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Sailing, anyone?

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Sailing, anyone?

Postby Kabuki » Sun Nov 28, 2010 12:10 am

I notice there's a sailboat in /Models/Geometry/sailboat1

I've never seen it, but it seems that it would be possible to make a working virtual sailboat, given that they are so similar to aircraft in how they work. Does that model react to the wind?

Anybody want to speculate on the feasability of making a working sailboat model, that can be operated like a real one, in flightgear?
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Re: Sailing, anyone?

Postby Hooray » Mon Nov 29, 2010 12:11 pm

Please don't send support requests by PM, instead post your questions on the forum so that all users can contribute and benefit
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Re: Sailing, anyone?

Postby DFaber » Tue Nov 30, 2010 7:43 am

Hi kabuki,

Anybody want to speculate on the feasability of making a working sailboat model, that can be operated like a real one, in flightgear?


I'm experimenting with YaSim Ships for quite a while now and I'd say it is possible. Right now my most advanced Ships are large engine powered ones like these:

Image

I already tested a sailing vessel too, but it requires some nasal to control the Sails. The Model itself reacts to wind, but reducing sail area or adjusting a sail to the wind is problematic without Nasal. I like to get a decent ship movement first, before I start on implementing Sails (the tests I made with hand controlled wind were big fun though!)

If there is someone here with nautic experiences and likes to lend a hand, give me a shout.

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Re: Sailing, anyone?

Postby Algernon » Tue Nov 30, 2010 10:02 am

I've got a fair amount of sailing experience on reasonably sized cabin vessels, I'd be happy to be involved in discussions about making it work - after all, most sailing principles are purely mathematical and so, in theory at least, could all be replicated.
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Re: Sailing, anyone?

Postby DFaber » Tue Nov 30, 2010 3:49 pm

Algernon wrote:I've got a fair amount of sailing experience on reasonably sized cabin vessels ...


Great to hear that! First thing to find out would be if my ships handle like ships or whatever. I'm going to prepare some for testing.

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Re: Sailing, anyone?

Postby Kabuki » Tue Nov 30, 2010 6:47 pm

The idea came to me from contemplating that a sail is a wing. It works exactly like a wing. I've also noticed that different ground surfaces have properties such as 'adhesion'.

Reading some of the posts in hooray's link, there's a realism problem with waves. Not just the chop, or the slower swells that move a vessel up and down, but especially the bow wave that's generated and changes when a sailboat heels with the wind.

I think a simple borderline-realistic sailboat would be fairly easy for an experienced a/c developer (which I am not). Getting one to handle realistically is always the challenge with any kind of virtual physics.

There's also an issue with the pure fun aspect. A sailboat would be more like an airliner than a warbird. More cereberal than reactive -- because things just don't happen all that fast on a sailboat, usually.

Still, there's a similar appeal in aircraft and sailboats to me, because of the way they work with air. I've more experience at the tiller of a sailboat than the yoke of an airplane, but there's still that amazing feeling of being able to feel the wind. In a sailboat, it's you engine of course. And there's a lot of horsepower in a good breeze.
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Re: Sailing, anyone?

Postby Hooray » Tue Nov 30, 2010 8:58 pm

It would probably not be too complicated to simulate a very simple model, for example there is an online sailing simulator purely implemented in flash: http://www.thepirateking.com/ships/sail_simulator.htm

It would probably be a good idea to look into other OSS projects that are in one way or another related to simulating ships, for instance see: http://bridgecommand.co.uk/

EDIT: I did a quick search, there is a fair bit of info available on the maths involved in sailing specifically. For example, see: http://www.oceansail.co.uk/Articles/Maths.html or http://terrytao.wordpress.com/2009/03/2 ... -the-wind/

Also, there are a handful of open source tools available for sailing related CAD, such as for example: http://sourceforge.net/projects/sailcut/

Image


Looking at http://www.angelfire.com/space/proto57/sailsims.html there is apparently an increasing number of proprietary sailing simulators available, and it seems this could be very well replicated in the FlightGear "world".

