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  #21  
Old 10-30-2011, 02:45 PM
mwtoelle's Avatar
mwtoelle mwtoelle is offline
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Quote:
Originally Posted by CPMcGraw
(snip)
Haven't simulated a Cherokee-D yet, but I expect better lift-off numbers. This engine should not be viewed as a serious BOOST engine for heavier designs; rather as a higher-performance "D" for light designs (3FNC and 4FNC variety).

Early or late production on the Cherokee-D? A late production semi-clone that I built back in 1994 drifted out of sight after a successful flight on an Estes E15-8. However, an Estes E motor of any description will require some nose weight. I am surprised that you did not simulate the old Estes Omega with an E12-0/E12-8 combo. If you really want to fly heavy models on black powder motors, I think that you would need a core or semi-core burning motor.
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  #22  
Old 10-30-2011, 05:53 PM
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Jerry Irvine Jerry Irvine is offline
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Quote:
Originally Posted by CPMcGraw
Using the new graph, as Jerry indicated, the engine is "soft". It appears great, once the model is airborne, but getting off the ground it doesn't have a lot of "oomph" when used in a design that weighs in over 13 oz loaded.

I also tried it out in the SEMROC SLS Laser-X...

Altitude -- 554'
Deployment V -- 4 FPS
Rod length -- 60" (took 49")

This is a 12.5 oz design loaded, and shows great flight numbers, but lousy take-off numbers.
I have strongly suggested Estes upgrade to 1/4" x 48" rods (USR standard) and forsake 3/16" going forward. The AT by E motors need a stiffer rod and the Estes E motors need a longer rod due to low take-off speeds. These E motors should be considered to have a max liftoff weight of a pound or less, and better if between 1/2 and 3/4 pound. I would say the MLOW of a D12 is 30-50% higher than an E12.

Counter-intuitive but true.

Jerry
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  #23  
Old 10-30-2011, 08:14 PM
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CPMcGraw CPMcGraw is offline
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First simulations with a Cherokee DD...

Simulation 1: E12-0/E12-8......2709'......Dv 16 FPS......60" x 1/4" (45" required)

Simulation 2: D12-0/E12-8......2225'......Dv 8 FPS.......60" x 1/4" (47" required)

Simulation 3: E12-0/D12-7......2126'......Dv 31 FPS......60" x 1/4" (43" required)

I figured a lighter design would work better, and these first runs tend to confirm it. It was a pleasant surprise to see a D12-0 doing as well as it did as the booster, and to see a 500' difference in altitude between it and the E12-0. One item to note with these simulations, all three include a 3 oz allowance for a BoosterVision camera and 9V battery.
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  #24  
Old 10-30-2011, 09:17 PM
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Using a standard Cherokee, I ran simulations with both 18" and 16.4" tubes:

Short-body: E12-6, 2018', Dv 29 FPS, requires 0.375 oz of ballast at base of NC, has a margin of 1.43. 28" of rod.

Long-body: E12-6, 1987', Dv 25 FPS, requires 0.25 oz of ballast at base of NC, has a margin of 1.45. 29" of rod.

The E12 requires ballast on both versions. The margin was below 1.0 for both without it.
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  #25  
Old 10-30-2011, 11:10 PM
CaninoBD CaninoBD is offline
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Quote:
Originally Posted by Green Dragon
You need no Level anything cert to cluster E motors.

Level 1 cert in only required for flying H-I motors. ( or up to cluster of 1280 N-sec ).

three 30Nsec E's is 90 Nsec and no certification is required..

unsure on the waiver issues, however, is the new no-notification 'large model rocket' propellant weight limit 125 grams or 113 ?

~ AL

fly em high


Not entirely correct.

Your forgetting the NAR safety code rule 7 Size. My model rocket will not weigh more than 1,500 grams (53 ounces) at liftoff and will not contain more than 125 grams (4.4 ounces) of propellant or 320 N-sec (71.9 pound-seconds) of total impulse.

3 E9 are 35.8 * 3 = 107.4 grams OK
4 E9 are 35.8 * 4 = 143.2 grams NOT OK - HP and you need a L1
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  #26  
Old 10-31-2011, 12:13 AM
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luke strawwalker luke strawwalker is offline
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Quote:
Originally Posted by Doug Sams
Yes, indeed, this is great news! WFK!

