3" MAC Scorpion-

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BSNW

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Hey all-
Okay I know this is kind of a lame question. There is a reason why I am asking the rocketry community this question. ANYWAY..

If you have a dual deploy 3" MAC Performance Scorpion and have done some flights on it with 38mm motors...can you let me know what motors and what altitudes you got? Its that simple.

I am thinking of trying an I200-W (YES I said I200....I love that motor. Based on dry weights and adding a pinch for glue and paint I get a thrust to weight of around 6:1 for the life of the burn of the motor...not bad) for lower flights and the I284-W for higher flights (which may be a tad out of site....to much for me since that motor is almost a J motor). All I need is some rough ideas on motors and altitudes for this rocket....so I can get a general feel. Kind of like asking folks at the launch line "Say...what motors have you used in that rocket".....thing. Since I dont know anyone with this rocket...I go to the forums...

Back Story: So, I dont have Roc-Sim...Open Roc makes my computer crash, and I did go to Thrust Curve.org at one time....See, I have a 4" Scorpion that I entered all the actual weights and measures on the ThrustCurve guide. I entered my motor...a J540-R. It said a max altitude of around 4100 feet. When I launched it....it went 5289 feet (sweet). Just a little off though!! So now you know the boring back story to my original question. And since Thrust Curve says "Simulator Data" on the thrust curves I am looking for more real world, observed information on this rocket.

Thank you for your time and Help!
Andrew
 
I have no experience with this rocket but I opened the ORK in Open Rocket and configured it with an AT I200W:
Scorpion.jpg
 
Hey all-
Okay I know this is kind of a lame question. There is a reason why I am asking the rocketry community this question. ANYWAY..

If you have a dual deploy 3" MAC Performance Scorpion and have done some flights on it with 38mm motors...can you let me know what motors and what altitudes you got? Its that simple.

I am thinking of trying an I200-W (YES I said I200....I love that motor. Based on dry weights and adding a pinch for glue and paint I get a thrust to weight of around 6:1 for the life of the burn of the motor...not bad) for lower flights and the I284-W for higher flights (which may be a tad out of site....to much for me since that motor is almost a J motor). All I need is some rough ideas on motors and altitudes for this rocket....so I can get a general feel. Kind of like asking folks at the launch line "Say...what motors have you used in that rocket".....thing. Since I dont know anyone with this rocket...I go to the forums...

Back Story: So, I dont have Roc-Sim...Open Roc makes my computer crash, and I did go to Thrust Curve.org at one time....See, I have a 4" Scorpion that I entered all the actual weights and measures on the ThrustCurve guide. I entered my motor...a J540-R. It said a max altitude of around 4100 feet. When I launched it....it went 5289 feet (sweet). Just a little off though!! So now you know the boring back story to my original question. And since Thrust Curve says "Simulator Data" on the thrust curves I am looking for more real world, observed information on this rocket.

Thank you for your time and Help!
Andrew

Nothing on 38mm, but turned in over 19K on a Loki L1400. Just sayin......
 
Gary I knew you would reply to this! I also heard you needed some parts after that flight! Ha ha ha!!! Just Saying!!
I know....I'm one of tho guys....one who actually likes to SEE my rockets after they leave the pad!!l
 
. All I need is some rough ideas on motors and altitudes for this rocket....so I can get a general feel.

This exactly what Thrustcurve is for - a general feel, not absolute precision. Thrustcurve is very clear about its assumptions and recommends other simulators if you need more detailed analysis.

As for your particular observation on the J540, the Thustcurve default constant Cd of 0.6 is probably a bit too high (and it is not constant, either.) Using a better Cd model (OR), this rocket spends most of its time below 0.6. Or, you got a hot sample of J540. Or, you launched in Colorado. Or, the altimeter has temperature error. There are many unmentioned possible discrepancies between your simulation and your flight.

Spending more time with good simulations of YOUR rocket will be more helpful than anecdotal comments about rockets that are not yours.
 
This exactly what Thrustcurve is for - a general feel, not absolute precision. Thrustcurve is very clear about its assumptions and recommends other simulators if you need more detailed analysis.

As for your particular observation on the J540, the Thustcurve default constant Cd of 0.6 is probably a bit too high (and it is not constant, either.) Using a better Cd model (OR), this rocket spends most of its time below 0.6. Or, you got a hot sample of J540. Or, you launched in Colorado. Or, the altimeter has temperature error. There are many unmentioned possible discrepancies between your simulation and your flight.

Spending more time with good simulations of YOUR rocket will be more helpful than anecdotal comments about rockets that are not yours.

Yes I know this....I just gave the back story to my question. Also I did find it kind of funny that the estimation was that far off. Geez is it okay if I ask for anectdotal information? Or does this offend the the super smart rocket guys?

