If you are trying to run a planing hull or displacement hull resistance/powering analysis using Orca3D version 1.3.4 or later in Rhino 4, and you either receive an error message related to the drag library or nothing happens at all, then perform the following steps:

1. Download the attached replacement drag library for Rhino 4 to your computer. 

2. To use this replacement library file (HCDragPredLib4.dll) open your Windows Explorer and browse to your Orca3D installation folder. By default this is located at C:\Program Files (x86)\Orca3D on a 64-bit operating system or C:\Program Files\Orca3D on a 32-bit operating system. Inside that folder you will see an existing file named HCDragPredLib4.dll. Rename that file to HCDragPredLib4.dllbak and copy the replacement file in its place. 

3. Once you complete this step you will also need to download and install Visual Basic Powerpacks version 1.2. This can be downloaded from Microsoft at http://go.microsoft.com/fwlink/?LinkID=108166. 

After performing these two steps you should be able to run your drag prediction.