Kestrel DG200 canopy mod.

[Bruce]

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

[Frank Whiteley]

You might check in also at the kestrel401 yahoo group.

Frank Whiteley

[Tim Mara]

Not too long ago there were pictures of a Kestrel 17 on Hansjorg Streifeneders web pages with a single piece forward hinged canopy modifcation ....this glider was being offered for sale but I think the ad said "Streifeneder" modification to canopy.

noted on their website: http://www.streifly.de/segelflugzeug-service-e.htm

You have some fancy ideas for modifying your aircraft? Please tell us. Actually there is not much we are not able to put into practice. Some of our works were: ·

• a continous long canopy for Kestrel ·
• an elongated front canopy for ASH 25 ·
• a long one-piece canopy for ASH 25 ·
• an elongated forward hinged canopy for Discus ·
• seat cushion and sidewall panels in genuine leather, seat heating ·
• and much more...

try asking him, his website is  http://www.streifly.de/home-e.htm

tim

Please visit the Wings & Wheels website at www.wingsandwheels.com

 

"Bruce" <br...@wird.co.za> wrote in message news:h0q96q$nse$1...@adenine.netfront.net...

[JS]

Whilst you're waiting for the fix from Streifeneder, try different
flap settings on tow.
Jim

[Bruce]

Now there's a lateral suggestion.

I shall take your suggestion and try it - but I still want the new canopy.

Bruce

[Jonathon May]

In England Don Austin has put a one-piece canopy on a kestrel,it looks like
a next generation ship,he dosen't know when to stop though, he also put
suspension,a disc brake and wing tips.

[Bruce]

Sounds perfectly reasonable to me. Winglets, disk brake and a single
pece cockpit - a little wing profiling and you have a very nice
sailplane for a fraction of the cost of one (15m) with maybe 3% better
performance... A new 18m ship would cost me five times the investment
for maybe 10% more L/D. If you just want to have fun then it is a poor
investment.

The locally developed modification with polyhedral wingtips and winglets
seems to narrow that performance gap even further. So that is a probable
change when time and money allow.

Mine has already had a complete cosmetic going over and wing profile -
needs some work to pretty the cockpit up and then she is as good as new.

Lovely glider as she is - But that canopy has to go.

[jsbrake]

But wouldn't putting winglets on the bird invalidate the Type
Certicate?

I've been toying with the idea of the double-panel spoiler
modification, but I've been told that my TC would be gone and I'd be
in the "owner maintenance" category. I'm not sure that that's a good
idea.

I can understand upgrading the brakes and canopy not interfering with
the TC, but wouldn't the winglets be a structural change, and thereby
invalidate the TC?

As an aside, my TC states that my Kestrel must be "all white", with
blue-grey (or similar light) registration marks. I understand that it
was written in the early days of FRP, but would it be allowable now to
put bright red anti-collision accents on the extremities?

[Bruce]

Well it all depends on where you live.

In South Africa gliders are maintained much as the BGA did before the
EASA onslaught. So we are - by definition - in owner maintenance world.
No type certificates are significant, except for first registration of a
type in the country.

The winglets are manufactured and tested by a qualified aero engineering
business. Any structural modification like this is subject to a pretty
rigorous approval process, then it is up to owners to decide if they
want them. As long as the change is performed and approved by a suitably
qualified person and signed off in the log book there is no difference
to flying a factory standard ship. Except that you can embarrass some
newer glass. It does make it harder to sell to places that do rely on
type certificates.

[ZZ]

Bruce

I'm almost certain that I have seen at least one 17 meter Kestrel with
an aft hinged canopy. I don't know if this was a factory (Glasflugel)
canopy or an owner modification. Perhaps this could be adapted to
accommodate the 19 meter canopy as well.

Paul
ZZ

[Donald Austin]

>As to the mods done on my Kestrel 19 I have fitted a Vega Canopy to it as
I watched the Vega Mould being made and they used an uncut Kestrel Canopy
for the front of the Vega.
I liked the simple hinging arrangement used by DG so I used this method.
The winglets I fitted were on the style of Shemp Hirth and measurably
improve the roll rate and I believe improves the best glide angle.
The BGA permitted the fitting ofwnglets to any gider that can have its
wings extended. ie 20 Meter Kestrel.I have also fitted two ASW 20's
with winglets.The easy way to do this is to modify the stub tips.
Kestrels are too heavy for a drum brake but a M/Cycle front disk brake can
be obtained complete with Brake Lever pipe and reservoir quite easilly.The
standard Glider wheel with disk is the one I used.
It seemed a shame not to fit Rubber springs to the U/C when it was
reassembled so I did.
Anyone who would like a picture is welcome.
Don Austin

[Donald Austin]

At 09:22 12 June 2009, Bruce wrote:

[fred....@gmail.com]

Don:

I would like a photo and the specifications of the M/C disc brake you used. I have just purchased a Kestrel and would like to make this modification.

