Staggered bottoms?

[jesseh]

What do the staggered bottoms do on powerboats? I've seen it on lots of different designs and would like to know more about what it does and why.

Did I mention that I'm not a boat designer? I'm a software engineer with a lot of curiosity.

The bottom of this boat has what I am talking about.
http://www.boatdesign.net/gallery/sh...t=2&thecat=514

Two types of steps:

The first (older) type of step simply aerates the hull.

The second type of step that is becoming more and more common now is the Harry Schoell Duo-Delta Conic hull which has one large pronunced "step" forward.

See:
http://www.schoellmarine.com/conic.htm

Duo Delta Conic High Speed Planing Hull
The DDC is a revolutionary new hull design that incorporates two hulls in one. The forward Delta Conic hull has a developed conical entry with a constant delta planing. It also incorporates wide lipped chines. The aft hull develops a constant planing surface that displaces a delta pattern when on plane. The forward hull creates a bow wave under the hull, along the aft hull to "ride the wave". As speed increases, the wave moves aft thereby lifting the stern. The hull then lifts to planing attitude without climbing over the "traditional hump".

At rest or on plane the trim attitude is nearly the same as during acceleration (no hump). The DDC has a high degree of lateral stability as a result of the forward chine notch. As planing speed is achieved air is vectored under the running section thereby reducing suction loads, as illustrated in the graph on this page, The forward and aft hull planes at optimum angles. The aft hull "surfs" on the bow wave at high speeds. This performance characteristic eliminates the need for trim tabs or wedges. Thus the DDC achieves higher speeds, greater efficiencies and stability, soft ride and effortless control.

http://www.schoellmarine.com/

[jesseh]

Thanks for the info!. That's how I had thought it had worked. Another question if I may on the same subject.

I used to be a neighber to a small hydroplane racer. On his boats there was a small strip fore of the prop that I was told caused the water to be "denser" just before the prop allowing it to bite better. I don't know how true this is, but he was a world record holder in the 500cc class with this boat.

If this is true the it seems the stepped design would negate some of the prop effeciency by airating (spelling?) or disturbing the water before it got to the props. Am I way off here?

Thanks
Jesse