DX3 mini downscale

For some time now I really enjoyed the look of the MadCow DX3 and am considering to get a Super DX3 in the future to get into HP rockets. In the meantime I decided to downscale the DX3 to fly on D and E engines, calling it the "DX3 mini". I had the OpenRocket file done a while back, but never ordered the parts. OpenRocket predicts a max. altitude of about 1200ft on an E-engine.
Being on Vacation for a week I figured this would be a great time to start this project. I ordered all the parts from Semroc before heading to the North Carolina mountains. This will be my first attempt at a build blog. :eyepop:

Nice! I enjoy building with tubing around 2", its just a nice, manageable size. Not so big & heavy it needs an expensive motor, but still large enough to get my fat fingers around.
Enjoy the mountains, and enjoy the build!

T-Rex thank you,
Yes 2 inch is a great size to work with. The DX3 mini comes it at 1.8 inches. And in the simulator it flies up to an altitude that I think is just right for this type size of rocket.

And I am enjoying the mountains. If I'm not fishing for trout with my daughter, shooting the BB gun with my son, do family trips with the family, or build my rocket, this is what I'm doing: Just enjoy the view!

Semroc has some nice Ejection Baffles, that I really come to enjoy. I have currently 2 rockets flying with the baffle, and up to this point they have been working flawlessly. So I decided to install one in this rocket as well.

Assembly is straight forward and doesn't cause any issues. The baffle is made out of fiber so it's important not to forget is to cover the inside of the cone and back with one or two coats of glue to protect against the hot ejection gases.

While the baffle is drying I started on the motor mount. I could have ordered a complete engine mount kits, but I decided to just buy the individual parts and some extras, to be able to make multiple engine mounts to use in future builds. Ends up being a little cheaper too.


First I had to cut the tube. 4 inches long to be able to fit E and D engines.


The thrust ring was a little tight fit, and it was necessary to peal off the outer layer.


After cutting the slot for and positioning the engine hook, I secured it temporarily with a centering ring. Time to glue in the thrust ring.


I installed one extra centering ring at the very top of the engine mount. It's only function is to make it easier to get the ejection charge soot out of the body tube easily. Without the baffle I wouldn't worry about installing it.

crossbound said:

T-Rex thank you,
Yes 2 inch is a great size to work with. The DX3 mini comes it at 1.8 inches. And in the simulator it flies up to an altitude that I think is just right for this type size of rocket.

And I am enjoying the mountains. If I'm not fishing for trout with my daughter, shooting the BB gun with my son, do family trips with the family, or build my rocket, this is what I'm doing: Just enjoy the view!
View attachment 138806

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I told SWMBO that we should look into someplace similar as that when we left the Norfolk area of Virginia. No Mountains, Must have Beach! She has been to the beach twice in the 6 years we have been in SE Texas................

I have 2 that were scratch built using 1.9" AT tubes. A great size. They can be ball field flown, or let em rip.

Enough of my hijack, enjoy!!

crossbound said:

Semroc has some nice Ejection Baffles, that I really come to enjoy.

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Be warned that I had a 1.6" Nike-Smoke using a Semroc baffle where the baffle was blown completely out of the rocket by the ejection charge of an AT E20; it had previously done fine on Estes 24mm BP motors. Maybe I didn't glue it in well enough, but the AT motors tend to have more energetic ejection charges.

mikec said:

Be warned that I had a 1.6" Nike-Smoke using a Semroc baffle where the baffle was blown completely out of the rocket by the ejection charge of an AT E20; it had previously done fine on Estes 24mm BP motors. Maybe I didn't glue it in well enough, but the AT motors tend to have more energetic ejection charges.

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Thanks for the warning. I wasn't planning on flying it on anything bigger then an E-9, but good to know in case I come up with some silly idea to fly it faster and higher.

Engine mount built and ready to install. The body tubes are a little on the thinner side so I decided to reinforce the aft end of the rocket with a 1 inch tube coupler.
I had ordered 2 tube couplers, with the intention to cut one in half. Not one of my better cuts, but some sanding took care of the fuzzy edge.


The coupler is installed flush with the body tube, as well sitting flush with the lower centering ring.

