L2 Rocket Design Questions

[haon151]

Hello everyone! I'm currently trying to design a rocket for my L2 certification. This will be my first time designing a rocket of my own, using electronics, and recovering with dual deploy. As such, I have some questions before I continue. This is a 6ft tall rocket with a 3.9" Quantum airframe using a 54mm motor mount. I plan to fly on an I motor for a test flight then going for my L2 on a J. Don't know what exact motors to use yet. Feel free to give me any additional feedback not related to the questions here.

Images here, and the OpenRocket file is also attached.

1) With dual deploy, when the main parachute is ejected, should the nose cone be blown just by itself off or should the nose cone with the extra body tube be blown off? To secure one or another together, are three #4 pan head screws enough? Also, am I getting the right idea that the shear pins will be placed through the body and into the avionics bay?

2) Is 13 in of body tube enough to fit the main parachute and 18ft of shock cord? I read "Make: High Power Rockets" by Mark Westerfield and there were general packing size guidelines, but just wanted to make sure. Also, how is descent of the main parachute calculated when there is already a drogue deployed? The book gave some sizing numbers, but this didn't take into account the drogue already having been deployed. Just been using simulation numbers, is that okay?

3) Is my stability okay? Only estimated the avionics mass, it's not measured yet. I've heard it should be around 1-2, but is there a more specific rule for this? Is 2.5+ over stable?

4) I am using 2 screw switches in my avionics bay to arm the rocket. These are all modeled in CAD. How do I line this up to drill a hole in the correct spot in my body tube? Is it just taking the dimensions from CAD and sending a prayer? Or is there something better I can do?

5) When does the durability of my centering rings and bulkheads become a concern in regards to parachute deployment? My avionic bulkhead is a total of 9/16" thick with 6/16" of that being 3D printed. The images attached shows this more clearly. Motor centering ring is 1/4" thick. Each piece will have forged eyebolts attached. Does this system give enough strength for parachute deployments? Is a plastic nosecone also suitable?

I have more questions, but I don't want this post to get too long. Thank you all in advance!

 

[Handeman]

Hello everyone! I'm currently trying to design a rocket for my L2 certification. This will be my first time designing a rocket of my own, using electronics, and recovering with dual deploy. As such, I have some questions before I continue. This is a 6ft tall rocket with a 3.9" Quantum airframe using a 54mm motor mount. I plan to fly on an I motor for a test flight then going for my L2 on a J. Don't know what exact motors to use yet. Feel free to give me any additional feedback not related to the questions here.

Images here, and the OpenRocket file is also attached.

1) With dual deploy, when the main parachute is ejected, should the nose cone be blown just by itself off or should the nose cone with the extra body tube be blown off? To secure one or another together, are three #4 pan head screws enough? Also, am I getting the right idea that the shear pins will be placed through the body and into the avionics bay?

2) Is 13 in of body tube enough to fit the main parachute and 18ft of shock cord? I read "Make: High Power Rockets" by Mark Westerfield and there were general packing size guidelines, but just wanted to make sure. Also, how is descent of the main parachute calculated when there is already a drogue deployed? The book gave some sizing numbers, but this didn't take into account the drogue already having been deployed. Just been using simulation numbers, is that okay?

3) Is my stability okay? Only estimated the avionics mass, it's not measured yet. I've heard it should be around 1-2, but is there a more specific rule for this? Is 2.5+ over stable?

4) I am using 2 screw switches in my avionics bay to arm the rocket. These are all modeled in CAD. How do I line this up to drill a hole in the correct spot in my body tube? Is it just taking the dimensions from CAD and sending a prayer? Or is there something better I can do?

5) When does the durability of my centering rings and bulkheads become a concern in regards to parachute deployment? My avionic bulkhead is a total of 9/16" thick with 6/16" of that being 3D printed. The images attached shows this more clearly. Motor centering ring is 1/4" thick. Each piece will have forged eyebolts attached. Does this system give enough strength for parachute deployments? Is a plastic nosecone also suitable?

I have more questions, but I don't want this post to get too long. Thank you all in advance!

Just my opinions, so I'm sure others will have different ideas. I really like that you are using a 4" rocket with 54mm MMT. I think that is a great L2 rocket, especially if it can handle the 54mm J, K and L motors available. I'm not sure about using Quantum airframe, but you should be able to use most of those motors with that.

