Hi Ren,
Since your daughter is working on this for her science fair project it may
be worth looking at happens as you vary camber in xfoil.
http://web.mit.edu/drela/Public/web/xfoil/
Pay careful attention to what happens to lift and drag as the camber
percentage changes.
If you have an iPad handy Wind Tunnel Pro will do similar calculations in a
an easier to use manner.
Regards,
Nick
On Wed, Oct 30, 2013 at 9:19 AM, <nmonllor_at_tampabay.rr.com> wrote:
> **
>
>
> Hello everyone,
>
>
>
> I've come across many plans where two differnt percentages of arc have
> been presented for different cieling heights. An example of this would be
> in Ron Williams' book Dennis Jaeck's Pennyplane #2 on page 91. There have
> been others too.
>
>
>
> On this particular model plan it states:
>
> high cieling: 4% arc
>
> low cieling: 6% arc
>
>
>
> The first time I saw this, I figured it had to do something with lift,
> Bernoulli's law and so on. At the time, I didn't give it much thought as I
> just wanted to build a plane that flew. Since then though, I've come across
> it again and again on other plans and thought I'd take a look at why this
> was so.
>
>
>
> Well, my daughter Gabby is doing her science fair project on how differnt
> arc radius airfoils affect the flight of her Pennyplane. BAM, right between
> my eyes!!! The question arises again, but this time with a purpose.
>
>
>
> I thought it had to do with lift but, does it?
>
>
>
> A smaller percentage would create a higher hump in the air foil increasing
> lift according to Bernulli, but yet it is suggested for a lower cieling.
> Whyis this?
>
> What am I not seeing?
>
>
>
> Please help me understand.
>
>
>
> Thank you,
>
>
>
> Ren
>
>
>
Received on Wed Oct 30 2013 - 06:30:22 CET