MADCOW 4" FRENZY CARDBOARD ROCKET... A BUILD THREAD #1

[Rex R]

some kit makers like to use the 'stage' over ride to set the design file mass and cg locations...the demented bovine is one of them. reset the overall cg/mass over rides to zero (untick the boxes) and you should be back in business.
Rex

 

[TMJ]

some kit makers like to use the 'stage' over ride to set the design file mass and cg locations...the demented bovine is one of them. reset the overall cg/mass over rides to zero (untick the boxes) and you should be back in business.
Rex

That's what I did, Rex. I unchecked all of the CG overrides, but had to override the mass of the custom components, myself, to reflect the true weight of what items were going into the rocket, and where they were going to ride. This one is a "head-scratcher". One good thing, though. The flight sim gives me good altitude being 14 ounces heavier than I truly am. I'll get a bit more reach than the simulation predicts (if 'that's' truly accurate)! LOL

 

[tim cubbedge]

I use the "stage configuration" to input total weight and actual CG.

 

[TMJ]

I use the "stage configuration" to input total weight and actual CG.

I 'think' that I am doing the same thing, but something is still wrong. I'm 'unchecking' all CG overrides. My menu, in the design window has 'no' CG symbols beside the listed item, not even the first 'stage' feature listed. Help please. What should I see on my screen to insure that I am doing this properly?

 

[TMJ]

I might be using the software incorrectly. Not sure. All I'm sure of is where the CP is supposed to be. Knowing 'that', I can properly balance the rocket with, or 'without' any software. I wish I had time to learn more about Open Rocket, right now, but I don't. I have less than a week to finish this up, or miss my shot at Airfest...

 

[Rex R]

three possibilities that I can think of 1) one or more of your components has an incorrect weight (this includes shock cords and parachutes). 2) one or more sections has an incorrect over ride/ the stage over ride is set. 3)long shot did you set the fin filet radius? anyway see the picture to see which part we are referring to as the overall stage item(grumble, windows. have to see about re-installing my paint program).
you will need to recheck all your weights/over rides, are you comparing the real weight to sim weight with or w/o engine 14 oz. sounds about right for a motor weight...
Rex

 

[TMJ]

three possibilities that I can think of 1) one or more of your components has an incorrect weight (this includes shock cords and parachutes). 2) one or more sections has an incorrect over ride/ the stage over ride is set. 3)long shot did you set the fin filet radius? anyway see the picture to see which part we are referring to as the overall stage item(grumble, windows. have to see about re-installing my paint program).
you will need to recheck all your weights/over rides, are you comparing the real weight to sim weight with or w/o engine 14 oz. sounds about right for a motor weight...
Rex

Okay Rex... check 'this' out! When I had the CG symbols along side the menu items, as shown in your attached image, my rocket only weighed 3.5 pounds 'loaded'! When I unchecked all of that stuff and had no CG symbols at all it weighed 14 ounces more than my rocket weighs. I 'am' weighing the rocket with the motor case 'and' the bates grains installed. 'Actual Flight Weight'! This is a head-scratcher. Something is amiss. Maybe I need to uninstall/reinstall my software...???

 

[TMJ]

All confusion aside. I know where the 'center of pressure' should be. That being known, I can easily balance this thing without any software. I'm just wondering why I'm getting conflicting results that don't match what I've got. I'll figure that out later. For now... "I'm balancing a rocket!" :wink:

 

[tim cubbedge]

When you select "stage", you should see this window. In my case, I have input my measured CG & weight. My mass with no motors and the CG I input can be seen on the rocket view. The CG & weight will be recalculated once you select a motor & the actual weight & CG should be really close to what OR states (assuming y0u are not using any spacers)!

 

[Rex R]

just out of curiosity how do the numbers compare w/o motor and where do the cg fall (likewise w/o motor) that should tell us where to look for phantom weight, the mass over ride for the fins is the total mass of the fins, not per each fin.
Rex

 

[Banzai88]

This is where you get caught up in the danger of sims. Individual component weight 'what it's supposed to be' only really matters for initial estimating.

