Help on a new project

[4G's]

Hi guys, I just joined so im still learning the ropes here. I looking to start a new project. First off, anyone know of a website where I can find a 29mm quad cluster engine mount? this is my biggest problem with starting the rocket. Basically I want the rocket to be powered off 4 clustered G size aerotech engines, body tube be constructed out of 2 44in "blue tubes" (Anyone know how these body tubes preform?) heres a link to them: https://www.apogeerockets.com/blue_tubes.asp . Im also going to be using a 50 in nylon recover parachute, please correct me if im going to be using the wrong size (rocket roughly 6-8 pounds when finished). Im still thinking about the fin template. Anyone know a good size, shape and quantity for the fins I should be using? Any help or comments would be greatly apprieciated. Thanks agian guys.

 

[troj]

Those blue tubes are pretty amazing stuff! One of the local guys brought one to a launch so we could check it out, and I'm impressed by it.

Get in touch with Barry and LOC/Precision about your quad motor mount -- ask if he'll cut the centering rings you need for that. Make sure you tell him what tubing you're putting it in, so he can cut it to the proper size.

-Kevin

 

[4G's]

Ok thanks ill take a look. btw have you or anyone you know clustered aerotech engines? I have never used aerotech engines.

 

[JRThro]

A cluster of 4 G motors, equivalent to an I motor, is high power, isn't it?

Someone who has never used Aerotech motors isn't likely to be Level 1 HPR certified.

 

[MarkM]

A cluster of 4 G motors, equivalent to an I motor, is high power, isn't it?

Absolutely!

Someone who has never used Aerotech motors isn't likely to be Level 1 HPR certified.

A good possibility, but not necessarily. Don't forget Loki, CTI, and now defunct Ellis


That brings up the question. ARE you L1 certified?
If not, then this project is not possible until you get your certification.
This project falls into the L1 territory for several reasons:
1) the rocket weighs more than 3.3 lbs exceeding Class 1 rocket limits
2) the combined propellant weight exceeds 62.5g
3) the combined impulse falls into the I class (anything above G requires an L1)

 

[Luv2launch]

Absolutely!



A good possibility, but not necessarily. Don't forget Loki, CTI, and now defunct Ellis


That brings up the question. ARE you L1 certified?
If not, then this project is not possible until you get your certification.
This project falls into the L1 territory for several reasons:
1) the rocket weighs more than 3.3 lbs exceeding Class 1 rocket limits
2) the combined propellant weight exceeds 62.5g
3) the combined impulse falls into the I class (anything above G requires an L1)

I thought it was possible to cluster up to 2 G's for a total of 125 grams before it was considered high power?

 

[hardinlw]

The FAA has a total propellent weight of 125g as one of their limitations. That would be two G engines. The impulse of the typical G engine is 100 N-s impulse which means that two would be on the order of 200 N-s which is above the 160 N-s limit for the G impulse class. There are three limits that you must stay under :

125g total propellent weight
160 N-s total impulse
80 N average thrust

Going over any of those puts you out of the model rocket category. With black powder engines, 125g of propellent would still be under the limit.

 

[BsSmith]

I can cluster 2 G77s in my Titan and still be under the high power limit, exept for the weight of the rocket. So I am not sure if 4 Gs would be a large H or small I, considering that you use single use motors. But anyway, you will need a L1 to fly it.

Igniting composite motors in a cluster is more difficult than BP motors, you will need very hot igniters, such as Magnalite. Do not use E-matches dipped in anything with a G motor! The E-Matches need a larger core in the motor to burn without blowing themselves out of the motor. Using these will probably result in one motor firing without the others, which could be very bad.

 

[MarkM]

The FAA has a total propellent weight of 125g as one of their limitations. That would be two G engines. The impulse of the typical G engine is 100 N-s impulse which means that two would be on the order of 200 N-s which is above the 160 N-s limit for the G impulse class. There are three limits that you must stay under :

125g total propellent weight
160 N-s total impulse
80 N average thrust

Going over any of those puts you out of the model rocket category. With black powder engines, 125g of propellent would still be under the limit.

