Junior Level One: 4" Patriot

Hey guys! I am super excited to show you this build, because I am quite happy with the results. I will do my best to make this thread as in depth as possible.

My dream rocket to build is the Madcow Super DX3, it seems like a blank canvas with massive size. I really was hoping that this rocket would be placed on sale during Black Friday, instead I found the 4" Patriot at a nice price. I placed my order and began to build. Below are the steps I took, recalled and recorded the best to my ability. I hope you enjoy the read, and confirm that the build was up to par for a certification flight.

Parts:
The Madcow Website lists these parts as what comes in the box:

High Power Rocket
Heavy Duty Plastic Nose Cone
1/4" Plywood Laser Cut Fins and Rings
Delrin Rail Buttons
Cut Vinyl Decal
Pre-slotted Airframe
9/16" Tubular Nylon Shock Cord

I also opted for the optional 36" parachute, with a 38mm Motor Mount.

Along with items above, I also purchased 2 quicklinks, I believe they are .25" (I will check later), some 15 min epoxy from US Composites, an extra set of centering rings, and some run of the mill 5 min epoxy.



Tools:
As for tools used, a dremel with proper attachments, table saw, miter saw, rulers, and a lathe were all needed, when each was used will be mentioned throughout the thread.

The Motor Mount:
I did some research to see what the lengths of 38mm motors were, and what I would be expecting to use in this rocket. I opted to cut the motor mount tube to 12". This cut was made with a miter saw. Due to how the saw cuts, sanding was needed to ensure that the tube still maintained the same shape as before. After the tube was cut, some simple meassuring yeilded where the centering rings needed to be placed. I intended to place the forward ring about a .25" behind the tip of the tube. The middle ring was placed in a position where the ring would line up with the already slotted fin slits, this would allow for epoxy to contact the forward end of the through the wall fins, and the middle ring. The aft ring was then to be placed on with the internal fillets completed. I intended to place the assembly in so that from the aft end of the body tube half of an inch of the motor tube would be exposed.

Mounting the Rings:
Before I epoxied any ring to the tube, I placed the eyebolt assembly into the forward ring. After making sure the eyebolt was in nice and tight, I took some 5 min epoxy and secured it in place. I did not follow the instructions recommendation for the eyebolt position, instead I installed the eyebolt with the opening like so:

This allows for easy removal of the shockcord assembly via a quicklink.



The first step was to sand down the location where the rings would be mounted to the motor mount tube. The are was sanded so that the coating on the tube was removed, allowing the ring to bond directly to the tube in a wood to paper bond. This adds a bit of security with the bond strength.

I work in my neighbor's carpenter shop, so he is always suggesting things to teach me and how I could do my projects better. He suggested making a 38mm hole in a square block of wood, and using this as a way to ensure the rings would be square when bonding to the tube. I did exactly this, and ended up with this set up:


This would allow me to place glue where the ring would rest, slide it into place, and then place glue on one side of the ring, wait for it to set, then glue the other side with the clamp removed.

The epoxy I purchased required a 4:1 ratio of hardener to resin. To make sure these amounts were as exact as possible, I used syringes to measure out the two parts. This work quite well, especially when it was a nice temperature outside because both the resin and the hardener became a lot more viscous. I then would mix the epoxy for a good 5-8 mins before I applied it to the desired location.I did this for the motor mount, in the steps described above, and was pleased with the result.


Mounting the Motor Mount:

As mentioned above, my goal was to have the motor mount positioned in such a way where the middle ring is placed just right in respect to the fins, and where the tube stuck .5" from the end of the body tube. I at one point had the math all figured out in a sheet of paper and intended of showing it here, but has since lost it. I may go back and post it at a later time. Rest assured, the measurements were made, and I was confident I would get the mounting position I would be pleased with.

The prep was much like mounting the rings to the motor mount: sanding down the bonding location. This was done, and I was ready to mount the motor mount.

I wanted to make sure I could bond the rings to the tube in two place: forward of the middle ring, and forward of the forward ring. To do this, epoxy was placed as best possible where the middle ring would sit, but to ensure it would bond in the strongest way possible, I slid the motor mount to such a position that the middle ring was just behind the forward end of the fin slit. At this point, I needed a way to get glue into the slit, let it move around, and then push the assembly to its final position. To accomplish this, I used a very large syringe to put glue into the fin slots, where once the ring was pushed into place the epoxy would bond the middle ring to the body tube.


