# Dr. Zooch Mark II build...

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#### luke strawwalker

##### Well-Known Member
HI! Here's a build thread of the Dr. Zooch Mark II. If you're not familiar with Dr. Zooch's products, be sure to check them out at https://www.drzooch.com/ as he has a TON of cool LPR semi-scale (ant scale) rockets. These are builder's kits, so if you're a BAR this will REALLY take you back-- no cheap plastic RTF stuff here... it's up to you to make it as good as you can, and if you're a noob, you'll learn some skills along the way while having fun. This kit is 'loosely' based on the Gemini/Titan II, and it's a pretty neat little fun representation of it when it's done!

Let's get started. First, the kit comes in the usual Dr. Zooch 4x4x12-ish inch box, which is terrific for storing the finished model as well. After checking all the parts and reading the instructions, I dove right in. This is a pretty simple kit but pretty interesting and a few challenges come along the way, depending on your skillset and level of craftsmanship you desire. The kit consists of a BT-50 body tube, a balsa nosecone and noseblock, and a balsa 'seal disk', cardstock paper pre-printed wraps, including nosecone wraps, BT-20 engine mount and associated parts, motor hook, trash bag chute, fin material, and associated hardware. I was surprised to find some kevlar for the shock cord in with the kit. It was a bit frayed and the ends unravelled a bit, but for a light small rocket like this it should be fine, especially after minor re-winding.

The first step is the capsule. The balsa nosecone needs a small 'step' filed/sanded into it, where the conical part of the Gemini capsule meets up with the cylindrical thruster section above. The capsule is turned with a "rounded" edge here that you sharpen into a distinct line by sanding. It's not too difficult with a little 60 or 80 grit sandpaper, the recommended nail file (which I didn't have) or a small file. Once you've got that, carefully, and I DO mean carefully, cut the capsule wrap out of the sheet and glue it together. You'll learn how to get a steady hand and use your hobby knife carefully here, if you want a good job. Glue it up with white glue, which is recommended throughout for the wraps, and let her dry. I'd recommend cutting pretty much dead on the lines, or JUST outside of them, as the Zooch wraps are an EXCELLENT fit. ( I cut the first couple wraps 1/32 or so outside the lines, and had to go back and retrim them, the fit was that good) Main thing is, take your time, and test fit first just to make sure. Once it's glued up and dry, I test fit again and did a little minor shaving of the edges before gluing it to the balsa nosecone. It fit perfect. Repeat for the thruster cylinder band and the upper instrument compartment and nosecap. The little black 'dot' nosecap is the hardest wrap in the whole kit to cut...

The instructions advise that you can fill the upper instrument compartment cone with white glue to 'solidify' it. One word of warning-- wait until it's securely glued and glue dried to the upper end of the nosecone before filling it with white glue. Who knew a paper cone could float in white glue?? Luckily I caught it before the glue ran, and I cleaned up the mess, drained the glue and let the cone dry before refilling it. I did deviate from the instructions one tiny bit, in that I installed two small paper 'tabs' in the top of the instrument compartment cone before gluing it on. I've used this trick before making paper rocket nozzles, to connect the two halves, and it works great-- far easier than trying to make a butt glue joint between two peices of paper! You can see the small 1/8 x 1/4 tabs in the capsule pics.

Here are the pics and we'll continue in a moment... Enjoy! OL JR

#### luke strawwalker

##### Well-Known Member
Ok, so I finished off the nosecone by going over the top instrument cone and disk seams and the seam to the thruster cylinder with a Sharpie. The color didn't quite match, so I went over the sides of the instrument cone and top dot to get it matched.

