# Gemini-Titan Scratch?

### Help Support The Rocketry Forum:

#### JStarStar

##### Well-Known Member
Has anybody scratch-built a GT anytime recently?

I skimmed over the plans for the old Estes kit on the JimZ site, I'm thinking about trying to do one later this winter...

I guess the old Estes kit used a BT-60 Gemini nose cone, and a BT-70 main Titan body. BMC lists a BT-60 Gemini cone, so that would probably be a good place to start.

On the original Estes model, the fins were cutout clear plastic joined together with dope and plastic cement, I've never seen that come out looking good.

I think my own inclination would be to build a "Christmas tree stand" engine/fin unit, painted white or primer gray or something, which would insert into the model for flight, and be replaced by a scale engine nozzle unit for static display.

What's the consensus on add-on "neutral color" fin units as opposed to clear plastic fins?? I've never thought the clear plastic fins look realistic anyway - the rocket doesn't really look like that, so is it really that good of a solution??

#### powderburner

##### Well-Known Member
if I am not mistaken, I just saw some Gemini and Mercury-style NCs on ebay
I think those auctions were going to end soon so you may want to check 'em out (don't know if they are a "good" deal or not)

#### sandman

##### Well-Known Member
joe,

I've made some Gemini titan nose cones to fit a BT-60 but I believe they are for a BT-60 main body.

I'll bring them with me tonight.

#### dtomko

##### Well-Known Member
I have all the parts ready for a clone of the old Estes GT and it will probably be my next project. Yes, BMS has the cone and the BT-70 is readily available. After reading several build reports from years ago, there are a few ways to improve the original. You can simplify the internal stuffer tube system. You can probably lose the whole BT-20 part and use a longer BT-60; there's enough pop from the two engines to fill the tube for ejection of the chute. The fin system is a pain and the original (I had one) was ugly, didn't stay on all that well, and tended to scrape the paint off the bottom part of the BT. I saw a while back that someone had cut slits in the BT-70 on the black roll pattern and used clear fins with tabs that slid in for flight. You couldn't really see the slits on the black. To do this you would need to make sure the stuffer tube ran all the way to the engines. Not impossible, but I haven't measured to make sure a BT-60 will go over the ends of the two motor tubes at the front of the engine mount. If you are going for a static vs. flight system you have a lot of flexibility. The Neubauer GT does this with a single engine. Personally, I think the 2 engine cluster looks great and I also think clear fins do look better from a distance.
Drew Tomko

#### JStarStar

##### Well-Known Member
Hmm. Don't see anything like that listed now, unless the item description is so far off that the words "Mercury" and "Gemini' don't register a hit...

Actually, the cones won't be a huge problem... as I mentioned, Balsa Machining Service lists a BT-60 Gemini cone on its stock list, and the price is not horrible, I think about $6.00. As far as Mercury is concerned, I am all set... besides my Mercury-Redstone I can look out the window into the park and see hanging in the G-D #(%*@$*&*&!! tree... ...

I have another copy of the Mercury-Redstone kit down in my workshop waiting to be built, and earlier this week I travelled to one of our local Rocket Meccas and got my hands on an Estes Mercury-Atlas kit - something I've lusted after for quite a while. So I have both Mercury vehicles accounted for. The Redstone and Atlas should make a nice flight combination - as I understand it, they are built on the same scale, from the same molded plastic Mercury capsule.

Apollo, of course, I'm gonna have Saturn Vs coming out of my ears... I have the Sandman Saturn 1B already built, along with an Estes 1B in the box, which I think I may try to clone to build a "flyer" version... so actually I have a pretty complete lineup of the U.S. manned space fleet... a Gemini-Titan and a Shuttle are pretty much the only missing links. But I've gotta have something to keep on the lookout for, eh??

Although that does bring me up to what I see as my late-winter PMC project... I got ahold of a couple copies of the AMT "Man In Space" 1/200 model collection... and also a 1/200 Hasegawa Shuttle kit .... I could probably convert them to fly as follows:

Mercury-Redstone ... MMX motors
Mercury-Atlas ... 13mm Mini-motors
Gemini-Titan ... 13mm Minis (or maybe 18mm)
Apollo-Saturn 1B ... standard 18mm A-C
Apollo-Saturn V... 24MM D/E
Shuttle - 24MM D/E

Ahh, well, plenty to keep busy....

#### dtomko

##### Well-Known Member
The Atlas and Redstone look great together. Here are mine.
DT

#### dtomko

##### Well-Known Member
Hmmmmmm. It's strange how the middle cone has a shorter shoulder than the other two. The tips look narrower as well. My BMS cone looks like the center one.
DT

#### sandman

##### Well-Known Member
dtomko,

That's 'cause the one in the middle is a Mercury Capsule and the two on the ends are Gemini Capsules!

