All10Fingers Posted July 22 Share Posted July 22 Every time I make a rocket, I use the exact same process. However my results are all over the place. Some cato, some zip and zag around, some don't leave the ground, some make big arches and end up back on the ground, and some fly perfectly straight up the whole way. I know the stick could probably be a little bigger. But I have thousands of these BBQ skewers. Any thoughts ideas, critiques, advice or praise would be a great help as the fire danger in my area is very high this time of year. Oh yes, it's BP, with a little carbonate and titanium mixed in the delay. Half inch inner diameter no nozzle. Packed on a skylighter spindle with a hammer. Link to comment Share on other sites More sharing options...
greenlight Posted July 22 Share Posted July 22 (edited) I used to use bamboo skewers for small black powder rockets when I was younger and experienced the same problems. I believe it is due to the small bamboo stick not being long enough or having enough mass to properly balance the motor. The stick should be long enough with enough mass to balance the thrust produced. Definitely try a thicker larger stick. Then they will fly straight and more consistently. You can find and fine tune this region when the rocket will balance on your finger level at the point illustrated by the parabola in the photo below: Edited July 22 by greenlight Link to comment Share on other sites More sharing options...
All10Fingers Posted July 22 Author Share Posted July 22 Seems like that stick would have to be huge to balance out with the whole rocket. So I just shot the one in the picture.... It cato'd. But the one I fired off in the 4th burned the right off. The sticks aren't perfectly straight either. And eye glue em on as straight as I can. But I have bad eyesight and a shaky hand so there not really perfect. Link to comment Share on other sites More sharing options...
greenlight Posted July 22 Share Posted July 22 It would be huge if you use a very thin low- mass stick like the bamboo. Most rockets use a wooden dowel rod as the stick which is thicker and heavier so does not require insane lengths to balance out. It will still be long compared to the motor length but in terms of physics, as the mass of the stick moves further away from the point of origin near the engine, its opposing (counterbalancing) force fue to gravity increases with distance. This is why it is more difficult and more force is felt to hold up a large rod from one single end in your hand versus holding it in the middle. Link to comment Share on other sites More sharing options...
Almostparadise Posted July 22 Share Posted July 22 If they are on the short side, try using two sticks. One across from the other. Link to comment Share on other sites More sharing options...
Zumber Posted July 22 Share Posted July 22 2 hours ago, All10Fingers said: Seems like that stick would have to be huge to balance out with the whole rocket. So I just shot the one in the picture.... It cato'd. But the one I fired off in the 4th burned the right off. The sticks aren't perfectly straight either. And eye glue em on as straight as I can. But I have bad eyesight and a shaky hand so there not really perfect. Stabilizer stick or balance stick shall be straight, smooth ,unbroken and uncracked throught its entire length And its height shall be atleast 5.5 times of height of motor/shell etc. Also if you stick conical shape kraft paper cone at top head of rocket (not for payload type rocket) it reduces wind resistance during its flight. And If you keep 20 percent empty space at nozzle side of tube this space acts as a propulsion chember and aid rocket to fly straight. Link to comment Share on other sites More sharing options...
ThrownBiscuit Posted July 22 Share Posted July 22 I think maybe with the difference between a CATO and not wanting to launch with the same technique utilized, could it be differences between batches of BP? I know I've had similar problems with some of my rockets until I started consolidating batches together to get a more uniform product. Link to comment Share on other sites More sharing options...
All10Fingers Posted July 23 Author Share Posted July 23 So, are you telling me it's all about the weight of the stick that stabilzes the rocket? I've been looking at it in terms of wind resistance. Like the fletching on an arrow. The feathers cause drag towards the back which keeps it pointing straight ahead. I'm concerned too much stick will severely impede the flight. Maybe I'll switch from kabab skewers to rotisserie skewers.... or try the 2 stick thing, cause I really do already have a bunch. Link to comment Share on other sites More sharing options...
Guernica Posted July 23 Share Posted July 23 If you describe your build process in detail, it might help to identify where things are going wrong. Are you waxing your tubes? What's the size of each increment you load? Are you dampening your fuel? How confident are you you're pounding each increment with consistent pressure? Obviously pressing instead of ramming makes it easier to keep track of loading pressure, but it's possible to hand-ram your way to success at the 1/2" ID size with which you're working- it does take a certain feel with the hammer, though. Did you ever get that dead blow hammer? Those overly tiny sticks you're using are certainly no good for consistent flights, but aren't the cause of your CATOs (you definitely need to step up your stick game though too, it doesn't matter if you have a million bbq skewers, it doesn't mean you should use them for this size rocket, save them for your 1/4" tooling). Without knowing more about your process, I'd guess your problem has more to do with poorly consolidated & inconsistent increments than anything else... Link to comment Share on other sites More sharing options...
