4" Madcow Phoenix- a Beginner's Guide

[d11rok]

Greetings all!
I had the great fortune of attaining this wonderful kit during BF bonanza, and came around to building it recently for a L1 certification attempt 3/20/16 (results at the end of the thread- stay tuned!)

As I was perusing the forum in anticipation of building it, I found many absolutely fantastic build threads on this exact kit, but many did not answer questions I had that were probably more beginner than compared to the expert builders that were putting DD in the nose cone, doing fancy edits to the kit using Bob Vila's own machinery and power tools, using rare materials that one can only find on peaks in the Himalayas, etc. Thus, the nidus of creating this thread; it is for those that come to the forum that are just approaching the iceburg that is HPR and building their first kit for certification, wanting to discern what will go into their most important build to date.

I learned much along the way- from all the aforementioned threads to more importantly my own experience during this build. Enjoy!

 

[d11rok]

I am going to skip the unboxing stuff and get straight to the building. However, first part is planning.

My thoughts on the early part of this build:
1) Have the aft totally flat when the Aeropack retainer was in place.
2) Have the CR's make contact with the aft and fore fins, respectively, such that they make an additional glue joint
3) In case the nylon shock cord became unusable at some point in the distant future, to have the fore CR's screw eye in a position for easy retrieval/replacement of the cord

With the complete retainer in place (not epoxied) on the MMT, it is put adjacent to the BT:


Using a ruler put through the top-most part of the fore fin slot, a line was drawn on the MMT where the fore CR should go to make contact with the fin tab of the fore wings. The hashing is where I'd later place 5min epoxy for the fore CR:


Tip at this juncture- slide the fore CR just a bit down onto the forward section of the MMT, but fore of where you want to slide it to. A fair bit of anxiety of having 5min epoxy dry whilst you attempt to jam the fore CR in place can be avoided this way.

However, all of Madcow's pieces came stock with excellent fit, and I did not have to sand at all. It slide right on without issue, and just fore of the line I had marked in the picture above. About a sitcom duration later, I put the screw eye in such that it's eye was COMPLETELY open (see in the pic below, that there is no MMT in the way of inserting a new shock cord, if needed, to fit goal #3 above). Keep in mind, the screw eye CANNOT have any parts that are wider than the CR, else there will be issues with placing the MMT assembly into the BT later. Once satisfied with positioning of it, JB weld was put on the hardware:


Lastly, confirmation of desired height of the installed fore CR, just above the forward most part of the fore wing slots.

 

[d11rok]

I should mention first that I omitted a step in the last post: both tubes were sanded with rough grit sandpaper, especially where epoxy/glue would eventually be. The body tube was filled with Elmer's wood filler, then sanded with 220-->320-->400 grit sandpaper.

Next step is to join the two tubes. The aft CR is merely placed on the aft part of the MMT, followed by placement of the motor retainer. Using a long wooden dowel, 5 minute epoxy is smeared in the spaces between the fore fin slots, just aft of where the fore CR will go. Then quickly (again, beforehand making sure the fore CR slides in easily), the MMT with its installed fore CR is shoved through the smear of epoxy and into position. The tubes are positioned upright, and the aft CR is ensured to be flat against the retainer, forcing the MMT to be central. From the top, more epoxy is put on a wood dowel and filleted about the outside:


(Note: prior to this, the shock cord was installed after the JB weld had dried. the loose end was then taped to the main end, and the entirety shoved into the MMT for later use. Tip: ball up some tape and put it into the aft end of the MMT to hold the cord into place until later).