Next, the motor mount. The Mark II uses a distinctive and quite inventive motor mount design that incorporates a conical rocket nozzle at the base of the motor mount, which looks REALLY cool. Start off with the usual method of making a motor mount-- cut a slit, fit the hook, etc. The first difference from what I'm used to (Estes style motor mounts) is that you cut out a 'reinforcement band' from the wrap sheet, put a layer of white glue on the back, and wrap it around just below the engine hook top slit. This reinforces the motor mount tube. Install the motor hook as normal and give it a couple wraps of electrical tape to secure it. Now to the second deviation from standard motor mounts-- take the lower centering rings, 20-50's, and make sure they fit the motor tube, sand slightly if necessary. I tested mine on top of the tube above the motor hook. Once you have a nice fit, you'll have to notch the inside of the ring, approximately 1/8 inch wide or so, about half the thickness of the ring. Carefully cut about halfway through the thickness of the ring from the inside, move over a bit and repeat, then carefully lift the squares of paper out of the cut to make the groove. Install the ring over the motor mount per the instructions. Repeat these steps for the third motor ring that goes at the base of the motor mount tube. Cut the engine nozzle from the wrap sheet, curl it, glue it up with white glue, and let it dry. Again, cut basically right on the lines, as it was a perfect fit.
Notch the engine bell per the instructions to clear the motor hook and allow it to move, and glue it in as instructed. Finish the motor mount off by gluing up the third ring to the motor tube and bottom of the rocket nozzle cone. Lastly, notch the third ring from the outside as per the instructions to clear the motor hook for installing/removing the motor.

More to come! Here's the pics... OL JR

#### luke strawwalker

##### Well-Known Member
Next, measure off an inch from the bottom of the body tube. This line will be where the bottom of the body wrap will go, and the fins mount on the exposed tube below it. Then, either use the doorframe method or your handy-dandy tube marking angle to put a straight line down the length of the tube. This is the wrap seam line. Once you've done this, carefully cut out the wrap (cut on the line, it fits good) using a straightedge and then apply glue as per the instructions-- I had my doubts but it works. Put 1/2 wide 'smear' of white glue all the way around the edge of the wrap and across the red 'seperation line' between where the upper and lower stages seperate to keep the edge tight to the tube when you cut the tube apart later on. Line it up carefully along the tube length line and on a clean surface (don't want glue mess or dust/crud to discolor the wrap) roll it onto the tube, and work the seam edge down by rolling a sharpie along it, kind of burnishing it down. If you did a good job you'll hardly be able to see the seam! I also use this seam line to locate the bottom fin and launch lugs.

Install the motor mount as instructed. Be sure to leave half the second (middle) engine mount ring protruding from the body tube as the instructions indicate-- you want to be able to use the cool booster stage Dr. Zooch is developing for this rocket and turn it into a two stager later on, right?!? This is the 'stage coupler' for that lower stage. Anyway, be sure to turn the motor hook to align with the body wrap seam-- makes the rocket look cooler

Next, carefullycut along the red line on the tube wrap. You'll have to make 3-4 passes with your hobby knife, so go slowly don't rush, slip, cut yourself, or goof up the tube/wrap, and don't try to slice through all at once. Once the blade breaks through on the third or fourth pass, you can insert the blade and gingerly finish the cuts as you turn the tube. Freehand tube cutting takes some effort, but the skill is well worth it. Once the 'upper stage' (actually a cargo section) and lower stage are seperated, gingerly deburr the inside of the tube ends with the edge of the hobby knife, scraping NOT cutting! Now she's all dressed up and ready for the next step...

Here's the pics... to be continued... OL JR

#### luke strawwalker

##### Well-Known Member
Moving on, we get to the fun stuff.... Now you get to see just how good you are!

Start by cutting the 'blowout panels' out of the 'upperstage' body tube. They are the four small black rectangles just under and opposite the main black bars of the roll pattern on the upperstage tube. Carefully score them several times with your hobby knife until you cut through; I cut the two long sides first and then turned the tube 90 degrees in my hand to make the two short 'end' cuts. Once you cut through, gently lift the panels free. Cut all four out.

