Dr. Zooch Return To Flight Space Shuttle build thread- #2

[luke strawwalker]

Since the crash of TRF wiped out all the great info on the Zooch Shuttle build, and since I bought one of these kits last October, and since I figured I could use some more 'conventional' glider experience before diving into my Zooch Lifting Body rocket, and since it's great fun to do build threads, I offer the Zooch Space Shuttle build thread #2...

I wanted to start this last week but was 'unavoidably detained' by work and home issues which lasted on into this week, including missing work yesterday morning to take my sister to the ER after she passed out in her bathroom from dehydration brought on by stomach flu. 3 IV bags later she was much better and sent home just in time for me to make my afternoon bus route.

Anyway, I'm starting from scratch and there's a lot going on around here still, and this is a lot longer build than I've undertaken lately, so the build part of this thread is going to be an ongoing effort for awhile. I hope you guys will pitch in with your experiences, tips, and ideas as we go along, and maybe we can reformulate a lot of the good information that was in the original thread, now lost.

First off, I've been reading the instructions and checking over the parts list. Everything looks to be there and in good order. The instructions seem to be fairly involved but this is a fairly complicated kit, so that's to be expected. The parts and stuff look to be the usual high quality yet no frills Zooch stuff I've come to expect.

One thing I've had to learn is, to just trust Wes's instructions and go about building the kit pretty much as he describes, though sometimes I DO switch the order around a bit, working on something three steps ahead while waiting on the glue or paint to dry on something else, just to shorten build time. Sorta 'parallel development' in ant scale... The reason I mention this 'trusting the instructions' is that I've gotten rather used to having to 'second guess' the instructions that come with a lot of rockets made by the largest model rocket manufacturer who shall remain nameless... I've found that some of the materials they use and procedures they recommend are 'less than ideal' or rather shaky, and leave some DEFINITE room for improvement. I've even learned not to trust all their motor recommendations, through bitter experience of late. Having developed this 'healthy skepticism' of the kit instructions, transferring that over to Zooch kits became habit, but I've learned that, "Hey, whaddya know, Wes really DID do his homework and wrote instructions that work, what a refreshing idea"... I hear Master Yoda's voice behind me telling me, "You must UNLEARN, what you have LEARNED". While I have a few tricks that make things easier, I haven't found any obvious "gotcha's" in the Zooch kits or instructions, unlike some of my recent experiences with the big "E".

So, let me return to my reading and get organized and we'll get started. More later! OL JR

 

[Saluki]

Looking forward to this build thread. I have read your others and I am sure I will pick up some tips.

Thanks.

 

[luke strawwalker]

I'm hoping that Dr. Zooch will chime in here and repost the formulas and methods for doing the 'Zooch treatment' for painting the ET... Of course with old Krylon now joining the dodos and dinosaurs, we'll probably have to come up with something new for those unable to locate the Old Formula Krylon colors required...

The reason I mention this now is, I'd like to do a paint test to see if I can make it work, and familiarize myself with the technique.

Here's a tip I've found so far... Look for Krylon Farm and Implement paint... It still seems to be the old formulation so far... After scrounging through all the local hardware stores and auto parts and farm stores, I came up with:

1. one can of Krylon Rust Tough Ruddy Brown Primer, #9204
2. one can of Krylon Farm and Implement Old Equipment Yellow, #1819
3. one can of Krylon Farm and Implement Allis Chalmers Orange, #1820

Now, there's a small problem here from the original "Zooch method": The recommended Orange was "Pumpkin Orange". I checked at Grainger's and from what they could find out, Pumpkin Orange is no longer available in the lacquers-- it's not in their catalog, in searching their system and vendor info they couldn't find any current mention of it, and I've only found it in the new Krylon formulation, which would be of dubious use applying it with the lacquers, even as a 'mist treatment'. Maybe it would work, maybe not, but I'd do a paint test first on a spare tube. I did some comparison shopping and it appears that the Allis Chalmers Orange is just a little darker than the pumpkin orange, but I bet it ends up virtually identical, since I've painted stuff AC Orange before and it's pretty darn bright! Certainly not dayglo but it's a pretty vibrant orange! Old Equipment Yellow is pretty hard to find too; from my comparison shopping, the New Caterpillar Yellow appears just a shade darker than the OEY. Perhaps going with something like John Deere Yellow, which is just a shade brighter, coupled with the shade darker AC Orange would offset, but I don't know for sure... test, test, test...