While the epoxy was curing, I got to work on the aft fin set. Going across the grain, thinned Elmer's wood filler was painted onto both sides of each fin. I tend to paint this on quite thick, and then I find you only need to go through the sanding process once. The fins were then placed between 2 pieces of wax paper with weight on top (to prevent warping from the water needed to slightly thin the filler). Another sitcom duration later, the filler is dry, and sanding proceeds as follows: 220-->320-->400-->600. Below is an after and before picture:


Once all were nice and smooth, they were all trialed through the aft fin slots. With an eye on the straightness of them, CA was used to tack down the fins. 5 minutes later, internal fillets were placed with wood glue using a small diameter wood dowel. Ensure the internal fillets are dried before moving to the next fin. The aft fins were all straight; the camera angle is a bit skewed:


While those were drying, 2 "jigs" of 2 straight popsicle sticks glued together were made, as was filling and smoothing out the fore fins.



With the ends of the "jigs" clamp to the fore of the aft wing and the other ends hovering over where the fore fins would be, glue was applied to all contact surfaces of the aft fin, including a heavy dose of wood glue on the tab. As the fin was passed through the slot and the 2 jigs, the excess wood glue would leak down onto the MMT, forming an internal fillet rather easily. The other clamp was placed on the other end of the popsicle sticks onto the fore fin, ensuring absolute straightness of the 2 fin sets. This was repeated all around, then additional internal fillets were placed, making sure extra glue ran down onto the fore CR, contacting the foremost part of the fore wings.

After the wood glue was dry:

 

[d11rok]

Next up is the external fillets, but first, filling/sanding the area between the 2 fin sets. This area is where the fin tab of the aft fin is, just behind where the fore fin overlaps it. There may be some step-ups here, and thus the filling required. Nothing different here than usual filling/sanding process:


Let the fun begin! I find the blue painters' tape is the go to for large masking jobs. Mask the aft fins last, as it would be better to remove that mask first, as it is a smaller area to control should something go awry. Also, put some tape down the gap between the fin sets, as during the process of forming the fillet (I used another popsicle stick), that is where the glue runs. Have plenty of paper towels handy.



And with fillets awaiting drying:

 

[danielsadjadi]

Excellent fillets. Is that wood glue?

 

[kcobbva]

Next up is the external fillets, but first, filling/sanding the area between the 2 fin sets. This area is where the fin tab of the aft fin is, just behind where the fore fin overlaps it. There may be some step-ups here, and thus the filling required. Nothing different here than usual filling/sanding process:
View attachment 285809

Let the fun begin! I find the blue painters' tape is the go to for large masking jobs. Mask the aft fins last, as it would be better to remove that mask first, as it is a smaller area to control should something go awry. Also, put some tape down the gap between the fin sets, as during the process of forming the fillet (I used another popsicle stick), that is where the glue runs. Have plenty of paper towels handy.

View attachment 285814

And with fillets awaiting drying:
View attachment 285815

Wow, as previously asked: Is that woodglue? That looks really great for fillets of woodglue! How did they dry? I know most of my wood glue tends to shrink a bit. I'm a convert and went to RocketPoxy for darned near everything. Just LOVE the way it sets up. But if that's woodglue and it dries like it looks; you've got a VERY steady hand. Also, looking at the previous fin placement, really looks like you have it rock solid! You need to put one of Andrews 808 #16 camera shrouds on the side of the aft frame, and get a camera of course. That'll tell you just how true your fins are. I bet that doesn't spin at all on the way up!!! VERY nice looking build so far!

 

[dixontj93060]

Looks like RocketPoxy to me.

 

[kcobbva]

One other thing. I noticed you had the tubular nylon used with all the Madcow rockets. I put a nomex sleeve over my aft in my L1 to ensure it doesn't burn over time. Might be worth looking at. Also if you can reach it, might also be worth adding a quick link to that eyebold in the aft to quickly remove the line. I didn't do that in my L1, but absolutely did that in my L2. Also added them to both L1 and L2 on the E-bay and made it so much easier than the tie on method that is supposed to be done with the madcow out of the box.

