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Conventional V-bottom hydronamics question..........

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Old 12-30-2007, 08:02 AM
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Originally Posted by monstaaa View Post
a good analogy is pouring a little water on a waxed tile floor then droping a waxed tile shiny side down on top of the water . then trying to pick it up. wont be easy. flip the tile to the un finished satin side and it lifts .
same method or theory when wet sanding the bottom fore to aft.
Yes but on the smooth side the tile will slide from side to side much easier. America's cup boat spend more money on speed then anyone and they no longer sand the bottoms they make them as perfectly smooth as they can.
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Old 12-30-2007, 11:11 AM
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Surfboards must benefit from dimples holding contact with with water for high speed control.
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Old 12-30-2007, 11:13 AM
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I recall the ABN Amro boat won the ocean race. I saw it in Annapolis and the entire hull was dull from apparent wet sanding.
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Old 12-30-2007, 05:08 PM
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My first question is how fast is the package going to go? If you only go around 65mph, keep the motors low. Gains from reduced drag of high motor position won't show up until your around 75-80 +. If your going slower than that with a high motor setting, you will lose percentage slip and the ability to carry the bow with trim. That could make you slower.
Tuff boat....my buddies Midnight is about 12000= pounds. He has quad 300 optis on a 24" set back bracket and his over revving at 6k+ with 28 B1's runing 85 on gps.

My boat is going to be extremely lighter due to resin type and foam coring. Estimated 30% lighter.

I have 36" of set back on bracket and another 12" with notched transom.

I will be must likely be going with quad 250 efis. So I plan on running the same speed 85++if not more.......

So to pose question again ...........with notched transom and set back on 24degree deep Vee how high can I go.

Max top end is the goal.
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Old 12-30-2007, 08:24 PM
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Enforcer, 36 inches and 12 inch notch. I think You'll be lucky to hit the set up on first try. Do you plan on cowlings almost touching and solid mounts? You might end up with center engines higher relative to the bottom then the outside. The outer motors will take a whopping barking in choppy water. I would think you will start with them up 9 inches or shafts even with the bottom given the are so far back. The center two maybe higher. The water will rise about 1 inch per foot of set back. I also think you'll want 3/4s of your prop in the water to carry the boat. Ultimately you may change the height a few times before your happy. If you can take pictures or measure your buddies boat it will certainly help cut down test time.
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Old 12-30-2007, 08:36 PM
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Thanks for the reply. they will be on 24" centers, the beam is 9'6, I will be most likely going with pre 2002 motors-(skinny cowlings)also due to cost of four and $$$$ trying to get most bang for buck and can't see spending 70K on new engines.

I was running my old Midnight with shafts even with bottom. I will do this again. I have been lookin at a lot of set ups. It looks like the Sutphen with quads uses 20"s on outers and 30"s on centers. But the beam is not as wide.

I also put my buddies Midnight in here, he is running 20's on outers and 25 centers. But his bracket is set up for 25 centers and he does not have a notched transom.

And also a Fountain.

We were both wondering how the water flow off of the v to notched transom and then to bracket will channge set up or effect the handling speed etc...

I have set my bracket up for 30" centers. Just wondering if I can get way with 25"s in center????

Thanks for the help ,Tony
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Conventional V-bottom hydronamics question..........-sutphen-quad.jpg   Conventional V-bottom hydronamics question..........-tommys-mid-quad.jpg   Conventional V-bottom hydronamics question..........-fountain-quad.jpg  

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Old 12-30-2007, 09:06 PM
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I haven't researched much but I would tend to think 25's in the center
Did the fountain have different pitch props on it? I would think the centers are higher and truly surfacing the outers need more bite. Also notice the fountain swing in in the center. In reality its possible the outer surface as well when the hull lifts at top speed.
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Old 12-30-2007, 09:18 PM
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I have heard of and tried different size pitchs on outers and centers. The problem with outeres being so high is when you turn boat they will cavitate. I went to four blades and problem was non existent.

25" centers would be a lot easier to find.

I want to keep the top of engine cowlings as close to even with each other as possible.

Here's a pict of a new Homeland Security Midnight.
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Old 12-30-2007, 09:25 PM
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How wide is the notch? If its 20 inches or less it shouldn't effect your height decisions. Chances are good that Homeland boat was well tested and carries more weight than you will. Allow yourself adjustment up from that set up. Are you going to run sportmasters?
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Old 12-30-2007, 09:31 PM
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Here's my boat, it's 12" deep not sure how wide. plan is to use Bob's lowers lke the last one I had.
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Conventional V-bottom hydronamics question..........-z-new-mid-transom.jpg   Conventional V-bottom hydronamics question..........-z-midnight-home-10.jpg   Conventional V-bottom hydronamics question..........-z-midnight-home-2.jpg  

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