If the Doc will repost his 'Zooch method' and some pics, and if I can duplicate it decently on a test tube, I'll spring for a few cans of more readily available competitive products and see if I can't get a good match.

Someone else (sorry escapes me at the moment who) suggested "Totally Tangerine" in New Krylon as a good match for the ET, so if yall have pics to demonstrate, I'd love to see em!

More later! OL JR

 

[foose4string]

JR, I wouldn't be overly concerned with the colors. You don't want a dayglo orange, but anything in the Pumpkin ballpark should work. The OT is always in some flux between yellow and a brownish orange, so anything in between should do ok. One color that comes real close to the actual OT is Krylon Farm and Implement #1809- School Bus Yellow. It's more of an Orange if you ask me. Seems like it's the old stuff, but I can't swear to it. Same cap as the old. I have yet to use it on a Zooch OT but I have sprayed it on my Semroc Hawk and it seems like a great color for this. Sounds like your implement paints ought to do the trick.

As long as you have a good base with the Ruddy Brown primer, your yellows and and oranges are going to darken over the dark base coat. Those colors are always a bit transparent anyway and take multiple coats to get the intended color. That's why we generally like white base coats for yellows, oranges, reds, etc...so they show up with more vibrancy. Obviously, we don't want that here and are only doing very light misting coats over the dark primer until we get the desired color.

Mine were built before all of this Krylon old formula/new formula nonsense. I used Ruddy Brown, Pumpkin Orange, and Sun Yellow(barely).

 

[mjennings]

I shot mine with an airbrush and used Testors Model maters paint, Chrome yellow, Afrka Braun, insignia red and rust. I can't recall the ratios off the top of my head, I'll look tonight (probably something like 10 : 2 : 2 : 1). The ET was a near exact color match to the shuttle on my mission patch poster.

 

[Fred22]

Instead of cutting all those strips of paper for the segments in the srb's I used dental floss. Looked great and not nearly as much work
Cheers
fred

 

[mjennings]

Well I went to post last night and accidentally blew my post away.

Color application was as follows
base coat of white
1st color coat was Chrome Yellow with some Afrika Braun '42 mixed in
2nd color coat was Chrome Yellow with some Afrika Braun '42 a small amount of Insignia Red to get it to orange up, and some Rust or Burnt Sienna.

I couldn't find the mix ratios on my computer so likely they got blown away in TRF 1.0. The paint mix in the cup look almost like an orangy salmon color, I was about to toss it then thought "Hey you spent so much time mixing this up test shoot it through the airbrush and see what she looks like." It came out exactly like I wanted!

I'll try to get pictures up tonight.

EDIT:
Below is the link to the build thread in the archive and my color mix.
https://www.rocketryforumarchive.com/showthread.php?t=43486
"I am very proud of the ET. All Airbrushed with model master paint. I used a white (a glossy Insignia white I believe) base coat, followed by a 2:1 of Afrika Braub '42 and Chrome Yellow FS13538. This provided a nice yellow foam base, that I think looks similar to what I remember the foam patches from the tank that got hailed on last year. It went on more yellow than I expected but worked well. Then I mixed the same Chrome Yellow with a few drops of ancient ... Insignia Red FS31136, and Burnt Siena. It looked like I melted a Salmon colored crayon in my mixing cup, and was tempted to chuck it and try again, however, I thought the last mix was a lot lighter when I sprayed it so I dumped it in my color cup and dusted a paper towel and I was surprised that it came out exactly how I wanted. Two light coats later I have a tank that is fairly uniform in color"

 

[Micromeister]

I agree, the foam covering color has changed a good bit over the years.
I used a darker brown on my estes shuttle stack, but it still came out OK.

