Madcow 4" Phoenix "Build...Tear...Rebuild" Thread

[KenECoyote]

Hi Everyone!
Years ago I ordered a Madcow 4" cardboard Phoenix during Black Friday special and after my Madcow 4" Patriot build (finishing can be found in the"Pain-triot" thread), I figured this was a logical next step.

Also given that Madcow seems to be (mostly) stocked again and this is available on bf special (last I checked), timing seems good and this may help others.

What entailed was a good reminder to me to plan ahead for builds as well as how to change a build after it's been glued.

NOTE: I will be editing and updating posts as I go...apologies if this drives you crazy, but I used to be a proofreader and editor (believe it or not).

 

[KenECoyote]

Note that I've only just begun the build, so this will be a follow along with me thread.

Background on my build theory: Usually when building some rocket that is new to me, I default to following the directions since the manufacturer should know how to best build the kit...right?

However, in this case there was a bit of waffling for me since:

• I had been away from HP builds for about 5 years (on a long break).
• I had just built the similar 4" Patriot and enjoyed the build.
• Madcow seems to have somewhat sparse instructions imo
• I had heard and seen how the rear fins seemed prone to breakage due only having partial ttw connections (not sure if this was changed in the new kits).

The first point was what lead me to start a stock follow-the-instructions build, but last point was really bugging me and lead me to de-construct the partial build.

 

[KenECoyote]

Why change the build?

The Phoenix missle has small rectangular fins at the bottom spaced apart from the larger fins.



This isn't necessarily a problem if you have full TTW (through the wall) roots, but because of this kit's construction, the ttw root is only about a third of the full fin span.



(The lower right part extending out goes under the forward fin, so the drawn black line is the full ttw root span for the rear fins.)

 

[mikec]

I assume you saw the comment on the Phoenix product page https://www.madcowrocketry.com/4-phoenix/ ? The pics linked from there are interesting, though maybe a little overbuilt IMHO.

Many Madcow kits have partial TTW tabs like this, but the lower fins on the Phoenix will take more impact force than most.

 

[KenECoyote]

The build starts!

Actually, I wasn't planning on a build thread, so I don't think I have any pics of the start, but close your eyes and imagine...

A beautiful pristine motor tube with centering rings masterfully epoxied on with fillets as perfect as one could ask for and then the artisanal handcrafted assembly trial inserted into the bt with the precision of a brain surgeon who moonlights as an explosives technician...yeah, I'm...that..good!

 

[KenECoyote]

I assume you saw the comment on the Phoenix product page https://www.madcowrocketry.com/4-phoenix/ ? The pics linked from there are interesting, though maybe a little overbuilt IMHO.

Many Madcow kits have partial TTW tabs like this, but the lower fins on the Phoenix will take more impact force than most.

Yup, after the above stock build start, I saw for myself how it seemed lacking in ttw and I found the same comment when researching on ways to fix it, however I felt this was a bit more trouble than I wanted.

Was going to post next, but beaten to it lol:
https://goo.gl/photos/W3dtn7KB36ra7G1v9

 

[Hobie1dog]

fiberglass is about as strong as you can get, no worries

 

[KenECoyote]

What next? Why the hesitation?

So I had the motor tube and CRs epoxied together, but that slim rear fin support kept bugging me.

So I figured I should at least try internal fillets to strengthen it from the inside.

Henceforth, I was committed and then went about trying to remove the rear CR off the motor tube so that it can be glued in place after the fins are glued to the bt & motor tube.

 

[KenECoyote]

fiberglass is about as strong as you can get, no worries

This one is cardboard...not sure if there was a fg one when I got it.

Title update/clarification coming!

 

[Hobie1dog]

This one is cardboard...title update/clarification coming...

oh, that's a big difference then.

 

[KenECoyote]

Welcome to the grind...deconstruction commences!

To remove the rear CR that was epoxied and filleted to the motor tube, I first used a Dremel to grind down the fillet.

(Re-enactment)


Then I used a mallet and hammered away at the rear CR and it eventually came loose! The planning and concern about breakage was much worse than actually just doing it.

