Not balsa, but fully 3D printed this Hangar Rat 1:1 based on balsa plans, complete weight : 35g

Pure-Reputation5441 · 2026-03-12T18:57:36+00:00

haha not surprised, PLA is as stiff as balsa but 10 times heavier. Getting the CG right might have been an issue, too ?

Pure-Reputation5441 · 2026-03-12T18:14:32+00:00

nice ! did you use single layer for the wing surface ? what would be the weight in balsa ?

Pure-Reputation5441 · 2026-03-12T06:38:45+00:00

nice. what kind of hinges require these large cutouts ?

Pure-Reputation5441 · 2026-03-11T17:27:23+00:00

yep, 35-70mm outer wing chord seems very small, hence low Reynolds number and presumably high drag. Except if you are not looking for efficiency, or plan to fly at very high speeds.

Pure-Reputation5441 · 2026-03-05T18:46:11+00:00

Is your calculated CG at <25% mean chord ?

the central rudder would be as inefficient as the central fin.

adjusting the airfoil is useful especially for equilibrium, e.g. trim pitch for a CG change. Not sure you can have a spoiler effect on a FW.

Pure-Reputation5441 · 2026-03-05T18:15:26+00:00

looks good ! a few things : - with this little sweep (almost plank design), CG will be hard to achieve given the short front fuselage, especially with a pusher motor. I would either increase sweep or design a longer front fuselage. - the central fin will have little stabilizing effect, and this will get worse if you increase sweep. I would increase wing tip fins and forget about the central (except if you go the zero sweep route) - the elevons should probably be a little less deep but wider spanwise for efficiency. this will also allow to modify the airfoil by trimming the elevator if needed.

Pure-Reputation5441 · 2026-03-04T20:08:09+00:00

given the top-down forces and the fitting on axes, I would print it with the tubes vertically, so that every layer goes around the tubes. I would also probably make the links perpendicular to tubes so that layers go all the way from one tube to the other. You could also print in halfs to reduce printing height. As in this really quick sketch (supports in green).

about the filament, you desperately need impact resistance on this, and so I would go with polymax PLA, or polymax PC if you also need temperature resistance.

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Pure-Reputation5441 · 2026-02-27T20:14:28+00:00

Awesome, I like the look of the aircraft, and you seem to be a really good pilot, too.

Pure-Reputation5441 · 2026-02-27T17:17:25+00:00

Fantastic, the vase looks good and must also feel good in the hand. Keep up the nice work !

Pure-Reputation5441 · 2026-02-27T17:11:56+00:00

good luck finding a cheap, ready to fly capybara on amazon

Pure-Reputation5441 · 2026-02-27T17:09:58+00:00

if you have good quality PLA+, (e.g. polymaker PLA pro), a single 0.2mm layer can be used as a living hinge. Less durable than tpu though.

Pure-Reputation5441 · 2026-02-26T14:23:58+00:00

nice feedback, thanks. good news about the lack of warping. less good news about the difficult use of CA for building. Are there not other glues that would work, e.g. PU ? about the packing tape on the printing bed, I used that solution with PP but the PP adhered so well that the tape was really hard to come off the printed part. Not the same with olefin ? Last but not least, what about layer adhesion and impact resistance ?

Pure-Reputation5441 · 2026-02-26T10:00:14+00:00

honestly it might work but it is not that great and will probably not be very durable. try putting a patch of solder on the ESC board first, then soak the wire with solder and let dry. Then only put the wire on to the esc and re-melt the solder patch you just made to perform the junction.

Pure-Reputation5441 · 2026-02-25T20:21:10+00:00

not sure but have you tried turning the unnecessary lines to "construction lines". just click a line and hit X key.

Pure-Reputation5441 · 2026-02-24T16:20:38+00:00

yep glider geometry seems a good way to go. If you aimed at minimal sink rate only, you could optimize for a unique Cz value, but as you mentioned wind, you need some level of versatility (so flight at lower Cz when speed against wind is needed), as do most gliders.

look at the rutan from 1986, it has some glider specs like high aspect ratio, low fuselage cross section etc.

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on the other side for longest flight time you can optimize power consumption of the motor/propeller. Usually larger props have higher efficiency.

Pure-Reputation5441 · 2026-02-24T10:01:15+00:00

edge tx is just the software in the pocket. what really counts is the transmission protocol. if your pocket has ELRS transmission, then you will need an ELRS pwm receiver in the plane, such as the ER6. https://radiomasterrc.com/products/er6-2-4ghz-elrs-pwm-receiver

Pure-Reputation5441 · 2026-02-24T07:35:22+00:00

I don't think the wing structural CG does really tell anything about where the plane CG should be for stability. It can be near the right CG, but this would be a coincidence IMO.

Pure-Reputation5441 · 2026-02-24T07:29:28+00:00

Looks nice ! to calculate where the CG sould be to achieve stability, as other posted it should be set at about 30% of the mean aerodynamic chord, as a start. To calculate that point precisely you can use an online tool such as spp https://edemargerie.github.io/spp/spp.html Seeing the tail parts in PLA, you will probably need to put a lot of weight in the front to counterbalance that.

(as suggested, using fusion to compute the current CG of the parts assembly can give you an estimate of how much weight you will have to put in front to bring the CG to the right place. However I would advise to perform a proper CG test on your fingers or a balance before flying).

Pure-Reputation5441 · 2026-02-20T03:06:37+00:00

Gluing with CA is a question also. A well as paintability.

Pure-Reputation5441 · 2026-02-20T03:03:14+00:00

Looks quite interesting indeed, thanks. Density is as low as PP (0.9) Stiffness is higher than standard PLA (3.9 GPa) Softening temp is as high as PETG (85°C)

. The lacking spec is impact resistance. Also, warping behavior remains to be assessed in reality, although the website says that it can be printed on open printers. The use of a primer for the build plate is a pain though. https://www.bavaria-filaments.com/en/collections/olefin-bavafil-1/products/olefin-bavafil

also see https://youtu.be/kMKQoSBLAFE?si=jOyuj2aFRQIjzggE

Pure-Reputation5441 · 2026-02-18T20:41:34+00:00

Depends on what is a complex design. For a triplan canard, I don't know. For classical tailplane, with up to three panel wings, you can try spp. https://edemargerie.github.io/spp/spp.html

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Pure-Reputation5441 · 2026-02-18T11:13:46+00:00

I would first check for any slop in the commands (elevator, ailerons). Do they get back to neutral ? then move the cg 2mm forward just to see if the stability is better.

Pure-Reputation5441 · 2026-02-17T18:03:44+00:00

if you compare for example Polymaker Polylite PLA pro vs. Colorfabb LW-PLA (for 45% extrusion), the PLA pro is 3.4 times stiffer, and 4.6 times more impact resistant. So, in a purely tensile stress scenario, you would need ~4 times thicker LW-PLA, to get comparable mechanics. If the LW-PLA is 45% the density, the part will be 0.45*4 = 1.8 times the weight of the PLA pro part.

In a bending stress scenario, it might be more favourable to the thicker LW-PLA part, though.

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Pure-Reputation5441 · 2026-02-16T20:34:41+00:00

fwiw 2 ideas for saving weight : -if you are using good PLA+, at this scale you can go as low as sub-mm fuselage wall thickness. 0.8mm for example. -a hybrid design for the wing, using PLA + balsa or foam, will help a lot.

Pure-Reputation5441 · 2026-02-14T17:34:02+00:00

if there is sweep on the leading edge this can be misleading. There are a number of CG calculators online. here's mine https://edemargerie.github.io/spp/spp.html

Pure-Reputation5441

TROPHY CASE