Wavy Hull

[dave L]

I am just an interested observer when it comes to boat design. I try to read all I can on the subject, when I came across this link on a wavy hull design

http://www.newscientist.com/news/news.jsp?id=ns99996368

As it is from newscientist I trust that it is reputable. But I wanted to put it to the minds of this forum.
What difficulties are likely to be encountered in design & production of a wavy hull vessel? Is this an old idea or is it revolutionary? How likely is it to conform to its anticipated results?

[redcoopers]

Sounds like the theory they used is inviscid...

We have a half-hull at Berkeley in the Naval Architecture Building of a "wavy-type" hull. It's all wood and looks like it was made more than 25 years ago.

Yes, if water didn't have shear stresses, then this would probably be the ideal shape for a given speed. However, when you use a wavy-type hull, you will get nasty pressure gradients from the influence of viscosity which will then influence the wave-making.

As a student of hydrodynamics, I am aware of the many uncertainties involved: and I am wary of any new wonderful solution (water is just too complex!). However, I love to see any new developments in the field. If I had enough money to be a ship-buyer, I'd buy this design only after seeing full-scale prototype testing.

-Jon

[yipster]

the idea did cros my mind but.....

[Sean Herron]

Hello...

It's more about breaking the surface tension and laminar flow...

About inducing 'tiny bubbles' between the hull and the water...

About trying to get some foam - some seperation...

Like shark skin under an electron microscope...

But really officer - I think - actually I am sure it was two guys in a blue Ford and they were heading South at a God awful speed...

Sure - I can step out of the car...

SH.

[Tim B]

I can see that roughening the surface finish would reduce drag (ask any Laser sailer) as it's all about the maintainence of the boundary layer, but I can't quite see that sticking lumps on the hull (which is basically the case)is really going to help. It will do something for the wash, but you don't reduce powering by adding radical dP/dX es (with the exception of steps).

It's interesting anyway,

Tim B.

[jehardiman]

Old stuff, at least when I was in school. Raise your hand if you remember the "coke bottle" hulls.

All they are doing here is playing with words (what do they mean by "reduced wash"; less wake wave height?, less wake forward momnetum?, shorter period wake waves?) and the humps and hollows of wave making. We all know that we can play with the hull shape at a given speed in flat water to maximize (minimize? ) the wave making hollow and therefore resistance. But is that really useful? Especially, if the construction cost is greatly increased. What about all the off design speeds and displacements? The inability to control speed through the hollow transition may be a significant problem like it is on SWATHs.

Now some of that dolphin skin....http://www.sciencedaily.com/releases...0517072242.htm....

[Thunderhead19]

First, Popular Mechanics is a reputable magazine, and thay have printed at least one story I know that turned out to be a huge scam (Titanic Returns). That aside, Look at that shape, who is going to build it? ($$$$$$) Third, the boat is restructed to a most efficient operating speed, what happens outside of this speed? Bulbous bows are one thing, but this??

[Sean Herron]

Hello...

I think the real problem is that Green Peace might start sit ins in my lobby if I start killing off enough dolphins or sharks to skin my boat...

Plus killing and skinning sharks and dolphins requires a whole new set of skills and capital investment...

Let's change the discussion a bit - what would I use to bond the hides to the FRP - or perhaps I should build a skin kayak and take a mold for FRP so as to have a test boat...

Or perhaps I should take a year off and 'go find myself' - I think I dropped something from out of my left ear - in Idaho...

Anyway I don't buy this - until you start making stepped planing hulls - for high speed power - with outlet channels in the steps to aerate the hull - I don't 'feel' or see the theory in application - regarding displacement speeds anyway...

Imagine a 'wavy' hull in quartering bow waves - it would make me drink more to try and anticipate the hulls response while heeled at various angles - not to mention tacking and gibing - eash...

What was the question doctor...

SH.

[MikeJohns]

A lot of these theories come from air based hydrodynamics but dont wash when tried in fluids; Like the transsonic area rule which works in aircraft but when applied to a yacht hull by de-Saix (by waisting the hull amid ships) had no beneficial affect.
Various speeds heel angles, leeway angles and sea states make this sort of thing just idealistic in a displacement sea going vessel.

[seamonkey]

[quote=Tim B]I can see that roughening the surface finish would reduce drag (ask any Laser sailer) as it's all about the maintainence of the boundary layer,

Well,of course ,you're going to get a laser sailor who doesn't agree!Lasers,being semi-planing shapes,and relitevly light bounce around a lot,and continuously separate from the H2O medium-at least that's the desire!-so I don't agree with your statement,unless it's a very heavy laser which only sails as a displacement boat!!

[Tim B]

Seamonkey, you may be right, but I am not talking about adding a considerable amount of roughness. ie. do not try putting deck-grip on the underside, I am talking about fractions of a thousanth of an inch!!! It has also been proven to work on other sizes of yacht (and on powerboats).

Tim B.