FWIW, during my quick search, I couldn't find a single open source sailing simulator, let alone multi-platform.
And this is actually confirmed by this discussion from August 2010: http://ftp.uktrainsim.com/viewtopic.php?f=275&t=108752
These folks specifically mention FlightGear, too.

This could be an interesting opportunity for FlightGear actually.
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Re: Sailing, anyone?

Postby Algernon » Tue Nov 30, 2010 10:45 pm

I would imagine it's not the aerodynamics that would be hard to implement, but the hydrodynamics - I know there are a number of seaplanes and flying boats in FG, but I'd imagine the attention paid to their handling in the water is probably minimal... but I don't know this.

To accurately model sailing, you need to model the counteracting forces on different points of sailing: for instance, when sailing close-hauled - when the sail is pulled right in because you're sailing into the wind - forward motion comes from the lift generated by the sail counteracting with the fin or keel sideways. When sailing free - with the wind aft - the wind is pushing the boat along and the handling characteristics are totally different. So you need realism in both the air AND the water.
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Re: Sailing, anyone?

Postby someguy » Wed Dec 01, 2010 5:16 am

It might be simpler to model an iceboat or landsailer. Lakes in fg are frozen in winter, and salt flats are great for landsailing. The sail handling is just the same as a sailboat, but no worries about hydro effects. Nice and speedy, too, with the opportunity for MP races.
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Re: Sailing, anyone?

Postby Arthur Maiden » Wed Dec 01, 2010 10:14 pm

that and if we introduced Sailboats, we might have to schedule tides, and their effects on boats, although it wouldnt be much more difficult than the winds...

if anyone has questions about in-depth areas of sailing, then i could tell you or point you in the right direction...
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Re: Sailing, anyone?

Postby Crashpilot » Mon Dec 20, 2010 1:21 am

Well, Flightgear over time changed to GearGear or GearSim or SimGear (wait a second...) anyways. Though it focuses on aviation, the border became eroded over time: Pushback, snowplow, carrier, cars, trucks, wheelchairs, AI ships...

As far as I can tell, the intersection between nautics and aviation are huge, just the emphasis are somewhat different. Seaplanes would profit from tidal simulation, waves and a simple hydro physics for sure, while nNautics need all the stuff a flightsim needs: Descent weather, graphics with large view distance including mist and fog, night and day change, support for realistic light buoys etc... Flightgear has it yet.

Thorsten is developing a very promissing local weather system with fog banks - who doesn't have an association with nautics?

So I am positive that descent support for ships will come sooner or later.

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Re: Sailing, anyone?

Postby Crashpilot » Mon Dec 20, 2010 1:33 am

Algernon wrote:when sailing close-hauled - when the sail is pulled right in because you're sailing into the wind - forward motion comes from the lift generated by the sail counteracting with the fin or keel sideways.


True. In fact, you can consider a drop keel or centerboard as a wing, too. It can even stall. And, btw, to the rudder applies the same.

Ever noticed how easy the wind can push your yacht sidewards when you are not having speed? Gain 2 knots speed by engine and the yacht is like on rails: Keel and rudder are in flow again...

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Re: Sailing, anyone?

Postby DFaber » Mon Dec 20, 2010 7:38 pm

Hello Sailors,

here is my current attempt to create a Ship:

http://www.sol2500.net/flightgear/files/Ships.zip

The Archive contains a Liberty Class Freighter (which is the most advanced) and a PT-Boat (not so advanced). Please test and comment.

Warning: This Work is in early stages, and meant as a Proof of Concept. Don't expect too much.

Greetings
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Re: Sailing, anyone?

Postby saturn5 » Fri Dec 31, 2010 9:50 pm

Thanks for working on this, great to have ships!
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Re: Sailing, anyone?

Postby Algernon » Sun Jan 02, 2011 2:45 pm

I'll check this out shortly, Detlef, now the end-of-year festivities are over and I can set up my cockpit again :)
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