Kestrel DG200 canopy mod.

At 08:39 19 November 2019, wrote:


FYI, Kestrels VNE is 250kts.

Vne for Kestrel is 250 kph, 135 knots. Metrication still causing
confusion...

On Tuesday, November 19, 2019 at 7:30:05 AM UTC-5, James Thomson wrote:
At 08:39 19 November 2019, wrote:


FYI, Kestrels VNE is 250kts.

Vne for Kestrel is 250 kph, 135 knots. Metrication still causing
confusion...

There was a discussion of water ballast vs max weight of non-lifting parts here in 2017:
https://groups.google.com/forum/#!to...ng/MGtLQaWwEtU .
It's well worth the read about wing bending moments.

On Thursday, June 11, 2009 at 2:45:37 AM UTC-4, Bruce wrote:
OK

Anyone out there with experience in converting the T59D / 401 Kestrel
canopy from the awful removable thing with a hoop exactly where you want
to watch the tug, to a single piece.

Apparently there is an approved mod using a DG200 canopy.

Second question is - would there be anyone with such a canopy /frame
assembly for sale. As I understand it you need the entire DG hinge and
pedestal part too.

FWIW - I am considering modifying a Mark 2 Slingsby T59D Kestrel 19m -
though to the best of my knowledge the canopy and cockpit is identical
on the various Kestrels.

Any advice gladly received.

Cheers
Bruce

Further to my earlier comments on desirable mods., I just remembered an important one.
As received new from the factory, 1972, I discovered that despite the vne
of 145 kts ( from memory); at sowewhere around 90 kts, a kick on the pedals would instigate rudder flutter, quite disturbing but killed by pressure
on both pedals.
AS in yugoslavia in 1972 , we never got to fly near Vb, let alone vne,
this was not a concern.
However, when I was repairing this glider 4 years later, I discovered
a reason for this flutter.
Normal composite fuselage construction uses plies at 45 deg to the axis
which yields the maximum torsional stiffness for the laminate.
My fuselage as laid up by the gnomes of Kirbymoorside, had plies running
parallel to the axis, ie 1.4 x less torsionaly less stiff.
(the first rudder flutter mode is torsional)
Moreover, the mass balance on the rudder was at the bottom , the wrong place
for torsional mass balance; it should be near the top.
Nothing I could do about the layup, but moving and adding to the mass
balance near the top of the rudder moved the flutter propensity
above 110kts, unlikely in a proper final glide.
These faults may have been corrected for later serial #s but I suggest
flutter testing in small increments above 85 kts.
John Firth Ottawa.

You seriously need to understand the max weight of the none lifting parts, you can’t use the weight available as water ballast in the wings in your calculations, as being in the wings it does not
increase the bending loads of the spar, and you will be overloading the lift pins on the fuselage. The suggestion to put extra weight in the wings by fitting extra ballast capacity is also a very dangerous concept as you will he increasing the negative g loads which are only half the positive g rating. The max weight is there for a reason.
Otherwise, it’s a good plan. Bringing the profile to accurate form is your best way to improve performance by far, as Slingsby did a very poor job of profile accuracy.

On Tuesday, November 19, 2019 at 4:30:05 AM UTC-8, James Thomson wrote:
At 08:39 19 November 2019, wrote:


FYI, Kestrels VNE is 250kts.

Vne for Kestrel is 250 kph, 135 knots. Metrication still causing
confusion...

Ouch, that would be a typo... Which you correctly caught... VNE is indeed 250kph or 156.55 mph... My point is still valid, a lot of darn bird for the buck... Kestrels walk away from a lot of birds, when soaring in similar conditions.

Few planes are even close to the Kestrels handicap at .88, most costing significantly more--not $20,000, and $30,000 fully restored with an amazing trailer.

A pilot interested in competition has to start ponying up hundreds of thousands to get close or under it. I more than understand I will not be in first place--but also understand I will be six or fifth place... Maybe fourth or third on a great day.

John Firth words say it all...

Proof of the pudding, on a good but not exceptional Ontario day, I passed
the 500KM mark past TP 2 in 4 1/2 hrs. For a 1970s design it was pretty good.

John Firth

There is a glasflugel tech note on the 17m Kestrel about a mod to increase tha max weight of the none lifting parts by 12kg, it involves reinforcing the spar stubs around the pin bushes.
It would be worth looking in to at the weights you are proposing.

http://www.streifly.de/TM401-14.pdf It allows an 11kg increase.

On Tuesday, November 19, 2019 at 12:49:10 PM UTC-8, Charlie Quebec wrote:
There is a glasflugel tech note on the 17m Kestrel about a mod to increase tha max weight of the none lifting parts by 12kg, it involves reinforcing the spar stubs around the pin bushes.
It would be worth looking in to at the weights you are proposing.

http://www.streifly.de/TM401-14.pdf It allows an 11kg increase.

Can you recommend a translation software for this Tech Ref?

The MAUW (Dry) of a Kestrel 19 (Series 1,2,3) is 990 lbs... stated in the POH (Issue 2). Originally, it was 960 lbs dry, but Slingsby issued an update.

In the UK, there is a 3% increase (BGA concession, non-aerobatic) in dry weight to 1020 lbs, so there must be some engineering done somewhere at sometime to allow for that increase.

I would hazard a guess that going beyond those limits makes you a test pilot.

What you really want is a Series 4 Kestrel, which allows for an additional hundred pounds of dry weight!

-John Brake
Kestrel 19 #1789

I have seen an increase in the weight of non lifting parts granted for a decrease in VNE. Proper engineering was done and the mod was approved by GFA. Let's face it, you do not need a VNE of 135 knots in Kestrel.

The UK increase applies to all gliders, with the new limitation of no aerobatics. No engineering done at all.
I’m surprised how many don’t seem to understand the concept of the weight of the none lifting parts, that is what you need to worry about, and that is where the 3% increase was granted..