I followed the same procedure for the forward ring, but stuck my arm inside the BT, and made sure to make a nice epoxy rim where the ring and BT met, this was the result:


I was super pleased with the epoxy distribution, and was shocked that the large syringe worked so well, I was almost certain the epoxy would not be friendly to the tool.

Mounting the Fins:

To mount the fins, my carpenter friend showed me how to make a nice guide. I then made one myself.


First two cuts were made that were .25" in depth into the wood piece with a table saw, each perpendicular to one another; this is where the fins would sit in the mount. Next, I used a lathe to make a circular divet the same depth as the initial cuts. This was because the fins were to be flush with the end of the BT. Next, a hole was cut in the middle with the lathe to allow for the motor mount to slide through.

This created a fantastically sturdy platform for the fins to be mounted with, but one that required special attention as to not bond the mount to the rocket itself. I explored using wax paper as a solution to prevent the guide from being epoxied to the rocket, but opted to just use extreme caution when epoxying instead.

Each fin, fin slot, and fin mount slot was numbered to ensure there wasn't any confusion when I went to mount them. I then mixed the epoxy, placed each fin in, applied pressure to the mount, and placed it on a flat surface. I then used some elastic bands to make sure the fins were being pressed against the BT, and waited the proper amount of time.

Removing the mount, the fins were on nice and straight, and I was very happy. They certainly run parallel to the body of the BT which is nice, meaning less of a roll on launch day.

Fin Fillets:

It was then time to add the fillets to the fins. Sanding was done to the base of the fin, where the epoxy would bond the BT and the fin. The BT was also sanded in the corresponding location.

To make sure each filet was as uniform as possible, I measured a .25" from the base of the fin up on the fin, and .25" from the base onto the BT. I then applied a straight piece of tape on the fin and the BT to allow for a clean looking fillet.


Epoxy was then mixed with Phenolic Microballoons. The consistency of peanut butter didn't seem that possible without adding a very large amount of filler, so I added a fair amount, and proceeded with the fillets. I let the epoxy sit there for about 3 mins after pouring it into place, then ran a Popsicle stick over it to round it out. After about 5-10 mins, I removed the tape. The result was always a straight line of epoxy.

I repeated these steps for each external fillet and was generally satisfied. Some fillets turned out larger in diameter than others, but nothing too extreme where I would be concerned about balance. These fillets are large, and very, very, very, strong. I have no concern about them holding up.

Internal Fillets:
Internal fillets were messy, and a lot less smaller than the external fillets, but what important was that they bonded each part to eachother, which they did.

Here is what they looked like, I'm not proud, but hey, who really is about the internal fillets:

Payload Section:
With the more technically challenge parts of the build out of the way, this was a breeze.

To start off, I took the provided bulk plate, attached the eyebolt assembly, and glued it into place with some 5min epoxy. This bulkhead assembly was then glued a little more than flush into the coupler with some 5 min epoxy. This was to allow for more surface area of epoxy exposure. This coupler 8"in length, was epoxied with 5 min epoxy into the BT with 4" exposed. Sanding was done before the bonding of the coupler to the BT.

Using a miter saw, I cut the base of the nose cone off, this will be useful for adding the weights later on. As of now, I am planning for a friction fit of the NC to the payload section, but that could change.

Tragedy Strikes:

This was not fun...

Long story short, I came home one day to find my rocket crushed by my garage. I was lucky, the crush had left about 5" of the BT not harmed by the door forward of the forward centering ring. This saved my build. If the crush had left no viable BT left to mount a coupler to, I would have been done. There was no way I was going to fly a damaged rocket for my cert flight.

After ordering a coupler and some length of 4" BT from Madcow, I cut the damaged BT off, and cut the newly ordered tube to the right length needed with a miter saw. I then used some epoxy, and epoxied it together. Sanding was done before hand in the proper places. Here are some action shots


Conclusion:

Taking the rocket into the postal service, I got 3 messurements:

Weight of aft section of the rocket (everything south of the coupler attaching the payload bay): 27.40 Ounces
Weight of payload bay + nose cone: 15.30 Ounces
Weight of aft section with chute, quicklinks, and shock cord: 36.8 Ounces

This was a fantastic surprise, the simulated file in Open rocket is about 2 ounces off of what I have measured. I was concerned the rocket was to be way too heavy. I also did the simple CG test where I hung the rocket to try and find out where everything balanced: this observed CG was only about an inch off of what the simulation predicts. With playing around with the model more, I am sure I will have an accurate simulation for launch day with an accurate CG.

