Mad Cow 38mm - 2.6" Arcas

I've been looking at this rocket for a long time and ran some Open Rocket sims on it. This thing should scream. It can hold some of the largest 38mm casings out there and being all G10, it should be able to handle any motor it can take. Sims for a CTI J530 suggest 10,000+ feet and a speed in excess of Mach 1.4.

I'm looking forward to this.

EeebeeE said:

Sims for a CTI J530 suggest 10,000+ feet and a speed in excess of Mach 1.4.

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I like the way you think, my friend. :grin:

I'm looking forward to this.

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Likewize. Subscribed.

Alex

I shall enjoy this thread.

Got a notification from Mad Cow that it shipped today. It is difficult to get the specs for all the parts because this is an upgrade of their original FG design. It originally came with a 29mm motor tube and a single body tube, but I think, after looking at their components specs that I the layout below is pretty close to the parts. I believe the aft tube is 28" long and the forward tube is 16". The nose cone is 8.25" and is a secant ogive form. I had an Aerotech Arcas the same size that I lawndarted on New Years 2012, but the fin can survived so I took the fin specs from it.

For the most part, I am going to build this close to factory design, but I will make it DD and use an Adept 22 as the DD electronics. I am making a universal tracking transmitter assembly for both my DD and single deploy rockets that will have a Perfect Flite P-Nut altimeter attached as well (the Adept 22 sled will be universal too, and will fit into a couple different rockets). I will rely on the P-Nut for better telemetry data on this.

One minor change is that I will deploy the payload bay with the nose cone, and put a bulkhead in the payload bay so I can...well...carry a payload. It will have a camera facing the horizon and another facing aft.

Here is my initial layout in Open Rocket...and just for giggles, The configuration includes a Loki J1000. Note the altitude and speed in the lower left. Who knows, on a hot and humid day maybe the aft camera will pick up the sound cone.

Friday after a long week at work, it is great to have present waiting at your front door.

The Arcas came today, and what a great little kit! I am completely impressed. A 10.75" Secant Ogive nose cone (4:1) that fits like a glove into the upper tube. The fin slots are precision cut and the fins fit like a glove into them. The obligatory kit shot shows everything that comes with it. The only exceptions are the two bulkheads, the retainer, and the shock cord set to the right of the nose cone.



I weighed all the parts and remeasured everything. This is the revised layout, including my Av Bay which I have been working on over the past couple days.



This will be a relatively quick, but fun build.

Sanded the fins today, but in the process I killed my vibrating sander. Had to hand-sand the last fin and a half.

Had to dry-fit the thing to see how it went together. The centering rings are a little loose, which means that I may have issues with my av-bay. other than that it goes together pretty well.

Since I am using this thing a my first real mach-buster I am going to go a different route than what is prescribed for the fins. Instead of installing the motor tube then gluing the fins in, I chose to install the forward centering ring then install the fins. I slid the motor tube and the bottom centering ring as a guide to make sure everything lined up, then took out the motor tube and aft centering ring. That way I have more room inside to better put in internal fillets.

My handy-dandy Estes Fin-alignment guide does the trick again and the rubber band ensures that there is a tight fit. As you can see, without the motor tube in place there's a lot more room available to do the internal fillets.

Continuing the build thread

The open fin can gave me a lot of room for a small airframe to reinforce the fin roots. I ended up taking small strips of 6 ox. fibrerglass and epoxying them in as fillets to the inside of the airframe. These fins aren't going anywhere, especially after I do external fillets. After the fins were done, I applied generous amounts of epoxy to the fin roots and the forward centering ring, then slid the motor tube in. Before I installed the aft centering ring I added another amount of epoxy to the fin root where they attached to the motor tube.

I have to say, even though there hasn't been much feedback thus far on this build, that this is a fun project. everything is going together well, and when I am done, I am going to have a real high performing rocket that is relatively inexpensive to fly.

these are great tips. keep going, looks great. Are you building the AV from scratch, if so can you give pictures.

I am building the AV bay sort of from scratch. I have an Adept 22 Altimeter already on a sled and I am going to build the bay so that sled will fit. Then I can have a sled that is interchangeable between this and another rocket.

take pictures of the AV when doing please. i want to make mine modular also.

It has been a while since I posted on this thread, but I wanted to show off my nose cone electronics. This is a universal component that I will take off and use for several different rockets.The base is made from 3 sheets of 6 oz. fiberglass, compressed under about 40 pounds of steel. On one side is a BRB transmitter and on the other is a PerfectFlite P-Nut Altimeter. My thought was to have another altimeter located away from the E-bay so that it is not impacted by ejection gasses. I should get a little more accurate reading.

The assembly will fit into a 38mm tube and it only weighs 1.4 ounces. This will go into the nose cone of my Arcas, my Cosmic Cucumber, and my 3x upscale of an Estes Der V-3, my L3 build. It attaches into the nose cone bulkhead using 2 #6 sheetmetal screws through the two holes on the ends of the base plate. The other two holes are vents for the altimeter.

I'm almost done with my Madcow Arcas.
I bought it because my Aerotech was my favorite rocket for years,
till I totaled it in February.
I'm thinking exactly as you are.
Since i started with high power, theres no going back.