 

[d11rok]

Daniel and kcobb,
Thanks for the comments and thoughts! Indeed, those fillets are of titebond II wood glue. The key is to put enough glue between the tape lines that it touches the tape on both sides, then with a popsicle stick placed at about 30degrees to parallel run it down. This obviously leads leads to a lot of glue runoff coming down the gap between both sets of fins, and thus the need to place tape there and having lots of paper towels at the ready. About 4 popsicle stick runs through, the excess glue that is pushed onto the tape making the fillet decreases enough such that it doesn't run back into the fillet. That is when to pull both sides of the tape off at the same time, starting fore, and pulling straight up

In regards to how they dried: in about an hour or 2, the periphery of the fillets went from the light yellow opaque color you see above to the more tan and clear color associated with it drying. That is when I was assured the fillets were dry enough to work on another set. In regards to it shrinking, I did not see any effects of that if it did, as I imagine it dries from peripheral to center superficial to center deep. Any contraction therefore should be focused on the bonding line, with a rather narrow angle of effect and limited contraction. The already placed internal fillets should hold the fins steady

 

[d11rok]

One other thing. I noticed you had the tubular nylon used with all the Madcow rockets. I put a nomex sleeve over my aft in my L1 to ensure it doesn't burn over time. Might be worth looking at. Also if you can reach it, might also be worth adding a quick link to that eyebold in the aft to quickly remove the line. I didn't do that in my L1, but absolutely did that in my L2. Also added them to both L1 and L2 on the E-bay and made it so much easier than the tie on method that is supposed to be done with the madcow out of the box.

Kcobb,
I will certainly have to look into that nomex sleeve! I do have a quick link in place, but not at that location. Will update this thread later in the day with the hardware bits.

 

[dixontj93060]

Those are the nicest wood glue fillets I have ever seen!

 

[kcobbva]

Those are the nicest wood glue fillets I have ever seen!

+1!! Absolutely.

 

[d11rok]

Thanks much for the kind words!

After the external fillets completely dried (that is, I was able to see the contact point between the fins and BT), I stood it upright and couldn't help but take a picture with the NC on, as now the shape of the rocket is complete:


The aft CR is then installed. JB weld is smeared on the exposed sections of the aft fin tabs, as well as just aft to those in a circle inside the BT and on the MMT, so that when the aft CR is pushed down onto the aft fin tabs, the internal fillets will be already made. Shortly after the CR is in place, the motor retainer is also JB welded on. The aft CR then has JB weld external fillets:


Attention is then turned to the nose cone and necessary added weight. Throughout the build, I weighed and tabulated each individual piece of the build. This data was entered into the provided rocksim file by Madcow, and the additional weight that was composed of glue/epoxy was added diffusely throughout the piece itself. Using this data, about 434g of NC weight is needed to put the CG about 1.33 calibers fore of the CP (where did that caliber number come from? Given that it was on the "stubby" side of things with the fins about 50% up the BT, I chose to put the caliber closer to 1 rather than closer to 2, and if higher motors are flown in the future, I have room to go).

Lead shot is measured, and about 4% waste is added (ie: lead shot I anticipate being stuck in the epoxy slurry within the cup rather than going into the NC) to make the weight very close to 1lb. Neat how things sometimes work out, isn't it?


I had made another thread asking questions of how best to go about adding weight (and thanks again for all your comments there). I decided to go away from my idea and stick with the "tried and true". I purchased 1/8" inch brass rod from Home Depot, which will act as cross struts to which the epoxy-lead shot slurry will not breach when exposed to high G's. Should it breach, the rocket would likely become unstable and who wants an unstable rocket these days?

2 1/8" holes were drilled straight across from each other at about 5cm aft of the tip of the NC, and 2 more 1/8" holes were drilled straight across from each other but perpendicular to the other holes, about 4.5cm aft of the tip of the NC. the brass was then shoved through and clipped. Thin CA was then put around each strut's hole and allowed to dry overnight.