After attaching about 12 feet of Kevlar shock chord to the baffle, the baffle was ready to go into the body tube. I installed it 6 inches from the upper end of the body tube. That will be plenty of room for shock chord, parachute, and shroud lines.

Now comes the boring part. Filling the spiral with wood filler and sanding. At the same time I "painted" the nose cone with food filler as well.


Of course we need launch lug. I decided on two 1 inch long 3/16 lugs. They were glued on with wood glue and added some thicker fillets with wood filler.


The fins were cut out of 1/8 inch balsa, the leading edge rounded for some "better" aerodynamics. And of course surfaces painted with wood filler and sanded after drying.


After gluing on the fins and launch lugs the rocket is finally taking shape! :w:

In OpenRocket I had to add about 0.5oz of weight to the nose cone to get the rocket stable at little over 1.1 caliber with an E9-6. With a D12-5 stability is around 1.8


I knew I would have a limited tool set with me I decided to drill a 1/2inch whole into the nose cone before going on vacation. I also cut a 1/2 inch dowel around 1 inch long to use as a plug once the weight is added.


Not being able to weigh out BB's, there was no way for me to know how much weight I actually added. I had brought a D12-5 engine with me, loaded it into the rocket, as well as adding the parachute. Now by trial and error I added BB's to the nose cone until the rocket was balanced hanging from a string right at 18.3 inches, as OpenRocket predicted.
Then I mixed some epoxy, added the BB's and poured them into the nose cone. Finally mixed some more epoxy to glue the plug into place.

Back from vacation and busy as can be, I only made slow progress on the DX3 mini.
This past week I was able to finish the nose cone with the eye bolt. After gluing in the wood dowel with epoxy, I sanded the epoxy flat, then added wood filler to fill in any gaps that were left behind and sanded flat again. I pre-drilled the hole for the eye bolt and putting some wood glue on the threads, screwed in the eye bolt.

Finally added a good blob of wood glue in the center of the eye bolt to finish it all up.

So the rocket was almost ready for finishing, but I wanted to add some nicer fillets to the fins. Many people on the forum were using Titebond No-Run No-Drip woodglue to make fillets on LPR rockets, so I journeyed out to buy some, which turned to be a little challenging... but that's for an other thread.
Eventually I was able to get the fillets done and it was time for priming. I started out with a gray primer, sanded a good bunch, more gray primer, and more sanding. Then I switched to a white primer, because eventually the rocket would be mostly white. After the white coat I found a lot more imperfections that I ended up filling in with bondo spot and galzeing putty. More sanding, and a final coat of white primer.
For the white base paint I used Dupli-Color Perfect Match Lacquer, and the metallic orange was done with Testors One Coat Lacquer. I love the orange color. I had hoped to get a smoother transition from the orange to white color, but the rattle can paint did just not get on nicely enough to make it look good. So the transition is rather abrupt.

Almost done! Decals and clear coat and we're ready to roll!
I decided to try out Testors Ink Jet water slide decal paper. I've never used it before but wanted to give it a shot. The design was done in Adobe illustrator using the PDF fin template exported from OpenRocket. I also searched the web to find the font that MadCow rocketry is using on the Super DX3 fiberglass.
The decals came out really good. The only complaint I have is that they were not sliding very much. I ended up with more of a peel and stick system, rather then sliding them the backing paper.
So what's left? Just the clear coat and maybe some polishing. I will let the decals set for at least 24 hours before spraying the clear coat.

Very nice! The DX3 is one of those 3fnc rockets that just look "right".

rocketgeek101 said:

Very nice! The DX3 is one of those 3fnc rockets that just look "right".

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It sure is. I figured since I'm not in the market for the real thing at this moment, I might as well enjoy a smaller version of it!

And so it comes to an end. I was able to put the clear coat on the rocket. It was a little tough to get a smooth coat, most likely because of the high temps and high humidity here in Florida. Initially I wanted to used a Duplicolor clear coat, but spraying it on a test piece of cardboard, I ended up with the milky haze. I switched to Valspar Lacquer clear coat and it turned out fine.

So hopefully next weekend I will be able to fly it at the Tripoli Tampa launch.

Nice and glossy! Remember to post launch pictures!

Clean work...came out super.

Thank you guys. And pictures will follow soon!