Good morning all you BARs. I'm doing some pre launch research to see if I can launch my SLS Aerodart safely on F22J motors. This is the problem I'm having. I have been told that a safe stable launch requires a minimum Thrust to Weight ratio of 5:1. The ThrustCurve website which is very helpful matching motors to rockets tells me that although this motor will provide a T:W of 6:1, the lift off acceleration will be too slow meaning the rocket will be unstable. Thrust Curve puts this motor in the fail category for this rocket. Interestingly, I used ThrustCurve to find motors for the Aerodart in 2014 and then the F22J was in the "Motors that worked" category. I wonder why the result changed since 2014. Incidentally, the Aerodart will be launched on a 48" rod. Has anyone launched an SLS Aerodart on F22J successfully?

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SLS Aerodart Motor guide ThrustCurve.pdf (170.8 KB, 44 views)

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Douglas

I wouldn't do it.
The thrust profile of that motor sucks for anything but really light rockets.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.

Somebody call a doctor. GH must be really sick! Come on, man! You love power prangs!

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I love sanding.

I don't like Powr-Prangs with any Mini-Max or Enerjet kits. That's just heathen blasphemy.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.

I was only into LPR in the early 70s, so I didn't know anything about AP motors and the original Enerjet line, but C propellant looks good. My fav is White lightening, of course. SLS Aerodart launches great on F20W, but that's a SU motor. RMS is much more cost effective. E18W also works well for this rocket. Black Jack propellant is the reason for the slow launch issue here. Right now I don't have a mid power rocket in my fleet that I'm comfortable launching on F22J.

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Douglas

I don't purchase BJ propellant anything for my 18, 24, 29 hobby, and 29 HPR RMS casings.
Not a fan of slow low thrust liftoffs. I prefer BLAST-Offs. FJ propellant is acceptable, but leaves a lot of residue.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.

Not always !

F20W $34.19 ( 2 pk. ) at Balsa Machining Service ( $17.09 per motor )

RMS-29/40-120 Motor hardware ( BMS ) $67.49

29mm F reloads ( BMS ) $17.99 each


Cost for 10 flights

F20W - $170.90

RMS - $247.329

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Cost for 100 flights

F20W - $1709.00

RMS - $1866.49

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Dave F.

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"Failure Is Not An Option . . . Adapt & Overcome ! "

NAR # 26128 L2
TRIPOLI # 517 L2 ( inactive, at present )

That is like comparing apples to oranges, because the F20 is a hazmat free 30g motor with only 52 Ns total impulse vs. the RMS Fs that are close to 80 Ns but require Hazmat.

I've flown an Aerodart clone on a wide variety of RMS motors. F40, F80, I think F52.

I woudl definitely avoid the F22J. I have used that in a slightly smaller early model Aerodat (1.5" ID tube) and it flew nicely.

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NAR #27085 - Oregon Rocketry - SAM