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Don Aronow had this in a notebook...

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Old 03-13-2004, 12:24 PM
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we looked for data on the east coast boats and could find litttle...same for some of the west coast boats...one thing we laughed about is that if the company has "been around" chances are their is a market demand for the characteristics of the boat...these are probably well planned hulls from the littlle I could see...

...want to have an example of a poorly balanced boat? Take a 18'er designed for water skiing; maybe a bowrider and stuff a 525HP in it ....you will need lots of trim action to keep the thing under control at full speed if you could hit say 90-100mph... the first "roller" that hits and you are out of the boat...

by the way....Cats are really safe at speed...you just have to know "your limitations" in terms of speed vs. conditions...
 
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Old 03-13-2004, 12:30 PM
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Oh course, in reality, length matters a great deal, in boat hulls too.
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Old 03-13-2004, 01:34 PM
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Quote:
Originally posted by CAP071
QUOTE "a "perfect hull would need no trim tabs or engine trim" so a perfect hull dosen't exist"


When was the last time You seen a perfect wave
Actually when we raced the 36 Skater neutral trim and no tabs was the best way to run. The only time any trim was used was in the turns to keep the rpms up.
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Old 03-13-2004, 02:53 PM
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...we had a Friday conference call with boaters from all around that we new ...we networked...and used the services of a friend at an engineering team ....we did some research Troutly..and some cutting and pasting...but it was to feed numbers into a spreadsheet that we had calculations on and force ranked hull efficiencies as best we could.

We looked at mostly Aronow designed boats along with Pantera. Why? They are the one's we are looking at as some of us are trading up...it's just the kind of boats we liked is all..so we didn't look at everything...

by the way..the 31'-35' Formula Fast-techs are deemed quite efficient by our numbers..

...we won't mention all our sources but we had techs and an ngine bulider and a v-bottom racer and a rep from a maufacturer who shall remain ananymous on the call...

...the fun thing we found is that STEPS/BOTTOM DESIGN and an efficient DRIVE rank as #1 in overall performance.

the x-dimension is determined by hull performance....and that is not easy to modify....

...so the bottom line is "our standard" for a great hull design in the 35'-40' range is one that can run in the 80+'s all day long and do it safely...with a pair of 525's or a similiar powerplant. Why 525's? High tech...reliable; dependable and reasonably priced HP engines. More fun/less headaches.

....pick up Powerboat etc and that's all you need to know...if it's 35'-40' and can run around these speeds and meets your needs you should be in good shape in having a very efficient package that you won't feel the need to tweak when you get it...
 
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Old 03-13-2004, 03:03 PM
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Troutly...here is a link that offeres what Crouch and Pascal mathemathetics usd to derive it came from....he was from waht research we have done..and unfortunately not much is there...an individual affiliated with NASA in some capacity. They studt hydrodynamics and extrapolate the principles to aeronautics...that's why astronauts rehearse in a water tank...trim tabs on a boat work in a similiar manner to take of wing extension tabs/flaps on a plane...a plane can shift fuel from one side to the other to trim the plane...a boat can use tabs...a polane could too...anyway here is the link...if you wish to do some cutting and pasting of your own.


http://homepages.borland.com/nmp/nmpIndex.htm
 
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Old 03-13-2004, 03:21 PM
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sure length matters...but remember in an efficient planing hull a lot of the hull is out of the water..and with steps aeriation actually floats the hulls on bubbled water....and air....so it matters more if the hull is slow to pull out and acts more on the side of a displacement hull as opposed to a very efficient planing hull...an example is an older wood Cris craft displacement hull of around 25' that has 500hp and has a top speed of 40mph. vs say a 24' Pantera with 500 Hp that can hit 80mph. The Pantera is more efficient and at full speed with this power safer than a displacement hull being "forced" to go fast by pushing huge amounts of water...the Pantera glides on the surface...

