Mach 1, Karman Line - Space Force

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Eric

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I have just started on a new Mach 1 Rocketry kit. The "Karman Line - Space Force" looks like its going to be a fun and exciting one. It will be my first attempt at doing airstarts.

Mach 1 currently has a BT-55 size of this kit, but it does not use motors in the side pods. I am building a 2.6" with BT-60 side pods. With 54mm main and 29mm side motors.

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It will be 60" tall and weigh in close to 86oz. I laid out all of the parts and did a little dry fit. Just like previous Mach1 kits, the fit is amazing. The tubes and fins are great. No bubbles, delamination or other defects.

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I will take some initial weight and dimension measurements. Then wash all of the parts before assembly.

Initial plans are for dual deploy with electronics in a standard avbay. Planning on my new Eggtimer proton to handle airstarts and primary deployment. With a Quantum used for backup deployment. I will put an Eggfinder Mini in the nose. But I'm unsure if I will stick with the plastic LOC nosecone, or upgrade to fiberglass.

I don't plan on any high speed flights. But I can see getting some good altitude out of it. I have a pair of H97's for the pods, with maybe a J250FJ main motor.
 
My standard fiberglass assembly gets cleaned with acetone, scuffed with 80 grit, or gouged with a sharp razor, then cleaned again with acetone.

This build will be assembled with BSI 30 minute. I normally prefer a slower cure epoxy, but I'm trying to keep this going at a better pace. But I will be ordering a new set of rocketpoxy for the fillets. I just love how smooth it goes on.

So... I started with the motor mount tube. It went together like a normal MMT, but just required some good measurements to ensure the middle centering ring lined up with the fin tab slot.


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Most Mach 1 kits come with a flat kevlar to make a Y-harness. I opted to go with a single attatched kevlar, as I will also have two pairs of Airstart wires running down tthe tube. I used a really heavy weight 1/2" tubular kevlar. Sewed a loop on the end and installed a few layers of anti-chafing heat shrink. Then measured and installed the strap so the loop was just clear of the tube. I did debate if I wanted to sew a swivel into the kevlar loop, but opted not to.

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I did have to notch the middle CR to run the kevlar further down. The top ring was already notched.

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I set up a syringe on a stick so I could place the epoxy up in the tube where I needed it. Without messing with any of the fin slots. I set the aft centering ring so it was a little looser, and put some tape tabs on it. This allowed me to install it to ensure a straight motor tube, but removable to pour some internal epoxy later.

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Then the MMT was installed into body tube. The MMT was already measured to allow the Aeropack retainer to sit flush to the body when tightened. I needed the MMT to extend .15" past the body tube.

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Next up was installing the fins. I started with the main tube fins. Pretty straightforward on these fins. Just line it up very well and taped it into place.

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After an hour the epoxy was well set and I removed the tape to install the other side. A straight edge over the back ensures they are lined up nicely.
A couple tongue depressors fill the difference between the motor mount tube while it cured up right.

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Up next was the more involved task of modifying the other fin tabs. My plan is to use up to A 29/240 case in thr side pods. So I had to notch the fin tab to allow motor clearance.

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I took the things to the band saw and got to work. I cut inside the lines to leave as much material as possible. Assembled everything a few times making a few minor adjustments as needed.

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I ended up making a little adjustment so the motor tube would slide another 1/4" forward. There is 1/8" motor tube behind the pod tube.

Dry fit.
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Dry fit with motor hardware.
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For final prep of the fins I took them to the band saw and combed the root end. This will help with the mechanical bond, since the chemical bond is lacking from the fast cure times.

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After everything was cleaned, scuffed and cleaned again. I began piecing the pods together. It was like a puzzle. Fin in and epoxy. Fin out a little and epoxy. Fin back in. Apply forward internal epoxy. Forward centering ring slid in. Apply aft epoxy. Slide motor tube in. Apply motor tube aft epoxy. Slide aft centering ring in just the right amount. Then pull the motor tube back just a hair. To set the perfect distance for that motor case. Then wipe up all the extra epoxy that got outside the tube. They turned out very nice.

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Thank you Sir. I'm really enjoying this build.


The next item I'm going to tackle is setting up the air start wire conduit. My initial thinking was to run a small aluminum tube down the inside of the main body. Drill holes through the centering rings and have the wires exit out the back.

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There's plenty of room to fit the conduit between the motor mount and body tube. The problem that comes up is when using an Aeropack retainer. The conduit could be left a little short and just the wires could come by the retainer base. But I have measured my retainer so the cap tightens down almost perfectly flush against the body tube when tight on the motor.

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So my plan is to run the conduit externally past the motor mount tube. I will hide it in the fillet between the main body and side pods.

As shown here.
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I used a long drill bit so I could get a low-angle on the hole. I used to heavy gauge wire inside of the tubing. So I could hand bended without the tube collapsing. The conduit sits flat against the body tube.

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I plan to flatten down the conduit and smooth over the internal section with a little epoxy so no recovery gear tries to catch on it. I am planning on using two pairs of CAT5 Twisted wires to run the length of the conduit. They're easily replaceable, cheap and color coded.

I will go over more on its installation with the side pod that it'll be next to.
 
