TBPNews #45 - September 8, 2003 
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>>>>>> Tunnel Boat Performance News >>>>>>>>>>>>>>
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In this issue: 
1) First Annual "Rock The Bay" Poker Run 
2) Dealers welcome Bombardier sale to family
3) Zodiac gets $5M Coast Guard order
4) Off throttle steering standard for PWC's
5) Brunswick continues on acquisition path
6) NEW - Mercury Outboard Trailer Hitch Cover
5) FREE Powerboat e-book
6) 'Family & Performance Boating' magazine - Save 25%!
7) FEATURE ARTICLE - How does a tunnel hull work? (Part 2) 
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1) First Annual "Rock The Bay" Poker Run 

Fastboats.info is proud to announce the First Annual "Rock The Bay" Poker Run and it's going to be a great one!

Fastboats.info has teamed up with the Nauti-Goose Saloon, the Nor'easter Magazine and Anchor Boats in the beautiful bayside town of North East, Md. to bring you this first-class, APRA Sanctioned and insured event on the Northern end of the Chesapeake Bay. 

Boasting the finest cruising waters on the Chesapeake Bay, the northern reaches of the Bay offer fresh water, protected surroundings, beautiful scenery and lots of open water for a great performance boating environment. Our headquarters, the Nauti-Goose Saloon and co-located Anchor Marina offer the most picturesque spot on the bay to host a Poker Run. There's plenty of free parking, fork lifts, multiple long ramps with docks perfectly suited for large performance boats with mechanical services and fuel available at the Anchor Marina.


http://www.rock-the-bay.com/
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2) Dealers welcome Bombardier sale to family

Bombardier Inc. has sold its recreational products division to a group of investors that includes the founding family.  The Montreal-based transportation giant said it reached an agreement to sell its recreational products business for an aggregate $874 million to a corporation formed by Bain Capital, members of the Bombardier family and the Caisse de depot et placement du Quebec. The transaction is expected to close by midfall.  This is the best possible outcome, said Roch Lambert, vice president and general manager of Bombardier Recreational Products Boats and Outboard Engines Division. Nobody knows how to design and build recreational products better than the Bombardier family, a group of people who practically invented the category.  As we prepare to move forward  youll see a company that will continue to gain momentum and build the highest quality motorized recreational products anywhere in the world, Lambert wrote. Were healthy; were motivated; and were ready to become a more powerful force in the industry than ever before.  

Selling the recreational products division was part of a plan announced last April that executives said would restore the corporations balance sheet and allow it to focus on the aerospace and transportation businesses. The decision came just as Johnson and Evinrude outboard dealers were starting to recover from the lost business and diminished market share they suffered after the Outboard Marine Corp. bankruptcy.
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3) Zodiac gets $5M Coast Guard order

Zodiac North America says it has signed a contract to supply the Coast Guard with 58 custom-built Hurricane 558 rigid-hull inflatable boats. The company says the deal is worth more than $5 million. Zodiac H-558s RIBs will be used on the Coast Guards new Marine Protector Class 87-foot patrol boats, in a range of Coast Guard operations, including homeland security, search and rescue, and law enforcement. The 87-foot Coastal Patrol Boats that will carry the H-558s are being used to replace the services fleet of 82-foot cutters. The boats are designed to be capable of carrying out missions in 12-foot seas. The H-558 is an aluminum-hulled RIB that is designed to launch from the stern ramp of the new patrol boats, even in heavy seas.
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4) Off throttle steering standard for PWC's
  
An industry standard for off throttle steering of personal watercraft will soon be a reality, the National Marine Manufacturers Association reports.  The standard could be available to the industry as early as next month.  Members of the Society of Automotive Engineers (SAE) Technical Subcommittee on Personal Watercraft includes PWC manufacturers Kawasaki, Honda, Yamaha, Polaris and Bombardier, in addition to representatives from the US Coast Guard, the National Safety Boating Law Administrators and NMMA. The new off throttle steering standard will be applicable to model year 2006 craft.
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5) Brunswick continues on acquisition path  
  
Brunswick Corp. has acquired the marine product business of Attwood Corp., manufacturer of marine hardware and accessories and a subsidiary of Steelcase Inc. as a continuation of its plan to grow its boat parts and accessories business. The company advised that participating in the boat parts and accessories (P&A) segment achieves a number of strategic objectives - to integrate boat and engine design and engineering; ability to offer a higher level of service to our dealers'; and provides Brunswick a chance to increase sales as well as an attractive profit opportunity for Brunswick and our dealers as after-market P&A traditionally offers higher-margins.  Plans are to solidify and integrate Attwood's operations into the Brunswick Boat Group as swiftly and efficiently as possible.
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6) NEW - Mercury Outboard Trailer Hitch Cover

We now have this completely unique addition to your rig! A stock Mercury Trailer Hitch Outboard Decoration for most any commonly owned trailer hitch. Make Waves with this Realistic Boat Motor Hitch Cover!  This unique item is not found in stores, so Order now! Watch the propeller spin you down the road! Only $26.95 + Shipping 
http://www.aeromarineresearch.com/mercury_hitch_cover.htm
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5) FREE Powerboat e-book

Obtain your FREE Powerboat e-book, by author Jim Russell, at AeroMarine Research's website:
http://www.aeromarineresearch.com/popup.htm
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6) 'Family & Performance Boating' magazine - Save 25%!

