L1 1.6" Madcow DX3 Build-Just Launched

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DeltaFuturistics

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Hey guys. This will essentially be my first post on the forums and just want to say hi and thanks for having me. I've been flying RC for about 7 years of life but sadly haven't been able to because of school and hockey. I've gotten into model rocketry at the beginning of last year and have been making engines at my high school since then with our measly club of another person and teacher. Finally decided to step away from the failures and successes of that and work on a couple kits over the summer to get certified. I've been reading through the forum for about a month and half learning techniques and other stuff. Enough about me, on to the kit from Madcow.

This is in no way a super big rocket. I wanted a small platform so I could learn techniques first before moving on to bigger kits. First impressions were all good. I ordered the kit with the Kevlar shock cord, chutes with flameproof cloth, and FW nose cone. I went a head and used some foam board and cut out some fin guides. I also bought an aeropack 29 mm retainer. I will be flying the kit on an aerotech 29/240 casing, but I'm not sure which load I'm going to use with it.

I plan on using an Easytimer from altus metrum for DD. Apogee messed up my order for it, they sent me a tiny perfect flight firefly altimeter for small models using ejection charges in the engines instead even after manually highlighting the invoice that the put the correct one in the box...made me laugh a bit. I called them and got it fixed. They should have sent one but nothing has come in yet...

Here is the kit out, and then a dry fit after some sanding to the fin slots and a wash. Epoxy of choice on the build will be JB weld and Rocketpoxy.

FullSizeRender (2).jpgDX3 dry fit.jpg
I have no idea why they came out sideways on the forum. They are perfectly fine viewing them on the pc, but I will soon figure out how to rotate them.:confused2:

Before starting this thread I decided to work on it by gluing on the centering rings and retainer with JB weld.
FullSizeRender (4).jpgFullSizeRender (5).jpg

I have a couple questions right out of the gate.
1. The shock cords came with swivels on them. How am supposed to attach the swivel to the eyebolt?
2. How long does it take for rocketpoxy to set up?

Won't be launching this till around September because I also want to build most of a level 2 kit (2.6 tomach or frenzy most likely) later and possibly get both certs in one launch day.

Will glue shock cord to this assembly today with rocketpoxy.
 

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welcome! Glad you posting - I love the DX3.
1. You will need quick links to attaché the swivel to the eyelet - small one is fine
ImageUploadedByRocketry Forum1464894164.912858.jpg

2. Not sure exact specs - but I mix up and let sit for 10-15 min (air bubbles will dissipate, then administer. Then to hold something in place - it seams to take 30 min to an hour, but will still be soft to touch - so solid takes overnight. John from Rocketpoxy or others might answer some specifics on that. Just used it the other night. If your using for fillets it tends to move up to an hour for me so I let sit for 20 minutes prior to using for fillet, just my 2 cents

Will be watching the build!
 
The dry time should be stated on the instruction sheet that came with the Rocketpoxy. I've found it to be about 3-4 hours until firm enough to handle and full cure is at least overnight. I've done fillets at 4 hour intervals with no problem. (One around 5:30 when I arrive home from work, another at 9:30 or 10.

As recommended by Nick, giving some time for it to dissipate gas bubbles is a good idea. Some people recommend spreading it out thinly and then scraping it back up with an old credit card or similar. I also let it sit for about 20 min after mixing when using for fillets. Otherwise it self-levels a bit too well.

I too will be watching this build. I'm currently building the same kit in the 2.6" size myself.
 
Thank you both for the good tips. Will be going over to home depot soon for those clips.

I have seen that advice about laying the rocketpoxy to get bubbles out for fillets, will definitely do that when I do mine. I plan on using half inch CPVC for the fillets, is that a good size?

