Conventional V-bottom hydronamics question..........
12-20-2007 | 05:12 PM
#11
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From: Austin, Texas
12-20-2007 | 05:41 PM
#13
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From: Apache Jct. AZ
I understood it as introducing air under the hull = less drag/aerate the props.
I'm no engi-ma-neer so I could be completely wrong.
I just know they both are expensive - and as Clay pointed out, some are Uber-expensive
12-20-2007 | 06:33 PM
#14
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From: charlotte nc.
WHOAH Gerrard!! You opened up a can here!
There are a LOT of things that matter.
1. Weight is a bigger factor than anything.
2. The step itself is not what makes a boat faster. Its the natural pitch or trim that it places the thrust, as well as depth in the water in relation to the weight being pushed or displaced.
3. There are so many bottom designs out there, that you CAN'T generally title one as better (fast/ride/efficiency) than the other based on categorical design. You have to take into account strakes, hook, rocker, tabs, etc. etc.
4. Multiple steps are actually slower a single step; and a straight bottom should be faster. (Given ALL things equal, but how could you accomplish that?) Think of it in plumbing terms. If point A and point B are exactly 8' apart, and you have three equal diameter tubes to pour 2 gallons of water through; which one do you think is going to empty First? Second? Third?
There are a LOT of things that matter.
1. Weight is a bigger factor than anything.
2. The step itself is not what makes a boat faster. Its the natural pitch or trim that it places the thrust, as well as depth in the water in relation to the weight being pushed or displaced.
3. There are so many bottom designs out there, that you CAN'T generally title one as better (fast/ride/efficiency) than the other based on categorical design. You have to take into account strakes, hook, rocker, tabs, etc. etc.
4. Multiple steps are actually slower a single step; and a straight bottom should be faster. (Given ALL things equal, but how could you accomplish that?) Think of it in plumbing terms. If point A and point B are exactly 8' apart, and you have three equal diameter tubes to pour 2 gallons of water through; which one do you think is going to empty First? Second? Third?
because the stright pipe will let the water move through it faster then the others .
12-20-2007 | 06:46 PM
#16
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From: Florida
OK.. I'll put my .02 into this, having driven a step bottom in the late 60's.
First there are many different steps for different reasons, so let's not get into that. "V" bottoms can "ventilate" the hull if the ribs are "hyperbolic", In general, think of it this way. Steps are generally faster because they don't stick as much to the water as "V"s, The step reduces the "suction cup" effect, thus reduces drag, faster speed. Pads raise the boat, more speed. "V" generally cut through the waves. Deadrise is a major component in wave crushing and also speed.
Velosity's rakes and ribs are not true parallel to the sides or the bottom / keel, they divert some of the water to the outside so the boat stay more on top. (I don't know what the deadrise is) Less friction = speed. Less friction, harder to handle, squirmy. More weight=less speed, better in washing machine. Anyone figures out how to get "all" we want from one hull. Let me know.
First there are many different steps for different reasons, so let's not get into that. "V" bottoms can "ventilate" the hull if the ribs are "hyperbolic", In general, think of it this way. Steps are generally faster because they don't stick as much to the water as "V"s, The step reduces the "suction cup" effect, thus reduces drag, faster speed. Pads raise the boat, more speed. "V" generally cut through the waves. Deadrise is a major component in wave crushing and also speed.
Velosity's rakes and ribs are not true parallel to the sides or the bottom / keel, they divert some of the water to the outside so the boat stay more on top. (I don't know what the deadrise is) Less friction = speed. Less friction, harder to handle, squirmy. More weight=less speed, better in washing machine. Anyone figures out how to get "all" we want from one hull. Let me know.
12-20-2007 | 07:16 PM
#17
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From: Beautiful Fort Lauderdale www.cheetahcat.com
* PLEASE don't let this thread turn into a stepped hull VS. non-stepped hull bashing issue!
There's no dispute that some people like conventional (non-stepped hulls) and some people like stepped hulls. There's also no argument that they both have their good/bad points, I have an intrigging question.
99% of the time, a stepped hull is faster than a non-stepped hull-- so why are some non-stepped hulls, like Velocity Powerboats as fast or faster than a stepped hull in it's own class?
I know it's not "rocket science", I do understand why a stepped hull is usually faster, because of less drag from the steps. So why is a Velocity (non-stepped bottom) so fast? What makes it so fast compared to other stepped hulls in its class?
There's no dispute that some people like conventional (non-stepped hulls) and some people like stepped hulls. There's also no argument that they both have their good/bad points, I have an intrigging question.
99% of the time, a stepped hull is faster than a non-stepped hull-- so why are some non-stepped hulls, like Velocity Powerboats as fast or faster than a stepped hull in it's own class?
I know it's not "rocket science", I do understand why a stepped hull is usually faster, because of less drag from the steps. So why is a Velocity (non-stepped bottom) so fast? What makes it so fast compared to other stepped hulls in its class?
12-20-2007 | 07:21 PM
#18
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From: Florida
Pad bottom? Simply put; nothing supports weight like a horizontal surface now the trick (bad word) is how much of it?[/QUOTE]
Yup.. In theory, a piece of plywood with a motor on it is the fastest design.
Yup.. In theory, a piece of plywood with a motor on it is the fastest design.
12-20-2007 | 07:25 PM
#19
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From: SoCal
Good responses.......I was wondering how the non-stepped Velocity can be as fast as the stepped hulls. I think Paradox summed it up best about how the steps work (I had a pretty good idea of that already)
Griff also mentioned the pad bottom. I just find it interesting that the non-stepped boat can be as fast or faster. The reason I say this is because when you take a conventional hull-like a 38 Top Gun with 500EFI's the boat will probably run 72pmh at best. Compare it to a TS Top Gun with the same 500EFI's and WOW!!! This boats runs almost 10mph faster!!! There is a huge speed improvement.
Griff also mentioned the pad bottom. I just find it interesting that the non-stepped boat can be as fast or faster. The reason I say this is because when you take a conventional hull-like a 38 Top Gun with 500EFI's the boat will probably run 72pmh at best. Compare it to a TS Top Gun with the same 500EFI's and WOW!!! This boats runs almost 10mph faster!!! There is a huge speed improvement.
Last edited by Semper Fi; 12-20-2007 at 07:31 PM.
12-20-2007 | 07:25 PM
#20
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From: Tampa, Indian Shores Beach
Velocity, are much lighter than similar boats with the same power and size, they are usually 15-20% lighter. Thus faster.
On a personal note WOT stepps don't even matter, how much of a boat is in the water at WOT, about 20" in the rear, way past the step, however a pad can make a huge diff.
Just my 2 cents
WILL
On a personal note WOT stepps don't even matter, how much of a boat is in the water at WOT, about 20" in the rear, way past the step, however a pad can make a huge diff.
Just my 2 cents
WILL