Different construction materials and technique's

Your forcing me to take some pics.

I like the things you've done so far, you'd like mine.

Teddy

I just read some more,
No altimeter or speaker of any kind should be exposed to the
e charge in any way, for any length of time.

Just for grins I designed and simmed a second stage. The second stage can take up to a 54mm L.

I have to say, even though there hasn't been much feedback thus far on this build, that this is a fun project. everything is going together well, and when I am done, I am going to have a real high performing rocket that is relatively inexpensive to fly.

Evan,
I couldn't agree more......
I'm making a piston out of 3" of a coupler and bulkheads.
More efficient and positive deploy.
My maiden flight should be 5/11 with the
Radical Rocketeers in New Jersey.
I'm psyched.
Did you maiden yet???????????
Teddy

Not yet. I have 2 other projects ahead of this one for our upcoming launch at Geneseo. Plus a wild thought just hit me on this one and I think I have the Kahunas to actually do it. The Aft centering ring is 3/4" forward of the bottom of the airframe. I think I can make this a 2-stage monster with a 54mm booster stage.

I would use a timer mounted in an e-bay in the booster to ignite the main stage motor. URRG has a launch late in June and they have a high-altitude waiver (22,500' I think). I would need every bit of that waiver.

The stages would be held together with a coupler tube and shear pins. The second stage would fire at a 5-10 second delay after the first stage burned out. This would cause it to go in and out of Mach, but would make it go higher. The other option is to hold the delay down to 2-3 seconds. If I do that it will go well past Mach 2, but about 5,000' shorter.

The configuration below is with an L950 in the booster stage and a J530 in the upper. Most likely, the maiden would be with a K740 in the booster. I could lengthen the delay and still go over 20,000' with that configuration because the booster would not get up to Mach 1.

Submitted for your approval: The 2-stage Arcas. Should I do it?

I'm goin to URRF
DOOOOOOOO ITTTTTTTTTTTTTT

Teddy

Hey Evan,,,,,,,,,
Ya wanna see something nice I'm building,,,,,,,,,,,,,

My 3" X 8 1/2 ft Wildman Intimidator is going up on a J800 T tomorrow 5/12 with the Radical Rocketeers in Great Meadows N.J.........
Your comin right????????

My Madcow Arcas will maiden at the next launch,,,, either 5/18 or 3 weeks later I guess,,,,,, theres been rain dates involved.......

I'm definitely flyin those two at URRF........
But I should have one more too maiden at URRF..........
My very first scratch build on Rocksim.................

And A drum roll please....................

View attachment 128998

Teddy

The forum says the attachment is invalid.

View attachment Altitude Seeker.rkt

hows dat........

I don't have RockSim. do a screengrab from the image, paste it into Windows Paint, and save it as a jpeg file.

Open Rocket will open rkt files.

Maiden Voyage today. A near cloudless day in Western NY, a CTI J394, and an hour and a half search later, and I got this great video.

[YOUTUBE]NGm8yza18g4&feature[/YOUTUBE]

Can't resist...When I install an MD-80 digital camera inside the rocket, I have to start recording immediately. There are still a couple things left to do in my checklist, so the camera picks up bits and pieces of what is going on. So I edited together some of what the rocket sees as it is being prepped and ready for take off. To the tune of the Blues Brothers, "Sweet Home Chicago" (which happened to be the right length and fits the tone of the video) here is the Arcas flight from the rocket's point of view.

[YOUTUBE]MiCFEvo0VN0[/YOUTUBE]

Getting it ready for URRF this weekend.

When I built my Aerotech Arcas, the paint scheme was based on a cross between the operational model which was black and silver and the color alignment of the presentation model which was the traditional red and white with the red markings down the side. I added some red pinstriping (barely visible in the photo). It was my first midpower rocket, and it flew great. Unfortunately on New Years Day 2012, the G138 motor failed to deploy and it came in ballistic. The video of the flight is also below.

[YOUTUBE]2CevR_ltMJo[/YOUTUBE]

This time I am going with the presentation markings with a red nose cone and fin, but with a chrome instead of white. As a memorial to my Aerotech, there will be black pinstriping. Should look cool. I am using Dupli Color automotive spray which goes on well, dries fast, and is easy to wet sand. Not that much in the can, though. Since I am using chrome, I sprayed the red first, and that coat went on tonight. Tomorrow I will sand the red, tape it up, then spray on the chrome. I am also going to spray something else chrome to make sure I can clear coat it. Thursday I hope to pinstripe add the decal, and clear coat if possible. Saturday, it flies hopefully to 9,500' and hits 1,000 MPH.

Chrome paint applied. It came out very good. I'm going to let it set for a while then apply the ARCAS decal and some black pinstripe. Should be a real cool mach buster. Does anyone know if you can clear coat over chrome paint?

I know interest in this is low, but I am proud of how it finally turned out. She flies tomorrow at URRF. Hopefully with a CTI J530. Prettiest Mach buster out there.

Very nice! Remember to post pics of the flight.

Nice rocket, questionable beer choice...


Good luck with the flight!

patelldp said:

Nice rocket, questionable beer choice...


Good luck with the flight!

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Bud Light Platinum. Great beer. But to each his own, I guess.