How much power?

[moocrew]

I did my best to place this is the right forum..and since i am scratch buliding this i figured this was best place.

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*Specs*
one plastic tube
3' in length
53mm in diameter = 2 1/16th inches...this is to the out side edges.
The thickness of the tubing is 1/16th of an inch.
Weight= 6 3/8 oz. Its rather heavy.

*NOTE: its still just a plane tube i have done no work on it of any type.
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Now that you have the info here's my question.

What type of engine would I need to launch this thing.
I'm not looking to launch it to the moon i would actaully prefer that it doesn't go higher than about 500-600 feet..in my opinion, the lower the better.
So would it be possible to mabey use an Estes D..or mabey E to launch it?

Im open to all opinions

Thank you in advance.

 

[Mike]

Welcome to TRF Moocrew!

I'd suggest downloading the demo version of either RocSim from www.apogeerockets.com or SpaceCAD from www.spacecad.com With them you can input all the data you've just given us and it will then simulate how your model will perform on different motors. They can give you a whole host of different information such as maximum altutude and best delay.

HTH

 

[moocrew]

thanks for the great link Mike. This program will assuredly save my rockets from the horrible fate they usually fly into.

Now I have some questions about the engine setup.

Because of the heavy weight of the body tube the program says I will need
2 estes C-6 engine just so that it will go 322 ft.

my first question is...how do i make both engines ignite at the same time...I don't want this to be a staged rocket.

And is 322 ft enough height that the rocket won't smack into the ground?
It seems like a nice height for what i want..so long as i make a suitable parachute? I don't want the thing to end up in the next state.

Thanks again for your help.

 

[Mike]

Moo,
Would it be possible to use an Estes D instead of two C motors? This would solve your problem of clustering (igniting two or more motors) as you would need a high volt/amp launch system.

I'm not a clustering expert so you'd be best talk to someone who is more experienced...they should chime in here.

You say you're using a plastic body tube, would it be possible to use somthing like Estes tubing? That way you would save a lot of weight and *may* be able to fly on a lower power motor. Also if somthing did go wrong with the flight you'd probably do less damage to whatever it hit than if it was plastic.

Something else I think I ought to highlight is safe flight speed, in order for the fins to be effective the model has to travel at a certain speed, the launch rod is there to guide it until it is going fast enough. I know SpaceCAD tells you minimum launch rod length...I'm not familiar with RocSim but it probably does too. Also be aware this increases in windy weather.

As for parachute size EMRR has a calculator to work out how big your chute needs to be based on weight. https://www.rocketreviews.com/cgi-bin/myemrr/recoverybox.cgi RocSim/SpaceCAD will also tell you what the best delay to use is. This is pretty important as you want the parachute to open when the rocket is as close to apogee (top of flight) as possible, that way its moving slower so your parachute should hold up. Since your rocket is quite heavy make sure you parachute is up to the job.

Hope all that helps. Sorry if I sounded critical at all, there were just some issues I thought I ought to cover. Wasn't too sure what your rocketry experience was either?

 

[KenParker]

To expand a bit on what Mike has said - instead of talking C and D motors, let's talk 18mm motor mount vs 24mm motor mount.

Your Estes B6 and C6 engines are 18mm diameter engines, and you construct an 18mm motor mount (motor mount = mmt). Your Estes D12 engine is 24mm in diameter so uses a 24mm mmt.

I agree with Mike that for the sake of simplicity, you might want to equip your model with a single 24mm mmt instead of a dual 18mm mmt cluster.

Also, Estes now makes a 24mm C11 engine, which I imagine would give you about the same flight as twin 18mm C6's. Then, if you want to send it higher, you could go to the Estes D12, and if you really wanted to kick it up there, you could go to the Estes E9. If you think you will use the E9, you have to design the motor mount to allow for the 3.75" length of the E9, and then use a spacer with the 2.75" length D12 and C11.

You still have even more motor options if you ever want to get into RMS - Reloadable Motor Systems. Aerotech makes a 24mm RMS, and they have many D, E, and even F impulse reloads for it. There are also single use 24mm Aerotech engines, I know they are making E and F SU (Single Use), not sure if they are making any D 24mm SU.

You have *lots* of options with a 24mm mmt.

 

[moocrew]

Mike- Yes the D engine will work i only lose about 6 feet of flight which is decent. So that is probably what I will use. Also the rocket is going to be flown in a nearby 20 acre corn field..so it prolly won't do much damage to anything but itself, but I still under stand what you mean and I may have to even bump the motor up one. As far as the chute goes. I'm getting my grandmother..haha...to stitch me one im pretty sure it will hold.

Ken- Thanks for all the info about the engines...Ill look into those for mabey my next large rocket because I would like to start adding some power. But this rocket is basically a test. I know very little about rocketry so hopefully I will learn alot from this.
Much thanks to both of you.

And since im rambling on...here's another question.
Space Cad says the min. launch rod length needs to be 6.57 ft!
That uhhh...really large compared to my little 2 footer im used to launcing with.
How would I get/make something like that....won't the rod become flimsy?
Im also assuming that this will take a little thicker rod (duh) any ideas about how to do this?

 

[Fore Check]

Originally posted by moocrew

And since im rambling on...here's another question.
Space Cad says the min. launch rod length needs to be 6.57 ft!
That uhhh...really large compared to my little 2 footer im used to launcing with.
How would I get/make something like that....won't the rod become flimsy?
Im also assuming that this will take a little thicker rod (duh) any ideas about how to do this?

