What about the old designs?

[big-boss]

Why are the old hull shapes gone in racing boats? Like the Gar Woods, Bootlegger, etc.? Is the deep v-Cigarette that much better? Thos old boats went 60 to 70 MPH with an old V-12 or whatever with lots less power than say a Chevy BB Merlin of today- lots more weight.
Where did all the old hull design/ Theorys go?

[PAR]

Change is the most essential element of all existence. Without change, the dinosaurs would still be here and we'd be furry little things, clamoring around in the rocks.

In the early 1960's formula one cars were cigar shaped, had skinny tires and no wings, but they changed to what we have now.

In the 1930's we had many successful hull forms, most V shaped did best at higher speeds. As time marched on, the natural refinement of these early shapes have developed into what we see today, which isn't as radical a departure as comparing a 1960 formula car to the current versions. This suggests the yacht designers in the 1920's got it very close, requiring subtle refinements to the present day forms.

To answer your question directly, we are seeing those shapes today, but refined and tweeked a touch.

[lazeyjack]

Remember Slo Mo Shun?
Most racing today is offshore, the entry must be deep, power to weight ratio has gone through the roof, and diesels rule the waves
http://www.slomoshun.com/
here build your own:))
http://www.classicthunder.org/SetUp/SloMoV/Building_V.htm

[big-boss]

I understand the change/ time thing. Water is still the same and so is prop HP. My question is: Why did say the "baby Bootlegger" go the way of the dinasaur? Lighter engine/ Horsepower would surly have helped performance. THe change from a rounded flat bottom? To the deep-V ( knowing that the off-shore modern cats are simply Don Arno cutting a deep-V Apache/ Cigarette down the middle). How did we end up with the deep Vee?

[Tad]

Why did say the "baby Bootlegger" go the way of the dinasaur?

Modern powerboat hull design history is a fairly thick book, with many twistings and blind alleys. Lots of folks had a hand in..... As PAR said above, Baby Bootlegger was simply outclassed by further developments. The BB hull was a variable deadrise vee bottom, with approx. 3-4 degrees of deadrise at the transom. This is fast in flat water but horrible in big waves, it will pound a boat to bits. Thus Hand and Hunt/Levi after him increased deadrise all the way to the transom to handle a sea better at high speed. More powerfull engines were being developed (war effort) by auto and airplane companies. This allowed the effective use of the power-hungry (higher resistance) deep vee. Modern boats use various forms, not just a deep-vee, as we know (through research) that one size does not fit all. Many production boats utilize variable deadrise, some use low deadrise, steps, notches, flats, pads, etc.

[big-boss]

Tad, Thanks again that is good info. Do your boats have "sort of" the hull shape of the old BB?

[Tad]

Not really even close to BB, though somewhat inspired by all right. Rooster is wider (to house twin big block v8's) and runs surface drives under her tail. Pretty and quick, about 72mph tops.

20642

20643

20644

[juiceclark]

For better or for worse, in this business what survives and evolves is what sells. We've just passed through a period where smaller boats all look the same and are rather hideous. (but quite shiney) Perhaps buyers in the < $1MM range will start demanding some style for their hard-earned money in the near future.
Tony in Sw FL

[Eric Sponberg]

In my recent work, which includes the retro-styled Cherubini Classic 20, I specifically looked at marrying the classic hull shape above the chines with the modern underwater shape of the deep-V hullform. This is because the older designs, although fast, were terribly rough riding and a little dangerous. They were wet and sometimes hard to control in turns.

The deep-V concept that came out of the Hunt Design office for the Bertrams was indeed far superior to the classic hull shapes. All the science of planing hullforms since the 1960s has been devoted toward refining these types of bottom shapes. Stepped hulls are a continuing development of that.