Next, get a pair of reading glasses or a magnifier, and if you're like me drink something to give you a steady hand... LOL This is where it gets interesting! Carefully cut the yellow tank dome from the wrap sheet-- it's the yellow 'flower-looking' thing. (Yeah, at first I thought Wes's daughter had hacked into his graphics program and put flowers on the wrap sheets to dress them up too, but this thing DOES serve a very cool purpose!) Once you've liberated the tank dome from the wrap sheet, VERY VERY CAREFULLY cut through the gore lines on the dome radiating out from the center. The gores stay attached to the center of the dome, but you cut to the outer edge. Once you've accomplished this feat, and had another drink of something to steady your hand again, get your white glue and start gluing the gores back together, overlapping them behind each other as shown in the instructions. There are the tiniest glue tabs I have EVER seen on the edge of each gore. Of course I flubbed this up, and having fat, cut up, smashed up old hands, I luckily could resort to my collection of surgical hemostats to actually get the overlap right and clamp it up to dry. Be careful though, as too much glue softening the paper or taking too big a bite with the hemostat will screw it up, as you can see in a couple spots in the pics. There is definitely a learning curve here, but if you can do this and pull it off perfectly, congratulations you're now an excellent candidate for being a successful neurosurgeon! Seriously though, while stretching one's capabilities, it's certainly not impossible, and if you flub, oh well, it's inside the rocket and the only way you can see it is by looking through those itty-bitty blowout panel holes you just surgically-precise cut!

Ok, here's where I deviated from the instructions a tiny bit. I figured 'one cool deal like this deserves another'. There is a 'seal disk' in the kit, used to seal off the upper cargo section from the blowout panels and to-be-installed tank dome below. So, I fitted this seal disk to the tube (had to sand a smidge off for a smooth easy fit) and then upended it, and put centering marks on it using my steel ruler. Then I traced the antenna canister/instrument cone outline from the wrap sheet onto typing paper, and cut that out. Then, I traced around that cutout typing sheet pattern back onto an unused side of the cardstock wrap sheet, and cut that out with my hobby knife and glued it up into another paper cone. This will be the upperstage rocket motor. Titan II's used 'fire in the hole' staging-- the upperstage rocket motor ignited while the lower stage rocket motors were still burning, but about to burn out. That's what the 'blowout panels' are for: to vent the rocket motor starting up. This negates having to have ullage rockets to slosh or 'seat' the propellants against the bottom of the tanks and fill the lines like would be necessary had the first stage motors already had shutdown. (Hey, this WAS the dawn of the space/missile age after all; gotta shave some risks and complications out somewhere! ) Anyway, once you've got this new paper cone, center it and glue it up to the seal disk, NOT the weighted bulkhead The seal disk is much thinner than the bulkhead. This will represent the upperstage rocket motor visible inside the blowout panels just above the tank dome on the finished rocket.

Next, I'd recommend going over the now hopefully completed tank dome with a good smear of white glue front and back and let it dry again. It took me three steps to glue all the gores, and I popped a couple trying to 'kneed it with my thumbnail to give it a domed appearance' per the instructions, so I reglued that busted gore seam and gave it the once over front and back with a little more glue to help strengthen it up. Once that's dried, then work it a little to 'round it out' some.

Coat the screw eye thread with glue and screw it into the bottom side of the long weighted bulkhead, opposite side from the weighted filler plug. I had the screw eye bottom out on me and hit the weight, and refuse to screw in all the way, so after three tries I moved over and screwed it in at an angle to get it to screw in all the way. I used Titebond II dark glue for this for added strength. Using white glue, paste the now finished tank dome on top of the bulkhead, covering the weighted filler plug. Center it up as best you can.

Test fit it in the upper stage tube, and test fit your upper seal disk and rocket nozzle, but DON'T GLUE IT UP YET! Mark the bulkhead so you can replicate the depth. You want the tank dome visible but not even with the blowout panels.

Also, since I have a pico-altimeter I might want to fly in this rocket, I drilled a 1/4 inch hole up from the bottom of the seal disk inside the upperstage rocket nozzle for an altimeter vent. You can omit this step if you don't plan on ever flying an altimeter. Paint the seal disk bottom surface and outer rocket nozzle Testor's #1180 steel, and the inside flat black, and set it aside to dry...