I went ahead and glued the shock cord tether on to the motor tube with it. I put a drop of CA in the CR cavity and then inserted the shock cord and made sure it was flush. I let it sit for about 10-15 minutes for it to firm up before I worked with it. I also added the black dye to seem how it works, couple drops and boom, done. I mixed wayyyyyyyy too much (two full spoon fulls of too much) but it was nice to understand how it feels and what its like to work with. Looks pretty good, had to be careful with clearance because of the short centering rings. With the extra epoxy I also did the switch band on the coupler.

I have to rotate any pictures in Gimp for them to be proper here.

Peanut Butter and Cool Whip hah
Rocketpoxy PB.jpg

And the motor mount and switchband
SC mount.jpg

I left my masking take in my car for some reason, and mom's subie blew a tire so she had to take mine, could have made it look better but it should do fine.
 
The dry time should be stated on the instruction sheet that came with the Rocketpoxy. I've found it to be about 3-4 hours until firm enough to handle and full cure is at least overnight. I've done fillets at 4 hour intervals with no problem. (One around 5:30 when I arrive home from work, another at 9:30 or 10.

As recommended by Nick, giving some time for it to dissipate gas bubbles is a good idea. Some people recommend spreading it out thinly and then scraping it back up with an old credit card or similar. I also let it sit for about 20 min after mixing when using for fillets. Otherwise it self-levels a bit too well.

I too will be watching this build. I'm currently building the same kit in the 2.6" size myself.

Are you building with the 38mm or 54mm motor mount? I plan on getting a 54mm and using the aeropack adapter to go 38.
 
So I continued on with the build today and glued in the motor tube assembly into the booster. I plan on also gluing fins in today and possibly fillets tomorrow. My strategy to get the retainer lined up perfectly with the booster tube will be explained with the pictures.

Before starting to mix everything I first sanded the CRs on the motor tube and also the inside of the rocket with a wood dowel and super glued sand paper to it to reach down and sand the inside as well. I then cleaned all of it over with alcohol on a cotton ball and once again used a dowel to reach down it to the tube. I then took a paper towel to dry everything and then shoved it through the booster tube and out. Finally I bundled and shoved the shock cord into the motor tube.

I made sure I did not mix to much rocketpoxy this time and let it sit inside the cup for about 10-15 minutes before applying it to the rocket so air bubbles can come out(as advised). Taping some Popsicle sticks together with some tape worked perfect to reach down and get the epoxy into the right place.
IMG_1634.jpg
After applying epoxy to the inside I slid in the motor tube with the rear CR still exposed and applied some epoxy on the forward edge and first half of CR and slid and twisted in so that the CR was just barely out. Epoxy of course started to spew out of the top a little and taking a paper towel and vary carefully removed the excess to make sure the retainer cap won't get glued on. The only issue with letting the rocketpoxy sit for a bit is that it thickens quite a bit so this took some time.
IMG_1635 v2.jpg
I then pushed and twisted a little more making sure that the shock cord mount was not in the way of the fin slots and guesstimated the length of the retainer needed to be left out. After this I held the rocket with motor tube up and inserted the 29/240 casing with closures. This ejected the shock cord down the tub and I was able to screw on the rest of the retainer and secure the motor.
IMG_1636.jpg
Finally I slid in the assembly in completely and gave a little twisty twists back and forth and made sure the retainer cap was flush with the body tube. I then just unscrewed the cap and slide out the motor casing to let it all set up.
IMG_1637.jpg
Boom done, now onto the fins.
 
Another work day on the rocket and throughout the day I have thought of several questions that will be asked at the end of this post. Today i was able to glue the fins on with JB Weld and tomorrow will work on my fillets. I was also able to work on the e-bay and assemble it mostly but have yet to thread lock any of it because of my questions.

