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CumulusX, Ridge Lift and Thermals


VulcanB2

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Hi,

I'm new to serious FS gliding, although I have got about 50 hours in the real thing (K-13 mainly).

I haven't looked too closely at the settings yet for CumulusX, but I just tried some ridge soaring in the Aerosoft Discus BM and so far, very pleased!!

My main query is to do with ridge lift/sink. I set an 18 kt wind from 270, putting the wind the far side of the mountains in HawaiiX (by MegaScenery).

The lift was about what I expected, but the sink seemed rather aggressive. At certain points, even though I was over the peak, on the up-wind side, I was in quite strong sink and had to fly quickly back into the lift. Is this a limitation, or to do with the settings?

It's like the point where Cumulus detects the top of the ridge, however steep the upwind side is, it assumes it is equally steep immediately behind it, but at a point immediately over the top of the ridge.

Instead of /-\ it is more like /\.

Are there any suggestions/recommendations for more realistic settings than the default?

With respect to the Discus BM particularly (or just the B ), what should I set the Slope lift and sink factors to? The default has them both at 1.0.

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Regarding auto-thermal generation, does it automatically take cloud ceiling as set via FS Weather menu into account when generating thermals?

In the settings, you can set a max/min ceiling for thermals, but it is unclear whether thermals can terminate lower than the cloud base unless reset for the current conditions?

Thanks!!

Best regards,

Robin.

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For ridgelift, the with the wind left-to-right, here's a display of what CumulusX calculates (red=lift, blue=sink):

cx_ridgelift.jpg

Sink is not dependent upon the forward-facing slope, but only on the steepness of the backslope.

Are there any suggestions/recommendations for more realistic settings than the default?

My suggestion is do a bit more flying first. Note if you fly missions, these will probably use close to the default settings and they're not as far adrift as you suspect.

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Regarding auto-thermal generation, does it automatically take cloud ceiling as set via FS Weather menu into account when generating thermals?

Yes, if there is a Cu layer.

In the settings, you can set a max/min ceiling for thermals, but it is unclear whether thermals can terminate lower than the cloud base unless reset for the current conditions?

This is a bit more complex - CumulusX will use its *own* max/min range for thermals if there is no Cu layer at the position of the user aircraft, otherwise it will use the cloudbase value from FSX. *Sometimes* FSX will report that there is no Cu layer even though the user settings are that there should be, so it can be a bit confusing with 'blue' thermals even though you can see some wispy Cu's...

B21

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Couldn't have explained better,

With respect to the Discus BM particularly (or just the B ), what should I set the Slope lift and sink factors to? The default has them both at 1.0.

The slope lift factors are only used in CCS compatibility mode, to support joined sessions with FS9/CCS2004 and are almost deprecated. The sink factor controls the surrounding sink of a thermal. Leave them as they are.

Cheers,

Peter

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Looking at the diagram again, Peter, can you verify Wave lift? Is Wave shown somewhat in the 4-5 position and what determines whether or not a Wave cloud appears over this spot in real life? Could it be simulated?

Once in a while I'll swear I get some sort of lift on the back side of a ridge between ridges at a higher elevation.

Scott

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Hi,

Once in a while I'll swear I get some sort of lift on the back side of a ridge between ridges at a higher elevation.

I noticed this, too. I can't decide if I'm simply feeling the effect of rising air over the smaller ridges, but it seems to have an effect at a much greater altitude.

Is this flow really from the larger ridges that I'm downwind of?

It is particularly noticeable when flying around 2 nm to the west of the eastern most mountains on Hawaii, at about 3,000 ft (set a 20 kts wind from 080).

Best regards,

Robin.

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