More after the schoolbus route and enjoy the pics! OL JR

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#### luke strawwalker

##### Well-Known Member
Okay, when we last left Batman, he was... oh wait a minute... the Mark II, yeah...

So, next I did the fins. I like papered fins, for the added strength. Since the fins on this kit are 1/16 balsa, it's probably not a bad idea. Cut the fin template from the wrap sheet, and align it with the grain as marked, and outline the fins on the balsa. Cut them out with your hobby knife and stack them, sand them to final shape, and using a sheet of typing paper cut in strips, paper the fin. Coat one side with glue (I used Titebond II dark), note which is the leading edge (has the small rounded corner from the leading edge with the grain parallel) and put it face down on the paper with the remainder of the strip ahead of the leading edge of the fin. Squirm it around a little to make sure the glue is spread, and press it down firmly, then coat the backside with glue. Fold the fin over onto the paper, keeping the paper tight against the leading edge as it's folded over the leading edge. Press firmly and work any bubbles or excess glue under the paper out by pressing from the center toward the edges. By the time you've done this, any glue squeezed out around the fin should have softened the paper a bit; take a rounded smooth object (Sharpie cap/opposite end, rounded hemostat end, whatever) and run it around the outside tip edge of the fin that will be out in the airstream. Gently burnish the paper down over the fin edge, especially around the curve at the fin tip/leading edge junction. Set them aside to dry. Once they're dry, I lop off the excess paper with scissors, and then carefully cut them out with the hobby knife, and then trim the edges with the hobby knife of all excess glue and paper until it's all flush with the edge of the wood. Be especially diligent trimming the root edge so you get a good glue joint. After trimming and light sanding of the edges, flat to true everything up, then lean the fin over at a 45 degree angle and very lightly draw it toward you to shave off any paper 'fuzz' on the fin edge, flip and do the other side. I then wicked a small amount of CA along the outside tip edge of the fin and the curved part of the leading edge to make sure the paper is set for good at the edges, and to harden the balsa and paper. I started the double-glue joint by applying a small amount of Titebond II dark along the root edge of the fin and standing them up aside to dry.

Next, and the instructions don't really elaborate here, but mark the tube for the four fins. I don't have a tube marking "bullseye" so I wrapped a spare strip of printer paper around the tube overlapping itself, marked the end, took it off, measured it in millimeters, then divided by four and put three extra marks on the strip at 19.5 millimeters apart to properly space the four fins. Wrap the strip back around and tape the ends together, turn to align the end with the wrap seam mark along the length of the tube from before, and then mark the location of the other three fins. Remove the strip, and with your doorjamb or handy-dandy aluminum angle/tube marking jig, extend the lines from the mark square to the tube. Since the launch lugs will be located on the seam line, put the fins just to one side. I gently sand off a strip about 1/8 inch wide behind the line (to the right) to get rid of the glassine to get a strong glue joint. Rotate the rocket in your hand so all the fins are mounted to the right of the line as you work your way around the tube sanding the glassine. Then apply a light smear of Titebond II dark and set it aside to dry. Within 5 minutes the Titebond should be plenty dry to glue the fins on. That is one thing I notice about the Titebond II; it seems to dry pretty darn quick! I do the fins on opposite sides of the tube so I can attach a "U" shaped piece of balsa to the fins with spring clothespins to hold the fins square as they dry, since I don't have a fin jig. Apply a light bead of Titebond II to the root edge, and press it to the tube over the dried glue on the tube and align with the pencil line. Hold for 20-30 seconds and it will be pretty well set. Be sure to do any alignment pretty quick, because the glue will 'grab' within ten to fifteen seconds. I like this method because it has a lot of the 'almost instant' benefits of CA without some of the drawbacks. I set the rocket aside with the balsa alignment jig clothespinned to the fins, and came back 30 minutes later and did the other pair of fins. Fillet with the Titebond "Molding and Trim Wood" glue. I read about this stuff on a forum and found it in the store, so I picked up a bottle to try it out. This is the first time I've used it, and I must say, "I'm sold"! It's thicker than wood glue, which helps it make and hold nice fillet shapes as it dries, so you can do the layups on ALL the fillets at one time, because as you work your way around, they will be 'set up' before you turn the tube over to do the other side. One word of warning though-- I tried to just smooth the fillet with my finger, and the glue seemed to want to come right off the rocket with my finger. A quick wipe off, reapply, and wet the fingertip before smoothing with water (I just licked my finger to be honest) and a quick swipe and the fillet is made! VERY slick! After the fins had dried and the fillets dried, I then went over the fins with a thin wicking of CA just to harden the balsa. I also wicked some CA into the paper rocket nozzle, just because I'm anal...

