My second Aerobee 150 Build & Finish Highlights

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Marc_G

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Hi folks,

At the end of 2011 I built a SEMROC Aerobee 150. It had a full build thread, here:

https://www.rocketryforum.com/showthread.php?30552-SEMROC-Aerobee-150-Build-Thread

I eventually lost it to winds aloft that dragged it over a heavily treed area. It had an 808 camera on it. I was very sad to lose it, but the worst part of it was that although I had a pretty solid bead on the direction and distance it went, I never found hide nor hair of it ever again. In the fall I canvased the area, looking all over the ground, through the leaves, and up in the branches. Though no part of the rocket would have been salvageable, I did hope to recover the memory card from the camera. Or, at least get some closure. Over a bunch of trips over the span of a year or two I found lots of other people's rockets, but never any trace of mine. Eventually, I gave up.

When I first heard of SEMROC closing up shop I quickly ordered a replacement. This rocket is a bit tough to clone in the absence of SEMROC since it uses BT58 tubing and cone. Not the most common stuff out there.

I finally got around to building it over the last week or two.

My goal in the build was to do a better job than I did the first time around. Specifically:
-In aero foiling the fins on the original, I made some of the edges too thin and fragile.
-The strakes (called shrouds in the kit) are supplied as rectangular cross section balsa pieces. We're supposed to round them into semi-elliptical shape. That's about 10 linear feet of shaping. I didn't do a great job of it.
-It was the first time I used pearl white paint. I didn't realize it wasn't opaque; some marking lines showed right through.

There were also a bunch of small finishing errors due to insufficient experience or care.

As I write this, the build is done, but there is still a lot of effort to be spent to make it look nice. This won't be a full build thread; I'll only cover areas of particular interest.
 
First the fins. To get them to the desired shape, I first needed to sand them down from root to the opposing edge.

I started by taping them along the root edge, covering the portion shown so that this part of the fin would not be sanded. I then rubbed the fin along a piece of sandpaper that had been glued to foamboard. Many light passes from (protected) root to tip, gradually thinning the fin. There is a center line along the fin outer edges drawn by placing the fin inside a template half the fin thickness. Angle of the pen matters; there was some variability in how close to center the lines were.

Aerobee150 004.jpg

Aerobee150 006.jpg

I did all of them before moving to the next step.

Learning from the last time I built this bird, I stopped before making them too thin.

Aerobee150 008.jpg

I created triangular masked areas on them, and again sanded tape-to-tip until the desired shape was revealed.

Aerobee150 009.jpg Aerobee150 010.jpg Aerobee150 011.jpg
Aerobee150 012.jpg
 
With the fins properly shaped and smoothed, with no tips or edges made too thin, it was time to harden them.

For projects like this my preference is to harden the fins with thin CA. This lets me later fill any grain or pores that remain without fear of messing up the shape of the fins when I sand down the excess filler. Due to the complex shape of the fins, papering is not an option.

One potential problem with CA-hardening fins is that the CA soaks in and can reduce the glue joint strength, since the CA prevents the wood glue I will use from soaking in. So, I pre-glue the fins with wood glue first:

Aerobee150 013.jpg

After the wood glue has soaked in and dried, I then use thin CA (from Hobby Lobby) dribbled on and rubbed over the surface with either a q-tip or other applicator. Today I had a foam brush handy, so I used it. Actually it didn't turn out great; the glue set up a bit faster than usual and I got some globby bits on the surface:

Aerobee150 015.jpg

Usually it's much soother, other than the grain of the wood. The foam brush made the CA curing accelerate quite a bit. In fact some white fumes came up off the brush.

Anyway, a light touch with a 220 grit sanding sponge and a 320 grit sanding block & free sandpaper smooths off the globs. The composite wood/CA is a lot more resistant to the sanding than the plain globby hard CA. In just a few minutes per fin, they are good to go.

Aerobee150 016.jpg
 
I marked the body tube, with two marks per fin to account for the fin thickness. A layer of wood glue went into the area where the fins and strakes will be. The motor mount is also shown.

View attachment 255551

I adjusted a home brew fin jig that I use for projects like this to accommodate the fin thickness. The second layer of glue went onto the fin, and the double glue joint initiated. I used a clamp (clamping the flat part of the beveled fin) to hold it in place while the glue set up.

View attachment 255552 View attachment 255553 View attachment 255555

Eventually all the fins were on.

EDIT: How odd. The pictures aren't showing up. I'm not sure why.
 
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Looks like a nice project, Marc.

I really like your tip to apply wood glue to the fins' root edges before applying thin CA. I just papered a set of fins for a rocket I'm building, and sealed the edges with thin CA. I didn't think about the root edge being sealed, too, and now I'm concerned that the wood glue won't grab along that edge. I tried sanding them to little effect. At this point, I might switch to epoxy.

Thanks for your threads - I always learn something!
 