 

[luke strawwalker]

I got some of the new flavor Pumpkin Orange today to do some test shots... and I also lucked out and actually found a few cans of ORIGINAL Krylon Ruddy Brown Primer #1317! I think they had the better part of a case. There were a few older colors still there-- Celery, that 'appliance baby blue' and other weird/odd pastels that I pretty much puke at, but no Original Pumpkin Orange, and I've been looking for that stuff EVERYWHERE for a good while, so it's pretty much gone AFAICT.

Anyway, gotta head to the bus barn soon but I'll try to do some test shots tomorrow... OL JR

 

[Dr.Zooch]

Here's the original spray instructions- NOTICE: THIS MAY NO LONGER WORK with the "new" formula spray paints

1. Start by spraying it with a base coat of Krylon "Special Purpose" Farm and Implement Weather Guard protection paint- #1819 OLD EQUIPMENT YELLOW. Which is a brownish yellow.
2. Then I arm-length, distance sprayed a light coat of Krylon #2411 PUMPKIN ORANGE GLOSS to add some orange.
3. Then I very lightly arm-distance sprayed a smekeling of Krylon Rust Tough Enamel Primer #RTA 9204 RUDDY BROWN PRIMER to show aging of the ET foam.
4. Puff-distance spray alternating coats of each to make the ET as yellow, orange or brown as you desire.
5. Then after allowing it to dry, I taped and covered everything except the intertank and did another distance spray of RTA 9204 to make that area stand out.
6. Trim the LOX tunnel and other areas with Testors 1167 tan.

Note also that you can use this method to represent different tanks. More orange on the intertank gives you STS-114 where more brown gives you the tanks prior to the super light weights and more yellow gives you the tanks fresh out of the production hangar.

 

[luke strawwalker]

Here's the original spray instructions- NOTICE: THIS MAY NO LONGER WORK with the "new" formula spray paints

1. Start by spraying it with a base coat of Krylon "Special Purpose" Farm and Implement Weather Guard protection paint- #1819 OLD EQUIPMENT YELLOW. Which is a brownish yellow.
2. Then I arm-length, distance sprayed a light coat of Krylon #2411 PUMPKIN ORANGE GLOSS to add some orange.
3. Then I very lightly arm-distance sprayed a smekeling of Krylon Rust Tough Enamel Primer #RTA 9204 RUDDY BROWN PRIMER to show aging of the ET foam.
4. Puff-distance spray alternating coats of each to make the ET as yellow, orange or brown as you desire.
5. Then after allowing it to dry, I taped and covered everything except the intertank and did another distance spray of RTA 9204 to make that area stand out.
6. Trim the LOX tunnel and other areas with Testors 1167 tan.

Note also that you can use this method to represent different tanks. More orange on the intertank gives you STS-114 where more brown gives you the tanks prior to the super light weights and more yellow gives you the tanks fresh out of the production hangar.

Thanks Doc that's what I needed... I'm going to try to do some tests this weekend, probably with rolled up posterboard (don't have enough 'spare tubes' lying around, I don't think) and see how it turns out.

I'm going to do a little 'science experiment' with different stuff to see how it looks... I'll post pics when I'm done.

Later! OL JR

 

[mjennings]

Pics (reference my post above for more details)

White base coat


first color coat


compare shot


mix cup


well if it comes out wonky you can always do tiny tan splotches on the nose and have it be STS-117 that got hailed on 2007

 

[Dr.Zooch]

That looks pretty good.

Everyone keep in mind that the people who print posters and books cannot get the color dead on- because, as has been correctly stated here, it is constantly evolving as the sun's light ages the foam. Likewise, the photos from the internet are never dead on either, because of how colors are sent across the net (such as "internte safe" colors) and when they re-mix on your computer has more to do with how the machine is programed to restore the pixels than the actual colors. Thus- as long as you avoid day-glow orange, it'll be good enough for most people.

