Spent three weekends on my printed swing-wing glider and today it finally worked. The first two flights the wings either stayed locked or snapped out right off the pad, which looked pretty silly. Turns out the problem was friction in the hinge. I printed the pivot pieces in PLA at 0.2mm layers and they were binding ever so slightly, enough that the spring band couldn't overcome it under the g-load at burnout. I sanded the hinge pins down with fine wet-or-dry paper and reamed the holes with a drill bit turned by hand, just a hair at a time untill everythign swung freely under its own weight. Also swapped the rubber band for a slightly stronger one. Test flights today: wing deployed maybe half a second after burnout both times, and the glide was actually glide-like instead of the lawn dart routine from before. One thing I noticed, the printed nose section is heavier than I planned, so the glide tends to pitch up near the end. Not a disaster, it just stalls and settles down gently. Might hollow it out a bit on the next print. Still, after weeks of watching it tumble into the grass, seeing it circle down under a full wingspan was a good feeling.
Finally got the wings to pop out on time
Oct 10, 2026
Last reply: 47 seconds ago
4 Replies
I fought the same sticking hinge problem on mine last fall and went a diffrent route with the fix. Instead of trying to sand printed pins into submission, I swapped in a short length of music wire through the printed hubs and reamed the holes just enough for a smooth slip fit. Ran a pencil point through the holes for dry lube too, since I was worried about anything oily soaking into the filament and weakening it. Took maybe twenty minutes and the wings now snap out the instant the motor burns out, even on the B6-4 flights where the kick is pretty mild.
On the nose weight issue, hollowing the print works but an easier trick for me was shifting the wing saddle back about a quarter inch and adding a tiny bit of clay to the tail until it glided flat with a gentle hand toss first. I got the balance point roughly right on the bench before wasting another motor on it, which I should have done from the start honestly.
One other thing that helped mine was giving the wing root edges a light sanding where they rub the fuselage when folded. They were dragging on the body tube edge during deployment and it made the swing look lazy even after the hinge was free.
On the pitch-up at the end of the glide, I had the same thing happen with a printed glider I built last summer and found a fix that didn't involve reprinting anything. I just stuck a few grams of modeling clay into the tail cavity and shifted it around between flights until the glide flattened out. Took maybe four or five tosses off the porch to find the spot where it stopped ballooning. Clay beats hollowing out the nose because you can tune it on the field instead of waiting another week for a print.
This is the first time I've seen someone make moving parts on a printed rocket actually work. I've only printed static stuff so far, fins and a coupler, and even those needed a lot of fiddling to fit right. How do you keep the wings folded while it's still going up? I keep picturing them popping open too early and the whole thing spinning off sideways. Also curious what you use for the band, is it just a regular rubber band from the hardware store or something stretchier? Might try a simple fixed-wing first before I attempt anything that hinges.
Update: the clay trick sorted the pitch-up. Started with a small ball of modeling clay in the tail cavity and moved it around between flights until the glide came out flat. Also swapped the printed hinge for a short piece of music wire with a hand-reamed fit, and the wings snap out even faster now. Next build gets a lighter nose from the start.
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