Step placement

I'm looking for either books or publications (online or via subscription or back issues) which go into detail about step placement and design on performance powerboats from 25-40'. I see that almost all of todays production performance and sport boat lines employ steps of one type or another, mostly similar to one another, but I have been unable to locate much information about the design or calculations involved.

Ditto.
The only info I have ever found is in an old publication by Uffa Fox, where he espoused the great benefits of using steps in powerboats - and that was back in the 50's!

The late Bob Hobbs of Miami may have published on this topic.
Harry Schoell, www.pulsedrive.net knows about this stuff, but I doubt he's talking unless he gets paid.

What I can tell you is that you want the angle of incidence of your planing surfaces to be about 4 degres at your target speed.

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Stephen Ditmore
New York

You could take a look at the patent number 5452676 filed by Paul A. Fiore in 1994. This is a patent for a multiple steps.

Try www.cartesianinc.com but I think you hav to register to get any information here.

Best of luck.

Cato

You could also look for the patents of Harry Schoell and Michael Peters (at www.delphion.com) I favor this type - a single step forward of the CG for the purpose of achieving the 4 deg angle of trim mentioned before over the widest possible speed range. Schoell designs the Larson hulls, and is suing Regal for patent infringement. For high speeds it is important that no curvature is immersed forward, and Schoell's approach to achieving this is also an important part of his thinking.

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Stephen Ditmore
New York

I see that almost all of todays production performance and sport boat lines employ steps of one type or another

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As a counterpoint, there was a short article on Steve Stepp (of Velocity Powerboats - notched transom and pad vee bottom fame) in Powerboat Magazine. Stepp says he will never build a stepped bottom because

“They (stepped-bottom boats) are way more prone to spin out, let’s put it that way,” says Stepp, who has sold a lot of boats to Mercury Marine’s Lake X and to the company’s Placida, Fla., test facility. “There’s no such thing as a boat that won’t spin out—there’s none made. It’s just that vented or stepped bottoms are a lot more prone to it.

“We still outrun them,” he adds. “Pleasure boat to pleasure boat, equal to equal, in any engine combination.”

Stepp maintains that, in addition to greater efficiency and top speed, pad bottoms provide a handling advantage over conventional V-bottoms as well. Riding on the pad rather than a sharp keel makes Velocity boats more nimble, he says, which enables drivers to correct more quickly.

“With a pad bottom, you can correct fast if you see you’re going off a wave sideways,” Stepp says. “That’s a lot tougher with a conventional V-bottom.”

Click to expand...

http://www.powerboatmag.com/2001/july/features/feature11.html and at http://www.velocityboats.com/ Stepp cites several hooking, spinning, and rolling accidents which he credits to stepped ventilated hulls.

Providing a narrow flat water-ski-like pad for a boat to run on at top speed vs. aerating/ventilating the hull with steps running transverse to the boat’s axis would seem to allow for tighter handling, and if the speed improvement is equally as good… I don’t think padded vee’s have as good a hole shot though.

Have there been any reviews comparing the handling of a Harry Schoell step configuration to a typical two-smaller steps aft setup?

stepped hull

The data I've seen indicates that Harry Schoell's single step design is lower resistance
than comparable non stepped and at least one twin step design at most planing speeds. I
would note that the best results are obtained by combining a stepped hull with a surface
drive, which is what led Schoell to get into the surface drive business. I would also
note that Schoell's designs have incorporated a flat "pad" (or in some cases an inverted
V) aft of the step since about 1989. Whatever the merits of a pad, the ability of a
properly designed stepped hull to maintain optimum trim over a wide speed range is a
major advantage, in my opinion.

I think many control problems are due to the same factors whether the boat has a step or
not. A CG too far forward or too little chine beam relative to the boat's displacement or
a poorly shaped planing surface forward can result in curvature (along the path of flow)
being wetted. As for "spinning out," it may indicate that the step is too close to the CG,
but it should be correctable with a skeg aft in any case, just as it is on a surfboard.

Stephen Ditmore
New York

Another (free) place to search for and view relevant patents is http://www.surfip.gov.sg/

or US patents can be searched by keyword or number for free at http://www.uspto.gov/patft/
(to view the images you need a free TIFF viewer plugin for your browser... a good one is listed under the help section of that site if you can't view the TIFF's)