Gemini lab thing...

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Mugs914

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I worked up something like this in OR a little while ago. Got the build bug this past weekend so I actually started work on it, along with a couple of others.

This idea was inspired by several things, one being the Gemini MOL project from the sixties. Another inspiration was the old Estes plan called the "Orbital Transport Laboratory", or something like that. It was a DOM plan, I think.

Anyway, I had a Semroc Gemini capsule nose cone and a bunch of tube laying around looking for a job, so off we go!

First, here are a couple of shots from OR that show more or less what it shoud look like"
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So far pretty straight forward stuff; Semroc Gemini nosecone Estes BT-55 tube, typical motor mount (18mm) with several feet of Kevlar shock cord looped around the motor tube...
20210215_105713.jpg

20210215_105727.jpg


The ring is made from a piece of 4" LOC tubing approx. .65" long. It was supposed to be the switch band on a 4" av bay, but I didn't need it for the rocket the av bay went in to. I propped it up on a couple of batteries to get some idea of where it would go and what it was going to look like.
20210215_105926.jpg


I wanted to add some dimension to the ring though I'm not sure what form it will take. It may be just smooth or it may end up being segmented around the periphery. Either way it started with a strip of 1/8"balsa that I formed around a 4" tube for another project.
20210215_144456.jpg


The ring was slipped over a piece of 4"coupler tube so t would stay round during the process. Then the strip was clamped to the ring and tacked with CA.
20210215_150750.jpg


Once everything was tacked and the ends trimmed everything was glued securely and the inside soaked with thin CA. This produced the typical noxious fumes, but when the smoke cleared the whole thing was rather bullet proof. Unfortunately, the inside was also rough as a cob. There will be much sanding...
20210215_150811.jpg


Looks pretty good so far...
20210215_151018.jpg


More to follow...

Thanks for looking!

Mike
 
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Mugs914

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Been thinking about how I wanted to go about mounting the ring fin on this thing. With all deference to my mate @Cape Byron, it didn't look like the anti-gravity coupler was going to work long term, so I had to come up with another idea. 😜

I have various sizes and shapes of carbon rods in the stash, so I got to thinking about a 'spoked wheel' kind of thing. Maybe four main struts from the front side of the ring and eight smaller stabilizing struts in an A-frame arrangement from the rear side of the ring. Maybe A-frames front and rear...

I'm thinking the center of the ring assembly will be a sleeve that slips over the BT-20 engine tube. That way the whole ring fin assembly with the struts and central mount could be built on a jig and glued to to model in one piece.

Regardless of how it ends up, I'm going to build it on some kind of jig, so I got started on that. A four inch bulkhead forms the basis of the jig and a short section of BT-20 will be the center. Should have some time to work on it all tomorrow...
 

Cape Byron

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I'm thinking the center of the ring assembly will be a sleeve that slips over the BT-20 engine tube. That way the whole ring fin assembly with the struts and central mount could be built on a jig and glued to to model in one piece.
Sounds like a plan. Building on a jig helps a lot with ring fin things.

I still like the anti-gravity coupler idea though... 😁
 

les

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Very Interesting. Looking forward to this.
 

Mugs914

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Got the ring fin all done. It took a couple of days to get through the process, but it came out pretty good, I think. Here are the pics...

First off, the ring had to be filled and sanded since there wouldn't be access after it was all glued up. (Never filled an inner spiral before.)
20210220_222220.jpg


Jig made from 4" bulkhead and a dead motor....
20210220_222031.jpg

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For the inner strut attach points I wanted something that would slide over a BT-20 motor tube, but with a snug fit. I didn't have anything like that, but I found these little rings. I think they are designed to hold metal engine hooks, so the fit is fairly loose. A strip of cardstock and a little sanding made for a good fit over the motor tube.
20210221_181954.jpg


To get the proper placement for the struts I printed a guide from Payloadbay.com. Spacer blocks were glued in place to support the struts while the glue dried. The mounting ring was placed on the jig and the struts themselves were cut from rectangular carbon rod.
20210221_211909.jpg


Sanding the struts to fit was a bit fiddly, but didn't take too long. They were then glued in place with medium CA and left to dry.
20210221_214532.jpg


The rear ring was then slipped on the jig and the rear struts made from smaller carbon rod. They were glued in an A-frame type arrangement.
20210221_223335.jpg


Once everything dried it was (carefully) pulled off of the jig. In spite of looking a bit spindly, it's actually pretty darn strong! I'll probably do some fiddly details to make it look like the thing folded for launch or something.
20210221_223516.jpg

20210221_223506.jpg


This was definitely the biggest hurdle on this build. It should be pretty conventional from here on!

As always, thanks for looking!

Mike
 

Mugs914

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Here's what it looks like on the model.

It probably won't be glued until after paint, I want some kind of detail/texture on the inside of the ring and that will be easier to make and paint with the ring off the rocket.

I'm also not sure about the motor retainer. It's just a place holder for the pics. The original idea was for an engine nozzle-looking cone and that's probably what I'll end up doing, but the retainer has an interesting look too.
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Cape Byron

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Looking really good. Dr Zooch made an excellent nozzle arrangement for his Mk II kit.


I've thought of doing something similar to this a number of times since I built a Mk II.
 

BABAR

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Looking really good. Dr Zooch made an excellent nozzle arrangement for his Mk II kit.
I am with @Cape Byron on this, I think a flared nozzle (bell or otherwise) would accent the retro design more than the retainer. Not sure if you have room for both. Would a Wendy’s ketchup container fit?
 

BABAR

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Probably won’t be an issue, but if you go with the nozzle outside diameter should be less than largest body tube diameter or you may have launch lug issues.
 
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