And 4) 3.3lb total rocket weight - including motors

 

[MarkM]

I can cluster 2 G77s in my Titan and still be under the high power limit, exept for the weight of the rocket.

That's incorrect! 2 G77's give a total impulse of over 200 Ns. That's above the Class 1 limit of 160 Ns. Your Titan flights are high power flights (Class 2).

 

[4G's]

Ok. I thought you had to be level one just to purchase and fly motors larger than G. I did not think it meant that you could not cluster G engines.Can someone send me a copy or give me a link to motor regulations. I would really like to do things legally.

 

[4G's]

I was planning on using 4 aerotech G white lightning motors. Each produces an average thrust of 79n (17.8Ib) making it a total of 316n. The rocket, after all is said and done I assume would be between 5-8 pounds. What level certification do I need to do this?

 

[Handeman]

This would be a level one rocket.

My suggestion would be to go to a club launch and do your L1 cert. Just remember, you CAN'T do it on the cluster rocket unless you use H motors. Even though the total impulse might be H or I level, for a certification, at least one motor has to be an H or I motor.

What you could do is build the 4 x 29 mm cluster motor mount and a 1 x 38mm and make the motor mounts interchangeable. Use the 38mm to cert on an H or I, then put the cluster in and try that. Of course you could also make other types like 38mm + 6 18mm or any other combo you can fit in the rocket.

 

[MarkM]

I was planning on using 4 aerotech G white lightning motors. Each produces an average thrust of 79n (17.8Ib) making it a total of 316n.

For future reference, you don't add up the the average thrust. You add up the TOTAL impulse. You need to familiarize yourself with these terms...impulse (total) and thrust; they have distinctly different units and are two distinctly different types of measurements of a motor. The G79 has a total impulse of ~105 Ns. Four of these would give you a total impulse of ~420 Ns. That's well into the I range. It does not affect the certification required to fly this rocket, but as you can see there is a difference between your math and way it should be done.

 

[4G's]

Ok. A lot of this is a learning experience for me, so now I know that I add up impulse instead of thrust. The biggect rocket I have delt with is a duel E engine rocket...so this is quit a large step. I just turned sixteen in February, so I am not quit as knowledgable as most of you guys are here who, quit possibly, have bachelors degrees in aeronotical engineering or something in that arena. Also I have not been around any other modelers, since the NAR launches are a minimum of a 2 hour drive from here. So I am sort of teaching myself along with the help of you guys.

 

[jj94]

Dual E's? Were the E motors black powder or AP? If you have never clustered AP before, I'd suggest that you try it out and get comfortable with it with smaller motors. If you screw up launching 4 G's at once - even if they light a half a second apart - it can go very bad.

 

[4G's]

They were 2 composite engines. I have figured out how to wire the 4 engines with a 2 motor whip clip. But beyond that, its basically new.

 

[RimfireJim]

Ok. I thought you had to be level one just to purchase and fly motors larger than G. I did not think it meant that you could not cluster G engines.Can someone send me a copy or give me a link to motor regulations. I would really like to do things legally.

Here ya go:
https://www.doug79.com/stuff/HPR_metric9c.pdf

That link can be found here: https://www.rocketryforum.com/showthread.php?t=539

 

[terryg]

From the NAR web site:

Who Needs HPR Certification?

A person needs High Power certification if they:


1. Launch models containing multiple motors with a total installed impulse of 320.01 Newton-seconds or more, or

2. Launches models containing a single motor with a total installed impulse of 160.01 Newton-seconds or more, or

3. Launches rockets that weigh more than 53 ounces (1500 grams), or

4. Launches models powered by rocket motors not classified as model rocket motors per NFPA 1122, e.g.:
1. Average thrust in excess of 80.0 Newtons
2. Contains in excess of 2.2 ounces (62.5 grams) of propellant
3. Hybrid rocket motors

 

[RimfireJim]

Also note, as can be seen on the graphs I linked, that an FAA waiver is required for total propellant mass >125g or for total rocket mass >1500g.

