US Rockets Dual 18mm Rear Eject

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snrkl

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So I decided a brain dead kit was best to keep me busy while I postulate other builds.

Obligatory kit spread:
ImageUploadedByRocketry Forum1505368247.329443.jpg

Overall kit quality isn't great:


Nosecone arrived chipped (pic is post sanding)
ImageUploadedByRocketry Forum1505368309.301290.jpg

24-18mm CRs were badly sized on both diameters and were already delaminating when I opened the kit - rather than struggle with them, I swapped them out for some Estes ones I have in the parts box. They fit perfectly.

Couplers are very sloppy fits - they will fall straight through the BT - gonna have to glue them well...

The bulkhead that is supposed to but against a coupler to make the rear eject plug is small enough to fall into the coupler - I'll probably end up making one out of 24mm BT of my own or at least maybe add a layer or three of paper to the inside first.
ImageUploadedByRocketry Forum1505368616.193902.jpg

I'm also a little worried about the thickness/ strength of the bulkhead - I'm convinced the bulkhead will snap when I screw in the eyelet for the shock cord: ImageUploadedByRocketry Forum1505368698.489534.jpg
 

snrkl

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But we press on regardless.

First step is cutting the ejection baffle holes: 2 in the main BT and one each for the motor pods:

ImageUploadedByRocketry Forum1505368813.374418.jpg

Then gluing the BT and pods together
ImageUploadedByRocketry Forum1505368833.041922.jpg
ImageUploadedByRocketry Forum1505368845.902473.jpg

I used the trick I learned on my Kraken clone - lines on the inside of the BTS mean you can align them from the top:
ImageUploadedByRocketry Forum1505368944.347398.jpg

Laid it all flat on both sides once glued to ensure the tubes are parallel - they were.. :)
 

snrkl

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Nose comes all wet sanded, motor mounts glued, filleted and drying.

ImageUploadedByRocketry Forum1505370502.451188.jpgImageUploadedByRocketry Forum1505370514.580604.jpg

I found a solution for the rear eject plug - it's obvious from the instructions the bulkhead used to be thicker: ImageUploadedByRocketry Forum1505370579.712357.jpg

I used one of the badly fitting CRs and braced the bulkhead against that.

ImageUploadedByRocketry Forum1505370616.773966.jpg
ImageUploadedByRocketry Forum1505370631.484330.jpg

So that's all glued and filleted now.
 

tHoagland

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My son built this kit last winter and found the same quality issues with the components. That said, once it was completed, it was fun to fly
 

snrkl

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My son built this kit last winter and found the same quality issues with the components. That said, once it was completed, it was fun to fly
Yeah - a scan of rocket reviews tells the same tale...
 

snrkl

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Pod nose cones, upper airframe and fins are on - motors mounted too.

ImageUploadedByRocketry Forum1505661497.303443.jpg

3 layers of BT fillets on and they're still bubbling - I've carefully been slicing out the offending air gaps and filling with less white glue from a much smaller nozzle - they're strong and much smaller, but just a bit ugly now. I figure I'll CWF them and sand before I paint.

I'll say one thing - these 1mm laser cut plywood fins are AWESOME...

I think I'll be looking into these more - I wonder if my local rocket supplier can do laser cut thin ply like this in the future.

Haven't decided on colour scheme yet, but I'm postulating on gloss white and some colour laser decals. Maybe an inverse SR71 paint scheme... who knows.
 

snrkl

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One small mod I'm considering is taking a few inches off the top and building a small payload holder below the NC for an altimeter. This rocket is very back heavy already - don't want to add any more weight at the back.
 

snrkl

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Drilled the nosecone and removed the end.
ImageUploadedByRocketry Forum1505874340.802931.jpg

Sandwiched the NC end between the coupler and a CR. Sealed the ebay with a bulkhead made from a laser cut CR Center. I knew I kept those for a reason.
ImageUploadedByRocketry Forum1505874368.605469.jpg
ImageUploadedByRocketry Forum1505874403.103633.jpg

Ebay fits my JLA3 perfectly. Drilled a small hole in the ebay to allow the barometer in the A3 to function.
ImageUploadedByRocketry Forum1505874767.672522.jpg

BT Fillets finished with CWF and sanded.

ImageUploadedByRocketry Forum1505874975.991090.jpg

Now it's primed and waiting for sanding and basecoat.

I'm thinking mostly white gloss with decals - I'll figure it out once the white is drying.
 

LithosphereRocketry

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I like your ebay! I've used Apogee plastic rivets to secure ebays but never thought of just pinning it in place... Very clever!

Sadly CTI doesn't make an 18mm line or I'd suggest bigger motors... And I wouldn't trust AT motors to ignite reliably enough.
 

snrkl

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I like your ebay! I've used Apogee plastic rivets to secure ebays but never thought of just pinning it in place... Very clever!

Sadly CTI doesn't make an 18mm line or I'd suggest bigger motors... And I wouldn't trust AT motors to ignite reliably enough.
LOL - my bad, I didn't explain: the chopstick pins are there to prevent paint getting in - apogee plastic push rivets are indeed how it will be secured.
 

snrkl

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Matt black complete.

I'm pondering some details in white paint pen, but I'll probably just stick to the stealth flat black option.

ImageUploadedByRocketry Forum1506209390.662599.jpg
 

Lugnut56

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Here's a couple pictures of my 18mm rear eject. I built it mostly stock, but added some additional stiffening where the engine pods and main body tube meet. I used sections of small bamboo skewers to fill the voids (you can get a bag of 100 12" skewers for a couple bucks at Wal-Mart). I also was concerned about the chute/wadding being pushed too far into the body tube, blocking the pass thru ports. I installed a centering ring with a short section of skewer glued onto the top of it to act as a barrier for the wadding, but will still allow the gas to escape through it. Before installing the centering just below the ports, I glued the Kevlar shock cord to the skewer and put a couple coats of glue on it to protect it from the hot gases. Have only flown it once on A8-3, but it wasn't impressive. Next flight will be on B6-4's. I like the black paint job on your rocket.

DSCF4577.jpgView attachment 332064
 

snrkl

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Yeah, I still haven’t flown mine.

I came close at the last launch but I didn’t have the energy to put the recovery hardware in.

I’ll get there one day... [emoji12]


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