Some cool water was placed in a bucket and the NC was introduced, and no bubbles were noted, so I was convinced none would get in during the introduction of the epoxy. Why care about the waterproofness of the NC you ask? read later

I had rocketpoxy laying around for when I get to the composite builds, and this seemed to be the longest cure time epoxy I had laying around, and thus this was mixed together and slowly lead shot was added, such that a thin layer of epoxy covered all lead shot balls. I did not realize that the epoxy would be as thick as it would be, and if I had to do this again I would search for a thinner epoxy for sure to that I can just pour it in. However, I was able to find a narrow snout funnel, tape it to the snout of the NC, and with the remaining piece of the brass rod, the quite thick epoxy-lead slurry was jammed through and dropped into the tip of the NC whilst being suspended into the bucket of cool water. My arm got quite the exercise, but finally enough of the slurry dropped to the tip, covered the brass struts, and was left to cure for 36h.

So why care about waterproofing the NC, and why even place the thing in water, you ask? When the epoxy is drying, it is an exothermic reaction, which produces heat. That heat could deform the NC, and who wants a deformed NC these days? Thus, the NC is placed in cool water to act as a heat sink. If water got into the NC and interacted with the epoxy, the bonds of the epoxy to lead and to the NC would weaken substantially, leading to increased chance of the weight not staying put.

 

[d11rok]

As the epoxy was curing, it was time to get to the fun part- finishing the rocket! As mentioned in my cosmic interceptor thread, I am a big fan of the Rustoleum paint/primer in one combo. Since then, however, I have used and greatly liked the Rustoleum filler primer as well.

The color scheme for this rocket was not going to deviate much from the gray body/blue stripe scheme. However, as I was planning in my head how to go about placing the stripes, another Phoenix build thread (will cite here later) mentioned using colored electrical tape for the stripes, and so I figured I'd give that a whirl.

Step-by-step of the finishing:
1) Using a dishwashing sponge, scrub the entirety of the BT and fins to ensure no oils have been deposited on it inadvertently. These tend to lead to issues with the paint/primer sticking, and leads to some aesthetic imperfections
2) Two coats of the Rustoleum filler primer (link here https://www.homedepot.com/p/Rust-Ol...Primer-Flat-Gray-Spray-Paint-249279/202097276) were sprayed about 5 minutes apart from each other
3) 400 grit sandpaper was used throughout the entirety of the BT and fins, but concentrating along the fillet surfaces.
4) Using paper towels, the entirety was dusted off, leading to a very smooth surface:

You'll note in the picture that the NC has been freed of its water , but I am still allowing it to dry more

5) Two light coats of Rustoleum Gloss Winter Gray (link here: https://www.homedepot.com/p/Rust-Ol...-General-Purpose-Spray-Paint-249089/100670423) were sprayed on the BT and fins, about 5 minutes apart. After doing so, I had contemplated going back and doing a third coat, but out of an abundance of caution, chose not to. The first 2 coats had gone on without a glitch- no runs, very minimal heterogeneity of the paint, no crinkles- and I did not want to mess with that. I was overall quite pleased with the result:

 

[d11rok]

After the BT had been painted and awaiting to dry, I had been working on the NC.

Step by step finishing of the NC:
1) Clip brass rods as close to the surface, then file without damaging the NC
2) Xacto the plastic bond lines
3) Sand entirety of NC with 100 grit sandpaper. I find this leads to a nice "uniform roughness" of the NC which will lead to better capture of the filler primer, as well as homogeneity
4) Mask off the shoulder of the NC. I use blue painters tape at the foremost shoulder, then tape a plastic bag over the rest, as you'll see in the picture
4) Similar to the BT, the NC got 2 coats of the filler primer separated by about 5 minutes.
5) Sand the NC with 400 grit sandpaper
6) Similar to the BT, the NC received 2 coats separated by 5 minutes of Rustoleum Gloss White Paint (link here: https://www.homedepot.com/p/Rust-Ol...-General-Purpose-Spray-Paint-249090/202071352), and was allowed to dry via clamping the aforementioned plastic bag to the table and letting it overhang:


After 24h, the NC was popped on top of the BT, and a near-finished picture shows the following:

 

[d11rok]

In the background of the above post's 2nd picture, you'll notice 2 estes rockets. These are the projects from the "Battle of the Probes" build thread in LPR. The project was put aside temporarily for this project, but shall return in short order. And yes, it appears that this was a shameless plug- my apologies.

