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Level 2 questions

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davalf

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After finishing up my level 1 project (yet to certify) I am already looking ahead. My next rocket I want to use for a level 2 cert. I want it to be a large rocket, 5.5" in dia. and 6-8' tall. I want to use a central 54mm mmt and 3 surounding 29mm or 38mm mmts. I was just wondering if there was a weight issue I need to worry about. I also want to have the capability of using motor ejection. I was hoping to build the rocket minus all the electronics and be able to fly it, then add stuff as funds allow. Now, is this to ambitious for a level 2? And is the rocket to large? Thanks

Dave
 

WillMarchant

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If you want to do test flights on H and I motors then, yes, you do need to worry about mass. I like the Loki I405 motor, so I'll use that as an example.

The rule of thumb is that you want about a 5 to 1 thrust to weight ratio. And another rule of thumb is that you can use the motor average thrust as part of that. So, take the 405 average thrust in Newtons of the Loki I405 and divide that by 5 to get 81. And then convert that from metric to English units by dividing by 4.4 to get a maximum liftoff weight of about 18 pounds. That's just to get it going safely off an average length rail in a fairly low speed wind.

The I405 will get one of my 9 pound rockets to about 1200'. That's the other thing you need to worry about: getting high enough for safe deployment of your recovery system.

RockSim will let you play more games. But keep an eye on having a safe velocity off the end of the rail and on keeping to a reasonable altitude.

But, yes, it is possible to build a rocket that you can test fly on L1 motors and then do your L2.

Have fun!
 

ben_ullman

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you mentioned outboards, remember to plug those. speaking from experience! If you don't plan on plugging them just leave the ejection charge out and save it for another flight. Because the results will be the same!! :)

Ben
 

Handeman

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There are no weight limits or weight requirements for any certification level. All certifications are based on the motor size.

No, that isn't too big or too ambitious for a Level 2 rocket. That sounds like a rocket that is solidly in the middle of the Level 2 range.

As Will mentioned, you will have to decide on weight limits as part of your design and intended flight profiles. If you want to fly it on a single H or I motor, then the designed weight limit will be much lower. If you are always going to use L2 motors, like at least a K motor, then you could have a rocket that weighs up to 25 lbs and still fly it with most available K motors.

As Ben said, if you are going to use motor ejection, make sure any escape paths for the ejection gases through the clustered motor tubes are plugged before flight, or better yet, eliminated by design.

You can certainly add additional electronics later, although I would definitely recommend including them in the initial design.

Something you might want to consider is adding the electronics to your Level 1 rockets. Getting experience with dual deploy in L1 rockets before you start using it on a large, expensive L2 rocket isn't a bad idea. Besides, if you're like me, after using the dual deploy a few times. I would much rather fly with DD then motor ejection.

I would suggest you get an altimeter and fly some L1 rockets with dual deploy before you finalize the design of your L2 rocket. You may find you don't want to fly the L2 with motor ejection at all.

Good Luck on the L1 cert and keep us up to date on the L2 build. Pictures!
 

davalf

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Would just a bulkhead in the outboard mmt's be suffecient? And for the rocket, I havent started designing it yet except for in my head. My rocsim trial has expired and would rather spend the 120 on more rockets.

Right now I am intimidated by electronics. But, I want to learn. I had planned on designing them into the rocket and later add. I was hoping to be able to cert level 2 at LDRS in june but I am not set on that. I want to make sure I am comfortable with level 1 rockets before hand.

Dave
 

Handeman

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Would just a bulkhead in the outboard mmt's be suffecient? And for the rocket, I havent started designing it yet except for in my head. My rocsim trial has expired and would rather spend the 120 on more rockets.

Right now I am intimidated by electronics. But, I want to learn. I had planned on designing them into the rocket and later add. I was hoping to be able to cert level 2 at LDRS in june but I am not set on that. I want to make sure I am comfortable with level 1 rockets before hand.

Dave
If you make your top CR for just the central 54mm, that will seal the outside tubes and work quite well if you want to use motor ejection from the center motor.

As for the electronics, I bought a Perfectflite HiAlt45. It has two very high current pyro channels, is easy to set up, and runs on a 9V battery. It doesn't record anything so it only beeps out max altitude when the flight is over. It's very simple to use and reliable.

If you get an altimeter, play with it. I got mine because I wanted to use dual deploy for my L1 cert. I put the altimeter in the rocket and did a lot of ground testing. You can use Estes igniters and a controller for testing the amount of FFFFg that is needed, but I used a tube and suction cup to apply vacuum to the electronics bay to actually test the altimeter and charges as a single system. That verified that I had everything connected correctly and that the charges worked correctly.

I used a piece of IV tubing (I kept the extra from the IV kit the last time I was in the ER) and a suction cup.

Tape the suction cup over one of the E-bay ports and tape over the rest of the e-bay port holes. When the altimeter is powered up and ready for flight, suck on the tube. When you can't get any more air out of it, pinch off the tube. The apogee charge should fire right away and unless you have a perfect seal, the main deploy charge should go off a short time later. I have some COPD and can still get almost 2000ft on the altimeter when the E-bay and tape provide a good seal.

