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Random Thoughts on the Apogee Saturn V

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tbzep

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The following seven posts are a review and play-by-play construction of the Apogee Saturn V by Terry (P'rfesser) McCreary. They were originally posted to r.m.r. a couple of years ago. Part one was originally a stand alone piece about the body wraps, but several people asked him to comment on the complete kit, resulting in parts two through seven.

BTW, the P'rfesser also wrote "Experimental Composite Propellant", which arguably is the best book out there on motor making.

Enjoy!

tim
 

tbzep

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Just to set the record straight: this isn't a criticism of Tim's kit or techniques. I think the Apogee Saturn V is an absolutely beautiful kit, I'm thrilled with it, and if I had the money I'd buy a dozen. My building skills are rather limited; I've never built a kit as intricate as the Saturn V before. It's my hope that this post will help someone else that's been having similar problems.

The gluing of the wraps is the part of construction that scared me the most. Tim shows a construction technique using fast CA (thin). Someone else on RMR suggested practice, so I practiced the technique a
number of times using scraps from the the wraps. Now, some of the edge scraps are extremely thin and aren't going to glue down properly, so that a bad result on the scrap won't necessarily mean a bad result on the real thing.

BUT... I simply couldn't get the technique to work properly. Thin CA is a good solvent for polystyrene, and even the thicker scraps would dissolve and crack. (I think this is more of a comment on my lack-of
building skills than on anything else; I've never built a rocket this intricate before, and I've never used CA to build a rocket before.)

An alternative technique, which was very successful in my hands, uses medium CA instead of thin. [Warning: the CA I used was several months old, which may have something to do with the properties of the stuff. Anyone who wants to try this technique would be well advised to practice with scraps on a piece of body tube first.]

I found that the medium CA didn't dissolve the plastic of the wraps anything like the thin CA did. I could actually run a bead of medium CA and let it cure without the plastic dissolving at all. If you find that your medium CA dissolves the plastic too, it may be too fresh...

My technique was much the same as in the video, except that I carefully stretched and taped the wraps into place, and made sure that they were just where I wanted them and as tight as I wanted them, before gluing. Then I simply ran a bead of medium CA on the edges of the wraps, using a very fine tip on the CA container, and let it cure.

Using this technique, the thrust structure wrap (bottom) is actually more difficult to do than some of the others. I did glue it down first, but to get the proper feel and practice, it might be better to glue the intertank wrap first. The intertank wrap (just above the thrust structure) is a nice simple rectangle with no projections.

My cutting technique on the wraps was less than perfect, so the top edge of the intertank wrap snugged up nicely to the tube, while the bottom edge gapped away from the tube just a little, maybe half a
millimeter. I found I could stretch the wrap so both edges would touch the tube -- but that left a misalignment at the seam.

My solution was to ignore the gap at first, glue the "snug" edge down, then glue the "gapped" edge down a couple inches at a time. After applying the medium CA to the gapped edge, the bottom edge was pressed
to the tube and held there for two minutes (that's how long it took for the glue to grab really well).

When doing the thrust structure, the places between the four fairings were glued down first, just as Tim suggests. When that glue was completely dry, the fairings were done by applying a drop of medium CA
to each corner, and holding down the corners against the tube until the glue set. Then a bead of medium CA was run along each edge.

Here lies a problem with this technique. Medium CA is slower than thin CA, and polystyrene doesn't glue all that well to the paper tube anyway. That means that this method is significantly more time-consuming. In some places like the fairings, you have to do a little at a time, hold the pieces together for two minutes, then do a little more.

Another problem that I've already alluded to is the fact that for the most part, the wraps have to be very carefully taped into place and ready-to-go before you start gluing, because the medium CA takes so long to set.

I finished all the main body tube wraps in two days, except for the sticky-outy parts on the interstage wrap. Each sticky-outy part will have to be glued one at a time. That's going to take a good while. But hey. If'n I was in a hurry, I'd'a done it weeks ago.

Regardless of the technique used to glue the wraps, some practice with the scraps from the wraps will pay off handsomely.

Last comment for chemistry geeks: you probably know this already but if you can get 10-100 microliter plastic pipetter tips, they work quite well as extension tips for the CA bottle, and they're so doggone cheap that they can be thrown away after one use.

Hope this helps someone,
P'rfesser
 

tbzep

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The following are from my own experiences, YMMV and all the standard disclaimers.


Video instructions:
It should be obvious, but if you have the disk space to copy the entire instruction CD to the HD, you won't have to wait for a movie to load, listen to the whine of the CD, etc. Okay, it wasn't obvious to me until yesterday...


