LTUPyro Posted January 24, 2013 Posted January 24, 2013 Hi,I have tested 10 bp rockets today and I have some stabilisation problems. Only 3 of 10 went straight in the air. Other 7 went kinda straight, but then somehow it change course and very fast goes to ground. Stick I use is 10 longer than motor. Maybe I need to use some weight on stick? Please help cause I need to make 25 rockets in 4 days for little show.\Sorry for bad english :/
bob Posted January 24, 2013 Posted January 24, 2013 I"m not very good with rockets but what I do is I put a stick on the rocket, then I put my finger behind the nozzel of the rocket and see if it stays level, if it does then I use it that way. If the rocket goes down then I know I need a longer stick, if the opposite end goes down (the end farthest away from the rocket) then I cut a little bite off of the stick.but like I said I"m far from being a pro at rocketsbob
dan999ification Posted January 24, 2013 Posted January 24, 2013 balancing is not always enough to guarantee straight flights. what id were the rockets, core burner, endburner, round stick, square stick? Stick od/ width of sides, was it windy?There are some tables and general rules of thumb.A little more info would help get you a straight answer. Dan.
Col Posted January 25, 2013 Posted January 25, 2013 If the stick is 10x the motor length it`s probably too long. I wouldnt worry too much about balance unless its a slow rising rocket.
nater Posted January 25, 2013 Posted January 25, 2013 (edited) Are the sticks breaking? Are the rockets turning so they start to fly into the wind? Are the motors too weak? Is the delay too long? Do you have video? ------ At the risk of sounding mean, and having worked out rocket issues of my own, you should not be planning a show with them until they are well dialed in and you get very reliable results. 4 days is not very much time to improve a 70% failure rate. Edited January 25, 2013 by nater
LTUPyro Posted January 25, 2013 Author Posted January 25, 2013 (edited) balancing is not always enough to guarantee straight flights. what id were the rockets, core burner, endburner, round stick, square stick? Stick od/ width of sides, was it windy?There are some tables and general rules of thumb.A little more info would help get you a straight answer. Dan. Rockets is 15mm ID, core burner. Stick is square 8mmx8mm. And no, here wasnt any wind. Are the sticks breaking? Are the rockets turning so they start to fly into the wind? Are the motors too weak? Is the delay too long? Do you have video? ------ At the risk of sounding mean, and having worked out rocket issues of my own, you should not be planning a show with them until they are well dialed in and you get very reliable results. 4 days is not very much time to improve a 70% failure rate. Are the sticks breaking? No Are the rockets turning so they start to fly into the wind? Nope Are the motors too weak? Well I guess these are kinda strong cause I have tried it with 200 g shell and it went really good and fast. I guess it can lift more than 200g. Is the delay too long? Nope, it's almost perfect Do you have video? Sadly no, but if I have more free time today Im gonna try some rockets and will catch it on camera. And yep, I guess I will just use shells 'cause I wont get any accidents. I just wanted rockets cause I need some huge titanium salutes for finale. Edited January 25, 2013 by LTUPyro
Mortartube Posted January 25, 2013 Posted January 25, 2013 (edited) If they lifted a 300g shell (and I assume that they went straight up), then I think that your sticks are too long. Did you use the same stick dimensions when you lifted the shell? Try as suggested. Get the rocket to balance by putting your finger just behind the nozzle. If when you do this, the motor end tips down, the stick is too short. If the end of the stick tips down, the stick is too long. When it balances try launching them again. Changing the stick length is the easiest thing to do first If they still don't work well after the balancing trick, we can eliminate things in steps to try to help. Oh and remember, the heavier the header, the longer the stick will need to be. A salute rocket will usually be lighter than a header full of stars. Edited January 25, 2013 by Mortartube
LTUPyro Posted January 25, 2013 Author Posted January 25, 2013 If they lifted a 300g shell (and I assume that they went straight up), then I think that your sticks are too long. Did you use the same stick dimensions when you lifted the shell? Try as suggested. Get the rocket to balance by putting your finger just behind the nozzle. If when you do this, the motor end tips down, the stick is too short. If the end of the stick tips down, the stick is too long. When it balances try launching them again. Changing the stick length is the easiest thing to do first If they still don't work well after the balancing trick, we can eliminate things in steps to try to help. Oh and remember, the heavier the header, the longer the stick will need to be. A salute rocket will usually be lighter than a header full of stars.Thanks! Gonna test it out as soon as I can.
nater Posted January 25, 2013 Posted January 25, 2013 (edited) Did your rockets have nozzles or are they nozzleless? If they had a nozzle, is there significant erosion on the ones that didn't fly right? Edited January 25, 2013 by nater
psyco_1322 Posted January 25, 2013 Posted January 25, 2013 (edited) First, videos and pics really help with solving issues, if you can get video, it makes solving the problem a lot easier. Otherwise we have to guess on some things and ask lots of questions. Your stick length for that size of motor should only be around 25" (64cm) ... given the motor length is 10 times the ID, you have a stick that's nearly twice as long as it needs to be. For my 4oz (1/2") motors, I use a stick around 22", for 1lb (3/4") motors, I use a 32" stick. If there is any wind, the rocket will turn into the wind shortly after take off and attempt to fly into the wind. Rockets hardly ever fly perfectly straight up, usually they will have a slight angle to the flight, but they should never turn around and fly towards the ground. Make sure you are getting the sticks attached straight, look down the motor and stick to make sure. A slanted stick can cause erratic flights. Also make sure you're stick is not able to wiggle around and move side to side. I attach my sticks with hot glue, and add a few wraps of tape around the stick and motor. Using only tape usually allows the stick to have a little wobble to it, make sure you glue them somehow. Edited January 25, 2013 by psyco_1322
Mia Posted January 25, 2013 Posted January 25, 2013 More to the point how are you attaching the stick? Balance the rocket at the point of mass you will get a shift of gravity after the kinetic energy has ceased.
LTUPyro Posted January 25, 2013 Author Posted January 25, 2013 Thanks you all guys for help. I just tested some rockets all went very good. I wanted to film it, but sadly I didnt pressed camera button .. I'm gonna make some smaller salute rockets and about 5 150 g salutes for my little show finale
Col Posted January 25, 2013 Posted January 25, 2013 You shouldnt need a stick longer than 3ft on a 15mm motor. Long sticks have more flex which could contribute to stability issues.
bob Posted January 27, 2013 Posted January 27, 2013 Thanks you all guys for help. I just tested some rockets all went very good. I wanted to film it, but sadly I didnt pressed camera button .. I'm gonna make some smaller salute rockets and about 5 150 g salutes for my little show finale yeah that's a pain when you do that, you won't belive how many times I've down thatI'm glad you got them working good enought to have a few in your show!bob
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