Technical Difficulties

I was trying to illustrate the next post on the N00b T00b last night, with a screenshot from OpenRocket, on the MacBook Air I use for The Rocketry Show podcast.

But the 3D image of designs in OpenRocket on this MacBook all display as really tiny.

This is as large as I can make the image.

Looking at it in preview, I guess in this case it's not terrible, but I wanted a larger image, and after an hour of messing with it, I got fed up and went to bed.

I might see if I can dig out the really old, slow, clunky laptop I used when I started The Rocket N00b blog, because at least I can load photos from my camera onto it, even if it's old junk.

We shall return to #NaRoBloMo shortly...

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Remnants

Today was a launch day in Amesbury, MA. While I had anticipated pretty clear skies and low wind, by the time I arrived (late), clouds had rolled in, and the wind was blowing toward the power lines. Not enough to halt the launch, but enough to disallow high power rocket flights.

The winds were slight enough to fly, but chilly, and made me a bit skittish. There were a lot of CATO's today, too, and the whole thing just felt a little spooky.

I had brought a number of rockets which had never flown, including the Estes Saturn V which I finished building before the July 20 anniversary of the Apollo 11 landing, but which I've been unable to get off the pad for one reason or another.

My first attempt was thwarted by the extreme heat. The launch was called short before I got the chance to get my Saturn on the pad.

The second time I took my Saturn to a launch, the shoulder of the upper section had grown tight. I was worried it wouldn't come off, that there would be no parachutes, and that the whole beautiful thing would come in ballistic and smash to pieces on the ground.

I took it home and worked on the shoulder until it could slide in and out of the rocket without too much force.

Last month, I was finally going to fly the Saturn, but as I was setting it up on the launch pad, the string holding the upper portion's recovery system broke. It was too short to re-tie it on the field, so I had to come home without flying it once again.

Today, after all that, the wind had me worried, and though I want to see how this rocket flies, I wasn't willing to launch it if I was likely to lose the upper section. "Go fever" has caused me to lose a number of rockets I worked really hard on, so I've learned to say no if the weather isn't feeling right.

So, I didn't fly much today - not the Saturn V, nor a number of other unflown builds.

I started with the N00b T00b, its second flight. The first flight, in October, should have been low risk. I only put it up on an A8-3! But I had a PerfectFlite Firefly altimeter on board, and the nose cone wasn't tight enough, so at apogee, the nose and altimeter both popped out of the rocket and I didn't see where they fell! I found the nose cone later, as it had landed right at the base of Pad 7, which I was assigned for my to-be-aborted Saturn flight. The altimeter never turned up, despite my combing the area. Good thing they're pretty inexpensive.

Today's N00b T00b flight went better. No altimeter, but a high flight on a B6-4, and the nose stayed on.

I also flew my Estes Photon Probe on a B6-4, a nice flight with a nice motor. I used to put C's or nothing in my rockets, but the last few years I've learned to really appreciate the B motor.

I'd have flown more B stuff, but I didn't bring anything that small, and realized I'd left my motor adapters at home. There were one or two things I'd have been willing to fly on a D12-5, but I didn't have a spacer, and the motor tubes were too long.

Finally, the weather cleared, and the wind died down a bit, and I though I should have a bit more guts. There was only 45 minutes left in the launch, so I didn't want to do anything too complicated (like attaching the metric rail I'd brought for some of my rockets to the high power pad), but I felt pretty good about putting up my Estes Leviathan on an F26-6 composite motor.

Because I built the Leviathan for my high power level 1 certification flight, I of course way overbuilt it. It's heavy and wouldn't go too high on an F26. That, and the Jolly Logic Chute Release, and the fact that the Leviathan is just... big... made me feel it was unlikely I'd lose it.

I think this was only the third flight of the Leviathan since I'd built it. Maybe fourth.

I taped a camera to its side and filmed the launch from the ground. The F26 is a fun motor. The flight was great. Chute Release performed perfectly. Of course my Rocketry Show MacBook Air doesn't recognize the little camera I had taped to the side of the rocket, but once I figure out how to get the video off of it, it should be a fun little short video.

After the site was broken down, I combed the area again, wondering if maybe I'd stumble across that Firefly altimeter I'd lost over a month ago. You never know. You can find all sorts of things at regular launch sites, even years later. Someone today found an Estes Mosquito they'd lost in early October, in perfect shape, so anything's possible.

I didn't find the altimeter, but I did come across the remnants of an old CATO. A damp, spongy blue propellant grain from a 38mm composite motor which must have been here since at least last month. Probably the nozzle blew out and the fuel grain fell out, unburned. It had sat there unnoticed, blending in with the ground, till I saw the unusual shape and kicked at it with my boot to reveal the blue grain.

There's one more launch this year, in two weeks. This time, I'll prepare better, ahead of time, go early, and see if I can't get that Saturn off the ground.

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The N00b T00b - A Quick, Easy, Scratch Built Tube Fin Rocket - Part 1: The Basic Build

I have a bunch of random model rocket parts lying around the Rocket Room. Some are things I intentionally stocked up on, and some are leftovers from kits I modified, or from other projects.