Gluing down the wraps, one more note:
The technique I described of using medium CA to glue down the wraps is leaving, in places, a tiny fillet that really should be sanded off. Another good reason to master TVM's use of thin CA for that purpose, since thin CA doesn't leave a fillet. Memo to myself on the upper stage wraps: wipe off any excess CA more carefully, while pressing the wrap into place.


Big couplers:
I made both of the large couplers rather a tight fit in the main tube. Better a tight fit than a loose one, I reasoned. Not a very good idea. The coupler for the upper section should indeed be a reasonably snug fit. However, if the coupler that holds the nozzles is a really tight fit, it will be difficult to remove the nozzle assembly. Since that assembly is just for display.... I'll have to sand mine a little.

Another reason for a snug-not-tight fit: the couplers will better fit the centering rings, making it easier to center them properly when gluing.


Cutting the wraps:
I found that by holding the knife at a very shallow angle, it follows the indentation better than if held high. You may find exactly the opposite. It's a personal kinda thing.

Nevertheless, in a few places the blade left the indentation. I ended up with wraps that had a less-than-perfect cut edge (uneven by perhaps a half-millimeter in a few places). I tried sanding the edge carefully with 400 grit paper. The wrap is too flexible to sand easily. Anyone else have a cure for uneven edges on the wraps? (those of you who have the kit will understand why a straightedge is kind of hard to use). Anyone really worried about it? Okay, so maybe I'm being just a little anally retentive here... :)

I started cutting with a brand new el-cheapo brand blade, and it wasn't new enough. (Memo to myself: buy some good blades. Or steal a scalpel from one of the bio profs' labs at lunchtime.)

Go ahead and cut the long edges of the wraps, but leave the ends uncut at first. Or at least leave them a little long. They have to be trimmed to length anyway, and you don't want to trim them too short.


1st and 2nd stage Tunnel Covers:
The long balsa tunnel covers weren't perfectly straight but are very slightly curved, maybe a sixteenth of an inch. That's not much, but you can run into a minor problem in "Orienting the Vacuum Form Wraps Part 2". A curved tunnel cover may throw off the alignment of some of the wraps just a bit. Solution: Draw a straight line on the tube where the edge of the tunnel cover is to go, and use it for alignment.

Presumeably anyone building this kit has seen TVM's errata page at www.apogeerockets.com/Saturn_errata.asp. Considering that there are ninety-odd pages and I-dunno-how-many movies in the instructions, he's done a tremendously accurate job.

P'rfesser
...having never forgotten any of my own mistakes, I've gotten very
good at repeating them, over and over...
 

tbzep

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YMMV and all the standard disclaimers.

Paper part of the big transition:
The CA glue coating didn't stiffen up the paper part of the transition as much as I'd have liked. I now wish I'd made another couple of transitions to go inside the one supplied. I would have made them of cardstock and about five millimeters shorter so they wouldn't foul up the fit at either end. Don't glue them in until the fit of the transition provided has been properly adjusted.


The big transition wrap:
Problem: The wrap for the transition is too short. Some of the other wraps have been a bit short, but I've been able to stretch them slightly to fit. On the big transition wrap, the ends meet but there's a smooth place about two corrugations wide.

Attempted solution: trim about a millimeter off the inside curve of the wrap. That cuts off the very ends of the corrugations. Now the wrap can stretch a little more. Unfortunately, there is no way it's going to stretch an eighth-inch. This trim that I did was probably a bad idea. I had to seal the ends of those corrugations before painting, so the paint won't seep underneath.

Possible solution: glue it in place and make a couple of plastic or balsa corrugations to fit in the space.

Actual solution: glue it in place, turn rocket so I can't see the blank space. :)

The conical shape makes it a little difficult to fit the wrap properly, tape it into place, and have it stay there. I need three hands and a prehensile tail, methinks. So: I got the fit correct, then slid the wrap forward a bit and taped the ends together. Then slid it back, pressing it snugly (not too hard) onto the paper
transition. Nice, tight fit and I can hold it with one hand, apply glue with the other, wipe it off with the third. No need for prehensile tail anymore...


Electronics:
Something I hadn't considered is electronic recovery. Shoulda-but-didn't: cut a 38mm hole in the forward centering ring, at the edge. Mount a piece of 38mm airframe tubing maybe 6" long aft of the centering ring, cap the aft end.

Since I didn't do any of that, I'll probably have to mount any electronics in the forward end of the 29mm motor tube. Or possibly glue a 29mm tube to the inside wall of the main tube and mount a MAD or an accelerometer there.

P'rfesser
 

tbzep

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Before I start, I want to post some of an email that I sent to Tim van Milligan yesterday:

I want to state publicly how pleased -- no, *thrilled* -- I am with the Saturn V kit. The level of detail is outstanding, the fit of parts is beautiful, and (my opinion) it isn't really as hard to build as some might think, thanks to a highly detailed and very clear set of video instructions. It's my sincere hope that the folk on RMR, reading about my experiences with the Saturn V, will decide to purchase one of their own.

