Chris,
You must be the person Ann at Van's was talking about.   Ann mentioned to me that someone had a Sam James cowl and the spinner was to small,  I wast ordering my finish kit less the cowl at the time.  I have a Sam James cowl that I got from Bernie Kerr.    I told her that I would get back with her about the spinner.  I immediately went to my storage building and measured the face of the cowl,  it was 13".  The only difference that I see is that you have the cowl that has the one large cooling opening at the bottom.  The cowl I have has two cooling inlets like the vans cowl.  I wonder why the .75" Difference in the cowl face?

Bob Perkinson

-------------- Original message from Charlie England <ceengland@bellsouth.net>: --------------


> Al Gietzen wrote:
> >
> > I have the James rotary cowl--front “face” has a 13.75” diameter. I
> > also have the Vans 13” spinner that is already cut to fit my CATTO
> > prop. This leaves about a 3/8 lip of cowl showing all the way around
> > the spinner. Take a look at the picture.
> >
> > I know any amount of lip will cause drag, but is this enough to
> > warrant a new spinner? UHS makes a 14” one that would probably do the
> > trick.
> >
> > Chris
> >
> > My opinion is that is more a matter of appearance than function. The
> > air flow at that point is very turbulent, and any resultant drag would
> > be less than measurable.
> >
> > BTW; on the post about the fuel pressure sensor I thought you were the
> > other Chris with the Velocity.
> >
> > Al G
> >
>
> I can't even spell aerodynamicist (& neither can my spell checker), but
> everything I've read says that it's better to have the cowl face bigger
> than the spinner bigger. My impression is that the air will speed up
> slightly but not be greatly disturbed as it continues around the cowl,
> but if the spinner is bigger it will cause really bad turbulence as the
> air tries to turn the corner at the edge of the spinner to fill that gap.
>
> Will James assured me that the stock Van's spinner fits his cowl, so I'm
> going with his assurance.
>
> FWIW,
>
> Charlie
>
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