My Madcow 4" Phoenix Build

Now that my parts have arrived I have begun my build of a Madcow 4" Phoenix rocket. What gives me the most joy in flying is the electronics, so I must make modifications to this rocket to make it mine. Since this rocket doesn't have enough room for an electronics bay - I don't want to make it longer - I am adding the Altus TeleMetrum (mine is v1.2) between the fins and motor mount. Doing this adds some weight towards the bottom of the rocket so additional weight is needed in the nose. However, I want to be able to fly a wider array of motors and have more control over the CG for these different configurations. Therefore my first task is to modify the nose cone.

First step in modifying the nose cone is to remove the bottom of the nose cone using a dremel.



I then had to make a new bottom for the nose cone. My first attempt at using the lathe failed. I had actually purchased the lathe for my wife about 10 years ago since this was something she had loved to do in one of her college classes. This is the first time it has been used! I had apparently been using the wrong tool and she got the disk made perfectly for me.



I scruffed up a washer and coupling nut (gives extra threads) and epoxied these onto the new disk.



This disk will get mounted into the nose cone (nut side towards tip - inside) and the long eye bolt can be removed in order to adjust the nose cone weight by adding or removing 2" washers. This also keeps all of the weight directly attached to the shock cord via the eye bolt so the nose cone body does not have to support the weight or shock.

In addition to sanding the fins, I did a lot of work on the motor mount prep. The ejection charge design is based off of the one used by Vern Knowles. I also decided to add a couple additional centering rings. The bottom one will be removable (this will become evident later). The ejection charge is inserted into the 2nd to bottom centering ring via the coupling nut and will be directed into the main chamber (above the top centering ring) via a 24mm tube. Drilling out the centering rings to accommodate the 24mm tube was super nerve wracking! There isn't much material left and I actually threaded the last ring for the coupling nut. Luckily everything survived and gluing everything together will make it extra strong.

Thanks for sharing. Used to have this kit, but sold it. Am interested in the build though.

I also committed to the electronics bay by using the scalpel. I used only a portion of a coupling tube since the bay lies between two of the through-the-wall fins and I want the centering rings to be adhered to the fin roots. I also removed the glassine coating from the tube and have dry fit everything to make sure it will all go together. Major kudos to Madcow for such a well made kit!

Last for tonight was a test of my guillotine fin alignment guide. Note that I have to give kudos to original creator of the guillotine fin jig but this design was just not going to work the way I wanted it to for this build - so I built my own version with my needed modifications - adjustable length, removable guillotine, and capable for use in building any diameter rocket up to 5.5". While I am proud of the modifications, I have seen the touchy threads on TRF concerning this tool and so please note that I have no intention to sell this, make it for others, give out plans, or anything else. Feel free to gander though...



Overall not bad for 2 days progress!

I like your Fin Guide. I really need to build something like that one of these days.

Rocket looks good too.

I built one of these last winter. I had to put slightly more than a pound in the nose, but it flies very well.
Looking forward to the build and the first flight.

Yesterday my back decided it didn't like me any more - still can't figure out what happened but moving became nearly impossible. So no building yesterday. Luckily it started to feel a bit better tonight and I powered through to get some rocket work done. I managed to epoxy the new disk into the bottom of the nose cone and used some dowels to provide extra security. Hopefully I will have some time to post pictures tomorrow.

I also epoxied the shock cord mounting ring into the top centering ring. The coupling nut was also epoxied to the 2nd from bottom centering ring.

Real progress also started by gluing in the first centering ring into the body tube. With this I also started to update the rocksim model.

op:

The MC Phoenix is a great kit, and the mods you are making should make it even better!

I did something similar with mine concerning the nose weight (even though for smaller motors on calm days the weight of the extra hardware was just enough to keep it stable).

One thing I would suggest is upgrading the shock cord to kevlar, my latest flight suffered a burn through on the stock nylon cord.

Mine with a LOKI H144

Fe Dude said:

op:

The MC Phoenix is a great kit, and the mods you are making should make it even better!

I did something similar with mine concerning the nose weight (even though for smaller motors on calm days the weight of the extra hardware was just enough to keep it stable).

