Newbie questions

One more (how many one mores!?) while im at it...

Background first: there are multistage rockets where the preceeding stages burning up igniting the next and it falls off and contiunues (if you want). Also, on spent motors it is completly empty hollow except for the pinch at the end where the gasses compress. Great, but what if....

I wanted to make a long tube and stick 2-3 motors into it, but i dont want the motors to fall off? Will there still be enough thrust (with a C6-5/3/0) to keep the rocket up to speed after it burns through its own nozzle and also the one that burned before it?That was confusing wasnt it...i know. I looked through the forums/what not (or i think i did) and didnt find anything about this.

Now for something beyond my skill: Is it possible to launch a rocket very slow so its actually possible to take a picture of it before it dissapears!? The best pics i got of my RTF (so i had to glue fins on...oo) rockets are of just before it ignites and just when it leaves the screen! It would be kindof nice to see it slowly lift off.

Here's a couple of links to clubs in your area. Both of them have upcoming launches. I highly recommend attending a club launch. You'll see some cool stuff.

https://www.blackholerocketry.com/

https://www.northwestrocketry.com/

Here is my rocket i said i would post...it is my second rocket ive made, the first was moreover a flying piece of paper. Just incase you were wondering.

Pretty nice looking.

If it is a two stage, stability may be an issue with those small fins, but that if a very good effort for a second rocket, scratch built to boot.

I wanted to make a long tube and stick 2-3 motors into it, but i dont want the motors to fall off? Will there still be enough thrust (with a C6-5/3/0) to keep the rocket up to speed after it burns through its own nozzle and also the one that burned before it?That was confusing wasnt it...i know.

Click to expand...

The initial thrust of the successive motors would almost certainly dislodge the ones below it. If you bound them together tightly, the dangerous probability is that the staging would blow a gap between the motors, redirect the thrust into the body tube, and create a flaming projectile. The far easier and safer method is to have the lower stages fall away (just like NASA staged rockets.)

Now for something beyond my skill: Is it possible to launch a rocket very slow so its actually possible to take a picture of it before it dissapears!? The best pics i got of my RTF (so i had to glue fins on...oo) rockets are of just before it ignites and just when it leaves the screen! It would be kindof nice to see it slowly lift off.

Click to expand...

It takes practice, a good shutter speed, and a little luck to get good pictures. A second person doesn't hurt either. Larger rockets are a little easier to capture. A rocket has to leave the pad fast enough to be stable. With small models, this turns out to be pretty darn fast. Remember, NASA rockets leave the pad at a a pretty good clip too. They are simply far bigger, photographed from miles away.

Originally posted by noahnott

One last question, where the first and second stages connect, is it supposed to be a tight fit, loose fit, medium tight, barely hanging in there...im lost on that part. How do i know if its right?

Thanks for helping
-Noah

Click to expand...

It needs to be a loose fit, but not so the weight of the booster causes it to fall off if you hold the rocket by the upper stage.

If it is too tight here is what happens: The lower stage burns thru and ignites the upper stage. The lower stage stays stuck and the flame from the upper stage burns up the bottom stage.

At a recent launch, a friend launched an Estes 3 stage rocket.
The bottom stage worked perfectly, but we never saw the second stage fall. The third stage worked perfectly, the parachute popped out on time and it recovered nicely.
The second stage was still stuck to the bottom and the body tube was burned away down most of one side between the fins.

This also answers one of your other questions. It does not work to light a motor above and run the exhaust thru the empty motor casing below.

I found this book to be just filled with info and ideas for model rockets. https://www.apogeerockets.com/design_book.asp

This website is filled with good information. check it out!
https://www.apogeerockets.com/education/index.asp

Originally posted by jflis
Pretty nice looking.

If it is a two stage, stability may be an issue with those small fins, but that if a very good effort for a second rocket, scratch built to boot.

Click to expand...

Um, your probably most likely right (because the fins do look a little tiny). But i used this free sim and it says it will be stable (with like the CP 1.5 in or so behind the CG) IF i add ballast in the nose cone (like a battery but i think thats illegal to use). Anyways, is this a reliable sim for just simple rockets knowing if there stable?

-Noah

I think it will probably need noseweight to fly properly. I use rocksim, and have never tried the one you link to, but since it's from Nasa, my bet is that it's fairly decent.