But obviously (to me) NOT the same scale!

Also...it looks like one of our members here is bidding on them already.

#### Stymye

##### Well-Known Member
I just got back to my scratchbuild
I'm attempting to build mine without the fins
I just hope both motors light because they are canted.!
I made a cone for it last weekend out of hard wood, so it's much heavier
I still need to trim the tip and and carve the window details,after a little more sanding it will be ready to assemble .

#### dtomko

##### Well-Known Member
That's 'cause the one in the middle is a Mercury Capsule and the two on the ends are Gemini Capsules!
D'Oh! I guess I was fooled because on the old old Estes Mercury, there was a hollow in the main part of the capsule around which the paper wrapper went. Still, the Geminis look odd to me; they seem to have part of the instrument shroud built in before the part that goes inside the BT. The BMS/Estes cone doesn't have that.

#### sandman

##### Well-Known Member
I have two of the BMS Gemini cones and they fit a BT-70!

They have the transition already on them.

#### dtomko

##### Well-Known Member
Actually, the one in the middle is the Gemini and the two outer ones are the Mercurys. You can see the difference in the upper sections. Looking at the Ninfinger site, in the Estes Custom parts catalog, Estes made two different Mercury capsules, one for the paper wrapper and another plain-sided one. These are the plain ones. You can see the Gemini (44) and 2 Mercury cones(47 and 49) in this diagram.
BTW, BMS makes two different Gemini cones, one for BT-60 (the Estes clone) and one for BT-70.
DT

#### JStarStar

##### Well-Known Member
Yeah, the issue is that the Gemini capsule itself is slightly smaller diameter than the Titan booster, thus you have the tapered white transition section (the instrument module)...

I think the old Estes kit had a BT-60 centered inside a BT-70, with a cardstock tapered adapter section. You could either do that, or simply make the transition section as part of the nose cone itself, and just go with a BT-70 body and no interior tube (except maybe a stuffer tube from the motor mount.) Gord, I think that has to be what you have.

The Estes kit design (BT-60 mounted inside BT-70) would probably allow you to actually do the cutaway open section between stages 1 and 2 (the same problem you run into with a Vostok/Soyuz) - that's an idea.

I like stymye's idea of flying one without the fins - with CG far enough forward so it can be "body-stable" ...

That's where that big hunkin' BT-70 cone might come in - that would have to be packing some weight - or you could always drill & fill, too...

We'll see. A lot of interesting possibilities.

#### Silverleaf

##### Well-Known Member
Originally posted by dtomko
The Atlas and Redstone look great together. Here are mine.
DT
Thats It !

For the last couple months I've been searching off an on trying to remember who had made clear booster fins for their Atlas, and it was you Drew !

You posted a pic a long time ago of these same clear booster fins, up close, laying on their side. I've since lost that picture, but
I've got to ask you Drew, how in the world did you make them ?

What throws me off is how clean the seem looks, and what type of tubing did you use ?

Essentially, I'm asking for directions on how to make these.

Cheers my friend,

#### dtomko

##### Well-Known Member
R.S.,
The thread with other pictures and info is here:

https://www.rocketryforum.com/showt...perpage=20&highlight=estes atlas&pagenumber=2

If that link didn't come out, it's in the thread called "Estes Mercury Atlas." I got the tubes from a Red Arrow Hobbies tube assortment, and I glued them inside the Estes ones which I cut down.

Getting back to the GT, I don't think I would try flying it without fins, especially if one engine doesn't light.
And now I know why BMS makes two Gemini cones, and why one costs twice as much as the other. The BT-70 size one comes with the transition as part of it.
DT

#### GuyNoir

##### Well-Known Member
Originally posted by JStarStar
Has anybody scratch-built a GT anytime recently?
I flew my scratch build Gemini Titan at the ROCI launch in Muncie, IN at the end of September. Here's some particulars:

BT-70

twin mini-engine (A3-4t) powered

BMS Gemini cone, BT60 sized, with a paper adapter for the equipement section

Clear plastic fins mounted through the wall

BT-70 finished by scaling the exterior drawing located at:

https://www.ninfinger.org/~sven/models/titan_II/tii_dwgs/tii_dwgs.html

This really makes the model a snap to finish, but you've got to have a printer of sufficent size to do the job, and a full copy of Adobe to scale it properly.

The bird's not very heavy (I confess I haven't weighed it), and thus it performed very well. About 300 fee or so, high enough for good chute deployment, but keeps the flight in front of the crowd the whole time.

I'll see if I can snap a picture this weekend and post it.

