Darkstar Series Build

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mtnmanak

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4" Dual Deploy Darkstar build begins here

Took a little break after the holidays due to some knee surgery a couple weeks ago, but back on track and building out Darkstars!

For this build, going to approach things a bit differently. One of the reasons there was a delay after finishing the 3" Brightstar was that I am planning to use a full Sticker Shock wrap for this build. I talked to Mark a couple times and he designed a really amazing wrap for this build and it took him a couple weeks to get it done. He highly recommended waiting to install the fins after installing the wrap, so I need to do things in a bit reverse order. Following Mark's guidance and the video he has on his site, I will basically get all the various holes and hardware in the booster, payload and switch band done before installing the wrap, then install the fins. I am also planning to put tracking in the nosecone, so will build out a sled for that. At the end of the day, not too different, but going to modify a the order I normally do things to accommodate the wrap process.

Started off as normal by dry fitting all parts and sanding down the ends to ensure a tight fit at all junctions. I then labeled all the ends so I can remember which parts had been fitted to other parts.

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I also marked out the lines on the couplers for later use:

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And marked down the fin lines and rail button lines all the way down the tubes. One note, normally I would not mark the outer surfaces with a Sharpie because the Sharpie lines have a tendency to bleed up through paint, but I am doing a wrap on this rocket, so it is not a problem.

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mtnmanak

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I am not going to inject the internal fillets for both the forward and rear fins this time. I am only injecting the front fins and then will do the rear internal fillets through the aft opening before I fix the rear CR in place. I usually forget to grind out the injection holes before putting in the MMT, so this time I made it a point to do it first on the checklist. I find it much easier to use a Dremel to grind the holes when there is no MMT blocking the bit.

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mtnmanak

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I taped the retainer onto the end of the MMT and taped the tailcone onto that so I could accurately measure out the various spacings on the MMT for the CRs and retainer. A reminder from the 3" build, if you are going to use one of the Aeropack tailcone retainers, the spacing is much different. Luckily, Wildman included a fairly long MMT with this kit, so there was more room to work with at the forward end of the fin slots (as compared to the 3" model). I didn't tack anything in place right now, just measured things out and marked the MMT.

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mtnmanak

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The MMT measurements allowed me to get an accurate length for the kevlar bridle. For this build, I am using a 1/2" tubular kevlar rated to 6000 pounds. Pretty straightforward here, measured the length so the bridle would just reach the edge of the booster when done. Cut the kevlar by saturating the cut point with thin CA then using a utility blade to cut it clean when dry. Nice clean cut.

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mtnmanak

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Next up, I measured the thickness of the kevlar to determine how deep the slots on the forward CR should be, measured and marked them on the CR, then ground out the slots with a permagrit file.

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mtnmanak

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I used the fin slots to mark out the fin lines on the MMT and masked them off with some tape. Also masked off the end of the upper fins slots where the middle CR will go to avoid getting any epoxy in that area. I fed the bridle ends through the slots and epoxied them down with some Aeropoxy 6029 and taped them in place. I epoxy them slightly angled away from the fin slot - I figure it adds a bit of security to have them angled away from the slot in the CR, but also helps ensure they don't inadvertently interfere with the fin installation later. Setting this aside to cure all day.

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mtnmanak

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While I am letting that cure, I want to get a jump on the fins. Normally, I would not finish the fins prior to installation, but since I am going to wrap the tubes, I want the fins to be painted before installation. So, I want to get the paint on today so they have a couple/few days to cure before I install them.

Before I epoxied the kevlar on the MMT, while I had the MMT in booster to mark the fins lines, I also inserted the fins and drew a baseline. Then I drew a line 2mm above that for a fillet. Mark says you can fillet right over the wrap, but I am not so sure I want to do that. Normally, I do a 5mm external fillet. I will meet half way here and later trim the wrap 2mm back and have fillet sit half on bare FG and half on the wrap. Should be nice and strong and, hopefully, provide a blend into the wrap.

With the lines on the fins drawn, I masked them off and formed a holder out of some packing foam. Next step is to hit them with some primer.

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mtnmanak

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Another small step today - drilled some holes in the rear CR and threaded some scrap kevlar thread in them to allow me to easily insert the CR and pull it back out, which needs to be done a number of times through the build. Credit to TVM for this method - first time I saw it was in the Zephyr build video they have. (probably a trick that has been around a while, just noting that the Zephyr video was the first place I saw it)

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3 coats of primer, wet sanded lightly with 400 grit after last coat. Moving on to the black paint. Using Duplicolor engine paint.

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4 total coats of Duplicolor Black Engine paint, 800 grit wet sand between the 3rd and 4th coats. Last step, need to start getting the clear coats on within an hour.

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mtnmanak

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Bridle epoxy is cured, coated everything with Proline 4500, including filleting the forward CR ring, top and bottom. Will let this cure overnight before conitnuing.

