XFLR5 update

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Aerowerx

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For those of you that use XFLR5, there is a new version 6.4.4, updated yesterday, which allegedly includes aircraft stability analysis.

Haven't played with it yet, so I don't know its capabilities.

Note that if you go to source forge and click on "down load latest" you will not get v6.4.4. (at until source forge does an update). Instead go to "files" and download it from there.
 

fly2kads

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From what I have seen so far, the stability analysis appears to have a couple of limitations: no evaluation of stick-free conditions; and it does not include any effects of power. Those limitations make perfect sense in the context of R/C model sailplanes, for which XFLR5 was developed, but makes for an incomplete solution for man-carrying, powered aircraft.
 

Aerowerx

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I have played with it a little bit, but don't see much difference with older versions.

Maybe I misread the announcement.

At least I assume he fixed a bunch of the bugs the older versions were plagued with. Unless you did everything exactly right, the older version I had kept crashing.
 

Aerowerx

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From what I have seen so far, the stability analysis appears to have a couple of limitations: no evaluation of stick-free conditions; and it does not include any effects of power.
True, but you can do a static analysis with different air speeds. This will give you some idea.

Those limitations make perfect sense in the context of R/C model sailplanes, for which XFLR5 was developed, but makes for an incomplete solution for man-carrying, powered aircraft.
Again true, but it is a good start.
 

Topaz

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...Again true, but it is a good start.
Since propellers are either stabilizing or destabilizing, depending on whether they're pusher or tractor props, power effects cannot simply be dismissed. And effects of the propwash of a tractor prop need to be accounted for as well.

For the time being, at least, it would seem this tool is only useful for sailplanes.
 

mcrae0104

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Comic Sans in a technical document? Oh, the humanity!

Sorry I can't comment on XFLR5, as I haven't used it.
 

mcrae0104

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That is not a technical document, but a slide show converted to a PDF. Originally used in a presentation.
Sure, I get it. Not a textbook. No quarrel with that. But, as it has been said, "the medium is the message." I'll step off my soapbox now so actual discussion of XFLR5 can continue... :)
 

ScaleBirdsPaul

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I’ve used XFLR5 quite a bit. I use it primarily as a GUI for XFOIL, however I use the wing analysis portion quite a bit. It’s the simplest program I’ve found to look at a 3-D wing in the early stages to get lift curves, pitching moments, and load distributions. I haven’t used the stability analysis much so no real opinions there.

I’d only use it for very early rough numbers. There’s a PDF related to the latest update that discusses some of the shortcomings, and it is even more inaccurate than I thought, especially outside the nonlinear part of the lift curve. I used to think that it could predict the spanwise location where stall begins based on where it would fail to find a CL solution. Turns out this is not true. I’ll see if I can find the PDF, but the gist was the rectangles used in the panel simulation don’t handle curvature in multiple planes well. Supposedly future versions will use triangles to fix this.
 

ScaleBirdsPaul

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From what I have seen it seems to be pretty close to where theory says the stall should start.
I found it very sensitive to how the wing was modeled. If you modeled the wing as one “section” with 50 spanwise panels you would get very different results (where stall would start) than 5 sections with 10 panels each, all else being equal. I didn’t like that.
 

Aerowerx

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I found it very sensitive to how the wing was modeled. If you modeled the wing as one “section” with 50 spanwise panels you would get very different results (where stall would start) than 5 sections with 10 panels each, all else being equal. I didn’t like that.
Why is there no "cancel" when replying to a post?

I was going to say something but lost my thought. (drove to my sister's today, and drove back. Also had a sip of wine this evening.)
 
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