Rocketarium KSR-420S - 3x18mm cluster

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Tyler P

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This is my first cluster rocket. Looks like a very simple build and I'm looking forward to digging into it!

I buy a lot of the Estes bulk packs with the variety of motors and always ending up having A8-3s left over (because they're not as fun, lol) so I thought it would be fun to use up the undesirables in a cluster rocket!

I've always thought this one looked cool and it's a cool sport-scale sounding rocket. Sounding rockets are my favorite, lol!

Enjoy the build!

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Tyler P

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Motor mount installed in the rocket.
 

Tyler P

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Fins rounded and sanded.
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I decided to try yet another method of sealing the fins. Two coats of Deluxe Materials EZE-Dope, sanded between coats. I'm still going to do another coat on them with the EZE-Kote before I prime the rocket. They were still a bit grainy but should be good after EZE-Kote and paint.
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High-heat drying rack.
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Before and after a 2nd coat and quick sand.
 

Tyler P

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Fins on!
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Baffle/coupler installed, shock cord in. It is ready for a coat of EZE-Kote, a quick sand with 400 grit, and then primer.
 

kuririn

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What is the motor retention method? Friction fit?
I don't see any engine hooks.
 

Tyler P

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I'm thinking just a wrap of tape for a snug fit like an Estes minimum diameter. The motor mounts weren't long enough to add any sort of retention like motor hooks. The stopping blocks are flush with the upper ends of the tubes.
 

Tyler P

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So, I found a length of what I think is 2-56 threaded rod that will thread nicely into the hole at the top of the motor mount. Unfortunately, I don't have any 2-56 nuts to check it. I'll pick up all the necessary bits at the shop tomorrow, when I go in.

A bit of epoxy piped in to the top of the mount, thread the rod in, let it set, and throw a washer and nut on the end and it'll be good.
 

Eric Nantel - DiaLFonZo

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I found that a 3/16 aluminum standoff is almost a perfect fit inside the 3 24mm body tubes.
Drawing (around a 18mm inside tube, i don't have your dimensions) it seems to be too tight for that standoff which mean you have almost no space.

You have access to a 3D printer i could draw an internal part that fit but your 2/56 threaded rod might be a better solution.
 

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Tyler P

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I decided to go with a 4-40 rod with a #8 washer and regular steel 4-40 nut. Seems like it should do the trick well enough. I didn't have access to a 4-40 thumb-screw or wing nut, which would be easier, but this will work. I always have a Gerber multi-tool on me when I go out to do this kind of stuff anyway.
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Tyler P

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Nice, be sure to post some launch pics!
I will certainly try to get some good ones. I have a couple photographer friends with some skills, and they want to come and shoot some pics one day!
 

Tyler P

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Filets are done. I didn't take pics of the process as I was doing 2 rockets with one batch of 30-minute epoxy mixed with SIG micro-balloons, so I didn't have time to stop and take pictures.

Mixed 30-minute epoxy and then added micro-balloons until it made a nice slurry/paste. Applied with a popsicle stick and smoothed with a finger dipped in rubbing alcohol.
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Eric Nantel - DiaLFonZo

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Very nice - Should hold up pretty well.
I would suggest a 3D printed attachment on the nut.. but it will get completely melted i guess ... lol
 

Tyler P

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Very nice - Should hold up pretty well.
I would suggest a 3D printed attachment on the nut.. but it will get completely melted i guess ... lol
Thanks! Yes, it probably wouldn't hold up to being directly in the blast zone.
 

Tyler P

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I decided to brush on two coats of EZE-Kote by hand this time, instead of using my airbrush. Too lazy to clean it out today, haha! It doesn't leave it quite as smooth as airbrushing it on, but it will look the same once I do a quick pass with 400 grit.
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Tyler P

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Got some work done tonight.
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mbeels

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Boy, when you build, you don't mess around, another quick one! Looks good, was that paint also done by airbrush?
 

Tyler P

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Boy, when you build, you don't mess around, another quick one! Looks good, was that paint also done by airbrush?
Thanks! Yeah, this was airbrushed. I had to touch up the nose cone by hand, as I had a bit of a masking issue.

Honestly, I could have just painted the red areas by hand but decided to put the effort in, lol.

I did learn that I need to pick up a touch-up gun to spray clear-coats. The airbrush, even setup with the bigger needle, doesn't spray heavily enough with clear to put down a proper wet coat. This one turned out well enough, though.
 

Tyler P

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This is the first time that I have come across Eze Dope. How did you like it for use on your balsa fins? Did it add some strength to the balsa? Did it fill the grain well? Was it easy to sand?

Thanks!
-Dave
It is easy to sand. It's not really intended to be used in this way, I just thought I'd try it. I think I like EZE-Kote a bit more. It seems to harden up a bit better, which is what it is made for, but they're both water-based, and easy to sand. There doesn't seem to be a any super easy solution for filling the grain that works super well, but I do find EZE-Kote gives nice results. You can do several coats fairly quickly because it dries fast, and then you can sand it down nice and easy. I definitely prefer it to the wood glue method.
 

kuririn

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Heh, cracks me up with the newer generations not knowing or hearing about dope.
What's old is new again.
Full circle.
So Tyler, I take it that you also do wood model airplanes, no?
Gonna have to look into the airbrush acrylics. I have a starter kit and a couple of books, but haven't allotted the time to learn the process yet.
Laters.
 

Tyler P

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Heh, cracks me up with the newer generations not knowing or hearing about dope.
What's old is new again.
Full circle.
So Tyler, I take it that you also do wood model airplanes, no?
Gonna have to look into the airbrush acrylics. I have a starter kit and a couple of books, but haven't allotted the time to learn the process yet.
Laters.
I picked up a little stick and tissue model a few years ago to do, mainly to try the waterbased dope. I have built a couple giant scale rc planes and fly high-performance aerobatic rc planes. I used to build the Guillows stuff as a kid, and I may try my hand at another one soon.
 

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