So here we go with the fins, did the regular rough sanding to add some bite and then cleaned with alcohol. After mixing up some JB Weld I went ahead and coated the bottom of a fin to start off.
IMG_1638.jpg
I then inserted the fin front first and set it in and let the JB weld set in for about 30 seconds. I then pulled the fin out and repeated with applying some more JB Weld. I heard around on the forum that the nick-name for this technique is called the "Double Butter".
IMG_1640.jpg
I made sure I had my fin guide in the rear to lift the rocket up enough and to align fins once they were in place. When I moved to the next fin I then pulled it back and then set it back on.
IMG_1641.jpg
Here it is set up to dry after wiping all the excess Weld off the fin's. (Don't worry I straightened the alignments after the pic.)
IMG_1642.jpg
Moving on to the e-bay was simple. Not much to say as I just followed instructions from Mad-cow's site...I also drilled the plastic rivet holes to hold on the payload bay.
IMG_1643.jpgIMG_1644.jpg

Here are questions as of now for the build.
1. What form of ejection method should I use? I'm pretty sure a 1/2 inch CPVC end cap will fit on with the eyebolt so I can't really use that method. I also am aware of using the centrifuge tubes. I can get these easily from my Mom's lab but I'm weary of just letting it hang in the rocket because I have read them blowing chunks out BT's before. I also heard that it is recommended to glue some thin pipe to the e-bay and just have it sit in there. I also plan on buying E-matches from Jim for ejection. Thoughts?

Link to the E-match thread: https://www.rocketryforum.com/showt...deploy-ya-need-these&highlight=CJ's+Wacky+Wed...

2.Vent hole size... I plan on using three and I have read Vernk's page on it and read his chart but it doesn't really help me as the smallest length for 1.6" e-bay on the graph is like 15"... mine is 6". I haven't found anything on the instructions from Mad-cow but maybe I'm just blind. Any help on size?
3. Last question for now...I will probably use some bass wood to create the sled for the rocket it self but how have you attached the actual sled to the threaded rods from each bulkhead on the bay? I was thinking using just some bolts and Jb welding them to the sled and threading them on?

Thank you all
 
Looking good so far. I strongly suggest an H250G :) much fun.

It may be a 'small' rocket, but this is a ballsy L1 cert. I like it.

I've used tubes for charges... in something this size, it's that, glove fingertips, or having something turned up on a lathe if you have a buddy with a metal shop.
 
Thanks for the reply. I'm pretty sure the best to use to test for now is the glove fingers. Any advice on vent holes and sled mounting?
 
Today I did my first set of fillets ever. I went ahead and rough sanded all surface areas and then cleaned them up. I did the trick with a sharpie and your choice of fillet puller and wrote a bunch on the tip of the pipe and ran it down to get lines. I decided to use 1/2 CPVC. Next I masked off everything. Mixed up some rocketpoxy added some dye and was ready to go. I let it sit for 15 minutes for bubbles to come up and they sure did.
IMG_1645.jpg
I was ready to apply the epoxy and took a Popsicle stick and applied the epoxy evenly and spread it out generously. I let them sit again but for 10 minutes I think.
IMG_1646.jpg
First pull turned out well. Dipped the pipe in the alcohol and slid it down from top to bottom.
IMG_1647.jpg
Here they are after multiple pulls on each side.
IMG_1648.jpg
Here it is with the mask just pulled and then finally cured.
IMG_1649.jpgIMG_1650.jpg
Overall with my first time I am very pleased. No bubbles or anything bad on them. Sanding will of course be needed but especially the front and rear tips of the fin will need it. Couldn't have asked for a better result. Will do the other 2 sets within the next few days.
 
Got another set of fillets done today. Called apogee once again as well about the altimeter well.......They've shipped it alright and the people at the front desk seem to have misplaced it this whole time...:facepalm::eyeroll: I will rummage through the mail room on Friday for a desperate search.

I also think I have been able to answer my own questions so far and will be using 3/32 holes as vents. I think I will be gluing a form of tube to the sled and the using bolts to keep it on. I can't work with the sled till I get the altimeter.

New question, do you recommend a screw switch for the altimeter or should I just turn it on and then place it on the pad?
 
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New question, do you recommend a screw switch for the altimeter or should I just turn it on and then place it on the pad?

