Note: This is the full text report with fewer pictures.  Visit Jeff's site for all the pictures.

Admittedly I was inspired by Andrew Waddell’s big Saturn V construction article on RocketryOnline. While the Saturn V is impressive, I am much more interested in the smaller Saturn 1b. In the past both Estes and Centuri kited model rocket versions of this NASA launcher. Of the two the Centuri version was much easier to build and fly. Estes had re-issued Centuri’s 1/100 version of the Saturn 1b in 1992 but it since has gone out of production. These two past versions were to be the basis for my upscale project.

One of the most troubling features in doing this model is the first stage booster tank tubes. There are very few commercially available body tubes that are sized correctly to evenly space and get a proper circumference for the fist stage booster. I researched and listed all commercially available body tube diameters then sat down at the UniGraphics terminal and built some CAD models. I eventually found out that a 2x upscale of the 1/100 Estes kit would fit what was available without having to resort to custom ordering. I ended up using Estes BT-56 body tubes for the first stage tanks surrounding a 54mm core tube. The second stage or more correctly the SIV-B stage would be a LOC 5.68” diameter body tube cut down to 4.75” (ala Andrew’s method for the Saturn V) The base of the first stage would be the stock diameter 5.68” body tube.

The hard part was now out of the way. I downloaded the plans for Estes’s 1/70 version of the Saturn from JimZ’s web site. These plans were invaluable for making the command module capsule, LES (launch escape tower) and the fin assemblies. I plotted the shroud for the LEM on the UG and printed it out full size. The pattern was transferred to poster board and cut out. All of the parts I used to construct the Saturn 1b are available through any supplier of high power and model rocket components. (I ordered everything through Magnum)

The kit was constructed very similarly to the Centuri/Estes version where by the rocket is built up and painted in various sub-assemblies then final assembled, detailed and applied decals. I will list each major component and the build process I used.

First Stage Fin/Tank Base:

For me this was probably the second most complicated item to do. If you notice on the Saturn 1b there is a shroud ring on the lower section of the first stage booster that surrounds the first stage fuel tanks. This shroud has scalloped cut outs to accommodate the booster tanks. I used the pattern from the Estes 1/70 plans and enlarged it to the size I thought I would need. I then made a poster board pattern and tried it out. It didn’t work too well. The reason was the lower body tube of the first stage booster needed to be smaller in diameter than the 5.68” one I was using. Since I didn’t want to cut this tube down and make more centering rings I needed to use something else. I finally hit on using thin 1/64” veneer ply. I cut out a single section needed to fair to the booster tank. I then split this in half, made a mirror pattern then glued a rib to the backside that would set the proper angle and setback from the core tube to the edge of the lower body tube. What I had now was one section of lower fairing that would go around one half of a booster tank tube on either side. Now I had to make eight of these. 

Veneer ply is very easy to work with and cut. You can use scissors or score with a knife and break it similar to sheet styrene. It is available at most hobby stores. A little pricey though for a sheet since it is so thin. I made my eight sections one at a time. First I cut the lower body tube to the right length, glued in the centering rings and marked out my eight equal sections. Then I started gluing the fairing pieces down using CA. I had little short sections of BT-56 left over from cutting the booster tubes to length and used these for spacing and fit checks. I did each section one at a time checking the fit and trimming where necessary. The total job took about two nights to do. But it was well worth it.

After the unit was filled and sanded I glassed it using ¾ oz glass cloth and epoxy finishing resin. The weave was then filled and sanded smooth.