Also keep in mind that when your shuttle flies, they last thing people are gonna notice is the ET color- they'll be too busy getting "wow'ed" by the shuttle flight itself.

foose4string's is one of the best paint jobs I've seen- in person and on the net.

 

[mjennings]

That is True Wes, I have a few pictures from lets say a paper airplanes throw away from the tank, I'd take my stack up and do a shot but I doubt they let me get it up the elevator (as much as I would like to! And if the Orbiter slipped of and glided to the ocean I think I would cry, not to mention the trouble I'd be in). I was just very pleased that I got something that looked very right and didn't accidentally wind up with a tank that looked like a road cone!

Like I mentioned about the 117 tank the difference between the original aged foam and the repair filler

Pictures found at Kennedy Media Gallery (https://mediaarchive.ksc.nasa.gov/) and Wikipedia

 

[luke strawwalker]

That is True Wes, I have a few pictures from lets say a paper airplanes throw away from the tank, I'd take my stack up and do a shot but I doubt they let me get it up the elevator (as much as I would like to! And if the Orbiter slipped of and glided to the ocean I think I would cry, not to mention the trouble I'd be in). I was just very pleased that I got something that looked very right and didn't accidentally wind up with a tank that looked like a road cone!

Like I mentioned about the 117 tank the difference between the original aged foam and the repair filler

Pictures found at Kennedy Media Gallery (https://mediaarchive.ksc.nasa.gov/) and Wikipedia

That'd be easy to do if you wanted to replicate that exact flight tank... just load up a stiff bristle brush with some cream colored paint and "flick" it onto the tank by running your finger over the bristles as you wave the brush in the air...

Course it might make a mess of you and whatever area you're working in as well... OL JR

 

[foose4string]

Thanks Wes. Seems I have been doing the colors in the wrong order from how you have described the process. Doesn't matter much IMO, so long as there is some combination of Brown, Orange and Yelllow(spray can method). One other thing to note, I try not to spray too heavy with the gloss colors since I don't really want a slick, shiny surface. I like Wes' verbage..."smattering". Doesn't hurt to give it a shot of flat Crystal Clear in the end.

Of course, it's hard to beat a good airbrushing job like Mjennings did. Being able to mix the paint ahead of time is always a plus. I really need to practice with mine.

 

[Dr.Zooch]

Thanks Wes. Seems I have been doing the colors in the wrong order from how you have described the process. Doesn't matter much IMO, so long as there is some combination of Brown, Orange and Yelllow(spray can method). One other thing to note, I try not to spray too heavy with the gloss colors since I don't really want a slick, shiny surface. I like Wes' verbage..."smattering". Doesn't hurt to give it a shot of flat Crystal Clear in the end.

Of course, it's hard to beat a good airbrushing job like Mjennings did. Being able to mix the paint ahead of time is always a plus. I really need to practice with mine.

Actually, I was thinking your order was better than mine. Way more logical.

 

[mjennings]

Thanks Foose, that was actually my first time mixing my own colors for the airbrush!

 

[luke strawwalker]

I did the paint test today while changing the oil in my wife's truck late this afternoon, but I didn't have time to get any daylight shots today... yall will have to settle for kitchen table shots and flash shots til tomorrow.

I started with a ~3 inch tube that I had on hand (shipping tube) that I covered with typing paper last night to avoid the 'fuzzies'. I performed three tests on three seperate types of materials just to compare/contrast. It was rather windy today so I painted them in the farm shop, which isn't lit too well, so please forgive any blotches...

I can't figure out how to insert the pics into the text so I'll just do a couple seperate posts for the individual tests. First, the family photos. The first shot is natural incandescent light and the second and third are flash. The fourth and fifth are daylight shots.

