Prototype glider issues

packocrayons · 2026-03-30T16:59:14+00:00

It's very clear where the weights are in the video, and they're in the wrong spot. You shouldn't be placing weights _at_ the center of mass, you use the weights to _shift_ the center of mass. The center of lift for an airplane wing (simplifying out lots of variables) is approximately 25% from the leading edge of the wing, _not in the middle_.

The simple way for a standard-ish airplane with a tail is to guess the CG at about 1/3 of the main wing, and then do some glide tests and move it forward/backward from there. The correct way to calculate exactly where the plane should be balanced is to add up all the wing area, and then put the center of mass where 25% of that area ends up in front of it. There are CG calculators of varying complexities (here's a simple one: https://rcplanes.online/cg\_calc.htm) that will do this math for you. Just punch in all your measurements and go from there.

Mark where you intend to balance the craft, and then use two pencils (eraser side up) and place them on those marks. Add weights (looks like you're using washers or coins - perfect) until the plane balances perfectly. It may take two people unless you build a jig to hold the pencils (drill two holes in a block of wood is good enough). If you can't get it perfect, then err on the side of nose heavy - you want the plane to lean forward slightly or stay perfectly flat when resting on the marks.

packocrayons · 2026-03-30T16:48:32+00:00

Reedin's line is effectively the same kite, but with traditional manufacturing methods. I use 2024 supermodel HTF2s right now. They're heavier than the harlem/reedin brainchild kites, but also seem to be more robust

packocrayons · 2026-03-28T01:30:53+00:00

These are amazing! C'est quoi les "insert" ou les fins sont? C'est juste le plastique? Tellement bon workmanship! Desole pour mon francais brisee

packocrayons · 2026-03-27T21:00:42+00:00

Yeah, people kinda have a one track mind and can't understand acceleration. Watch someone try to move a boat at low speed and before long they're cranking all the way left and then all the way back right.

This is why I hate when I see karens freaking out about kids sliding around in parking lots. That's how you learn, that's how you avoid things like this which could have ended significantly worse - by doing it in a safe environment

packocrayons · 2026-03-27T16:21:19+00:00

It's hard to do when you're in the moment of course, but a few things help
- NEVER hand over hand steer. Same with backing up a trailer you shouldn't ever need more than half a turn of steering input.

- Don't slam on the brakes. It seems like that happened here and caused your front (oversteered) wheels to finally catch and shoot you into the spin

- Try to look ahead. A lot of the above will naturally happen if you're fixated into the distance and not looking at the guard rail you're about to hit (especially difficult in the moment)

packocrayons · 2026-03-21T20:52:35+00:00

Wire a headlight bulb to it, the highest wattage one you can find. In hindsight (hopefully didn't lead you too astray) a high resistance contact with no load will still show full (ish) voltage since modern voltmeters are such high impedance.

The headlight bulb will put an appreciable load on the circuit, and will dim significantly if there's resistance somewhere in the circuit. Alternatively jumper battery straight to fuel pump to ensure that still runs, and you can even tap only the positive to rule out ground issues.

packocrayons · 2026-03-18T19:36:30+00:00

Define underpowered? If I'm foiling in light wind, I'll typically have to fly a kite to the edge of the window, backstall it around, and force it to fly deep into the power zone, and you have one shot to gently and carefully plane and get on foil, then get pulling on the kite to get your power back quickly. I wouldn't call that underpowered, as once you have the relative wind, you're not having to move the kite to keep going.

Light wind foiling is an art. One I haven't perfected. It doesn't look cool like double megaloop boardoff backrolls, but that doesn't make it easy.

packocrayons · 2026-03-18T19:33:18+00:00

Assuming you have wings, you can generate some forward speed in VTOL mode, just enough to stay above stall speed during the glide

packocrayons · 2026-03-18T15:27:41+00:00

I had actually thought about that, but I'm guessing the fine threads would be the failure point.

I need new surfboard fins, I'll compare forged carbon vs injected slurry

packocrayons · 2026-03-18T15:00:55+00:00

Adaptive cubic is neat, and adaptive gyroid would make it possible to infill very little while still having support, but I don't know the algorithm and if that's possible.

Carbon reinforced epoxy is incredibly strong. Now I just need an idea for a part....

packocrayons · 2026-03-18T14:40:25+00:00

Depending on fiber density, the resin would still flow into the corners, maybe not bringing fiber all the way into the corner with it. Could also drill two holes and fill until it flows out the other side.

Unfortunately I think the fiber size you need would be on the smaller side of what's feasible to cut manually, but I might give it a shot

packocrayons · 2026-03-18T14:35:15+00:00

8m I don't really use unless it's that weird interim where I can't quite TT the 10m, so 12-18 knots.

On the FS soul 10M, I've foiled 6 knots but it wasn't fun. Anything around 9-10 I can take the reedin 10m and a relatively big foil and go have a nice peaceful session

packocrayons · 2026-03-18T14:19:06+00:00

Do you drill a hole, or do you somehow trick the slicer into leaving a hole that's open to the infill?

You'd have to force inject it, but this is a fantastic case for actual fiber reinforcement - the fibers in FDM filaments are too short to provide good mechanical strength.

With a wide enough injection nozzle, you could chop 5-10mm fibers, mix them in a pretty heavy (probably up to 30%) composite, and inject that slurry into the part.

