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FloatGear: Skipjack Kathryn...

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Re: FloatGear: Skipjack Kathryn...

Postby S&J » Sat Sep 24, 2022 7:44 pm

Are you using the coefficients I sent you ?
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Re: FloatGear: Skipjack Kathryn...

Postby Kugelfang » Mon Sep 26, 2022 7:34 pm

No, I'm not yet using the coefficients. Baby-step development workflow.

But I have successfully moved sail thrust and heel to external forces. I'm much happier with the performance now. Just spent a couple of hours cruising the Choptank river in Maryland with the wind blowing from the north. Couldn't do that previously.

Image

I want to get leeway and yaw implemented next and if all goes as planned then I'll start tweaking the values and implementing 'proper' physics.
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Re: FloatGear: Skipjack Kathryn...

Postby TheEagle » Mon Sep 26, 2022 7:42 pm

Seeing the increasing number of boats for FG, we really ought to add normal ports to the airport database ! :mrgreen:
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Re: FloatGear: Skipjack Kathryn...

Postby S&J » Tue Sep 27, 2022 2:13 pm

Kugelfang wrote in Mon Sep 26, 2022 7:34 pm:No, I'm not yet using the coefficients. Baby-step development workflow.
.


The equation for lift and drag is actually very simple and identical (almost) to those used on planes.

The Left Drag values are a multiplication of sail area (ft), a value you provide, dynamic pressure which exists as a jsbsim property and the co-efficient result from the table data based on beta angle, plus (which is the difference) a value between 0 and 1 for percentage sail raised.

The hard(ish) problem is to understand the beta angle as this is a pythagoras result based on the current wind direction and current facing direction and angle of sail 'let out'
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Re: FloatGear: Skipjack Kathryn...

Postby Thorsten » Tue Sep 27, 2022 4:53 pm

I want to get leeway and yaw implemented next and if all goes as planned then I'll start tweaking the values and implementing 'proper' physics.


Generally you'll have a much easier life implementing proper physics first and then fine-tuning things.

That'd be because nature usually does proper physics (for some reason, it's really good at that). :mrgreen:

The equation for lift and drag is actually very simple and identical (almost) to those used on planes.


Actually physics doesn't know and doesn't care whether an object is an airplane, a ship or a tree - so naturally the equations are always the same regardless of the object.
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Re: FloatGear: Skipjack Kathryn...

Postby Kugelfang » Mon Oct 31, 2022 9:44 pm

I'm surprised I've been working on this for only three months. Seems like forever....

Nevertheless, I'd love to get some feedback on the Kathryn. Download at https://github.com/alberto1901/Kathryn.

Being a non-sailor, non-engineer with few specifications and absolutely no performance data, I'd really be interested in hearing others' opinions on performance. Especially if you have sailing experience! There's no engine. Don't even look for one.

I'm aware of:

1) a couple of minor graphics issues
2) she likes to yaw--you have to constantly adjust the rudder (or the sail trim, or the sail deployment) to maintain a straight course. It's a matter of balancing forces!
3) rudder seems inefficient at low speeds and too efficient at higher speeds
4) I still need to implement keel forces and the centerboard which should dampen down the tendency to yaw
5) Seems like reaction to anything other than smooth water (i.e., wave amplitude greater than 0) is very, very, um ... robust

Also, my joystick seems to be in a coma so I've done all the development using keyboard controls: Arrow keys control the rudder; Del/End trim the sails; PgUp/PgDn Furl/Unfurl the sails. Shift-P brings up the panel with the compass and course indicators. Key controls are explained in the help file (press '?').

Many thanks in advance.

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Re: FloatGear: Skipjack Kathryn...

Postby S&J » Mon Oct 31, 2022 10:43 pm

We are so going to have some fun with this :)

thank you very much
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Re: FloatGear: Skipjack Kathryn...

Postby Kugelfang » Thu Nov 03, 2022 11:04 am

S&J wrote in Mon Oct 31, 2022 10:43 pm:We are so going to have some fun with this :)

thank you very much


I've had a lot of fun working on it!

BTW, is there a way to explicitly give focus to the main window? I've found that in both of the boats I've developed the user has to click on the main window before fgfs accepts any keyboard or mouse events. I suspect what is happening (but have no idea how to test) is that the non-displayed Canvas panel is actually holding the focus.

TIA
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Re: FloatGear: Skipjack Kathryn...

Postby TheEagle » Thu Nov 03, 2022 2:34 pm

Indeed, the Canvas window takes focus from the main window which isn't needed for a panel like that - add:
Code: Select all
allowfocus: 0

to the argument list of the window constructor call ! :) (You need to make all other arguments keyword arguments, too)
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Re: FloatGear: Skipjack Kathryn...

Postby S&J » Fri Nov 04, 2022 11:09 am

Kugelfang wrote in Thu Nov 03, 2022 11:04 am:
I've had a lot of fun working on it!



Now it seems I've got to learn how to sail
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Re: FloatGear: Skipjack Kathryn...

Postby Kugelfang » Fri Nov 04, 2022 11:54 am

@TheEagle, thanks.

TheEagle wrote in Thu Nov 03, 2022 2:34 pm:I... add:
Code: Select all
allowfocus: 0


Allowfocus:0 didn't seem to work but I found that adding '.clearFocus();' did. Issue fixed.

S&J wrote in Fri Nov 04, 2022 11:09 am:
Now it seems I've got to learn how to sail


That makes two of us! (which probably says something about the accuracy of the FDM!)
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Re: FloatGear: Skipjack Kathryn...

Postby S&J » Fri Nov 04, 2022 1:10 pm

Sorry but I'm not using your fdm, so can't comment on it's accuracy

What I needed was your GUI as a start point from which to mod to the FDM I have for Australia II.

I must say your GUI has been a great help.
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Re: FloatGear: Skipjack Kathryn...

Postby Kugelfang » Sun Nov 06, 2022 1:36 pm

Glad to hear it. That's the great thing about open source!
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Re: FloatGear: Skipjack Kathryn...

Postby S&J » Sun Nov 06, 2022 1:46 pm

Sharing, modifying and distributing.
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