I don't NEED or WANT to spend time on an expensive simulation program for a stable rocket of simple design to sim my rocket. What I need are accurate weights and an accurate thrust curve and I am good to go. Call my original post friendly-general "flight line conversation". I see your very knowledgeable on sport rocketry... would this have been your reply if I walked up to you and asked this question on the flight line?

Nevermind.....
 
I will share some "anectdotal observations" from my rocketry travels. I have found when you want to ask questions at a launch, I go to the old school guys with lots of EXPERIENCE. They have made all the mistakes and are willing to share their experiences.

People often equate knowledge with wisdom. Some of the slickest-smartest Roc-Sim guys can't launch their way out of a paper bag.....I have seen this. Because to some....Roc-Sim makes them think that if they have all the information....it replaces their lack of experience in the real world. Model Rocketry from models all the way up to the biggest of the big did just fine before Roc-Sim and the people who built and launched gained knowledge AND wisdom just fine without it. Yes.... I was asking for anectdotal observations from others......I will take that over Roc-Sim any day.
Andrew
 
I've flown my 3" Scorpion on an AT H550 1,854 feet and a CTI I800 vmax to 2,617 feet. The rocket weighs 4.5 las without motor and I have an Aero Pack tailcone retainer on it.
 
I have one and fly it often, but mine has an extended booster with a 54mm MMT. I adapt down and fly it on I impulse frequently, but I don't keep flight records. The last two flights have been on a Pro54 J240-RL and have gone to 5500', if that in any way helps (probably not).
 
THANK YOU Dave-Brian and John! This is exactly what I was looking for...just some general information. I think I will stick with the I284-W. The "simulated" thrust curve shows a great thrust to weight to cover low and higher winds. Should be a fun ride! this is a nice kit...I too have the tail-cone on this and my larger 4" scorpion (see Mac Performance web site). Anyway....THANKS GUYS!!!
As Gary Dickinson would say, "see you on the flight line" lets hope for Blue Skies and No Wind!..BSNW
Andrew
 
Hi Andrew,
Something to consider for simulations in the future. I use an app called ‘Rocket Calculator’. I think I paid $4.99 a few years ago. I have it on my iPad and iPhone. It has multiple features (altimeter port sizing, chute decent calculations, deployment charge calculators, etc) along with altitude prediction. You can adjust for launch site altitude (I’m in Colorado), temperature, Cd, etc. I would call it an intermediate step between Thrust Curve and OR/RockSim. However, I just did a search in the App Store and can’t seem to find it, so my suggestion may be moot. If you can find it, it’s worth a few bucks IMO.
 
I don't NEED or WANT to spend time on an expensive simulation program for a stable rocket of simple design to sim my rocket. What I need are accurate weights and an accurate thrust curve and I am good to go. Call my original post friendly-general "flight line conversation". I see your very knowledgeable on sport rocketry... would this have been your reply if I walked up to you and asked this question on the flight line?

Thrustcurve, OpenRocket, and RASAero are free of cost.

If you asked me on the flight line, I'd say, "Nice rocket, BSNW. However, I am not familiar with your model and building techniques. Also, there are about 50 different 38mm motors that you can buy, and I haven't memorized every one of them. Rather than guess, let's use some science. Here is a simple app on my phone called Thrustcurve Motor Guide. In about 15 seconds, it will compare the performance of every motor that fits your rocket......."

Teach a man to fish, and all that jazz.

You asked about 38mm motors and modest altitudes, and ended up getting responses about 54mm motors going to 19,000 ft. I find those comments less useful than a relevant simulation, even one that may differ by 20% from an observation. Past data allows you to tune and better predict the next flight.
 
As you can see by my reply to Gary.....he is a friend of mine and likes to fly super high. We were just joking around. Also a lot of motors on thrust curve have thrust curves that vary as much as 30% and my thrust curve app...thing undershot it's prediction by over a 1000 feet! Just look at the curves for the 54mm J275....yikes!
Look I just wanted some general ideas and usually folks at a launch would say " how much does it weigh?".
I also never had an implied expectation the anybody would actually know ALL the 38mm motors. I had a few guys who replied with some good information....I'm good.
 
BTW....I already know how to fish...and I think I am pretty good at launching as well...I also know that I have a lot to learn...but some folks fish, learn and get information in different ways and we all do just fine!
 
It's all good.

Agreed on the thrust curves. There are a lot of questionable files out there that will wreak havoc on the simulations.
 
Thrustcurve, OpenRocket, and RASAero are free of cost.

You asked about 38mm motors and modest altitudes, and ended up getting responses about 54mm motors going to 19,000 ft. I find those comments less useful than a relevant simulation, even one that may differ by 20% from an observation. Past data allows you to tune and better predict the next flight.

I know Andrew and just wanted to say "Hi" in my own special way. Come fly with us some time...... :)
 
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