Do a light sanding just to take any 'grit' or hardened paper fuzz off the fins and smooth the CA down pretty, and you're ready to paint. I brushed on some Testor's "1180 Steel" per the instructions on the fins, tube bottom below the wrap, and I went ahead and painted the nozzle too. I could've done a better job painting, so I took a bit of 800 paper and lightly sanded the fins; actually broke through the paint in a couple spots, so I repainted after I took the pics and it looks MUCH better now. I just didn't see breaking out the airbrush for about 12 square inches of painting...

Here's the pics! Enjoy... to be continued... OL JR

#### luke strawwalker

##### Well-Known Member
Continuing, we now come to the famous "Dr. Zooch Trash Bag Parachute" with it's "Poly-Coated Popeilium Shroud Lines". I won't go through the details of that, just follow the instructions, and I recommend surgeon's knots on the shroud ends. I also rub a little white glue into the lines where they wrap around the snap swivel to make sure they don't slip and 'tilt' the chute.

Now, when I made the 'upperstage rocket motor' on the upper 'seal disk' I didn't account for it sticking down so far and moving the bulkhead up too far into the cargo compartment. After doing some trial fits, I decided that the nozzle didn't have to stick down 1/4 inch, so I carefully cut it down to 1/8 inch away from the seal disk by carefully cutting around it with the hobby knife. That allows the seal disk to ride lower in the tube, freeing up space in the cargo compartment. Once you're set with where to put the nozzle and seal disk, go ahead and smear some white glue around in the tube above the 'blowout panels' and install the seal disk. Insert the bulkhead and tank dome so they're visible inside the blowout panels, and make sure the upperstage 'rocket nozzle' (if you made one-- if doing the kit per the instructions just glue the seal disk above the blowout panels and put the tank dome where you want it. If you DID put in an upperstage rocket motor nozzle, be sure and leave a gap between the tank dome and nozzle so you can see daylight through the blowout panels between the nozzle and tank dome. It won't look right if the nozzle is right up against the tank dome.
Once the nozzle/seal disk is set, remove the tank dome bulkhead and apply a bead of white glue inside the upperstage tube end below the blowout panels, and reinstall the tank dome/bulkhead. Double check the spacing again to make sure everything is to your liking, and set aside to dry.

Install the shock cord mount (it's a regular 'trifold' style using kevlar). The launch lug is cut in half and one half glued to the top of the 'first stage' below the bulkhead seperation line, and the other is nestled in a fin fillet, aligned with the wrap seam. That way, the lugs, seams, etc. are all on the 'back' of the model. I usually cut the lugs at a 45 degree angle to make them a little less 'draggy' and make it look a little cooler.

So, that's it. Hoping to fly it maybe tomorrow. Here's the money shots. Enjoy! This is a fun kit to build and I'm really looking forward to the "Dr. Zooch Mark II Stage Zero" that is planned as an add on booster stage for this kit, to be released soon. Have fun! OL JR

#### Dr.Zooch

##### Well-Known Member
Terrific build!

A word about the Kevlar- I ordered a ton of it figuring it was the tight weave- it wasn't. The best way to keep it "together" is a method that Foose came up with- that is tie a series of knots about 2 inches apart going up the line. Even if you do not do this, however, keep in mind that Kevlar's strength runs ALONG the line- so even if it comes unwoven, it's still just as strong and will hold.