...so length matter a heck of a lot more on a displacement hull and remember if the planing hull is less efficient it has to displace more water than it's counterpart...so planing hulls displace some water obviously...but the really efficient stepped one's and cat's displae much less. It's an equation you can find at the website I sent Troutly. What a good stepped design does is combine aerodynamics with hydrodynamics...a displacement hull is all hydrodynamics...if a 42' Cig/Fountain/OL had wings it would take off in a second!
A displacement hull wouldnt ....those new Luxury cruisers that you can get with a diesel power that do 60+mph are hybrid planing/displacement hulls.

Hope all this helps...we had a fun day yesterday putsing around with all this...do we have all the answers? no ....bet we were able to "get into the head" od Aronow and his counterparts and come up with some interesting speculative observations using a simple equation and a spreadsheet....you guys can do the same thing....make a spreadsheet...put the formula in...look up data from the Magazine tests and determine co-efficients of drag based on the equation and force rank your numbers....

you will find out why fast boats go fast...how to possibly go even faster...and how to enjoy an older slower boat that is a calssic and fun to operate....hey some guys like big blower motors...my buddy at work could care less about all this...he wants a BIG 45' non-stepped boat with Sterlings and dosen't care if he hits 75.

...so we all are not the authorities on anything but a fun day with some math and principles...we got to be boat designers for a day...and quite frankly short of cutting the weight down with exotic carbon graphite composits we couldn't figure out a way to make a good 40'er do more than what's available...but we figured that with "stealth" technology and Carbon/grahphite and Sterlings you could probably hit 300mph on the cad/cam.

....so if we ever can get the tech and get it at a reasonable price 20 years from now we will be looking back and wondering haw the average boat in 20 years can do say 200 mph with a couple 525's...

it can be done...it's a "going to Mars thing"....as Chef Emeril might say!

.....BAM!
 
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Old 03-13-2004, 03:43 PM
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C= the following

250 Non step V-bottom
275 Step V- bottom
300-350 Cats

I have used all of these in formula as a constant except in the one that uses the gear and propellor pitch where the constant is 1056.

Use your current realistic factors for the equation and see how close you are don't forget to factor in prop slip. You can figure your prop slip by taking your current top speed and divide it by the perfect top speed with no slip factor.
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Old 03-13-2004, 03:45 PM
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So to make very long story very short...let me sum one thing up....


....all planing hulls displace a percentage of non-aeriated water....

...the less water that is displaced (and dicplaced is like taking the palm of your hand and quickly moving it in a sideways position underwater...you can feel the resistance/drag on a small scale) the easier the boat will travel from point a to point b. Period.


Some palning hulls displace more water than others beacuse:

-Balance...they bounce up and down hitting the water in the front with the bow and causing drag.

-They don't get up on plane as much as other boats or they ride at less efficient geometries.

-They don't have air bubbles under the hull which increases a sliding effect or lubricates the bottom. An air/water bubbled mix is easier to get through....it's like moving your hand through bubbled air from a jacuzzi...less resistance you can try at home....now I feel like Mr. Wizard...


....so all we did is take some complicated equations...crunch numbers and shed some light on what goes on under your boats.

.who makes the best boat and who has the best boat out there? YOU DO IF YOU ARE HAPPY WITH IT!

...so our conclusion is that steps are not a "fad" they are here to stay for those who want cutting edge efficiency... and that there are very efficient boats without steps too...but when you get bigger you displace a lot more water....anybody know Troutly of a non-stepped 42'er that does 85mph on 525's...not to pick on Troutly but this time I did the work...and we all benefit...nobody has all this anywhere to cut and paste....and it all makes sense...

....and cat's plane instantly and need less tab control becasue they are really hydroplanes in disguise....Aronow dabbled with them..I have been in a Skater and it's a blast! Why are insurance rates higher? Because there is the POTENTIAL that a weekend warrior can do some wild things and it's all about experience..someone asked if boats are going to fast...my response after doing all this carp is yea definately for the underexperienced or someone drinking and boating you bet. Weekends with the kinds on board os not the time to "do a Poker Run".....so as troutly says...boat responsibly...

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Old 03-13-2004, 04:05 PM
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sean stinson

Good Post and yup...Cats are exactly where you placed them..to get to 600 you have to have wings..!
 
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Old 03-13-2004, 04:10 PM
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Very nicely said
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