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

Re: single step - double step
 

Not sure of Ex #'s our 05 Lightning TS with 500's is 84+ with 1/2 tank and 3 on board for comparison.

Re: single step - double step
 

Single step 35 runs around 80 with 500's -2nd step good for 3-5 mph

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.

Re: single step - double step
 

:confused:

Re: single step - double step
 

why would fountain make 2 bottoms, why not use same bottom for bothe boats, 3-5 is alot

JMPH

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.

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. :D

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.... :rolleyes:

Who me comment on steps? Darn it all I want speed without steps.... :drink:

In reality I love hanging really fast turns..always did...I must be waiting for GLH to sell his Tiger to me or something :eek:

...give me one Fountain and one Cigarette please.... :D


You know I love you Reggie :D 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...

Re: single step - double step
 

Huh??? :confused: :confused: Did I sleep through that class while attending M.I.T.

Re: single step - double step
 

Re: single step - double step
 

Bigger motors over comes all that :cool:

Re: single step - double step
 

My take is if a boat company can design a boat that goes 90+ with "stockish" power and market it and sell "speed/$$" a fast boat with less power is more profitable.

But in reality it is good we have choices....

IN some ways I wish steps were never brought back in vogue. If nothing else they break up the lines of a boat....

But I am a knob...been here and done this...wish some companys offered 2 versions. :D

Yup bigger motors...like 1050 Sterlings and a 42' non-stepped
Cigarette. Why can't I give this up? :p

Re: single step - double step
 

Yes, Hydrocruiser, this uses the exact same formula. The constants are usually called Crouch constants, named after the guy who came up with the formula, who was also a very famous designer of gold cup and other high speed powerboats in the first half of the 1900's.

By collecting data from boat tests, I find the following constants. NOTE that the constants are sensitive to weight, and as fas as I could tell, all the weights quoted in all boat tests are provided by the manufacturer -- the boats were not weighed by the publication doing the test. Therefore, these numbers are not precise:

1992 Fountain 47, no step: 209
2000 Fountain 47, two big steps: 277
2006 Fountain 47, slightly improved bottom: 284

The early boat needs 50% more power to reach the same speed. That also mean 50% more fuel.

Very similar big double stepped bottoms:
2001+ Fountain 42: 267
2000+ Formula 383: 267
2000+ Cigarette 42 Tiger: 258

My boat, single but pretty big step:
2000 Fountain 32 Sportfish Cruiser: 245

Non-stepped bottoms:
Baja 442: 237
Excalibur 47: 236

Big fat tubby powerboats:
Cruiser 405: 200

Playing with the numbers to compare my fuel burn this weekend with a theoretical identical boat with no step, and two steps:
No step: $275
One step: $235 <- actual
Two step: $215

Re: single step - double step
 

If it's not fast enough change pulleys! :drink:
Dan