The difference between a traditionell hull and a FasTrac hull

[kursinal]

We are doing a project about special hulls.

The one we are most interested in is the one in the picture below.
We are from sweden and we don't know the name of this kind of hull, so if you could tell us we would appreciate it.



We wouldn't mind if you could tell us some more information, because we have a hard time finding some.

Thank you in advance, Kursinal!

[kagraham]

I know it is a model of Regal Runnabouts, won some awards, after a quick google search i found some contraversy over there design, and a similar patented design of a Mr. Harry Schoell. you can read about that here http://www.rbbi.com/folders/pat/regal/regal.htm "Regal's president Duane Kuck says they will contest the suit. Kuck said FasTrac was in costly prototype development and testing for two years. David Livingston of Seattle (designer behind Brunswick's U.S. Marine/Bayliner boats said he designed it from scratch. It features include a step to improve efficiency; tunnels aft that draw air and break the suction between hull and water; inverted strakes, which keep the hull tracking; laminar flow interrupters (small steps) along the strakes, which prevent instability in turns"; two pads aft for horizontal stability: and a 24-degree deadrise."
More information may turn up by searchign the patented hull type under the name Mr. Schoell calls it. hope this helps a little maybe get you started..
-karl

[kursinal]

Originally Posted by kagraham

I know it is a model of Regal Runnabouts, won some awards, after a quick google search i found some contraversy over there design, and a similar patented design of a Mr. Harry Schoell. you can read about that here http://www.rbbi.com/folders/pat/regal/regal.htm "Regal's president Duane Kuck says they will contest the suit. Kuck said FasTrac was in costly prototype development and testing for two years. David Livingston of Seattle (designer behind Brunswick's U.S. Marine/Bayliner boats said he designed it from scratch. It features include a step to improve efficiency; tunnels aft that draw air and break the suction between hull and water; inverted strakes, which keep the hull tracking; laminar flow interrupters (small steps) along the strakes, which prevent instability in turns"; two pads aft for horizontal stability: and a 24-degree deadrise."
More information may turn up by searchign the patented hull type under the name Mr. Schoell calls it. hope this helps a little maybe get you started..
-karl

Okey thanks for your time. I've actually seen a lots of pros with this kind of hull, like faster, less fuel wasted etc...
Are there any cons?

The search didn't give me that much I'm sorry

[Raggi_Thor]

It will probably be worse than a smooth bottom at low speeds.

[RANCHI OTTO]

Less wetted surface = more speed....
Less wetted surface = less stability....

If you are looking ONLY for speed than is Ok, but if you want produce safe and easy boats than forget about this configuration.

There are other hull shape to obtain safe and fast boats.

[Verytricky]

Originally Posted by kursinal

We are from sweden

IMO, the man who got stepped hulls perfect is Ocke Mannerfelt , and he is in Sweden ( being Swedish )

www.ocke.se

[alpamis34]

Man this is the phenomenon of the stepped hull which provides two planing regions on the savitsky based planing graphs which would then lead to the higher efficiency in resistance.But the handicap is the reduction of the stability.This type of hull is generally adopted to offshore racer boats which generally require high speeds on surge but not stability.
Cheers

Tumer Berk

[David Peng]

Only for very high speed boat....It could be a twin sister of surface drive

[Raggi_Thor]

Hydrolift in Norway has also used stepped hulls wit success,
www.hydrolift.com

[RANCHI OTTO]

Nice boats..! Well done

[tgwhite]

Raggi:

Given a stepped hull's inherent instability, that picture looks like one shown on TV where the boat rolled right over. Yikes!

[Verytricky]

You definately get instability, but the reward is speed. So no slacking off during a race!

[RANCHI OTTO]

Speed is only for race boats otherwise the stability is a very important point for an high speed pleasure boat.

What is a Porsche 911 if isn't able to stop from 100 km/h to 0 in 3.5 sec.?

A good boat is always a compromise btw. various factors....speed is only one of them!

[kursinal]

Originally Posted by RANCHI OTTO

Less wetted surface = more speed....
Less wetted surface = less stability....

If you are looking ONLY for speed than is Ok, but if you want produce safe and easy boats than forget about this configuration.

There are other hull shape to obtain safe and fast boats.

Thanks, I will have that in mind. We actually had an interview with a step-bottom researcher and he told us some stuff, like you said.

Originally Posted by Verytricky

IMO, the man who got stepped hulls perfect is Ocke Mannerfelt , and he is in Sweden ( being Swedish )

www.ocke.se

Yes we are aware of that, but we can't find any information about him or his research, sadly.
EDIT: Oh, didn't see the link, thanks.

Originally Posted by Raggi_Thor

Hydrolift in Norway has also used stepped hulls wit success,
www.hydrolift.com

Thank you.

[RANCHI OTTO]

I have nothing against steps and I think that is an interesting matter for research even the influence of scale effect.

I have designed high speed boat up to 100 m.p.h. without steps...personal choiche....don't be vitriolic against me.. ..as said is only that I prefer to reach speed and stability at the same time