I just compared it to the E9. Same length case. E12 has 2.5s burn time vs 3s for E9. Both have sustainer portion of curve at ~10N. Both are ~36g of propellant (ie, no mailing).

The key diff is that the E12 has a 33N initial thrust spike vs 20N for the E9. So the E12 is very much like a longer burning D12 with a similar initial kick.

I'm really looking forward to getting my hands on some of these! This is really exciting news.

Doug


I don't quite follow this...

The D12 burn duration is 2.7 seconds, is it not?? The E9 is 3 seconds, correct?? So the E12 is now 2.5 seconds, with the same peak thrust as a D12?? How is this a higher performing motor (IOW an "E" motor) if it has the same DURATION as a D12 and the same peak and average thrust as D12?? I get it that it's a LOW END "E" motor, so it's not going to be double the duration of a D12 at the D12's average and peak thrust levels to be a "full E", or that it has DOUBLE the peak and average thrust for the same duration as a D12, (or some combination thereof) but I don't follow how this is an "E" motor if it has the same burn characteristics as a D12... and the D12 at 17N/s isn't a FULL "D" motor either...

I must be missing something... Last I heard though, thrust times duration = total impulse (motor letter class) later! OL JR
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  #27  
Old 10-31-2011, 12:36 AM
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Royatl Royatl is offline
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Quote:
Originally Posted by luke strawwalker
I don't quite follow this...

The D12 burn duration is 2.7 seconds, is it not??

....snip....

I must be missing something... Last I heard though, thrust times duration = total impulse (motor letter class) later! OL JR


Yep, you're missing something. The D12 is 1.6 seconds. The E12 burns 50% longer.
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  #28  
Old 10-31-2011, 06:27 AM
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GregGleason GregGleason is offline
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The thrust curve is similar to the D12, except it burns for another second.

Remove the ".txt" from the file "Estes.E12.eng.txt" and you will have a working .eng file.

Greg

Quote:
; NAR Date Tested ...: 2011-09-25
; Total Impulse .....: 27.24 n-s (s 0.35)
; Peak Thrust .......: 33.29 n (s 3.49)
; Burn Time .........: 27.24 n-s (s 0.35)
; Average Thrust ....: 11.17 n
; Exported using ThrustCurveTool, www.ThrustGear.com
; Exported by .......: Greg Gleason
; Export Date .......: 2011-10-30

E12 24 95 0-4-6-8 0.0359 0.0588 ES
0.017 2.222
0.064 6.519
0.103 11.556
0.163 19.704
0.202 25.481
0.245 31.259
0.284 32.889
0.296 30.667
0.309 27.407
0.331 20.889
0.352 15.407
0.387 13.333
0.464 11.852
0.657 10.667
0.842 10.37
0.889 9.778
1.125 10.074
1.297 9.481
1.323 10.37
1.336 9.481
1.74 9.333
2.04 9.185
2.143 9.185
2.174 10.222
2.199 9.481
2.332 9.63
2.371 9.926
2.397 6.222
2.431 2.222
2.44 0.0
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  #29  
Old 10-31-2011, 07:03 AM
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STRMan STRMan is offline
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Quote:
Originally Posted by Gus

So E12-0 to E9-8 ought to make for some interesting flights.


My first thought! I actually have an upscale Centuri Stiletto that I made to launch from a D12-0 to an E9-8. Rocksim put it up at around 2900 feet. I have to make another booster now to hold the E12-0 booster. Looks like I will finally have my first rocket capable of breaking 3000 feet!

It will be interesting to see if the sustainer will gain more altitude with an E9-8 or an E12-8.
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  #30  
Old 10-31-2011, 09:33 AM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by Gus
So E12-0 to E9-8 ought to make for some interesting flights.
I have a rocket that's perfect for this. I used a Big Betty to build a sort of upscale ApogeeII, and, the way I set it up, the booster can handle the longer motor, so I should be able to test this combo...without putting it in orbit

BTW, I wasn't clairvoyant - I didn't anticipate the advent of a longer booster motor. I only made the booster longer, as I recall, to keep it closer to scale. But it oughta work perfectly with the E12-0.

Doug

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