greenlight Posted July 23 Share Posted July 23 52 minutes ago, All10Fingers said: So, are you telling me it's all about the weight of the stick that stabilzes the rocket? I've been looking at it in terms of wind resistance. Like the fletching on an arrow. The feathers cause drag towards the back which keeps it pointing straight ahead. I'm concerned too much stick will severely impede the flight. Maybe I'll switch from kabab skewers to rotisserie skewers.... or try the 2 stick thing, cause I really do already have a bunch. Yes the stick makes a big difference in stabilisation and flight if your motor is dialled in. An arrow shot from a bow is only accelerated while it is contact with the bowstring. The moment it leaves the bow string, it is no longer accelerating, and the only force on it is gravity in the downward direction (projectile motion). The arrow has a velocity still but no acceleration so having an aerodynamically shaped projectile in this case increases range and accuracy. A rocket motor has an exhaust of high velocity gases which provide acceleration (thrust) through the flight until the fuel is consumed. This constant acceleration makes it a bit more difficult to stabilize. The stick provides both aerodynamic stability as a sort of tail and also a trailing mass which moves the centre of mass of the rocket resulting in stable, straight flight. The stick also keeps the centre of pressure behind the centre of mass during flight. 1 Link to comment Share on other sites More sharing options...
cmjlab Posted August 12 Share Posted August 12 I'm no rocket expert, but for the inconsistent flight issue, I'd try the 2nd stick first - it's a quick simple method to possibly help provide a little more stability in flight. I also agree that it won't help with the CATO issue though. Good luck. Link to comment Share on other sites More sharing options...
All10Fingers Posted August 12 Author Share Posted August 12 Cool, I think Ive solved the catos. Bought a couple 1\2 inch roll pin punches. These are way better than the stupid aluminum crap skylighter sent me. And for less than half the price. They fit snug inside tube and are made for pushing holes through metal with a hydraulic press, so one can hammer on one all day with no worries. No more cracks, gaps, soft stops, or bubbles. As far as sticks go.. .I've made improvements. But a new issue is the stick catching fire during flight and curling. It Makes the rocket do a fun little spin dance. Still looks cool, buy not what I was going for. Probably can be solved with better quality sticks. In conclusion, the problem was that im a cheapskate I guess Link to comment Share on other sites More sharing options...
Almostparadise Posted August 13 Share Posted August 13 3 hours ago, All10Fingers said: Cool, I think Ive solved the catos. Bought a couple 1\2 inch roll pin punches. These are way better than the stupid aluminum crap skylighter sent me. And for less than half the price. They fit snug inside tube and are made for pushing holes through metal with a hydraulic press, so one can hammer on one all day with no worries. No more cracks, gaps, soft stops, or bubbles. As far as sticks go.. .I've made improvements. But a new issue is the stick catching fire during flight and curling. It Makes the rocket do a fun little spin dance. Still looks cool, buy not what I was going for. Probably can be solved with better quality sticks. In conclusion, the problem was that im a cheapskate I guess Popular is a good choice for sticks. It wont catch fire as easily. Its cheap for a couple short peices which will go a long way. Until then, there's always foil tape if u just need a quick pyro fix w out it raining burning sticks.😏 Link to comment Share on other sites More sharing options...
All10Fingers Posted August 13 Author Share Posted August 13 You know, I hadn't considered just using actual sticks... There's lots of poplars in my area and I know a spot with a dense thicket of basket willow. Both grow relatively straight and narrow. I could probably just cut and trim something like making tiny arrows. Somewhat inconvenient but free and practically unlimited. With infinite options for size Link to comment Share on other sites More sharing options...
cmjlab Posted August 15 Share Posted August 15 What improvements did you make to the stick to get them to fly better? Link to comment Share on other sites More sharing options...
All10Fingers Posted August 16 Author Share Posted August 16 For one, taking better care to make sure I glue them on straight. Aside from that, I speculate that maybe the slightly better consolation from the new rammers gave me a tiny bit more thrust to help keep itself pointed forward. Although this isn't much data to work with as I've only made one since I started this post so it could still all be random luck. But I'd like to think my efforts have some influence on the results. Seems silly but the very first one I ever made was by far the best I've ever made. It was all BP, no delay mix, nozzle, or any sort of measuring at all. But that one flew straight up like it was on a wire. And it went high enough for there to be a noticable pause between when you see and when you can hear the burst. Since then I've made good and bad ones. But never have been so perfect as prototype 1.0. Maybe it was just a particularly good batch of BP. Or even charcoal 1 Link to comment Share on other sites More sharing options...
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