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  #1  
Old 05-22-2018, 03:30 AM
DavidQ DavidQ is offline
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Default Continuing construction of classic K-kits with the Cobra K-10

I had gotten to the K-9 Spaceman a while back (in 2016) in the quest of my K-kit builds when I became distracted with making a special space for rocket building. As a result, some of my builds sat partially built for a long time.

I've returned to finishing them. So, the next project is the K-10 Cobra.

Since I did a scratch build meant to copy the appearance, and not necessarily the internals, I started by laser cutting parts, and casting a resin nose cone.

The Cobra originally calls for a balsa transition between the booster and the payload. I decided to use a paper transition, because I could draw it and cut it with the laser. I don't have a laser cutting lathe to laser cut transitions. But, it would be a cool tool to have.
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Old 05-22-2018, 03:35 AM
DavidQ DavidQ is offline
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The first step for my build was the payload section.

I made the payload tube extra long - as long as the payload section, and extending down into the paper transition. That gave me internal support for the transition. A slightly undersized centering ring was slid into the transition, to assure that it was forced to be round.

At the base of the transition I converted a BT-60 coupler, a plywood bulkhead, a centering ring, and some other scrap parts into the shoulder of the payload section. That was attached to the base of the BT50 payload section, and the transition was slid down onto it. After being glued, it was a really strong section.
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Last edited by DavidQ : 05-22-2018 at 12:01 PM.
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  #3  
Old 05-22-2018, 11:10 AM
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ghrocketman ghrocketman is offline
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Far more complicated than just using a TA5060 though, but it works.
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  #4  
Old 05-22-2018, 08:18 PM
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neil_w neil_w is online now
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I am very psyched to see this series of builds moving again. Normally I'd assume the builder would lose interest after a while, but after seeing what you did with the Shrox builds I will be watching to see how far you go with this (I expect pretty darned far.)

Or perhaps just biding time until I get to see you you do a scratch build of K-45.
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Old 05-22-2018, 11:23 PM
DavidQ DavidQ is offline
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K-45? I'm still on the stuff from 1964. That'll be quite a bit of time being bidden.

Meanwhile, back at the ranch.

With the payload section under control, the next section was the fins. To be honest, I've never found the Cobra to be attractive. It's got those giant fins that look like someone standing with the feet wider than their shoulders. And, it's got those giant fins that look like they'll take the better part of a shelf.

I had also investigated other historic variants of the Cobra. As we can see, there was a version of the Cobra published in Model Rocket News, V3N4, circa 1963. That's before the K-10 kit of the Cobra. It's my plan to build the historic versions as well. But, gees, the MRN version of the Cobra is almost identical to the K-10 version. The only real difference is a slightly different shape in the fins. That wasn't enough of a difference to dedicate that much shelf space to, so I didn't build the MRN version. (Edit - I just noticed that the Design of the Month 17 page for the MRN Cobra even mentions the Estes kit. So, I have no idea which came first.)

Or, maybe I didn't build the K-10 version. How will we ever know? OK, I built the K-10 version.

At the same time, I installed the motor mount, to our friends at Quest. Or, an engine mount to our friends at Estes. It takes three engines, and glued tissue was to be packed around the tubes. I have a laser cutter. So I laser cut some special centering rings.
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Last edited by DavidQ : 05-23-2018 at 12:17 AM.
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  #6  
Old 05-22-2018, 11:28 PM
DavidQ DavidQ is offline
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Then, I let the rocket sit on my shelf for a long, long time.

Finally, in the recent time, I decided to finish it. Imagine me spraying gray primer filler. And more gray primer filler. And sanding. And spraying more gray primer filler. And sanding. And taping off the fins and transition and nose cone. And spraying the body white. And letting it dry. And removing the tape from the fins. And taping off the body. And painting the fins and transition and nose cone blue. And drawing decals. And printing decals. And applying the water slide decals.

And then, showing the finished rocket. A copy of the Cobra from 1964.
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  #7  
Old 05-23-2018, 04:58 AM
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Wow, that sure is pretty! Nice work!
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  #8  
Old 05-23-2018, 09:23 AM
stefanj stefanj is offline
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I love the fin streamlining.

This turned out great. I take it you color printed the decals on decal paper?
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  #9  
Old 05-23-2018, 11:45 AM
DavidQ DavidQ is offline
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I drew the decals with Inkscape, and color laser printed them on clear waterslide decal film from Papillio.


I usually don't pay that much attention to the fin edges - round the leading edge, and square the other edges. But, trying to keep in the mood of the classic kit, I did spend time to streamline the fins on the Cobra. Thanks for noticing.
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