More to come. OL JR

 

[luke strawwalker]

Okay, test 1 consisted basically the way Dr. Zooch explained how to do the paint job on the tank. I started off with a base coat of Krylon Farm and Implement #1819 Old Equipment Yellow, which is basically old Caterpillar Yellow. Next I did a mist coat at a distance and making FAST passes with the can with the closest thing I could find, which is Krylon Farm and Implement Allis Chalmers Orange #1820, instead of the recommended Pumpkin Orange which I cannot find anywhere. Lastly I made a mist coat at a distance with fast passes of Krylon #1317 Ruddy Brown Primer, which I wanted to try in lieu of the Krylon Rust Tough Enamel Primer #9204 which I have and is recommended, just to see how it would work. I found that I didn't have quite the coverage I wanted, so I went over it again with a second mist coat of all three colors until I had the coverage and color balance I was looking for. Basically I only gave it a couple minutes to 'tack up' between each coat.

I notice in looking closely at the finished product, that the Old Krylon produces the most 'pebbly' surface of the three tests. If feels like 220 grit (or maybe a bit finer) to the touch. The colors are well blended, but perhaps a tiny bit grainier looking than the other two. Overall I think it looks great.

Here's the pics... First a natural light shot, the second is a flash shot, the third is a daylight shot, and the fourth is a closeup with the camera on macro mode.

 

[luke strawwalker]

For test 2, I switched to "new" formula Krylon. I started with a base coat of "Bauhaus Gold" which is a little darker, golder yellow than the sun yellow. Next a mist coat at high speed with "Pumpkin Orange", followed by a mist coat at high speed of the "Ruddy Brown Primer"

A word of warning... when you buy a can of NEW Krylon, before you leave the store, pop open the cap and make sure the "new improved" turnable fan nozzle is intact... there is a red nozzle 'body' and a small white plastic wedge-shaped nozzle that snaps into it, and when I opened my can, the white nozzle tip was missing from the nozzle body. I figured "so what" since I was putting on the base coat and didn't need fine atomization, and the stuff just puked out all over the test object and me. Improvising I snatched the nozzle body and tip off the Pumpkin Orange and interchanged the nozzle throughout the rest of the test. I have to say I HATE the new nozzle-- it puts out a LOT of paint, and it doesn't atomize worth a darn. The droplet size is really too big for my liking. To get a 'mist' coat on the part, I had to hold the can about 2-3 feet back and "whip" the can past the tank tube at high speed to get a light enough coat-- if you move slower you will get too much paint on and cover up your undercoat. Krylon REALLY screwed up, because they could save a ton of money and have a lot better results just going back to a plain-jane one-piece push button nozzle like the cheapy paints have. The 'solid cone' nozzles on the cheapy paint atomize MUCH finer and are 'omnidirectional'. I just tipped the can on it's side since I didn't want to get more paint on me realigning the 'handy' twist flat fan pattern nozzle on the new Krylon.

I found that I had to 'work more' with this paint but the finished result is more than acceptable. You really have to 'whip' the cans around to get a light enough coat, and I had to make 2-3 coats to get the coverage and blend and color matching that I wanted. It laid down smooth, much smoother than the OLD Krylon, without the 'pebbly' sandpaper grit-like effect, but it certainly didn't lay down 'gloss smooth'. There is still a slight texture to it. I'd say it works pretty darn well, considering.

Here's the pics... first a natural incandescent light shot, the second is a flash shot, the third is daylight, the fourth is a closeup with the camera in macro mode.

 

[luke strawwalker]

Lastly, for the third test, I played around a bit with different brands of paint, just to see if they played nice together, in what I call the 'hybrid test'. It's also likely to be the cheapest test, which appeals to me since I'm a cheapskate

First I laid down a base coat of Walmart house brand Colorplace #20011 Red Primer, which is almost a match for the Ruddy Brown Primer but only 99 cents a can. Next, a mist coat of NEW Krylon "Pumpkin Orange" and then a mist coat of New Krylon "Bauhaus Gold". I had to make 2-3 more coats to get the coverage and color balance I wanted, but it went slightly easier now that I had some experience with the New Krylon. The Walmart Colorplace Red Primer has a plain-jane solid-cone spray pattern nozzle, and it goes on finely atomized and very smooth. Of course the New Krylon has those stupid flat-fan pattern two-piece twistable nozzles that put out thick, coarse, and fast.

