Balancing Rocket Sticks - Necessary?

[Guest PyroManiac1]

I have started making my first two rockets. 3/4" ID and 4" Long with a cohete style report. I am using a sugar fuel with 65% KNo3 35% Sugar as well as a "Ruby Red Rocket Fuel" recipe supplied by Skylighter. Do I need to balance my sticks? Or can I use some BBQ skewers. How would I go about balancing them?

[pyrokid]

The purpose of the stick is to provide stability to the rocket during flight. As the rocket flies through the air, the air exerts forces on the rocket stick. If certain dimensional conditions are met, these forces act to keep the rocket pointed toward the sky. I've flown plenty of 1 lb. (0.75" ID x 7.5" length) rockets with rocket sticks 0.25" on a side and ~36" in length. There is some latitude for stick dimensions that will give a good flight but I would say that the bbq skewers that I'm familiar with are probably too small for the motor that you're describing.

[Guest PyroManiac1]

I also have some small dowels 3/16 ID and 12" long. Would those help?

[Guest PyroManiac1]

Also where would I attach the stick? Half way down the rocket motor or...?

[pyrokid]

12" seems a little short. Square dowels are preferred over round ones because they add more stability per unit length. See attached images for a better explanation.

[Arthur]

The aim of the stick is that the rocket files in a direction, without a stick rockets fly randomly, making any header very scary.

 

My few musings on sticks; Square in section, wood, glued to the rocket motor securely, balanced so that the initial CofG is just behind the rocket nozzle.

 

BBQ skewers can be too thin and bend with heat near the flame

[Mumbles]

I moved this to the rocketry section to help keep things organized.

[Guest PyroManiac1]

Due to heavy quarantine and semi martial law where I am, I can't really go out to the hardware store to get any supplies. I will have to improvise, maybe securely glueing and taping two dowels together to make a 24" stick. This rocket motor and heading is 2 ounces. If weight is the problem, I could also weight the ends of the sticks with ball bearings. Thoughts?

[Arthur]

If covid19 avoidance is possible, then avoid it! There will be time after covid for playing fireworks.

 

There used to be old books with pics of short stick rockets with paper fins attached -like a model rocket. Maybe you could try and make some guesses, but having two, three or four fins must make the launcher less easy.

[Guest PyroManiac1]

This hobby is one of the best I have and I am not willing to give it up due to Covid-19.

 

I drilled small holes in the ends of my twelve inch dowels and inserted another small connecting dowel secured with wood glue and then finished by electrical taping the seam. Its all one solid 24" stick now. Hopefully this will allow the rocket to get at least 40 feet in the air before it starts to change course dramatically.

[memo]

i have lots of bamboo . would that work ? in the past did't the chinos use that

[Jimjimboom]

I have used bamboo sucsessfully

[memo]

jim boom , what would you use on a 1 lb black powder core burner, 1 yard in length ? building my first ever rocket soon. your input would be great

Edited April 7, 2020 by memo

[Bigmark]

I'll add I have used the bamboo vegetable stakes with good results. 3/8"od by 36" long just balance the rocket and hot glue. You will more than likely have to trim a little off the stick. But they will work.

[nordicwolf]

I am confused by verbal descriptions of how to stick-balance motors (except for dag's comment about not balancing them at all!) Some suggest to balance "ahead" of the nozzle which to me seems to imply the balance point is on the motor itself. Others suggest the CG balance point is "behind" the nozzle which I take to mean balanced on the stick itself behind the motor exhaust.

 

(I also read that the CP of a stick-rocket will be pretty much at the nozzle exit

 

For clarity I created a quick picture asking where to balance the rocket (sorry dag! I am still learning and have to be careful about where and how often I can test fly anything).

 

Location "1" balanced on the motor itself, or

Location "2" balanced on the stick itself just behind the motor

 

My first flights will be without headers, simply a 1/2"ID x 5" motor with 75:15:10 BP (ball milled with ERC), all BP, no delay or ejection charge in the first two motors I pressed.

