Re: Re: Aerodynamic obsessiveness

From: Brett D. Sanborn <08bdsanb_at_alma.edu>
Date: Sun, 28 Jan 2007 14:41:50 -0500 (EST)

Nicholas,

I really don't think you're going to gain anything by covering the area in between your wingposts. 1/8" by 3/32" sounds really huge to me. With posts that size I think of anything but streamlined...

I used .031" diameter carbon fiber on my pennyplane wingposts, and I don't think it makes a difference. At USIC last year, Jim Richmond, Tom Sova, Walt VanGorder and myself were all flying within seconds of each other and I doubt it was wingposts that gave the edge; Richmond had the longest ones.

Focus your time on prop and rubber combination.

Brett Sanborn

---- Original message ----
>Date: Sun, 28 Jan 2007 19:25:27 -0000
>From: "Nicholas" <ndhuang83706_at_gmail.com>
>Subject: [Indoor_Construction] Re: Aerodynamic obsessiveness
>To: Indoor_Construction_at_yahoogroups.com
>
> I've already streamlined the posts. They're about
> 1/8*3/32. One
> thing that worries me is the junction between the
> film and the wing.
> I don't have anything to attach the film to at the
> top. I think the
> loose flim might flap around and make things even
> worse. I'm running
> slightly low on time to do exhaustive testing, but
> we'll see what
> comes out.
> Nicholas
>
> --- In Indoor_Construction_at_yahoogroups.com, dgbj@...
> wrote:
> >
> > I wondered whether at this very low aerodynamic
> scale there are any
> vortices
> > behind the wing posts.
> >
> > According to Van Dyke, "An Album of Fluid Motion",
> Figure 46 on
> page 30, the
> > flow pattern transitions from steady to
> oscillating at around R =
> 41.0. A
> > 1/16" wing post at 2 feet per second has a
> Reynolds number of about 65.
> >
> > Putting film between the wing posts might create
> more friction drag
> than it
> > eliminates. You would presumably still have a wake
> behind the rear
> post.
> > Might it be better to streamline the posts?
> >
> > The obvious way to get an answer is to try it.
> Replace the prop
> with an
> > equivalent weight of clay and glide test.
> >
>
>
Received on Sun Jan 28 2007 - 11:41:56 CET