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mtnmanak

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This morning, I tacked on the rear CR with some mounting putty and the retainer with tape so I could epoxy in the MMT and the forward CR. I used Aeropoxy 6209 for this - mixed up a healthy batch and got a good layer in, just forward of the fin slots. Placed the MMT in the body tube to the right depth (checked by inserting the fins) and will put this aside to cure for the day.

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mtnmanak

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Working on the AV Bay while the epoxy is curing.

Fair warning for anyone else that gets this kit - I did get an extended coupler tube. The kit comes with an 8" coupler tube for the e-bay and I replaced it with a 10" coupler I got from Wildman. Mainly, this was becuase I wanted to use one of the printed Adeng sleds Wildman sells and the switch mounts are on one end of the sled. My experience in the past is that to get the switch ports away from the end of the tube, you need to push the sled to one side or the other and a longer tube helps keep the switch band fairly centered. In this case, my measurements indicated that a 10" tube would put the switch band almost center using the not-quite-5" long dual altimeter 98mm sled. So, if you use the same components and wonder why your switch band ends up considerable off-center, that is why.

The components for this build will be:
- Redundant MW RRC3 altimeters
- Dual Altimeter Adeng printed sled
- Shurter rotary switches
- Wildman aluminum bulkheads
- 1 foot long 1/4"-20 all thread

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mtnmanak

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Started off fitting the switches in place. As usual with these printed sleds, the terminals are quite close to the bed of the sled, so I like to solder the wires on at a 90 degree angle. Getting pretty used to doing these now and can knock it out in a very short time. Added the heat shrink tubing and installed the switches once everything cooled. One aspect I would note if you solder the wires on at an "extreme" angle is that it makes it more difficult to slip the locking nut back over the wires and onto the switch. You could solder the wires on while the switch is in place on the sled, but I am not good enough or dexterous enough with my soldering to make that work well, so I estimate how wide I can make the angle before I solder the wires by test fitting the nut over the wires. It isn't perfect, but I can usually carefully bend things around a bit to manipulate the nut on if I get too wide. Learned that lessen the first time I tried this method a while back and I ended up having to desolder and try again.

Oh, also, I cut away the two outer posts on the switch.

I used 22 AWG wire for this build with high temp silicon coating.

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mtnmanak

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The Adeng board comes with some small nylon standoffs - perfect size for keeping the RRC3 components off the deck. Lined them up and used the screws that came with the sled to anchor the two altimeters on. Trimmed the swith wires, got the battery terminals in place and installed ferrules on all wires. Screwed them into the altimeter and that portion is complete.

Note: I usually screw the battery covers on backwards when there is no battery in the compartment (staving off questions about why they are shown like that in the photo). Reason is twofold - I don't want to lose the covers or screws and it ensures I know I didn't inadvertently leave a battery in the compartment when storing/shipping the rocket.

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mtnmanak

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With the forward CR epoxied in place, this would normally be the point in the build where I epoxy in the forward fins, proceed with the next CRs, then rear fins, etc. But, since I am going to wrap it, I need to jump forward to a bunch of things I would normally do as finishing steps. Mark recommends drilling all holes prior to wrapping the tube and then going back later and cutting the holes out with a hobby knife. So, I needed to plan out and drill all the various vent holes, switch holes, shear pin holes and PEM nut fasteners prior to starting this wrap. Frankly, I should probably be more diligent about doing these steps earlier in the build anyway, so this is forcing my hand to do some better quality engineering up front.

I laid out the dry assembled tube with the retainer taped in place and all the seams/joints taped tightly:

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Measured and marked the vent holes in the booster, switch band and payload bay:

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Marked out the holes for the 1010 and 1515 rail buttons:

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Measured and marked for the PEM nuts:

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Measured and marked for the 2 switch holes:

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Also measured and marked for the PEM holes on the Nosecone and the shear pins:

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mtnmanak

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Then I drilled everything out and cleaned up the holes with a file. Holes drilled:

- 4 body tube vent holes - 5/32" each
- 2 Switch band vent holes - 5/32" each
- 1010 rail button holes - 3/16", cleaned up with file and test fitted with the weld nuts
- 1515 rail button holes - 1/4", cleaned up with file and test fitted with the weld nuts
- PEM nut holes in payload bay and Nosecone (using 4-40 PEMs) - 1/4" each
- 2 switch holes - 1/4" each

Once all holes were drilled and cleaned up, I installed the PEM nuts in the payload bay and nosecone:

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Then drilled and tapped the 2-56 shear pins:



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That should cover all the holes and hardware. Hope to take my first crack at wrapping the tubes later today!
 

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One more interim step, once the epoxy on the hardware cured, I assembled everything, put all the screws in and Dremeled witness marks at all appropriate junctions:

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g.pitts

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Really nice work, @mtnmanak. I believe I recall a PEM thread where you or someone mentioned that these inserts are not PEM, but another brand. Where did you find those? I really like the countersunk fitting for the outside of your body tube, but have never been able to find them.
 

mtnmanak

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Really nice work, @mtnmanak. I believe I recall a PEM thread where you or someone mentioned that these inserts are not PEM, but another brand. Where did you find those? I really like the countersunk fitting for the outside of your body tube, but have never been able to find them.
These are Lumadyne "tube fasteners" that I got from Apogee. I think they are the only retailer left that sells them. The claim to fame for these PEMs is that they are coated with a material that makes the metal adhere to epoxy better.