The Mark II is my favorite kit- I must have six of them around here- not counting my 3 cold-power Mark IIs and I have at least 15 of the capsules- 2 of which are ant-lofters. Too bad for the ants... I'll never grow up... if fact, I get paid to be a 14 year old again! I love my job

Luke! Give us a flight report! We're waiting...

#### snaquin

##### Well-Known Member
Nice build ..... especially the capsule. That was a great idea using the paper tabs to secure the instrument compartment.

.

#### luke strawwalker

##### Well-Known Member
Thanks Wes and snaquin...

Yes, the Mark II flew yesterday at our Challenger 498 club launch. The full photoset is available at https://groups.yahoo.com/group/Challenger498/photos/album/299508142/pic/list and I'll post a few pics here. I only flew the Mark II twice and spent the rest of the time playing with my new Fuji Finepix S2000HD digital camera, doing high speed burst mode liftoff shots!

Unfortunately I flubbed the pics of the Mark II-- I didn't prefocus on the rocket itself before liftoff, so the autofocus locked on the field in the background, so the focus is pretty soft... okay, very soft... okay, okay, it's just plain out of focus... (yall won't let me get by with claiming to be 'artsy' )

Anyway, the Mark II flew beautifully. After dodging some rain showers, I loaded her up with an A8-3 considering the wind, and put her up on her first flight! Straight up, arched east, popped the chute, and gently drifted down to the field about 50 yards from the pad... BEAUTIFUL!!! Next, I loaded her up with a B6-4, prepped, and sent her up... and up... and UP!! MAN that little bugger will flat scoot on a B6-4, even with my 'battleship' building techniques! She was just a dot in the sky when she popped the chute, and started drifting in the 10-ish mph east wind... she went about 150-200 yards from the pad, to the mid cross fence of the farm, but recovered perfectly! That Mark II is a NICE flyer!

Now, one of my club buddies read my build thread on here, and I realize I might have given a bit of a false impression. No, you don't REALLY have to be a brain surgeon to do the tank dome and blowout panels... Hey, if I can do it, anybody can ! I'm just learning like everybody else, and my hands are big and have been cut and smashed so many times doing farm stuff that I'm surprised they work as well as they do... so if anybody got 'spooked' by my attempts at humor on the tank dome and blowout panel work, don't worry... you'll do fine and it's good training for later more complicated modelling builds! Sometimes I'm too much of a smart@...

Anyhoo... here's the pics... Enjoy! OL JR

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#### luke strawwalker

##### Well-Known Member
Okay, here she is on a B6-4... the last set was an A8-3...

I'm glad I didn't try a C6-5... she'd have been TOTALLY out of sight on a C6-5! Especially considering the lousy conditions yesterday and the fact we ended up getting rained out!

Later! OL JR

Oh, BTW Wes, thanks for the build thread (pre-TRF meltdown) on your pad 34Z-- "Z" for Zooch!

The pad looks terrific! OL JR

#### Dr.Zooch

##### Well-Known Member
I normally fly mine on a C6-7... it's a "No Arc" flight- just keeps goin' up.

#### luke strawwalker

##### Well-Known Member
I normally fly mine on a C6-7... it's a "No Arc" flight- just keeps goin' up.
I'm walking to lose weight but didn't feel like walking to the next COUNTY! Maybe on a completely NO WIND day I'll try that, but that weren't yesterday!

Hmmm... methinks you're trying to get me to put her into LEO and end up having to buy a new rocket... LOL

Have a good one! OL JR

#### Dr.Zooch

##### Well-Known Member
Keep in mind that with the new Stage Zero, you can add about 700 feet to that altitude and if launched without the SRBs attached, add about 1,000.

Hey- Texas sky is really big.

#### luke strawwalker

##### Well-Known Member
How much altitude if you fill the upper stage with sand?? LOL OL JR