Try this link to BMI CAD for your custom launch rod:

https://www.bmicad.com/bmilrod1.html

They make stainless steel and titanium launch rods in various diameters and lengths, up to 6 ft standard and custom lengths above that.


I've got one each of the Deluxe stainless rods in 1/8" and 3/16", both 5 ft long.

I would not recommend going above 5 ft in the 3/16" rod in stainless, because I notice that mine "sags" under its own weight when tilted into the wind (just a tad, but it does.) This is much more noticeable on the 1/8" rod - I'd recommend sticking with the standard 3' rod on the 1/8" size. I didn't drop the load for the titanium rod, but I'm sure that it would be much lighter and "stiffer" feeling than the stainless if you wanted to go much above 5' in the 3/16" size. I use my stainless rod occasionally, but I actually prefer my standard Estes aluminum 1/8" rod because it has less whip to it.

Another thing you might try would be to use rail buttons and a launch rail for your rocket. Rails are extremely rigid and extra long rails are more common than extra long rods, due to the possibility of rod whip on the longer rods.

 

[BlueNinja]

Came in on this thread a little late, but I would recommend a 24mm mount as well. You can use anything form a C11 to a F21. The motors much bigger than a D12 (not including E9) will require Aerotech stuff, You may want a 24/40 reload case.

 

[moocrew]

Alright I have almost all the kinks worked out on this rocket.....
So far I have improved it so that the launch rod only needs to be about 3 ft long...which is easily obtained.
Im using three estes B8 engines to give it a kick but keep it low flying.

Now there are only two questions I have left....so If you guys are getting sick of me yet.....

my first question is....
With the rocket body being so large will the three engines produce enough gas to deploy the chute?
My dad told me about putting an Inner tube inside the rocket to decrease the volume that the gas has to fill.
Is this correct?

And since I'm not real sure how to do a cluster launch...is there anyone who can explain how to do this?

Thanks again for all of you help..when i launch this thing there will be pics.
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EDIT:If you aren't sure about something..or I explained it wrong....I can email anyone the file for my rocket on space cad if this will help clear things up?

 

[Fore Check]

HMMMMMmmmmmmmmmmmmmmm.....

Several questions at once, eh?

OK. First to the main question. Where do you get the B8's???? Haven't seen them in a while. I'd like some too!!!

Nevermind -

I could provide several examples where the interior volume of your rocket airframe is significantly less than other proven designs that use a *single* engine. Your design will have three, so I wouldn't worry about the need for extended engine tubes to reduce the volume between the engines and the nose cone (we call them "stuffer tubes.")

Cluster launching - now that's a more in-depth discussion.

The basics: You're gonna need more "juice" than a standard Estes syle hand-held controller. You'll need a 12 Volt launching system at a minimum. There are many to be had that plug into your cigarette-ligher in your car or directly clip to your car battery for power. Still others, like the one I use from Pratt Hobbies, is a self contained rechargeable unit. You must have the additional voltage to supply enough amps to reliably burn more than one igniter when you press that launch button.

Now you have to hook those alligator clips on (in your case) six different igniter ends (as opposed to two on a standard, single engine launch.) This is much easier to do with a 2 engine cluster, because you can "twist" ends of inginter wires together and use a single pair of alligator clips. Not so with three. Much more reliable if you use three pairs of alligator clips.

But how?

Check out the web store of our very own "flying_silverado" for a 3 engine (minimum, he sells four - and that'll work too) "clip whips."

https://www.thrustaero.com/pages/clips.htm

You clip the leads from your 12V launch controller to the "small end" of the clip whip, and hook up individual alligator clips to the individual igniter leads. Just make sure none of them are touching (thus causing a short!!!!!!!!)

 

[Fore Check]

I should add a few other things about clustering, without going into too much detail.

* Make sure that you select three igniters that at lease are visually identical. i.e. same amount of black pyrogen on the tip, similar gap on the nichrome wire, etc.

* Take a single sheet (square) of recovery wadding and rip it in half. Wad this up tightly into a small ball and mash it down into the top of each engine in your cluster (above the clay cap on the ejection charge end) before inserting the motors into the model for launch. This helps protect your model from mishaps.

* Only launch a cluster of your type with three exactly matched engines. If you use Estes or Quest engines, I'd use all three from the same pack. In other words, don't cluster 2 B6-4's with a single C6-3 in your case.


I'm sure there are other details I'm leaving out that someone will chime in and "fill in the blanks...."

 

[moocrew]

Thanks for all the help guys!
The rocket is near the priming stage.
I've cut and glued all the fins all there is left to do is make the chute and engine mounts, then the paint job. Ill be sure to post pics when I'm done.

Thanks again for all of your help.

 

[Hospital_Rocket]

If you want to get a good basis in cluster techniques, there is a good resource in guy name of JIMZ

Jump here and look thru the list of documents. There are two old estes publications on clustering down near the bottom of the list.

https://www.dars.org/jimz/pubs.htm

and by the way:

Only launch a cluster of your type with three exactly matched engines. If you use Estes or Quest engines, I'd use all three from the same pack. In other words, don't cluster 2 B6-4's with a single C6-3 in your case

That said, make absolutely positively sure there is nothing with a
-0 mixed in your cluster...Or you will learn a new term - ZIPPER!

Al

 

[wwattles]

Actually, you can mix your motors, but only as long as you:

1) have them symmetrically paired (like 2 B's straddling a single C in a line, or 2 D's and 2 E's in a checkerboard square)
2) make the shortest boost + delay be when you want the nose cone to come off. Rocsim can help with predicting optimal delays based upon mixed motor configurations.

WW