Up close, the finished product is certainly the smoothest of the three. It feels pretty darn smooth to the touch, though it's not 'gloss smooth', but definitely has less 'tooth' than #2 and OBVIOUSLY less than #1. The color itself looks slightly less well blended than the others, giving it a 'grittier' appearance despite it's smoother finish. It looks something like a pattern a printer might produce on VERY close inspection. At a foot distance beside me now, it looks virtually identical to the others.

Here's the pics-- first the natural incandescent light, the second is the flash pic, the third is daylight pic, and the fourth is a closeup on macro. Hope this helps folks contemplating how to do the foam color. More later! OL JR

 

[Fred22]

It's good of you to go to all that trouble luke. I am taking notes for my next shuttle build
Cheers
fred

 

[luke strawwalker]

Thanks Fred... glad I can help

I edited all the above posts to add daylight shots and some closeups done with my camera in macro mode. Zoom in and you should be able to see the relative graininess of the different paints, and even the surface texture.

For reference, here are some pics of a chunk of hot stuff foam I pulled off the bottom corner of my brother's shop yesterday evening, taken in daylight. He told me it's been exposed to the sun for about six months or so.

Yall have a good one! OL JR

 

[Dr.Zooch]

GREAT JOB luke! We're all learning here!

 

[mjennings]

Nice work, looks good!

 

[luke strawwalker]

FINALLY... now that spring break is here, I can actually get down to the build!!!

I started off using the provided tube marking guide to mark the main BT-60 External Tank tube, which is the backbone of the stack, for the positions of the Solid Rocket Boosters, the Shuttle attach pad, and the engine hook locations. These are all clocked at the cardinal points to each other like fins. I use my handy angles to square the lines down the length of the tube.

OL JR

 

[luke strawwalker]

Next up, put a line the squarely along the length of the SRB. Mark the tube at 13/16 from the bottom end, and cut the SRB aft cones from the wrap sheet, and glue them up. I took my handy-dandy hemostat clamps over to the shop last week and took the die grinder to them, and carefully and lightly ground the teeth off of them, making them smooth jawed. Now they work GREAT for clamping up stuff like the SRB aft cones while the glue dries.

I also took the nosecones outside, for both SRB's and the ET, and hardened them with CA glue. Then, I sanded them lightly to take the hardened 'fuzz' off them, and tried out my new tub of wood filler with microspheres. This stuff goes on like concrete, as you can see in the pics. It does sand out well though-- after you take 99% of it off.

I went ahead and worked on the SRB's while the filler was drying, by installing the SRB aft cones, and their stiffening rings. I carefully trimmed the rings down at an angle with a NEW hobby knife blade (don't try using a used one; you need the keenest edge you can get for this) and then just lightly finish sanding them. I think they'd have turned out a bit nicer if I'd just sanded them to the taper as the instructions indicate, but I'd have ended up sanding for a LONG time and figured I'd try trimming them down, but if you do, I'd advise a little more finish sanding to get them down smoother than I did.

Once I test fitted everything, I glued it up and left it overnight to dry. OL JR

 

[luke strawwalker]

This morning I went back to work on the SRB's. I noticed that I stupidly overlooked something in the instructions, which is, that I should have pushed the SRB aft cones and stiffener rings up to the 13/16 mark on the tubes, instead of leaving them flush with the aft end of the tube. So, I have 'nozzleless' SRB's. I went ahead and carefully cut out the SRB wraps from one of the wrap sheets, and rolled them up tight to preform them. (One other thing I'd advise with Zooch kits-- pull the wrap sheets and instructions out of the kit and store them flat under some heavy books or something for awhile before you build the kit-- they're shipped rolled up tightly inside the main body tube of the kit, and sometimes they're rolled the opposite way from how they go on the tube because of how they're printed on the sheet, so storing them flat for a while really helps later on to get them to go on nicely) I glued the edges per the instructions, aligned the edge with the line on the tube, and carefully rolled them on. I decided to just trim the little bit of ring from the top, that should have been on the bottom if I had put the aft cones and rings on right, so the wrap would be flush with the top end of the tube and the front edge of the aft cones as they were meant to be.