As of now, I am working on filling the BT and sanding it down, prepping for paint. I also need to purchase a motor retention system, and mount the rail buttons. I have two sets, and am kinda lost on which set I need to mount, if I can't figure it out, I'll ask here. I also have some recovery questions as to how strong my swivel is that I purchased, and motor recommendations, but we'll worry about that later.

All in all, I think she is ready for flight. I have named her Rosie after Rosie the Riveter. I needed something patriotic because the rocket's the Patriot, but needed a name to call her by. (I do this with a lot of things haha)

Thanks for the read! I am so excited to fly, and am looking for launch locations in Michigan. I'll have the open rocket file up soon, with some paint, and final pictures!

(I have yet to proofread, so please excuse any errors)

Not bad!!

nice work! i too picked up the patriot at the BF sale. I hope mine turns out as well as yours.

Fantastic work so far! This is one of the rockets on my short list, so your great detail and pics in the build thread are much appreciated! Sorry to hear about the disaster; however you handled it great and solved it quickly without getting discouraged. Kudos!

Hey! It's always cool to see another Jr. on here. Your build looks great! I'll keep an eye on this

Thanks for all the responses! I'll do my best to keep the good results coming.

Recovery
So the kit comes with a 36" chute, which I purchased a swivel from LOC-Components. I am a little confused as how to attach the chute to the swivel. If I do the standard make a loop and slide the chute through the loop, the two middle chute lines appear to cross, resulting in uneven length when the chute would be deployed. This is what I mean:

I also have a nomex blanket which will protect the chute.

Is this normal? It seems incorrect? Should I be worried about the strength of the swivel as well?


Filling
With the reconstruction that had to be done, plus my sloppiness with the epoxy, I had to sand down some areas to fill them with wood filler. For the epoxy I had to use a dremel attachment, while for filling holes and the spirals, I used Elmer's wood filler. It works well for the tiny bubble holes left in the fillets. Here are some glamor shots, not finished yet and need a finishing sanding, of what grit I will find out.
Before:

After:

Some extra shots:

(Didn't mean to submit ha-ha)


I'll have the open rocket file up soon, along with some flight plans. Can't wait!

Orion14ed said:

I am a little confused as how to attach the chute to the swivel. If I do the standard make a loop and slide the chute through the loop, the two middle chute lines appear to cross, resulting in uneven length when the chute would be deployed.

Click to expand...

This to me is quite common...even with the Estes plastic chutes and my way around it is to first mark the center of each loop so you know the mid point and ideal point for attaching and then grab all the loops at the midpoint together and tie a knot leaving just enough space on the end to pass the entire chute through again for the swivel/anchor (don't put the knot too high on the chute otherwise you'll be reefing it). Others may have a better method, but this has worked for me so far.

KenECoyote said:

This to me is quite common...even with the Estes plastic chutes and my way around it is to first mark the center of each loop so you know the mid point and ideal point for attaching and then grab all the loops at the midpoint together and tie a knot leaving just enough space on the end to pass the entire chute through again for the swivel/anchor (don't put the knot too high on the chute otherwise you'll be reefing it). Others may have a better method, but this has worked for me so far.

Click to expand...

Should I be concerned about the strength of the swivel? If the deployment is at too high of a speed (within reason) should I worry about the swivel breaking?

How would you all recommend adding nose weight? I was thinking of using buckshot with epoxy and just placing it into the nosecone top, will this work, or will the epoxy not bond well enough?

Also, what grit sand paper would you recommend for finishing the body and the nose cone, I want a nice look to her when she's finished.

About to buy an aeropack retainer, after that, the railbuttons are on, and the weight is placed in, it'll be all ready!

I am aware of stability calibers and how they operate, but now much overstable is too overstable? I want to put in enough weight for my largest motor, but this would make it quite over stable. What margin would you recommend for the safe side?

Thanks everyone!

Orion14ed said:

Should I be concerned about the strength of the swivel? If the deployment is at too high of a speed (within reason) should I worry about the swivel breaking?

How would you all recommend adding nose weight? I was thinking of using buckshot with epoxy and just placing it into the nosecone top, will this work, or will the epoxy not bond well enough?

Also, what grit sand paper would you recommend for finishing the body and the nose cone, I want a nice look to her when she's finished.