(Actual crime scene photos)

 

[KenECoyote]

Rebuild & born again!

So now that I had the rear CR off and my rocket was bottomless, I marked the rear CR and added screws so I could put it in place to center the motor tube as I proceed to glue in the fins, but also later remove it to apply internal fillets and when that is done glue it back in place.

 

[KenECoyote]

Sticky situation...

I then epoxied in one set of fins with a nice gloopy epoxy bead, but two things bothered me...

1. The square plywood leading edges just seemed too brutish and probably adds more drag forward, which isn't ideal.
2. The rear fins (even with internal fillets) still seemed too weak in my mindsim and I imagined the nightmare of repairing it if it snapped off...not pretty.

Look closely at the black line where the rear fin meets the bt at the base...the rest is the extent of the ttw root.

 

[KenECoyote]

Breaking bad.

So after a bunch of waffling (go easy and play soon or go do the extra work to make sure it's a better and longer lasting toy?)...I decided.

 

[user 30299]

I've been regularly launching my 4" Madcow Phoenix for the past 6 years. Never broke a fin.
But I've been using a Top Flight 50" chute since day one.

Someone in Australia posted a comment way-back-then that the 36" chute was too small, and
I think they tried a 42" chute. The rocket always descended too fast. They tried a 50" chute
and all was good.

The Phoenix can be pretty heavy if you end up with some weight in the nose cone for stability.

I found the Jolly Logic Chute Release was a perfect addition when using a potent 38mm motor
with that 50" chute.

 

[KenECoyote]

I've been regularly launching my 4" Madcow Phoenix for the past 6 years. Never broke a fin.
But I've been using a Top Flight 50" chute since day one.

Someone in Australia posted a comment way-back-then that the 36" chute was too small, and
I think they tried a 42" chute. The rocket always descended too fast. They tried a 50" chute
and all was good.

The Phoenix can be pretty heavy if you end up with some weight in the nose cone for stability.

I found the Jolly Logic Chute Release was a perfect addition when using a potent 38mm motor
with that 50" chute.

I'd agree with you that big chute is great and the "easy button" if it works with your field.

My club is at a farm with trees immediately behind us as well as parts around and there is a big deep creek immediately behind. Also the farm to one side isn't rocket friendly, so if it lands there you may not get it back.

Originally I was going to make this a quick and easy build with nose deploy and JLCR (HA!), but now I'm thinking of making it funner with dd and pushing the rocket (maybe some good practice and learnings for L3 next year or so).

 

[user 30299]

I'd agree with you that big chute is great and the "easy button" if it works with your field.

My club is at a farm with trees immediately behind us as well as parts around and there is a big deep creek immediately behind. Also the farm to one side isn't rocket friendly, so if it lands there you may not get it back.

Originally I was going to make this a quick and easy build with nose deploy and JLCR (HA!), but now I'm thinking of making it funner with dd and pushing the rocket (maybe some good practice and learnings for L3 next year or so).

If you have a tight field, the 50" chute won't be the issue. The Phoenix and stubby rockets in general like to
weathercock more than most rockets. You'll have this nice straight launch and once it starts coasting the
rocket will take on this nice arc across the sky. Add a little wind and the arc becomes more pronounced.

The Phoenix is one of my favorite rockets. But it really teaches you how to "fly the field". And I have
flown it on tight fields. Madcow's Super Batray is another great stubby rocket with the same challenges.
I have that one too.

Keep your build simple, and you'll enjoy the Phoenix for a long time.

 

[KenECoyote]

Keep your build simple, and you'll enjoy the Phoenix for a long time.

You may want to unsubscribe from this thread then, my friend...because I'm one who likes to do things differently and I don't shy away from challenges...






I took a stock Aerotech G-Force and gave it a needlessly complicated paint job.

I certed L2 with a custom dd modded X-15 where the designer said it wasn't possible (I felt I knew enough by then).

I've often gotten back all the hard work I put into my rockets...in spades.