As far as nose weight goes, you don't really need to stick a battery in there. There are a plethora of objects that are heavy and can fit in that space, and you don't have to worry about acids and stuff. But the best thing to do is to take some lead shot, like fishing weights, and stick em in the nose and then cover it all with glue. I've done it with white glue on smaller models-if you want to use epoxy be careful because it can get hot and could melt the plastic of the nose. You could stick it in some ice water.

Jesse

My only prob is that my homemade nose cone is solid wood. I guess i could drill a large hole into it and stuff it with lead. I use 5 min epoxy on everything =D

Thanks again, Noah

Originally posted by noahnott
My only prob is that my homemade nose cone is solid wood. I guess i could drill a large hole into it and stuff it with lead. I use 5 min epoxy on everything =D

Thanks again, Noah

Click to expand...

That what I would suggest. That one of the ways that I added weight to my sons Pinewood derby car. Just drill a hole or holes depending on how much weight you need and drop in fishing wights and cover them with glue. White or yellow gule should work fine.

Sounds good.

On a diff subject which i asked at the beggining of this thread, about not using fins. Somebody posted their finless rocket which i liked, but i can make finless rockets (and stable) by just adding a fair amount of ballast in the nose?

Also, for drop off booster rockets I can just let them "tumble" on their way down with no fins? No streamer required?

If the boosters are small enough, then they can tumble. You may have some trouble seeing them, and a streamer would help with that, but they should be light enough to not cause any harm.

There are a lot of different types of rockets, some of which don't use/need fins, per se. Check out https://www.artapplewhite.com/ for some neat cone, saucer, and other really weird designs.
You may also want to try ring fins. Those look neat and work well.

but i can make finless rockets (and stable) by just adding a fair amount of ballast in the nose?

Click to expand...

Sure you can, just look at a bottle rocket - long stick with alot of weight up top..

stable- yes
predictable flight path-no

Alright, thanks yet again.

The booster rockets falling off is a little too tricky for me (but i know how its done) so i just might skip the part where they fall off. Ill see what i can do.

*edit* Something else just dawned upon me...the fact that this rocket im making is a little heavy (but still legal) for 1 C6-5 motor. One other question: So i launch my finless rocket which is pretty heavy, and it doesnt have a lot of speed when it leaves the launch pad. So um, since its finless whats keeping it stable, and will it still be stable when its flying slow, as in really slow? The rocket weighs...when compared to a can of beans (450g) it feels a little lighter when i put the motor [c6-5] on it)

also the NAR code says "If my model rocket weighs more than one pound (453 grams) at liftoff or has more than four ounces (113 grams) of propellant, I will check and comply with Federal Aviation Administration regulations before flying. " So, basically pretend your rocket is a plane?

-Noah

The booster can just be attached to the sustainer with a coupler. When the upper motor lights, the pressures in that little space will blow away the booster.

About the booster thing i meant them being on the outside like a cluster rocket.

Try reading through this thread.
Are you talking about having the motors in their own length of body tube, with a nose cone that can pop off? In that case, a simple way to keep it on during flight and have the whole booster come off after ejection (like the space shuttle's SF boosters) is to rig something up with straws and dowels.

Well that thread answered my booster question. But yah, heres a picture of what i wanna do. Is there a better way to paint the paper part where I sanded it (it just soaks up the paint). About the booster motors things, ill try to buy some pvc pipe so it looks better than the lopsided paper.

Gotta eat,
Noah

If you Google "vcp" and down load it you'll find it's an easy to use way to design rockets.

vcp has helped me immeasureably over the years which is a great thing for freeware.

Also, the programmer is a member of this forum.

Great program, im just not used to it yet.

But, before i punch in my rocket into the program, maybe somebody knows from experience...

If i launch my 500g rocket which only uses a single C6-5 motor, will it be stable after it leaves my 3ft launch rod moving along pretty slow? Its finless and their is a lot of ballast in the nose. Ne1 know so i can put it in the program or ajust my model so it will be stable? If it is stable even when moving slow....that means i could actually take a pic of it! lol

Thanks but yet again, and again,
Noah

No, it will not be stable. Finless is a problem right there - it will have next to no corrective force to prevent it from deviating from a straight trajectory. Second, 500g is so much that I would not trust it on a D12 - that is into the E30 territory. A C6 is asking for disaster (and a C6-5 will eject the chute underground). For most of its burn, a C6 does not even produce the 5N of thrust needed to exactly offset the weight of a 500g rocket, much less lift it off the ground.