Fred.lasor AT gmail.com

[Don Johnstone]

Take care with the flap setting, the limit speeds for positive flap are
very restrictive but one stage of positive does allow you to see the tug.

[Don Johnstone]

There is an official double paddle mod for the airbrakes, it was held on
Gliderpilot.net for a long while. It is a very simple mod.

[Ian Kennedy]

"Don Johnstone" wrote in message
news:4fb2fc13$0$2899$a826...@newsreader.readnews.com...

Mod is on the Kestrel Yahoo group.
The word is that all it does is change the noise.
Landing flap and good speed control is all that's needed.
( Unless you are out to impress, when the use of the tail chute looks
coooool )

[juerge...@gmail.com]

> Kestrels are too heavy for a drum brake but a M/Cycle front disk brake can
> be obtained complete with Brake Lever pipe and reservoir quite easilly.The
> standard Glider wheel with disk is the one I used.
> It seemed a shame not to fit Rubber springs to the U/C when it was
> reassembled so I did.
> Anyone who would like a picture is welcome.
> Don Austin

Hi Don,
I would very much appreciate to receive pictures and specs for the wheel brake and U/C mods you made.
My Glasfügel 17m Kestrel (118) has its wheel brake lever under the stick. Is it the same wit the T59D´s? Did you mod that actuating element, too?
Greetings from Germany
Jürgen

[highte...@gmail.com]

My name is Stephen, and recently purchased a Kestrel T59D in great shape. The Kestrel's handicap (Kestrel .89 versus Discuss .93) being in the neighborhood of more expensive ($250,000) aircraft--seems like a pretty good bet to put money into the old girl--albeit a 50 year old glass ship.

The bird is in amazing shape, yet needs some love in certain areas.

Being nearly seven feet tall as a pilot... options are to cut a hole in the bottom of the aircraft--which negates need for new brakes. Of course, I could opt for one of those new-fangled, sexy looking single canopies with a six inch larger bubble. Yeah, yeah, that is the ticket... Look cooler, go faster, and receive small increase in performance. Mmmmm... That is probably the better choice.

My hit list is simple...

1) Trailer gets new Timbren Axle-less axles. A two tone paint job--gray lower, white upper--with red seperation stripe and alloy designer rims. Electric brake upgrade, with new radial tires.

Inside will be painted, scabs and wounds from years of use fiberglassed over, and mounting hardware updated.

(About $3000 of love to make a 36 foot long viable and attractive for competition.)

2) Canopy modification... Going to reproduce Don Austins work for canopy. Would love to find that guy and actually ship my aircraft to him for design changes and review. The canopy is the biggest potential loss of L/D on the Kestrel--with any leak of air pressure devastating the laminar flow around the nose to wing section.

(Planning on $4000 of love, could go up to $6000 depending on cost of DG frame and hinge costs)

3) Wingtips... Have research done on benefits and size required. Again, mimicking Don Austins work in England, with small tweaks because of research values found to be optimal. Really curious as to the reality of theoretic values vs real world application of that theory in Don Austins bird--he loves the darn thing, so it must be exceptional.

(Planning on $6000 to $8000 of love on winglets. Improving L/D by 4--making former 44:1 closer to 48:1 with windshield mods, turbulators, and wingtips.)

4) Brakes and suspension... Improved brakes... Why improve brakes on a plane that is known to spin on the ground if you manage to fly it in hot? Because, the standard brakes are just too damn ineffective. Good speed control is important in any plane--add sixty five feet of wingspan and you have a wild bronking buck on your hands. The damned thing is designed to fly, and it wants to. The suspension will absorb the more aggressive landings, instead of my rumpus--connected--to--me (medical term, yeah.)

Again, stealing as much as Don Austin will let me from his experiences... Thinking maybe I should let him do all the work. If only I could find him. Plus the cost and hassle of shipping the bird... Really looking for a talented shop in the United States that is adventurous and not outrageous in price tag.

I will be the first to admit, I will have $30,000 into my sailplane... It will however run circles around others at competition, with the competitors spending $300,000 to arrive at the same place my $30,000 took.

Finish lines never lie...

Anyone know Donald Austin? Tell him I am going to need his help to compete in the 2020 year.