About to buy an aeropack retainer, after that, the railbuttons are on, and the weight is placed in, it'll be all ready!

I am aware of stability calibers and how they operate, but now much overstable is too overstable? I want to put in enough weight for my largest motor, but this would make it quite over stable. What margin would you recommend for the safe side?

Thanks everyone!

Click to expand...

Well, I may not be the best person to ask about a 4" Patriot. Mine seems to be "snake bit". It seems to break every time I fly it. Broken fins, cracked fins, and the last flight had a tennis ball size of the BT get ripped out at the top of the BT. I would call it a zipper but it was more like a shark bite.

With that said, I wouldn't use the type of swivel pictured in your post #7. I tried one like that once and it got bent/stretched and stopped spinning on the first flight. I've also found that the only time a swivel is really needed is when doing DD and the fin can spins while the rocket is dropping from apogee to main deployment. The higher you fly and the longer the drop, the more the spinning/twisting happens. With motor deploy, there is seldom enough spinning or twisting that happens to the shock cords to be much of an issue since the fin can hangs under the chute almost immediately and doesn't spin.

As for adding nose weight, I'm also not the one you need to ask about that. What I've found is that in most designs (about 10:1 to 20:1 height to diameter) where the CP is near or just above the top of the fins, the CG doesn't change that much from a small motor to the largest. The total weight of the small motor is behind the CP but doesn't shift the total CG much because it is relatively light. Only part of the weight of the largest motor is behind the CP so it doesn't shift the CG relative to CP by much either. Check your sims, but you may not need much if any nose weight.

As for margins, I've found that a stability margin over about 3 calibers can be problematic. If there is much wind at all, it can and usually does tilt into the wind quite a bit and flies at a much lower angle and has a much longer recovery walk than a rocket that flies straight up. There are a lot of factors that play into this, but my suggestion would be to keep the stability margin between .75 and 2.5, with the 1 to 1.5 caliber being the sweet spot.

Good luck!

Nice post - great build - I really enjoyed reading this - keep up the good work!!

- Rocket crushed by garage door!!! Oh Man! - I hate when that happens!

- So lesson learned... Remember not to leave your Rocket under the open Garage door

Should I worry about a vent hole? The retainer comes in the mail today, so all I have to do is mount the rail buttons and I'll be all set. Once I add the nose weight, launch is next month!

Hope you at least attach an 808 camera to the outside for a nice "ride-along" of your cert flight

I am real close to launch, this week I am mounting the rest of the parts and will start painting!

So I went in and attempted to make my model as accurate to the real thing as possible.

Each stage without overriding anything was within an ounce of the actual measured results, so I was pleased there. This meant the aft section of the rocket comes in at 27 ounces, with the forward section coming in at around 15. The center of gravity was about an inch and a half off from my hang test, so I had to override the aft sections CG to make it accurate. I could not add mass because the mass was already accurate, so I was not sure what was up there. If someone can tell me if this will be an issue, please respond. I believe any discrepancies in small amounts like that will be accounted for by over predicting the location of the components and weights to make the CG as far aft as possible, then adding nose weight to account for this. This should make the rocket more over stable, which is much more ideal than under.

I decided to roll with the heaviest 2 grain H from cesaroni for my nose weight. Please take a look at this file and fix as you see fit. Here are some for sure values to consider:

Weight of aft section of the rocket (everything south of the coupler attaching the payload bay): 27.40 Ounces
Weight of payload bay + nose cone: 15.30 Ounces
Weight of aft section with chute, quicklinks, and shock cord: 36.8 Ounces

Fixed weight of the chute provided by madcow: 3.1 Ounces

If anything seems off, let me know!!!

Thanks in advance!

Also, should I worry about a vent hole, how lose should the separation point be, and is the rod velocity enough?View attachment barepatriot.rkt I dont know why open rocket keeps doing this, but it saves it with the CG of the entire rocket locked, please uncheck that along with anything else that is locked except for the aft BT CG. For some reason it won't save correctly and it is frustrating me to no end.

Orion14ed said:

Should I worry about a vent hole? The retainer comes in the mail today, so all I have to do is mount the rail buttons and I'll be all set. Once I add the nose weight, launch is next month!

Click to expand...

Yes, You need a vent hole.

My apologies for straying off topic, but what does the 4&quot in your thread title stand for?