---- 4g clay nozzle

---- 21g BP

---- 2.7g clay plug

---- 13.4g tube (1/2"ID x 5")

total motor weight 41g.

 

Does the balance point change when I add a header? What I mean is, the header will add mass and change the CG, so adding stick length (or another stick) will be needed to get the balance point moved back from the top end of the motor.

 

But will it still need to be balanced at point "1" or point "2"? (I hope it is the same point with or without header.)

 

And also, where about on the attached diagram is the CP?

Thank you!

Edited February 7, 2022 by nordicwolf

[Bourbon]

This is a subject that's been tackled many o' times. One thing I can tell you is, don't let it drive you crazy. Keep it simple as possible when flying stick rockets. Save the technical stuff for your rocket kits.

 

Balancing your motors right at the nozzle is a good place, when flying without header. When you add a header, and the header increases in size and weight, you'll want to balance further up the motor... A good heavy header, I've even balanced them "right behind," the header, with perfect success. I do this because I don't want to add more stick. Keeps the weight down. I only fly pounders - 7 1/2" and short pounders 3.75". I use 3/16"-1/4" x 34" - 36" sticks. 1/4" x 36" seems to be ideal, for allot of folks working with 1/2" - 1" motors. A good hot motor, with a big bulky header, some folks will run 2 sticks 180 from each other.

 

Your trying to fly a round mallet here. Nothing like a sleek, aerodynamic rocket. I wouldn't worry about finding the CP. Just keep the CG up on the motor, with a header. A couple pro stick rocket builders have said, they don't balance anything. They just have a preferred stick they use per size of rocket. They don't trim anything. They throw it on and fly it. I tested this with mine. Seems I can just throw a 36"r on there, no balance and she fly's great. However, I did the balance game till I found the stick that covers what I do.

 

Now that Ive rambled on... Most likely no help at all for ya. There's some smart guys on here that can explain to ya, with more technical verbage then I.

[nordicwolf]

Thanks for that, Bourbon. Hmm, I wish I were saying thanks FOR the bourbon, but I digress.

 

I found some 30" skewers from walmart that are about 3/16" diameter that I intend to try. I have some 1/4" square rods as a backup. I really hope the 3/16" skewer works for the 4oz motors as they are cheap and easy to get. Whatever, I want to get to something I can just set and forget.

 

Without any header, I will try it as I currently have it at position "1" just up on the end of the motor.

 

I have 1 pound tooling as well but core burner for 7.5" and 3.75" I hope my 75:15:10 ERC milled BP is not too hot for those and does not CATO. I press to about 9000psi. (I also have some 3.75" stinger tooling I want to try. no balancing those :-))

 

I have read many discussions here and elsewhere, but I had trouble visualizing the balance point, so I posted the picture above for clarity.

 

Thanks for the reply!

[Richtee]

Thanks for that, Bourbon. Hmm, I wish I were saying thanks FOR the bourbon, but I digress.

 

Now now young wolf... careful what ya wish for. Sticks are fine but DO pay attention to balance. Lockheed and many others do. There’s a reason. And DO film (Ah fuck did I say film?) a few.

[Bourbon]

Lockheed stick rockets. Wouldn't that be something?

 

 

nordicwolf (I also have some 3.75" stinger tooling I want to try. no balancing those :-))

 

 

Build one of the stingers you have, just don't drill the tangential hole. Throw a stick on it and fuse it at the bottom with a j hook... I do it all the time! They fly wonderful, kid you not... Fantastic shorty! They hall nice pay weight for a tiny bugger. I use 65/25/10 in mine.

 

I should have said up top, yes, balance close to position 1(without header). That will make up for weight loss as the fuel grain burns. Visualizing becomes easier after it's built, stick and all. Do thee ole finger test. You'll know right away if that stick is too short, or, simply not heavy enough. Too flimsy can be just as much a problem. May get a death wobble..

