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fergusdog

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Hi Peter & Ian

I just tried cumulusX! and sim_probe and love the combo. To me this is one of the most ingenious add-ons for FSX - even for non-gliders. :yahoo:

To quickly introduce myself, Im quite involved in the FS scene, have a reputation as a scenery designer (http://www.simpilotexperience.com) and also run a free online magazine (http://www.simpilotnet.com).

I would love to take this add-on to the next level. There are more wind effects (maybe not just gliding related) like coastal winds. I'm wondering if you would be interested in developing your programs into a new kind of weather add-on which makes atmospheric modelling in FSX much more realistic. I got some ideas and contacts that would help pull it of, so I just want to check how you guys feel about that...

Another question, I ran sim_probe on my 20m New Zealand mesh and found that the lift wasn't as strong compared to FSX missions or FS2004 CCS. I was above quite a steep mountain side with 20 knots crosswinds and got lift about +4 max. This meant that I would only get lift at about 70 knots in the glider, so I couldn't really develop any good speed. Is this what I should expect?

Cheers,

Christian

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Hi Christia,

thanks for the compliments. Regarding future development, a lot of things could be possible, but to be honest, the RL gliding season is to start now, and I have spent really quite some time the last six months. So, my number one priority is driving CumulusX! to its full release 1.0 in the next weeks and manualling. Perhaps there will be a few minor improvements during the rest of the year.

In parallel, I will consider the outline of a potential version 2.0, which will most probably include wave lift, because I have already a first theory how this could go. Coastal winds (things like convergence I think?) were not on my radar so far and I do not have a good idea yet, how this could be put together by the limited view of a simulation program.

Regarding your experience with the lift strength, we had already some discussion here. One outcome was, that CCS2004 usually overemphasizes flat slopes and has approximately 15% more lift than windspeed at a vertical slope.

Of course the ridge lift of FSX missions are purely artificial, since you can easily design a mission with ridge lift twice as much as windspeed.

On the other side, both Sim_Probe and CumulusX! with slope data base are aiming at a reasonable simulation of ridge lift, based on (very) simple physical models, which may result in an experience, that is sometimes less exciting, but more realistic. What we would like very much, is collecting feedback from RL experience, to get some calibration data to fine tune these models.

best regards,

Peter

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Ridge lift in the default Austrian Soaring mission is extremely, unrealistically, strong. I wrote the follow-on Austrian Soaring Days 2,3 & 4 missions and toned down the lift a bit in those. The ridgelift boxes in the FSX mission editor give you *contant* lift throughout the box (more-or-less). For what it's worth I wrote the only tutorial I'm aware of for using RidgeLift elements in a mission (here) so there's some small vestige of credibility (but not much). The FSX default Austrian Soaring mission just planted a couple of *huge* ridgelift boxes all along the main slopes used in the mission, while my follow-on missions have maybe sixty smaller boxes aligned to the slopes for a more granular ridge lift implementation.

You *are* right - FSX default ridge lift (and thermals) are stronger than sim_probe and CumulusX!, but frankly you could fly a plank in that lift, but the difference isn't as great as you might think. The problem is FSX default gives you the same very strong ridge lift even if you're very high up above the ridge, or often way out into the valley in front of it, and in those situations you'll get very little from sim_probe.

Note that sim_probe is calculating the lift based on a relatively detailed slope analysis of what is around you. The lift is consequently finely detailed, varying every second, and you have to seek out the steepest part of the slopes. In a 20-knot wind it's not that hard to find 10+ knots of uplift. Note that the numbers displayed in the sim_probe console window or in the CumulusX! debug window are *meters-per-second*, so times 2 to get knots.

Note also the sim_probe approach is ruthless about the angle of the wind relative to the slope. The ridge lift will be strongest if the wind is perfectly perpendicular to the *local* section of ridge your on, but anything else will decrease the lift from the maximum.

Most of all, sim_probe is looking carefully at how tucked into the slope you are, i.e. an analysis based on your altitude AGL and the slope upwind and downwind of your aircraft. If you're flying along a typical ridge, it makes a *big* difference if you get down to ridgetop or below.

What this means is if there was a race with significant ridge-running involved (e.g. out of Ridge Soaring Gliderport in Pennsylvania, USA) you would *really* have to optimise your flying to win the race - follow the contours of the ridge, stay at the right altitude for the conditions, and fly at the right speed *at every point*.