One thing I would suggest is upgrading the shock cord to kevlar, my latest flight suffered a burn through on the stock nylon cord.

Mine with a LOKI H144
View attachment 180459

Click to expand...

+1 on the Kevlar. At the least put a Kevlar sleeve on the motor end of the nylon.

Nice picture of your good looking bird! I do have a nomex shock cord protector which I am planning to use - should I notice any deterioration I will change it over to a kevlar cord. Fe Dude - were you using a bare nylon cord or did you have a protector sleeve?

I used my Dremel sander to grind spots for the brass used with the shear pins.



I also attached the disk inside the nose cone using epoxy and some dowel pins. The epoxy was allowed to cure for about 24 hours and then the pins were ground smooth with the nose cone. Overall it turned out really nice (and still fits in the body tube).




Sent from my iPhone using Rocketry Forum

I made some major progress this weekend by getting the fins and fillets completed.



I only inserted the middle centering ring so I could add good internal fillets along the fin roots. While a 4" tube has been a "large" improvement over the LPR rockets it is still not quite large enough to put my arm down the tube with the glue bottle. So I came up with the following tool:



It is a disposable syringe (from McMaster-Carr) attached to a length of aquarium air hose. A balsa stick is attached to the hose to give it some rigidity to help aim where the glue goes. I learned the hard way (a couple of times) that the hose has to be taped to the syringe otherwise a nice stream will shoot across everything when the hose falls off!



I also managed to add the bottom and top centering rings along with the ejection charge tube. Unfortunately I figured out after everything had been glued that I couldn't get the coupling link onto the eyebolt due to the length of the motor tube. To solve this I had to take the Dremel down the body tube and cut off the motor tube. This made me soooo nervous but it worked out perfect.


(Bottom centering ring)

I also needed to route the antenna of the Altus TeleMetrum which had to go into the parachute chamber. To protect and isolate the antenna I used a stirring straw wrapped with some balsa scrap from my wife's architecture student days.



Here is the top centering ring and antenna tube.



Also did a lot of work on the electronics which will be posted soon (hopefully) when it is done.


Sent from my iPhone using Rocketry Forum

I've completed quite a bit and need to do some posting. I am nearly done painting and am getting ready to add the decals. I love the decals which came from Madcow but I need to make a few of my own to add to these. Unfortunately I can't figure out what font it is! I've been reviewing fonts online for hours now and can't find it. Anyone possibly know what font it is?

Anyone possibly know what font it is?




Sent from my iPhone using Rocketry Forum

I found it! It is "MD Military Stencil A" and can be found at https://www.tlai.com/med_des/mdsta.html. Wish it was free but oh well.

out of curiosity, how wide is the silver band at the top of the body tube? I've got a kit coming from the demented bovine, thought I would do the original color scheme(white) and mostly stock. thanks,
Rex

Rex R said:

out of curiosity, how wide is the silver band at the top of the body tube? I've got a kit coming from the demented bovine, thought I would do the original color scheme(white) and mostly stock. thanks,
Rex

Click to expand...

I don't have that one in my paint job and the Madcow instructions don't specify it. Until you mentioned it I hadn't really noticed.

well...after doing some research I found that a 3/16" wide band should be close enough(this band represents the clamp used to hold the radome in place). so now we know. thanks for looking.
Rex

mohmes said:

Nice picture of your good looking bird! I do have a nomex shock cord protector which I am planning to use - should I notice any deterioration I will change it over to a kevlar cord. Fe Dude - were you using a bare nylon cord or did you have a protector sleeve?

Click to expand...

I believe it was just the bare nylon cord that came with the kit. A kevlar sleeve will help, just make sure it covers all the way down to the attachment point. I usually tie a knot with a loop, and the sleeves have trouble fitting over the knot.

I just used the ole eyeball for the silver band on the paint job.

Make sure to post a flight report!