Main Body Tube:

Next up was the main body tube. This started out as a 5.68” diameter LOC payload section. It was cut to length then run on a table saw lengthwise to remove enough material to reduce the diameter to 4.75”  I saved the section I removed to use as a joiner later. To get the tube to hold a circular shape I took the LOC 5.68/54mm centering rings and cut the diameter down to 4.75”  I did this by taping the rings together, marking the new circumference and trimming them on the bandsaw. These centering rings were what was used to keep circularity and diameter on the tube. The centering rings were inserted and the splice was epoxied in place with 30-minute epoxy then taped and left to dry. After the splice joint cured the centering rings were glued in place with 30-minute epoxy. There ended up being a gap between sides of the longitudinal cut in the tube. I filled this with scrap balsa and sanded it smooth. I then marked the upper end of the tube to trim off about a 1” section to be used as the base for the LEM Shroud/Command Module Stack.

Now it was time to apply the body wraps. I wanted to have the body corrugations on my model just like the full size Saturn 1b. I used Evergreen Styrene sheets with .10” ribbed spacing on them. These can be found in most hobby shops that sell model railroad supplies. There are many different sizes and styles. The sheets I bought were 6”x12” and come three to a pack. I used 3 packs for the body wraps. I measured off my 1/100 model and cut the sheets to strips of proper width. Since the sheets are only 6” wide they needed to be put on in sections to do the entire circumference. The only drawback to this whole process was the need for a good seam between joints. It turned out rather well. I masked off three or four rib spacings on either side of a joint, filled it, then sanded smooth. From three feet away you can’t even tell. Painting made it even less noticeable. The overall effect with the corrugations is well worth and minor cosmetic issues.

LEM Shroud/Command Module Stack:

For this assembly I used the ring previously cut from the main body tube, a cut down 5.68” tube coupler, a 3” LOC body tube, a ¼” thick ply 5.68”/3.00” centering ring reduced to 4.75” diameter, a poster board LEM shroud, a paper nose cone and a 3” tube coupler as a nose cone base.

I epoxied the cut down centering ring into one end of the main body tube ring. I left about an 1/8” exposed at the top for the LEM shroud to attach to. I then cut down the 5.68” tube coupler so it would fit in the main body tube. I left about an inch and a half shoulder to seat into the main body tube. The coupler also has a slot or keyway that fits the doubler in the main body tube. This feature prevents the nose section from rotating on the main body. After the couple tube is set and a good fit achieved I epoxied a solid ply bulkhead at the bottom of the couple ring. The screw eye of the recovery system will pass thru here and it makes a nice solid base. 

Next I epoxied in the 3” service module body tube. Alignment was an important issue here so I took my time and made careful measurements. This was to make sure that the completed assembly wouldn’t look crooked when the whole rocket was together. After the epoxy cured I installed the paper LEM shroud. I had drawn out and cut this pattern earlier then put it together using super tacky glue and an iron. Basically you attach the glue tab to one edge of the seam, let it dry then apply the same glue to the other half of the tab and let it partially dry. Let your iron heat up while you do this, not too hot though, about 300 degrees should be fine (I use a monokote iron for my model airplanes). You will also need a dowel of some sort to back up the joint when you iron it. I use a scrap piece of closet hanger dowel rod. Let the end of the dowel rod hang over the end of your workbench ans support it so it will take some pressure when you iron. Then tak your shroud, align and join at the seam, slip over the dowel rod and iron the seam. You won’t have to hold the iron there long. Move it up and down the length of the seam for a few seconds. The glue will re-activate from the heat and produce a strong bond.

I then fit checked and aligned the shroud to the body tube and base. When everything was where it needed to be I epoxied the assembly together. To make the shroud more durable I glassed it with ¾ oz. glass cloth and Z-Poxy finishing resin. After sanding to remove excess cloth I filled the weave with lightweight spackle and sanded smooth.