We have obtained great deals on Powerboat magazine subscriptions.  This month we have a great deal on the popular 'Family & Performance Boating ' magazine. 
 
'Family & Performance Boating' magazine - Showcases sport and performance boats in ways never before seen, and provides performance enhancement solutions to better meet the power and handling demand of today's more knowledgeable enthusiast.  9 issues Published:  Seasonal  
Cover Rate: $35.91 Our Rate: $26.99 (25% savings!)
Get yours now at: http://www.aeromarineresearch.com/boating%20magazines%20discounts.html
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7) FEATURE ARTICLE - How does a tunnel hull work? (Part 2) 

What makes the tunnel hull work? (Part 2)

This is a multi-part article on the engineering basics of what makes a tunnel hull work.  

Last issue we looked at the fluid dynamic forces involved in making a tunnel boat work.  Recall that several requirements must be satisfied for an object (boat) to maintain a steady, stable, straight-line velocity.  
(1)	Lift = Weight.  (Discussed in Part 1)
(2)	Drag = Thrust.  The drag experienced as a result of a velocity and all the lift mechanisms must be overcome by the available thrust.  
(3)	Pitch = Null.  (Discussed next time)

This issue we will look more closely at the 2nd part of the picture - drag and thrust relationship.  

The propeller is the source of all available thrust and must be sufficient to overcome the drag created under running conditions.  The drag of a tunnel hull is made up of both aerodynamic or 'air' drag (drag from the tunnel and deck surfaces as well as appendage air drags such as driver, cockpit area, motor, etc.) and hydrodynamic or 'water drag' (from the planing sponsons and motor appendages under water).  Although the water drag is responsible for most of the trouble, particular attention to the air drag will pay off at high speeds.

Up until rather recently in the history of power boating, one could say quite safely that the 'air-drag' of a hull was really not very significant.  Today however, with the super-fast high-horsepower racing tunnel boats now easily exceeding the speed of many light aircraft, careful attention to the smallest details of hull design is necessary to reduce the drags and squeeze every last bit of speed and stability out of the boat.  Better performance can be achieved even on lower-speed Family or commercial Tunnels when particular attention is given to aerodynamic drag reduction.  

As with the tunnel lift, the Air Drag increases as the square of the velocity and also as the angle-of-attack increases.  So air drag can become a rather significant problem at high speeds and high angles of attack.  This air drag originates in basically three (3) forms: 

(1) Skin Friction is the drag created by the passage of the fluid (air in this case) over the exposed surface area (the tunnel and deck surfaces).
(2) Induced drag is the drag created due to the lift generated by our aerodynamic 'wing' (the tunnel roof and deck surfaces).  This portion of the drag is there to remind us that we really don't get all that nice lift for free!
(3) Profile Drag is the one that can be both designed into a hull and improved upon with an existing hull design.  This is the part that is reduced by fairing the cockpit, shrouds or appendages.

While we're on the topic of appendage drag, it's noteworthy to point out that such 'appendages' as the driver and/or passengers, windscreen, outboard motor area, and even race-boat cockpit fairings do create air-appendage drags.  It's well worthwhile keeping these areas both as small and as clean as possible.  

Water Drag is generated basically in two separate, and for the most part, unrelated areas.  These are drags caused by the motor appendages (skeg, torpedo and propeller) under the water, and the sponson planing areas on the surface of the water.

As with aerodynamic drag, drag generated by hydrodynamic surfaces can be categorized into three separate contributors.  

(1) Frictional drag is a function purely of the surface condition (which we assume perfectly smooth and flat) and the 'viscous-force-ratio' - in our case, how fast the planing surface is going with respect to its length.  This viscous-force-ratio is called the Reynolds Number, and is used to simplify comparisons of different sized objects, at different speeds.  The total surface area exposed to these viscous forces (i.e. the wetted surface) tells us just how much friction drag we will have. 
(2) Induced Drag is caused by the lift generated by the planing surfaces.  The lift generated by the difference in pressure between the lower surface and top surface of the sponson bottoms 'induces' trailing vortices at each edge of the surface (i.e. the inside of the sponson or keel, and the outside chine).  A higher Aspect ratio running 'pad', will in general reduce the induced drag.
(3) Profile Drag or 'form drag' accounts for the types of drags that do not normally depend on the 'Reynolds Number' or hull velocity.  These drags are generally constant for a given hull configuration and include the effects of hull discontinuities, hull curvature, and drag caused by interruptions to the smooth flow of the water along the surfaces or 'separation drag'.  

Appendage drag or motor drag is difficult to calculate in a simple manner, since there are so many different designs of lower units in use today, and since every boat has the drive unit set up just a little bit differently.  

The Skeg is really just a kind of wing, flying through the water - sideways.  The 'Torpedo', or the part of the lower unit that houses the transmission, etc., is actually just a projectile moving through the water generating drag. The Propeller is a multi-aerofoil component generating lift and drag in all different directions.  (One of these directions we call thrust, and we use it to 'propel' our boat).  As far as additional drag on the hull however, the propeller contributes very little.  The total drag of the motor then, is determined in a based on the velocity of the hull, and the 'type' of motor lower unit.  (The AR Tunnel Boat Design Program software does a complex analysis of the lower unit forces based on each unique configuration).

You can see that balancing all the pros and cons of lift and drags is the key to high performance powerboat design.

Next week we'll look at the 3rd part of the picture - Dynamic Force Balances

See you next time!

/Jimboat