 

Edited February 8, 2022 by Bourbon

[nordicwolf]

I am waiting on some stinger tubes from PyroDirect - then I will build some and try the 3/16" dia skewers. They seem stiff enough but as a first-timer I have nothing to go by. Maybe they are too flimsy - I hope to find out soon.

 

65-25-10 - I will mix some up. What charcoal do you use? I have eastern red cedar from pet bedding also from walmart. Hmmm. skewers, cedar, I wonder what else walmart can do to support my vices...

 

Thanks again!

[SharkWhisperer]

Thanks for that, Bourbon. Hmm, I wish I were saying thanks FOR the bourbon, but I digress.

 

I found some 30" skewers from walmart that are about 3/16" diameter that I intend to try. I have some 1/4" square rods as a backup. I really hope the 3/16" skewer works for the 4oz motors as they are cheap and easy to get. Whatever, I want to get to something I can just set and forget.

 

Without any header, I will try it as I currently have it at position "1" just up on the end of the motor.

 

I have 1 pound tooling as well but core burner for 7.5" and 3.75" I hope my 75:15:10 ERC milled BP is not too hot for those and does not CATO. I press to about 9000psi. (I also have some 3.75" stinger tooling I want to try. no balancing those :-))

 

I have read many discussions here and elsewhere, but I had trouble visualizing the balance point, so I posted the picture above for clarity.

 

Thanks for the reply!

Wolf, I know those Wallyworld skewer sticks and they're probably going to be on the light side, like way way light side. Guessing you're talking about the Ozark Trail skewers (little under 3' long) skinny round jobs. 10-12/pack for about a buck. Price is a fooler. They're skinny, lightweight, and super bendy. Try 'em but don't be surprised if you're disappointed. And please cut off the pointy end :>} Even the cheap Chicom sticks that come on small 1.4G rockets are better, and the Chicom's cut every corner they can possibly think of.

 

Edit: Modified confusing description of skewer length.

Edited February 9, 2022 by SharkWhisperer

[Arthur]

If rocket sticks didn't matter the Chinese factories wouldn't supply them. They do matter and need to be an appropriate size. There seems to be an optimum size for a stick depending on the size mass and CG of the load. Also they need to stay straight and strong right by the hot flame.

CplMac2 (formerly of this parish) has a nice shell on YT v=5g9uCcY7tFg

The stick would do a realtor's notice proud.

[dagabu]

Sorry for replying to an old thread but after running the rocket line for 2 years now and seeing what makes a rocket fly and what hurts performance as well as witnessing thousands of "traditional" sticked rockets, I think there is abundant proof that balancing a rocket on the stick (especially one without a shell/heading, hurts performance and robs height.

 

Allow me to walk you through the "problem rockets" we had this year and lets talk about what was done (with the makers permission) to get them to perform well.

 

The first is the sali-boosted strobe rockets we saw plenty of. Several of them took a sharp turn upon launch and several others cork-screwed during the coast phase.

 

The sharp turn at launch is due to torque, not the stick thickness or length. A builder (Mike) made several strobes (his first ones) and allowed me to coach him on what sticks will do when the instant thrust kicks the motor "into" the stick as the mass of the stick reacts to inertia and pulls against the motor. This causes the stick to bend, sometimes severely up to tearing it off the motor or even breaking if the wood grain crosses the stick length.

 

We launched the first using a traditional single stick he attached with hot glue. It pitched and changed the trajectory to fly toward the B-line. Mike thought it was a good flight but I saw that it lost a lot of its energy to the pitch and horizontal flight instead of using that thrust to climb high into the sky. I asked him if I could modify the second rocket and he was exited at the prospect of a straight up flight so I cut his 40" stick in half and attached the other half to the motor 180° from the first stick. This rocket launched straight, it climbed a couple thousand feet and the salute went off at apogee. It was a supreme example of a strobe flight!

