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Richard64

CX Thermal Lean factor

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Hi Peter, will you answer a question for me.

In the CX Users Manual you state that a value of zero produces a purely vertical thermal while a value of 1 produces a leaning effect etc.

Does this mean that a value in between these 2 values will give a corresponding effect i.e if I entered a value of 0.5 would this have the effect of producing half the leaning effect of the value of 1.

Hope you understand what I mean.

Regards

Richard

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Hi Richard,

you are correct. The value of "1" results in a leaning angle which corresponds to a vector addition of wind speed and updraft. If the value is less than 1 the column becomes more vertical. You can even increase up to 3.0, however values over 1 are not realistic and provided for backwards compatibility with CCS2004. (BTW, CCS2004 definition is inverse, see CumulusX! appendix on thermal script files on that).

Currently vertical wind profile is not considered and wind is taken only at the aircraft for determining actual leaning. This leads to some compromises if there is a strong vertical dependency or wind at the aircraft is unsteady. The physically correct solution of sampling the whole vertical profile seems to be too FPS-consuming at the moment. The next CumulusX! release (available soon) will improve here somewhat.

best regards,

Peter

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Hi Peter and many thanks.

Can I please ask another question and that is am I right in thinking that temperature and dewpoint settings in FSX have no influence on how CX behaves?

Looking forward to the new version of CX.

Regards

Richard

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Hi Richard,

that is correct again, by no doubt. There was a first idea, to derive actual thermal conditions, including cloud ceiling from FSX' detailed weather data. Unfortunately, most of the time the data is insufficient, incomplete or even inconsistent. This means that FSX weather appearence is frequently not in coincidence with FSX! internal weather data.

The main philosophy of CumulusX!' thermal creation is consistency with the visible weather phenomena of FSX.

Another reason, not to follow it in full detail, is that it would be almost impossible to a commonly educated user, to create a desired thermal situation on purpose.

best regards,

Peter

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Many thanks Peter, the reason I am asking these questions is that I am trying to replicate as closely as possible real world weather with data collected from weather sites such as SkyLinkWeather.

One problem I have is trying to determine thermal strength from the data I collect.

I have found several formula for calculating this and they work, however when I enter the thermal strength in CX it is very weak and almost impossible to use.

For example one calculation gave a thermal strength as being 2 meters per second but this entered into CX was totally insufficient and I had to increase it to 3.5mps to have any chance of success and then only with a diameter of 1000m to 1400m.

And sorry, another question.

If I have determined that the cu cloudbase is say, 4000ft (1219 meters)and this is set in FSX, how do you enter that figure in CX.?

Is that the minimum lift height that you would enter and if so what do you enter the maximum as?

Regards

Richard

PS added later.

Peter I have just realised that the lift height question has been asked before.

However if I have set a cloud base in FSX what should I put in CX.

Sorry bit confused over what you should enter if CX picks up information from FSX.

PPS, FSX settings are imperial and CX is metric so I guess as long as you make the conversion that's ok, but is it possible to change CX to imperial.

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For example one calculation gave a thermal strength as being 2 meters per second but this entered into CX was totally insufficient and I had to increase it to 3.5mps to have any chance of success and then only with a diameter of 1000m to 1400m.

If I have determined that the cu cloudbase is say, 4000ft (1219 meters)and this is set in FSX, how do you enter that figure in CX.?

PPS, FSX settings are imperial and CX is metric so I guess as long as you make the conversion that's ok, but is it possible to change CX to imperial.

Hi Richard,

For getting some idea of the useful lift you should subtract 1 m/s from metereoligical lift for the glider's own sink during banking. You should also account for the bell-shaped lift profile. The 2 m/s apply in the center of the lift. At the diameter where you circle it will be less. I think the metereological formula gives a sort of average over the column. So 2 m/s lift is really not very much.

If the lowest cloud layer in FSX is cumulus, then it's ceiling overrides the ceiling in CumulusX!. The ceiling there is only relevant for blue thermals. You can define a range to get variations very three hours.

Forgive me, if I concentrate on functionality and leave metric-imperial conversion to the educated user.

best regards,

Peter

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OK many thanks Peter.

The imperial to metric conversion is no big deal. I have made myself a small spreadsheet to do this.

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Hi Peter, me again.

We have talked about the ceiling height and the part that the level set in FSX plays in Cumulus X.

However although we add a Cu BASE level in FSX what determines the TOP level.

Are there any rules governing this or can we enter any figure we choose?

Regards

Richard

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However although we add a Cu BASE level in FSX what determines the TOP level.

Hi Richard,

the two numbers in the CumulusX! control panel, Min and Max height, refer both to the thermal ceiling, and only in the case when there is no cumulus layer in FSX. CumulusX! then makes a random choice for the lift ceiling in between of the two numbers. The thickness of te cloud layer thickness is given by the graphical cloud model and cannot be altered during runtime.

best regards, Peter

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