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Cosmic interceptor build

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kzimmerman

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First, a few disclaimers. I cannot build stock kits. Nope, it just won't happen. So, I've made some modifications to this kit to produce a more robust rocket. My plan here is to fly this on CTI reloads, in the 3 grain F size, and maybe the 6 grain G size (I'm eyeing up that green......). So, some things that came with the kit were not used, some things were just beefed up. Also, I'm in the middle of moving. If this thing runs past the 19th (I don't think it will) then the conclusion might be delayed. Theres also a very good chance I will wind up giving it to the Little Newton Burner, I mean, my son.

On to the show!

First on the instruction sheet was the MMT. This is an area that is most typically modified, and this build holds to this. First thing I did was to take the stock motor hook and cut off the forward tab. I then bent the tab up where it goes through the ring, giving me motor retention with no casing size limitations. Did the same on my black star. I then inserted the ring over the hook, gluing it down with titebond.

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I put one of the finlets on there for reference.

Next came all of those little finlets. They are all stock (gasp!) But the rest of the MMT.......

I disposed of those crappy cardstock centering rings and the tube coupler. I used .25" plywood instead. I cut a notch in the forward centering ring, ran some kevlar under it, and tied the kevlar off behind the CR. I then epoxied the CRs to the motor mount, and imbedded the kevlar into epoxy. No week little estes shock cord mount for me. I also glued that little ring tail on.
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Then, I glued up the main fins. No big mods (until later). I glued them up against a 2' level to make a nice straight edge for attachment purposes. The fit of these fins left a little to be desired, I had to spend some time jockying the bits to make it work.

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I built a jig to attach these fins, so after I marked the body tube, off we went.

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I modified the finlets on the tip of the fin to angle in 45 degrees. I don't have a picture of that, so I'm gonna stop here and get one or two!

Kurt
 

swatkat

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I LOVE this kit... so much so I now own two built ones and three backups. She'll fly great of F's. I have flown her twice on F44-8's which will fit in the stock mount. The wings are pretty robust both on launch and landing; my only issues have been that the wing area makes the rocket really susceptible to weather cock. But with that in mind you should be fine. I'll have to consider a 29mm mount in my next build. Would love to see this one go on a nice long G25, G40, etc.
 

Cabernut

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I recently sent mine up on an E30-4. Really whistles going up. I'd like to build another one with a 29mm mount as well then load it up with a G33 Mellow. Which reminds me, I wonder what speed the fins on these can withstand without reinforcement?
 

kzimmerman

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I don't know about top speed for stock fins, I was worried about the big fins and the small gluing area, so I glassed mine with .75 ounce cloth and polycrylic. I actually all ready did that, most of what you have seen so far was done before I started the build thread. I'm hoping to fly on 24 mm g's, specifically looking at the G-84 Green and the G-65 white longburn.

Anyway's, Pics of the fins. Sorry about the bad background, my dads shop is now my shop, and full of my stuff too until the 19th ish.

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The fiberglass cloth is actually laid at this point, last night I put another layer of polycrylic on it. A little more sanding where the air scoop goes, and the air scoop, the grill, and the last fin (?) will go on.
 

kzimmerman

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I've got some work to do on the fiber glass, gonna take a few day's to work on it, so this thread will be quiet for a few day's. Not to fear though, should be back by the end of the week posting up some stuff.
 

kzimmerman

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I built the grill, tacking the bits together with a tiny bit of CA, then when I had them all aligned, wicked some more CA into the joints. I cut out the air scoop, was a bit tricky. My first attempt at marking the tube and the centerline of the template slid away from the tube centerline. I rotated the tube, and used some ultra low tack masking tape to hold it in place. Went much better this time. I cut out the tube, smoothed the edges up with a bit of sandpaper, and trial fitted the pieces. Now I had a little problem.

Seems that the parts of the grill don't match up well with the template from the instructions. I have two of the "fins" that are about 3/32 to long, and the tube doesn't cover it. It's the two fins in between the outermost and the center fin. Well, I'll deal with that later when I put the grill in permanently. I put the grill in place, and glued up the tube to the rocket BT. I left the grill in while the glue is drying, but it isn't glued in yet. That will be one of the last things to be done on this build, after the painting is done. After the Titebond dries, I'm gonna run a later of glass over the intake and down onto the mings a bit. I'm kinda wishy washy about one or two actually...... thoughts? It's .75 ounce cloth, and I see this as having a tremendous drag force on it in flight.
 

kzimmerman

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so I'm gonna glass the scoop on, and I'm gonna replace the fin on top with a larger fin, and a bt-5 pod on top, the rounded nosecone on front and the tapered one on the back. My build is on hold for a bit, but not forgotten. I packed up everything, and then my house closing got delaed for 3 weeks. I've got 5 or 6 boxes of rocket stuff, might take me a bit to find what I'm after......
 

kzimmerman

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Status update. I made a new fin for the top of the rocket, with a BT-5 Body tube pod on top. All the glasswork is done, and I sprayed a coat of dark grey primer on it (looks black to me!). I then realized that I forgot the LL. Damn. I'm going with 1/4", and I have some, somewhere. Once settlement on the new house occurs, I'm sure I'll find them. Maybe. It's been a long messed up road on the house, we've been homeless since mid july. So it's slowed the build down some. Still no closing date, but should happen in the next few weeks. If your the prayin' type, now wouldn't hurt.
 

kzimmerman

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Further status update, Finally closed on the house, so I have my rocket bits to play with. Plus unpacking. Yay us, but it's good to have a roof over our heads that belongs to us. 3 months homeless......
So the rocket is essentially done except for decals. Once I get those on there, I'll snap a few picks and post em.
 
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