What about the old designs?

[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]

Originally Posted by Eric W. Sponberg

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/z...era_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]

Originally Posted by 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?

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.