 

[d11rok]

At this point, I had little time to completely finish the rocket prior to the certification attempt. However, I wanted to get all the hardware installed and the holes drilled.

A bit below where the shoulder of the NC would be, I drilled 2 1/8" diameter holes, one on each side, to allow venting of the BT. Why you ask? As the rocket ascends higher, the pressure on the inside of the BT becomes increasingly greater than the air pressure. This pressure gradient can lead to NC ejection when you absolutely do not want it, and possibly leading to a zipper. Who wants a zippered rocket these days?

And now my rail button thoughts. The rail buttons that came with the kit are fantastic and simple- the button and a screw. However, I feel (and I have no evidence to back this up) that there a couple things missing which I addressed in this build:
1) having just a screw as the point of contact through the BT can lead to much torque on that section of BT, possibly leading to local trauma and need to repair later. Would there be a way to decrease this?
2) My fore rail button will be at the CG (for both launching rationale and to easily identify where the CG is). However, this ended up being within the parachute bay, and I certainly do not want a sharp screw anywhere near the parachute as it ejects. Can I easily and non-permanently cap that, without protruding too far into the bay that the shock cord would get caught?
3) I wonder if the rail button spinning on the BT creates enough friction in the short term to decrease the acceleration off the rail, and in the long term eat away at the BT.

Walking through Home Depot (which is a frequent occasion for me), I came across the solution to all 3 issues, and will share them here:

For issue 1 and 3 above, I came across these washers:

They sit snug on the BT with a somewhat rubberized grip, but the top of the washer is metal and convex in shape. This would prevent too much screw torque on the BT, as well as provide a nice surface for the rail button to slide on to both decrease friction (I would posit the coefficient of friction between the button and metal is less than the button and cardboard) as well as prevent damage in the long term to the BT from the rail button spinning. Yay!

For problem #2, I came across rubber stoppers, that were cut in half with a razorsaw, keeping the wider half and screwing that into the loose end of the screw. The 2nd picture shows the complete assembly at the aft rail button- the same assembly is in the parachute bay:


With a day left until certification attempt, I pack the decals and electrical tape, and head to the hotel

 

[d11rok]

Upon arriving at the hotel, I considered myself lucky while bringing the rocket in to not have the secret service or FBI called haha.

Anyways, I wanted to put a thin layer of tape on the fore of the BT to bring out the NC better. Fortunately, across the street from the hotel was a West Marine store, and I picked up this: https://www.westmarine.com/buy/seafit--premium-striping-tape-1-4--P000224545 in black.

The nice part of that tape is that there is a paper backing, which allows you to take your time with the application of the tape, not having to worry about the tape sticking to everything.

The blue electrical tape (https://www.homedepot.com/p/3M-Scotch-3-4-in-x-66-ft-35-Blue-Electrical-Tape-10836-DL-10/100140100) was then put into position as pictured on the Madcow instructions. I wanted to have the blue stripes between the fore fins symmetric, and thus the linear decals associated with those blue stripes were measured as a new unit- "1 hotel room key length"- from their respective start of the fore fin. There were multiple mistakes when placing the blue electrical tape, but fortunately it was able to be removed without removing the paint underneath. I Xactoed the length of electrical tape at the fillet lines, and this was done easier than anticipated as well.

The remainder of the decals were placed (the waterslide ones, and although there were many, it was fantastic placing each one of them, as the rocket continued to gain realism.

