Upgraded 4" Madcow Patriot

[Ben Martin]

After my failed L1 I decided to upgrade my 4" Patriot in order for it to be successful.

During my L1 my nosecone fell off, so I'm taking precautions against it. The nosecone I ordered online to replace it ended up being the version that is 2 inches longer than the original due to them sending me the wrong one. I think this might be better for stability reasons due to the mass being able to be further forward. Feel free to express your opinions on it.

So far I have:
- Replaced 3 foot parachute with a 4 foot one.
- Replaced nosecone and added 4 plastic rivets holding it to payload bay in addition to friction fitting with tape.
- Added 1/4" quick connects (the huge ones) to the eyebolts connecting the body to the payload bay.

I plan on:
- Adding a 5/15" all thread rod from the tip of the nosecone all the way to the cap where it would be bolted on both sides. This adds 100 grams to the nosecone for stability and allows for the nose weight to be secured.
- Adding 300-400 grams of epoxy/bbs to nosecone, helping to secure the eye bolt and allowing the mixture to be supported by something. This would push up my CG significantly, I would test my CG before adding too much.
- Tying a butterfly knot in the nylon rope about 1/3rd down from nosecone to add the parachute. I plan on using a 220 parachute swivel and a small quick connect to hold it on. Not sure if the 220 swivel is strong enough, so I would greatly appreciate some feedback regarding it.

These are my improvements/ideas so far, all feedback regarding the change in design would be greatly appreciated. If you have a 4" Patriot as well, please share what you have done with it and what has worked out.

 

[Rex R]

rule of thumb for recovery systems, take the weight of the rocket and multiply by 50. so a quick link rated for 220# can handle a rocket weighing up to 4.4 lb.s HTH
Rex

 

[Ben Martin]

rule of thumb for recovery systems, take the weight of the rocket and multiply by 50. so a quick link rated for 220# can handle a rocket weighing up to 4.4 lb.s HTH
Rex

That seems to be really cutting it close. My rocket is over 4.4lb loaded but recovery would be a bit under.

Do you think it is fine just to connect the parachute with a quick connect?

 

[Rex R]

I connect many parts of my recovery systems with quick links...I would suggest the next size larger(660#) in either galvanized or stainless.
Rex

 

[Ben Martin]

I connect many parts of my recovery systems with quick links...I would suggest the next size larger(660#) in either galvanized or stainless.
Rex

I have big enough quick links, the 220 I was referring to is the parachute swivel that connects the parachute to the quick connect.

 

[rharshberger]

50G's is not a bad starting point for an off nominal flight (early or late deployment, drag separation, horizontal low altitude deployment caused by a hard turn off the pad) all of those events can easily cause a 50G event if not more. As for the swivels, I use them on the fin can to prevent my kevlar from twisting up badly due to the rotation of the fin can as the rocket falls through the air, they need to be sized the same way as the quick links.

 

[Ben Martin]

50G's is not a bad starting point for an off nominal flight (early or late deployment, drag separation, horizontal low altitude deployment caused by a hard turn off the pad) all of those events can easily cause a 50G event if not more. As for the swivels, I use them on the fin can to prevent my kevlar from twisting up badly due to the rotation of the fin can as the rocket falls through the air, they need to be sized the same way as the quick links.

Where did the 50Gs come from?

 

[rharshberger]

rule of thumb for recovery systems, take the weight of the rocket and multiply by 50. so a quick link rated for 220# can handle a rocket weighing up to 4.4 lb.s HTH
Rex

Where did the 50Gs come from?

50G's is what you get from Rex's suggestion, he could have said multiply by 50G's instead of 50 its the same thing.