Once you get the rocket built, DO NOT override each component or add in 'epoxy' or 'paint' or anything silly like that as a distributed part. Get the form factor of the rocket correct, and THEN override the ENTIRE rocket weight and non-engine CG. That's really the only way to ensure that the computer model matches your real world piece, complete with epoxy and paint.

OR will then adjust the CG for each motor.

CP, once adjusted for 'actual' form factor, should be close to factory, but expect some variance.

 

[DavidMcCann]

Once you get the rocket built, DO NOT override each component or add in 'epoxy' or 'paint' or anything silly like that as a distributed part. Get the form factor of the rocket correct, and THEN override the ENTIRE rocket weight and non-engine CG. That's really the only way to ensure that the computer model matches your real world piece, complete with epoxy and paint.

Exactly what I do. Who cares what a fin weighs? Overall weigh gets plugged in, I balance the thing over something and find the CG, measure it, input it...done.

I skip the rest of the tomfoolery....

 

[TMJ]

Many thanks, guys! Your help has payed off. I did the 'stage' thing and overrid the entire weight, adding the true weight, and set the CG .4375" south of the mfg recommendations (due to the CP moving that far aft via the av-bay upgrade). I 'now' have a rocket with a 'non' motor stability of 1.01 cal. Stability 'With' the motor is .306 cal. The given weight 'with' motor now matches my rocket 'EXACTLY'!
Everything is in order!

Now... is .306 cal stable enough to launch? Should I add some nose weight, or just leave it alone?

 

[tim cubbedge]

Probably a good idea to add some nose weight. Most people like to see a stabilty of 1-2 calibers with motor installed!

 

[Banzai88]

Yeah, with that style rocket, with any motor in a given class, you want 1 cal stability OR BETTER. Remember what I said WAY back at the start of this thread? An overly nose heavy rocket flys low, a tail heavy rocket flys once. Unless it's a stubby (base drag and all that), anything less than 1 cal stability is, generally speaking, tail heavy.

Now you understand another power of a sim, it can assist you in planning for things like this. Hopefully you have access to the inside of the nose cone easily. You can cut a hole or a hatch, or simply add a tracker bay up there. Most use gorilla glue or epoxy or foam to hold BBs or lead fishing weights in place. Many use a cross brace as additional structural insurance.

Myself, having had a nose weight not stick to the plastic of a nose cone once, I always use some sort of cross brace to anchor the weight. I prefer a #7 lead shot and RocketPoxy slurry. On plastic nose cones I use a drywall or a deck screw through the side of the nose cone near the tip from side to side, at least 1 inch up from the tip. I dremel off the ends that stick out and make it flush, then spot putty to cover the slight divot. Pour in the weight/glue mix and keep it point down until it cures, then prime/paint the nose cone. I've never had a high power nose cone go soft from any kind of heat from the epoxy curing.

Everyone has their own approach, most work fine.

 

[TMJ]

Okay, the sim got me again, but not in a bad way. I reloaded the rocket motor with propellant and physically checked the CG of the rocket. It's not .306 caliber, as the sim showed. It's actually 1.4 caliber without any nose weight. This is based upon the mfg's CP which also jives with the CP shown in the sim.
I'll become more familiar with software sims, given time. For now, I see them as a good way to locate/verify the CP and run flight simulations. Fun and interesting stuff.

 

[TMJ]

Yeah, with that style rocket, with any motor in a given class, you want 1 cal stability OR BETTER. Remember what I said WAY back at the start of this thread? An overly nose heavy rocket flys low, a tail heavy rocket flys once.

Yep, I remember you saying that. The phrase stuck with me. I was simply wondering about the 1+ cal thing after reading about folks sometimes keeping the CP really close to the CG, for some reason. Probably different types of rockets, performance, or something. It obviously had no bearing on what 'I' am doing, as I can't remember who, what, or where I was reading that! LOL

 

[TMJ]

Decent rate... The sim shows my 'ground Hit Velocity' to be 5.66 m/s. That's about 12.7 mph. That's not too fast for Airfest Kansas dirt is it?

