# What should be the "golden ratio" for lifting on a land glider?

Following the comment suggestions, I changed the question from directly asking for real world examples to this.

Context:

In this setting, some decades after the 2020's, earth had some climatic disasters that led to the entire planet becoming some kind of steppe savanna full of big rocks and sand. Not post-apocalyptic, just cyberpunk-ish.

I'm trying to find a middle ground between a hover/glider aircraft/landcraft, and one of the ideas I took inspiration from are hydrofoils, that have a tiny foil that generates lift underwater, so you have massive ships moving meters above water all sustained by these tiny metal structures.

Of course, this would be impractical for landcraft with we moved the analogy with "1:1 scale" (like land-foils under the ground), but I was thinking on maybe a snow glider foil or a simple wheel. Thus, the "land-glider" (or "land-foil")...

Simply put, aircraft are just too expensive and complicated in general (since this is a story a few years on the future), gliders can't take too much weight and need enormous wings, hovercrafts need a lot of energy just to hover and cars are too slow to traverse rough terrain (also, Ekranoplanes can't fly over rough terrain and make turns).

The question:

So, for a land glider, it would be necessary to balance the lifting power necessary from wings/foils/lifting body fuselage (or any other kind of lifting mechanism) and the amount of weight the wheels must have on them to also give some speed, balance and not have to much friction so it wouldn't slow down the entire craft.

So, basically, a car with wings that doesn't fly that high (like a chicken).

What should be the "golden ratio" for lifting on a land glider?

Examples:

It would be easier to think on alternatives and answer my other questions if I had real world examples to base myself on.

Well, the closest I could find to what I mean are the 4X-D ski speeder from the Star Wars VII movie, but I don't know very well if these should be considered an aircraft or a landcraft.

The "closest" I could find on real life are Sand Gliders, that work like conventional sail boats, but with wheels.

• Ekranoplan? They work over land just fine, provided the land is flat. Commented Nov 10, 2022 at 16:01
• @AlexP The problem is that the land in this scenario isn't flat, and these can't make tight turns Commented Nov 10, 2022 at 16:07
• Well then, hovercrafts it must be. They are much less efficient than ekranoplans, but at least they can go over slightly bumpy terrain. If the terrain is neither flat (or at least very gently rolling) nor only very slightly bumpy, then, sorry, the vehicle must have wheels or tracks. (Note that hydrofoils have the same restriction -- they cannot deal with rough seas, like, at all.) Commented Nov 10, 2022 at 16:09
• I know it's very interesting -and important- to have good real-world references when making something near-futuristic, unfortunately you shouldn't ask about them here directly ^^'. But you can circumvent a bit this, asking for "landfoils" which would meet travel (e.g. speed, autonomy...) criterias and tech constraints in your world harsh's environment. Commented Nov 10, 2022 at 16:14
• @Fulano I think it's much less off-topic now :). I'd advise to copy the exact same question in title into the section "the question :". It's so that people don't need to look back up to understand what you want to know. For the rest, I fear that my knowledge of aerodynamics are a bit low, so I'll let the others tell you if you gave enough details, or if you ask for too much at once. Commented Nov 10, 2022 at 16:38

## Land based hydrofoils are called "Wheels"

Sorry if this answer is a bit disappointing, but wheels perform the exact function on land that hydrofoils perform on water. A traditional boat is not like a cart on water, it's more like a giant box you are dragging along the water, but we've been doing this for 1000s of years because water is slippery enough we can get away with it. A hydrofoil reduces drag on the boat by lifting it out of the water and only contacting it in small, low drag extensions, just like wheels.

In reality, there is little reason to try to make a vehicle like the one you are showing because the challenge when designing land vehicles is often more about how to add enough traction to the wheels the keep the car from slipping, and enough surface to keep it from sinking than it is about reducing drag. So, the ideal ratio is 0% lift, 100% weight on your wheels... actually, high speed land vehicles have to be designed to negate lift to ensure enough traction for breaking and maneuvering and to resist flipping.

### ...But nothing is stopping you from using jet engines for better speed

If good old spinning wheels are not fast enough for you, look at rocket cars. Again, instead of using lift to raise the vehicle off the ground, they actually use flaps that increase negative lift as you get up to speed to make sure that the air passing around you does not lift you up making you lose control.

That said, an objectively "good" land vehicle for your setting is actually something in the opposite direction of where you are coming from. Rocket cars require wide open, perfectly smooth landscapes that have to be specially picked from only a small handful of places in the world. Even if your whole world goes desert, there will not be many places you can drive them.

If you are trying to go off-road in a desert, you need bigger wheels and a lighter chassis so you don't spin out on loose sand. You need a lower center of gravity, wide wheel spacing, and a highly flexible suspension system to overcome sand dunes without flipping, and you need tight maneuvering more than speed so you don't crash against the bigger rocks. What you need for day-to-day driving around at high speeds is something like a dune buggy.

If you want to make a more believable high-speed dune buggy, reducing lift is not the way to do it. You need to be able to apply negative lift at will, using something like an adjustable spoiler. You could maybe even give it some optional rocket propulsion (like the bat mobile) for when it hits a wide open flatland where that might be a option, and loose sand would otherwise inhibit your max speed, but it will need to maintain a normal dune buggy like operating mode for most situations.

• Ah crash, the querent just changed the question by the time you wrote your answer. Sorry :/. Commented Nov 10, 2022 at 16:33
• @Tortliena he did.. but I think the point remains that wheels need a lot more work to add enough friction than they do in reducing it. Commented Nov 10, 2022 at 16:38
• Indeed ^^. Hmmm... I don't like very much frame-challenges (it now kinda is with the new question x) ), I'm not sure how you can give an alternative, perhaps use the wheels as the main source of "gliding", and keep somewhere the idea of some sail. Or talk about the "golden ratio" of wheels ^^". I truly don't know. Commented Nov 10, 2022 at 16:42
• @Tortliena Agreed, I've extended my answer accordingly... it's still a frame challenge, but addresses the lift/thrust ratio part of the question more directly. Commented Nov 10, 2022 at 16:46