In the latest newsletter, you used the word "vaporware". That word does not belong in the same sentence with "Apogee Rockets" unless the word "not" is also included. Way back when, I wrote a check for the Saturns and dropped it in the mail without a qualm. I knew you'd come through, I love the Saturn V, and I'm looking forward to Apogee's Saturn IB!
----------
Now to the LEM transition: Remember, YMMV.

The LEM transition is stated in the video as being a bit flexible. Since the big transition was more flexible than I like, I did what I thought I should have done with the big 'un. I was wrong; this didn't work too well, but I'll tell you what happened anyway.

Two photocopies of the LEM transition were run onto coverstock. They're not exact size -- photocopies rarely are -- but they'll do for this purpose. The inside curve on each was cut 2-3 mm *inside* the line. The outside curve was cut about 4mm inside the line on Copy A, about 8 mm short on Copy B. Objective: to have the two additional transitions nest neatly inside the one supplied.

The Original transition and Copy A were was cut out and curled lightly. Copy A was used in place of the "Overlap" piece of Original. A little rubber cement on the outside of Copy A, a little on the inside ends of Original. It's a little hard to get the ends of Original together but eventually it works.

[Incidentally, the idea of using rubber cement for the transitions is a great one, which never occurred to me. I'll be using that one in the future. Thanks Tim!]

The ends of Copy A are trimmed up a little with scissors. They don't have to fit together perfectly, in fact, I left a few mm gap between the ends.

For Copy B I cut off the Overlap piece and rubber-cement the thing together, just like Original was. The object is to get Copy B to fit smoothly inside the assembly we're working on.

A small batch of 30-min epoxy was mixed and brushed onto the inside of Copy A, then the outside of Copy B was coated. Excess was scraped off (Note to myself: need slower epoxy for this. Thinner epoxy would be nice too. I'm all out of System 3). Copy B was inserted into Copy A which was already in Original. Push the assembly together tightly.

When the epoxy has partially set, slide the whole assembly over the service module tube and onto its coupler. Fasten it in place as directed on the instructions. Wick CA onto the outside as per the instructions.

Problem: either I didn't push Copy B tightly enough inside, or I didn't fit Copy A properly. In either event, there appears to be a little separation between the shrouds in some areas. It's a lot stiffer now in most places, but it probably would have been better to have used Tim's method of an extra ring, or to use the carbon fiber or fiberglass inside the shroud. Oh well...

I should mention that I've done this sort of thing before, making several paper shrouds and gluing them together for a strong composite structure. You can make some pretty big shrouds using a pair of trammel points and a long aluminum rod to draw the curves.

P'rfesser
 

tbzep

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YMMV and all the standard disclaimers.

Well... [shuffles feet nervously] I guess I don't always do everything in the order it's supposed ta be in... [hangs head shamefacedly]...the fin fairings was supposed to be done long ago...

The balsa supports for the fin fairings went together okay, except that the die-cut slot in the balsa was too small for the piece that fits it. My fault, I should have clamped it, just like TVM showed in the video.

Widened the slots with a small flat file, just took a few strokes.

The vacuum-form fairings are a fair bit harder to work with than I thought they would be. They're *awfully* thin in places, especially near the bottom where they meet the tube. Be careful. They can tear more easily than some of the other vacuum-form parts.

The edges of the fairings are not straight lines. I tried laying down a ruler to cut them before I realized this. Cut them out with cuticle scissors as TVM recommends.

[Incidentally, this is one of many places where the video instructions are clearly superior to any printed instructions. Cutting out and fitting of the fairings would have taken a bunch of drawings and a lot
of words, and still wouldn't have been as clear.]

Numbering the fairings and their locations where they fit best as you fit them may be useful, if you're like me and can't quite cut out any two of them alike.

TVM uses a technique with Fixit epoxy clay to fasten the fairings to their supports. He also mentions the use of Fixit to stiffen the fairings so they won't deflect. Stiffening the fairings sounded like a great idea. What I did arises from the fact that I use a fair bit of epoxy in my work. And also from the fact that no epoxy clay was handy. I didn't order it yet. I'm sorry. So...

A portion of regular hobby 30 minute epoxy, about 5 mL or a bit more, was prepared. A little bit was rubbed into the balsa where it meets the fairing, to avoid "starving the joint." To the rest of the epoxy, quartz microballoons were added, enough to give the epoxy a good bit of body (a little more than the volume of epoxy). The result I wanted was about as thick as stiff pancake batter or brownie batter. It could be stirred, it would flow slowly, but would stay in place very well when spread thin. [Caution: the microballoons seemed to make the epoxy cure more quickly.]

