Kestrel 19 info wanted.

On 2018/05/29 02:16, wrote:
The brakes on the Kestrel are too far back on the wing to be very effective.
The Slingsby Kestrels had poor sutface accuracy too, thats why the extra 2 meters of wing only improved the LD by one point.
The ultimate ineffective use of span.

If you reprofile the wings accurately and clean things up the glide does
improve. But it is still an old airfoil, so don't expect wonders. I
measured best glide at ~1:45 (after reprofile and adding with winglets.)

Still a wonderful aircraft. Comfortable, good handling predictable and
strong as a a house.

The one piece canopy is a DG200 unit. The complete kit is available from
Striefenedder - but seriously expensive.

As mentioned before - the airbrakes are not the most effective. But the
landing flaps work well, and like any open class glider, energy
management in the pattern is important. With full landing flap, full
airbrakes and the drogue chute out - if you can see it over your toes,
you probably can't reach it.
Too fast and it will float forever.

Jokes aside - the approach is very steep once the drag chute is out, but
I have only ever practiced a couple of times with it. The landing flaps
are enough...

I contacted Striefeneder about this a couple of years ago, they told me they no longer supply this mod.

On Thursday, May 31, 2018 at 1:17:11 AM UTC-6, BruceGreeff wrote:
On 2018/05/29 02:16, wrote:
The brakes on the Kestrel are too far back on the wing to be very effective.
The Slingsby Kestrels had poor sutface accuracy too, thats why the extra 2 meters of wing only improved the LD by one point.
The ultimate ineffective use of span.

If you reprofile the wings accurately and clean things up the glide does
improve. But it is still an old airfoil, so don't expect wonders. I
measured best glide at ~1:45 (after reprofile and adding with winglets.)

Still a wonderful aircraft. Comfortable, good handling predictable and
strong as a a house.

The one piece canopy is a DG200 unit. The complete kit is available from
Striefenedder - but seriously expensive.

As mentioned before - the airbrakes are not the most effective. But the
landing flaps work well, and like any open class glider, energy
management in the pattern is important. With full landing flap, full
airbrakes and the drogue chute out - if you can see it over your toes,
you probably can't reach it.
Too fast and it will float forever.

Jokes aside - the approach is very steep once the drag chute is out, but
I have only ever practiced a couple of times with it. The landing flaps
are enough...

If left out overnight, dew may run down rudder and get the drogue chute wet thus is may freeze solid in before or in flight, depending on the location and season. Sealing it with tape overnight, or removing it and reinstalling before flight will avoid this.

Applies to all gliders with drogue chutes.

Frank Whiteley

Should be better than 45 after reprofiling, my 17m DG200, same airfoil is 45 factory, the 17m kestrel was 43, and the 19m was 44.

On 2018/06/01 09:28, wrote:
Should be better than 45 after reprofiling, my 17m DG200, same airfoil is 45 factory, the 17m kestrel was 43, and the 19m was 44.

Hi Mike

Unfortunately when they built the 19m they did not understand
aerodynamics so well I suspect. So they added a metre of thick draggy
wing at the root, and left the relatively high lift wingtips in place.

So - what you get is lots of extra profile drag. Best I could get off
GPS traces on long final glides in winter when the air is nice and still
- a little under 1:46... Maybe it is that she is 40+years old (1971 was
a LOOONG time ago). Maybe I am pessimistic. With properly profiled
airfoil but without additional mylar seals on the flaps - only internal
seals. I can honestly claim 1:45 is an achievable glide ratio. On a good
day it is maybe 1 better. But I never counted on that. The single piece
canopy may improve the sealing enough to make a difference there - the
amount of noise the canopy generates indicates that it is a source of
significant drag.

Keith modified a T59D by reprofiling the entire wing, and removing the
outboard 1.5m on each side, and reprofiling that part with thinner,
lower incidence airfoil and polyhedral plus a winglet. That got the
owner more like 1:51 - but the cost to do it commercially would be
prohibitive.

Its is my recollection that 1/2 meter was added at the root and the tip.
Airfoils 101, a thicker airfoil has a wider but shallower low drag bucket.