Attaching the Wraps

Most of attaching the warps isn't so bad: it's fairly straightforward, following Tim's instructions, using thin CA and an applicator tip. But, it seems that if there's any radial stress (stress perpendicular to the surface) on the warp when the CA is applied, there's a chance the wrap will crack at that spot. Small crack, most likely, and no melting, but a crack. Cracks—tears, really—can also form from circumferential stress, along the surface, such as when you're trying to stretch the wrap to help it lay flat.

If I was pushing a piece down, the chances of a crack forming were pretty high.

So, the leading edges of the protrusions on the Second Stage Aft Skirt wrap (the LH2 Fill, fairings for the LH2 feed lines, LOX vent cover.) aren't secured yet. I'm debating whether to use some quick-set epoxy or thick CA. I'm leaning toward the epoxy, but the quickest set I have is five minute, and I want one minute. I expect I'll use the same to secure the various loose wrap ends, but I'll see just what happens after I attach the various tunnel covers.

I'm almost dreading applying the wrap covering the interstage between the S-II (second) and S-IVB (third) stages: it's a tapered wrap. Maybe Tim has a different method for attaching, or maybe I'll just go with the double-sided tape.

All Wrapped Up and No Place to Go—Yet

The wraps are in place: positioned, oriented, taped down.

It's time to apply the CA—in the morning.

The thrust structure wrap is a bit short, 1½, maybe 2mm. But, it looks like Tim designed things so a fin faring will completely cover the seam.

Practice, Practice, Practice

The Web abounds with stories of doom and gloom from people trying to attach the vacu-form wraps to the Apogee Saturn V. Rocketeers bemoan melted stringers, torn wraps, problems getting the CA to wick the way the instruction video describes—and on and on.

What to do?

Tim shows an alternative, using a particular double-sided tape. It's appealing: no risk of melting plastic. But, I remember the nerve-racking work attaching the paper wraps to the Estes Saturn V. Estes recommended using a permanent spray adhesive to attach the wraps, and I sweated proverbial bullets over getting those things lined up just right before attaching them. I'm not exactly thrilled with repeating that process using the Apogee vacu-formed wraps.

So, I thought I'd just try out the CA method, using some trimmings from the wraps and some other paper tubes. The procedure worked as advertised: the CA wicked, the wraps didn't melt, all seemed well. And the CA method has a big advantage: you can very, very carefully align and check and double-check the alignment of the wraps, tape them down, check again, and then apply the CA.

Trimming Plastic

To model Apollo 15, I have to remove the 4 ullage rockets from the Interstage wrap, and then patch the holes. Tim Van Milligan of Apogee Components recommended cutting patches from a second wrap; the question then became just how to get the patches to fit and to look good.

My first attempt: cut a patch that was too big, place the patch behind the wrap, and line up the stringers and other molded features. The slightly different plane is makes the patch too obvious, though. On to a second method: cut the patch so it fits perfectly inside the hole from the ullage rocket. This seems to be working, despite requiring much more precision and being much more tedious. It's now just a matter of being patient: start with the patch very close to the right size, but perhaps ever-so-slightly too big, and trim a thin sliver at a time until it fits, carefully ensuring the stringers stay aligned. With luck (shouldn't take too much), a tiny bit of filler and a coat of primer will complete the illusion.

The Joys of Tools

It sure is helpful to have good tools. It's even more important when you have someone who knows how to use those tools!

As yet another diversion in the Saturn V build, I'm working on an interesting two-stage rocket. More on some of the interesting bits later. For now...

The booster will be a D12, the sustainer will use an 18mm blackpowder motor. The booster's body tub is 35cm long, BT-80; the sustainer is BT-60. A transition between the two is needed, with a hole bored through to enable sustainer ignition. I have a 60-80 transition from BMS that just needs the hole.

How to bore the hole? I'd like the hole to be tapered, fairly smooth, dead center, and straight through. I don't have a drill press, a lathe, or a milling machine, and I'm certainly not trusting my hand drilling skills for this. (Yes, in fact, I only really need the two ends to be centered up, and the first, oh, couple of centimeters to be straight along the axis. Still, I'm not trusting this to my hand drilling!)

While checking with various friends, I ended up scheduling a business trip east that included a weekend swing by my parents' place for a visit. Dad has a small workbench drill press. He doesn't have quite the right size drill bits or mills, but he does have a couple of hole saws that are close. To make a long story a bit shorter, between the drill press, the hole saws, and the mill, along with Dad's skill at jury-rigging things and adapting tools and techniques to purpose, we have a hole that's nicely centered up, fairly well tapered, cleaned out of all the excess stuff in and around the edges (hole saws leave a plug in the middle of the work if you don't saw completely through—and the saw, though deep enough for our job, is only about 70% of the length of the transition), and ready for final fitting to the two motor mount tubes.

Pictures coming soon to the Nescorna Rocket Works Web site.

Good tools, good skills.

Cutting Wraps

Minor mistake: I chose the wrong sequence for cutting out the wraps. It should be obvious (shouldn't it?) that you start on the easy one, and work on progressively more difficult ones, not the other way around. Oops. I started on the hardest wrap.

Luckily, that wrap, the Interstage wrap, will likely end up as the fodder to patch the ullage rockets I'll remove from the other Interstage wrap, the one I actually did cut out last.

Would Be Done...

I'd be done cutting out the wraps except that...