What motor are you planning on? I'm trying to look at velocity off the pad but there are no motors saved. Anywhere from 35+f/s is usually fine. The faster you go, the less likely it is that you will weathercock.

DRAGON64 said:

My apologies for straying off topic, but what does the 4&quot in your thread title stand for?

Click to expand...

I'd guess it was supposed to be 4", but due to some strange issue, it came through the way you see it.

I have no idea why that happend. I could have swore it was " and turn it got changed. As for the question about the motor, I was using the weight of the heaviest two grain cesaroni motor. I don't think the fps was that fast, which is concerning. I can't check now, but I will soon. I am going to add about a pound of nose weight, which seems reasonable but heavy.

Sorry for the double post.

I looked up the motor weights, highest 2 grain motor is the H125 (according to Apogee). I put in the proper amount of noseweight to make the rocket loaded have a margin above 1. The chart shows that even with this motor, the stability jumps up a large amount in flight, almost to 3. I understand this would mean quite over stable in flight, but am not sure how much that matters.

Heres the file, again if it locks the CG for the stage, please uncheck it and every other CG lock instead of the bottom of the rocket, thanks! (The file is being weird.) View attachment barepatriot.ork

Alright! I added the rail buttons, as well as a 1/4" vent hole. All that is left is the nose weight. If someone could check my file and make sure the amount I have simulated is correct, that'd be fantastic. Instead of be-be's, I am going to use another type of weight for less surface area for the glue to have to bind to, any suggestions? The vent hole is also near the separation point, which from an apogee newsletter, sounds right.

So I added the nose weight, and have the final numbers on this rocket:
Mass with no motors is 1759 g, this has been measured on a scale so I am confident the weight of the rocket is around this amount.
CG is around 23" without any internal components.

I needed to add about 680 grams of nose weight, which seemed like quite a bit. I was worried the rocket would be over stable but looking at stability vs time in open rocket none of the two grain Cesaroni motors take it over 2 margins, which is nice.

Here is the file, it has no internal components but is accurate by weight.

My final questions are:
Is around 20-30mph off of the rod safe? I've read around there is fine, but just would like to be sure.

Is my 1/4" vent hole near the separation point too large? I could fill it in and drill a smaller one. And should I worry about the ejection charge pushing the heavy upper section of the rocket apart?

I would also really appreciate if someone could double check my stability figures on 2 grain motors. They all look fine stability wise, but I don't want it reaching above a 2 during flight as that could be very problematic.

View attachment acuratepatriot.ork

Once I add the rivets to the nose cone, she is finished and off to be painted! I'll be looking for a flight sometime next month!

I can't check your file right now, but I wanted to say that I'm excited to build this rocket. I found a deal that I couldn't refuse so it should be here next Monday.

I built and flew the Madcow Patriot for my L1 on the CTI H225, used epoxy clay for fillets, 15 minute epoxy everywhere, no nose weight, no vent hole, and set up the payload bay as removable so I could add dual deploy later. Hit about 1400' on the cert flight. I've flown all the way up to the J354 in dual deploy configuration up to 4700ft with no issues and never added nose weight. The electronics bay added a pound far enough forward it remained over 1.5 stable. It is a super flier and always straight flights. When it's time to retire this one I'll replace it with a fiberglass one for more durability.

Should I fill the vent hole? I've never used one and don't want to have a separation issue because of it. I'm confident the rocket had good stability and weight, but just would like some clarification on the vent hole.

Also, if someone could send the proper way to pack a chute myway, that would be great. I have heard of several ways but just would like to hear your opinions.

And if anyone could double check my sim, that would be great!

And @dgreger congrats on the l1! She's a good looker!

well after adding 17' of shock cord and 36" chute(you should use a 48") I ran a couple of flight sims, on a 6' rail I would go with the H165 with a 6 second delay. otherwise looks good so far.
Rex

It's

Rex R said:

well after adding 17' of shock cord and 36" chute(you should use a 48") I ran a couple of flight sims, on a 6' rail I would go with the H165 with a 6 second delay. otherwise looks good so far.
Rex

Click to expand...

I'll see if I can make that happen! I am still concerned about the vent hole and really just would like to know if its too large, I don't want the separation to fail!

I started priming! A long way to go, there are some imperfections that I need to work out. I didn't fill the bt as well as I thought I did, but I'll take it!

Well, to be completely honest, the vent hole you have is wayy too large. 1/4" is bigger than you need for most rockets. A vent hole for your rocket should be like 7/64th or so