Personal Best to all you dedicated fliers out there,

Stephen

[Charlie Quebec]

The first thing you need to do if you want a 19m go well is check the profile accuracy, Slingsby never managed to get it as good as the Germans. That’s why the 10 gained only one L/D point after adding 2 meters. Striefeneder used to do the canopy mod, but when I asked them said it was too expensive to be worthwhile, I’ve got a photo somewhere of one that was done, and it looks great. It won’t give you any better performance though.
In the UK several have been legally modified to 20M span. A slingsby Vega canopy fits exactly, as the front was from the Kestrel. Just a canopy frame and bubble without labour will be well more than you have budgeted.

[Jonathon May]

At 21:29 15 November 2019, Charlie Quebec wrote:
>The first thing you need to do if you want a 19m go well is check
the

>profi=

>le accuracy, Slingsby never managed to get it as good as the

Germans. That=
>=E2=80=99s why the 10 gained only one L/D point after adding 2
meters.
>Stri=

>efeneder used to do the canopy mod, but when I asked them said it
was too

>e=
>xpensive to be worthwhile, I=E2=80=99ve got a photo somewhere
of one that
>w=
>as done, and it looks great. It won=E2=80=99t give you any better
>performan=

>ce though.
>In the UK several have been legally modified to 20M span. A
slingsby Vega

>c=

>anopy fits exactly, as the front was from the Kestrel. Just a canopy
frame

>=

>and bubble without labour will be well more than you have
budgeted.
>

Don is starting to show his 80+years,I have not seen him at the
gliding club this year.

[highte...@gmail.com]

On Friday, November 15, 2019 at 1:29:43 PM UTC-8, Charlie Quebec wrote:
> The first thing you need to do if you want a 19m go well is check the profile accuracy, Slingsby never managed to get it as good as the Germans. That’s why the 10 gained only one L/D point after adding 2 meters. Striefeneder used to do the canopy mod, but when I asked them said it was too expensive to be worthwhile, I’ve got a photo somewhere of one that was done, and it looks great. It won’t give you any better performance though.
> In the UK several have been legally modified to 20M span. A slingsby Vega canopy fits exactly, as the front was from the Kestrel. Just a canopy frame and bubble without labour will be well more than you have budgeted.

I am having the fairing looked at, agreeing with you wholeheartedly. I am trying to put off doing paint and fiberglass work as long as I can--with the fiberglass being one of the birds better features.

Did people find the 20M mod worth the effort and expense??? I know lugging around 19M wings at close to 120 pounds a piece is going to get old.

Please do tell me more about where I can get a Vega Canopy--wanting to add six inches to the bubble, so I fit, being close to seven feet tall and 279 pounds. If I can get the attaching hardware--I will blow the bubble myself--so I was discounting the price, doing what I have skills to do.

Biggest thing for me, since I am updating the canopy anyway is to make egress and entry much more easy.

Thinking winglets offer the longer wing aspects, with many desirable traits having them. At 20M of wing, not sure there is much advantage left for winglets.

[highte...@gmail.com]

Don is legendary, even stateside.

Because of him, I am endeavoring to make a Kestrel T59D fit a 279 pound, nearly seven foot tall pilot. Bought the plane and cannot even fly it until I get some mods done.

Have to make a 6 inch taller canopy. Have to move my body back two inches into the wing root--trading off my body weight as the wings water ballast.

I will be a rocket in the skies. Even the trailer will look amazing when I am done. I have a reasonable, yet serious budget to finish this airplane--I am so big in size, have had to plan this for years. If it was not for Bob, probably would not have ever entertained this large and risky of a project.

Figuring I am only a test pilot for the first fifteen minutes-then if all things work, I get to find out how well.

If anyone runs into Don, send him prayers from Stateside. The man has gone where very few venture, and I would like to recreate some of his work--only with my new data.

I think I can reach 48:1 with that aircraft.

Stephen G. Elder
Chief Operation Officer
Precision Innovation
Black Ops Division
(951) 515-6029

[Charlie Quebec]

You will be 16kg + parachute over the maximum pilot weight 110kg, ( this is also the limit for the harness as standard) and out of the CG range without adding tail ballast, and worst of all, after that, significantly over the max weight of the none lifting parts. The Canopies are not blown, as they get too thin as they stretch, they are formed by forcing a plug upwards into the hot plastic.
Not trying to rain on you parade, but you should know this.

[Tango Whisky]

With all these modifications, he will probably push best L/D from 44 to 44.5, plus he will be a test pilot for the reasons you cite.