 

We went about changing sticks and lengths as well as thicknesses to demonstrate flight changes due to stick modification alone. We were favored with 15-20 MPH winds in the early evening so we could see the flight as well as the stick position in the wind. This became the highlight of the evening when we used a four foot long single stick on another of his motors. While we were loading the rocket, an old-snort offered to tip the rack so we could "Fire into the wind and direct the rocket." . I told him that I would be happy to let him launch one of his rockets into the corn field but we would keep the racks straight up for this launch. The rocket came off the rack pretty straight and then used all of its coast to steer into the wind and gain very little altitude before healing over and dropping back to the road just 50' behind the racks.

 

Mike scratched his head, he didn't understand why the second rocket went up 2000' and popped at apogee and this one round-tripped? Watching the flight, the stick pitched about 40° into the wind and just hung there! A near perfect representation of what I was hoping to see. Mike swore that he had been told time and time again by the "greats" in rocketry that he MUST balance his rockets to get them to fly "straight". I asked to trim another of his sticks and demonstrated that we could cut the stick very short as still match the CG but not the pre-launch CG. Hmmm? Picking up his spent rocket stick (tube was blown off) I taped an empty tube of approximate size to the used stick and had to cut the stick back almost 2/3 to get the motor/stick to balance at the intersection.

 

I then trimmed this new stick to that same 1/3 length and cut a short piece for the other side and he launched it in the same wind, in the same rack in the same position. It did not steer into the wind appreciably and reached about the same 2000' the second rocket reached. WHY!?!? The shorter stick allows for much less mass and much less drag so it can move through the acceleration phase much faster with little stick deflection or torque applied to the stick.

 

I also spoke at great length with an old timer who is also some kind of aeronautical engineer that was launching all sorts of teeny-tiny rockets that used absurdly short sticks yet flew straight as an arrow!

 

Next up: Rockets with shells.

 

I am confused by verbal descriptions of how to stick-balance motors (except for dag's comment about not balancing them at all!) Some suggest to balance "ahead" of the nozzle which to me seems to imply the balance point is on the motor itself. Others suggest the CG balance point is "behind" the nozzle which I take to mean balanced on the stick itself behind the motor exhaust.

 

(I also read that the CP of a stick-rocket will be pretty much at the nozzle exit

 

For clarity I created a quick picture asking where to balance the rocket (sorry dag! I am still learning and have to be careful about where and how often I can test fly anything).

 

Location "1" balanced on the motor itself, or

Location "2" balanced on the stick itself just behind the motor

 

My first flights will be without headers, simply a 1/2"ID x 5" motor with 75:15:10 BP (ball milled with ERC), all BP, no delay or ejection charge in the first two motors I pressed.

---- 4g clay nozzle

---- 21g BP

---- 2.7g clay plug

---- 13.4g tube (1/2"ID x 5")

total motor weight 41g.

 

Does the balance point change when I add a header? What I mean is, the header will add mass and change the CG, so adding stick length (or another stick) will be needed to get the balance point moved back from the top end of the motor.

 

But will it still need to be balanced at point "1" or point "2"? (I hope it is the same point with or without header.)

 

And also, where about on the attached diagram is the CP?

 

Thank you!

[nordicwolf]

Thanks so much for the info. I hope to go to a launch and learn from someone like you, first hand. In the meantime your details I will consume eagerly. Thanks again for all the great help!

[cmjlab]

Dave,

 

Can you clarify how you ARE determining the stick length?

 

I don't have a lot of experience with rockets, but of the rockets I have launched (B.P. and Whistle all 3/4" ID) Ive never balanced anything. I just used two sticks approximately 20" long (~3/8" x 1/4") and they launch relatively straight.

 

So I'm curious if it's a certain # relative to tube length, if there is some formula, or if it's just based on experience to determine what length sticks will work best?

 

Thanks. I apologize if you answered my question in your post and I just didn't understand).

 

Charles

 

*Edit* I haven't tried any headers on them either, so I'm not sure what effect that would have on length either.

Edited August 22, 2022 by cmjlab