Nose Weight for 4in Madcow Patriot

like the title says, is nose weight needed for the 4in patriot? Only will be flying it on either an H or I for a hopeful L1 cert in the future. Thanks for the help!
*also cant measure CG myself because i dont have the kit yet

Instructions can be downloaded from the website. It states the CG as 28" from nose tip. Amount of nose weight needed will vary according to weight of motor and building technique. Most people weight according to the heaviest motor they intend to use.
Or you can add a variable weight ballast system into your nose and add/subtract according to which motor you use.

kuririn said:

Instructions can be downloaded from the website. It states the CG as 28" from nose tip. Amount of nose weight needed will vary according to weight of motor and building technique. Most people weight according to the heaviest motor they intend to use.
Or you can add a variable weight ballast system into your nose and add/subtract according to which motor you use.

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Is it a guarantee pretty much than its gonna need nose weight no matter what?

Can't give you an answer, too many variables. If your build technique is light and only use a minimum engine you might not need nose weight. See steps 23 and 24 in the instructions. Even Madcow cannot give you a definite weight total.
Just find the CG with your chosen motor and make sure it is at or in front of the listed CG, adding nose weight as needed.

I built the 4” Madcow last year for my level 1 and I ended up putting close to a pound of weight in the nosecone.
You can find the rocksim/openrocket files online. Start there to give you a general idea. Then you can edit the file as you build to tweak it to your specific build/configuration.

The actual Patriot missile carries a heavy warhead in the forward sections, moving the CG way forward, and thus can get away with the tiny fins. With hollow hobby rockets, the tiny fins push the CP forward, and thus nose weight is needed to get the CG ahead of the CP.

Now, having said that, I do not have a Madcow Patriot, and I can't answer your question directly. But I do know that if it is a true scale Patriot, it will need nose weight due to the fin size.

14 - 16 oz is about right for a 2 grain 38mm motor(check before trying to fly it), an H242 get it going nicely. please note that the cg location given in the instructions results in a 1 cal. margin of stability.
Rex
also note that it has a payload section...I flew mine on an I161 and a 0.5 lb. of cheese (in addition to the base nose weight). you WILL need to secure the nose cone.

I have a Madcow 4" Patriot with an adjustable weight system (washers) in the nose. I build light, I'm pretty confident you will need weight.

mine got close to 20oz of lead up front..

I'll check my sim for CG and CP when I get home. It has all the weights I use for different motors
Agreed with statement above, the weight I use may be too much/little depending on how you build it.

(I've got ~8oz fixed in the tip for 2grains, and I have a 2oz and 3oz donut to add for longer motors. Doesn't take much extra, the longer motors move the CG up too)
Love the rocket. It was my L1, and has flown on H-J. I'm going to be making an e-bay for it so I can use plugged motors soon.

Nytrunner said:

I'll check my sim for CG and CP when I get home. It has all the weights I use for different motors
Agreed with statement above, the weight I use may be too much/little depending on how you build it.

(I've got ~8oz fixed in the tip for 2grains, and I have a 2oz and 3oz donut to add for longer motors. Doesn't take much extra, the longer motors move the CG up too)
Love the rocket. It was my L1, and has flown on H-J. I'm going to be making an e-bay for it so I can use plugged motors soon.

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I appreciate all the replies, im new to high power (previous kits are estes pro series ii on g motors) so im unsure of how to put the nose weight in the nose cone in the first place. Lead shot with epoxy through a drilled hole is what I gather.

Nytrunner said:

I'll check my sim for CG and CP when I get home. It has all the weights I use for different motors
Agreed with statement above, the weight I use may be too much/little depending on how you build it.

(I've got ~8oz fixed in the tip for 2grains, and I have a 2oz and 3oz donut to add for longer motors. Doesn't take much extra, the longer motors move the CG up too)
Love the rocket. It was my L1, and has flown on H-J. I'm going to be making an e-bay for it so I can use plugged motors soon.

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Also is it possible to fly a 4in patriot stock without any nose weight on an H?

Karsten said:

Also is it possible to fly a 4in patriot stock without any nose weight on an H?

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No. As Joe said, download the Rocksim file from the Madcow website. Run the sims with your chosen engine.
Ran a quick sim on Open Rocket with an H238. With 12oz mass in the nose it shows only .391 caliber of stability.
With no nose weight it looks like the CG will be behind the CP.
Increase the nose mass and see how the CG moves forward. You want it at 28" from the nose or less.
Laters.
PS Forgot to mention, your build may be different depending on technique (heavy on glue, etc.). As mentioned, use the sim to get an idea of the weight needed, and fine tune to the actual CG on your rocket.

kuririn said:

No. As Joe said, download the Rocksim file from the Madcow website. Run the sims with your chosen engine.
Ran a quick sim on Open Rocket with an H238. With 12oz mass in the nose it shows only .391 caliber of stability.
With no nose weight it looks like the CG will be behind the CP.
Increase the nose mass and see how the CG moves forward. You want it at 28" from the nose or less.
Laters.
PS Forgot to mention, your build may be different depending on technique (heavy on glue, etc.). As mentioned, use the sim to get an idea of the weight needed, and fine tune to the actual CG on your rocket.