I added some struts between the motor and body tubes in order to make a holder for a down-looking 808 camera and to support the removable bottom centering ring. This also allows me to insert the BP ejection charge in the bottom, wire it up, and seal it off from the motor. Hindsight reveals this adds a lot of weight very low in the rocket - however there wasn't a good place to put the charge except for possibly dangling it on a long wire inside the parachute chamber. I'm not real fond of the latter as this contributed to the loss of my last rocket.



So while on the subject of my lost/last rocket - my level 1 modified Estes Pro Series 2 Ventris - I had only one ejection charge attached to an Altus TeleMetrum where the wire to the charge broke shortly after liftoff. I could actually see in the data when it broke . Well the rocket ended up hitting the earth at 150 MPH. A painful lesson was learned about taking advantage of all ejection capabilities and to not be altitude hungry. The TeleMetrum lost about a dozen components as it was located in the nose cone, but after some major surgery I got it running again! I was about to give up hope and actually ordered a replacement (don't tell my wife), but I now have two working units. Here it is in the new electronics bay.



The key has 3 positions: CPU off and pyros shunted, CPU on and pyros shunted, and CPU on and pyros armed. (I still have to add decals.) I also have two screws which can be removed by anyone to disarm the pyros should the rocket be lost (shouldn't happen if the TeleMetrum is working). I also routed a USB plug so I don't have to open up the bay to charge or configure the TeleMetrum. A very tight squeeze inside and am looking forward to the day I build a rocket with a real electronics bay!

I've also completed the painting except for the silver stripe (thanks Rex) and the decals. So here is a picture of the full rocket with my kids as the board the school bus for my son's first full day of Kindergarten and first time on the bus.




Sent from my iPhone using Rocketry Forum

Nice! Looks like the kids are excited! And interesting camera location!


Sent from my iPad using Rocketry Forum

I'm really hoping I don't melt the camera because I really like it. But if it works it is going to be a great shot.


Sent from my iPhone using Rocketry Forum

mohmes said:

I'm really hoping I don't melt the camera because I really like it. But if it works it is going to be a great shot.

Click to expand...

Unless your data card melts also :eyepop:.

I was thinking to use a strip of Aluminium foil tape for mine .
Rex

So with everything installed, minus decals and a final clear coat, the lift-off mass with a CTI 6 grain J is 3417 grams or just over 7.5 lbs. With the original kitted 36" parachute the decent rate is over 23 MPH with no wind and the chute is recommended for rockets 3-5 lbs. So I ordered a 50" parachute from Madcow Rocketry. Rocksim is showing a "Cd" for the 36" chute of 0.750. Is this still valid for the 50" chute? Using this "Cd" value for the 50" chute drops the decent rate to 17 MPH. Does this "Cd" value seem reasonable/correct?

mohmes said:

So with everything installed, minus decals and a final clear coat, the lift-off mass with a CTI 6 grain J is 3417 grams or just over 7.5 lbs. With the original kitted 36" parachute the decent rate is over 23 MPH with no wind and the chute is recommended for rockets 3-5 lbs. So I ordered a 50" parachute from Madcow Rocketry. Rocksim is showing a "Cd" for the 36" chute of 0.750. Is this still valid for the 50" chute? Using this "Cd" value for the 50" chute drops the decent rate to 17 MPH. Does this "Cd" value seem reasonable/correct?

Click to expand...

Have a look at the Fruity Chute "Iris Ultra" They are a bit pricy however you can likely get away with a 36" chute, a 48" would set your baby down real softly but it there is any wind it may be a long walk. Read the tech specs on them, I personally have about a dozen of them, both elliptical and Iris in 12" to 48" and different colours. If you do get the Iris I would also get the compact spectra line option it's just a neater bundle.

one of the hard parts about this kit, is deciding which motor to build for...I'm thinking AT 3-grain(if for no other reason than the H178 DM ).
Rex

I went into this build planning to use it for my level 2 certification so that required at least a J motor. I also wanted to take advantage of CTI's certification special and get a 6 grain case for free, allowing me to later launch a 4, 5, or 6 grain motor with a couple additional spacers. The Altus TeleMetrum is what has really drawn me to HPR, so it took me a while to figure out the best way to use the TeleMetrum in this kit that I have been drooling over for a while now. So that is where my decisions came from.