The *.x3d files rendered by the website output each component as a single wireframe mesh. This corresponds to the wireframe shown on-screen in OpenVSP.
A normal vector is calculated at each node point that is used in the rendering process.
At sharp corners (wingtips), the normal vector should be multi-valued (one normal to the wingtip, another to the wing surface). Since the render doesn't know about the sharp corner, it creates a visual artifact.
In OpenVSP's native rendering, we split the mesh wherever sharp corners occur before calculating the normal vectors and sending it off to the graphics card for rendering. That way, we are actually visualizing two surfaces (with separate normal vectors) that happen to meet. This results in better rendering. That said, there are still some cases where OpenVSP's normal vectors get ugly and our rendering has some artifacts.
Probably the best fix for this would be to modify the *.x3d export capability in OpenVSP to use the split meshes instead of the singular meshes. I can give you some pointers if you want to try it yourself.
Otherwise, this is extremely low priority and probably won't change.
Rob