I have a bunch of short, BT-20 sized tubes (0.736 inch in diameter). They're most certainly supposed to be motor tubes, though they're a little short, so I'm not sure where they came from. Most Estes engine tubes are about the same length as an 18mm (A, B, or C) motor, while these are shorter. If you used them for a motor mount tube, you'd have to have the motor hang out the back by at least a half inch, whereas most Estes kits have the engine stick out about 1/4 to 3/8 inch.

I think they're leftover stuff from Rocket Camp which ended up in my pile of parts, and I think they might be from Pitsco, which a previous Rocket Camp teacher seems to have used.

I also had one 8.75 inch long BT-20 body tube which I know is a leftover from Rocket Camp. When you teach model rocketry to kids, there will always be parts left over. Not from the kits the kids build, but from the extra kits you have on hand.

Kids at camp will lose parts, glue parts in the wrong spot, shove parts up their noses or get them stuck firmly on their fingers and need them cut off by the nurse (yes, this all happened). Consequently, some of them won't have a rocket to complete if you don't have spare parts, and a kid at Rocket Camp with no rocket to build is likely to get bored and become disruptive. This is really a digression, but if you ever teach model rocket camp, make sure you have extra kits, and be prepared to end up with a bunch of random parts left over.

So, having given away launch lugs, engine blocks, fins, etc., I had one body tube left over from an Estes Viking.

I hadn't started building a rocket in a long time. The N00b family had recently moved, and for a while I was trying to just finish building and painting all the stuff I'd started in the previous two years. My build pile of kits is so big, I didn't know where to start.

Then I thought: maybe I should build a quick tube fin rocket, just to get back into it.

When it comes to model rockets, my tastes are pretty traditional. I like rockety-looking rockets - a nose cone, long body tube, and three or four fins. I'm not as interested in odd-rocs, saucers, boost gliders, or tube fin rockets. That's not a criticism - I enjoy seeing them fly at launches. It's just for my own fleet, I like mainly sport models and the occasional scale model.

But tube fin rockets can be fun. They have a lot of devotees. They can be simple to construct, and unlike rockets with flat fins, they apparently do not weathercock.

N00b Note: "Weathercocking" is when a rocket arcs into the wind. Almost all model rockets do this to some extent. It's a kind of side effect of fin stabilization. As a rocket's fins correct its trajectory in flight, lift on the fins rotates the rocket body around its Center of Gravity. As it oscillates, the rocket will tend to correct more in the direction the wind is coming from. Rockets with larger fins or rockets which lift off slowly tend to weathercock more severely than faster models, which may only weathercock slightly closer to apogee. See The Handbook of Model Rocketry by G. Harry Stine and Bill Stine for more on this phenomenon.

I had lots of parts, so building a tube fin model would be easy. Tube fin rockets can come in different designs, and I'm no expert on them, but it seems that the easiest to build quickly are rockets which use the same diameter tube for fins as it does for the main body tube. You can fit six tube fins perfectly around the center tube, so getting them glued on straight is easy.

As far as "designing" the tube fin rocket would go, there wouldn't be much design. I had parts, so I'd glue them together. I wasn't going to have to cut anything or shape anything. I'd just see how it turned out.

The rocket used a BT-20 body tube, the diameter used for 18mm A, B, and C motor mounts. So this would be what's called "minimum diameter." No centering rings, no engine hook, no motor mount - the body tube is the motor mount. Minimum diameter rockets tend to fly very high. Some examples beginners might know are the Estes Viking, Wizard, Hi-Flier, etc. The motor would be kept in the rocket though friction fit - a wrap of masking tape around the engine until it's tight enough that it won't fall out of the rocket, or be ejected out by the ejection charge.

Construction was simple. First, I glued in a spare engine block I found in my spare parts. I pushed it n place with an old motor casing so that the motor would hang out the back by about 1/4 inch.

Next, I glued on the fins. This is the part that makes a tube fin like this a snap. To get the fins on straight, you start with one fin. Run a thin bead of glue down one side of the tube fin and attach it to the main body tube. Then, lie both tubes on the work table, side by side.

A straightedge helped me make sure the ends of the tubes were even with one another, and the fact that both tubes were lying on a flat surface as the glue dried ensured that they were parallel - that the tube fin was straight.

As the first fin dried, I ran a bead of glue down a second tube fin and attached that to the body tube by laying it down next to the first tube fin.

A third tube fin was glued to the body tube laid on the table opposite the first fin.

I needed to figure out where to put the launch lug, since I'd never built one of these before. I tried to see if I could hide it in a gap on the body tube between two tube fins, but it turns out that BT-20 tube fins are a little too small to hold a 1/8 inch launch lug between them. So I glued a launch lug inside the fourth fin and glued that in place in the remaining gap on the body tube.

I made sure all the tube ends were even using my sanding block, and then I let the glue dry a little bit. The first four fins went on in about 10-15 minutes.

I flipped the rocket over when I felt the glue would hold without things moving, and quickly glued the remaining two fins in place in about 1 minute's time.

That was it. I popped on the nose cone, and had a look. With the exception of putting in a shock cord, the rocket was built.

Coming up: Stability? Payload? Paint? How about a name for this rocket??

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