 

[RimfireJim]

Also I have not been around any other modelers, since the NAR launches are a minimum of a 2 hour drive from here. So I am sort of teaching myself along with the help of you guys.

Do you know about the Southern California Rocket Association's launches at the Santa Fe Dam Recreation Area near Azuza? That is 50 miles from Balboa Island, if the Balboa Island where you are is the one in Newport Bay. Yes, that is 2 hours round-trip, if that is what you meant.

There is also DART in San Diego, but that is 90+ miles from Newport Beach to the Mission Bay site, which is limited to G impulse maximum. Their low-high power site is out in the desert east of San Diego.

I'm trying to imagine where you can launch any rockets anywhere around Newport Beach. Do you realize that launching of any rockets (model or high power) is, unfortunately for us hobbyists, highly restricted in California by state law? You have to have 1) permission of the landowner, and 2) permission from the fire protection agency having authority of that land. The second one is the dang near impossible one without being an organized group, e.g. a club.

 

[Handeman]

After reading a little more about your circumstances, I would recommend putting the 4G project on hold for a while. I think you should buy a 24/40 or 29/40-120 hobbyline case and build and launch rockets with the composite motors. After a dozen or so launches with the RMS, you will have a very good idea of what it will take to launch the G79 motors in a cluster. Besides even single E, F, and G motors are more power then you will get with BP.

 

[stickershock23]

YOu can build for 4 g motors but you should probably fly it on something smaller to start.
remember to keep it under 3.3 lbs. if you can do that then yes you can fly this project without a special permit.

As for lighting 4 aerotech motors, it can be done. my der red max airstarts 3 h180s...

Find 4 igniters that match as close as you can (ohms) and send lots of power to them..

now should you do this... probably not. but that never stopped me before.

 

[4G's]

Thanks a lot guys...big help with the rules/regulations and launch sites. Speaking about the launch site, I have heard of some that are as little as 45 minutes away....but due to regulations the limit of power at most of these sites are at best E...for about the rest of the time, the power limit is C. Thats just to small for that distance. I will look into better sites and a certification...thats another question...just how do I go about getting a level one certification?

 

[kramer714]

There are a few groups that launch in Southern California. ROC launches at lucerne Dry lake bed, about 100 miles from Newport www.rocstock.org I have launched up to M motors at Roc. They help lots of people get certified, plus have regular vendors at the launches to buy motors and supplies (and advice!) from.

 

[stickershock23]

I'm not exactly sure were you are in calif. there is also SCRA that launchs 2 or 3 times a month at santa fe dam. they are MODEL rocket only. thats "G" and below.

There is also a central calif launch. that is high power, cant think of the name.
But it is like ROC lots of great guys and they can help you certify LI (and more)

 

[MarkM]

will look into better sites and a certification...thats another question...just how do I go about getting a level one certification?

As someone who is under 18, your only option is to do a NAR Jr level 1 certification. So, you need to find a club that is NAR affiliated; TRA does not have Jr level cert.

There are some limitations to the NAR Jr L1 which can be found on the NAR website at www.nar.org. Other conditions for the cert should be availabe there as well.

 

[4G's]

Ok. What is the difference between level one cert. and jr. level one cet.? Will I be able to purchase H and I motors with my jr cert?

 

[MarkM]

Ok. What is the difference between level one cert. and jr. level one cet.?

AGE!

Will I be able to purchase H and I motors with my jr cert?

Someone else (who has a standard L1 or higher cert) will have to do it for you. You must be 18 to purchase high power motors. Also, you basically need someone to sponsor your flights. You are not allowed to handle, assemble or install high power motors...again, someone will have to do the assembly for you with your input/instruction.

Read the NAR site! The info is there.

 

[4G's]

Ok never mind. I just looked at the nar and rocstock website and basically found out how to get my certification. I can go purchase a kit, like maybe the Sumo that runs of H power, build that, go to a launch, have a level 1 or higher certified modeler purchase one, and there I have it. It does work that way for the most part doesnt it?