# Thread: Which would be more efficient?

1. ## Which would be more efficient?

Which boat would be more efficient:

1) A boat that planes on the surface of the water.
2) or a "boat" that rides the ground effect a couple of feet above the water without touching the water, in a sense, flying.

Just thinking.

2. Of course the boat that rides above the water would be more efficient, less drag from the water. Tho hover craft has already been invented, but lots of disadvantages, been there done that. Bud

3. Mine as well talk about planes using ground effect, once it out of the water it is no longer a boat.
And yes, a plane using ground effect is more efficient than a boat. Lots of studies on this if you do some searching on the net.
Thats why those seagulls cruise just above the waves and rarely flap their wings.
BK

4. Actually a hovercraft isn't using the ground effect. And there is a whole class of ground effect boats. I'm not trying to re-invent anything. The information I cannot find is real efficiency data.

5. Less drag is more effecient however a hovercraft does not actually completly clear the water and is not flying on ground effect. Those boat things with wings that fly on ground effect are certainly more effecient than boats on plane as water has lots of drag.
Your question is a little vague as to what area of effeciency you are talikng about. Each of these three types of "boats" is better suited for certain jobs than the other two so what you mean by effecient would be helpful to know. What data are you looking for, load carrying per HP, amount of fuel per lb of cargo carried, hp per mph per lb? Total operational cost per mile per lb of cargo? What do you mean by more effecient?

If I had a small low wing seaplane and I mounted an outboard on it. Then I motored 100 miles, tossed the outboard into the bay and fired up the main engine and took off but remained in the ground effect for 100 miles in the same direction, same winds etc... and then pulled out of the ground effect, got up to nice cruising altitude and cruised for 100 miles. Which scenario would burn the least fuel? Let's assume the load and everything was identical for each leg. On the pilot forum I got this response from Float Pilot:

With my little 95 horse power Cub on floats, it takes most of that horsepower (and 2,600 rpm) to get up (on step).
Then you can reduce power to 2,000 rpm to plane along in a step taxi configuration. This keeps you planing along just below flying speed, (30 mph) with added lift via the wings.

However,, I can also become airborne in ground effect over the water. (float planes have more drag than wheeled aircraft in many instances so they do not receive the full ground effect benefit in some cases. ) Anyway,,, I can remain in ground effect flight at 1 to 2 feet above the water at 1,600 rpm at about 38-45mph

So with my aircraft I can use less power to remain in ground effect flight compared to step taxi.
I'm not proposing anything, just trying to learn.

7. The ground effect flight should be the most effecient if comparing on step speed to either method of flight. If you were using a very small effecient outboard at moderate speed say 3 to 4mph things could even out much closer. Drag increases rapidly in water as speed increases so on step speed would have a lot of drag. Flying in ground effect produces more lift at slower speed for less drag and less needed throttle.

8. Originally Posted by RainGull
Actually a hovercraft isn't using the ground effect. And there is a whole class of ground effect boats. I'm not trying to re-invent anything. The information I cannot find is real efficiency data.
The Russians invented several flying boats that "fly" only 8-10 feet above the waves using short, really thick, stubby wings, using jet engines these things cruise around 500 mph. But watch out for that one big one...it'd be the last, rather spectacular splash. Probably why they never went into production.

The big downside of your idea is that once you are airborne you'd be moving so fast that it would be challenging for you to do that which is so cool about being on the water: looking at everything and having a fun time.

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