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

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Old 12-21-2007, 01:40 PM
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Before this thread makes a wrong turn, I just want to say thus far it has had some very good points brought out and I have enjoyed reading it. Welcome gramp but I have to ask what Velocity you are talking about that has a narrow beam? I have a 280 and the beam on it is 8'2", and the 39 that is so fast with the 700s in it has an 8'3" beam. A 38TS Top Gun has an 8' beam and a 38' fountain has an 8'6" beam, so I would say they are average if anything. Also I'm not sure what Paradox means by the stakes being designed to push the water away from the boat, my 280 has stakes like you drew for example A.
Both "V "hulls have a beam of 8'.. right, has a narrower surface.
Bottom right, allows more air, better lift, but harder when lands on wakes. geting the curve flatter in the rear and "out"... will tend to push the water out instead of straight back. The location of the curve will provide bow. mid or stern lift. I have an old INfinity, one of the last made with variable "rib" / strake design. one of the fastest 26' (with 454)and rides like a Apache in rough. (lol.. I can see all the Apache owners geting after me for this one )
Conventional V-bottom hydronamics question..........-v-hull-2.bmp
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Old 12-21-2007, 05:23 PM
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Read My Next Post..........i Got Another Question!!!
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Old 12-21-2007, 05:24 PM
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Old 12-21-2007, 05:24 PM
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OKAY................. Here's another question...

Why does the 32' Advantage not need tabs, even running in rough water? I have never been in one, but every offshore boat I have ever been in needed tabs in rough water.


The 38 TS TG didn't need much tab at all. I think it's one of the best rides out there that I have ever been in. Boat flys very level.
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Old 12-21-2007, 06:02 PM
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That pic on the bottom right with the arch looks like you have the shakes bro- get another drink before they get too bad!!

J/K- I know drawing with a mouse it hard!
No prob. But sorry Mark,, can't drink..
Doctors order. Something with the pencrious chitt. It's shut down,, no cure.. no drinks..
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Old 12-22-2007, 08:44 AM
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I'll agree.

It also has less hull in the water a.k.a running surface; which provides for reduced drag.
A 26' boat and a 28' boat with like bottom designs that weigh EXACTLY the same; down to the ounce, with IDENTICAL power... Which one will be faster?
The one with the least drag.
true. using skater as an example the 28 is heavier longer and wider, yet with the same o/b power is faster than the 24.
i find this impressive.

as well as this
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Old 12-22-2007, 10:10 AM
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Not really on single step 38+ footers. How long did he keep them; a year? Two?
That is, before moving on to multiple steps... where he has spent a plethora of time dialing in.
There is more to it than that. The Fountain Factory is 2 hours away and so is Joey Griffin - my engine builder and most know the relation of Joey Griffin & Fountain. That said, I have spent some time down there to ask questions. Fountain uses twin step design because they want their boats to be the fastest / safest boat they can build.



But the following is what I learned at Tres' school:

The single step hull design makes for a skittish ride, plus the pivot point when turning is farther forward. Multiple steps generally ride better and are more predictable in turns and the pivot point is rearward (where the weight is) and thus turns more confidently.
I assume that if you want a better riding more predictable turning boat especially at high speeds, then most builders are going to use and "dial in" what works better.

If you doubt me, I'll be glad to refer you to Tres Martin.
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Old 12-22-2007, 10:38 AM
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OKAY................. Here's another question...
Why does the 32' Advantage not need tabs, even running in rough water? I have never been in one, but every offshore boat I have ever been in needed tabs in rough water.
The 38 TS TG didn't need much tab at all. I think it's one of the best rides out there that I have ever been in. Boat flys very level.
Alot of this has to do with the builder and balance.
When a boat hull is designed, it is done with certain things in mind, usually something like this:Twin 525's & Bravos, a cabin, and a cockpit.

