Profili 2.30b | 25 MB

Profili is a software developed to help the 'do it yourself' modellers. Profili has a database of more than 2,200 airfoils with precomputed aerodynamic characteristics, which really saves time in making airfoil comparisons. The user's ability to easily change the airfoils slightly (or even extremely) has been made effortless. The program will then compute the new aerodynamics resulting from your changes. It is interesting to watch the computations take place; you gain a "feel" for how the pressures are distributed over and under the airfoil.

Once you input your pet airfoil, Profili goes to work. Depending on the complexity of the airfoil (maybe something exotic such as a double diamond shape with a square leading edge and ripples across the bottom), it may look as if it's locked up. Normally this is because Xfoil is having trouble with the pointy edges of your pride and joy. This is not a failure in Xfoil or Profili; there are just limits to what is possible with computational fluid dynamics.

To help manage this, Profili has an adjustable time-out function to keep things moving. When you try to design the world's most marvelous airfoil, keep in mind that nature prefers smoothness and will reward a finesse approach to airfoil design.

You might have heard the local theorists at the flying field discuss Reynolds numbers (Re). Profili will compute Re for you when you input your projected flight speed and model size. The accompanying screen shots are examples of selecting a particular airfoil, in this case an HQ 3.0/15, and calculating the aerodynamic characteristics at different Res. One thing we noticed was that for the HQ airfoil, as well as many others, there is a lot of variation in drag coefficient (Cd) with Re. It is one of the reasons big models seem to fly better than small ones.