For safety, you need to be able to turn it on after it's on the pad. You also need to be able to turn it off before removing it from the pad if you decide to cancel the flight. You can twist and tape (but not tuck) or you can use a switch. I've done both. I prefer a designed in switch, but twist and tape is very easy.


[emoji1010] Steve Shannon [emoji1010]
 
1. What form of ejection method should I use? I'm pretty sure a 1/2 inch CPVC end cap will fit on with the eyebolt so I can't really use that method. I also am aware of using the centrifuge tubes. I can get these easily from my Mom's lab but I'm weary of just letting it hang in the rocket because I have read them blowing chunks out BT's before. I also heard that it is recommended to glue some thin pipe to the e-bay and just have it sit in there. I also plan on buying E-matches from Jim for ejection. Thoughts?

2.Vent hole size... I plan on using three and I have read Vernk's page on it and read his chart but it doesn't really help me as the smallest length for 1.6" e-bay on the graph is like 15"... mine is 6". I haven't found anything on the instructions from Mad-cow but maybe I'm just blind. Any help on size?

3. Last question for now...I will probably use some bass wood to create the sled for the rocket it self but how have you attached the actual sled to the threaded rods from each bulkhead on the bay? I was thinking using just some bolts and Jb welding them to the sled and threading them on?

Thank you all

I've recently finished up a Madcow Frenzy DD 1.6", which is just about the same build as this one.

1 - I am using the latex glove fingertips for charges
2 - I have two holes, each 1/8". I am using a SAS5 snap switch with a pull before flight rod as the on/off switch for my quark and needed a hole that big for the pull rod. (See perfectflite website for details). It's worked fine for me on 4 flights so far.
3 - I used 1/8 ply for the sled, and a launch lug epoxied on each side of the sled to secure it to the threaded rod. I made the sled the exact length of the tube, so it doesn't shift around in flight. I also used some hot glue to secure it to the aft bulkhead, makes it easier to get it together.

I don't have any photos of my ebay with me now, but I can post some later tonight if you'd like to see what I did.

Also, if you are planning on putting an H into this thing, I'd highly suggest a tracker. I squeezed an eggfinder into the nose and needed it on both flights that I put over 3k. On an I205 it was completely gone, on an H114DM I lost it after separation. Only on a G64 was I able to keep it in sight, on that flight it was around 1500 feet.

cheers - mark
 
For safety, you need to be able to turn it on after it's on the pad. You also need to be able to turn it off before removing it from the pad if you decide to cancel the flight. You can twist and tape (but not tuck) or you can use a switch. I've done both. I prefer a designed in switch, but twist and tape is very easy.


[emoji1010] Steve Shannon [emoji1010]

Thank you Steve, will definitely use a switch now that you have told me that.

I've recently finished up a Madcow Frenzy DD 1.6", which is just about the same build as this one.

1 - I am using the latex glove fingertips for charges
2 - I have two holes, each 1/8". I am using a SAS5 snap switch with a pull before flight rod as the on/off switch for my quark and needed a hole that big for the pull rod. (See perfectflite website for details). It's worked fine for me on 4 flights so far.
3 - I used 1/8 ply for the sled, and a launch lug epoxied on each side of the sled to secure it to the threaded rod. I made the sled the exact length of the tube, so it doesn't shift around in flight. I also used some hot glue to secure it to the aft bulkhead, makes it easier to get it together.

I don't have any photos of my ebay with me now, but I can post some later tonight if you'd like to see what I did.

Also, if you are planning on putting an H into this thing, I'd highly suggest a tracker. I squeezed an eggfinder into the nose and needed it on both flights that I put over 3k. On an I205 it was completely gone, on an H114DM I lost it after separation. Only on a G64 was I able to keep it in sight, on that flight it was around 1500 feet.

cheers - mark
Thank you Mark. Will look into that snap switch but might go to screw due to simplicity( Pull before flight tags do look awesome on a rocket though). Judging by your experience I guess I will need a tracker in the rocket. Why did you put the eggfinder in the cone instead of ebay? Space? Eggtimer is a very viable option due to price. However I think my soldering skills are not good enough to build one. Is it possible that someone on the forums does this with a price?

