COMPUTER PROCESSING ALLOWS A MAJOR ADVANCE IN PROPELLER MEASURING TECHNOLOGY
Professional Boatbuilder Magazine.

The time-honored way to determine propeller pitch is to measure the prop with a pitchometer-by hand, in the shop. With the low-cost computer technology now available, though, it seems only logical that someone would figure out how to computerize this time-consuming and somewhat imprecise process.

In fact, Australian inventor Terry Ryan has been at work since 1979 on that very problem.  His system, called Prop Scan®, comprises an IBM-compatible computer with an interface card, proprietary software, and ,a measuring assembly.  In just a few minutes, it can calculate-to an accuracy of .001'- the pitch of a propeller ranging in diameter from 3" to 16'

The basic principle of the Prop Scan® system is this: An operator inserts the prop into a chuck and mounts it onto a rotating table that has an optical measuring system in its base.  A small wheel at the end of a metal arm rides over the surface of the blade, measuring vertical distance.  Each pass of the wheel sends data to the interface card and system software, and a sophisticated reporting component produces an array of line and bar graphs that profile the face of the propeller blade.  Technicians must still shape the propeller by the traditional methods of hammering and grinding.  But, by comparing the pitch and camber profile of the existing prop to that of the designed prop, they can accomplish the job far more quickly and accurately than they could using a manual pitchometer and pitch blocks.

Ryan's company, Propeller Dynamics Pty.  Ltd, based in Southport, Australia, counts as its clients the navies of Australia, Canada, and the United States; and has also sold product to the private sector worldwide.  In this country, two shops have purchased the system: Black Dog Propellers (Solomons, Maryland); and Coastal Prop Technology Inc. (Fort Walton Beach, Florida).

Black Dog owner Larry Carlson was Ryan's first U.S. customer, and is unabashedly enthusiastic about the system.  "A competent propeller-repair technician using traditional measuring methods can bring a prop to within approximately 1/4" of the designed pitch," says Carlson.  "But with Prop Scan ®, we can remanufacture propellers to ISO standards.  It's been shown that upgrading from an ISO Class III ["wide tolerances"] to an ISO Class I ["high accuracy"] propeller increases fuel efficiency between 5% and 10%, so this change can make quite a difference in boat performance.  We charge approximately 20% more than the rest of the industry, but the results are so good that customers don't complain."

** This article partially excerpted from Professional BoatBuilder, issue Number 42. Article written by Mary Sullivan, Managing Editor.