I got the extra Interstage wrap, so I could patch over the removed ullage rockets. It makes sense to cut out the extra, use the better for the rocket and cut up the other. So, one more (complicated) wrap to cut, then ullage rocket patching, and then it'll be time to decide whether to try the CA technique for attaching the wraps or the tape technique.

Wraps, Wraps, and More Wraps—and a Launch

I talked with Tony Cooper at today's LUNAR launch; Tony has a built but not-yet painted Apogee Saturn V. He cautioned that many CAs dissolve the thin wraps. I told him about the online cautions about certain brands of paint being incompatible with the wraps.

Punch line: test the CA, test the paint.

As to the launch: 2400' overcast kept temps down, but skies gray. Fun launch nonetheless. I was able to get Alpha 3 to accept a motor (last month, it wouldn't go in), and the ~55th flight was a nice affair on an A8-5. Bertha flew twice, on a D12-5 and on a C6-5; the D flight landed on the runway, chipping and cracking a fin (certainly repairable). 4TNC flew twice, on a C6-5 each time: it's a fun little rocket, though I'm concerned about the tangling parachute shrouds.

Meantime, this afternoon, I've started cutting out the last of the main tube wraps.

I'd Like Paper, Please

Wow: these plastic wraps are a pain. Seemingly pretty fragile, difficult to figure out just where to cut, nerve-wracking while cutting. I remember the paper wraps from the Estes Saturn V: much easier to work with those, and I've not even begun attaching the wraps to the tubes.

Extra Wrap Arrived

Cutting is slow: perhaps this particular wrap came from a mold nearly at the end of its life, and so worn? Sometimes, it's hard to find the little scribe lines that are supposed to be convenient cutting guides. Regardless, the extra wrap's arrived, and once I get the wrap cut out I'll remove the S-II ullage rockets and cut replacement stringers from the second wrap.

Decision to Cut

S-IC retro rocket issues are now sorted out: they were installed on the inside of the S-IC engine fairings, and blew a piece of the fairing off when they fired. One decision down (doesn't have to be made!).

The S-II ullage rockets are a different story: model Apollo 15, for example, and they should come off (the S-II wrap has four of them, Apollo 15 had none). Tim had a suggestion: get a second S-II wrap, cut out the ullage rockets, and cut pieces from the second wrap to replace the stringers.

I'm ordering a second S-II wrap, and I'll cut-and-piece.

Sorting Ullage Rockets and Retro Rockets

Which craft do I model: Apollo 8, 9, 11, 13, or 15? Not so trivial a decision, if I really want to have a reasonably accurate model.

The S-IC stages had retro rockets. All of these missions used 8, except for Apollo 15, which used only 4.

Some of the S-II stages used ullage rockets: 4 on all of these except 15, none on 15.

If I model Apollo 15, how much will I need to muck with the wraps ("2nd Stage Aft Skirt and Interstage" wrap for the ullage rockets, "Thrust Structure" wrap for the retros)? Can I even make these mods, or is it 4 ullage rockets and 8 retros, period?

4TNC Flight Report

4TNC turned out pretty well!

A B4-2 had the right delay, but not quite enough thrust. The flight seemed to be, well, mushing (in the sense that an airplane can be mushing: descending on the back side of the power curve, not stalled, but not exactly flying well) for about 10m after clearing the launch rod.

A C6-5 produced a nice flight: good altitude, good speed off the launch rod.

A note on flying at Moffett: build those fins strong: that concrete's pretty hard!

4TNC

What do you do when you want to build a rocket quickly, for a tight launch deadline, and you don't have any kits available that fit the bill, and you want something just a little different?

How about a variant on the standby 3FNC and 4FNC designs: 4TNC, using tubes instead of fins? Yup, 4 Tubes and a Nose Cone. We'll see how she flies: RockSim predicts around 50m on a B4, 120m on a C6.

Out of Planned Hold

Out of the planned hold, for about a week now. Minor diversion to get a new rocket designed and built in time for this Saturday's LUNAR launch at Moffett Federal Airfield.

Despite the diversion, work continues on the Saturn V. The primary structure of the lower section of the rocket is completed. Along the way, I learned a nice technique for making tube couplers for arbitrary tubes (assuming you have enough extra from a spare tube): section a piece of the tube so it just fits inside "itself," retaining the tab that's extra, and use the tab as the bonding surface for the two pieces.

Filleting the forward centering ring of the motor mount proved a challenge: it's very far down in the body tube, and tough to reach. There's likely more glue on it than really needed, but I'd rather lost 10' of flight altitude and keep the rocket together.

Planned Hold

T minus who-knows-how-much and holding. We're in a planned hold, a construction hiatus due to other planned activities.

The shock cord is on the motor mount, though, and the aft motor mount centering ring is ready for installation. The after motor retainer has arrived (addition to kit); I'll install that as I install the after centering ring.

Beginning: Engine Mount

Preparing to celebrate, next summer, the 40th anniversary of Apollo 11's flight, I'm (finally) building the Apogee Saturn V (that I bought almost 10 years ago!). I'll maintain a builder's log here.

With the laying of the gussets on the motor mount centering ring, construction begins. Most interesting was constructing two perpendicular diameters on each ring: I'm glad I could remember some of my basic geometry (constructing a perpendicular bisector), and figure out enough of the rest from basic principles to be able to do it accurately. (Important observation: a perpendicular bisector of any chord will be a diameter.)

Along the way, I might let myself get slightly distracted to build another quickie model, since LUNAR will be able to fly at NASA Ames for a launch in August!