So almost every characteristic of sim_probe lift is *very* different from the single 8-kilometer-long fixed-lift ridgebox that FSX places in the Austrian Soaring Mission, even though that has a lift strength of maybe 12 knots regardless of altitude or local slope direction...

For what it's worth I now fly with a modified left (Cambridge) vario giving me netto lift. Even though Peter did a great job making the right vario total-energy, it's very difficult to know what ridge lift you're in from just a TE reading (although that's a *huge* improvement on the default FSX uncompensated vario). The netto version isn't that much more complicated - I just add back in a polar lift value to his TE value with some basic linear interpolation code from five or six polar points for the DG808S.

Ian

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Thanks for your reply Peter. I realise the commitment, I'm a scenery designer myself. I'm simply thinking out loud, because I'd love to have much more realistic atmospheric modelling in FS. In regards to the coasts I have some ideas on how to do that (ie check the landcover below).

I'm simply wondering if you'd be open to creating a team and bringing in some other talent (not saying I know of people who want to contribute, but I know a few people who may be interested). Not trying to step on your toes, I simply love your add-on and see some future potential that no one ever has even considered so far...

Cheers,

Christian

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Sorry Ian. I didn't mean to put your work down, in fact I believe it's really original, I thought about this problem myself and one of the first things in simconnect I was checking was if it gives access to the mesh. I had a chat about that with a developer from Aces, so when I saw your work around I was impressed!

I know that the MS box system is terrible. I was simply surprised how little lift I got on a steep mountain side with 15-20 knts crosswind (as I wrote above it was between +2 and +4). This may very well be realistic, I have to admit I know nothing about real world gliding so this was just a question. Being very ignorant I assumed there were 3 possibilities:

a) What I saw is realistic

B) I don't know how to propely get maximum lift (I tried several spots across the ridge for about 30 min)

c) New Zealand is an extreme case with very steep slopes and my 20m mesh is really quite detailed. Maybe sim_probe can't quite cope with that environment (again, not trying to put your work down, it's excellent)

BTW, the spot I picked was around Omarama, quite a famous gliding spot...

Here's an idea. Given that I don't know what I'm doing, I'd be happy to send you a (free) CD of the NZ mesh (it's $70 payware) and you could test sim_probe in an extreme environment. Plus, you get to glide in some stunning scenery...

Cheers,

Christian

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blimey Christian - that's a generous offer. Before I take you up on it I am happy to test out the location you're talking about - give me a lat/long/altitude plus a wind direction and strength and I'll fly around there (or.... attach a FLT file and I'll fly that!). The default FSX mesh can only smooooth out the slopes in a more detailed add-on mesh, which means the lift is nearly always *less* with the default mesh rather than more (but the differences are neglible compared to the other things going on in general - maybe not at the top of Mount Cook though).

And please relax - I haven't taken *anything* you've said as any kind of criticism.

Given the way sim_probe works it is equally happy with add-on or default meshes so I don't think there's an issue there.

Where did you read the "4 knots lift"? Either the CumulusX! debug window, or the sim_probe console window, are the most reliable sources of the sim_probe ridge lift factor, which will be in meters/second.

With a 20knot cross-wind, it should be *normal* to find sim_probe ridge lift of 4-5 meters per second, i.e. 8-10 knots. Given a steep enough slope aligned to the wind you can do a smidgen better than that.

Here's my home-built netto vario:

post-11043-1213799879_thumb.jpg

This *overwrites* the panel.cfg in SimObjects\Aircraft\DG808S\panel, but I've included a copy of panel.cfg.cumulusx to make it easy to copy that back if you want it. That is the *only* file that is overwritten (otherwise the zip just installs a new gauge) so make your own backup if you're nervous.

Ian

b21_vario_netto.zip

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Thanks Ian

Don't have lat/lon here, but if you go to the Omarama gliding strip NZOA, then fly North to Lake Ohau (fairly big lake, you can't miss it) and then fly along the ridges. I tried the east ridge with a westerly around 20 knots, and was getting +2-4 m/s, probably average about 3 m/s.

Where did you read the "4 knots lift"?

I didn't ;) I used the console window, but wasn't sure what values to expect.

The complication I could see with a 20m mesh is that you have a lot more going on along the slope.

I'd be interested in your findings :)

Cheers,

Christian

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