The Command Module capsule came next. I had sized the paper pattern from the Estes 1/70 scale version so it would fit on the 3” body tube. I photocopied it onto cardstock. The pattern has panel lines and details marked on it. Since my model will replicate an actual launch condition vehicle these markings are not required. The boost protective shroud is all white. The pattern on the Estes sheet is basically an arc and if you cut it out as shown by the lines you will get a conic section with no tip. That’s because the Estes kit used a balsa turning for the top of the cone. I modified the cut by extending the seam edges up to the theoretical center of the arc lines. When the pattern was folded and ready for joining I had a cone. There was a small hole at the tip due to the nature of trying to make a paper cone. I’ll tell how I dealt with this later. I overlapped and glued the seam with my super tacky glue and let it dry. I then cut a 3” tube coupler section to about 1” in length. This is the shoulder of the nose cone. Once again I measured carefully to make sure everything was aligned then temporarily CA’d the coupler in place. I then ran a bead of epoxy around the inside joint between the cone and coupler. A paper cone is a bit flimsy so it needed some reinforcing. I inverted the cone, mixed up a larger than normal amount of 15-minute epoxy and poured it into the inverted coned. This plugged up the small hole at the tip and added some nose weight. I used my heat gun for monokote to get the epoxy to flow better. Heating epoxy has the addd benefit of making it cure faster. After the epoxy cured I sanded the tip to shape and was ready to glass it. I glassed the outside of the cone with ¾ oz. glass cloth and Z-poxy finishing resin. I made sure to put tape around the coupler so I wouldn’t mess that up. After the epoxy cured I removed the excess cloth, filled the weave with lightweight spackle and sanded smooth.

I now needed to add some base pieces for the LES tower. These were 3/16” dowel sections cut with a matching angle to the capsule so the tops would be parallel to the ground plane. I held some sandpaper on the cone and sanded the mating surfaces of the LES bases to match the cones contour. After they were all shaped and correctly sized I CA’s them in place. I filled any gaps with liteweight spackle and sanded smooth. Next I located the centers on each dowel top and drilled a 1/16” hole for the support wire I was going to use to attach the LES tower to the nose cone. The basic LEM/Service Module/Command Module stack was now completed. There would be extra detailing to come later.

LES Assembly:

I wanted on this model a scale and durable LES (launch escape system) tower. I had previously made one for my Bocye Aerospace Redstone and modified it for flight use. That one had suffered minor damage from time to time but I knew I could build a better one. I decided to use brass tubing. The Estes 1/70 version came to my aid again. The LES tower for that version used wood dowels glued together. I would substitute brass for wood and solder for glue. I scaled the Estes plans accordingly and built a jig. All the horizontal crosspieces fit into the vertical legs because I drilled holes to accept them. These would be stronger joints because the parts would physically interlock and be soldered. I built the basic tapered box shape adding one side at a time. When I was done I carefully heated joints and aligned and straightened where needed. I then started to add all the little diagonal cross members. The central ring was formed around a 3/8” drill bit shank and the ends soldered together. The whole process was not that tedious and took me about two to three hours over two days. The end result was worth it.

For the top of the tower where it attaches to the rocket motor I cut out a brass circle and soldered it to the top. To this circle would be the lower shroud of the rocket motor and the motor tube and nosecone. The shroud was laid out and drawn on Unigraphics. The original Estes 1/70 kit had this as a balsa turning. The rocket body was a BT-5 body tube cut to length with a balsa nose cone from my designer’s Special box. The pieces were all test fit and then put aside for assembly later.

Fin Assemblies:

The fins for this rocket were built up assemblies using .040” sheet styrene and 1/8” aircraft ply. I used the same technique that Estes’ 1/70 version used with a few modifications. I sized the patterns from the Estes plans. Since the fins on the Estes 1/70 version were oversized for stability I knew that any enlargement would not be true to scale. This was fine with me since the model is sport scale and the extra fin area would help in stability. (more on this later)   I constructed a 3D model of the fin in Unigraphics and then plotted out all the required ribs full size for my patterns. The fin is a complex shape with tapers both running from leading edge to trailing edge and root to tip. I then made a flat pattern of the fin skin to use as a template. I cut all the pieces out at once for all eight fins. A tedious process but in the long run it saves time and provides a consistency between fins. I used CA to glue the ply ribs to the inside skin of one fin then CA’d the other skin on. CA glue does a good job of bonding wood to plastic. The fins are not designed to have TTW construction. I had toyed with the idea but after careful consideration and weighing my options I decided against it. The root of the fin has a lot of bonding area and attachment to the base unit using 30-minute epoxy should be adequate. (this model will never see rapid acceleration; slow liftoffs are the goal here)  After all the fins were assembled any gaps  were filled with lightweight spackle and then sanded smooth. Having fin skins of sheet styrene means less finishing and prep time for painting.