Another option is going with the telemetrum v2 and putting it in the ebay if space is a problem with the eggfinder, but 300 bucks is a lot for an altimeter.

It would be great if you sent a picture of that nose cone setup.
 
Thank you Mark. Will look into that snap switch but might go to screw due to simplicity( Pull before flight tags do look awesome on a rocket though). Judging by your experience I guess I will need a tracker in the rocket. Why did you put the eggfinder in the cone instead of ebay? Space? Eggtimer is a very viable option due to price. However I think my soldering skills are not good enough to build one. Is it possible that someone on the forums does this with a price?

Another option is going with the telemetrum v2 and putting it in the ebay if space is a problem with the eggfinder, but 300 bucks is a lot for an altimeter.

It would be great if you sent a picture of that nose cone setup.[/QUOTE]

I don't think an eggfinder and quark would both fit in the ebay, though it might be possible with an external antenna. It would be a super tight fit though. The nose cone is pretty tight as well, I would have been better off using an external antenna for there as well. I built the quark as my first soldering project with the help of a electronics guy, he showed me what to do and had all the right tools. After that it was easy to put together my 2nd quark, and the eggfinder/rx. There is someone on the forum who puts them together though, I'm sure a search will turn up that info.

Here are pics of my ebay and nosecone. I had a friend in a machine shop make up a metal 'ring' with a hole tapped in it to secure the nosecone bulkhead in place. I had originally epoxied a couple of nuts to the shoulder of the nosecone but one of the nuts popped off during testing so I swapped the nuts out for the ring instead.

One side :

Fo3ahjA.jpg


Other side :

aNsLKoA.jpg


Inside of nose cone (and messy workbench) :

wgUgA5t.jpg


cheers - mark
 
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I don't think an eggfinder and quark would both fit in the ebay, though it might be possible with an external antenna. It would be a super tight fit though. The nose cone is pretty tight as well, I would have been better off using an external antenna for there as well. I built the quark as my first soldering project with the help of a electronics guy, he showed me what to do and had all the right tools. After that it was easy to put together my 2nd quark, and the eggfinder/rx. There is someone on the forum who puts them together though, I'm sure a search will turn up that info.

Here are pics of my ebay and nosecone. I had a friend in a machine shop make up a metal 'ring' with a hole tapped in it to secure the nosecone bulkhead in place. I had originally epoxied a couple of nuts to the shoulder of the nosecone but one of the nuts popped off during testing so I swapped the nuts out for the ring instead.

One side :

Fo3ahjA.jpg


Other side :

aNsLKoA.jpg


Inside of nose cone (and messy workbench) :

wgUgA5t.jpg


cheers - mark[/QUOTE]

I appreciate the pictures make a lot of sense. Too bad I don't have any ways to machine anything at the current time. The easy mini seems to be almost half of the size of quark. I fit that on one side with the lipo there as well I could run the egg finder on the other and make an external antenna. If I did this and covered it with a small shock cord nomes sleeves to protect against ejection blast would it effect that range and performance of the egg finder? Also does the egg finder require a ground antenna like the Yagis I've seen on here or is that for frequency strength tracking( don't know what its real name). Is the receiver that comes with the kit all you need to plug into the computer?

Thanks,Frank
 
I was able to finish all fillets on Thursday and also drilled in vent holes as advised by mark. All I have to do is glue in the bulkhead to the shoulder and sand fillets. Then it will be time to paint. I will avoid gluing in the bulkhead until I get an egg finder and decide how to fit in. I think it will work in the e-bay, but tight fit.

My skills at soldering are quite low. I have soldered plenty of batteries, motors, and escs leads from RC but never have worked with a PCB. I plan on buying a quark and giving a go at that but will most likely ship out an Eggfinder LCD to Connor. In the future I hope to be able to solder one.