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Is Rocksim a free program to download? Would be the first time using it

Karsten said:

Is Rocksim a free program to download? Would be the first time using it

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Rocksim has a free trial. OpenRocket is a free version. It’ll read rocksim files. It’ll definitely be a good thing to learn.

As far as nose weight, search the forum. There are multiple techniques. My original build I mixed steel BBs and epoxy. I roughed up the inside of the nose cone and poured the BBs in. Since curing epoxy puts off lots of heat I let the nosecone sit in a buck of cool water so it didn’t melt the plastic.
I’m redoing my patriot and using a threaded rod in the nosecone to attach weights to.

Good luck!

Rocsim isn't free, but Openrocket is and will be fine for your needs as you start out. (go to the software/electronics part of the forum and use visit the top link where Neil has packaged installers for it)

Here's a snip of the simulation for its most recent flight on a J316.
-Pay attention to the CG/CP locations. The locations are the only thing that matter since my weight and finish will be different than yours.
--It has 6oz fixed in the nose for 2 grain Pro38 flying, and I added 6oz removable weight to bring the CG forward. (I just rough up the inside tip, pour in 30 min epoxy, and then dump the lead shot in so it sinks down and settles)
--I design for the CG to be ~10-12% of vehicle length ahead of the CP. Most often you'll hear folks describe stability in 'calibers' (body diameters), but I've found that convention limited.



*caveat* If you use the part dimensions of the kit, Openrocket will give a CP that's further forward than what is in my sim, and it will appear under-stable with my weights. I used a CFD software program to run some tests and determined that the CP for this model is ~35.4" from the tip, so I added those square faux fins (massless) to simulate the rearward CP. It has flown using this CP position (and corresponding CG per motor) on I's and J's so I believe my results have real world validation.


Here it is (as I built it) with no nose weight and a 38mm 2 grain (H) motor. That CG/CP separation is only 5% of the vehicle length (or .6 calibers for other folks)
This has a very low static margin meaning the rocket must get up to much higher speed to be stable on rail exit, and the CP could possibly shift forward causing an unstable flight if it passes the CG

Nytrunner said:

Rocsim isn't free, but Openrocket is and will be fine for your needs as you start out. (go to the software/electronics part of the forum and use visit the top link where Neil has packaged installers for it)

Here's a snip of the simulation for its most recent flight on a J316.
-Pay attention to the CG/CP locations. The locations are the only thing that matter since my weight and finish will be different than yours.
--It has 6oz fixed in the nose for 2 grain Pro38 flying, and I added 6oz removable weight to bring the CG forward. (I just rough up the inside tip, pour in 30 min epoxy, and then dump the lead shot in so it sinks down and settles)
--I design for the CG to be ~10-12% of vehicle length ahead of the CP. Most often you'll hear folks describe stability in 'calibers' (body diameters), but I've found that convention limited.


View attachment 394102
*caveat* If you use the part dimensions of the kit, Openrocket will give a CP that's further forward than what is in my sim, and it will appear under-stable with my weights. I used a CFD software program to run some tests and determined that the CP for this model is ~35.4" from the tip, so I added those square faux fins (massless) to simulate the rearward CP. It has flown using this CP position (and corresponding CG per motor) on I's and J's so I believe my results have real world validation.


Here it is (as I built it) with no nose weight and a 38mm 2 grain (H) motor. That CG/CP separation is only 5% of the vehicle length (or .6 calibers for other folks)
This has a very low static margin meaning the rocket must get up to much higher speed to be stable on rail exit, and the CP could possibly shift forward causing an unstable flight if it passes the CG

View attachment 394103

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Wow! I appreciate all this! There is definetly alot of information to learn and digest. Im going to download open rocket right now and start playing with the files and seeing how everything works. I think this is the hardest part about going for my L1 cert for sure, calculating the nose weight based off the motor. I really do appreciate all the help!

There is a version (current one) of Open Rocket here on the forum that has a built in installer program (by Neil_W iirc). Sorry I don't have the link handy at the moment.
Edit: https://www.rocketryforum.com/threa...d-mac-to-solve-all-your-java-problems.143540/

rharshberger said:

There is a version (current one) of Open Rocket here on the forum that has a built in installer program (by Neil_W iirc). Sorry I don't have the link handy at the moment.
Edit: https://www.rocketryforum.com/threa...d-mac-to-solve-all-your-java-problems.143540/

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Ah thanks! I was just having issues attempting to install it from the main website but that worked perfectly. As far as files go, do I just download and save a rocket file and open it in the program from my computer?
And will rocsim files work as well?

Hopefully you'll get plenty of help here on the forum, although therell be plenty of confusion too. You're absolutely right, knowing how to balance a rocket for a safe stable flight is key to being a successful high power flier. The power gets much greater than low and mid power motors.

Rocsim files will open in OR, but some complex geometries like outboard pods or ring fins arent in OR yet. Fortunately your Patriot doesnt need either of those.