I now marked the lower body unit for the fin locations. The Saturn 1b uses eight fins so careful marking was essential. I then epoxied each fin one at a time. After the epoxy had started setting I used my finger, dipped in alcohol, to smooth a fillet between the fin and body tube. Eight fins to epoxy on with 30-minute epoxy can take a while. When they were all done I once again looked over all the joints and filled in with spackle and sanded smooth. 

The lower body unit has some corrugations on it as well and I duplicated these again with scribed styrene sheets used for the body wraps. These small sections were CA’d in place.

Miscellaneous Details: 

The outer body of the Saturn 1b has numerous conduits, ullage motors and fairings. I made these details from hard balsa carved and sanded to shape. The grain was filled in, more sanding and then they were primed and painted. These items will be glued to the body tube after it has been painted.

 The because of inaccurate body tube size relation ships when the lower fuel tanks are arranged around the core tube there is a gap between the fuel tanks when they are arranged. To fill this gap and to make sure when I installed the fuel tanks they would be straight I CA’d 1/32” ply strips along the length of the core tube. This filled the gap between the tubes nicely.

The model is intended to be launched off a ¼” rod and that is the lug size I used. I did not feel the need for a larger rod size because the model will not weigh that much when completed and it will not ever be launched in high winds. I positioned the lugs very similar to my 1/100 model. One lug on the lower body tube section near the fins and another one  on the second stage body tube. I had to line up the upper body tube and the lower one because they do require correct orientation to one another for conduit and roll pattern alignment with regards to the fins. The lugs were spaced off the body tubes to allow for the uneven diameters between them and I used a rod to align them while they were epoxied in place. When the rocket is final assembled a launch rod will be used again for alignment. 

Painting:

The rocket is now ready for paint. It was painted in sections very similar to the 1/100 Centuri version. This method involves less masking and easier handling of the parts. Even though there are only two colors, black and white, the various roll patterns and separation lines require careful masking and prep that a fully assembled model would make much more difficult. The paint I used was Krylon. It is a good all purpose enamel that goes on well and dries quickly. It also has the advantage of flowing the colors back together between coats because of the solvents used. (this can help if you get sags or minor runs)

I primed the main body tube and the core tube/fin unit. This helped show any defects or areas that needed more sanding or filling. The fuel tubes were painted directly (since they were already white in color and I did not feel the need to prime them), four black and four white. The capsule was painted glossy white separately as well as the LES tower and the LEM shroud adapter. I then painted the main body tube and core tube/fin unit glossy white. I let these dry for a day then masked and painted those areas glossy black. It is important to note that on the corrugated areas to get a good seal between the tape and the previous painted surface. This is to prevent the new color from ‘bleeding’ under the tape. It is also important to let the color coat dry for a few hours before removing the tape to prevent lifting or tearing of the new coat.

The actual service module was a polished aluminum in color. It almost looked like chrome. There are no real accurate chrome type paints. I could have used chrome self-adhesive monokote trim sheet. However, I did not have any and cleaning and use easily scratch the chrome in general. I did cover the service module section with aluminum colored monokote. This was then detailed with various pieces of white trim monokote to simulate panels and radiators found on the actual vehicle.

Recovery:

Recovery for the Saturn 1b will be very similar to the 1/100 scale version. It will come down in two pieces with the separation line being at the base of the LEM shroud to second stage body tube interface. The LEM/SM/CM/LES stack will come down in a nearly horizontal position via a single 36” parachute by use of a bridle fashioned from R/C aircraft control cable. This bridle attaches to an eyebolt at the base of the LEM stack and to an eyebolt screwed into a blind nut at the base of the service module. This eyebolt on the service module is removable for static display. 