1. Yes, the payload tube stays with the av-bay. That is the standard way to do it because people have found it works best. I use two #6 screws to hold the payload to the av-bay on everything up to 4". I only use shear pins on fiberglass BT. Anything else I use friction fit and haven't had any issues.

2. I'm not sure what you used to calculate that, but my L2 cert rocket started out with a 24" payload bay, 16" internal space. By the time I retired it with 50 flights, the payload bay was up to 36". There is no reason to make it a minimal length. Make it long enough you don't have to struggle to fit the chute, shock cord, dog barf, etc. in the tube. More space is better.

3. 1-2 stability is fine. You might want to make sure it's over 1.5 if you are exceeding Mach, but with Quantum tubing, that probably shouldn't happen.

4. I use index pins to make sure the av-bay caps align exactly every time. I also use index pins to make sure the BTs align to the switch band exactly every time. With that rotational alignment, it should be very simple to determine the vertical alignment of the switch locations and determine exactly where to drill the holes. I actually use pull pin switches in the switch band and series screw switches on the coupler and find it very easy to drill the 1/8" holes in the switch band to line up with the pull pin switches.

5. Your .ork file really doesn't show details very well. I haven't used eye-bolts for years. I glue a Kevlar loop to the MMT for the fin can attachment. I use u-bolts on the av-bay caps, and usually a u-bolt on the nose cone cap also. I wouldn't trust any 3D printed caps/o-rings to add any strength to wooden or fiberglass CRs.
As for how much strength you need for deployment, a lot of that depends on your deployment charges. If you believe in "blow it out, or blow it up", than you should add a lot of strength and larger, heavier, eye-bolts/u-bolts to all the recovery points. Also, going drogueless tends to have the rocket come down ballistic with the payload leading the fincan. When the main opens, the shocks on the recovery system is very large, especially when the fin can finally hits the end of the shock cord after the main has already opened. You may want to make the eye-bolts/u-bolts even stronger and heavier.

 

[Voyhager3]

Just my opinions, so I'm sure others will have different ideas. I really like that you are using a 4" rocket with 54mm MMT. I think that is a great L2 rocket, especially if it can handle the 54mm J, K and L motors available. I'm not sure about using Quantum airframe, but you should be able to use most of those motors with that.

1. Yes, the payload tube stays with the av-bay. That is the standard way to do it because people have found it works best. I use two #6 screws to hold the payload to the av-bay on everything up to 4". I only use shear pins on fiberglass BT. Anything else I use friction fit and haven't had any issues.

2. I'm not sure what you used to calculate that, but my L2 cert rocket started out with a 24" payload bay, 16" internal space. By the time I retired it with 50 flights, the payload bay was up to 36". There is no reason to make it a minimal length. Make it long enough you don't have to struggle to fit the chute, shock cord, dog barf, etc. in the tube. More space is better.

3. 1-2 stability is fine. You might want to make sure it's over 1.5 if you are exceeding Mach, but with Quantum tubing, that probably shouldn't happen.

4. I use index pins to make sure the av-bay caps align exactly every time. I also use index pins to make sure the BTs align to the switch band exactly every time. With that rotational alignment, it should be very simple to determine the vertical alignment of the switch locations and determine exactly where to drill the holes. I actually use pull pin switches in the switch band and series screw switches on the coupler and find it very easy to drill the 1/8" holes in the switch band to line up with the pull pin switches.

5. Your .ork file really doesn't show details very well. I haven't used eye-bolts for years. I glue a Kevlar loop to the MMT for the fin can attachment. I use u-bolts on the av-bay caps, and usually a u-bolt on the nose cone cap also. I wouldn't trust any 3D printed caps/o-rings to add any strength to wooden or fiberglass CRs.
As for how much strength you need for deployment, a lot of that depends on your deployment charges. If you believe in "blow it out, or blow it up", than you should add a lot of strength and larger, heavier, eye-bolts/u-bolts to all the recovery points. Also, going drogueless tends to have the rocket come down ballistic with the payload leading the fincan. When the main opens, the shocks on the recovery system is very large, especially when the fin can finally hits the end of the shock cord after the main has already opened. You may want to make the eye-bolts/u-bolts even stronger and heavier.

