Hovercraft Mk.4
My 4th hovercraft model proved was the first time that the capabilities of this idea started to get quite impressive.
Not only could the Mk.4 perform incredibly well on land, but it worked very well on water, and ice too,
traversing partially frozen lakes with ease.
Float.mp4Not only was it truly amphibious, but it was manoeuvrable as well.
The new addition of side "puff ports" that let out air from a pressurised hollowing inside the vehicle, called the "plenum chamber". These self-designed and hand-made valves produced a small thrust that created a small moment arm on the model, allowing it to do tight turns without moving.
Puff_Ports_Working.mp4Rudders.mp4Using a mixture of plywood and 3D printed ABS, I handmade a chain of pushrods which allowed for surprisingly good directional control in space contested environments.
In order to manufacture the curvature of the craft's hull, I had to make a completely new tool - a steam bender. This was quite simple to make, yet extremely effective.
Steaming.mp4Construction Process
The construction process of the Mk.4 was significantly quicker than all previous hovercraft models I had made as I was essentially using the dimensions from the previous one (the Mk.3), except improving on the design dramatically. This time I had used mostly balsa wood, reducing the weight down to less than half of the previous model. Additionally, I had more knowledge in electronics and what motors to use. The old terrible lift fan was replaced with a new brushless outrunner AC motor. These are widely used in electric aviation due to their low friction and exposed design, allowing for superb cooling. I also replaced the thrust fan with a more powerful motor and replaced the blades. There were still quite a few flaws, but the design was substantially better than the previous one.
Here are some photos of the design process.
Constructing the Bottom Floor
Constructing the Top Floor
Adding the Top Features
Adding the Ribs
Adding the Skin
A "cabin" style cover was added to protect the electronics from any water getting inside. I used neodymium magnets to fasten it to the hull.
Conclusion
Unfortunately, the Mk.4 met an quick and untimely end to its life when a friend crashed it at very high speed into a concrete blockade. This severely damaged the hull and ripped the skirt open. Not only this but the extreme heat had made the skin very flimsy as it was only attached to the wood via hot glue as I didn't have the tools at the time to clamp it down using wood glue. This construction method did not fare well in hot temperatures, especially the 2022 England heatwaves. All of this caused me rethink its design quite dramatically and make note of its various failings, so I could improve on them next time around, as I made this model quite fast in order to finish the whole project before my exams at the time. The hovercraft project was postponed for a while after this due those exams and other life events taking up time afterwards. I would, however, begin building another one a few years later.
Project Afterthoughts
I learned many lessons about this type of vehicle. The shortcomings of this design taught me:
Hovercraft can flip at high speeds and will need some type of aerodynamic device attachment to mitigate this.
Hovercraft can be hard to control to the inexperienced pilot, and so some kind of removable shock-absorber or bumper attachment would be wise next time around.
A hovercraft (which is supposed to be a rugged, all-weather, amphibious vehicle capable of traversing almost every terrain), should be immune to both extreme heat, and extreme cold. I will bare this in mind thoroughly when designing the next one.
When designing the next model, I had in mind to design it as a kind of demonstrator for new ideas and concepts.
Some things that I would want to include on the next model I design and build includes:
A properly, lift fan designed with air compression in mind, as well as preventing air back-flow when the skirt generates a high plenum-chamber pressure, which not an optimal situation for any axial-flow "compressor" fan to be in. If this is done, the skirt should be able to continually support the model over large "bumps" which might "knock" the air out of the plenum chamber by squeezing the skirt under the crafts' weight for a short period of time. A subsonic, centrifugal enclosed (with a roof) impeller design immediately comes to mind.
A hybrid, bag-finger skirt. This will increase the craft's ride height, allowing it to traverse more daunting, higher-obstacles. Not only this, but theoretically, if done right, finger skirts should be easier to maintain than a simple bag skirt. This has to be fully replaced if significantly damaged, whereas fingers only need to be removed and replaced individually. This reduces material demand and cost for me. Not only this, but fingers would also reduce the craft's friction as they provide a better seal with a fraction of the surface area needing to touch the ground to create said air seal.
A much better water sealed electronics box. A completely 3D printed, removable one would be revolutionary to this craft, allowing it to completely capsize and still be rescued without much significant damage, theoretically.
More powerful puff-ports. These would allow the craft to mauver on
Lights. This would allow the craft to be visible in low-light conditions.
A reverse-thrust mechanism. When teaching new, inexperienced people how to "fly" this model, they often would get it stuck and it would need to be recovered by hand. This could prove detrimental if it occurs whilst waterborne. Despite adding a lot of additional complexity, the reverse thrust mechanism could ultimately prove to save this model's life. Such a mechanism may seem overkill for just a model, until the pilot finds themself in an inescapable situation, so this is definitely something to consider.