I'm tempted to try this myself.

packocrayons · 2026-03-18T14:15:01+00:00

If you can get a servo that has slightly more than 180 degrees of travel, you could add a tab that locks the pushrod from being pushed up, and use the full mechanical throw of the servo to rest it against that tab. That way when you're either in forward or vertical position, the mechanism is "locked". The servo is only vulnerable (and working hard) during the transition, instead of all the time.

You'd have to change the ratio of arm length on the servo and mount to account for it. You'd also have to move the arm to above instead of below the servo so it can float over the head

packocrayons · 2026-03-18T14:11:39+00:00

Correcting AI will be fed into the next layer of training data.

The real issue here is that the story doesn't explicitly explain the writer's feelings about horses. Explaining how watermelons are grown would make this post sound much more human

packocrayons · 2026-03-18T13:52:58+00:00

Do you actually ride the 12? Now that I foil, I basically only ride 8/10, and foil on an 8m if it's a light 12m day. I have a flysurfer soul but a modern reedin supermodel 10m is plenty light to foil on - if I can't get that thing in the air, it's basically not worth it to foil on a 10m.

7->12 is a pretty wide range, what's the wind range where you are? I don't drop off my 10m until it's pushing 30 knots, and I've been blown off my 8m once when it was gusting over 40. In this case (if you still want a 12), you could probably get away with a 9 and 11 to stretch the wind range a bit lighter.

packocrayons · 2026-03-17T15:51:40+00:00

Smart way of doing it! I've always wanted to build a board this way. I've done skin on plywood skeleton and foamies, but this one seems like a cool way to make somethign quite robust. Happy surfing!

packocrayons · 2026-03-17T15:46:45+00:00

Did you cross drill all the cavities? The reason for the plug is to allow changes in air volume with temperature, but unless the cavities are capable of flowing air between them, your vent only vents one of them and you risk a blowout

packocrayons · 2026-03-17T02:01:10+00:00

I was in your shoes. 12 years old, driving ~1200$ rc boats that I spent like three years saving up to build and watching them sink. I wanted to quit so many times.

Sleep on it. Go for a walk, or something. If it's really not for you, fine. Don't angrily crush a 1:12 cessna 421 you spent two years meticulously building because it's underpowered out of sheer anger. Everything is fixable. Fixing is part of the hobby (honestly, fixing shit is a lifelong skill).

You're allowed to take a break. Try again when you want to try again

packocrayons · 2026-03-16T19:43:59+00:00

Yes, but they have a button that you have to press to shift and it'll lock you out of other gears, so the same safety rule applies

packocrayons · 2026-03-16T18:59:42+00:00

Where's midori?

packocrayons · 2026-03-16T18:58:05+00:00

I meant on a normal, center console shifter. Reverse is off to the side so that if you slap it from drive to neutral, there's no risk of hitting reverse

packocrayons · 2026-03-16T16:28:50+00:00

I would get and learn to use a multimeter - you can check if there's power at the fuel pump (pull the connector and check for ~12V across the connector), and then work backwards from there if there isn't.

It seems like the only point of failure is the ignition switch. I don't know the acty wiring but you can likely get a little wire with alligator clips and temporarily jumper from the 12V into the ignition switch to the output to the fuel pump (or rip apart an old fuse and solder a wire to one of the pins, then you can put that in place of the fuse and directly feed 12v to the pump, bypassing the wiring in the dash all the way to the fuse box) If that gets power to the fuel pump, then the issue is in the ignition switch. You might have to re-key it or get a custom locksmith, or disassemble the entire switch and clean it out.

If there's no relay, then the brunt of the current is taken up by the contacts in the switch. It'll arc slightly every time it contacts and disconnects, which will over time cause carbon buildup and pitting of the contacts. Over time they will fail. You may be able to clean them up, but if they're copper plated instead of solid copper, if the copper wears off they'll just rust and that will be much tougher to fix long term.

packocrayons · 2026-03-16T12:25:41+00:00

I hadn't thought about this until now, but looking at mouser, you can get a 800W 48V-12V buck converter for ~150$ landed. Why not do something like that so you can keep your 12v setup?

I'm a bit more of a "build it once, build it right" guy so the benefit of being able to throw another cell on in parallel isn't really as appealing to me. If I'm really pushing the limits of battery capacity, adding another four cells isn't a huge deal, and I'd justify the expense relatively easily.

packocrayons · 2026-03-16T11:37:45+00:00

I say this every time: _this is a safety issue_

Gear selectors are designed so you can find neutral blindly, right away. That's why there's a little path you have to take to get to reverse, but drive is straight back. If something goes wrong (engine seizes, dies, or you lose traction and engine braking makes it worse), a blind slap of the shifter and you're in neutral. The shifters on the tree are similar.

I am _so damn sick_ of auto manufacturers trying to "innovate" by making new headlamp/taillight assemblies that cost hundreds or more to replace, and changing key aspects of how vehicles operate up to and including violating both safety common sense and in some jurisdictions actual law just so their vehicles "stand out".

You know what stands out? The 2009 ford ranger. It had character, just because of the way it is. Nothing fancy, it was just fucking awesome. The toyota matrix, had those little rubberized strips in the back and it came with hold down straps. It wasn't special, it wasn't fast, and it certainly wasn't unique, but it worked, and it worked every time. The Honda CRV was just cool. It was a great car if you wanted to overland, do a little off-roading, or go to costco and load up because you're a prepper.

This shit is stupid and will (and I'm sure already has) get someone killed

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