I put the SRB together to see how they looked, and set them aside to dry.
I also went ahead and sanded the cones down to get them smooth and ready for priming.

The BT-60 ET cone has some unusual instructions. The noseweight is offset to counteract the weight/drag of the shuttle orbiter hanging off the side of the tank, so you roll the cone (be sure you sand the filler down smooth before you do this, so it rolls easily and true) and let it rock back and forth to find the 'top' of the cone opposite the offset noseweight. I marked the 'top' with a small tick mark, and then put a line along the cone shoulder about 15 degrees off clockwise as the instructions indicated, where the cable tunnel will later go. This 'clocks' the counterweight opposite the orbiter when preparing the stack for flight. I went ahead and masked the shoulders with masking tape, and primed the cones.

More to come... OL JR

 

[luke strawwalker]

I also went ahead and installed the intertank wrap on the ET tube. It consists of a piece of corrugated cardstock paper that simulates the corrugated stringers of the intertank region on the shuttle ET between the oxygen and hydrogen tanks. Wrap it around the ET carefully, and mark where it overlaps so it can be cut to the proper length. While you've got it wrapped, I'd recommend going ahead and carefully drawing a line around the top edge of the wrap 1/4 inch from the top edge of the tube-- this helps to roll it on straight. Not in the instructions and not completely necessary, but it helped me Anyway, once you've marked the wrap, carefully cut it to the proper length per the instructions, apply white glue to the back of it, and carefully roll it onto the tube. Be sure you clock the seam to the proper line as indicated in the instructions. It looks really good once it goes on.

Now here I'm going to depart from the instructions for the aft end of the ET tube. The kit includes a cut-out from the wrap sheet for a conical shroud around the engine mount tube to the ET body tube to simulate the aft Hydrogen tank dome, which on the real ET is a spherical/ellipsoidal structure consisting of curved tank dome gores welded together. I wanted to replicate this 'rounded' look a little better than a tapered shroud would do, so I put on my thinking cap and started looking around for 'round stuff' that would be lightweight and of the proper size. I finally found something suitable, and so here goes.

I started off by 'borrowing' the foam egg container from the refrigerator. Luckily we were about out of eggs and so between breakfast tacos and transferring what was left to another package, we now have our raw material. Invert the egg container and inspect the rounded foam cups the eggs sit in. I had a couple that were wrinkled, dinged, or had some small holes punched in them from the egg packing machinery. Once you locate a few nice looking egg cups, get a fresh SHARP hobby blade and carefully cut them out. My egg container had rounded 'troughs' between the egg cups to strengthen the container-- carefully cut straight down through these and then link the cuts together around the circumference of the egg cup. The corner ones work especially well for this, if they aren't dinged or wrinkled. You might even volunteer to help with the shopping and buy the eggs yourself, and make sure you get a nice egg container for the purpose. Of course you might also get some funny looks, inverting several packs of eggs in the store to find the nicest egg container Just explain to anyone who asks that you're looking for the perfect aft space shuttle tank dome, and they'll be satisfied that your nuts and will go away and leave you alone. Of course they may also call security, so don't dawdle-- pick a good egg container and let's go.

Once you've cut out the egg cup, put it rounded side up on your workbench. Mine had a small 'flat' area at the bottom apex of the egg cup. Carefully center your BT-20 engine tube from the kit on the flat bottom center, and outline it with a pencil. With your sharp hobby knife (I keep saying sharp, because don't try to reuse a blade you've already cut balsa and paper with, as the egg foam will tear rather than cut and look horrible, forcing you to scramble (hehe, a pun) to find another egg cup suitable for carving, and hopefully you'll have switched to a sharp blade by then and don't haggle it all up too) Anyway, carefully cut the hole out of the bottom of the egg cup for the motor tube. It should be a fairly snug fit so cut precisely on the line or just inside it. Remove the divot from the center and test fit it on the motor tube.