Wait, so I see how you said that the upper payload tube should be attached to the av-bay, but for mine I have it attached to the NC. Do you think that would be too risky, and I should flip it around?
I’m also (maybe) prepping for an L2

 

[Buster]

Hello everyone! I'm currently trying to design a rocket for my L2 certification. This will be my first time designing a rocket of my own, using electronics, and recovering with dual deploy. As such, I have some questions before I continue. This is a 6ft tall rocket with a 3.9" Quantum airframe using a 54mm motor mount. I plan to fly on an I motor for a test flight then going for my L2 on a J. Don't know what exact motors to use yet. Feel free to give me any additional feedback not related to the questions here.

Images here, and the OpenRocket file is also attached.

1) With dual deploy, when the main parachute is ejected, should the nose cone be blown just by itself off or should the nose cone with the extra body tube be blown off? To secure one or another together, are three #4 pan head screws enough? Also, am I getting the right idea that the shear pins will be placed through the body and into the avionics bay?

2) Is 13 in of body tube enough to fit the main parachute and 18ft of shock cord? I read "Make: High Power Rockets" by Mark Westerfield and there were general packing size guidelines, but just wanted to make sure. Also, how is descent of the main parachute calculated when there is already a drogue deployed? The book gave some sizing numbers, but this didn't take into account the drogue already having been deployed. Just been using simulation numbers, is that okay?

3) Is my stability okay? Only estimated the avionics mass, it's not measured yet. I've heard it should be around 1-2, but is there a more specific rule for this? Is 2.5+ over stable?

4) I am using 2 screw switches in my avionics bay to arm the rocket. These are all modeled in CAD. How do I line this up to drill a hole in the correct spot in my body tube? Is it just taking the dimensions from CAD and sending a prayer? Or is there something better I can do?

5) When does the durability of my centering rings and bulkheads become a concern in regards to parachute deployment? My avionic bulkhead is a total of 9/16" thick with 6/16" of that being 3D printed. The images attached shows this more clearly. Motor centering ring is 1/4" thick. Each piece will have forged eyebolts attached. Does this system give enough strength for parachute deployments? Is a plastic nosecone also suitable?

I have more questions, but I don't want this post to get too long. Thank you all in advance!

I recommend Single Deploy. You don’t want this to be overly complicated. KISS. You don’t want to introduce Single Point Failures into a Cert attempt. If you are going over 4,000 ft AGL then maybe Dual Deploy.

 

[Handeman]

Wait, so I see how you said that the upper payload tube should be attached to the av-bay, but for mine I have it attached to the NC. Do you think that would be too risky, and I should flip it around?
I’m also (maybe) prepping for an L2

The payload tube attached to the NC can work. Most people use charge wells on the forward cap of the av-bay and find it works better when ejecting the nose cone and recovery gear from the payload tube attached to the av-bay. Where you want to attach the payload tube is up to you, but you should make sure the dependability of your system is acceptable to you.

 

[haon151]

Just my opinions, so I'm sure others will have different ideas. I really like that you are using a 4" rocket with 54mm MMT. I think that is a great L2 rocket, especially if it can handle the 54mm J, K and L motors available. I'm not sure about using Quantum airframe, but you should be able to use most of those motors with that.

Pretty unknowledgeable about airframes, what should I be using instead?

2. I'm not sure what you used to calculate that, but my L2 cert rocket started out with a 24" payload bay, 16" internal space. By the time I retired it with 50 flights, the payload bay was up to 36". There is no reason to make it a minimal length. Make it long enough you don't have to struggle to fit the chute, shock cord, dog barf, etc. in the tube. More space is better.

Will do, I'll make it longer.

3. 1-2 stability is fine. You might want to make sure it's over 1.5 if you are exceeding Mach, but with Quantum tubing, that probably shouldn't happen.

Sounds good. I think the stability number should go down when I build it due to the weight of fillets and other hardware.

4. I use index pins to make sure the av-bay caps align exactly every time. I also use index pins to make sure the BTs align to the switch band exactly every time. With that rotational alignment, it should be very simple to determine the vertical alignment of the switch locations and determine exactly where to drill the holes. I actually use pull pin switches in the switch band and series screw switches on the coupler and find it very easy to drill the 1/8" holes in the switch band to line up with the pull pin switches.

Never seen those before. Could you link to what you mean?

