single step - double step
05-17-2005, 06:08 PM
#1
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single step - double step
looking to move up, the ex., has a single step square windsheild, ice box, port potty ect., I realize it is a cheaper boat, 2 things, why, wouldn't be cheaper at manufacturing to go with one bottom .With the same power are the boats same speed because I assume the double step boat is heavier
with fridge pump out head ect,
JMPH
with fridge pump out head ect,
JMPH
05-18-2005, 06:15 PM
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Re: single step - double step
A twin step is substantially more efficient. A bigger step is substantially more efficient. About 20% higher Crouch constant. A non-step bottom is typically 160-180, a single and small and/or poorly designed step bottom is about 200, while the latest Fountains are about 240-260, far better than other boats.
Here is the formula, plug in for your boat, and you'll see what I mean:
(from http://www.cs.uu.nl/wais/html/na-dir...faq/part3.html)
The formula yacht designers use is called Crouch's formula.
It takes into account the weight and horsepower at the
propeller, and assumes a 50"% to 60"% efficient prop.
Most props fall into this range. Note that it doesn't take
into account the boat length, as that doesn't matter with
planing boats.
Crouch's Formula
V = C/((DISP/HP)**.5)
Where V = boat speed in knots (1 knot=1.15 mph)
C = Constant (depends on boat type)
DISP = Displacement (pounds)
Note that boat manufacturers usually give
innacurate numbers for displacement,
typically on the low side
HP = Horsepower available at the propeller
For comparison sake, here are some average values of C:
150 Typical lightweight, planing cruiser
180 High Speed Runabout
200-230 Race boats, hydroplanes etc.
Here is the formula, plug in for your boat, and you'll see what I mean:
(from http://www.cs.uu.nl/wais/html/na-dir...faq/part3.html)
The formula yacht designers use is called Crouch's formula.
It takes into account the weight and horsepower at the
propeller, and assumes a 50"% to 60"% efficient prop.
Most props fall into this range. Note that it doesn't take
into account the boat length, as that doesn't matter with
planing boats.
Crouch's Formula
V = C/((DISP/HP)**.5)
Where V = boat speed in knots (1 knot=1.15 mph)
C = Constant (depends on boat type)
DISP = Displacement (pounds)
Note that boat manufacturers usually give
innacurate numbers for displacement,
typically on the low side
HP = Horsepower available at the propeller
For comparison sake, here are some average values of C:
150 Typical lightweight, planing cruiser
180 High Speed Runabout
200-230 Race boats, hydroplanes etc.
05-19-2005, 04:11 PM
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Re: single step - double step
The answer might be a couple things. I do know that the TS is 3-5 mph faster, but the single step will out handle it and turn harder. The two bottoms is probably because customers like choices and that is just another option they have.
05-19-2005, 06:35 PM
#8
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Re: single step - double step
[QUOTE=u4ea32]A twin step is substantially more efficient. A bigger step is substantially more efficient. About 20% higher Crouch constant. A non-step bottom is typically 160-180, a single and small and/or poorly designed step bottom is about 200, while the latest Fountains are about 240-260, far better than other boats.
I think the new Fountains are more like 280-300's close to cats..
..that means it's a great straight line boat....if you catch my drift.
How's that for start'in some chit in the "Fountain Room".
It's fine as long as you know what you are getting into....wanna hang fast tight turns without sliding and risking a spin-out??...160-200 and more power and lesser speeds...of course....faster through rougher water most definitely...need a heavier old school Cig....
Who me comment on steps? Darn it all I want speed without steps....
In reality I love hanging really fast turns..always did...I must be waiting for GLH to sell his Tiger to me or something
...give me one Fountain and one Cigarette please....
You know I love you Reggie but old school was great and new school is great and there is a price to pay for a 300ish V-Bottom stepped hull in terms of turning quickly if need or want be and of course there is a price to pay for a non-stepped or less radically stepped bottoms...
I think the new Fountains are more like 280-300's close to cats..
..that means it's a great straight line boat....if you catch my drift.
How's that for start'in some chit in the "Fountain Room".
It's fine as long as you know what you are getting into....wanna hang fast tight turns without sliding and risking a spin-out??...160-200 and more power and lesser speeds...of course....faster through rougher water most definitely...need a heavier old school Cig....
Who me comment on steps? Darn it all I want speed without steps....
In reality I love hanging really fast turns..always did...I must be waiting for GLH to sell his Tiger to me or something
...give me one Fountain and one Cigarette please....
You know I love you Reggie
but old school was great and new school is great and there is a price to pay for a 300ish V-Bottom stepped hull in terms of turning quickly if need or want be and of course there is a price to pay for a non-stepped or less radically stepped bottoms...
Last edited by Hydrocruiser; 05-19-2005 at 09:01 PM.
05-19-2005, 08:17 PM
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Re: single step - double step
Originally Posted by u4ea32
A twin step is substantially more efficient. A bigger step is substantially more efficient. About 20% higher Crouch constant. A non-step bottom is typically 160-180, a single and small and/or poorly designed step bottom is about 200, while the latest Fountains are about 240-260, far better than other boats.
Here is the formula, plug in for your boat, and you'll see what I mean:
(from http://www.cs.uu.nl/wais/html/na-dir...faq/part3.html)
The formula yacht designers use is called Crouch's formula.
It takes into account the weight and horsepower at the
propeller, and assumes a 50"% to 60"% efficient prop.
Most props fall into this range. Note that it doesn't take
into account the boat length, as that doesn't matter with
planing boats.
Crouch's Formula
V = C/((DISP/HP)**.5)
Where V = boat speed in knots (1 knot=1.15 mph)
C = Constant (depends on boat type)
DISP = Displacement (pounds)
Note that boat manufacturers usually give
innacurate numbers for displacement,
typically on the low side
HP = Horsepower available at the propeller
For comparison sake, here are some average values of C:
150 Typical lightweight, planing cruiser
180 High Speed Runabout
200-230 Race boats, hydroplanes etc.
Here is the formula, plug in for your boat, and you'll see what I mean:
(from http://www.cs.uu.nl/wais/html/na-dir...faq/part3.html)
The formula yacht designers use is called Crouch's formula.
It takes into account the weight and horsepower at the
propeller, and assumes a 50"% to 60"% efficient prop.
Most props fall into this range. Note that it doesn't take
into account the boat length, as that doesn't matter with
planing boats.
Crouch's Formula
V = C/((DISP/HP)**.5)
Where V = boat speed in knots (1 knot=1.15 mph)
C = Constant (depends on boat type)
DISP = Displacement (pounds)
Note that boat manufacturers usually give
innacurate numbers for displacement,
typically on the low side
HP = Horsepower available at the propeller
For comparison sake, here are some average values of C:
150 Typical lightweight, planing cruiser
180 High Speed Runabout
200-230 Race boats, hydroplanes etc.
Did I sleep through that class while attending M.I.T.
05-19-2005, 08:55 PM
#10