#### teflonrocketry1

##### Well-Known Member
As I have mentioned before instead of clear plastic fins try a clear plastic cone (transition) cut from a large clear soft drink bottle. The cone skirts around the lower portion of airframe and also doubles as a stand for the rocket. Since the cone is clear and fits all the way around the tube there is only one critical and visible tube to fin joint.

Bruce S. Levison, NAR #69055

#### GuyNoir

##### Well-Known Member
Originally posted by teflonrocketry1
As I have mentioned before instead of clear plastic fins try a clear plastic cone (transition) cut from a large clear soft drink bottle. The cone skirts around the lower portion of airframe and also doubles as a stand for the rocket. Since the cone is clear and fits all the way around the tube there is only one critical and visible tube to fin joint.
Brilliant idea!!

But what glue do you use to attach the cone to the tube? I thought those PET bottles wouldn't work with nearly every form of glue known to man.

#### JStarStar

##### Well-Known Member
Originally posted by narprez
Brilliant idea!!

But what glue do you use to attach the cone to the tube? I thought those PET bottles wouldn't work with nearly every form of glue known to man.
I wonder, maybe, could you use nylon screws to attach the clear plastic bottle-skirt to the base of the rocket - drill a couple of holes on the bottom motor mount ring, and use nylon screws to bolt the clear plastic skirt on for flight - then for static display, out come the screws and off comes the plastic skirt??

Hmmm.

Another idea, if you had a bottle with a wide mouth - wider than your motor mount diameter ... like maybe one of those big orange juice bottles??

Could you take the bottle cap and drill a circular hole in the center, big enough to admit the motor mount, then cement or epoxy the bottle cap jacket to the base of the rocket ... then the clear plastic bottle skirt could simply screw onto the base of the rocket, using the bottle cap threads.

EDIT: I was out grocery shopping tonight and I happened to pick up a gallon bottle of Ice Mountain Water. The water tastes ok, but i don't really care about that, it's the BOTTLE I'm after.

The gallon bottle is four-cornered - a rounded square shape, clear plastic - no tinting - very clear - and also is fairly thin and light plastic. Should be easily cuttable with a utility knife. Many fruit juice bottles LOOK OK but are far too thick and heavy to use on any low-power kit.

The Ice Mountain also has a threaded bottle cap on the top that is slightly larger than the diameter of a BT-60 (About 1/8 larger.)

This means that you could hollow out the center of this bottle cap and have plenty of room to fit an 18mm (BT-20) or 24mm (BT-50) motor mount inside it. (Maybe enough room for a 2 x 18mm, if you were careful )

If you could figure out an adhesive or bolting system (maybe a pair of bolts in the base of the rocket, and lock-slots drilled into the bottle cap??) to attach that threaded cap on the tail end of the rocket, you could simply screw on a set of conical fins cut out of the Ice Mountain bottle, and fly the rocket that way.

I think you'd probably pick up a lot of exhaust grit on the fin-cone every time you flew, but the plastic-bottle section would probably be disposable anyway - if it gets grungy, just buy another bottle of Ice Mountain water, drink it, and cut yourself another fin-cone.

Hmmm. Thanks to the magical Mr. Sandman, I have BT-60 and BT-70 Gemini cones down in my parts box... might be a way to make that happen... lol

#### rokitflite

##### Well-Known Member
Hi Guys,
Actually in that Ebay listing the nose cone in the CENTER is the Gemini capsule Estes part #BNC-60AB. The ones on the outside are Mercury capsules that Estes made that were not in any kits #BNC-60T. They did not require the paper wrap like on the K-41 kit which were not listed in the catalogs as available separately. If you recall the BT-70 GT nose cone was JUST the capsule portion, it did not have that service shroud section behind it like the plastic cone to the BT-60 kit.

#### JStarStar

##### Well-Known Member
Originally posted by teflonrocketry1
As I have mentioned before instead of clear plastic fins try a clear plastic cone (transition) cut from a large clear soft drink bottle. The cone skirts around the lower portion of airframe and also doubles as a stand for the rocket. Since the cone is clear and fits all the way around the tube there is only one critical and visible tube to fin joint.

Bruce S. Levison, NAR #69055

OK, here is a pic of the Ice Mountain 1-gallon water bottle I referred to higher in the thread.

It turns out, that when you remove the bottle cap, a BT-60 would fit over the mouth of the bottle, except for the raised cap threads. It matches exactly the diameter of the cylindrical section below.

So the trick would be, to use a razor saw and cut this bottle off very carefully just below the neck of the bottle, where the threaded section begins. If this is done in the right place, the remaining bottle section should slide as a nesting fit over the BT-60 tube.... obviously, affixable by using a fillet of epoxy around the base of the rocket.

These bottles are very clear plastic, not super thick and heavy, can easily be cut in a shorter length to form a fin-skirt, so at least my guess is they would be a good solution for the question of clear plastic fins on a BT-60-based model. For bigger tubes, the fin-skirt could just be epoxied to the base of the rocket (or attached by screws, etc.)