 

[TMJ]

Aircraft safety wire motor retention. I was unable to find my safety wire pliers and had to order a new set, but here it is, finally. This is nothing but a single loop of wire twisted snugly around both the Loki motor case, against the thrust ring, and the three motor retention screws. One loop p/screw. after the wire is twisted snug, I simply tighten the screw until the wire becomes taught. Screws are backed with blind nuts. Very simple to do, very secure and very light. This motor case isn't going 'anywhere'!

 

[TMJ]

I'm now in the process of working through my 'punch-list' of small things to do, prior to launch, such as tidying up/securing my electronics bay wiring, snugging up the nose cone fit, adding Loctite to hardware, etc..
I'm not sure if I'll be able to perform deployment charge ground tests, due to conflicting work hours and weather conditions. I might have to do 'that' after arriving in Kansas, this weekend. Aside from the deployment ground tests... there's really not much else to add to this thread except for hopeful flight photo's and 'more' hopeful certification results. I feel quite confident that all will go well thanks to all you fine folks who have helped me out in getting into this HPR thing. "My fingers are now crossed!" :handshake:

 

[Banzai88]

Decent rate... The sim shows my 'ground Hit Velocity' to be 5.66 m/s. That's about 12.7 mph. That's not too fast for Airfest Kansas dirt is it?

That converts to about 18fps. Target for LPR/MPR is 12-15fps. For most of my high power/heavier stuff I target about 18-20fps. Seems to do fine in the plowed dirt that I usually land in for cardboard and plywood rockets. If push comes to shove and you don't have many parachutes to choose from to suit wind conditions of the day or landing conditions, I'd opt for a lower deployment altitude and a softer landing with a larger chute. BUT, to do that, you have to know damn sure how long it will take or how far your rocket will fall between deployment and inflation.


All fiberglass birds can stand a fair bit more impact velocity. I've seen data on at least one member who brings his Screech in at 34fps!!! Yikes!

 

[TMJ]

Argonia, Kansas is definitely a place that I could live. It's a beautiful place, slow paced and the locals are Amazingly friendly. Argonia, Kansa is the epitome of a priceless Norman Rockwell painting! If you've not been there, for an Airfest... I strongly suggest that you put it on your 'bucket list', but I digress. This is not a travel forum...

During my visit, I was extremely 'privileged' in being allowed to hang out with and associate with some extraordinary rocketeers. Jim, Tim, Roy, Bob, Scott, Jason, Charlie... the list is quite lengthy. To all you Airfest guys; "Many thanks for putting up with me getting in your way, bugging you with questions, asking you to show me the ropes, etc.. I'm sure I was sometimes a pain in the butt, but hey. At least I didn't drink your beer! "I'll save 'that' for the next time we meet!" LOL

Madcow Super DX3 with an I-210 motor, for level one attempt;


Madcow Frenzy with a J300 motor for level 2 attempt;


The 'payoff';


Now... "It's Miller Time!"

 

[neond7]

Congrats!! Now on to spend the $$$$$$........

 

[Banzai88]

Congratulations.

 

[TMJ]

Thanks guys!
Yep, it's time to pony up more greenbacks, now. I've got a few more HPR toys in my sights, including a level 3 bird that I'll be starting on shortly. Pretty sure that 'that' one is going to be an 'Extreme Darkstar'. I'll be taking my time with that one, while also working on my new L1 and L2 builds. I'll also probably be joining up with the Kloudbusters (monthly launches in Kansas). It's only a five hour drive for me. Nice getaway every month, or so. Now that the pressure of certification has been relieved, and I'm a bit more confident and relaxed..."Gonna be a real 'HOOT' my next time out!"
oint:

 

[TMJ]

L1 on its way up. No photo for the L2 Frenzy launch, "Dang it!" Oh well. Better luck next time...

 

[DavidMcCann]

Nicely done. Always good to see the full process and growth and how it takes each of us our own direction.

 

[TMJ]

Nicely done. Always good to see the full process and growth and how it takes each of us our own direction.

Thanks, David. You were a huge part in helping me make this happen! As for our own directions?... "Better buckle up, my friend. The ride is about to get a bit fast and bumpy!" :wink: