Building the (scratch) Flat Boy (part 1)

Last month one day I went out for a walk and by the time I came back, I’d conceived and mostly designed in my head an odd-roc I wanted to build.

One of our club’s members, James Shattell, is working on his Level 3 rocket, a 10x upscale of the Estes Fat Boy. 24″ diameter Sonotube body, nose cone by Python Rocketry, great big plywood fins. His plan is to fly it at the August launch, our big Family Picnic day.

Our club launches always have a theme (observed to varying degrees): Gliders, helicopter recovery, scale models, and so on. We decided that for the August launch, in honor of James’s Level 3 attempt, we’d have a theme of Fat Boys. Standard, mini, micro, huge, fly ’em if you got ’em. Thing is, in the past several years the August launch theme has always been odd-rocs, a tradition not to be abandoned. So this August there will be two themes: Fat Boys and odd-rocs.

And on my walk the phrase “Flat Boy” came into my head and wouldn’t leave. After all, why build a model for one theme or the other when you can build one for both?

After considering some more complicated ideas I ended up deciding to keep it simple by bashing a Squirrel Works Pie in the Sky kit. The Pie is a flat disk with a motor tube in the middle, a drag stabilized odd-roc. It comes with a sticker to cover the top which makes it look like a pizza.

The Flat Boy is going to be basically a Pie in the Sky with some fins added, painted red (the disk) and blue (the fins), with Fat Boy-like decals. Simple but amusing… and hopefully it’ll fly okay. I modeled it in OpenRocket but I haven’t even asked it to try simulating a flight. It’s way outside OR’s aerodynamic model.

You get the general idea, but there’ll be decals too. I briefly considered seeing about getting custom decals from Sandman, but decided I couldn’t justify the cost it would involve, especially given that the kit cost $5. Instead I pulled a scan of the Fat Boy decals into a drawing application and drew up a design. The dark blue fin decals were no problem; I just had to draw up an L to go with the Estes F, A, and T (and flip the A to go on the other side of a fin) which I can print on clear decal paper. Which is why the Flat Boy has four fins instead of three.

The white “FLAT BOY” was another problem; I don’t have the technology to print white ink. Instead I drew up a red disk with the “FLAT BOY” on it. I plan to print that on adhesive label paper — figuring that would probably work out better for me than a big disk of white decal paper.

 

So much for the cart, but there’s still the horse. The kit went together pretty much as designed, to start with. I did mark the motor tube and the bottom of the disk for fins first. The thrust ring is glued into the motor tube, the launch lug is glued onto it, and then the assembly’s glued into the disk. It’d be all over except paint and sticker if I were building a pizza, but for the Flat Boy there’s more. I cut fins from ⅛” balsa — I don’t care much about drag or weight here; I do care about strength. Given that I was cutting from blank balsa I was able to fill the surface with thinned wood filler and sand it before doing the cutting.  Then I filled and sanded the non-root edges. Just a little rounding, more for appearance than aerodynamic efficiency. Actually all for appearance. I glued the fins on.Then some fillets, and assembly’s done. Stay tuned in a few months for painting and decals.