The big problem with those is that they are stupid expensive. You can marry up a standard PEM with a countersunk washer (like this: https://www.amazon.com/CRL-Flush-6-...coding=UTF8&psc=1&refRID=6GD139WC9EPDQENJN1PH) and get pretty close to the LumaDynes.
 
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g.pitts

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These are Lumadyne "tube fasteners" that I got from Apogee. I think they are the only retailer left that sells them. The claim to fame for these PEMs is that they are coated with a material that makes the metal adhere to epoxy better.
Thanks for the pointer! I'd completely lost track of these after researching Lumadyne having seen the thread I mentioned. The price... well, there's the cool factor! I have an L3 build in progress at this time, and I was planning to use plastic rivets, but the cool factor is calling... :cool: Apogee order underway.
 

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Thanks for the pointer! I'd completely lost track of these after researching Lumadyne having seen the thread I mentioned. The price... well, there's the cool factor! I have an L3 build in progress at this time, and I was planning to use plastic rivets, but the cool factor is calling... :cool: Apogee order underway.
I get you! I have two L3 projects under way (one official with my TAP and one that is a big ass rocket) and definitely planning on making copious use of the 6-32 size LumaDyne nuts.

The cost of them is crazy for a small, cheaper rocket, but after I crossed 4 figures in cost on L3 parts, I realized the LumaDyne cost was the least of my worries.
 

g.pitts

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I get you! I have two L3 projects under way (one official with my TAP and one that is a big ass rocket) and definitely planning on making copious use of the 6-32 size LumaDyne nuts.

The cost of them is crazy for a small, cheaper rocket, but after I crossed 4 figures in cost on L3 parts, I realized the LumaDyne cost was the least of my worries.
I'm with you, brother! L3 attempts can be spendy.
 

mtnmanak

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Got the ebay completely done:

Drilled all the holes in the aluminum bulkheads for the charge wells, terminal blocks and wiring.

I use Rocket Junkies 3g charge wells for this build. They require a 3/16" hole and a bit of epoxy.

Used simple 2 wire terminal blocks, used 4-40 screws with nylon nuts and bit of epoxy to secure them in place.

Ran the wiring (22 AWG silicone coated) through holes on the bulkheads and filled the holes with some FabriTac. Put ferrules on the both ends and installed into the appropriate ports on the altimeters. Used simple color codes: white wires for the nose/main parachute ports and yellow for the aft/drogue ports.

Installed the foreged eye-bolts.

All nuts got a drop of Loctite.

Finally, I installed a couple quick-connects to the wires leading to the aft bulkhead and then used heat shrink tubing to keep all the routing neat and tidy.

Did continuity testing on all electronics, will do a vacuum test when I do the ground testing.

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mtnmanak

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Okay, tackled the payload bay wrap this evening. This was my first full wrap from StickerShock, so headed in with a bit of trepidation. The wraps aren't cheap. They look amazing, though! And while Mark was designing this wrap for me, he told me that he can only print a piece up to 52" long and this is a 67" long total tube length that needs to be covered, so it was going to have to be done in a minimum of two sections. Booster and switch band was one section and the payload bay was in the second section, but the payload bay is less than half the 52" length, so Mark filled the extra space with a second payload bay wrap (no extra charge) which gives me a wrap to practice with. I am glad for this and glad I started with the smaller section first, I learned a few lessons.

Following the steps in Marks video tutorial, I lightly sanded the tube and thoroughly cleaned it with alcohol.

Then, using one of the lines I drew earlier down the whole length of the rocket, I lined up the wrap and put a tape "hinge" on one side:

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I wrapped it around to make sure it was square to the tube - first time "Go"!

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Peeled the backing off and began smoothing it out from the middle about an inch or two at the time. Mark says this stuff is easy to peel on and off and reposition - he is right, great stuff to work with and the wrapping turned out to be pretty easy.

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Got a couple small bubbles, but easy to press out with your hand, no problem:
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mtnmanak

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Once the wrap was on, I heated it up, as per Mark's instructions. It really shrinks onto the tube very well! definitely tightens up nicely around the ends and any holes/slots.

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And here is where I messed up. The PEM nuts left the wrap in a little tent around them:

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I heated it up, thinking the wrap would shrink around the nut. Instead, all that air had nowhere to go, so it completely bubbled up and deformed. I tried to "patch" it, but it is a bit of a mess.

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It doesn't look too bad, so I am going to leave it and save the extra payload wrap in case I ding this one up at a launch.

For the correct way to handle this situation, trim around the inner circle BEFORE you heat it up, the air can escape and the wrap shrinks nicely to the edge of the washer:

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Once it cooled, I trimmed the holes, checked to make sure the shear pins still fit, and trimmed the ends. Came out pretty darn good!

Going to tackle to long booster tomorrow - will need another pair of hands. No way I can do that on my own.

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