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[NFMike]

Has anyone ever made a model boat/ship (displacement vessel, not planer) that had a reasonably realistic wake and/or bow wave?
If so, how?

It's one of those things that doesn't scale properly - presumably because the water is still at 12" to the foot scale. It was always the curse of those old war films sfx models - along with the shells exploding in the water - so I was wondering if there'd been any development since then.

[Andyn]

I was wondering if there'd been any development since then.

Nope sorry, water is still water

[Norseman]

water is still water

but if you really wanted to change the wake on a generic tanker for example, and then considered it at the design stage, is there nothing that can be achieved at all?

Dave

[Artistmike]

Here you go .... solar.physics.montana.edu/dana/ship_wake.pdf ....

[dodgy geezer]

Has anyone ever made a model boat/ship (displacement vessel, not planer) that had a reasonably realistic wake and/or bow wave?
If so, how?

The usual way, as managed by films, is to make the boat to a very large scale - 20 ft or more, and then use water jets mounted inside the bow spraying water upwards...

[malcolmfrary]

The wave shapes will be correct.  The texture will appear different because the component parts (bubbles) will be the same size.  Something to do with the surface tension of the scale water being the same as that of the full scale water.

[Andyn]

but if you really wanted to change the wake on a generic tanker for example, and then considered it at the design stage, is there nothing that can be achieved at all?

You can change the hull shape to provide whatever effect of wake you like, but it'll never have the same look as a real ship, the water isn't travelling very far and will always appear to move too fast, and it'll never bubble the same way a real one does...

[Martin (Admin)]

 it will look correct at the inverses scale speed and viewing distance!  

[Arrow5]

Release of an effervescent agent might work, maybe with a touch of light blue/green dye added.  They used salt grains blown by fans to simulate spray and rain in storm scenes, effective if filmed against a black angled back-cloth which allowed some "sheets of rain or spray" to roll downwards realistically as well as the wind-blown suspended salt .

[derekwarner]

Thanks Artistmike  ....very interesting....however I must admit I got a little lost on page 3 as below


ˆu · ˆe (ˆkcr) = cos ® = sin µw = 1 3

 could you please explain why the expression sin µw is needed?  .....Derek

[Norseman]

Having less mathematical  capacity than even the lowest order of primate
I found this simple statment hilarious 'it is easy to verify ....' 
Cheers for that Mike.

Dave

[dreadnought72]

Something to do with the surface tension of the scale water being the same as that of the full scale water.

Yes - you'd need something with a very low surface tension.

Perfluorohexane is one good example. Handy, too, since you can't drown in it! 

But better still would be liquid helium near absolute zero. 

Andy

[dodgy geezer]

It would also help to drop g from 9.8 down to about 1....

[Bryan Young]

Hi. A very, very simple answer to your "problem".
The vast majority of scale "displacement" models are driven around at scale speeds that would equate to 60mph for a real ship.
(Watched a "Liberty" ship (max speed 11 knots) careering around the lake like a Club 500 the other day).
You will know the length of your prototype (?) and its service speed. From that you can easily work out how long it takes the real ship to travel its own length. Transfer all that to the model. More realistic results. QED. BY.

[Netleyned]

Thats why the most realistic models
wakewise are well driven tugs and lifeboats where
the builder is striving for realism.

Ned

[NFMike]

Well, thankyou for all the answers and comedy. Very helpful - one or two anyway :)

If anyone wants a somewhat more readable article about wakes I stumbled on this one while looking around before starting this thread. It is actually aimed at diorama modellers but is written by an (ex?) US Navy engineer, so has some authority - and no maths :)
http://www.steelnavy.com/WavePatterns.htm

[malcolmfrary]

Artistmike's link describes in mathematical terms the size and shape of the waves, which are what we do get when driving a scale boat at scale speed and is almost certainly spot on.  It doesn't mention the fractal bits of foam which I suspect are what the OP wants.  The only way to get that effect is to build to a scale of 1:1, when it all works out.

[Arrow5]

I was thinking in my earlier post about the propeller wake, frothing bubbles etc., not the waves produced from the bow. Any thoughts on that effect ?

[NFMike]

I was thinking in my earlier post about the propeller wake, frothing bubbles etc., not the waves produced from the bow.

Yes, it was actually the froth from bow and stern and the trail left astern which I had in mind when originally posting. As is clear from the articles linked even a model boat produces the correct waves - the problem is they don't break and thus create froth.