In a readers digest version: The boat is tested and minor changes are made so the boat is balanced. Everything that went into that boat - the weight of components & location was thought out so the boat would be balanced. Ok, so you you have a properly designed/balance boat right from the designer.
Now the builder wants to sell boats to more people so they add, A/C, Toilet, hot & cold water, 5000 watt audio system, shower and more creature comforts. What does that do to the original balanced design of that boat - likely nose heavy? Maybe they installed all creature comforts on the port side - refrigerator, AC, Stereo, hot water. . . . . .what about balance??
or,
Builder installs mega HP motors, #6 drives and adds 3 more batteries. What does that do to the original balanced design of that boat - likely stern heavy?
Ever heard a builder say: "If you want A/C then I need to add 2 more batteries so the boat stays in balance"?

I am not sure who designs all the big names in boats, but AT is a Harry Schoell design and the Cig Top Gun is Michael Peters.
Now, if Cig or AT gets an order for a boat, and the guy wants big power and #6 drives, do you think either of these manufacturers call the designer and see what needs to be done to offset the added weight so the boat is as the designer intended?
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Old 12-22-2007, 11:25 AM
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Alot of this has to do with the builder and balance.


Builder installs mega HP motors, #6 drives and adds 3 more batteries. What does that do to the original balanced design of that boat - likely stern heavy?
Ever heard a builder say: "If you want A/C then I need to add 2 more batteries so the boat stays in balance"?

I am not sure who designs all the big names in boats, but AT is a Harry Schoell design and the Cig Top Gun is Michael Peters.
Now, if Cig or AT gets an order for a boat, and the guy wants big power and #6 drives, do you think either of these manufacturers call the designer and see what needs to be done to offset the added weight so the boat is as the designer intended?
Yes I do think (I know) A.T. has changed things around. There is different stepp inserts for the molds for different drive and power combos.
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Old 12-22-2007, 11:29 AM
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There is more to it than that. The Fountain Factory is 2 hours away and so is Joey Griffin - my engine builder and most know the relation of Joey Griffin & Fountain. That said, I have spent some time down there to ask questions. Fountain uses twin step design because they want their boats to be the fastest / safest boat they can build.



But the following is what I learned at Tres' school:

The single step hull design makes for a skittish ride, plus the pivot point when turning is farther forward. Multiple steps generally ride better and are more predictable in turns and the pivot point is rearward (where the weight is) and thus turns more confidently.
I assume that if you want a better riding more predictable turning boat especially at high speeds, then most builders are going to use and "dial in" what works better.

If you doubt me, I'll be glad to refer you to Tres Martin.
I conversed with Tres about his thoughts on the Single Step and the AT, Cigarette, Fountain and a few other things. I think ANY ride/hull is open to interpretation, driving style, and comfort level, and then an opinion is therefore formed.

While the pivot point of a single step (in this case example, the AT), is further forward than a twin step anything, you can take this to the bank: The single step will ALWAYS pivot on that one step, guaranteed; at 30, 50, 90, 110, -whatever mph. OCCASIONALLY, a multiple step boat, with confusion between the driver input, seas, load, fuel, weight transfer, speed, trim settings, etc, will pick a different pivot point (step) than the driver expects. This will not happen with a single step bottom design. Can you swap ends on a single step bottom? You bet. Can you do it on a multiple step bottom? Yes. Can you do it on a straight bottom? Yep, can be done. (With the proper training and experience, i.e. gained from Tres' class, you can make any boat do just about any turn, but you have to know how to turn, how to equal the pressure on both sides of the hull, etc. etc.)

(Great media: The Donzi videos that were shot for Miami Vice promos REALLY show how a multiple step boat turns. You can clearly see the transom taking a different track than each of the steps, and you see the water stream/cut off of each step. Those videos were done in FLAT water. If you are in ROUGH water, each of those steps is not going to be in contact with the water at all times. In that case, a step that is in the air, not water, will NOT be acting as pivot point.)

Also, just for example, an AT is going to have a pivot point further forward, based on weight distribution/COG as compared to ANY TS/TG, as the AT has a full finished cabin, comparatively having considerable more nose weight than a 1/2 cabin derivative boat.
Again, this is not a better than/worse than situation; just something to account for.

You were in the boat when Tres (purposely) whipped the 180* turn in Rich's AT. What did you think? Was it skittish? Would you have liked that same turn in your boat? Just curious.

Last edited by Sydwayz; 12-22-2007 at 11:38 AM.
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