Also I kinda of know about flying the field. I've never lost a rocket to the field at our club and before I took a hiatus, I had one year with 200+ launches and one rocket lost.

Finally this would be quite a short (or boring?) thread if I did that now.

I do plan to build my 4" Madcow Seawolf stock though and may do a build thread at that point since it's a unique one I don't see very often..

 

[KenECoyote]

Maybe it's a Maverick thing...

So here's a bit more background on why those puny rear fin roots were bugging me...

I built a TLP Maverick a bunch of years ago and it had fins similar to the Phoenix missile (just swap the nose cone!).

However the fins were surface mounted and the stupid things would snap off with almost every launch...even though the rocket itself is extremely lightweight.

Heck, those "stupidfins" (new term I came up with) snapped off at home when the rocket fell off the shelf...twice! This has never happened to any of my other rockets.



Side note is that this rocket was almost lost at the club field when it landed in the creek behind us and sat in the water for about 20 minutes before I could get to it. It was a crazy amount of work to dry out and stretch the shrunken body tube enough so the nose would fit back in (pics are of it post-repair).

 

[KenECoyote]

Cut it out please!

So after trying to figure out the best way to remove the well-glued fin set, I decided to just go at it like a surgeon and bring out the blades. (Don't tell my wife that I used her favorite kitchen knife!)



Luckily, the other open fin slots allowed me to go at the forward fin epoxy joint with a razor knife (repeated scoring wins here) while I also tried going bottoms up (down?) from the motor end with the large kitchen knife.

 

[KenECoyote]

Well...de-finned!


(Some Phoenix tears )

 

[KenECoyote]

Tangram anyone?

Here's a pic of how the two fin pieces fit together and my solution to further strengthen the rear fin.



More details to follow, but this is the main fix and it doubles the ttw root span.

 

[KenECoyote]

Still plugging away at this bird, but I have been researching a bit since @QFactor did give me some pause for thought that maybe this may not be necessary...or maybe I didn't want to consider that after I had completed two tear-aparts! However, I would have to admit that I was influenced afterwards and several times I got to some point on whether additional strengthening was necessary (which entails more work), I just decided to forgo it.

Still, I was curious as to whether there is actually a problem or is it just my personal concern along with that one Madcow reviewer.

Looking at Rocket Reviews, there are only two people listing flights and one did note a broken fin, but due to deployment failure:

Flight Log - 2015-08-08 - Karl Tyrrell's Phoenix, Madcow 4" on J381: "Almost a perfect flight, until the main deployment... Dual deploy with a cable cutter and a deployment bag. The safety string on the cable cutter fouled the deployment bag and kept it from releasing the main. Landed under drogue at 40ft/sec and broke a fin "​

This is one scenario I was concerned about. I was considering pushing my rocket with J motors along with either DD or JLCR and a failed chute opening can always be a possibility. In fact, last year I made the mistake of hooking up a replacement chute blanket incorrectly and it worked it way up and reefed my main chute, resulting in faster descent. The X-15 survived it fine, but there was some cracked paint at one of the rear fin joints, denoting a significant impact. In my opinion, the Phoenix would've broken a rear fin for sure in the same case if I had built it stock.

Incidentally the above flight log author earlier launched on an I180 to ~2K and had a larger chute...here is his response for that launch: "The 50" parachute was a little large and drifted far enough". Subsequently he used the cable cutter, which had a failure.

This is one of the tricky parts of the Phoenix...being a short rocket, there is limited space for standard DD and while many have had success with JLCR and other methods (ex. cable cutters), they do seem a bit more error prone (user error, chute entanglement, etc.) than standard DD - based on what I've seen as well as my own experience. Here is an account of another 4" Patriot having only 2 out of 4 successful JLCR uses. Still, I plan on using JLCR more in an attempt to perfect its usage the best I can and at this point will likely use it first with a 50" chute.

 

[KenECoyote]

So now with the forward fins all out, I proceeded to airfoil the leading edge.

I got a Dremel miter table for the X15 wings and it works pretty well for 1/4" plywood routing.



