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Pro's & Con's between full tunnels and tunnels with center pods

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Old 11-18-2003, 06:47 PM
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Originally posted by TopSpin80
T2x the point I was trying to get across was that a lot of people including myself and most boat builders claim their tunnel hulls are catamarans. When the true definition of catamaran from a naval architecture standpoint is not what they are producing.

Ernie
What is the "true definition of a catamaran from a naval architecture standpoint"? I'd call this a trimaran myself....


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Old 11-18-2003, 06:56 PM
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True definition.... none of us have of even want a catamaran

A kind of raft or float, consisting of two or more logs or pieces of wood lashed together, and moved by paddles or sail
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Old 11-18-2003, 07:04 PM
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but T2x raises a valid point. There are symmetrical and assymetrical cats and they are considered tunnel hulls but where in the shape and size of the center pod do you draw a like and say: this is not a cat anymore but a trimaran or a 3-point? Opinions please, semantics aside... BTW, great posts T2x and TopSpin80...
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Old 11-18-2003, 07:06 PM
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I love My Paddles and Sails................................
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Old 11-18-2003, 07:14 PM
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Cord,post a pic of the back of your boat please.
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Old 11-18-2003, 07:22 PM
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In my opinion it becomes a trimaran when the center 'pod' becomes the longer and bigger of the three pods. However I am sure there are many other opinions out there.... so let's hear them.

T2x in today's powerboat market there aren't many 'symetrical' catamarans offered. Most planing hulls do better without sponson symetry. Most catamaran sailboats however are dislacement hulls and therefore do better as a catamaran and not a tunnel.. plus they are going too slow to have any advantage in packing the air to create lift.

Ernie

what do you think?
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Old 11-18-2003, 08:15 PM
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I don't know the famile tree of the Profile 28.
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Old 11-18-2003, 08:54 PM
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Old 11-18-2003, 08:58 PM
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Here's is my take on all of this and don't take it as if I know what I'm talking about, this is just based off of what I have heard and experienced over the years.

First, I believe that a flat bottom race car does not produce a suction effect like someone said in an earlier post. All of the tunnels and devices underneath an F1 car are there the create suction. A perfect exaple of a flat bottom, zero ground effect car is an IRL race car. I believe that the primary reason that there have been a number of airborne accidents this season in IRL is due largly in part to the flat bottom, zero suction effect of the car. The front and rear wing are what push an IRL car to the ground, not the flat bottom sucking them to the track surface.

As for the boats, it has been my experience and what I have heard over the years is that cat (tunnel boat) without center sponsons work much better in the rough then that of a boat with a center sponson. Typically true tunnels have deeper sponsons then cats that have a center sponson, thus provide a better rough water ride. With two deep sponsons slicing over the waves and without a center sponson slapping the surface of the waves a smoother more efficient ride is the end result. Center sponsons can aid in manuvering, cornering in some cases and planning. Some boats need them to turn, some need them for engine and drive placement (single I/O applications), etc. If I remember correctly the center sponson on a Talon is deeper then the outside sponsons, thus making the boat corner better by staying neutral and even leaning in. I would have to say that Talon's design is a great one, considering the performance and the ride of the boat is outstanding, thus causing at least 9 different manufactures to copy or splash the design over the years. Obviously Skaters, MTI's, etc. etc would have center sponsons if they worked better in big seas. I don't see to many center sponson type boats winning major offshore races, so there must be a reason the the big boys aren't running a center sponson.

Again, this is just my two cents and I'm deffinetly no expert in this field. This is just what I have experienced and learned over the years.
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Old 11-18-2003, 09:43 PM
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Spectre 30,
I have to strongly agree with everything you've said on this topic, but I must add some to the auto comments. The front and rear wings add down-force, but the majority of the down-force comes from the venturi effect from the bottom of the car. The closer the under-body comes to the road surface the greater the suction that's created. This is the biggest reason these cars are so low. They have raised the minimum ride height in many of the fastest classes because of this incredible suction. Formula 1 cars had become so low that they were practically glued to the grown. The cars relied so heavily on the suction that a major ride height change would send them out of control during high g cornering. As the cars were lowered to within a few mm of the road surface the possibility of bottoming out became a very real danger. At this ride height the cars were generating 10's of thousands of pounds of down-force at high speeds. With these tight clearances the cars began to bottom out as the limits were pushed. When this happened the cars turned into sleds that momentarily couldn't be controlled while at the same time they lost 90% of their down-force. This is what likely killed one of the greatest F1 drivers of all time.
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