Belly board holes or no holes;

I have considered making a belly board with holes and one without holes. 
Attaching one at a time to a board where I can attach a scale. ?I would then 
attach the system to the roof of my truck that I would drive down an unused 
road. I would measure the air resistance at varying speeds.?

Do you believe that this would accurately correlate to flight?

Joe?




Sent from my Verizon Wireless 4G LTE smartphone

<div>-------- Original message --------</div><div>From: Dan Branstrom via KRnet 
<krnet at list.krnet.org> </div><div>Date:12/30/2014  12:34 PM  (GMT-06:00) 
</div><div>To: krnet at list.krnet.org </div><div>Subject: Re: KR> Belly board 
</div><div>
</div>
Herbert wrote, "......my bellyboard turns down to about 80 deg. and 
after talking to some aerodynamicists and some practical trials I 
decided to let the board without holes. The tests I made are very 
simple.I took a foamsheet ( 1 meter x 1 meter x 5 mm) ,fixed 5 strings 
to the edges and the center with a weight (about 100 grams ) and used my 
"parachute" as testdummy. I dropped the dummy from my ten meter high 
rooftop (5 trials without holes and 5 trials with holes) and compared 
the times I measured. It was easy to recognice that the board without 
holes always gone down slower ! There was a big difference how they sank 
down.The board without holes tumbled much more than the Board with the 
holes (due to the holes,of course) Happy New Year again,Herbert, German 
Kr Bilder Von meinem"

The board without holes fell slower in your test.  The problem is that 
at the speeds a belly brake is deployed, the holes in the belly board 
may generate vortices or turbulence, and hence, parasitic drag, that is 
more of a factor at the 100+ kph (62 mph+) that a belly brake is 
deployed.  Note that the people who have flown both with and without 
holes report more drag with the holes.  I would also think that there 
might be different interactions between the belly board and fuselage or 
tail when there are holes in it that contribute to the difference.  
That's why flight testing is so important, with the real world conditions.

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