Canadian Yachting April 2016 - (Page 29)
for your Purpose
This article is the first of 2 parts. Part 1
deals with propellers for displacement
boats and Part 2 will cover the rest of
the drive train (i.e. coupling, shaft, stuffing box, stern tube and cutlass bearing)
and a comparison of fixed, folding and
feathering propellers for sailboats.
eciding to change the propeller
on your boat is not a binary
decision, like "Do I want a red
one or a blue one." The science of
propeller design dates back to
Archimedes (287-212 B.C.). Selecting
and fitting a boat propeller is often
referred to as a black art, because the terminolgy and mechanics of props seems as
much art as it is science. Don't let the
term fool you. Prop professionals have the
charts, formulae and algorithms to back
up their recommendations.
Selection of the proper prop for your
purpose is based on what you want or
need to achieve: greater fuel economy,
faster cruising speed, smoother operation
or faster on to a plane. In his sixth rule of
thumb, Dave Gerr states,
"The same propeller can't deliver both
high speed and maximum power ...
A propeller sized for high speed has a
small diameter and maximum pitch. A
propeller sized for power or thrust has a
Propeller Handbook: The Complete
Reference for Choosing, Installing, and
Understanding Boat Propellers
We are here to explore exactly what he
means by that.
PROPS - WHAT AND WHY
To de-mystify the black art you first have
to learn the language. I have purposely
left out the more basic terms.
Hub (or boss) - the centre section of the
propeller, necessary to hold the blades
Blade face and back - the face is the
side of the blade looking forward from the
stern, the back is the side of each blade
when you are looking aft.
Blade root and tip - the root is the part
of the blade closest to the propeller hub
and the tip is furthest.
Leading and trailing edges - The leading edge is the part of the blade that first
makes contact with the water as the propeller rotates. The trailing edge is the part
of the blade that makes contact with the
water last as the propeller rotates.
Rotation - props rotate to the right -
right hand (RH) or left - left hand (LH).
Right hand means the propeller turns
clockwise (to the right at the top) when
viewed from astern. The majority of single engine boats have right hand props.
Table of Contents for the Digital Edition of Canadian Yachting April 2016
Vantage Point: Careers in the marine industry
Waterfront: Ken Read’s Sailing Advice, CY in Miami and Dusseldorf
Club Profile: Cobourg Yacht Club
Destination: Swan Lake - This gentle cruise into Masset Inlet paints a stunning visual depiction of the Masset Sound scenery and a foray into a swimming hole near Swan Lake. By Linda Leitch
Feature: Perfect Prop for Your Purpose - In Part I of this 2 part article, learn about propellers for displacement boats. “Selection of the proper prop for your purpose is based on what you want or need to achieve.” By Rob MacLeod
Power Review: Beneteau GT 40
Destination: Georgian Bay Cruise - Spending five days on the breathtakingly beautiful Georgian Bay will have you starting your packing list and planning your own route for the summer of 2016. By Jennifer Harker
CPS Port Hole
Destination: British Virgin Islands - A weeklong visit to the Pro-Am Regatta at the Bitter End Yacht Club in the BVI’s challenges the author to find the perfect balance between the thrill of competition and the perfectly mixed cocktail in this idyllic setting. By Clarity Nicoll
Feature: Underwater Lighting - More affordable than you might think and more useful than you would imagine – Underwater Lighting is the hot upgrade for Canadian boats of all sizes, power or sail. Light up your cruising nights this summer. By Andy Adams
Crossing the Line: The Shark is Alive and Well
Canadian Yachting April 2016