Madcow Mini DX3

I am planning a Missileworks RRC2+ with either a 9V or 2-cell small Lipo for power in my Mini Frenzy. I really like how simple the RRC2+ is.

My Mini-Frenzy has a Eggfinder Quantum and a 2s LiPo for DD.
The sled mounts on one all thread, and the altimeter sits between the sled and the other all thread. 38mm bays are very tight for space.

The Missileworks RRC2+ looks very good, and has a good price. Thanks. Looks like when I get to that point, I will be breaking out my jeweler's goggles in order to work on things. Caley Ann

I like my rrc2. Simple to setup and use. I've used a variety of methods to turn on altimeters. Wiring a switch between the altimeter and positive side of the battery is a good way to do it, but raises issues of where to mount the switch, which switch to use, how to get that tiny screw driver in there, etc. the simplest, and by far my favorite method is called "twist and tape". Cut the positive wire, and stick the ends out a vent hole. When on the pad, twist the two wires together, powering on the altimeter. Then tape the wires to the body of the rocket. Sounds caveman, and is, but it works and I've done it a handful of times past the speed of sound.

I received the Apogee EBAY today, and was disappointed that the tubes don't match the Madcow DX3. The EBAY tubes are .75mm too big. But no need to panic. I will use the tubes that came with the DX3, and fix those up so that the EBAY plywood will go inside. I just need to reduce the diameter of the four discs used at each end of the EBAY. I've done quite a bit of building of radio control and free flight airplanes, so these modifications shouldn't take more than patience. Once I get the EBAY working to where I can put it in and take it out, I will order the altimeter and battery, and of course, I will have to order the electric matches, black powder, and all the other little things that are required for dual deployment functionality.

From what I get on the specs of the RRC2+ altimeter, I will have to mount the altimeter on one side of the sled, and the battery on the other, as the altimeter is too long otherwise.

I finally got the fins seated, and now I get to try using RocketEpoxy to make the fin fillets. I've been told this epoxy is very good for this purpose. Caley Ann

Caley said:

I received the Apogee EBAY today, and was disappointed that the tubes don't match the Madcow DX3. The EBAY tubes are .75mm too big. But no need to panic. I will use the tubes that came with the DX3, and fix those up so that the EBAY plywood will go inside. I just need to reduce the diameter of the four discs used at each end of the EBAY. I've done quite a bit of building of radio control and free flight airplanes, so these modifications shouldn't take more than patience. Once I get the EBAY working to where I can put it in and take it out, I will order the altimeter and battery, and of course, I will have to order the electric matches, black powder, and all the other little things that are required for dual deployment functionality.

From what I get on the specs of the RRC2+ altimeter, I will have to mount the altimeter on one side of the sled, and the battery on the other, as the altimeter is too long otherwise.

I finally got the fins seated, and now I get to try using RocketEpoxy to make the fin fillets. I've been told this epoxy is very good for this purpose. Caley Ann

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While its not a RRC2, the setup I used here is one way of mounting the alt in a 38mm bay, part of the difficulty of small diameter Av-Bays is the fact you may not have enough room to mount stuff on both sides or between the all-threads normally.

The only way this little EBAY will work is if I can mount things on both sides. It is an all ply EBAY with the exception of a few metal parts. I don't have to worry about the big metal bolt that runs through something like yours.

I've another question on ejection charges. I've watched several videos, and seen things done differently in a few. In one, the ejection charge canisters are mounted on the EBAY ends. I've also seen one instance where the ejection charge is placed deep in the main rocket body tube below the drogue chute, and the other is mounted on the top end of the EBAY.

Does it really matter where the ejection charges are mounted, as long as the chutes and their associated lines and shock cords are protected by Nomex cloth?

Another question: If I can mount the ejection charge reservoirs to each end of the EBAY, is there a permanent solution for those resevoirs? It looks like the alternative is purchasing lots of little plastic canisters, or using rubber glove fingers. A permanent solution that looks nice is always preferable. But I do want to keep the rocket weight down. I don't want to end up with another Stretch Blobbo that was so heavy, it basically is limited to three engines, that right now are not available online. Caley Ann

Caley said:

I've another question on ejection charges. I've watched several videos, and seen things done differently in a few. In one, the ejection charge canisters are mounted on the EBAY ends. I've also seen one instance where the ejection charge is placed deep in the main rocket body tube below the drogue chute, and the other is mounted on the top end of the EBAY.

Does it really matter where the ejection charges are mounted, as long as the chutes and their associated lines and shock cords are protected by Nomex cloth?