Next up: the strakes, called shrouds:

The originals look like this:

Aerobee150 017.jpg

And they are supposed to be rounded over to be semi-elliptical. Tough stuff, but not impossible. Particularly after the glue dries holding the two parts together, making that glued section harder material than the rest. Doing it evenly is a challenge.

Having tried once, and not satisfied with the results, I chose a different way. I bought some poplar dowel of the right diameter (3/16"), cut 17" sections to match the length needed, and sanded off about 40% of it to be slightly more than a half -round piece. Doing the sanding evenly was no easy task, actually. I made some jigs and tried using a drum sander, and botched several lengths. Eventually I just did it free handed with my belt sander. There were some parts of unevenness, but those are easy to fill in after attaching to the body tube.

I also sanded points at the front and an angle at the back to make them fit as needed.

Aerobee150 027.jpg Aerobee150 028.jpg Aerobee150 029.jpg
 
Nice work so far Marc. Speaking of shaping the fins, when I started in on those thick buggers of the WAC Corporal, the first one was a learning experience and I did get the edges nice and thin. I was also very pleased with the shaping, but like you, I over did it a bit and had to add edges back on to one fin with Squadron putty. I think they turned out fine. It's flown and boy, does it fly nicely.

When I get around to starting my 150, again, like you, I think I'll leave just a bit more balsa on the edges.

For fun and reference, some shots of the one at the Air and Space Museum:






 
Thanks Foamy! Nice pictures!

I will return to this build this weekend. There has been a lot going on at work and at home that has distracted me, but this weekend if weather cooperates I plan to put primer on her so I can begin the next phase...
 
Nice work so far Marc. Speaking of shaping the fins, when I started in on those thick buggers of the WAC Corporal, the first one was a learning experience and I did get the edges nice and thin. I was also very pleased with the shaping, but like you, I over did it a bit and had to add edges back on to one fin with Squadron putty. I think they turned out fine. It's flown and boy, does it fly nicely.

When I get around to starting my 150, again, like you, I think I'll leave just a bit more balsa on the edges.

For fun and reference, some shots of the one at the Air and Space Museum:







Foamy, were these at the old NASM? I didn't see an Aerobee 150 on display at Udvar-Hazy.
 
Foamy, were these at the old NASM? I didn't see an Aerobee 150 on display at Udvar-Hazy.
Yes, the photos where taken at the A&S Museum in DC (I work near-by). Quite a few early rockets there. I haven't made it out to Udvar-Hazy, yet.
 
When I started this build, among the first things I did was use thin CA to seal and harden the nose cone. I polished it a bit with 320 grit sandpaper/sponges, then decided to try something I had seen in K'Tesh's "Make a nose cone look like plastic" thread.

I got a mega magic marker and painted the cone:

Aerobee150 030.jpg

After polish sanding it, some grain pores and various other pits were clearly visible:

Aerobee150 031.jpg

In a few places while polishing it down I actually started to wear through the CA coating; I over-did it. I re-applied CA and smoothed things out:

Aerobee150 034.jpg

Filler primer helps a lot... the bird was ready for it!

Aerobee150 033.jpg
 
I took some post-filler primer pictures, to emphasis the defects I'll be working to correct, but sadly my photography skills weren't enough to bring them out clearly...

The whole rocket looks good, in poor lighting and from a distance:

Aerobee150 035.jpg

The pits on the nose cones are easy to see with the eye; not so much with the camera in this shot:

Aerobee150 036.jpg

And other places there are little pits and voids and places where the fillets had bubbles.

Aerobee150 037.jpg
Aerobee150 038.jpg
Aerobee150 039.jpg

I'll be using 3M/Bondo spot & glazing putty on these, as well as the tube spirals. I apply it BEFORE sanding down the filler primer. Then, I can sand through most of the putty and into the filler primer, leaving behind just filled defects. At least, that's the plan.
 
I put the glazing putty on it this evening. Hopefully time for pics tomorrow. It all went on pretty neat until I started on the body tube spirals. Then it spiraled out of control. I tried to screed it on with a plastic card, but it got everywhere, and I resorted to rubbing it on with a (gloved) finger. Some of it got too thick... there's going to be a lot of red sanding dust in my future...
 
Here is what it looks like:

Aerobee150 041.jpg Aerobee150 042.jpg

Yeah, a right mess with way too much putty everywhere. On the bright side it should sand down nicely. I use a sanding sponge first, to strip off most of it, then careful sanding with probably 320 grit (maybe 220) until I start to bite into the gray primer.

It was my intention to start sanding tonight but other duties have taken precedence. This weekend will have to be soon enough!

Marc
 
This weekend I sanded down the red putty and made everything as smooth as possible. There were some issues around the join of the two body tubes, so I gave extra effort there. I then hit it with a second coat of filler primer. A few blemishes were still seen, so I used some Tamiya putty on them. It's waiting for final sanding before I hit it with Auto Air sealer primer.
 