The main body will come down via dual 36” parachute recovery. For the main body section I wanted to have it descend as close to vertical as possible to reduce stress on the fins at landing. This necessitates that the shock cord mount be as close to the centerline of the rocket as possible. There are two eyebolts on either side of the core tube in the parachute compartment. A bridle sling made of 3/32” A/C cable connected with quick links connects to an apex point a few inches above the center of the core tube. This is where the shock cord will attach and then continue to the parachutes. 

This rocket is not using any sort of altimeter based ejection system. The flight profile I intend will allow for a motor based ejection system. It might be possible to make provisions for one but I have not gone to the trouble to investigate the feasibility. 

Final Assembly:

After the various components are painted the rocket is ready for final assembly. The first stage fuel tubes slip into their respective positions and are lightly glued in place with super tacky glue. 

Next comes the main body tube to core tube join. The main body tube will slip over the eight fuel tubes and trap them into place. I put epoxy on the lower centering ring of the main body tube and slipped it into position. I used 30-minute epoxy so it would give me time to position everything for line up. Here is where I used my ¼” launch rod again to assure correct line up of the two assemblies. Once the main body tube was lined up I epoxied the upper centering ring to the core tube. I then set these completed assembly aside to dry.

I next attached the command module to the LEM/SM stack. This was a friction fit only. This will allow me to add any nose weight to achieve proper CG/CP relationship later. The LES tower is attached to the command module. This is a friction fit as well so I can take the tower off later for repairs if need be. The fit is very tight though so I am not worried about it coming off in flight.

Finishing/Detailing:

After all the epoxy has dried it is time to add the miscellaneous details. Using my 1/100 Saturn 1b for reference I attached all the ullage motors and conduits using super tacky glue to their correct positions. I attached the four vernier motors to the service module as well. I fabricated the four antenna boards from sheet styrene and painted them white with silver antennas. These were attached at the four locations on the first stage. 

A company in Texas called Model Graphics provided the decals for this model. They make custom vinyl self adhesive decals. I have used them before for custom work on my R/C airplanes. They do outstanding work. I sent them a .tif file of the decal set from Estes’ 1/70 kit and they were able to scale them to fit my 1/50 version. I highly recommend them. It may be a bit pricey but it is definitely worth it. Each set they furnish comes with complete instructions on how to apply their product. I also ordered a set of decals from Tango Papa custom decals. From these decal sheets I used the ‘United States’ words and flags on the CM and SM plus the various smaller target markings. Tom Prestia, the owner, has certain Estes decal sets available and will upscale them for an additional charge. These however, are water slide decals. So you will have to contend with silvering or clear edges if you don’t clearcoat.

Motor Mount and Stability:

I tried to model this rocket for CP using Winroc software. The only drawback was that the Barrowman equations for determining CP do not support an eight fin configuration. I used six fins and added 10% to the fin dimensions to allow for this. I also compared the balance point of the Estes 1/100 kit to this upsized version and it is very close. The calculated CP is 31.45 inches from the tip of the command module cone. I also believe that with eight fins the CP would move further aft. My actual CG is well forward of the calculated CP (27” from the tip of the CM) so I am confidant that this will be a stable flyer without addition of nose weight. 

Since the core tube is a 54mm diameter tube I used a LOC 54/38mm adapter. I assembled the adapted per the LOC instructions and epoxied it in place in the core tube. I used an AeroPac 38mm motor retainer. These things are the slickest set up going for my money. They are quick, neat and look so darn good.

