Questions! Please help!

Hello, I'm new to this forum, and also new to starting Mid-High power rocketry. I'm building a large 4.2 ft rocket with a 4'' diameter. It's not done yet but I estimate it'll way about 2-3 pounds. I have no electronic equipment like alterminers inside the rocket, and I'm trying to push the borders of Mid power rocketry to a whole new level. This is a long post, if you could help I would really like it!

First I have a question about choosing the right motor:

I have a 29mm motor mount, so I can only accept a large high power G motor, (has to have a impulse of over 100 n/s) and I don't want a online HazMat fee, (I'm trying to stay in the 100-dollar range) also, I want a single shot, not a re-loadable or kit motor, since I'm kinda a newbie to rocketry, I don't have a L1 certificate. Buying it in person at a store would be the best option, since I don't want to pay a HazMat fee and I don't want to email my I.D. and everything.

Second I have a question about bulkheads:

I ran into this whole thing about having a bulkhead to protect your payload from burning and stuff, and I don't know what to do, my shock cord is running from the top motor mount ring to the nosecone, so I don't think it's necessary.

Third I have a question about ejection charges:

Do I need a ejection charge to pop the top off my nosecone? I can't legally buy black powder in my area, and I don't think it's needed. Is it only needed when your working with really big rockets? I have a 18 inch nosecone btw, it weighs 10.52oz

Fourth, I have a question about my materials.

In all, these are the things I have:

A motor mount with two rings
A body tube
A nosecone
A shock cord
That little ring thing to attach the shock cord to the nosecone (On the top of the higher centering ring on the motor mount)
That cooling recovery paper wadding stuff
A 48'' nylon parachute
And I'm building my fins

Is there anything I'm missing?


I know this is a really long thread but I'm new to this higher power kind of stuff, and if someone experienced could help me I'd REALLY appreciate it. Sorry about all the questions!

Happy Launching!

-Dunavice
Rocketry Newbie

Welcome to the forum! Lots of information to be had here!

As far as motor selection, have you looked at Thrustcurve.org? Also, might try downloading Open Rocket. Both will help you model & simulate flights for your particular rocket and help decide for you what motors will safely launch your rocket.

https://www.thrustcurve.org/guidepage.jsp

https://openrocket.sourceforge.net/download.html

Most kits have the shock cord attached to a centering ring and the nose cone. Where else would you want to attache it?

You definitely need an ejection charge to pop your nose cone and as far as I know, all single use motors have ejection charges.

As far as "what's missing", what is your kit made of? Fiberglass, cardboard, something else? What kit is it?

I am sure others will chime in here!

Thanks! I have open rocket and I've been pretty good with the tests, however the problem of money chimes in though.
As for the kit, I'm not using one, I'm building my own design.
Now that I know that you need a ejection charge, where can I get it, and where can I get the black powder?
Thanks for the website, I'll be sure to use that!

Thanks so much for the help!

-Dunavice

EDIT:

I looked at the results, and the best motor which was in my legal restrictions was the Cesaroni G54, which I've looked a lot at before.
However, is this like a single shot or like a reload for a thing you have to have?

All single use motors have an ejection charge. You don't need any BP!

A 3 pound rocket on a G80 is doable, however the delay has to be really short. I recently flew a 58 oz rocket an a G64 and a G76 both are Aertech reloads the delays at 4 seconds were barely adequate. A 4" rocket in the 3lb range will have to a pretty light build.

Dunavice said:

I looked at the results, and the best motor which was in my legal restrictions was the Cesaroni G54, which I've looked a lot at before.
However, is this like a single shot or like a reload for a thing you have to have?

Click to expand...

It's a relaod, however very easy to use. All CTI however require HazMat.

Reloads do not require a L1 cert, as long as they're under 80N average thrust, and A-G


I believe it's going to be very difficult to built that rocket under 3 pounds. Note: If you go over 3.3 pounds or 4.4 oz of propellant, you need an FAA waiver.

You don't need a bulkhead, but nomex, paper wadding, or cellulose insulation will protect your chute.

Ejection charges are typically included in motors until you get up in high 54mm or 75mm motors. (no worries for a long time)

If you manage to keep it under 3.3 pounds, there are loadable motors - single use, but you assemble them. Benefit is no hazmat that all the large G single use have.

