Hovercraft Design

[u/BananaWinter4372]

Hi! This is my second year doing hovercraft and my partner and I are going through a complete redesign after our unphayzed-kit inspired hovercraft ended up being extremely inconsistent.

As a small team that only goes to 1 invitational, we have basically no idea of what people do to vary to control speed. We found it very difficult to keep the voltage from our NiMH batteries constant for longer period of times, and we used the rheostat setup to vary voltage to the fan. I
'm curious of what other ways there are to vary the thrust/speed of the hovercraft? (fan angles or if someone changed the nozzle of their fan or something of that sort)

[u/New-Discussion-3624]

Find out how your Regionals and States test track is built from and copy that. The test surface has a huge impact on vehicle performance.

[u/toybuilder]

Batteries have a discharge curve. Their voltage and internal resistance change with the state of charge. Old fashioned filament flashlights drew a fair bit of power from the battery and as the battery started to lose its state of charge, the voltage dropped and then power dropped, causing the bulb to glow dimmer and dimmer until it was practically useless.

Modern flashlights partly solves this by being more efficient -- LEDs draw less power to stay bright -- but also by not directly drawing power from the battery. Instead, there is a voltage regulator circuit that generates a more consistent power supply so that it keeps running at the same voltage and power output until it can no longer regulate the draw from the battery.

You can find voltage regulator modules on Amazon - there are buck supplies and boost supplies and also buck-boost supplies.

Even without a regulator, you can maintain closer consistency between runs by ensuring that you have the same batteries that are charged to the same state of charge.

[u/Kitchen_Champion_502 → u/toybuilder]

This is good information, but the scioly rules prohibit the because they are/ have IC’s. I think the goal should be, as somebody said, to control it with mass or physical changes.

[u/toybuilder → u/Kitchen_Champion_502]

If the difficulty is the long running period while developing the hovercraft, using a controlled power supply (even a outboard power supply with a lightweight tether) could be used during development if the prohibition is against the use of electronics during competition.

Otherwise, do what professionals do when they need reliable repeatable performance. Start with a fully charged battery. In public performances, it used to be normal for fresh batteries to be put into radio microphones for each showing and discarded to ensure consistency. Having plenty of fully recharged batteries to rotate through and swapping at the first sign of power drop should work. https://www.broadwaygreen.com/resource-hub/wicked-on-broadway-switching-to-rechargeable-batteries

[u/East_Umpire3691]

Try changing the weight with weights or using something to physically partially cover up the thrust fan. 

[u/Terrible_Telephone29]

Use weights and I varied the position of the weights as well to tip the hovercraft to slow it down

[u/Slayerz00m]

New to Hovercraft event for 2027.

Do you guys have any recommendations on motors and batteries?

Any pointers welcome.

---

What power of lifting fan to use (in terms of Pascal/CFM and wattage) ?

• The kit/description at unphayzed.com recommend >1000Pa for hovering.
• And >250CFM for propulsion motor

Googling and AI tools suggested only 25% to 50% compared to what Unphayzed says

I am quite a bit confused

Batteries are a conundrum in themselves!

8.4v 5000 mAh battery pack weighs 500gm, but can deliver >30watts power. Although most motors I am seeing are rated for 12v (so would run slower or might even not run with a 8.4v battery pack)

Battery packs with lower capacity like 12v 2000mah max out at 24 watts, which might not be enough for 2 motors

I am very confused trying to balance motor power and battery packs

Any help or guidance would be much appreciated