5. Your .ork file really doesn't show details very well. I haven't used eye-bolts for years. I glue a Kevlar loop to the MMT for the fin can attachment. I use u-bolts on the av-bay caps, and usually a u-bolt on the nose cone cap also. I wouldn't trust any 3D printed caps/o-rings to add any strength to wooden or fiberglass CRs.
As for how much strength you need for deployment, a lot of that depends on your deployment charges. If you believe in "blow it out, or blow it up", than you should add a lot of strength and larger, heavier, eye-bolts/u-bolts to all the recovery points. Also, going drogueless tends to have the rocket come down ballistic with the payload leading the fincan. When the main opens, the shocks on the recovery system is very large, especially when the fin can finally hits the end of the shock cord after the main has already opened. You may want to make the eye-bolts/u-bolts even stronger and heavier.

What other details should I be adding? I will look into the Kevlar loop solution. Should I just buy premade wood caps then? I will have a drogue parachute.

 

[haon151]

I recommend Single Deploy. You don’t want this to be overly complicated. KISS. You don’t want to introduce Single Point Failures into a Cert attempt. If you are going over 4,000 ft AGL then maybe Dual Deploy.

Have never done a dual deploy before, so wanted to learn. I could launch it a few times before to gain experience. Still a bad idea?

 

[Handeman]

I recommend Single Deploy. You don’t want this to be overly complicated. KISS. You don’t want to introduce Single Point Failures into a Cert attempt. If you are going over 4,000 ft AGL then maybe Dual Deploy.

I can't disagree with this.
I'm probably not the right person to respond, since I did my L1 cert with DD because I wanted to do that. For my L2, DD was a given since I used a K motor and wouldn't fly that high at my field without DD. I don't think "complicated" or "single point failure" is really the issue. I think it has a lot more to do with what rocket you built, how high it will go on your cert flight, and most importantly, how high it will go on the motors you want to fly it on after your cert, and what altitudes your home field can handle.

In my opinion, that is something you should learn while flying L1 before going for L2. In my case, 3,000 ft., depending on the day, was a good max altitude for apogee deploy. Most days, 6,000 to 8,000 was a good max for DD. Either way, you need to learn to fly the field and learn how high you can safely fly under various weather conditions.

I think if you want to fly K and baby L motors on 54mm then you should fly a cert rocket that can handle those motors. Even on a baby J, you need to prove, not just for the cert, but to yourself, that your rocket will be able to recovery correctly on your field. If you want to fly large J, K and L motors, I don't see any reason you shouldn't fly a cert flight that shows you can do that.

 

[Handeman]

Pretty unknowledgeable about airframes, what should I be using instead?


Will do, I'll make it longer.

Sounds good. I think the stability number should go down when I build it due to the weight of fillets and other hardware.

Never seen those before. Could you link to what you mean?

What other details should I be adding? I will look into the Kevlar loop solution. Should I just buy premade wood caps then? I will have a drogue parachute.

I have a 20 year old Public Missiles Callisto with Quantum tubing that I am still flying. The thing about Quantum tubing is you shouldn't really fly it above 0.8 Mach or in cold weather. It can be done, but as PML says, it's not recommended.

My L2 was LOC tubing with two layers of 6 oz. fiberglass cloth. Not because the fiberglass was needed, but because I wanted to learn how to do the wraps.

The index pins is something I install. I drill 3/16" holes with a Brad Point drill bit at the joint.



I then epoxy in a piece of 3/16" dowel. You could use 1/4" or wood also.


Once all the index pins are in, I drill any screw holes or shear pin holes. That way all the screw holes and shear pin holes are always aligned when the index pins are in place. I include the nose cone with index pins. All the pins give me an aligned rocket base on the launch buttons. That means when I install the GPS tracker in the nose cone, I know the GPS chip will not be facing the rail and not be able to pick up satellites.

As for drogue chutes, I've found that it usually takes 2 - 3 flights before I'm able to adjust the size of the drogue chute to get the drop profile that I want.

 

[haon151]

I have a 20 year old Public Missiles Callisto with Quantum tubing that I am still flying. The thing about Quantum tubing is you shouldn't really fly it above 0.8 Mach or in cold weather. It can be done, but as PML says, it's not recommended.

I see, I understand. I am not interested in pushing speed. I have done some sims, and everything is below mach 8. Will do simulations more for K and L motors as well to be completely sure this is the right choice.

I then epoxy in a piece of 3/16" dowel. You could use 1/4" or wood also.
View attachment 573187

That is extremely clever. Cool idea.

As for drogue chutes, I've found that it usually takes 2 - 3 flights before I'm able to adjust the size of the drogue chute to get the drop profile that I want.