Last year, I designed a deep-V bottom for a reproduction 21' Chris Craft Cobra, which was the 1955 design with the fiberglass tailfin on the back. It had the old style flat bottom aft and concave sections forward. I am going to write a story about this on my website soon. Basically, I took my CC20 deep V hullform and stuck it on the bottom of the Cobra. This boat is now built and running, and it seems to run well. The deep V is 20 deg deadrise at the stern, and this is a very constant shape for about half of the boat's length. The bow sections forward and below the chine are convex sections for a softer ride. The forefoot (keel profile shape forward) is shallower on the reproduction than in the original.

My client also purchased within the last year a real original 21' Cobra which happened to be the Chicago boat show boat from 1955 which was owned by the original owner. So my client now owns two Cobras, one original and one redesigned reproduction, with two different bottom designs, and hopefully we can get some real world comparisons between the two. I am attaching some photos which should be interesting. The boat called "INTOXICATION" is the Cobra original. That is also the original trailer. You can see the two bottoms, the original flat bottom and the newer reproduction deep-V.

The modern deep-V hullform is superior in design and performance to the designs of yesteryear.

Eric

[big-boss]

Eric, thanks for the information. Great work! What is that wood skid loking thing under the orig. boat? IS it simply the trailer or some thing to keep it all stright?

[Pericles]

Do you mean the piece of vertical ply,timber situated over the propeller under "Double Take"? It looks like a protection for the propeller whilst reversing the rig.
Actually, where are the rudders on both craft?

Pericles

[SC1]

old style, new tech: http://www.youtube.com/watch?v=FsNXIITGUvA :cool:

[SC1]

Here is the new 27´Super Cobrajet we at the moment are building.
500Hp 6.6L Duramax V8 Turbodiesel / Rolls-Royce waterjet ;

[Eric Sponberg]

Eric, thanks for the information. Great work! What is that wood skid loking thing under the orig. boat? IS it simply the trailer or some thing to keep it all stright?

Do you mean the piece of vertical ply,timber situated over the propeller under "Double Take"? It looks like a protection for the propeller whilst reversing the rig.
Actually, where are the rudders on both craft?

Pericles


I made a bit of a mistake--the stern of the "original" that I posted is that of another original Cobra 21 that was at the show, "Hemi Under Glass". The black things the boat is sitting on are the bunkboards of the trailer. The rudder is right there in the center behind the prop. The same on the reproduction, "Double Take", the bottom is clean and the rudder is the first thing you see there behind the prop.

I am adding in the stern view of "INTOXICATION". Note the anti-cavitation plate at the stern. The original owner told me he added that plate onto the hull during his first year of ownership, after he had pitched his wife out of the boat during a turn. In that incident, and I think it was during her very first ride in the boat, the rudder had suddenly ventilated and he lost control, and the Mrs. went flying over the side. They remained married up to her death a few years ago.

Eric

[Tad]

where are the rudders

Rudders??......rudders?

We don't need no stinking rudders! Rudders are sloooow dude......

[big-boss]

If you look at the Starb view of intoxication. It is setting on some sort of skid not really attached to the trailer. I heard back in the old days they did not drive the trailers into the water like we do today- they skidded them down? Looks interesting.

[Guillermo]

So my client now owns two Cobras, one original and one redesigned reproduction, with two different bottom designs, and hopefully we can get some real world comparisons between the two.
.......
The modern deep-V hullform is superior in design and performance to the designs of yesteryear.

Eric,
I'm pretty interested in knowing what the results of such comparisons. I look forward to you posting them within these forums.

All the best.

[Pericles]

Tad,

Single engine & prop? How is the boat steered?

