Re: [Flightgear-devel] Sailing Ships (was Re: Tides in FlightGear?)

[GWMobile <geo...@mi...>]

For craft at sea level over non land turbulence equations could be 
modified to create rythmic up down motion as well as "currents" from a 
direction.

If the frequency of the verticla turbulence shift is equal to the speed 
of the ship times 3 to 20 feet it should provide reasonable wave dip.

On Sat, 3 Jun 2006 7:57 am, Jeff Koppe wrote:
> As a long time Virtual Sailor user/idea contributor this thread caught 
> my attention (well... once it said "Sailing Ships..." in the subject). 
> In fact I've been toying with the idea of attempting to make my own 
> cross-platform sailing simulator for several years. I had thought about 
> using FG as a starting point but more recently I decided Delta3d would 
> suit my needs better. But then again I'm primarily a Perl programmer 
> and it's all vaporware at this point! If there is any movement in this 
> direction I'd be more than happy to help. I'd gladly convert any of my 
> Virtual Sailor boats for use and probably build anything needed. (See 
> www.static-lift.net for examples.) But I do think that wave action upon 
> a boat is THE key to a sailing/boating/ship simulator. Let's face it, 
> regardless of the motive power of the vessel (I too, had downloaded the 
> original Surprise program with the intent of porting it over to Linux), 
> moving up, down, across and through waves is the defining factor of ma
>  ritime travel.
>
> --jeff
>
>
>>  ----- Original Message -----
>>  From: "Steve Hosgood" <st...@ca...>
>>  To: geo...@mi..., "FlightGear developers discussions" 
>> <fli...@li...>
>>  Subject: Re: [Flightgear-devel] Sailing Ships (was Re: Tides in 
>> FlightGear?)
>>  Date: Fri, 02 Jun 2006 09:49:04 +0100
>>
>>
>>  GWMobile wrote:
>>
>>  > What about changing the aerodynamic computation so they take
>>  > place based on radius from the earth and at what would be sea
>>  > level change the air density to that of water.
>>  > Then any object below sealevel "flys under those equations. It
>>  > would allow for surface ships and submarines.
>>  >
>>  > And load in the whole terrain map of the world including all
>>  > bathespheric data
>>  >
>>  >
>>  >
>>
>>  I'd considered this, but I don't have the knowledge of hydraulics
>>  necessary to try and "parameterise" a ship's behaviour to suit (say)
>>  jsbsim. I think we'd need to spend some time running model hulls 
>> through
>>  water tanks or flumes if we were ever to gain that sort of data, and
>>  that means waiting until some Ph.D ship design students fancy getting
>>  into the project!
>>
>>  I'm thinking more modestly for now, i.e take Peter Davis's "surprise"
>>  FDM as a starting point. It doesn't handle any of the flotation 
>> aspects
>>  of a ship - just assumes the ship is at water level (which is OK until
>>  you want to try handling behaviour in waves). Davis's sim basically
>>  deals with thrust on sails up masts at various heights with yardarms 
>> set
>>  at given angles. Oh, and a rudder of course. It does consider heeling
>>  though, and in a true "FDM" for a ship I believe a heeled-over hull 
>> (as
>>  long as it is moving) is a significant contribution to being able to
>>  steer the thing. I've not dug in deep enough to see if Davis deals 
>> with
>>  heeling effects using real data or just fudge-factors.
>>
>>  Either way, I think it'll be OK for a starter.
>>
>>  FG's world model doesn't even need bathymetric data to start with.
>>  Basically you could get away with "if (ship within 50m of land) then
>>  you've run aground;" as a starting point. Worry about bathymetrics
>>  *after* getting the rest of it to work.
>>
>>  But you're right about submarines of course. They do fly in the water.
>>  Boats are the special case.
>>  Steve.
>>
>>
>>
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>>
>
>
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