And after the first contest he will have learned that it's not max L/D which matters, but L/D's at 90 ot 130 kts. At these speeds, a Kestrel basically falls out of the sky, regardless of any lipstick. Especially if the span has been increased.

My advice would be to sell this ship, and get one he'll fit in without making changes. ASW20 would be a good start, or Open Cirrus. Both are less, or significantly less, than 30k.

[arche...@gmail.com]

Having owned a 401, and I loved it, I regrettably agree with Tango Whiskey, other than the selling part :). I'd look for ways to improve the L/D at the higher speeds. Adding tips doesn't change the wing thickness near the root and you have to push that through the air at the higher speeds, so I'm guessing with the wing extension the polars will still converge to something VERY similar at 80 kts or more.
Now for the great news. It's a fantastic glider with very pleasant handling that by it's nature teaches good flying habits. Go take it for a few x/c flights and then decide what you want to do with it. Turns out it's pretty well engineered for what it is. Yes, the airbrakes are somewhat ineffective but it has flaps/landing flaps and the descent rate is more than adequate. As a result, it lands pretty slow making the wheel brake sufficient if working properly. Get the drogue chute working and practice that if you really want to make a super short landing. Mine had one and I never did, though I do regret not doing it once at least.
A single, connected canopy would be a fantastic upgrade if done right and would eliminate the gliders weakest feature, where do you put the canopy while rigging on a windy day...
As to flying it, I focused on maximizing what the glider could do well, mostly by trying to minimize the time circling. Spend $60 and buy SeeYou and look at circling percentage for each flight. Select your thermals wisely and perfect thermal entry. Fly into cloudstreets or any lift lines at the lowest altitude that makes sense, and out the end high and fast. Enjoy the pleasant handling all the way, it's a fun glider to fly and a fantastic value.

[Martin Gregorie]

On Sun, 17 Nov 2019 09:05:52 -0800, archerzulu wrote:

> Spend $60 and buy
> SeeYou and look at circling percentage for each flight. Select your
> thermals wisely and perfect thermal entry. Fly into cloudstreets or any
> lift lines at the lowest altitude that makes sense, and out the end high
> and fast. Enjoy the pleasant handling all the way, it's a fun glider to
> fly and a fantastic value.

I agree with all the advice given about flight analysis, but would add
that, if you're happy with installing applications written in Perl, i.e.
yo have to install the Perl runtime first, then using GPLIGC is a
reasonable alternative. It can convert a flight log into a KML file that
can be displayed with Google Earth. GPLIGC can be downloaded from:

https://sourceforge.net/projects/gpligc/




--
Martin | martin at
Gregorie | gregorie dot org

[john firth]

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

As usual ,I agree with Martin; I owned a K19 ( a 1972 model)for ten years and only sold it because I wanted to go 15M class.
It will indeed land very short if needed; landing flap, 45 kts and tailchute
as you flair will get you down inside 100M.
However, as supplied by Slingsby, there were a few things I wanted to change.
The cusp on the elevator added to provide "feel" at higher speeds made it
impossible to trim over 80 kts; cut it off to K17 elevator size;
anyway, I hated the trim system on the stick and locked it out except
for long glides.
The coupling of wheel brake to air brakes meant you had neither full
and ineffective airbrakes nor adequate wheel brake. Added separate brake lever.
The factory ballast bags held far too little (120 lb ??)
Made my own vinyl bags holding 250lb but the dump was too slow and wetted
the brake drum. Added a down tube ( also a filler tube) to the gear doors.
I reckoned that the max AUW was predicated on a rough field take-off
so not a problem from a smooth grass field.
For a chance at 750 km in Ontario I needed the weight ( add 50lbs inn the O2
tank holder) for cruise at 80-90 kts, and as Moffatt observed for the Nimbus 2
the higher wing loading makes it a different glider.
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
an old no longer bold pilot.
PS never checked the profile accuracy but filled in the over spar dip.

[highte...@gmail.com]

On Friday, November 15, 2019 at 8:39:50 PM UTC-8, Charlie Quebec wrote:
> You will be 16kg + parachute over the maximum pilot weight 110kg, ( this is also the limit for the harness as standard) and out of the CG range without adding tail ballast, and worst of all, after that, significantly over the max weight of the none lifting parts. The Canopies are not blown, as they get too thin as they stretch, they are formed by forcing a plug upwards into the hot plastic.
> Not trying to rain on you parade, but you should know this.

You are not raining on my parade...

By no means, I welcome all thoughts.