Another question: If I can mount the ejection charge reservoirs to each end of the EBAY, is there a permanent solution for those resevoirs? It looks like the alternative is purchasing lots of little plastic canisters, or using rubber glove fingers. A permanent solution that looks nice is always preferable. But I do want to keep the rocket weight down. I don't want to end up with another Stretch Blobbo that was so heavy, it basically is limited to three engines, that right now are not available online. Caley Ann

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Best case is that the charge Pushes the chute Out of the tube instead of blowing it further down into the tube.
This is really important for the main. Fortunately, putting charges on the forward ebay lead does this anyway.

Now if you put the charges on the aft ebay lid, it'll blow the drogue further into the body tube. Technically this isn't optimal, but the drogue is small and is easily pulled out by the harness when the airframe separates. Some my say you should always put the charge below the drogue so it pushes it out, but I have no plans to do this in my builds.

Caley said:

Once I get the EBAY working to where I can put it in and take it out, I will order the altimeter and battery, and of course, I will have to order the electric matches, black powder, and all the other little things that are required for dual deployment functionality.

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Also, blackpowder may be harder to find than just ordering it.
Your best bet is a Bass Pro shop to get Goex FFFFg. May be lucky and find it from a local gun place that deals with muzzleloaders frequently

That's what I thought. I will be putting the drogue chute charge down in the body below the chute to ensure it is ejected.

I live in a somewhat wild west environment. The towns have their yearly celebration of founders day, etc. And I have two gun shops in the area. I might get lucky and find 4Fg black powder. If not, I will have to order online like I do everything else, as where I live doesn't have a whole lot more than the necessities of life available. Caley Ann

Hi Caley. On some of the smaller diameter rockets, we like to use rail guides vs the buttons because trying to get inside the tubes to ensure the backing won't interfere with the parachute or shock cords can be difficult. My little boy and I doing that on our 1.6" madcow frenzy's right now. Might be worth looking at as well: https://giantleaprocketry.com/products/components_launch_systems.aspx#Acme_Conformal_Launch_Guides

Either way, as many have said, moving away from rods is a good thing. They tend to stick or whip and rails are just more sturdy and often taller so you come off the pad at a higher velocity...a good thing.

kcobbva, Thanks so much. It was suggested somewhere else that I do this because of the difficulty with installing rail buttons. I purchased Apogee Rail Guides. Had no idea that there were other kinds, or I would've gotten those you just linked. Much lower profile. I can only hope that what I have will work.

I found the altimeter and lipo battery set I had wanted, so I ordered those. But I still cannot get the matching charger. So I have to wait until I get the charger so that I can fly this little beast.

One thing about how small this model rocket is, is I will have to borrow someone's eyes to help me track it. From what I have seen with these little rockets, they fly fast, and fly high. That is one reason I really want the dual deploy. Hopefully with dual deploy, it won't drift off into the sunset never to be found. Caley Ann

rharshberger said:

My Mini-Frenzy has a Eggfinder Quantum and a 2s LiPo for DD.
The sled mounts on one all thread, and the altimeter sits between the sled and the other all thread. 38mm bays are very tight for space.

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Wow no kidding they are tight. Well done Rich. Erik and I are keeping ours easy as that's way above his head. But I bet that flies awesome.

kcobbva said:

Wow no kidding they are tight. Well done Rich. Erik and I are keeping ours easy as that's way above his head. But I bet that flies awesome.

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First flights looking to be June launch.

I managed to modify the Apogee BT-60 sized EBAY to fit my Madcow Mini DX3. It isn't perfect, but should be functional.

I am slowly putting a laundry list of things I will eventually need.

One of those is the 4fg black powder. I checked the two gun shops in my area, and they don't carry or sell it. I checked online, and it seems the minimum is five cans, plus their handling fee/postage and hazardous handling fee. I am wondering just how I will obtain even a small quantity of this black powder. I could never need five cans, let alone one, as I just won't be flying more than two flights a month, weather permitting. Does anyone have any suggestions on how to get a few ounces of the stuff? The only thing I can think of is to ask around my new club, and see if any member is willing to sell me a few ounces.

I am planning on running wires from the Easy Mini altimeter to connector blocks on each end of my EBAY. I can then connect the ematches to those connector blocks which have screws to hold the wires.

Another roadblock I have is the lipo battery charger Altus Metrium makes is sold out, and until they distribute more, I am dead in the water, as I have no way to charge that little lipo. Any other alternatives that use the small white JST plug?

Also, I remember a couple of you mentioning that you are flying something about the size of my Mini DX3 with dual deployment. What size drogue should I purchase for this tiny rocket? My main is 18 inches diameter, which I am hoping will be enough to slow it to a gentle landing on the dry lake bed. Caley Ann

Just about any hobby shop will carry a lipo charger and jst plug for your battery.

Not sure if you have a basspro anywhere near but that's where I got mine. Else road trip.....i missed if you said any clubs launched in your area. My folks always offered some to me until I found my own.

