Prop Designer blog

I hear about problems with opening DAT files but I don’t know how big a problem it is. I have written a small program that associates whatever program your system uses to open TXT files with DAT files. If anybody wants such a program I may add it to the library site or I could add a set of instructions for changing the file association. I know sometimes other programs use the DAT file extension for their own use so opening a DAT file can either show rubbish or at least text that is not in the desired format.

There must be some more exiting or at least more relevant to human powered flight to write about!

Because of the way Windows works, do people have problems opening DAT files? DAT files are just text files and are of the type .txt but the file extension is just renamed to .dat. I might do something about it and write a small program that adds the file association.

The quickest way to fix the problem is to right click on a .dat file in Exporer and select Properties. You can then alter the file association to Note Pad or another program that will edit text files. Be careful when saving the file that it is in text format and not some other format if you open it in Word Pad or your favorite word processor.

I am in discussions with certain people about the accuracy of the data in the DAT library. This is a section that concerns me as the data is mainly collected off the internet and it’s quality is unknown. So far I have not got any data that looks wrong to me but that is not quite the same as it is right.

I then use the DAT file to generate the page banners and use JavaFoil to generate the plots of lift against drag as well as the lift against angle and pitching moment, all information that helps to identify suitable aerofoils. If you choose to use a different program to generate these plots then you tend to end up with slightly different plots. This is a result of how they calculate the pressure and speed over the aerofoil and the results should be taken as close to what will happen in reality.

You will notice the results are for Reynolds numbers of 200,000 and above because below this value you tend to get laminar separation bubbles which the programs cannot cope with. Xfoil and so by extension XFLR5 and QFLR5 can indicade is present but even this program underestimates it’s effect.