 

[Rex R]

some time back a knowledgeable member stated his guide for sizing recovery stuff. he used 50Gs. I haven't heard of many failures when folks use a 50Gs to figure stress loads, so I figure that it should work most of the time. you might be alright using a swivel rated at 220# for your chute...but for a cert flight I wouldn't risk it, patriots don't usually twist that much(one benefit of those small fins ). I used #4 shot & epoxy for ballast with screws (as mentioned in the instructions), it seems to be staying put. I did have to redo a portion of my diy motor retainer after the blind nuts came lose. I did use a shock cord protector to shield the lower 30" of the nylon. a 45- 48" chute is about right...get some practice folding the chute though, the space provided is a bit tight. do Z-fold the shock cord (1" blue tape works).
Rex

 

[rcktnut]

I have the PML 4" Patriot and can put any J motor in it without any added weight in the nosecone. The nose cone is longer than the original you had and the fin span is 2.5 in. longer than your Patriot. I have 2 plastic rivets holding the nosecone on. You should gain .50 on the stability margin just by the longer nosecone itself. Adding the mass further forward in the cone will help with the CG. You should not have to add near as much weight as figured before. I would also use the RS CP or a happy medium rather than the Barrowman calcs. The Madcow Patriot might be a little truer to scale than the PML but doesn't bother me.

 

[Ben Martin]

some time back a knowledgeable member stated his guide for sizing recovery stuff. he used 50Gs. I haven't heard of many failures when folks use a 50Gs to figure stress loads, so I figure that it should work most of the time. you might be alright using a swivel rated at 220# for your chute...but for a cert flight I wouldn't risk it, patriots don't usually twist that much(one benefit of those small fins ). I used #4 shot & epoxy for ballast with screws (as mentioned in the instructions), it seems to be staying put. I did have to redo a portion of my diy motor retainer after the blind nuts came lose. I did use a shock cord protector to shield the lower 30" of the nylon. a 45- 48" chute is about right...get some practice folding the chute though, the space provided is a bit tight. do Z-fold the shock cord (1" blue tape works).
Rex

Sounds like a safe bet. I folded my shock cord on my first attempt and it worked out well. I need to get my hands on a shock cord protector, right now I am relying on a single nomex protector.

 

[Ben Martin]

I have the PML 4" Patriot and can put any J motor in it without any added weight in the nosecone. The nose cone is longer than the original you had and the fin span is 2.5 in. longer than your Patriot. I have 2 plastic rivets holding the nosecone on. You should gain .50 on the stability margin just by the longer nosecone itself. Adding the mass further forward in the cone will help with the CG. You should not have to add near as much weight as figured before. I would also use the RS CP or a happy medium rather than the Barrowman calcs. The Madcow Patriot might be a little truer to scale than the PML but doesn't bother me.View attachment 363899 View attachment 363900

I am aiming for a CG that is 30" from the nosecone as that's the recommendation in the instruction. Might be a bit overkill.

I had a perfect flight with rocksim showing 1.3 calibers while OpenRocket showed .3 cal.

 

[Nytrunner]

Take a 15" strip of ductape and fold it over the shock cord at the ejection charge end. Cheap protection for a few flights, then you can shell out for a nomex protector or just replace the ductape

 

[Ben Martin]

Take a 15" strip of ductape and fold it over the shock cord at the ejection charge end. Cheap protection for a few flights, then you can shell out for a nomex protector or just replace the ductape

I'm using the nomex cloth that came with the kit. I notice that it doesn't go very far down anymore now that I added the quick link.

 

[Nytrunner]

Sound right.

I'll bundle the chute and z-folded cord in the 12x12 square that came with mine, then use the ductape on the little tail that hangs out to connect to the booster

Keep on building!

 

[Ben Martin]

Sound right.

I'll bundle the chute and z-folded cord in the 12x12 square that came with mine, then use the ductape on the little tail that hangs out to connect to the booster

Keep on building!

This is what I plan on doing with the nosecone to secure the weight.

 

[Ben Martin]

Sound right.

I'll bundle the chute and z-folded cord in the 12x12 square that came with mine, then use the ductape on the little tail that hangs out to connect to the booster

Keep on building!

OpenRocket says to use 300grams of noseweight for 1 caliper of stability on an H motor, is that too much as I've heard that OpenRocket is not that accurate?

 

[Nytrunner]

Glad you reminded me, here's that file I said I'd upload. This was made back when I cared about naming components and specifying things, so it should actually be helpful lol
Note the Override fins that are there to drag the CP back. That accounts for OpenRocket's conservative figures as well as base drag (plus I do a little flow analysis on the side to validate)
It's one of the most accurate sim's I've got. I flew the I212 today balanced at that CG location and the Alt2 says 2105' (11' off of the sim)

The nose has ~6oz of shot and epoxy in the nose tip (scuffed it like crazy with an xacto blade), and I have a 2oz and 3oz weight to add when needed.