My favorite motor for this size rocket is the G76G reload for the 29/40-120 case. $10 relaods and no hazmat. Doesn't get much better, and easy to assemble.

Not sure where you are located - the advice I'm giving is based on US laws.

1. If you are less than 18 years old, you can't legally buy ANY reloadable rocket motors (Cessaroni), or ANY motor bigger than an "F" size single-use motor.

2. If your rocket weighs more than 3.3 pounds (ready to fly weight) you will need an FAA waiver to launch it.

3. If the ready to fly weight is about 3 pounds, it will fly on an Aerotech G80 motor. It might only go 500-800 feet high. You can find these G80 motors online for about $20 plus shipping, PLUS $27 hazmat fee. You are not very likely to find any hobby shops that carry "G" motors in stock where you can pick them up locally.

4. If your 3 pound rocket should crash into a person, house, car, etc. you will be responsible for any damages. Do you have insurance, or are you a member of NAR, TRA, or CAR?


Based on your questions - you might want to start with a smaller rocket. A 2.6 inch rocket will fly on an "F" size motor - like the less expensive Aerotech "EconoJet" motors.

Additionally - you might want to fly with a Rocket Club - in the US there are clubs in just about every state.

-Good luck!

Some further thoughts on how to built it lighter:

1/8" birch ply fins and centering rings, maybe even skeletonize the fins a fair bit and skin over with thin balsa/basswood,

Use tubular kevlar in place of all metal parts for shock cord attachment, epoxy tubular kevlar loop to MMT/Centering ring (Wildman Rocketry carries 1/4" tubular kevlar). Use Epoxy to attach the Kevlar. On the Nose Cone if it still has a cone shaped bottom just drill two holes in it and loop your shock cord through and tie securely (make sure all burrs and sharp edges are softened).

Make sure your nylon parachute is made of thin mill nylon (lighter and fits into smaller areas) not that a 48" chute fits tightly into a 4" tube, cuz theres lots of room.

As for bulkheading, the only thing I can see is a 1/8" birch ply shelf installed near the top of the airframe to keep the chute in the upper section of the airframe, punch it full of holes to lighten and attach your shock cord mount to it.

Use OpenRocket to design your build, then override the weights it gives with the actual weight of the parts you make.

Use Titebond/Wood Glue for construction and fillets, to TTW (through the wall) fins. Glue fin tabs to motormount, if you fillet inside the aiframe to fin tab use Titebond or Titebond Trim and Molding Glue (TMTG). External fillets for a G motor dont need to be excessive, and TMTG will do them just fine.

You didn't mention which 4" tubing you are using but I am assuming Loc, between that and the Nose cone you are probably 2 lbs already, with a thin mill parachute, fins, mmt, and shockcord and glue you will be awful close to right on 3 lbs.

My two 58 oz Crayons which were admittedly heavy build (due to necessity) flew to 500' and 530' on a G64W-4 and a G76G-4, parachutes deployed less than 100' above impact with ground. Open Rocket was right on for the sims. Too bad one of my delays was a hair long because my drilling tools bit was loose and drilled about .5 seconds less than I thought, the chute on that one opened at about 40' and with a 20' shock cord the chute deployed at 20', nose cone and altimeter were golden, main body not so much.

Just some thoughts, others might see some faults with them if they do hopefully they will chime in and correct my errors, but weight savings is a must for your build to be able to safely fly on G motors.

Yeah. That's a seriously heavy sounding rocket for a G.

I'm in a similar place as you. Building my first true mid/high power stuff. I'm using the Estes Argent as my build. I have over a quarter century of low power experience. The mid power stuff is very advanced by comparison.

Trust these guys. And look very closely at the AeroTech LMS motors. For the size you want, the budget you have, the fact that you don't want a reload or hazmat, they are your best option.

One more motor option. I have a local hobby shop that will order me motors. If I am patient and wait for their normal hazmat shipment, they'll order them for me at no hazmat fee.

Good luck.

Thanks for all the help guys, I'm keeping it all legal. I'm trying to keep it under three pounds and I'm legally buying the motor. I called a rocket field this rocketry club works in Texas, and they let me use their 4 acre spot to shoot my rocket, it's all open space too.