The inside of the fairing was scrubbed gently but thoroughly with alcohol and allowed to dry completely. The epoxy mixture was spread over the inside surface of the fairing (a wide piece of scrap balsa used as a scraper), keeping clear of the fin slot. The fairing was then laid into place. Alcohol was kept handy and used to wipe off the excess epoxy around the edges and in other places where it ain't spozed to be. It's very important to wipe off the excess epoxy as much as is practical where the fairing joins the airframe. That will
be very difficult to sand off later!

After about half an hour or so, the epoxy was fairly stiff but not fully cured. Using the end grain of a strip of scrap balsa (doesn't seem to stick as badly as other "tools") the sides of the fairing were pressed into place. The epoxy is stiff enough now, that the plastic stays where it is pressed. Alcohol to remove the excess.

The finished product was both rigid and light. In some trials I had discovered that the vacuum-form plastic could be peeled away from cured epoxy -- but not easily. So I have no fears about the fairing vacuum-form coming loose.

Dang, I'm runnin outa parts in the box!

P'rfesser
 

tbzep

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YMMV and all the standard disclaimers:

Once again, the video instructions demonstrate their value. Had TVM not shown the specific technique for cutting out the vacuum-form wraps at the antennas and such places, I'd have made a dog's lunch of the job.

Not much to tell here. The epoxy-microballoons mixture used on the first-stage fairings was also used for the tunnel covers.

Special care should be taken to smooth out the epoxy on the smaller tunnel cover, and to remove excess before it's cured. That thing is awfully difficult to hold in the fingers while sanding (for that matter, the larger tunnel cover isn't too easy to hold either). I tried a Post-It note, stuck to the other side of the small tunnel
cover. Held Post-It between thumb and finger, with other fingers on the back of the Post-it, and not a whole lot of pressure. It held reasonably well while sanding. If someone has a better idea for holding little parts, please holler.

One minor addition on the tunnel covers: I used a flat file to recess the parts of the cover that fit over the 3rd stage wraps, just a tenth-millimeter or so. I also sanded the wraps a bit where the tunnel covers go, to remove the slight ridge at the edge. The tunnel covers now fit tight against both the wrap and the airframe. I guess that's a little anal...

P'rfesser
 

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YMMV and all the standard disclaimers.

The command module went together just as TVM showed. Those RCS nozzles are TINY. A hemostat (careful, not too much pressure) helped to push the nozzles into their slots. One more place where the video instructions were invaluable. Without them I'd probably have cut off parts of the nozzles during removal from the sprue...

The escape tower can be glued in place on the CM, or simply mounted then removed for flight. I opted for glue.

Minor change: I glued the tower assembly onto the CM first, *then* added the escape rocket tube and its nose cone. Reason: I didn't get the ends of the tower cut perfectly square and even, so the tower wasn't perfectly vertical on the CM. That slight angle would have been magnified by the escape rocket. So after gluing on the tower and fitting the ER, I tilted the ER a little to make it vertical, then added CA to glue it in place.

For transport, pull out the LEM adapter and store the Apollo capsule inside the 3rd stage.

If I get another Saturn V and do it as a Skylab, the Apollo capsule and the SM tubing should make a pretty nice Little Joe II.

Nothing much left but paint, now.

Miscellany:
A piece of thick polyethylene sheet placed strategically over a seam will allow parts that have CA glue on them to be held down with the thumbs, whilst keeping the thumbs from becoming part of the rocket. (You guys what use CA all the time probably know this already, but this is the first time I've used CA on a rocket.)

The bottom cardboard disk of the nozzle assembly tended to bow inward significantly after painting. That made the nozzles angle in toward the center noticeably. Were I to do it over, I'd either (a) make four new gussets that fit the whole way across the disk, to hold it flat, or (b) saw and drill a whole new bottom disk out of 1/8" plywood, and sand about 1/16" length off the coupler ring before assembly, so the nozzle assembly wouldn't be too long.

A 38mm motor mount would have been a good idea. I'd like to see this fly on an H112J, just fer fun. How about a five-motor cluster, maybe E15's?

While on the subject of high power, I'd have cut another main centering ring for the motor mount, right smack dab in the middle of the other two. While removing the too-tight nozzle assembly (MY fault entirely for making it too tight), I squeezed the airframe a little too much in my hands, and gave it a very slight kink. If I'd put in another centering ring, it might not have happened. OTOH if I hadn't made the nozzle assembly too tight it wouldn't have happened either...

Pre-curling shrouds: if I just curl them in my hands I tend to crease them. Pull them over the rounded edge of a desk or board, they curve more smoothly.

I stand that baby on the desk and it almost touches the ceiling. I smile every time I look at it. She is beautiful.

P'rfesser
 

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