The Hovercraft challenge was great! However, I was sure that the Long Brother's craft would be at a disadvantage for these reasons:

Being powered by only one engine, how could forward thrust be throttled down without losing the hover cushion? Did you guys keep the pedal to the metal and just steer? It also seemed that almost all the weight was on the back end and the driver did not sit at the front but in the middle. Why didn't the Craft tip backwards? (Is it because most of the downward air thrust was also at the back?)

In most cases, wouldn't air escaping from the high side of the skirt prevent tip-overs like the Scrap Daddy’s had? (Was their skirt too long?

-- El Kid (sizzl@mindspring.com), January 20, 2001

Answers

It doesn't take a lot of pressure to keep the hovercraft off the ground. Force = pressure * area. The area of the craft was about 8'x12'?? That would be 13824 square inches. If it weighed 300 lb, it would need pressure of f/a or 300/13824 or .02 psi.

I think the key is that you have to supply air to the skirt faster than it leaks out. Of course that is easier as the gap between the skirt and the ground will lessen when less air is supplied.

-- Michael (Canadian P. Eng.) (michael@mks-tech.com), January 20, 2001.

anyone catch what motor the Long Bros. craft had?

also, it seems that the winner borrowed a lot from a design from universal hovercraft's UH-10. The local building supply place has most of the parts. the brings up the question of what the cheap/common motor option might be.

then there's the skirt...

-- Mighty Mik (mightymik2@home.com), January 20, 2001.

I liked the single engine design too. As to the control, if you don't like the way it is moving, just let off the throttle, and "plop", then start over. I have never driven a hovercraft, but I can see that they drive a lot like an airboat on snow. My friends and I took an airboat to Illinois one year (1976 I think) after a blizzard. We got a write up in the local paper, as people were calling in about a UFO that they had seen. We had to tie it up whenever we parked it because it would tend to blow away. The motors that I noticed on the hovercraft were one Briggs twin 16HP, and one Kohler single cyl ten HP. Waddy, "Wreckspert" for the "Rusty J's"

-- Waddy Thompson (cthomp3851@aol.com), January 21, 2001.

the single flaw that destined the scrap daddys machine to an untimely demise was that the skirt wasnt tall enough...from what i could tell, it looked like the deck was maybe 8 or 10 inches(254mm)from the ground, this didnt allow for any roll,pitch or yaw without the deck coming periously close to the ground, or contact! which we saw!....the comercial units that are quite large have skirts in the range of 6-8 ft. tall! and can go over objects almost as high with out damage! as for speed control...slow the engine, and the craft sets down on the ground causing drag! then throttle back up when the desired position or proximity is achieved!"mashing" the throttle doenst work too well as these vehicle steer almost as good as a hockey puck! it was quite a good episode!

-- tim (milehiharley@hotmail.com), January 21, 2001.

I think the answer to your question El Kid is that the long Bros. machine would hover at just off idle. So backing off the throttle a little would only reduce their forward momentum & the extra drag from the skirt if they backed off more would slow them down nicely. I thought it was a great machine. The scrap daddies machine did not have enough lift to keep the skirt inflated enough so it would lose its hover in the turns & dig in to the sand. I think if they had just revved the motor a little more driving the hover fan it would have worked much better. They had it at a fast idle!!! Their machine look to heavy too for the fan they had though.

"Rick The Rocket" future Junkyard Wars contestant.:-)

-- Rick Lawrence (hoodoo2@povn.com), January 21, 2001.