A channel big enough to pass two wires can be cut into the threads of an aeropac retainer. You also cut a small groove in the thrust shoulder and then your cap retains the wires positively positioned.

Although I like how your running the conduit externally. Just like real spacecraft
 
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Oh, this is awesome. Enjoying this thread and where it is going very much.
 
I'm flowing this thread. My daughter has the BT55 size, and we were considering turning it into a 24mm + 2x 18mm cluster.
 
Very nice!

Are you working towards building All ****** kits?
Lol... They do have a lot of great kits. But I would have to build a new kit every month for the next 5 years. And I still wouldn't have one of each kit. But my build pile is a mixture of manufacturers.
 
Lol... They do have a lot of great kits. But I would have to build a new kit every month for the next 5 years. And I still wouldn't have one of each kit. But my build pile is a mixture of manufacturers.

Umm this sounds like a goal... :)
 
Certainly not trying to tell you your business - the only experience I have with fiberglass rockets is buying my kits from Mach1 then opening the boxes, but real rockets have external wire conduits and tunnels - I think it would be an interesting detail to have working tunnels on a model rocket. So why hide it? Just a thought.

Definitely following this build even though I don’t have a KLT on the build pile...
 
Next I mounted the side pods to the Main body tube.

The fin tabs got a little epoxy on them from installing into the pods. So I lightly sanded them and did a good test fit. I had to slightly sand the aft end and slot of the tab so the side pod lined up with the bottom of the main tube.

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I used a block and sanded a flat spot onto both tubes. This gave me a great epoxy surface. I applied a thin coat of epoxy to each flat. Also put a generous amount into the fin slot.

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The fin tab lined the tubes up great. A few wraps of masking tape held it lined up and tight together. I pulled the tape firm to apply pressure.

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The second side pod went on the same way as the first.

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I'm really digging the front profile of this rocket. I really liked the fins coming out of the side boosters.
 
The first fin was just eyeball'ed on top of a printed template. I use a carpenter Square to set the second fin at 90 degrees. And use it straight edge for the other two. Also while verifying it against the printed fin template. But just by eyeball.
 
I mixed up a batch of JB weld and installed the Aeropack retainer. The 2.6" airframe is a perfect lineup with the Aeropack cap.

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I also drilled a couple pilot holes for the rail buttons. I will do there final drill size and tap after paint.

So when I installed the motor mount tube, I went a little heavy on the epoxy. Some ran forward and I ended up epoxying a few inches of shock cord to the body tube. But that looked like a great place to drill for a rail button. So the screw will have a little more to hold on to.

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And a little view all together, before fillets...

Front profile,
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Side profile,
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I received a new batch of Rocketpoxy the other day. So I started doing fillets.

So wrapped a piece of 80 grit around a bondo spreader, and that let me scuff up deep in between the two tubes.

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Cleaned the area real good, using an acid brush to get the acetone scrubbing deep in the crack. I did one final wipe with a lint-free towel and acetone. Then masked everything off nice and tight.

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I added one drop of dye to the epoxy just so it can have some visual contrast when smoothing them out. I poured the epoxy right after mixing. Then let it rest for 20 minutes before pulling the tape. Then smoothed with a gloved finger dipped in acetone.

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The airstart conduit was covered and you can't even tell it's under there. We'll get trimmed flush on the back end.

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This next image shows a good surface bonded area. There's 30 minute BSI in the middle.

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I will start with the fins tomorrow. It will take me a few days only doing two of the 12 fillets at a time.
 
The fin fillets went on nice. I really like Rocketpoxy.

I roughed up the joint with 80 grit, cleaned, then taped.

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I added one drop of the black dye to give the fillet a little color contrast for taking photos. I pour the epoxy right after mixing. After about 10 minutes I use a tongue depressor to remove most of the excess.

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After another 10-15 minutes, I pull the tape off.
Then use a gloved finger dipped in acetone to smooth them out more and remove the tape edges. And I often do more than one rocket at a time. Since you can only do one side at a time. That's why the mini frenzy got in the way of this picture.

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And 12 fillets later......

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These went on smooth enough that they will not get the normal treatment of spot filler putty. I will just go straight to a couple layers of primer and sanding.
 
I'm super impressed with how the conduit came out. Very nice work all around.
 
And after a few coats of primer and sanding it received its white base coat.

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After a few days in front of a heater, the body was masked and fins went to black.

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A couple days later decals were applied. Followed by a few more days in front of a heater before clear coat.

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I will get some flight photos this weekend.
 
The final build weight with all included parts came in at 64 oz. My parachute choices are not the lightest. So with full recovery, redundant altimeters and GPS my ready weight without motor is 90oz.
 
And after a few coats of primer and sanding it received its white base coat.

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After a few days in front of a heater, the body was masked and fins went to black.

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A couple days later decals were applied. Followed by a few more days in front of a heater before clear coat.

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I will get some flight photos this weekend.
Why is my plane in the background? Seriously! Shouldn't you be replacing all the speed tape you put on the left turbine? :)
 
BTW, I'm not flying back tomorrow commercially, so the plane better make it up and back to pick me up! :) And those homemade potato chips were amazing for the in flight snack. More of those, less of the ghost pepper dusted almonds.
 
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