 

[Ben Martin]

Glad you reminded me, here's that file I said I'd upload. This was made back when I cared about naming components and specifying things, so it should actually be helpful lol
Note the Override fins that are there to drag the CP back. That accounts for OpenRocket's conservative figures as well as base drag (plus I do a little flow analysis on the side to validate)
It's one of the most accurate sim's I've got. I flew the I212 today balanced at that CG location and the Alt2 says 2105' (11' off of the sim)

The nose has ~6oz of shot and epoxy in the nose tip (scuffed it like crazy with an xacto blade), and I have a 2oz and 3oz weight to add when needed.

So you would recommend not adding the complete nose weight OR recommends?

 

[Nytrunner]

I'm making no recommendation, just providing data.

 

[David Schwantz]

Hi Ben, if I may ask, what went wrong on your 1st attempt. I ask, as I was going to do mine today but launch got cancelled. Thanks, Dave.

 

[Rex R]

as I recall from up post the nose cone separated from the payload section when the chute opened. no word on the health of the original nose .
Rex

 

[Ben Martin]

Hi Ben, if I may ask, what went wrong on your 1st attempt. I ask, as I was going to do mine today but launch got cancelled. Thanks, Dave.

Nosecone seperate at apogee, never to be found again.

 

[Arsenal78]

I used a Madcow Patriot for my L1 as well back in March, and my nose also fell off but on landing. However someone had some removable rivets that we installed on the field and they passed me. My kit came with blistered tubes (storing the tubes in humidity before packaging caused the layers to separate) and never heard from Madcow after sending them a message regarding it. I also upgraded the chute to a 5ft chute and it worked well. Still to this day not sure why Madcow thought a 3ft chute was enough for that rocket. Finally decided to recycle the hardware and get a Binder Design Jackhammer to replace it. Overall frankly, I wouldn't recommend their Patriot or really any of their kits but that's for another day.

 

[Ben Martin]

I used a Madcow Patriot for my L1 as well back in March, and my nose also fell off but on landing. However someone had some removable rivets that we installed on the field and they passed me. My kit came with blistered tubes (storing the tubes in humidity before packaging caused the layers to separate) and never heard from Madcow after sending them a message regarding it. I also upgraded the chute to a 5ft chute and it worked well. Still to this day not sure why Madcow thought a 3ft chute was enough for that rocket. Finally decided to recycle the hardware and get a Binder Design Jackhammer to replace it. Overall frankly, I wouldn't recommend their Patriot or really any of their kits but that's for another day.

I upped mine to a 4 foot and added removable rivets.

I'm working on adding the nose weight now but underestimated how much epoxy I needed to fill this longer nosecone. I'll be adding another layer after it dries for a bit to cover it up.

 

[David Schwantz]

Be wary of epoxy in that hole. If you did not rough up the surface epxoy will break loose. Glue like foam tac or goop might be a better choice.

 

[Arsenal78]

I remember having to add a good bit of weight to get mine stable and even then, it fish tailed off the rod on an I140 for my cert flight

 

[Ben Martin]

Be wary of epoxy in that hole. If you did not rough up the surface epxoy will break loose. Glue like foam tac or goop might be a better choice.

Kind of too late for that now, but I added the all thread rod for the epoxy to hold onto.

 

[Nytrunner]

Kind of too late for that now, but I added the all thread rod for the epoxy to hold onto.

If the threaded rod is embedded in the epoxy/shot matrix, you're solid. The plastic is slick, but grabbing on those threads makes that irrelevant

 

[Ben Martin]

If the threaded rod is embedded in the epoxy/shot matrix, you're solid. The plastic is slick, but grabbing on those threads makes that irrelevant

Yeah it was added before the epoxy and bbs were added, and it has epoxied nuts on both sides of it on the top.

 

[Ben Martin]

If the threaded rod is embedded in the epoxy/shot matrix, you're solid. The plastic is slick, but grabbing on those threads makes that irrelevant

Yeah it was added before the epoxy and bbs were added, and it has epoxied nuts on both sides of it on the top.