My recommendation is to take your parts and make a sim file from scratch. Weigh and measure your parts, load them in, and you'll get great practice using the program. (You can override each part's weight, or override the weight and cG of the whole rocket/stage)

Nytrunner said:

Hopefully you'll get plenty of help here on the forum, although therell be plenty of confusion too. You're absolutely right, knowing how to balance a rocket for a safe stable flight is key to being a successful high power flier. The power gets much greater than low and mid power motors.

Rocsim files will open in OR, but some complex geometries like outboard pods or ring fins arent in OR yet. Fortunately your Patriot doesnt need either of those.

My recommendation is to take your parts and make a sim file from scratch. Weigh and measure your parts, load them in, and you'll get great practice using the program. (You can override each part's weight, or override the weight and cG of the whole rocket/stage)

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What is a good stability number to look for? I was able to load in the patriot file just now and am playing around with different motors. Is .276cal a good number, or what number should I be looking for? Thanks!

See my post above with my image of sims. Review what I mentioned about the stability margin (distance between CG and CP)

Understanding rocket stability is absolutely critical to building successful high power rockets.

Please Google "Rocket stability, apogee 462" and give that article a thorough reading.

I only use the open rocket or rocsim to identify the cp. All my time weighing and updating measurements ..it really only showed me how far cg shifted when a certain motor was loaded. I learned that even with all the weighing and tweaking of the rocsim , i still had to balance of the physical model.and then use cg overide in the rocsim ..so why try to model the individual weights ?

So now i use rocsim with online rkt file or use mfg location of cp ..mark it on the model ..usually inline with the rail buttons. Then balance empty to find cg ..pencil mark . Done . Sliding in grains into case , close and put into rocket and rebalance then pencil how far back the cg shifts . if weight is needed then can add some up front and rebalance.

I like marking stuff in line with the rail buttons and placing vent holes in line near the rail guides because if there are multiple marks they dont show when rocket is on the rail and if asked by RSO can find quickly.

Kenny

Karsten,

Here's the link to my thread I did a while ago for the same issue. Made it adjustable so that I can use several motors

https://www.rocketryforum.com/threads/madcow-4-patriot-weight.134289/#post-1603851

Hope it helps

fm

I think this is why I've never built a Patriot....

I thought that too...

But, it is a pretty cool bird; I was really concerned after I added the payload bay. That's what threw everything off. The un-'bayed rocket flies like a champ (NYTs has flown repeatedly; well). Though mine will only make it to about 10' (my office ceiling), once I had the weight figured out it was just a matter of getting the takeoff speed right

fm

Forever_Metal said:

Though mine will only make it to about 10' (my office ceiling),

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We'll see about that......

Forever_Metal said:

(NYTs has flown repeatedly; well)

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What does the New York Times have to do with anything?

Nytrunner said:

What does the New York Times have to do with anything?

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I don't know, but whatever it is, it probably requires a lot of fact-checking.

I scratch built a 4" Patriot using the exact dimensions of the full-size Patriot missile. I pushed the AV Bay as far forward as I could get it and still get a 50" chute in the cavity between the nosecone (with recessed attachment point) and the bay itself, and I still needed about 8oz of nose weight to be sure I was stable at my largest motors (6 grain 54s).

On all of my builds, which are pretty much all scratch builds, I have to tweak the numbers in the final build parameters in Open Rocket to be sure that the simulated CG lines up with what the model actually tells me balancing it on an edge to determine actual CG. If they're off, I'll go to the simulation program and "subtract" some weight from one component in one end of the rocket and "add" it to the other end in the simulation, all the while making sure that my rocket's total weight in the program matches the total actual weight of the rocket as measured on a scale. In that way, my simulations more closely mirror the actual rocket at final build weight and dimensions, AND CG is where it's supposed to be.

For what it's worth, I do nose weight LAST in conjunction with the process described in the paragraph above. There is no reason to guess at the weight needed and add too much until all other items are in place on the build. My method is to use tape and lead fishing weights, taping a guesstimate of the weight needed to the nosecone (about where it would be epoxied in), and taking my measurement for CG (without a motor installed). If it is enough, so good for me. If it's not enough and CG needs to be farther forward, I add another ounce and re-balance for CG, then fine tune it until I'm within about 1/16" difference between actual CG and simulated CG. Once I'm satisfied that I have the correct amount of weight, I might trim about 1/2oz off for the weight of the cross-braces and epoxy that will hold my little group of round lead balls in the nosecone. Once the epoxy dries, I double check CG, and if all is good, the nosecone then gets her paint too...


My scratch built 4" Patriot flies beautifully to between 4000' and 10,000' on motors ranging from J-244 to K-260; here she's boosting on a CTI K-520 at Bayboro, NC:

I have around a pound of noseweight in my 4in Madcow Patriot just for H and I motors. BBs and epoxy work if you want a fixed weight, or you could add an adjustable weight system using a threaded rod and washers. I'm sure it's because I built rear heavy, but the Madcow Patriot definitely requires noseweight due to its tiny fins.