Ah, okay. I will probably follow sim information and tweak if I see any issues.


Another question, how high until GPS becomes more of a necessity? Wasn't planning on using one for this rocket unless I had to.

 

[JackC]

If you aren't interested in pushing speed, I recommend big, low and slow for an L2 with single deployment. This type of rocket is great for small fields and only goes to 1500 feet or so, allowing you to track it during its flight. Think Loc Precision Warlock or along those lines. Use a 54mm mount, adapt down to a 38mm J motor, use motor ejection, fly it, recover it and you’re done. Use the KISS principle. Save all the cool, DD stuff after you certify. Keeping it simple reduces the stress on your nerves. Besides, no one awards you style points when you successfully certify.

 

[Banzai88]

Having learned just about every discipline for L2 at my overly long L1 (and MPR) stage, and having gotten off my butt for my L2 two years ago, I'm going to go ahead and say that I agree with Handeman on his recommendations. I was comfortable with DD, having had over a hundred DD launches, and plenty of L1 launches on full size L1 motors in 4" birds.......so my L2 project was just another build, and my L2 launch was just another 'new rocket' launch.

Another reason for building a fully L2 capable bird is that my L1 was a beefed up MP rocket, and hardly suitable for flying any other L1 motors. I had to build another rocket to do that. I chose to build my L2 bird as a 'fully capable' instead of a one-off.

I did my L2 as a scratch built, 4" 54mm motor mount, full dual redundant DD with GPS in the nose. It's a rocket that I can fly from 1500ft to 8000ft comfortably to 'fly the field' and it will eat anything L2 in 38 or 54 that's installed in it. It's large enough to work on easily, large enough to see comfortably all the way up to 8K, and flexible enough to fly mid and large fields that are suited to L2 motors.

As to your question of needing GPS, that's a personal decision. Most of us can see a 4" rocket up to 6-8K, depends on paint and sky conditions. I think that 'altitude' is really only 50% the determining factor. Field conditions (trees/hills/scrub/line-of-sight to terrain) is at least 50% of it, too.
Bayboro (5 square miles of zero trees and soft plow or low crops) I don't see it as necessary up to about 10K, MDRA Higgs, with all it's trees and ditches and limited sight lines I use it 100% for anything going over 2K.
Similarly, soft plow or sod farm, usually not necessary, but let the beans or corn get over knee high and I use GPS nearly 100%. If you haven't experienced knee high crops eating even the largest of rockets yet, you're in for a real treat the first time you experience it!
Not mandatory, but saves a lot of angst when you can walk right up to it.

 

[Buster]

Have never done a dual deploy before, so wanted to learn. I could launch it a few times before to gain experience. Still a bad idea?

Why not wait until after L2 that way you are not risking the L2 Cert.

 

[tsmith1315]

Have never done a dual deploy before, so wanted to learn. I could launch it a few times before to gain experience. Still a bad idea?

Actually doing this will provide you a far better answer than any of our speculations could.

2) Is 13 in of body tube enough to fit the main parachute and 18ft of shock cord?

Consider ordering an extra length of airframe and an extra coupler or two. Use them to make different configurations for single and dual deployment, different chute sizes/construction, etc.

 

[waltr]

Very well stated Banzai88.

I would not do DD for the first time on a Cert rocket. Get DD experience first with smaller rockets.
I have done lots of DD rockets but did L1 simple. I will do DD for L2 and the rocket has flown once on an I180 at Higgs.
I also use GPS at Higgs for anything over 1500ft.

 

[jmasterj]

Why not just build this rocket to learn DD with I motors? After several successful flights when you're confident in your technique, toss a J in it and get the cert. I agree with others that doing novel things (other than the motor class) with your cert rocket is a risky plan.

 

[haon151]

Having learned just about every discipline for L2 at my overly long L1 (and MPR) stage, and having gotten off my butt for my L2 two years ago, I'm going to go ahead and say that I agree with Handeman on his recommendations. I was comfortable with DD, having had over a hundred DD launches, and plenty of L1 launches on full size L1 motors in 4" birds.......so my L2 project was just another build, and my L2 launch was just another 'new rocket' launch.

Another reason for building a fully L2 capable bird is that my L1 was a beefed up MP rocket, and hardly suitable for flying any other L1 motors. I had to build another rocket to do that. I chose to build my L2 bird as a 'fully capable' instead of a one-off.