You do want a good seal in the e-bay or the pressure from the charges could be getting into the e-bay and mess with the altimeter readings.

Testing like this will give you a good idea of how well your e-bay is sealed and also verify your altimeter installation. You will also get familiar with the altimeter and how it works before you actually fly with it. Do enough testing like this and the first flight will be almost anti-climatic.

Here's a pic of the tube and suction cup I use.

IMG_0054.jpg
 
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Sailorbill

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I ran a sim on a 6" PML Ultimate Endeavour with a three 38mm cluster plus the central 54mm. With the added 38-54mm adapter total simmed weight was nearly 14 lbs. Length 108".
Simulated launch on a CTI I540 with a 7 sec. delay made 1262' with plenty of speed off the 120" rod (52mph) and time for deployment.
I attached a file.

View attachment UltEndeavour_partialw-3X38mm.rkt
 

WDG

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If you do a central 54mm and three outboards, I would suggest going with 38mm for the outboards. It is much easier adapting down than up.

I scratch built (sorta) a stretched stepped type traffic cone with a 54mm and three 38mm mounts. It was only 52" tall and flew plumb bob straight. Every set up required checking stability. Originally this rocket was done as a quickish build to test my electronics for air starts. It became a goal to break mach (never happened) and 1 mile in altitude (also never happened). On a K1200 redline to 3 AT I245 mojave green motors things were going great until right after burn out of the air starts. Apparently even though it was gong no where near mach, I should have used mach lock on the RC2 altimeter. It got confused with the sudden change of acceleration and with all that turbulence from the steps of the body, it threw out the main almost at motor burnout. Very briefly the nose cone went upward, but slowed down quickly. The fat end of the rocket didn't slow down nearly as quickly and essentially cut the top in half. Everything - except the parachute - which stayed inflated with a quick link, one fin (which seemed to last until it hit the block of epoxy added to the nose for weight) and the RF transmitter hung together and flopped back down. It only made it to 3800 ft. I think it would have made it to a mile had things gone right. But, it did encourage me to quit messing with traffic cones and get my 2 stage rocket in the air.

Good luck with your certs.
 

cbrarick

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Get yourself a wildman jr and a perfectflight mwad, and practice your dd before you start adding the complexity of clustering. Then go for the bigger rocket with the fancy clustering. Here's the benefits:

1. You can learn how to do electronics without worrying about an expensive, large rocket.
2. The mwad is one of the easiest altimeters to use - foolproof!
3. You can incrementally learn dual deploy (start with motor at apogee, then mains on your altimeter
4. It comes with the "indestructible" guarantee. Build it right and the wildman will replace it if you can break it (but I've had a altimeter fail and it spun in without parachute (but not ballistic) no damage!
5. Even with an aeropack retainer, it's still pretty cheap so even if you do destroy it, you're only out a few bucks vice the big one.
6. You can even do your level 2 on the wildman jr - I did!

JMHO
 

Handeman

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Get yourself a wildman jr and a perfectflight mwad, and practice your dd before you start adding the complexity of clustering. Then go for the bigger rocket with the fancy clustering. Here's the benefits:

1. You can learn how to do electronics without worrying about an expensive, large rocket.
2. The mwad is one of the easiest altimeters to use - foolproof!
3. You can incrementally learn dual deploy (start with motor at apogee, then mains on your altimeter
4. It comes with the "indestructible" guarantee. Build it right and the wildman will replace it if you can break it (but I've had a altimeter fail and it spun in without parachute (but not ballistic) no damage!
5. Even with an aeropack retainer, it's still pretty cheap so even if you do destroy it, you're only out a few bucks vice the big one.
6. You can even do your level 2 on the wildman jr - I did!

JMHO
I haven't really looked at the larger kits, but your suggestion of the Wildman Jr. in this case is right on. At $100 for a motor/dual deploy rocket you can't go wrong. I just guessed at a weight of 48 oz and a Cd of 0.6, but a Hobbyline G64W will get you 770 ft. and the Loki J1000 will top out near 1.6 Mach and 12,000+ ft. That sounds like a great rocket to learn electronics while pushing the envelope on speed and altitude.
 

GaryT

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IMO Stick to one level at a time, Do your L1 and if you get that? there is a plethora of H's and I's to fly single or DD with, The leveling up process is just that a process, Take your time with each, You'll learn more and become a better flier in the long run, Its not a race, Also you can't fit a 54mm and 38mm in a 5.5" Tube.
 

davalf

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IMO Stick to one level at a time, Do your L1 and if you get that? there is a plethora of H's and I's to fly single or DD with, The leveling up process is just that a process, Take your time with each, You'll learn more and become a better flier in the long run, Its not a race, Also you can't fit a 54mm and 38mm in a 5.5" Tube.
I was waiting for someone to say that. I have heard of several people certing level 1 and 2 with the same rocket. That does not sound fun to me. I have the most fun designing and building. And if I do not have something to build, the only thing I have to do at home are honey dos. I plan on starting this rocket within a couple of months. I am in no rush. I am hoping to fly it at LDRS though. But thank you all for the advice.

Dave
 
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