I finally got around to sanding down the white putty and giving the remainder of the bird a final sanding with 400 grit paper. The picture with the banana is pre-sanding.

Aerobee150 047.jpg Aerobee150 048.jpg
Aerobee150 049.jpg Aerobee150 050.jpg

She is now ready for the Auto Air sealer white that is the first step in putting an acrylic finish on. After that will come an opaque white coat, then a coat of pearl white (which is translucent) to make it sparkly. Probably won't get to it until next weekend. I've also got another rocket, an Araphahoe C (downscale from E) coming along and may paint them concurrently.

Marc
 
That's a good look'n rocket and you doing a great job of making it look right.

Now I want one, where'd you buy it at?
 
OK, Aerobee 150 mark 2 sat for a couple weeks pending finishing, while I worked on an Arapahoe C.

Finally I got white primer on her:

Aerobee150 051.jpg

The primer used is Auto Air Sealer White. The trick to this primer (a water based airbrush paint) is not to try to put it on so heavy in an attempt to make it opaque. It's not meant to be an opaque paint; you only need a thin layer. It adheres well to the surface underneath, and opaque paints sprayed on top of the primer will stick well to the primer.

The picture above us under-lit but if you look carefully at the upper fin you can probably see stuff showing through, and in other places.

I then gave it a coat of Auto Air Opaque White. By "a coat" I mean I painted over it back and forth with my mini spraygun with relatively light flow, several passes over the whole rocket, over the course of 10 minutes or so. The result is an opaque white that hides anything underneath it.

I didn't bother taking a picture, bit it was a bit whiter than what was shown above.

Next, I removed the nose cone and put on a coat of Auto Air Pearlized White. This stuff is a bit too thick to spray comfortably with my spraygun, so I added a bit of Wicked transparent base (10%) and Auto Air reducer (medium drying) (10%). This overthinned the paint actually, and I got a few fish eye spots. One issue with airbrushing (or spraybrushing) is that sometimes you get these fish eyes. They can happen if the piece isn't clean, or if anything oily gets into the paint, or if you overthin paint then lay it on too heavy, like I did. Sigh.

Aerobee150 052.jpg Aerobee150 053.jpg

Now, all is not lost. In person, it's visible but not highly noticeable. I could paint over it with several thin dusty coats and get rid of it completely, but one of the fins is going to be covered in black anyway (or maybe red), and there will be other details to distract the eye. It's not worth making a big fuss over, and I've found that sometimes fixing these things causes worse problems.

Note, with airbrush acrylics, basically you don't sand them down. If this was a lacquer I'd let it dry well, and lightly sand then use a rubbing compound, then put another coat on. You can't really do that with acrylics because they don't dry hard enough to sand.

This will sit until at least Wednesday, which is when I may have time to mask it up.

Marc
 
I eventually got enough time to do accent paint on her.

I was having some trouble with my airbrushes, basically because I forgot I need to thin the very thick metallic paints I was using (Auto Air Sparklescent rock star red and a similar black (plus a blue, on another project)).

Eventually got the paint on, then goofed when removing masking and peeled off some of the top layer. Sigh.

Proper procedure is:
1. Mask with Tamiya or similar tape
2. Seal the edges of the tape with either clear base coat (for acrylics) or the same color as you are masking over. I used a drop of paint on a q-tip.
3. Allow seal paint to dry thoroughly
4. Paint the new color; allow to dry
5. Slice the tape edge with a razor blade before peeling the tape, so the tape doesn't peel off the adjacent top color with it! I forgot this step at first.
6. Profit.

So I had some touchup to do, which is hard with multi-layer sparkly paints. Nonetheless, it came out OK:

Aerobee150 054.jpg
Aerobee150 055.jpg
Aerobee150 056.jpg

A few rough edges along the white/red boundary, but no big deal.

The few decals went on easily; the circle of black at the top is auto pin striping.

Now I just need to clear coat it. I'm probably going to just use Future on this one.
 
The reason I use Tamiya tape is because I don't need to worry about bleed under—that tape is good. I try and get the masking off before the paint dries so as to avoid lifting the edges and the paint settles nicely without creating a ridge were the edge is. The annoying part of that is I have to figure out how to get the masking off before I put it on, to avoid getting the fresh paint on the dried paint.

Having said that, you know what you're about and to each their own. Nice build—as usual. Did you create that scheme or was it used on an actual rocket?

Like you, I've stopped fussing and fixing minor irregularities. If you have to have it in hand to notice it—I'm not going to worry about it any more. The thing will be dinged, scratched and scraped after the first few flights.
 
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The paint scheme was intended to match the way I had painted the original one some years back, though I made a modification to include a white stripe between the black and red parts of the black fin. Makes it look sportier to me, and frankly was easier to mask. I can't remember the face card paint scheme... I'm at work so can't go take a look very easily.

I find the Tamiya tape is great but I get better results if I seal it on all but the smoothest surfaces. I am still working on my technique in this regard.

Thanks for the kudos!
 
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