This is where it gets interesting, and what took me a couple tries to figure out. Now you have to mark the side of the egg cup so it will precisely fit up against the ET tube. First, test fit your centering rings for the motor mount inside the tube, and sand to fit nicely if required. Mock up the engine mount, and slide the rings inside the ET tube, BUT DON'T GLUE UP ANYTHING!!! This is strictly installing the centering rings in the ET tube with the motor tube slid into the rings. Push the bottom ring up inside the ET tube about 3/8 inch, to make room for the 'dome' over the motor tube to slide up inside the ET tube. Slide the tank dome over the motor tube, domed side down, and slide it down the motor tube until the outer edge is flush against the ET tube. Then, carefully holding it tightly against the tube, mark it all the way around with your pencil. This will mark the dome square to both tubes. Take the dome off. Now, carefully trim the dome, ABOUT 1/16 INCH OR SO PAST THE PENCIL RING (ON THE LARGER DIAMETER PART) you just drew on the dome when you marked it against the ET tube. This will allow for the proper clearance to make the dome sit FLUSH with the outer edge of the ET tube when it's glued on. You don't want it hanging over, or not coming to the outside diameter of the ET tube when it's installed. Carefully cut off the excess ring to create the dome. Test fit it over the motor mount parts-- remove the motor tube and pull the ring flush to the rear of the ET tube, reinsert the motor tube, and carefully test fit the dome over the motor tube. It doesn't matter if the motor tube sticks out past it at this point-- this is strictly to test the fit of the dome against the bottom of the ET tube. If it's overhanging the edge a bit, creating a 'lip', carefully trim it again with your hobby knife, very gently carving off a small ring around the edge until it fits flush. Be careful to trim it squarely as you go-- keep the cut parallel to the pencil ring drawn around the dome. Eh viola-- instant spheriodal tank dome!
While you have the motor mount parts installed in the ET tube, go ahead and push the motor tube ALMOST FLUSH with the bottom of the 'dome'. Remove the dome, and make sure that the aft motor mount centering ring is flush with the bottom of the ET tube as per in the instructions, and then reinstall the dome, and make sure the motor tube is just BARELY protruding from the dome, and once you're satisfied everything is properly located, remove the dome and mark the motor tube where it enters the aft centering ring, so you can install the centering ring on the motor tube in the proper place. Also mark 'bottom end' or something on the motor tube, so you don't put it together upside down. Remove the motor tube and centering rings from the ET tube.

You can now assemble the motor mount as per the instructions. The lower centering ring SHOULD be almost exactly 3/8 inch from the rear edge of the motor tube, as the instructions indicate. Once the motor mount is assembled, install it in the ET tube as the instructions indicate, with the aft centering ring flush with the aft end of the ET tube. Be sure to clock the engine hook to the proper point on the side of the ET tube, as indicated by the marks on the template in step one. Take the tank dome, and trim a 1/8 inch by 1/8 inch square out of the engine tube hole on one side, to clear the engine hook. Once the motor mount is glued in, go ahead and glue on the tank dome with white glue. Smear a good coat inside it, put a bead around the edge of the tank dome, and smear a decent coat on the OUTSIDE END of the motor tube-- BE CAREFUL NOT TO GET GLUE INSIDE THE MOTOR TUBE, and then slide the dome over the motor tube, aligning the 1/8 inch square notch with the motor hook, and then CAREFULLY put a VERY THIN bead of glue around the edge of the tank dome where it joins the motor tube. AGAIN, BE VERY CAREFUL NOT TO GET ANY GLUE INSIDE THE MOTOR TUBE. Smooth the edge where it joins the ET tube as well. Don't worry about smearing excess glue over the dome itself; we'll have to 'paint' it with a few layers of glue to seal it for priming and painting anyway. Just make sure the glue is smeared on smoothly.

Here's the pics. The first pic is obtaining sample tank domes from the egg carton, the second is marking the engine tube on the bottom flat, the third is the engine tube hole cut in the bottom, the fourth is the 'mocked up' engine mount centering rings and tank dome almost ready for marking, and the fifth pic is how you mark the outer circumference on the tank dome. OL JR