BAY PROPELLER INC.

Computerized Propeller Repair

I.S.O. Standards

Formal standards of measurement have been set by the International Standards Organization concerning marine propellers. The Hale M.R.I. Scan System classifies propellers according to I.S.O. 484-2 Standard.

The Hale M.R.I. can scan a propeller at up to 8 different radius, thereby detailing a propellers camber, rake, track and pitch in 3 dimensions with extreme accuracy. The M.R.I. also breaks down each radii into as many as 4 local pitch sections.

Here are a few definitions that will help you understand I.S.O. 484-2's tolerances.

Trailing Edge - The trailing edge is the part of the propeller that passes through the water last. If a propeller is cupped, then it is the trailing edge that is cupped.

Leading Edge - The leading edge is the part of the propeller that cuts through the water first as the propeller is rotating.It is the part of the blade nearest the boat

Radius - A blade section starting from a point on the trailing edge of the propeller blade to the leading edge of the propeller blade. The 50 % radius is the line 50 % of the distance from the center of the propeller to the outer tip of the propeller. The 90 % radius is the line 90% of the distance from the center of the propeller to the outer tip of the propeller. A standard scan with the M.R.I. could be at the 50%, 60%, 70%, 80% and 90% radius.

Local Pitch - The local pitch is the pitch in one portion of a radius. The M.R.I. can divide each radii into as many as four local pitch sections depending on the class the propeller is being repaired to.

Sectional Pitch (or Radii Pitch) - Sectional Pitch is the average pitch of a single radii on one blade.

Blade Pitch - The blade pitch is the average pitch of a single blade

Propeller Pitch - This the the average pitch of the propeller as a whole.

I.S.O. Standards

Class S propellers must measure within:

• 0.5% of Propeller Pitch
• 0.75% of Blade Pitch
• 1% of Sectional Pitch
• 1.5% of Local Pitch

Class 1 propellers must measure within:

• 0.75% of Propeller Pitch
• 1% of Blade Pitch
• 1.5% of Sectional Pitch
• 2% of Local Pitch

Class 2 propellers must measure within:

• 1% of Propeller Pitch
• 1.5% of Blade Pitch
• 2% of Sectional Pitch
• 3% of Local Pitch

Class 3 propellers must measure within:

• 3% of Propeller Pitch
• 4% of Blade Pitch
• 5% of Sectional Pitch

Each increasingly high level of accuracy provides improved performance, fuel efficiency and smoother operation.

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