# The March 2011 issue of Westlawn Institute's free online journal is now posted

Discussion in 'Education' started by dgerr, Mar 19, 2011.

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### dgerrSenior Member

The March 2011 issue of Westlawn Institute's free online journal, The Masthead, is now posted and ready for you.

Highlights in this edition
Special Efficiency Issue:

• The Efficient Powerboat
• Message from the ABYC President
• Hybrids are not the Answer
• Westlawn Alumni/On the Drawing Board
• Know It All Answer - Schooner Rigging
• Splashes
• ABYC Tech Notes - LED Nav Light Refits
• We Get Mail
• Know It All Question - Prop Shaft Formula
• News & Views
• Controlling Corrosion - Part 2
• Unique Alumni Design
• Super Fuel Efficient Powerboats
• New USCG Passenger-Weight Rule
• Westlawn Information

Excerpts:

Editor's Note:
In this time of rising fuel prices and a tight economy, efficiency in boat design is critical. Owners need economical and cost-effective vessels. We'll spotlight efficiency in this issue, first looking at the overall considerations, in The Efficient Powerboat, by Dave Gerr, and then at details for enhanced efficiency in Patrick Bray's Super Efficient Long Range Motoryachts.

The Efficient Powerboat
By Dave Gerr
It gets better for slender hulls. The fact is that the rule of thumb "hull speed" is not accurate. Maximum hull speed is not a constant 1.34 times the square root of the waterline in feet. Instead, the constant 1.34 is a variable and that variable is proportional to DL ratio. The formula that I've developed that defines this relationship is:

Displacement-length ratio is a non-dimensional measure of how light a boat is for its length. The heavier a boat for its length the heavier its DL ratio and the lighter the boat the lower its DL Ratio . . .

Read the entire article in this issue.

By Dave Gerr
All ground vehicles (cars, trucks, buses, etc.) spend a significant portion of their time braking coasting, going downhill, or creeping along in bumper-to-bumper traffic. In all of these situations, the internal combustion engine needs to deliver little or no power, yet--in conventional vehicles--it must continue to run efficiently nevertheless. Hybrid electric cars take advantage of this by effectively shutting down or electronically nearly shutting down the internal combustion engine and using stored electric power during these specific periods. If you add in capturing regenerated power during braking and going down hill, the fuel savings are significant.

Super Fuel Efficient Long Range Motoryachts
By Patrick Bray
This hull design work started with a paper study on various published hull forms, their relative efficiencies and seaworthiness. Standard resistance curves for a wide variety of displacement, semi-displacement, and planing hulls were studied to establish their "sweet spots" and how this applied to the speed/length ratios that had been targeted. Out of this analysis came the decision to use a lobster boat type of hull, as it was considered to be the most efficient over this range of speed (VLWL x 0.9 to 2.3).

From here, various features were added to further enhance performance; a finer bow for low resistance and low bow wave, but high, wide spray knockers to add significant volume when pitching into a seaway; low transom immersion to reduce drag at low speeds, and wide spray chines above the waterline to give trim control at higher speeds.

Read the complete articles in this issue.
Go to:

You can click on:

To see all back issues and read whichever one you like.

Dave Gerr
Director, Westlawn Institute
www.westlawn.edu

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