I did my L2 as a scratch built, 4" 54mm motor mount, full dual redundant DD with GPS in the nose. It's a rocket that I can fly from 1500ft to 8000ft comfortably to 'fly the field' and it will eat anything L2 in 38 or 54 that's installed in it. It's large enough to work on easily, large enough to see comfortably all the way up to 8K, and flexible enough to fly mid and large fields that are suited to L2 motors.

That is kinda what I was thinking. Building a rocket like this to learn about dual deploy and can take me to the L2 cert and beyond. What changes or recommendations specific to the design I made would you suggest I do to accomplish this?

 

[haon151]

Why not just build this rocket to learn DD with I motors? After several successful flights when you're confident in your technique, toss a J in it and get the cert. I agree with others that doing novel things (other than the motor class) with your cert rocket is a risky plan.

That's my plan. Learn and then be confident going into the L2. Or I can change it to a single deploy for it's cert flight.

 

[haon151]

Actually doing this will provide you a far better answer than any of our speculations could.




Consider ordering an extra length of airframe and an extra coupler or two. Use them to make different configurations for single and dual deployment, different chute sizes/construction, etc.

This makes a lot of sense to me. I'll order some extra in order to configure this thing on how I want to fly it

 

[wsume99]

I would not recommend doing anything for the first time on your L2 flight other than the motor being your first L2 class motor.

If you plan to use dual deploy for your L2 flight then you should absolutely practice dual deployment prior to your cert flight. You can use your L2 rocket for practice however I can see a good reason to not use your L2 rocket the first few times you fly dual deploy. If you mess something up on the first few DD attempts you could damage or completely destroy your L2 bird. I'd recommend practicing dual deployment on another airframe and once you are comfortable do at least one DD shakedown flight with your L2 bird on a L1 motor. Then you will be ready for a cert attempt. That is the safest approach IMO.

 

[JackC]

That's my plan. Learn and then be confident going into the L2. Or I can change it to a single deploy for it's cert flight.

I would change it to single deployment if I were you. Again, you don’t get style points for a fancy or difficult Cert flight.

 

[JackC]

If you have an iPhone, use your compass app to get a bearing on the direction where the rocket has landed and stay on that bearing to recover it.

 

[jmasterj]

You can use your L2 rocket for practice however I can see a good reason to not use your L2 rocket the first few times you fly dual deploy. If you mess something up on the first few DD attempts you could damage or completely destroy your L2 bird. I'd recommend practicing dual deployment on another airframe and once you are comfortable do at least one DD shakedown flight with your L2 bird on a L1 motor. Then you will be ready for a cert attempt. That is the safest approach IMO.

That only makes sense if the practice rocket is cheaper or takes less time to build.

 

[AfterBurners]

If you aren't interested in pushing speed, I recommend big, low and slow for an L2 with single deployment. This type of rocket is great for small fields and only goes to 1500 feet or so, allowing you to track it during its flight. Think Loc Precision Warlock or along those lines. Use a 54mm mount, adapt down to a 38mm J motor, use motor ejection, fly it, recover it and you’re done. Use the KISS principle. Save all the cool, DD stuff after you certify. Keeping it simple reduces the stress on your nerves. Besides, no one awards you style points when you successfully certify.

so many choices it seems. I tend to agree with this approach has well. Another option to this approach you can use a JLCR if you wanted to take it a bit higher?

 

[thzero]

Have never done a dual deploy before, so wanted to learn. I could launch it a few times before to gain experience. Still a bad idea?

No, its neither bad nor good. I did mine with dual deploy, no problem, and sure others have to.

That being said, build a smaller (i.e. cheaper!) rocket that you can go practice dual deploy and get familiar with the electronics and all. Just doing it for first time on cert flight probably isn't optimal.

 

[thzero]

4) I am using 2 screw switches in my avionics bay to arm the rocket. These are all modeled in CAD. How do I line this up to drill a hole in the correct spot in my body tube? Is it just taking the dimensions from CAD and sending a prayer? Or is there something better I can do?

Because I have 3d printers, I print out 3d drill guides and jigs.

