Madcow 1.6 Mini Cowabunga Question

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VonRecktofen

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Hi Folks,
I'm putting together a 1.6 Mini Cowabunga (cardboard/wood fins) and i'm not really clear on where to place the launch lugs.... I'm planning on flying this lil' guy with Estes D-12's at first and then move up to E-9's if all goes well...
The mass with a D-12-5 loaded in it is 156.1gm, and it balances about 1/2" in front of the fins leading edge...
Where should I position them? I just want to be safe and correct...

Thanks for any help!
Franz in NJ
 
I was going to quote the instructions, but the instructions are completely off. The two lugs would wind up being glued on top of each other! I think they just transferred them from the bigger Cowabunga instructions. Anyway, as long as the CP point is between the two lugs you should be alright. I just eyeballed mine:

IMG_20180328_064814_813.jpg
 
Thanks for the information, I had read the instructions over a few times and had even downloaded them from their website as well, and I had come to the same conclusion...
I'll position them like you have yours mounted...

Thanks and wish me luck!

Franz in NJ
 
Good luck, you should be fine. I've flown the Mini Squat, which is exactly the same as the Mini Cowabunga except for the shape of the fins, with the same launch lug positions without any problems. Fun little rockets.
 
Thanks again for the info...
The only other issue I see is how to stuff the nomex chute guard, shock cord, and the chute all there with the nosecone fitting on top... Mine is really not staying on the BT with everything packed ...

Franz in NJ
 
Same here. The only thing I can suggest is to pack everything compactly, but not too tight in the body tube. Easier said than done. You want the nose cone snug but not tight. If it's loose and popping up a wrap of tape around the shoulder might help. And I haven't done it yet, but the nylon shock cord is waaaaay longer than it needs to be for this size. You may consider cutting it a little shorter to save some space. Last thing you want is the chute not deploying because the laundry hung up in the tube. I only pack the chute and shroud lines in the Nomex. The Kevlar is below the blanket, and the nylon is above it. But, like they say, best laid plans of mice and men right? Have fun!
 
Thanks again for the ideas, I’ll trim down the nylon as well, and things should have more space!

Cheers,
Franz in NJ
 
Thanks again for the info...
The only other issue I see is how to stuff the nomex chute guard, shock cord, and the chute all there with the nosecone fitting on top... Mine is really not staying on the BT with everything packed

I recently picked up a Mini Squat. I'm thinking of ditching the nomex for dog barf so I can run a JLCR in it.

Did you guys build these Mini Squat/Mini Cowabunga with epoxy or wood glue?
 
I recently picked up a Mini Squat. I'm thinking of ditching the nomex for dog barf so I can run a JLCR in it.

Did you guys build these Mini Squat/Mini Cowabunga with epoxy or wood glue?

If the rocket is wood and paper there is very little reason to use epoxy, Titebond II is what I use for regular assembly and TiteBond Quick and Thick for fin fillets. If you are going to add a screw on motor retainer (Estes, Aeropack, Rocketarium types) then JB Weld is the recommended epoxy for that, otherwise good ole wood glue will build the best and with fewer chemicals that can be harmful. Wood glue is stronger than the paper or the wood.
 
If the rocket is wood and paper there is very little reason to use epoxy, Titebond II is what I use for regular assembly and TiteBond Quick and Thick for fin fillets. If you are going to add a screw on motor retainer (Estes, Aeropack, Rocketarium types) then JB Weld is the recommended epoxy for that, otherwise good ole wood glue will build the best and with fewer chemicals that can be harmful. Wood glue is stronger than the paper or the wood.

The instructions call for 5min epoxy, but my plan is Titebond II and Titebond No Run No Drip Mould and Trim for fillets. I'm ditching the motor hook/thrust ring and going with an Estes retainer. And as I said I'm going to ditch the nomex so I can shove the JLCR in the tube.

I think Quick and Thick is how they brand the 8oz size and No Run No Drip is how they brand the 16oz size for whatever strange reason.

I also got my Pops a bottle of Titebond II to build his MadCow 2.6" Discovery.
 
TB NRND and TB QaT are the same product pretty much.

Going off their product codes, i think they're the same. All TB products have a 4 digit code. The first three digits is the product, the last digit coincides to the size container.

2403 is the Quick and Thick 8oz. 2404 is the No Drip No Mess 16oz.
 
Thanks for all the information folks!

Attempted first flight with a D-12-5 and this mini-bunga needs nose weight for sure...

Whats the best way to cram weight into this small nose cone? What Cal stability number should I shoot for?

Open Rocket says atleast 130gms into the nose to get at least 1.04 Cal, but it should be more right?

Thanks for any info. or suggestions...

Franz in NJ
 
Hey Folks,
Just bumping this thread again to ask if anyone has any idea how much weight they added to a Mini Cowabunga to help balance it if they were to run an Estes D-12-5 in it?

I added enough split ball fishing sinkers with epoxy to make the nose weigh 130gms, but boy it sure seems like a lot of weight for this Mini-bunga!

Any ideas or personal experience would be appreciated!

