Re: [DML] Re: MONSTER GARAGE SUCKS!!!!!

[Ryan Wright <ryanpwright@xxxxxxxxx>]

[Moderator Note: While this episode of Monster Garage is of interest to the DML, the physics of hovercrafts is not.  Please take further hypothetical messages about what might have happened to another forum.  I will no longer approve messages in this argument.  - Mike Substelny, DML moderator of the week]


On 7/28/05, twinenginedmc12 <twinenginedmc12@xxxxxxxxxxxxxxxxx> wrote:
> The Delorean Hovercraft project could easily have succeeded, with
> either the "put the delorean panels on the hovercraft" or the "make
> the entire car float, frame and all" approach.  If you do the math to
> calculate how much pressure is needed for each method, you'll
> probably be a believer, but if you aren't at that point, nothing I
> say will convince you. You don't have to be a hovercraft expert to
> work it out.  They are relatively simple machines.
> The pressure needed to lift either configuration is well within the
> capacity of the engine used to generate, and well within the capacity
> of the skirt to endure.
> 
> But who cares?  It didn't succeed, and that's that.  

Why didn't it succeed, then? 

Hovercraft are only simple machines if you just want to lift something
a few cm. To make it move, and perform reasonably over a variety of
surfaces, it's not so simple. Anyone with further interest in how
"simple" this is can go through the following document:

http://www.hovercraft.org.uk/download/estimating%20thrust%20and%20lift%20performance%20Rev%20D.pdf

> Your comment that you could have told me it wouldn't have succeeded
> in the first 30 seconds is unnecessarily insulting to a number of
> people, as well as technically unfounded.  I'm sorry, but you are
> just plain wrong

If you're going to say I'm wrong, you should back it up. Explain to me
exactly how you could have succeeded given what you had to work with.
Run the calculations, here, for everyone to see. They are linked above
and can also be found all over the web or in the book "Hovercrafting
as a Hobby" by James Perozzo. I would do it for you, but the show did
not provide enough data on your design. However, I am sure you will
find that this project was doomed from the beginning.

Lifting a 2700lb DeLorean with a little snowmobile engine is
technically possible. On a solid surface (such as concrete), and with
a proper skirt, it could be done fairly easily. Using said engine to
also provide thrust and maneuverability, and fly around over various
terrain? Not going to happen.

I am building a 20 foot Sevtec Explorer hovercraft. Proper lift &
thrust requires 80hp. Craft weight is ~1200lbs with a ~1400lb payload.
Achieving that payload is possible due to several factors: The
operating size of the craft: 20 feet long, 10 feet wide; The low
weight of the craft itself; Lift fan placement & design (2x15" fans),
etc. Some have overbuilt these craft into the 2000lb+ range; they
perform poorly and have trouble planing out in water.

The DeLorean Monster Garage project tried to lift 2700+lbs (roughly
the same lifting weight as a fully loaded Sevtec Explorer). Except, it
had a lifting surface area less than half the size; a motor ~1/4 the
size; less than half the airflow on lift fans and a skirt designed for
a little bitty hovercraft. Of course it didn't work! And if it had,
you would have been isolated to solid surfaces only. It would have
never moved over anything else and would have sunk like a rock in
water.

I'm sorry if you find my comments insulting, however, they are true.
The second they showed the doner hovercraft on the show, I knew the
project was doomed. My wife said, "They're going to lift a DeLorean
with parts from that?" I laughed and responded, "Nope." And I was
right. Not because the people involved in the project "screwed up",
but because of what you had to work with.

-Ryan




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