Dunavice said:

Thanks for all the help guys, I'm keeping it all legal. I'm trying to keep it under three pounds and I'm legally buying the motor. I called a rocket field this rocketry club works in Texas, and they let me use their 4 acre spot to shoot my rocket, it's all open space too.

Click to expand...

I also live and fly my toys in Texas. The following YouTube video is a 5'-5" long, 3" diameter rocket with a total lift off weight of about 2 1/2 pounds and flown on an AT G-76 RMS motor. This launch was conducted on private property and no complaints were filed.

[video=youtube;0cX-fxWGIcc]https://www.youtube.com/watch?v=0cX-fxWGIcc[/video]

Welcome to the forum! This place is full of people with lots of great advice and who don't hesitate to share it. I've personally learned a ton in the fairly short time I've been on here.

I'm pretty sure you can actually buy a G80 motor on Amazon and get it shipped without a hazmat fee. I've bought four or five from them without any trouble and the FBI hasn't knocked down my door yet... if you get your lv. 1 cert. there are a ton of HP 29mm motors that would probably suit you well. The first that comes to mind is the H195. in a large rocket like the one you're building, it probably wouldn't go too incredibly high either. I got my cert. In a 4" rocket using the H195 and it went to around 1000'.

You should keep us updated on your build. Sounds like a cool rocket.

RAHagen said:

Welcome to the forum! This place is full of people with lots of great advice and who don't hesitate to share it. I've personally learned a ton in the fairly short time I've been on here.

I'm pretty sure you can actually buy a G80 motor on Amazon and get it shipped without a hazmat fee. I've bought four or five from them without any trouble and the FBI hasn't knocked down my door yet... if you get your lv. 1 cert. there are a ton of HP 29mm motors that would probably suit you well. The first that comes to mind is the H195. in a large rocket like the one you're building, it probably wouldn't go too incredibly high either. I got my cert. In a 4" rocket using the H195 and it went to around 1000'.

You should keep us updated on your build. Sounds like a cool rocket.

Click to expand...

My video in the preceding post certainly shows that a G76 RMS (or G78 single use) motor has plenty of initial thrust to get a 2 1/2 pound bird going off of a six foot rod on a calm day. Or, you could put twin 29 mm motor mounts in that 4" puppy and fly it on two G80's and still be under the 125 gram FAA propellant limit. But you are going to need considerably more than 4 acres to do so safely.

tmacklin said:

My video in the preceding post certainly shows that a G76 RMS (or G78 single use) motor has plenty of initial thrust to get a 2 1/2 pound bird going off of a six foot rod on a calm day. Or, you could put twin 29 mm motor mounts in that 4" puppy and fly it on two G80's and still be under the 125 gram FAA propellant limit. But you are going to need considerably more than 4 acres to do so safely.

Click to expand...

I'm sure that a G could definitely fly a rocket this size. I'm just saying that if he were to get his lv. 1 he could put some really nice size motors in that rocket.

That's a mighty fine rocket!

Mine is similar to yours.
Maybe I'll consider that motor

I'm thinking about getting a H or I motor so I can attempt for a cert,
that'll work good.

Kind Regards

Dunavice

If you haven't actually built a model rocket before, may I suggest that you build a smaller rocket kit first to get the hang of things? If you have already built smaller kits and flown them, please disregard this and party on! :wink:

I'd definately get "Modern High Powered Rocketry 2" just search it on amazon...then a lot of rocketry will be easily understood. It's got lots of pictures for those of us who do better with the visual stuff.

I would also consider attending a launch before you build. I learned a lot on the field.

An odd, incidental, perk to achieving your level 1 cert is that you are then permitted to fly motors with an average thrust higher than 80, which really opens your motor choices up in the MPR range.

And not for nothing, but reloads are really the way to go.


Later!

--Coop

Has anyone mentioned that you will also need either a launch lug or rail buttons on your rocket? For a 3lbs. 4" dia. you would need at a bare Minimum a 1/4" dia. rod, but I would recommend a 3/8" dia. X 6' long rod. A much better option would be a 1010 rail and buttons. Do you have your own ground support equipment or are you borrowing that?