Thanks!
Franz in NJ
 
I just checked the nose weight used on my 2.2" downscale (BMS parts) with 24mm motor mount. The nose weight in it was 77.1grams and the nose cone weighed 42.4 grams for a total of 119 grams for the whole enchilada. I has .397 calibers of stability and flies great on F35W's. This rocket is in the short and fat category and so I use the RocSim massless cone workaround to determine nose weight requirements (a transition at rear of rocket 3xDia long with a forward diameter of 0 and a rearward diameter of whatever the airframes diameter is). Once I have found whatever nose weight makes the model stable at 1 caliber with the cone, I then delete the cone from the simulation, the rockets flights so far have flown to within 10% of the simmed altitude. I think you may have way to much unnecessary nose weight. FYI the RocSim mass less cone works in OR just fine (OR is all I use for general designing and simming rockets).
 
Thanks Rich,
That's what I thought, it will be difficult if not impossible to remove the weight from it now...
I originally launched this guy with no nosecone weight at all, and he was all over the place...
When I went back in to OpenRocket software, I had difficulty getting the added nose weight to be separate from the total weight... I added mass to the nose until the Cal was as close to .800 and had to check the mass override to make it work...

Lesson learned, will the excess weight make it unstable, or will it just need more engine to push it to a better altitude?

Thanks for the info!
Franz in NJ
 
Thanks Rich,
That's what I thought, it will be difficult if not impossible to remove the weight from it now...
I originally launched this guy with no nosecone weight at all, and he was all over the place...
When I went back in to OpenRocket software, I had difficulty getting the added nose weight to be separate from the total weight... I added mass to the nose until the Cal was as close to .800 and had to check the mass override to make it work...

Lesson learned, will the excess weight make it unstable, or will it just need more engine to push it to a better altitude?

Thanks for the info!
Franz in NJ

The extra nose weight may want to make it cone (looks like its spiralling on its way up or what some refer to as tail walking), and it will need more motor to get it to better altitudes, along with a larger chute for recovery (maybe). Can you post the .ork or .rkt file and I will look at it.
 
Thanks, I'll try to attach it here.

Thanks again for the help, once I have this figured out on the Open Rocket software, I should be good to go!


Franz in NJ

Can you post a list of the individual parts weights, each and every CG and weight was overridden so its kind of difficult to tell whats what. The nose cone without nose weight would be the most important, along with airframe and fin weights (all of them or individual fin weights). I weigh each component prior to installation so I have a base line, then at the end of the build measure the CG and finished weight and override them under the Stage part.
 
I'm only going to be able to guesstimate individual parts, as it's already together.... I'll be sure to weigh and record each component on my next build.

Nosecone empty 12.4gms
Weight put in nose 95.0gms
Nosecone plus weight epoxied in 107.4gms

Airframe,Fins, shockcord,nomex, chute (14") 91.6gms
No motor


Grandtotal w/o motor ChunkyMiniBunga 199.0gms

Estes E-9-6 weighs approx. 63.6gms

I added what I thought was enough weight to the nose to balance running the largest motor i would ever use, an Estes E-9-6 and keep the Cal as close to .8-1.0 as possible...


This guy will be a chunky minibunga for sure, unless I order another nose and start over!

Thanks for your help!

Franz in NJ
 
It will be a couple of hours till I am back at a computer but I will plug those numbers in and see what comes up.
 
Open Rocket, I am unwilling to purchase RocSim due to the fact that it doesn't seem to be supported or updated by the author/seller any longer.
 
Okay, so I reworked the sim a little based on the information you gave me and a mass less cone due to its being a stubby rocket. With 1oz of noseweight (28grams) it would have a just over one caliber of stability with every motor I tested, removing the cone with the same nose weight gives it a stability margin of .433 with D12, this rocket should fly nicely on that margin of stability. I am attaching the reworked OR file for your viewing, FYI OpenRocket will open .rkt files too.

I did set the parachute deployment to "apogee" instead of "first deployment charge of this stage" that way I didn't have to deal with picking the proper delay for the motor and to prevent errors caused by the too short or long delay causing parachute opening at high speed. The delay length in the simulation table is usually how I pick the best delay for my motors.

View attachment MyMiniBungaRH rework.ork
 
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Thanks Rich,
I use Open Rocket software as well, as I couldn't see paying the higher fee for basically the same information plus a graphic video representation of the flight on what is the Open rocket plot graph...

So in the future, how would I set the software when I download an .ork or .rkt file to start off getting the masses to match up with what my model actually weighs out to? For example, if I build an Estes Star Orbiter and then download a generic .ork file for that rocket, how to I go about changing the mass values of the components to get it close to what my model is as I build it?

Is there a tutorial or guide that would help me to figure out how to set the software up to do this?

Also, in your opinion, should I be concerned about this much weight in the nose of my chunky minibunga, or should I ground him until I order another nose from Madcow and add the proper amount of weight?

Thanks again for all your help, you are truly an ambassador for the hobby!


Cheers!
Franz in NJ
 
Each component has a mass over ride tab under its edit function, if you see a blue weight icon or a blue 4 quadrant taget icon the component has had a mass over ride.

Usually when I download or use another individuals .rkt or .ork file I verify the all dimensions are accurate, then I clear all overrides as the overrrides will not be the same as mine. Pre-assembly all parts get weighed and the information put into OR. Items like mass objects (noseweight) dont really need to be overridden as they are input as actual weights not calculated by the program.
 
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As for the nose cone, if you can drill out some of the weight that would be best, if not the rocket may be okay to fly as long as the parachute is large enough to safely recover the rocket and the motor gets it off the pad safely.
 
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