TBPNews #44 - August 23, 2003 
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>>>>>> Tunnel Boat Performance News >>>>>>>>>>>>>>
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In this issue: 
1) NEW RELEASE! - Tunnel Boat Design Software, Version 7 
2) OFFSHORE RACING EVENT IS BACK - September 27 & 28
3) Law limiting PWC use defeated in New York town 
4) NEW - Powerboat Links Pages!
5) FREE Powerboat e-book
6) 'Family & Performance Boating' magazine - Save 25%!
7) FEATURE ARTICLE - How does a tunnel hull work?  
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1) NEW RELEASE! - Tunnel Boat Design Software, Version 7 

AeroMarine Research has just released the most comprehensive software revision yet, to it's powerboat design and performance prediction and analysis software.  The Tunnel Boat Design Program, Version 7 was released August 16, 2003.  With dozens of new features, the TBDP, Version 7 software included 8 new design wizards, motor design database, a quick design feature, propeller sizing, accurate top speed prediction, new acceleration models, angle increment calculator, velocity range calculator, acceleration modeling with elapsed time prediction, motor height calc's. 34 Color graphic performance charts - and all the functionality of Windows 98/98se/2000/XP.

http://www.aeromarineresearch.com/adverts/New%20Product%20Release_software7.html
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2) OFFSHORE RACING EVENT IS BACK - September 27 & 28

It's official, the "Jersey Boys" and friends are coming to town!! The CBPBA is proud to announce the return of offshore racing to the area. The last of the OPA Series will be held in Cambridge, Maryland on the Choptank River, at the Hyatt Regency.  Saturday will be exhibitions and testing. The races will be held on Sunday. http://www.cbpba.com/offshoreracing/main1.html
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3) Law limiting PWC use defeated in New York town 
  
FOOTHILL RANCH, Calif.  An ordinance that would have restricted personal watercraft riding hours and placed speed limits on all boats along the town of Lansing's stretch of 
Cayuga Lake failed to get a second vote at a town meeting, the American Watercraft Association (AWA) reported.  None of the sitting board members seconded the ordinance when the motion was brought.  The ordinance would have barred PWC operation only from 8:00pm to 10:00am in the morning, and would have placed speed limits on all vessels 1,500 feet from shore. It was stated that the AWA would work with town officials to develop a regulation for all motorboats if called upon. This area of upstate New York has seen a flurry of town ordinances proposed since the state granted local municipalities the ability to regulate their own waterways. However, few ordinances have met with approval, and all anti-PWC proposals have met with staunch opposition from the PWC community, according to the AWA.
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4) NEW - Powerboat Links Pages!

More every week!  Over 1000 Performance Boating Links!  Well organized in easy-to-find categories.  Use the Powerboat Links to find everything you need for high performance powerboating.  ADD YOUR LINK to Powerboat Links, so that everyone else can find you!

http://www.aeromarineresearch.com/pages/
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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?  

This is a multi-part article on the engineering basics of what makes the tunnel hull work.  This week, we'll look at the principles of operation and Lift/Weight balance.

What makes the tunnel hull work?

To understand this, we must examine the fluid dynamic forces involved.  Several requirements must be satisfied for an object to maintain a steady straight&#64979;line velocity.  
(1)	Lift = Weight.  The weight for the hull must be exactly supported by forces such as lift from the hydrodynamic planing surfaces and aerodynamic lift.  
(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.  All of these various forces acting, must act so that the tendency to pitch about the centre&#64979;of&#64979;gravity (CG) is eliminated.  

So for a tunnel boat (as for any boat) these forces must all balance out; and the design of the hull can be thus generalized into the three areas of hull lift, hull drag and dynamic stability.  Let us look mare closely at these areas of lift and drag.  

Part 1 - Lift and Weight

As we have noted, the hull weight (including engine, driver, fuel, etc.) must be EXACTLY equaled by the lift forces generated.  This is true for any boat (or aeroplane, too) in stable flight.  The tunnel hull must however always be in 'stable flight', and so this balance is especially critical.  Too much lift and we take off like an aeroplane - too little and we sink! 
 
There is lift generated in basically two ways.  The planing sponson bottoms create 'hydrodynamic' or water-ift (lift due to forces on and reactions with, the water surface).  The aerodynamic lift is generated by the relative air flow over the tunnel and deck surfaces (lift due to forces on and reactions with the air, itself).  There are additional sources of lift in the tunnel hull rig, such as the slight lift generated by surface piercing propellers, for example, but the contributions of forces like these to the whole force 'picture', are 
insignificant.  

It is important to note that the relative significance of these forces changes as the speed of the hull increases.  Generally, under about 50 mph, the aerodynamic lift accounts for less than 10% of the total lift, the sponsons supporting nearly all of the weight of the boat.  At the 
speeds now attainable by conventional racing tunnels, the tunnel lift can account for well over 80% of the total lift.  This tells us then, that the sponson lift is reduced accordingly, which gives dramatic improvements in the performance of the boat, as we'll see later.

Next week well look at the second part of the picture - the drag and thrust relationship.

See you next time!

/Jimboat