 

[OzHybrid]

If you aren't interested in pushing speed, I recommend big, low and slow for an L2 with single deployment. This type of rocket is great for small fields and only goes to 1500 feet or so, allowing you to track it during its flight. Think Loc Precision Warlock or along those lines. Use a 54mm mount, adapt down to a 38mm J motor, use motor ejection, fly it, recover it and you’re done. Use the KISS principle. Save all the cool, DD stuff after you certify. Keeping it simple reduces the stress on your nerves. Besides, no one awards you style points when you successfully certify.

Certification is like a driving test. You want to turn up for that with a vehicle that has good all-round visibility and is easy to drive. Very few people would turn up to a driving test in a Ferarri. Blip the throttle and you spin out and fail. Yet that seems to me what many cert attempts are. Way outside the examinee's comfort zone.
So find a comfortable rocket and pass the exam. Then buy a Ferarri if you still think it's a good idea and you can afford it.
Norm

 

[Voyager1]

Certification is like a driving test. You want to turn up for that with a vehicle that has good all-round visibility and is easy to drive. Very few people would turn up to a driving test in a Ferarri. Blip the throttle and you spin out and fail. Yet that seems to me what many cert attempts are. Way outside the examinee's comfort zone.
So find a comfortable rocket and pass the exam. Then buy a Ferarri if you still think it's a good idea and you can afford it.
Norm

Well stated Norm!

 

[Lt72884]

For a first level 1 and 2 flight, its nice to keep it simple and relaxed. Its like cruising down old mainstreet on a cool summers night.
here is what i have been doing for my first design:
i purchased a 4 inch diameter cardboard mailing tube from the local print shop. Cost me $8
i followed the fin design from G.H.Stine in his book and created a nice set of fins that i 3d printed/laser cut/jigsaw
I created an ogive nose cone from the equation listed in the wiki nose cone design article.
used a laser cutter or scroll saw to cut 3 centering rings from some scrap 0.25 ply wood
used an old aerotech motor holder tube, the ones the motors come in as the actual motor tube.
Used a nylon material to make the chute
purchased shock-cord from my local farming store
put it all together and you have a nice rocket for level 1 and 2.

i also just recieved a jolly logic. great little device. i highly recommend it

Hope this helps.

 

[user 30299]

Using dual deployment (DD) for your L2 flight is only a big challenge if you make it a big challenge.
Be patient and keep it simple.

I did DD for my L2 flight. I used LOC's EZI-65 kit for my base design. I have attached the design in a PDF file.
This is a 4" dia. rocket, cardboard. I used/use a single RRC2 and 9-volt battery. I've had this rocket for a very
long time, and it's flown on "I" through "K" motors, warp motors too.

The most noticeable change to the basic EZI kit is the 24" long motor tube. I wanted to eventually put the
rocket up on a K1050 motor - which at the time was the only motor AeroTech made for the 2800 case.


I've included the drawing so that you can get a feel for the available space for your harnesses and chute.
I use 25 ft. harnesses, 7/16" Kevlar - and I think Teddy (OneBadHawk) made them for me. I use a 50" Top
Flight chute for the Main. The top payload area has all kinds of room.

The GPS tracker is for those launches where the winds are questionable above 4,000 ft. And there are
plenty of motors that keep the altitude under 3,500 ft. - which was the limit on the original field this
was regularly launched on.

There is no drogue chute in the lower payload - for Apogee separation. The 25 ft. harness, along with
a nomex blanket and zipper protection fit snuggly in this lower payload. I wish at times it had another
inch or two of length. But that was sacrificed when I put in the 24" motor tube. Live & Learn.

This kit went back to the days when Barry still owned LOC, and his shop was here in Ohio. This explains
the (2) 11" tubes and coupler to make up the top section. The kit came with one 11" section. When I
decided to go DD I needed to extend the top section - so I just added another 11" tube.

In those days the kit had 1/8" plywood fins. I changed them to 1/4" at the advice of the more
experienced people. Glad I did. I think 1/4" is now standard in the LOC kit.

I have included a couple of pictures of the "avionics" bay. I have to laugh at how simple & barren it
is compared to the avionics bays I now put together.

I spent most of my time on the GPS compartment in the nose cone. I rarely have to use it, it was not
a necessity for the L2 cert. It comes in handy now - but I could have skipped that extra work for my
L2 cert flight. Oh well, Live & Learn.

I'm glad I did the DD for my L2. It gave me the opportunity to learn some good stuff from the
experienced people at the launches - and it built up their confidence, and mine, that I would have
a good first launch. It made the cert flight more fun, along with a greater sense of accomplishment.