Let me tell you...I was unsure about all that work to remove the epoxied fin just to airfoil it, but I'm sure glad I did since it looks GREAT on the Phoenix.

 

[KenECoyote]

Back to Square One...

Going back to the first concern about the narrowed root span, I've already shown you a pic of my solution (post #22). I figured the best and easiest fix is to make it a full span.

So I got some 1/4" wood and used a mini table saw to cut out 4 squares.



I then epoxied them to the rear fin and after that I also added a layer of fiberglass.

I was considering vacuum bagging and full fin fiberglassing or two layers of cloth or even rods/pins/screws, but in the end decided that wasn't necessary.

 

[KenECoyote]

Building commences!

I extended the rear slots in the bt to accommodate the widened rear fin root and while I was at it, I also widened every slot since they were awfully tight to the point that I don't believe they're big enough. Heck, it appeared that installing the fins were actually ripping the slots bigger.

Why do manufacturers make it so tight? Maybe it's more to do with variation in wood thickness?



First set glued on again!

 

[KenECoyote]

More gluing vs. ungluing now...



Please don't judge me for my shade tree rocketry tools! I had stored away a lot of my tools during my hiatus and haven't located them yet, so in the meantime I've made do with what I could quickly find. Seems to work well enough.

 

[KenECoyote]

So I've been vacillating all day on dual deploy vs single with JLCR.

I had originally planned on dd and would then be able to reuse the dd sled on other Madciw 4" builds (or use the 4" Patriot sled here); however, with this Phoenix space is lacking.

Regular dd setup isn't good since there isn't enough room for the drogue. It would've been better to set the forward CR back further for a few more inches (that WON'T be happening now lol).



I could cut the nose cone base shorter and then use the nose area and additionally inset the rear av bay bulkhead so some of the drogue chute can fit into the lower part of the av bay coupler. However this is more work again and part of me wanted to make this an easy flier. We'll see...I'll mull it over for a bit.

Otherwise the rest kind of followed the norm. I added epoxy fillets to the inside of the lower fins (both against the motor tube and against the inside bt wall).



Not the best pic, but you get the idea.

Next added the upper rail button and then I epoxied the back side of that screw (already dipped in vaseline) with thick epoxy...button isn't going anywhere without me unscrewing it.

Then I epoxied the rear CR on followed by an Aeropack retainer (using JB Weld). Rear end is SOLID.



Later I plan to do outer fillets on the lower fins using Aeropoxy or similar. For the upper fins I have something different in mind.

That's it for now!

 

[user 30299]

Here are some pictures of how I set up my JLCR for the Phoenix.





Most people end up with some added weight in the nose cone so as to improves the rocket's stability.
With the added weight the Phoenix will tend to descend quickly, nose cone first, when you use a JLCR.
Once the nose cone takes the lead, the open body tube almost acts like a drag chute. My rocket comes
down straight as an arrow; Body Tube-----Harness-----Nose Cone-->

The JLCR tether and the chute are rigged so that the chute won't push out from under the elastic band.
The tether is attached ahead of the chute and the chute's harness loop so that the chute goes
"up & away" from the JLCR. This way you won't get any entanglement.

That's a 50" Top Flight chute in the pictures.

 

[KenECoyote]

Here are some pictures of how I set up my JLCR for the Phoenix.

View attachment 549273 View attachment 549278

View attachment 549279

Most people end up with some added weight in the nose cone so as to improves the rocket's stability.
With the added weight the Phoenix will tend to descend quickly, nose cone first, when you use a JLCR.
Once the nose cone takes the lead, the open body tube almost acts like a drag chute. My rocket comes
down straight as an arrow; Body Tube-----Harness-----Nose Cone-->

The JLCR tether and the chute are rigged so that the chute won't push out from under the elastic band.
The tether is attached ahead of the chute and the chute's harness loop so that the chute goes
"up & away" from the JLCR. This way you won't get any entanglement.

That's a 50" Top Flight chute in the pictures.

Very cool! Well thought out and makes a lot of sense, thanks for sharing that!