Flaperons

Wayne Paul wrote:

..... For example, a Schreder HP-14's
40:1 glide ratio is decreased to 2:1 when the flaps are lowered to 90
degrees.

Wow! That's an amazing change.

...This gives an approach angle of 30 degrees which requires the nose
to be 45 degrees below the horizon.

I think you've got this a little backwards - if the approach angle is 30
degrees, the nose can't be BELOW that - you'd have a negative angle of
attack. I think that the nose would be somewhere in the 20 degree down
range, to provide a positive AOA of somewhere around 10 degrees. 20
degrees nose down is VERY down, however - it would certainly LOOK like
you're pointing straight down.....

--
Marc J. Zeitlin
http://marc.zeitlin.home.comcast.net/
http://www.cozybuilders.org/
Copyright (c) 2004

"Marc J. Zeitlin" wrote in message
news:PiPld.610968$8_6.562540@attbi_s04...
Wayne Paul wrote:

..... For example, a Schreder HP-14's
40:1 glide ratio is decreased to 2:1 when the flaps are lowered to 90
degrees.

Wow! That's an amazing change.

...This gives an approach angle of 30 degrees which requires the nose
to be 45 degrees below the horizon.

I think you've got this a little backwards - if the approach angle is 30
degrees, the nose can't be BELOW that - you'd have a negative angle of
attack. I think that the nose would be somewhere in the 20 degree down
range, to provide a positive AOA of somewhere around 10 degrees. 20
degrees nose down is VERY down, however - it would certainly LOOK like
you're pointing straight down.....


The stall speed of a HP-14 with a 90 degree flap setting is only 30 mph.
The approach is flown at 55 mph (the best L/D speed with 0 degree flap
setting) to provide the ability to take of a little flap while raising the
nose if you are tracking short of the desired touch down point. Lowering
the flaps changes the effective angle of incidence of the wing with
relationship to the fuselage. In the case of the HP-14 this is about 15
degrees.

The attitude of the HP-14 sitting on the runway is the approximate attitude
at which it stalls with a 90 degree flap setting. As you fly the approach
at 55 with full flap you look landing aim point is well above the nose of
the glider. In fact it is almost up to the canopy bow.

(Pictures of HP-14 large span flaps:
http://www.soaridaho.com/Schreder/HP...41/N8041_1.jpg more links
http://www.soaridaho.com/Schreder/HP...-14_Links.html)

Respectfully,
Wayne
http://www.soaridaho.com/Schreder

In article PiPld.610968$8_6.562540@attbi_s04,
"Marc J. Zeitlin" wrote:

Wayne Paul wrote:

..... For example, a Schreder HP-14's
40:1 glide ratio is decreased to 2:1 when the flaps are lowered to 90
degrees.

Wow! That's an amazing change.

...This gives an approach angle of 30 degrees which requires the nose
to be 45 degrees below the horizon.

I think you've got this a little backwards - if the approach angle is 30
degrees, the nose can't be BELOW that - you'd have a negative angle of
attack. I think that the nose would be somewhere in the 20 degree down
range, to provide a positive AOA of somewhere around 10 degrees. 20
degrees nose down is VERY down, however - it would certainly LOOK like
you're pointing straight down.....

You're forgetting the effect of lowering the flaps on the actual as
opposed to nominal AOA of the wings.

Ask yourself how much you'd have to lower the nose after lowering the
flaps in order to (for instance) stay at the zero lift AOA relative to
the fuselage...

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."