[Tad]

Perry,

The boat I posted above is driven and steered with articulated Arneson surface drives. Steering is done by directing thrust (like a sterndrive) rather than by diverting fixed thrust with a rudder.

http://www.arneson-industries.com/

[Pericles]

Tad,

I thought we were discussing Eric's two vessels on the trailers, at the time I posted. The beautiful craft you designed carries its Arnesons very well. An upside down 1914 Roll Royce?

http://www.conceptcarz.com/vehicle/z10349/Rolls-Royce_Silver_Ghost_Shapiro-Schebera_Skiff.aspx

Regards,

Perry

[Wayne Grabow]

If we were working with the same power-to-weight ratio as the old classic speedboat designs, would the variable deadrise still be competitive? Is the modern deep-V a better design regardless of applied power, or is it simply better at utilizing the lighter and more powerful engines now available? If, say for the sake of increased fuel efficiency, people started asking for boats that got more miles per gallon and a little less speed, would other hull forms replace the deep-V?

[tom28571]

If we were working with the same power-to-weight ratio as the old classic speedboat designs, would the variable deadrise still be competitive? Is the modern deep-V a better design regardless of applied power, or is it simply better at utilizing the lighter and more powerful engines now available? If, say for the sake of increased fuel efficiency, people started asking for boats that got more miles per gallon and a little less speed, would other hull forms replace the deep-V?

It is not reasonable to look at different hull forms without considering the other characteristics like weight, power required, cost, fuel use, etc. The modern deep V has an advantage over the lower deadrise hull only in rough water capability. All other factors favor the lower deadrise hull with possible exception of public perception.

[PAR]

Wayne, ultimately there are many concessions used in the design process, before an end product is splashed. With a custom design you can tailor the compromises around the client a great deal. There's no such luxury in a production craft, even the limited production vessels of yesteryear. The end result with these boats, is one that suits as many possible clients as it's able, considering the design parameters which often lead to several limitations themselves.

In short, yes, continuing fuel cost increases will have an effect on hull types, but don't hold your breath. Although fuel has risen in recent years, it's not high enough to warrant wholesale changes. Consumer confidence in the economy drives the boat sales market and is a usual indicator of a down turn or up swing. Boat sales and registration have been on the down turn for a few years. New designs will not correct this, just more disposable income will.

When the economy turns around again (which it will and the nice thing about recessions) style and performance will dictate what the designers do with their hull forms. If sales continue to lag behind what expectations suggest, then you may see some "toe dipping" into the "efficient" hull types. Initially this will likely be in the form of clever advertising, but could possibly lead to refinement of hull shapes toward efficiency.

I frankly think hull shapes will evolve at a natural progression, with fuel efficiency increases covered by fuel delivery, transmission and engine calibration systems, rather then different hull shapes.

To directly answer your questions about "variable deadrise" or "classic old speedboat" hull forms. No, modern hull forms out class them in the categories we currently rate them. It is an incorrect perception that the deep V hull form is dominate in the market. The fact is that flat bottom, slightly and moderately V bottom craft greatly out sell the deep V's. Most of the slight and moderate V hulls are very similar to the old classic types, though their beam/length ratios differ, the warped bottoms and amount of deadrise remain in many cases.

[Eric Sponberg]

Hi folks,

As promised, I worked yesterday on writing up the full story on my Cobra redesign, and it is on my website now with more photos and some drawings.

http://www.sponbergyachtdesign.com/ChrisCraftCobra.htm

Eric

[yipster]

Eric, that are real nice lines, nice boat and sunny southern wheather
the standing fin i have my reservations about but maybe should bite my tong
read up on your eagler at the same time and see you'r the winner for the public
selling my 27 and harsh to read even a winning naval architect cant afford a 45

[big-boss]

Is the basic principle between new and old?
Old boats- Heavier with less power so they need to be designed to ride more in the water so you end up with the less V style.
Newer boats- Less weight more power and stronger materials you need/ can ride out of the water. Essentially "hoping" from wave to wave verse "crushing" threw.
Am I on the right track?

[TollyWally]

Eric,
What a nice looking boat your client built. While I was on your site I took a look around.

I was very interested in the lifting strake project. While the stated purpose was to knock down obnoxious spray the changes in performance were interesting. I found the graph at the end illustrating the differences that the lifting strakes made to speed at varying rpms very informative. It looks like one must really define the target well before optimizing for a certain objective.