A new approach with foils ?

Forerunner model:


http://www.sciencedaily.com/releases/2015/06/150617091748.htm

http://gemini.no/en/2015/06/whale-tails-can-make-for-efficient-seafaring/

 

Manfred,

Quit teasing us.
What do you know about the details of the rationale for this proposal?
Is it being suggested for motorized boats, not sailboats?

Is this suppose to modify the bow wave to reduce energy required to move fwd?

Thanks

 

Pitch drag?

This is a very interesting idea. Similar ideas have been tried in different contexts.

My question would be how much contributes profiles to the running, and how much is the resistance reduced as the boat pitch less. Is it possible to isolate one phenomenon from the other.

In my tests with rowing boats equipped with sliding seat, I have reduced resistance considerably through a fuller hull shape. The question is even then how much more efficient is the hull in itself and that the boat pitch less. How much drag comes from the pitching movement?

When I calculated the hull, I expected an increase in speed of about 0.5 knots by improving the design. In reality, the speed increased 0.9 knots. As I see it, it just depends on that the boat pitch less when the rower slides back and forth.

http://sassdesign.net/Design of a fast rowboat.pdf

How would profiles in the fore and aft ship enhance the properties of a rowing boat with sliding seat?

js

 

Hi Marc, you don`t like to be stripteased? To get an answer for your questions is not easy. I`m not an expert - only an amateur.
But I know of some problems of big cargo ships, roros, tankers, container ships and so on. And as far as I know, pitching is not the only problem.

The hulls are not optimized for best hydrodynamics. Economy dictates the whole thing. The hulls have to be fast (~ 20 to 25kn), easy, cheap and quick to be built, easily and fuel saving to be driven and have to carry as much as possible. They are prone to rolling and are really dangerous in waves from astern. Some of them capsized in tank tests and in reality.

CAPSIZE AFTER ROLLING AND BROACHING


These hulls have to be substituted by several technical measures. The newest is to attache foils to the underside of the vessel near the bow.

As I have no possibility to watch the expensive tests done by experts I can only repeat the "results" which you can get by reading them in the different links which mostly have the same text with only slight differences.


But one thing seems to be clear: You do not need to fit the bows of your boats with these foils. If you have your boat designed by a naval architect of which you can find some (very remarkable) in this forum you will absolutely not need such a substitute for the underside of your boat. And please do not forget the lift to drag ratio.

Second: I do not think, that the foils (directly) modify the bow wave and reduce the energy needed to drive the ship. The amplitude of the bow wave might be reduced because the pitching will be reduced and the inventor claims for the "whale tail" effect. -- But do not forget the disclaimer.
Hope you can vorgive me teasing you.