? Note: the launch rail is 8 ft.
I have found thrustcurve to be accurate when it comes to delay times, speed off rail/rod, and altitude.
 
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