LOC Big Nuke 3e Cluster/Airstart Project

DMehalko

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Next up on the build table is a LOC Big Nuke 3e, after about a year into this high power stuff I'm finding I’m loving it more and more!

After getting my L1 and L2 done last year, and finally flying dual deploy vehicles, my next rocket goal is to fly some air starts and clusters which this project will be aimed at!

I ordered a modified kit, and went with a 54 center and 2 outboard 29mm mounts. In retrospect I should have done 2 38mm outboards or 3 29’s, but I’ll still have fun with this and fly it on big K’s and baby L’s, with some I’s in the outboard pipes

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DMehalko

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I’m also treating this as a ‘sorta practice L3 build’ so will doing some beefing up and making this thing a tank, I’d prefer it to last and not sweat at all when pumping some L motors through it.

So first thing first was to ditch the glass line and get glassing. Using the awesome soller products and standard weight 6” fiberglass sleeves, which is close to 6oz cloth. For resin, using west 105/206. Son wanted to hang out and build a simple Estes kit while this took place
 

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DMehalko

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For those interested in glassing, I highly recommend these sleeves over wrapping. You don’t get any seams, easy to get it how you want before wetting out the cloth, and with their heat shrink it pulls everything so nice and tight 👌.

I made a quick video on the process on my amateur hour new YouTube channel, 10/10 recommend;

 

Tim51

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In retrospect I should have done 2 38mm outboards

2 x 38s and a 54 would be wider than the 5.5" airframe. I did a build thread on a scratchbuilt 2x38 + 1x54 airstart project a few years back using Loc 5.54 parts, with the 38s bulging out the side:
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I seem to be having problems pasting a link but if you're interested search 'Build thread: 1 x 54mm + 2 x 38mm in a 5.54" airframe'

Good luck with your project - airstarts are great fun to fly, and really satisfying when they work.
 

DMehalko

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2 x 38s and a 54 would be wider than the 5.5" airframe. I did a build thread on a scratchbuilt 2x38 + 1x54 airstart project a few years back using Loc 5.54 parts, with the 38s bulging out the side:

I seem to be having problems pasting a link but if you're interested search 'Build thread: 1 x 54mm + 2 x 38mm in a 5.54" airframe'

Good luck with your project - airstarts are great fun to fly, and really satisfying when they work.

That looks like a sweet build! Ya you used retainers and all, ya that definitely wouldn't fit haha. For the first attempt im thinking a pair of G25w's at central burn out could be fun with a 5sec burn for affect, probably would decelerating during the burn but might look neat haha.
 

DMehalko

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Next up was to get the motor mount and fins lined up and tacked together, followed by some slow cure fillets, and finally some 6oz cloth across the motor tube 👍
 

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Tim51

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That looks like a sweet build! Ya you used retainers and all, ya that definitely wouldn't fit haha. For the first attempt im thinking a pair of G25w's at central burn out could be fun with a 5sec burn for affect, probably would decelerating during the burn but might look neat haha.
Yes the received wisdom for outboards seems either gentle longer burns or short fast ones, either way ensuring your timing avoids creating a powered arc, (ie where the outboards kick in when the rocket is already curving away from vertical). Some outboards do effectively delay deceleration, showing as a 'step' in the graph, some give a little burst on the pedal that shows as a secondary peak. When doing your sims remember that the outboards will take a second or two to come up to pressure, so avoid a long gap after MECO. I spend time studying the full sim spreadsheet to think through what's likely to happen. YMMV - As you know, we build these things then learn how to fly 'em... I'm not an expert, and very much still learning too. Enjoy. 😊
 

thzero

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For those interested in glassing, I highly recommend these sleeves over wrapping. You don’t get any seams, easy to get it how you want before wetting out the cloth, and with their heat shrink it pulls everything so nice and tight 👌.

I made a quick video on the process on my amateur hour new YouTube channel, 10/10 recommend;



Nice video... I don't remember it being that easy when I did my 3" LOC tubes :) Pretty much did this exact same method. Definitely make sure to get off as much excess epoxy, otherwise it'll make it much harder when trying to put the heat shrink. Larger heat shrink is much easier - nice trick with the second set of creases. And heat gun, do go slow, but don't pause to long on any area otherwise you could melt holes in the heat shrink.
 

DMehalko

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Thanks all!

Next on the build I needed to plan out my electronics bay in the booster section. And a sacrificial ezi65 fin became perfect for that 🤣.

I then cut a hole in the booster airframe to access the airstart electronics. I really like the perfect flight stuff, but no safety mechanisms built in. The egg timer proton looks great, but has tons of features and I only want to use one of them. So that left me with the apogee unit. A simple timer with an accelerometer in it for arming and gyro tilt safety built in so the outboards won’t light if it’s not going up 👍

I also wanted quick access to the electronics and switch, so trying something different here and building a hinged hatch. Still in progress!
 

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DMehalko

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Updates! Spent some time finalizing the fin can air start bay, making it removable to easily maintain the bits, and to be able to hide the wiring behind the sled for clean wire management.

The bay will hold a new gen4 apogee timer, 2s lipo, and a missileworks switch going to a eggtimer wifi switch for safety
 

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DMehalko

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Moving right along into the paint and graphics, on my carbon EZI, i spent forever getting a glass finish, but for some reason on this one i liked the textured glass look coming off the sleeve wrap. Being named a big nuke i thought id try a different look. I still cant decide if i hate it or love it :)

Using a mask from sticker shock, i painted on the lettering, thanks Mark for the custom work!
 

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DMehalko

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Finishing up the booster paint and clear, wonder how much altitude I’ll loose as a result of the ‘texture’ but feels neat on the hands after clear coat :D
 

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Tim51

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Thanks! Just need to pick a new central motor, have 2xI205's ill light at meco :)
Two suggestions based on my experience so far:
1) For a first flight, set your outboard ignition for a little before actual meco - the outboards will take a miment or two to come up to pressure, so you'll still get a nice pause, but without waiting so long that you risk a powered arc. Eg, For core burns of 2.5s - 3.7s, I've set the aux ignition for 2.2s, and still had a clear gap on these combinations: K630/2×I55, K445/2×H225, K445/2×I236, K740/2×I470
2) Cesaroni motors have the BP pellet which ensures good ignition for airstarts.

YMMV etc.
 

DMehalko

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Two suggestions based on my experience so far:
1) For a first flight, set your outboard ignition for a little before actual meco - the outboards will take a miment or two to come up to pressure, so you'll still get a nice pause, but without waiting so long that you risk a powered arc. Eg, For core burns of 2.5s - 3.7s, I've set the aux ignition for 2.2s, and still had a clear gap on these combinations: K630/2×I55, K445/2×H225, K445/2×I236, K740/2×I470
2) Cesaroni motors have the BP pellet which ensures good ignition for airstarts.

YMMV etc.


Good advice! Ill set the trigger to be sooner, ill hopefully get a flight video soon, November 6th is our next club launch
 

DMehalko

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So made a major bonehead move, but i didnt know any better at the time :D. I used regular aerotech ignitors instead of low current ematches for the outboards. I waited in anticipation only to have nothing light (obviously). Mind you im an 'aerotech' guy, so there is that lol.

Either way had a great flight on a K659, still reached 4,064ft despite carrying extra weight in the tail of unburnt motors and extra nose weight to compensate lol.

Round 2 soon and flight number 3 on this bird soon! Thinking a K1103x for the next central

Short boost video, i do like the K695 :)

 

StreuB1

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Beautiful flight and beautiful rocket!! Get you a bag of CCP e-matches from Ebay or Amazon and give it another go! Shes gonna rip on those 3 motors!!!
 
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