Not cost effective per-gram, but if you only need a tiny bit: https://www.rocketmotorparts.com/Ejection_Charge_12-Pack/p1577809_16501630.aspx

kcobbva, I live in the high desert of southern California, so no fishing shops here. We do have lots of churches, bars, tatoo parlours and barber shops, and stuff like that. Might be because of the Marine Base. But if I need something special, I generally have to drive over 100 miles to the nearest big metropolitan area. We pretty much just have sand, rattle snakes and coyotes. ;-)

dhbarr, Many thanks. If the club I just joined, Rocketry Organisation of California has a member that can sell me some, I will go that way. Otherwise, the link you provided will probably keep me in business for a year with my mid-powered rocket.

Haven't heard on my question about a drogue chute size, but I am guessing about 8-10 inches.

My work, like I have done on my RC and free flight airplanes is very slow and methodical. I tend to take lots of time making sure I am doing things correctly, especially on my first attempts at something new. Hopefully I will have something that looks like a rocket to take of picture of, eventually. Caley Ann

I have managed to collect roughly 14g of bp by flying oddrocs(saucers pyramids) that don't require an ejection event for safe recovery as a bonus I don't usually have to walk very far to retrieve them.
Rex

Caley,

I am sure that if you attend a ROC launch, you can walk around in the morning and see if anyone has a small amount of 4F they can "donate" to your cause. For your small bird, a film canister or medicine container will go a long way.

I also suggest checking out John Coker's website at www.jcrocket.com -- lots of tutorials on how to do various things, including what you are attempting to do. Be sure to check out the "how-to" link on the left column.

These articles stand out to me: https://jcrocket.com/basic-wiring.shtml and https://jcrocket.com/electronic-recovery.shtml

You are asking lots of questions, and that is great. Best way to learn. In this hobby, the stupidest question is the one not asked. Don't be afraid to venture out to a ROC launch with your rocket and see if you can hook up with someone who is willing to walk you through the steps for success on your rocket.

Also I think you asked about connections for the av bay to charge interface. I use terminal blocks similar to these https://www.missileworks.com/store/#!/2-Point-Bulkhead-Terminal-Block/p/24591229/category=5760489 and https://www.missileworks.com/store/#!/2-point-Euro-Style-Terminal-Block/p/33363809/category=5760489. The first option I typically use for the smaller diameter rockets since they take up less space. I solder leads to them first, and cover them with shrink wrap. Then I feed them into holes drilled in the bulkhead, then epoxy the terminal block to the bulkhead (make sure you don't get epoxy in the terminals!) and also ensure that the backside of the bulkhead is sealed with epoxy where the holes pass through.

I also use the tips of nitrile gloves for my ejection charges. It's simple, takes up no space, and a box of gloves will last you YEARS.

I can post photos if you're interested of my setup(s). I will have to do that this weekend.

Have fun!
Mike Walsh

Hi Mike, You sure covered a lot. Thanks.

Yes, I found John Coker's website and videos, and have looked at many.

I would have not thought of covering the exposed terminal block. I had thought of the hole the wires go through the bulkhead, and had planned on filling those. I would imagine that if you put a thin coat of epoxy on both bulkhead sides, that would facilitate the cleanup of the smoke damage to them.

I purchased one of the terminal blocks Apogee sells, as I could not locate anything else I like. Like one person said earlier, I am not totally familiar with some terms, and my Googling skills suffer because of that.

Right now I am waiting for my next Apogee package before moving on with the build. Looks like I won't maiden the bird in the next gathering of ROC.

Speaking of black powder. I will just purchase one set of the little canisters from the website someone provided a link to. I am hoping the small quantity does not require a hamat fee. If so, I won't be purchasing. I'll just have to find another source somehow.. I am figuring that most of the charges required are going to be somewhere between .2 and .4 grams, as the payload sections for this bird are very small. Caley Ann

More progress on the Mini. I finally got the EBAY built and populated with the battery, switch and altimeter. I've come to the conclusion that I need to keep this very simple because of the small size. So I will just be running the e-match wires through a hole in each end, and using clay or some other such thing to block the remainder of that hole. I will be using the latex gloves to put the black powder and e-match end in, and using a tiny elastic to close it.

OK, another question. When I purchased this kit, I went with the fiberglass nose cone. It is open at the end. I had planned on using the ply disk that would have gone in the upper part of the rocket body, and plan on placing it in the open end of the nose cone. My question is, should I just glue the disk in, or should I figure out a way to make it removable for possible use by other electronics?

My last build was a Stretch Blobbo. I painted it, but the paint is not adhering to the plastic nose cone very well. Is there a secret to getting the paint to stay put on things like plastic and fiberglass?

I will eventually be having to ground test my dual deployment system. Exactly how is that done without using the altimeter. Since I do not have a vacuum chamber to simulate altitude pressure differences, using the altimeter seems to be impossible.