So anyway, I'm gonna try that. A Gemini-Titan using BT-60 as your mainframe, I think would have to use 13mm motors. 18mm motors would be way too wide in proportion to the mainframe to be even close for scale purposes.

hmmm... I'm a little dubious. I may do it anyway. But to make a decent scale model, I think if you're gonna go with 18mm motors, your body has to be at least BT-70.

#### teflonrocketry1

##### Well-Known Member
Cool! That's not quite what I had in mind, but it should work as long as the motors are located near the base or bottom of the cone (bottle) since the Krushnic effect should still be in effect.

Bruce S. Levison, NAR #69055

#### te_groen31

##### Well-Known Member
Hello,

About a year ago I started drawing a scale 1:96 Gemini-Titan.

I'm still fiddling with the engine section. A lot of work. A lot
of small parts that need to fit nicely.

But 2005 promises to be a good year. A lot of "almost-finished"
models will finally be finished.
(GT, Delta IV, Japanese version of Delta: the N2 and H1,
Atlas V( later this year), Zenit SL-3, Vanguard, and most
definately several versions of the Russian R7/A2 !!! )

The Gemini-Titan will be one of those. I'm drawing the
GT 3 and 8 mission. Why those two ?
No particular reason. Just for fun. And because of that yellow
band at the top of the fuel tank.
One version with, and one version without the band.

In the attachment you can see a picture of this model. I
enlarged it to scale 1:48.

And pleeaaase... don't mention the Saturn rocket. It looks
horrible, I know.... It only took me 2 weeks to build that one.
And an un-be-lie-va-ble amount of glue to stick all that
cardboard together....................

Some models will have very low detail, some will be almost
photo-realistically rendered. Will take me well over a year
to draw. Have to hurry to get the Soyuz rocket finished.
Our Dutch Cosmonaut André Kuipers will sign this model,
late this year.
I decided this model just HAS to stand out above all others.
Above ANY space model......on internet.
I may not succeed, but I WILL try !! ;-)

Greetings,
Erik.

#### DeWain

##### Well-Known Member
TRF Supporter
I'm also planning on building a 1/54 Gemini-Titan, but this will probably be a 2006 project. Thanks for the info on the BT 70 nose cone that comes with the equipment section.

Does anyone have any tips for detailing the capsule/ nose cone? I plan on carving out the window recesses, but I am at a loss as to how to try to emulate the stringers/ribs of the capsule.

Thanks,
DeWain

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
[Although that does bring me up to what I see as my late-winter PMC project... I got ahold of a couple copies of the AMT "Man In Space" 1/200 model collection... and also a 1/200 Hasegawa Shuttle kit .... I could probably convert them to fly as follows:

Mercury-Redstone ... MMX motors
Mercury-Atlas ... 13mm Mini-motors
Gemini-Titan ... 13mm Minis (or maybe 18mm)
Apollo-Saturn 1B ... standard 18mm A-C
Apollo-Saturn V... 24MM D/E
Shuttle - 24MM D/E

Ahh, well, plenty to keep busy.... [/B][/QUOTE]

Did the very same project a couple years back. You've got a couple of the motor selection to consider. Mercury Atlas flies great in a single Micro-Maxx motor my original set-up for the Genimi-titan was for 10.5mm A's but I've retrofitted it for 2 Micros works fine. the Saturn_V Honks on a single D12, Off set thrust on the Shuttle makes it a bit squirelly on a D12, but is underpowered on a C6, Haven't tried a C11 I haven't finished the paint jobs on the saturns and shuttle so No pic's but heres a composite of the other 3....HO I almost forgot... Don't throw away the LEMS either they fly very nicely with a MMX motor

TRF Supporter
Heres the LEM

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
Originally posted by teflonrocketry1
For PETG I have used hot melt glue.

There is a commercial product available for bonding PETG; IPS Weld-On #3 (methylene chloride) but I haven't tried it:

https://www.craftics.com/products.cfm?Category=80&cfid=2221007&cftoken=6340385

IPS Weld-On #55 is a two part adhesive that is also supposed to work for PETG.

Bruce S. Levison, NAR #69055
Bruce:
MC works really well just be careful with the very thin PETG, it eats it up very quickly.
Have you tried Weld-on 16? designed for Lexan, I'll get it a try soon.

#### dtomko

##### Well-Known Member
As I am still waiting for plastic for my Buran project, I decided to start the G-T clone. Here's the motor mount next to the BMS BT-60 transition-less cone. JStar, Andy, how are yours coming? Mark, I would love to see a picture of yours with the wraps. Erik, how is the paper version coming? (so many questions . . .)
Drew Tomko