As to CG, I am moving my body weight farther back into the wing by two inches--where water ballast normally would be. All calcs and work will be done professionally--with wife not accepting self as a test pilot. That dog don't hunt.

The sailplane I own has a empty gross weight of 330kg, and fully loaded gross weight of 472kg. That leaves 15.42kg for gear, that I may or may not add at a future date. The rest of the gross weight is my Canary Ass at 125.552Kg at Seven foot, two inches tall...

Short guys are the lucky ones when it comes to gliders. Strap on and go, I have always flown customized gliders--with last being a Pilatus B4. My heart was broken when the club let that bird go--too much bird that fit too few people in the club. Our soaring club formerly was mostly novice flyers--outside of perhaps ten of us old goats.

Back to the Kestrel...

Even added roughly 4kg as a penalty of a serious harness upgrade. The mounts also had to be backed with aluminum load distribution plates. The nice folks from a tandem parachute company helped me obtain the 500Kg five point harness I am yet to purchase in fire engine red, royal blue, charcoal, or grey. If people can hang safely from the harness with a second person attached for two years--seems reasonable it can keep me from bouncing in a seat for ten years.

Agreed on making a plug for the windshield--and thermoforming, sometimes writing faster than I think and edit. Basic plan is to make a carbon fiber turtle deck--saving kg's, a carbon fiber windshield enclosure--saving more kg's offsetting the weight of the comfortable six inch rise in new window. As the housing that extends to the front of the glider--it will be more efficient in not dumping precious laminar flow.

I am not looking to gain more L/D--just get published values. People do not realize that L/D is illusive and not many people truly attain all their bird has to offer. Seals, air leaks, anything destroys laminar flow--I am not being a test pilot--I am just conscientiously eliminating wasted L/D.

[highte...@gmail.com]

Have you really looked at the Kestrel performance? Friend, the handicap is currently set at .88... Quarter million dollar ships in same class beat out the Kestrel by fractions (New Discuss .85)... The Kestrel is quite comfortable running at 150kts and walks away from most planes.

FYI, Kestrels VNE is 250kts..

The biggest problem I have is being 279 pounds, and seven foot tall... Any bird I look at will take modifications.

I am not being crazy with mods, just making sure the plane performs to published L/D. If you did read above--all things are being professionally done to the aircraft, including calcs... If I show up on the National scene with a 50 year old glass ship--lots of folks are going to have egg on their face.

I do believe you have underestimated this fine old aircraft. All fixits to the plane are capped at thirty, and the trailer needs six, and cost me 17 to purchase.

Have a little faith in a fellow poor guy, I will make you proud this coming year. This 50 year old bird may not come in first, but she sure will be respectable in national standings. I just cannot afford a quarter of a million dollars and will be happy to place third, fourth, or fifth...

[highte...@gmail.com]

I agree with everything you have said.

I am changing the plane to fit a 279 pound body, with seven foot tall frame.

The changes being made are to reduce drag, and hopefully arrive at published numbers with my body weight. I want to compete this next year, and have never had a plane capable of doing so till this year.

I bought the plane and have not been able to sit in it yet. Come January, I will have my first tow in her. New harnesses, new CG position for my body, two inches back of current max pilot position, less rear ballast, new upholstery, a six inch taller canopy, longer rudder pedals, more clearance at the knees for my legs to fit in, new radios.

All in all... Read the bits I wrote above, being pretty responsible in what I am doing to this plane. Plus, when I am done and can afford something sleeker--the plane will easily fetch three times a standard Kestrel.

All modern conveniences, professionally designed and built for a heavy and very tall pilot, trailer redone to perfection in three colors... Grey bottom half, 2 inch Red Stripe, White top, and supporting latticed iron in gloss black, with aluminum mag wheels... All of the above, lifted by Timbren Axle-less Axles, and electric brakes.

I will have built a ten year dream machine for 30 grand, with a handicap of .88...

Color me dumb, sounds pretty reasonable to me... Don Austin went crazy on his Kestrel and loved it for years--he is my inspiration on this labor of love.

[James Thomson]

At 08:39 19 November 2019, highte...@gmail.com wrote:

>
>FYI, Kestrels VNE is 250kts.
>
Vne for Kestrel is 250 kph, 135 knots. Metrication still causing
confusion...

[Dan Daly]

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

[john firth]

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.

[Charlie Quebec]

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.

[highte...@gmail.com]

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...

[Charlie Quebec]

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.

[highte...@gmail.com]

Can you recommend a translation software for this Tech Ref?

[C-FFKQ (42)]

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

[Paul B]

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.

[Charlie Quebec]

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..