I think those are all the questions I can think of for now. I need to order the black powder now. I am going with the prepared batches the RCS Store has. With this little rocket, I may be able to get two flights out of each vial. Caley Ann

It's easier to paint fiberglass than plastic nosecone.

I have to really rough the plastic and use a few coats of primer to promote paint adhesion.

For ground testing, you could run a normal.launch control let lead to the ematch ematc through the vent hole. John Coker just sticks the wires on a 9-volt from like 3' away (if that far even).

If you want to use the alt, tape a vacuum to the vent hole, turn it on, then turn it off.

Nytrunner, You said vent hole> Exactly where do we put these vent holes. I understand they allow the air within the rocket body to equalize with the outside air. I have a hole in the middle part of the rocket where my EBAY switch is, but running the ejection charge igniter wire through that would cause problems with the top part of the rocket being ejected from the lower section, pulling the wires away from me. So, I get the feeling that I need a small hole in the lower rocket body somewhere below the body coupler to run that igniter wire through. I am guessing that would also apply with the middle section of the rocket.

Since I am probably classified as a "Chicken", I will be extending the wires for these tests to about 10 or more feet, just in case something blows up.

I know all I wrote probably sounds dumb, but this is my first rocket in almost 50 years, and to boot, it will be a dual deploy. I'm kind of diving off the high dive, without trying the low dive again, first.

Now for another question. First of all, this Mini DX3, while capable of launching with a Level one motor, and being used for certification, will not happen. I want this purely as a mid-powered rocket to get my tootsies wet in the hobby. But I would like to go to reloadable motors. I think the 120mm long or greater casings for the 29mm motors are considered L1 casings. Is that correct? Those below are mid-powered casings. I get the feeling what I just said is all wrong, so I need help in choosing a motor casing and enclosures for this rocket. I would prefer to keep the highest flight below 2000 feet, otherwise I probably am going to need tracking devices, which I cannot afford right now. I am not certain I am committed totally to resuming the hobby with full enthusiasm.

Right now I have purchased a pair of single use motors Econojet F20-7W, which was recommended for this model, which should get it well above 1500 feet. Since I am using dual deploy, I am guessing I need to remove the ejection charge from these. If I remember correctly, someone told me to remove the red cap, and pour out the black powder, then install the cap back in place. Since I don't know just how far the model will drift up after motor burnout, I cannot be sure leaving the ejection charge in would be smart. I know someone said to just leave it in, and when it went off, if would create a smoke trail to follow.

I got the idea about sandpapering the nose. I will give that a go. Too bad the paint job will look rough. Anyway, that is again enough questions. I hope I will learn enough to actually be smart enough to do all of this sometime in the future. Caley Ann

Run your wires out the vent hole in the avbay. Yes, the top part will get ejected away from you, so just attach your igniter clips so the wires pull free from them.

Get the Aerotech 29/40-120 casing. It is the most versatile casing for mid-power with the greatest variety of loads ranging from E through G.

Here is a video of me testing my Mini Frenzy's charges. For the drogue charge, I ran the ematch wires out the vent holes in the avbay. For the main charge, I ran the wires all the way through the avbay and out the hole that the drogue charge would normall occupy.

[video=youtube;APNxgf1lU00]https://www.youtube.com/watch?v=APNxgf1lU00[/video]

Ryan, Thank you so much. I guess that if I have enough slack in my extended wires, I shouldn't have any problem with the test. Like the video of the test. I am guessing that my guessimate of .3 to .4 gram of black powder was a bit low for the drogue chute compartment. Might be OK for the main.

Finally got most of the build done. I still have to decide on how to decorate it. Right now it is a few ounces under projected weight given by the instruction manual, but that will change when I install the two chutes and Nomex hankies

Another question. Now that I have done everything for dual deployment, just how many of those shear pins do I need for the lower and upper sections. I know that on four inch diameter rockets they use three pins, but I am wondering if I need that many for this little 1.6 inch diameter rocket.

Caley said:

Finally got most of the build done. I still have to decide on how to decorate it. Right now it is a few ounces under projected weight given by the instruction manual, but that will change when I install the two chutes and Nomex hankies

Another question. Now that I have done everything for dual deployment, just how many of those shear pins do I need for the lower and upper sections. I know that on four inch diameter rockets they use three pins, but I am wondering if I need that many for this little 1.6 inch diameter rocket.

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While you can do shear pins for cardboard rockets, the 38mm airframes really don't require them, and its kind of a pain to do them in cardboard as additional reinforcement is necessary around the holes they would fit in. However 1 shear pin is sufficient if you really want to do it, otherwise just make sure the everything is properly friction fitted (nose cone snug to prevent apogee deploy of main, and motor section snug to prevent drag seperation at motor shutdown). Friction fitting and masking tape are your friends for this size rocket.