Has anyone stuck an antenna out of the e-bay bulkhead? If so how did you protect it?
 
Just remember that GPS modules have issues when put in AV Bays with steel allthread running through them. Nose cone bays are recommended.

If you run the antenna out of the av bay, it's best to use one of the rubber duckies on a bulkhead connector, and cover it in several layers of kevlar and shrink wrap. Some folks use masking tape rather successfully.
 
I have two of this style rocket, the mini DX3 and the mini Tembo. They both use a screw switch, and a single vent/port. The glove tip method for the ejection charge works very well.
I have had the mini Tembo go to 5,800 feet and above mach, and it lost gps lock. Luckily another club member found it and returned it. THANK YOU.

Here is the DX3 on a pro29 H255 to 3,300
hard video to watch wicked spin
[youtube]uTBBPf668To[/youtube]
 
Just remember that GPS modules have issues when put in AV Bays with steel allthread running through them. Nose cone bays are recommended.

If you run the antenna out of the av bay, it's best to use one of the rubber duckies on a bulkhead connector, and cover it in several layers of kevlar and shrink wrap. Some folks use masking tape rather successfully.

I was thinking that the steel would be a problem. Forgive me, but I'm not very familiar with the lingo but by rubber duckies do you mean like a rubber protected antenna? If the antenna was completely out of the e-bay would it effect the GPS still? If going with a nose cone bay, I couldn't really catch how mark mounted the sled to the eye bolt on the NC bulkhead. He also used a custom machined ring to screw on the bulkhead while I think I will go through the shoulder. Guess I have to do a lot of research.
 
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I have two of this style rocket, the mini DX3 and the mini Tembo. They both use a screw switch, and a single vent/port. The glove tip method for the ejection charge works very well.
I have had the mini Tembo go to 5,800 feet and above mach, and it lost gps lock. Luckily another club member found it and returned it. THANK YOU.

Here is the DX3 on a pro29 H255 to 3,300
hard video to watch wicked spin
[youtube]uTBBPf668To[/youtube]

Very cool and glad someone got your rocket back. I was wondering on where and how you opted to mount your GPS on the tembo and DX3?
 
On the dx3 it is in the nose-cone

The tembo was one of the first and not made for dual deploy. So first I put an altimeter in the nose and flew it with a cable cutter then I added a small section of body tube below that for the GPS and ran very small gauge speaker wire for the ejection and cable cutter charge.
 
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Yes, like from a counter-sink drill bit

Careful though, when trying to mill out just a little, the drill bit wanted to catch and really cut into that poly stuff the NC is made out of. Maybe grind out the indentation
 
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Yes, like from a counter-sink drill bit

Careful though, when trying to mill out just a little, the drill bit wanted to catch and really cut into that poly stuff the NC is made out of. Maybe grind out the indentation

I'll have to pick up a bit from Home Depot, is there a specific size that you used? According to the picture you go through the shoulder of the NC or did you do something else, I ask because you said "poly stuff" is this the fiberglass shoulder or the filliment wound NC.
 
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Be sure to get a good countersink bit, not just a larger drill bit. A good countersink bit doesn't try to pull itself into the work and is angled correctly to match the underside of the screw head. A large drill bit will grab at your material and try to feed itself which will cause frustration.


[emoji1010] Steve Shannon [emoji1010]
 
Yes, like from a counter-sink drill bit

Careful though, when trying to mill out just a little, the drill bit wanted to catch and really cut into that poly stuff the NC is made out of. Maybe grind out the indentation

Got it, how did you opt to turn on the Altimeter in the NC, did you drill a hole in the shoulder of the NC and use a pull switch or screw switch?

Be sure to get a good countersink bit, not just a larger drill bit. A good countersink bit doesn't try to pull itself into the work and is angled correctly to match the underside of the screw head. A large drill bit will grab at your material and try to feed itself which will cause frustration.


[emoji1010] Steve Shannon [emoji1010]

I'll be sure to, my new parts list for this rocket is building up fast hah
 
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