US Rockets Dual 18mm Rear Eject

[snrkl]

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

Obligatory kit spread:


Overall kit quality isn't great:


Nosecone arrived chipped (pic is post sanding)


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.


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:

 

[snrkl]

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:



Then gluing the BT and pods together



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:


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

 

[snrkl]

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



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

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




So that's all glued and filleted now.

 

[tHoagland]

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]

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]

BT fillets.

 

[snrkl]

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



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]

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]

Drilled the nosecone and removed the end.


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.



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


BT Fillets finished with CWF and sanded.



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]

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]

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]

Matt black complete.

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

 

[Lugnut56]

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.

View attachment 332064

 

[snrkl]

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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