Hovercraft Danger

What ever can happen will happen.
A unfortunate accident has ocured in New Zealand. A trial run of a hovercraft(possibly an on-line design) resulted in the death of the operator by a mechanical fault resulted in the blade to strike his head. The operator was at the front of the craft.
Pictures were shown but not necessarily the actual craft.

 

Just as I was getting over the severed hand thing.

 

we need a boat design csi forum.

 

Yep
First I had to avoid sex (unfortunately that plan is already well implemented ), now I have to stay away from hovercrafts....... whats next?

Stop walking the dog?

 

Guess some new safety rules should be introduced, like - don't handle a winch under tension if you're a nudist sailor...

 

It is very unusual to read of a serious hovercraft accident. This sort of surprises me, as there are obvious dangers. In fact hovercraft are the safest way to travel, which is weird considering the physics of controlling one.

In my own "dream design" the engine and fans are hidden and tucked well into the body/hull for safety and noise control. I have never posted this craft, but built a 54 inch long model of it (one inch equals one foot scale).

http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10742775

If the image above is of the doctor's craft, then it was a front fan, front engine design. I like to keep all the nasty moving bit behind me myself and well guarded.

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From the HCA forum:
http://hoverclub.invisionzone.com/forum/index.php?showtopic=1638&st=60

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Short Story:
A few years ago a hovercraft with a rear thrust propeller (front lift fan) stalled and was floating in the water before a group of us sitting at a picnic table on shore. Several of the operators friends came by and perched themselves on the rear of the craft to assist.

When I heard the electric start engage I hid under the picnic table, the others at the table started to ridicule me for reacting that way.

As I sat under the table I explained to them that there was water on the deck of that hovercraft from the weight of the three guys working on the engine, and that if the propeller blade hit the water while turning it could come off and hit one of us.

Just as the laughter over my comment died down the propeller exploded when it hit the water (just a few inches over the deck) and splashed down in the water about half way between our table and the hovercraft.

I came out from underneath the table with instant validation. One of the guys at our table said of the three guys on the hovercraft; they were lucky and could have been killed. I looked at him and said we are all lucky the blade did not travel another fifty feet towards us.

Some people do not see danger, or cause and effect even when it happens exactly as they were warned. They just do not get it, and will not admit when they are wrong.

I'm the sort of guy that while standing at a street corner waiting for the light to change will position myself behind a large traffic light pole or other object. I have seen cars have blow outs and come over the curb from numerous causes and have learned to be aware of my environment. I also look behind me once in a while, you have to be aware or suffer.

 

It's a bit disturbing that the articles about this incident are inconsistent and the photographs are misleading.

Neither of the two pictures shows a damaged blade, for example. I think there is a bit of hearsay involved with the reporting.

From the wording of the articles, I wonder if there was a duct at all, or if there was a severely deficient one that caused the fan failure. Usually the duct will dramatically reduce the energy of anything ejected, even if it can't stop it.

I've never had a blade or anything else go through the wall of a duct yet, but I've seen several cases where something did. Everything I saw go through was in the order of a tool or a rock or some other sturdy, heavy thing. That's generally not a fan/prop blade, they tend to be light and have a nice big surface area.

One thing that's happened to me before though is to have a tool "tee-ed up" and hit by the prop, to go shooting out the back.

Another thing that's happened to me is that water strike George is talking about. It destroyed the prop entirely. Worst thing was, it wasn't my hovercraft.

Fortunately enough the manufacturer of the hover-specific prop was present when I broke the thing, and gave me a deal on fixing it.

 

The image in my post is a hovercraft but not necessarily the one involved in the accident as I said. I did not want to show all of the hovercraft as that may have been mis-leading.
Would you take your craft into heavy surf?

 

A hovercraft forum would be interesting.

 

I'd have to have a powerful craft to take on the ones shown, and one large enough for the task.

On a very fair day, I once took my hovercraft to lake Michigan. There were surf waves, and one broke at my bow sending buckets full of water into my fan blade where they made a loud clashing sound.

No damage done, but I quickly learned to angle into the waves and not take them head-on.

 

@tom kane,

The one you show is not in strong surf. It looks like a "slider" brand machine. It might be problematic for a beginner but as in any small boat, its ability to take wave action depends largely on the driver.

IMO it doesn't take a lot of power to go on strong surf. It takes freeboard, and hopefully some cushion height, and a hull that handles the wave if it actually makes hard contact. And lift inlet(s) that tolerate or avoid "green" water, and fan blades that either tolerate it or a drive system that lets them stall without snapping. And a thrust system that somehow tolerates or avoids the water as well.

What might take power is going upwind or downwind. Hovercraft are very susceptible to wind compared to boats, and not much susceptible to currents compared to boats. But if you put it down in water, currents seem to be much more troublesome because a hovercraft hull is not designed to move through water.

Some hovercraft, particularly the single engine single duct variety that kach22i has, have difficulty handling wind. Different machines handle wind poorly in different ways. The Scat brand sold in the USA would tend to have big problems going downwind, because you're either going too fast or you have insufficient lift, or both. That all leads to a plow-in, which can eject the driver. Conversely, the Universal Hovercraft brand of kit that I have tends to have a whole lot of surface area in the back, causing it to weather-vane and not want to go downwind at all.

 

Thank`s for all of that info. I found that surf big or small was like a lot of small tidal waves which carried anything in it where ever it went, it was like being on a conveyor belt and nothing could fight with it. I am always aprehensive when I see boats,jet skis or any craft in surf. My neighbour nealy lost several of his family that way and one of his children was trapped under the quaterdeck.

I can breath a sigh of relief, they are back on shore.

 

I can definitely appreciate that.

I remember the first time driving a power boat in significant waves, I almost flipped it. I also remember the first time I encountered any wave action on a hovercraft. It was pretty much the same thing, because while some things are common between hovercraft and boats, they really aren't all that common.

Driving that same boat, my dad wouldn't reel in the fishing lines until the waves were twice as high as what I almost flipped in. After awhile, I got nearly as good at it.

Don't get me wrong, there are definitely qualities of both boats and hovercraft that cause them to be better or worse in waves. But no matter what, if you don't know how to drive it you could get in a whole lot of trouble before you even suspect it.