Even ignoring the issue of the finless rocket, a 500g rocket on a C6-5 would reach a peak altitude of about 4 feet according to rocksim, and be doing 1.8mph at launch rod departure. That is not at all safe. Ejection would happen about 4.8 seconds after impact. A rocket that is in the 300g range will take off fairly slowly on a D12, and one in the 150-175g range will take off at a leisurely pace on a C6 (but use a C6-3: a 5 would be FAR too short).

That doesnt help me =(

im wondering if im right about the weight...hm, my rocket a little lighter than a can of beans? How did it become so heavy, maybe my left hand is stronger than my right..

*edit* Maybe i should buy a scale, but actually i compared again..this time to a can of peaches (425g)...the rocket felt just about 3/5 its weight...So actually its not 500g. But still.

What kind of tubing are you using in your construction? It appears pretty thick and heavy.
You can mailorder thinner tubing more suitable for rockets, then you can use lower power engines. You can build a pretty big rocket that will fly nicely on C engines.
The finless design is a challenge, trying to keep the CG/CP relationship "correct". I have an old design in my fleet that has a cone at the base of a long slim body, which replaces the fins. Even so, it can be wobbly in certain conditions. Nothing aside from active guidance will replace fins and airspeed for off-the-rod stable flight. (well, there ARE spool rockets, and other "oddrocs", but I wouldn't know where to start there...). Tubefins are very effective as well, something I plan on experimenting with one day.

Whatever your plans, I agree you would do well to find a local club to join if at all possible, there is a wealth of knowledge and experience there. Nothing wrong with thinking outside the box, as long as you have some idea of what's out there.

Be safe...
Dave

Yes the tube im using is fairly heavy pvc pipe about 1/16in thick. I could always resort to paper towel tubes =D just coat some epoxy on it and make it heavier than a brick

The reason i dont want to buy a body from fliskits or something is b/c its made by somebody for rockets (i prefer things made for something but not rockets). My rules are homedepot/officemax, my garage, and the motors from anywhere.

Back to the finless stuff...it wouldent work to point 2 small motors to spin the rocket before it gets off the launch rod, would it? Does rocksim take into account gyroscopic forces (or whatever its called).

*edit* If only the Co2 thing would work and was legal....fills up a balloon in mid air too!

Sry if im annoying you ppl with questions,
Noah

Heavy rockets.... yeah, my first scratch-built rockets used to be really heavy, too.

Well, I would begin by ditching the epoxy and using only yellow glue. Next, I would begin downloading plans of paper rockets as a means of studying how simple it is to construct a good looking rocket from very light, but strong materials.

Clive

So the weight issue, ill get rid of the pvc pipe and the epoxy but what is a good weight for a rocket using C-6's or A's and B's for that matter?

What can i say, im filled with questions, and if there is somewhere i can find more info (webpages [already looked at apogee's info and a bunch of other webpages] [ill stop by the library sooner than later]) let me know so ill stop bothering you as much.

Noah

Rocketry Online has a resource page that lists all the maximum suggested weights for each motor. I check this site often when I am developing a rather unusual bird.

https://www.info-central.org/index.cgi?propulsion

Clive

The heaviest I would feel comfortable with a C6 is about 4oz (113g). Same goes for a B6 (similar liftoff thrust capabilities). This will liftoff reasonably slow, and attain perhaps 300 feet on a C6 and 130 on a B6 (use a C6-3 and a B6-2).

So at least i know im way below the limit for weight. But um, what is the weight that would PROBABLY give me the best hight. And do those limits include the motor or just the rocket? Just wondering, b/c the paper rocket (covered in 2 layers of fiberglass resin, relativly light compared to the pvc and strong, about 20g for the fusalage) im making, im estimating to be a maximum of 75 grams with the motor included.

Btw, im basically limited to C6-5's and A10's (or something like that)...cant find any stores that sell motors other than "that place"

This is a fun hobby so far,
Noah