Final Thoughts:

The all up weight for this rocket is 3 lbs. 12 oz.  Which is not very heavy considering what has gone into it. There were no real problems encountered while building this bird. I was able to make everything with relative ease using common materials. I flew the rocket at our club’s December 12th launch. Prepping went uneventful. I did not bring my dual 36” chutes for the main section so I used a single 54” ‘chute. Everything packed nicely into the recovery section with enough room. The motor was readied and loaded. The weather that day was perfect. No wind and clear skies. I got a far pad since this would be a maiden flight. I had the photographers ready. And I prayed. The motor lit right away and the Saturn left the pad very majestically (and stable). Then it happened. At about 300 feet the ejection charge fired prematurely. The rocket was still under boost from the H123. The LEM/SM/CM stack separated and went off to the side. Its recovery ‘chute deployed perfectly. However, the main section was another story. The air load ripped the chute away and actually broke the main bridle. The main section continued up for a little way, arced over then headed straight down for the ground ready to take a perfect core sample. Any doubts of stability were allayed. The main section headed straight in, struck the ground dead on and then bounced back into the air about ten feet, flipped end over end twice and landed sideways on the ground. There was a hushed silence from the crowd. My only thoughts were “Oh well, time to build another.” All that remained was the 54” ‘chute floating gently down. I headed out to pick up the pieces. When I got to the main body I was very surprised. The damage was very minor. I expected the whole forward section to be crumpled but it was not. There was no damage to the upper section, which recovered via the parachute and there was no damage to the fins either (this was always a concern of mine on this model). All in all I was very, very lucky that day. The damage has since been repaired and I awaiting the final coat of paint. All I did was remove the corrugated wrap from the damaged portion, straighten the tube and reinforce with CA then cut some new wrap and glue it on, paint and finished.

The model will fly again. Post mortem indicated from all witnesses that the ejection charge went off too soon. As to why this happened I am clueless. There may have been a void in the delay element. Since the motor was still under boost while this occurred it seems the most logical assumption. Never the less the Saturn will fly again. I have been told that my models are all too pretty to fly and that I must have nerves of steel to do this. But my thinking is I build them to fly, and if you fly ‘em they’re gonna break. You can always build another.  If you are interested in looking at any of my other scale models then you can visit my web page at: http://www.geocities.com/CapeCanaveral/Hall/4501/index.html

This was the only damage suffered on the model from its death dive. I was amazed to say the least. Fortunately we were flying in a recently tilled bean field and the ground was fairly soft. Even so an impact to the ground at over a hundred-mph is nothing to sneeze at.

List of Materials & Sources:

(1) 5.68” LOC payload tube   Magnum
(1) 5.68” LOC tube coupler   Magnum
(1) 54mm motor tube    Magnum
(1) 3” LOC body tube    Magnum
(1) LOC 54/38mm motor adapter  Magnum
(1) 3” LOC tube coupler   Magnum
(1) 5.68/3.00  LOC centering ring  Magnum
(4) 5.68/54mm  LOC centering ring  Magnum 
(3) ¼ x 20 x 1.5” eyebolts   hardware store
(1) 10-32 blind nut    hardware store
(1) 10-32 x 1” eyebolt    hardware store
(1) 3’ length 1/16 A/C cable   hardware store
(5) quick links     hardware store
(3) pk scribed sheet styrene   Evergreen
(2) pk .040 sheet styrene   Evergreen
(4) .185 I.D. x 12” brass tube   K&S
(4) .062 dia x 12” brass rod   K&S
(1) BNC-5S nose cone   BMS or Estes Designer Special
(1) BT-5 body tube (Estes)   Magnum
(1) .190” x  12 wood dowel   hardware store/hobby shop
(1) 1/32” x 12” x 24” veneer ply  hobby shop
(1) ¼” x ½” x 12” balsa stick   hobby shop
(1) ¼” x 3/8” x 36” balsa stick  hobby shop
(1) 1/8” x 6” x 12” A/C ply   hobby shop
(1) 38mm motor retainer assy   Aeropac International

Sources:

AeroPac International
Magnum Hobbies and More
Model Graphics
Tango Papa Decals
Evergreen
K&S Tubing
LOC Precision
Balsa Machining Service