Finally, the morning prior to launch, the completed project! (note the nice hotel room carpet! haha)

 

[d11rok]

The launch day came 3/20/2016. What a beautiful, cloudless day it was! After finally figuring out the intricacies of an Aerotech reloadable, the launch went rather well!



The delay was a bit more...delayed than I would have hoped, but no damage at all to the rocket. L1 certification achieved!

 

[Coop]

Excellent! Nicely done! Perhaps you mentioned, but I missed it in my after-work fog... what motor did you use?


Later!

--Coop

 

[kcobbva]

The launch day came 3/20/2016. What a beautiful, cloudless day it was! After finally figuring out the intricacies of an Aerotech reloadable, the launch went rather well!

View attachment 285930View attachment 285931View attachment 285932

The delay was a bit more...delayed than I would have hoped, but no damage at all to the rocket. L1 certification achieved!

Congratulations Dan!! I hope you are still on Cloud 9. You deserve it after that build. VERY nice indeed! Cannot wait to share L2 success stories with you!

 

[d11rok]

Coop,
Thanks much! I used an Aerotech H130W, drilled to 8 seconds.

Excellent! Nicely done! Perhaps you mentioned, but I missed it in my after-work fog... what motor did you use?


Later!

--Coop

 

[d11rok]

Congratulations Dan!! I hope you are still on Cloud 9. You deserve it after that build. VERY nice indeed! Cannot wait to share L2 success stories with you!

Thanks again Kevin. It was a fun one for sure! I'm looking forward to your rocket completely nailing the flight.

 

[VAXman]

Upon arriving at the hotel, I considered myself lucky while bringing the rocket in to not have the secret service or FBI called haha.

Only if the upper two stripes were yellow (active warhead).

In my photos here on this forum is a picture of me with my Madcow Phoenix. I used Monokote (the thinner iron on stuff) for my stripes. I used chrome Monokote for the stripe below the nose cone. The entire rocket was then clear coated using TopFlite LustreKote clear.

I had to put a pound of sea pearls in the nose of my Phoenix which had me concerned but I've seen many other reports now that have done pretty much the same. It seems a waste of APCP to have to boost that much lead toward the sky. I epoxied the sea pearls into place by pouring finishing epoxy in with the pearls; then, a layer of 30 minute epoxy. The whole nose weigh was secured thereafter by drilling through the nose cone and into the lead/epoxy. I tapped the whole for 1/4" 28TPI and then introduced 3 1" long hex set screws (like these: https://i.ebayimg.com/images/g/XFEAAOSwdvpWEfqM/s-l300.jpg) to hold things in place. These were then CAREFULLY ground to the nose cone contour using my dremel tool. You'd never find where the studs are located unless you had a magnet.

 

[Bat-mite]

Congrats!

For as much as people keep saying the hobby is dying, it seems like there are lots of people certifying all the time.

 

[CORZERO]

Nice job! What was your final loaded weight?

 

[d11rok]

Vax,
I do believe I saw your rocket somewhere along the way and was in awe! It's likely where I got the idea for the thin tape (albeit, not monokote, but will look into that stuff later).

The sea pearls idea is interesting. Why did you go with that instead of lead, as you would need to use the same weight, and possibly more given that it would be less dense and take up more volume in thee nc)?

Bat and corzero,
Thanks much! The final loaded weight was 4 lbs 7.5 oz

 

[VAXman]

I live on the NJ shore, so sea pearls are easy to come by in the local diving/marine shops. They're also smaller, so less space. Besides, trying to purchase anything gun related in the Peoples Republic of New Jermany is a humiliating experience. It took weeks, and far too many signature forms and ID, just to get 1lb of FFFFg!

 

[VAXman]

4lb 7.5oz ... with motor? That's about 2kg. Mine, with CTI 3 grain case and a 247H143-13A, weighs in at 2.6kg.

 

[VAXman]

FYI, MonoKote has a heat activated adhesive. You need an iron -- hobby stores sell a special iron for this -- to adhere it to a surface you wish to cover.